Navy Uses Railgun To Launch Fighter Jet

Phoghat writes "In 2015 the aircraft carrier USS Gerald R. Ford will take to the seas and the plan is to use a railgun to launch planes, instead of steam powered catapults. From the article: 'The Navy developed its Electromagnetic Aircraft Launch System as a replacement for the steam catapults currently used on aircraft carriers. The EMALS is a linear induction motor that's capable of accelerating a 100,000 pound aircraft to 240 miles per hour in the space of 300 feet. Compared to a steam catapult, the railgun catapult is much smaller, more efficient, simpler to maintain, gentler on airframes, and can deliver up to 30% more power. It's also capable of being cranked down a whole bunch, meaning that it can also launch smaller (and more fragile) unmanned drones.'"

Comments

A linear induction motor is not a railgun.

[John Hasler]

n/t

Re:A linear induction motor is not a railgun.

[icebike]

Same accelerator concept though. Maybe what they have built is flexible enough to handle both roles.

Linear induction motor that's capable of accelerating a 100,000 pound aircraft to 240 miles per hour in the space of 300 feet.

One wonders how is that any easier on the airframe?

Anyone know how you calculate G-forces in this kind of acceleration?

Re:A linear induction motor is not a railgun.

[blackraven14250]

I would guess it's easier on the airframe because it can have a different acceleration curve. I imagine a steam driven catapult as having high power at the onset, but lower power at the end, while an electronic method like this can have a more gradual push.

Re:A linear induction motor is not a railgun.

[Pharmboy]

I also wonder if it is simply a smoother curve, with less bumps and jarring. This would seem to be much better for a controlled acceleration, not just at G force or final speed, but for the entire range in between. With steam, it would seem they just pushing it at full throttle for the whole distance.

Re:A linear induction motor is not a railgun.

[Antimatter Beam Core]

Same accelerator concept though. Maybe what they have built is flexible enough to handle both roles.

No it isn't.
A rail gun uses two charged rails and a conductive projectile. The projectile is introduced between the rails, strikes an arc, and and is propelled down the barrel by Lorentz force.
A linear induction motor, on the other hand, uses coils to produce magnetic fields which propel the projectile.
Rail guns require maintenance to their rails every few shots, or they will become too eroded to use. Plus, they need another type of gun to start the projectile moving, or you just weld the projectile to the rails. All these factors make a linear induction motor a much better choice for aircraft launch.

Linear induction motor that's capable of accelerating a 100,000 pound aircraft to 240 miles per hour in the space of 300 feet.

One wonders how is that any easier on the airframe?

Anyone know how you calculate G-forces in this kind of acceleration?

The Nimitz class aircraft carriers' steam catapults already do the same thing.

Re:A linear induction motor is not a railgun.

[0100010001010011]

Jerk is probably what you should look at, not acceleration.

Re:A linear induction motor is not a railgun.

[krygny]

... Anyone know how you calculate G-forces in this kind of acceleration?

No details provided but I'd assume you can vary the current with a high degree of [computer] control. Increasing the inertia gradually, rather than an instantaneous kinetic release of steam.

Re:A linear induction motor is not a railgun.

[Hognoxious]

Yeah, I was wondering what advantages this has over steam. Maybe it's easier to route cables than pipes? On the other hand, you're already producing steam for the engines and steam pipes don't short when they get wet.

Re:A linear induction motor is not a railgun.

[GloomE]

v = 400km/h = 111m/s
s = 100m

v^2 = 2as

a = v^2/2s

a = 12321/200

a = 61m/s^2

g = 9.8m/s^2

a = 6.3g

Re:A linear induction motor is not a railgun.

[wiredlogic]

They are switching to the linear motors for the reliability. Steam catapults need extensive maintenance on a regular basis which cuts down on the available capacity to launch planes

Re:A linear induction motor is not a railgun.

[noidentity]

In other words, constant acceleration, so that there are the same G-forces on the airframe during the entire run, rather than more at the beginning than end.

Re:A linear induction motor is not a railgun.

[Anonymous Coward]

Same accelerator concept though.

No, it is not. It is far more similar in concept to a mass driver.

A railgun consists of two parallel, electrically conductive rails, each connected to one terminal of a charge storage device (usually a capacitor, but if you've got something better, go with it). The charge storage device is charged to full power, and then a conductive projectile is placed across the rails, completing a circuit.

The completed circuit resembles a large inductor, in that it is a large conductive loop with current flowing through it, whose inductance is proportional to the area enclosed by the loop. The magnetic field generates a force upon all the components of the railgun, but since the projectile is the only part not rigidly fixed, it is moved by the force. The force acts to increase the size of the inductive loop, driving the projectile away.

The key component to note here is that the projectile needs to be conductive, not ferromagnetic, and the rails must be exposed in order to pass current. This limits military applications because the presence of dirt in the rails could break the circuit, causing an electric arc flash, causing the system to act more like an arc welder. Also, the rails wear out due to the heating caused by the lack of superconductivity.

Read the Wikipedia articles for Railgun and Mass Driver more details.

Re:A linear induction motor is not a railgun.

[noidentity]

The electromagnets use insulated wire where it matters. Anywhere there isn't insulation, a little water would vaporize if it were conducting any significant portion of the energy running through the couls.

Re:A linear induction motor is not a railgun.

[Wyatt Earp]

3.3g or so for a loaded F-18C

https://pumas.gsfc.nasa.gov/files/03_23_02_1.pdf

Re:A linear induction motor is not a railgun.

[fuzzyfuzzyfungus]

While the question could have been phrased better, it isn't as simple as you make it out to be.

You know that the starting velocity is zeroish(maybe a little bit of taxiing; but negligible) and that the end velocity is 240mph; this makes calculating average acceleration over those 300 feet trivial; but it doesn't much help you in determing the actual shape of the acceleration/time graph.

It is quite possible, for instance, that an electrical system has a nearly perfectly constant acceleration, while getting the same out of a steam driven system(whose volume is presumably changing continuously) would be some fairly tricky plumbing.

From an airframe maintenance perspective, I assume that it is the sharp spikes of peak acceleration that cause the most trouble, and those are what a system capable of neatly constant acceleration could avoid...

Re:A linear induction motor is not a railgun.

[Anonymous Coward]

Anyone know how you calculate G-forces in this kind of acceleration?

First you metricise: 240 m/h ~= 107 m/s , 300 feet ~= 91 m. First assume Uniform acceleration (probably not, but then g is constant during the acceleration).

Then for some math, solving the time over which this takes place: s(displacement)=0.5(u(inital speed)+v(end speed))t -> 91=0.5(0+107)t t ~=1.68s

Then solve the acceleration: s(displacement)=0.5a(acceleration)t(time)^2 -> 91=0.5a(1.68^2) -> a~=63.6 m*s^-2
1 g is approx 9.8 m*s^-2 so dividing by these yields it in g-forces: approx 6.49g

Re:A linear induction motor is not a railgun.

[Anonymous Coward]

Yeah, had to laugh / call bullshit as soon as I read the first sentence. If it were a railgun launcher you'd maybe see part of the front wheel go shooting down the runway at mach 5, but the rest of the plane wouldn't go anywhere and just fall over nose down.

Re:A linear induction motor is not a railgun.

[Wyatt Earp]

A lot fewer moving parts and better control over the stroke energy

Looks like they've done over 220 test fires of this already in 2010

http://www.navair.navy.mil/NewsReleases/index.cfm?fuseaction=home.view&id=4468

http://en.wikipedia.org/wiki/Electromagnetic_Aircraft_Launch_System#Advantages

Re:A linear induction motor is not a railgun.

[elfprince13]

Not really. Acceleration with non-zero jerk will involve different calculations than constant acceleration. There's a reason Hooke's law isn't the first thing they teach you in a high school physics class. The physical interpretation of the calc

Re:A linear induction motor is not a railgun.

[LetterRip]

One wonders how is that any easier on the airframe?

Anyone know how you calculate G-forces in this kind of acceleration?

It isn't the total acceleration, it is the change in acceleration (jerk) that stresses the airframe. The steam catapult has a lot of jerk, the induction system can minimal jerk.

Re:A linear induction motor is not a railgun.

[John Hasler]

I was wondering what advantages this has over steam. Maybe it's easier to route cables than pipes?

Much easier.

On the other hand, you're already producing steam for the engines

They are producing steam for the generators that produce electricity for the engines.

...steam pipes don't short when they get wet.

The Navy has been using large electrical machines on shipboard for over 100 years. I think they know how to keep seawater out of them.

Re:A linear induction motor is not a railgun.

[MattskEE]

Same accelerator concept though. Maybe what they have built is flexible enough to handle both roles.

No, they're not the same concept, and the electromagnetic plane launcher that they are building here cannot readily be re-purposed as a railgun.

The EMALS (electromagnetic air launch system) is a Linear Induction Motor which works just like a standard AC motor except it has been laid out flat instead of in a circle. The launch carriage has a set of alternating magnetic poles (the stator) and it is driven by a series of series of coils which are driven with the appropriate AC waveform as the carriage passes overhead.

A Railgun contains no permanent magnets, it uses a current through the projectile (or through a projectile carrier) to create a Lorentz force with the current in the rails which propels the projectile.

In principle one could attempt to design a linear induction motor as a weapon, but since the point of a railgun is to achieve extremely high exit velocity (current Navy efforts have achieved on the order of 2.5km/s, shooting for 5km/s) it will be very challenging to achieve the appropriate rise/fall times in the driving coils. The need for permanent magnets in the projectile are also a problem, and I imagine there would be issues with magnetic fields saturating the projectile unless the magnitudes are limited, meaning the weapon must be longer.

I could see a role for LIM directly as a weapon only if there were some application where you need to launch a relatively very heavy projectile at relatively small exit velocity.

Re:A linear induction motor is not a railgun.

[jklovanc]

This calculates the average acceleration over the distance. What if the acceleration is not constant. As has been stated by another poster, steam catapults accelerate better at the start than at the end. What if the initial acceleration was 8.3g at the start and linearly declined to 4.3G at the end. The final velocity would be the same and the average acceleration would be the same but the stress on the aircraft and pilot would be higher.

Another poster touched on a valid point about jerk. Nothing instantaneously goes from at rest to 6.3g acceleration. There is a small space in time that the acceleration changes. By controlling that transition stress on the airframe and pilot is reduced.

Re:A linear induction motor is not a railgun.

[John Hasler]

The EMALS [navy.mil] (electromagnetic air launch system) is a Linear Induction Motor...

Actually, it's a linear synchronous motor.

Re:A linear induction motor is not a railgun.

[MattskEE]

>The EMALS [navy.mil] (electromagnetic air launch system) is a Linear Induction Motor...

Actually, it's a linear synchronous motor.

Right you are, thanks for the correction. A linear induction motor would actually be closer to a railgun, although still not quite there.

Re:A linear induction motor is not a railgun.

[nospam007]

"I could see a role for LIM directly as a weapon only..."

It fires armed airborne bomb/missile launchers, sounds like a weapon to me.

Re:A linear induction motor is not a railgun.

[Brett Buck]

Perhaps. But depending on the capacity of the steam reservoir - which is presumably huge on a nuclear aircraft carrier - the pressure drop is almost certainly negligible. What the motor permits (just looking at the performance aspects) is the acceleration curve to be tailored to the airplane.

Re:A linear induction motor is not a railgun.

[MorePower]

Cooool! How do you put field current into the, um, rotor? (carriage, I guess)? I guess metal wheels would work.

Re:A linear induction motor is not a railgun.

[fluffy99]

"I could see a role for LIM directly as a weapon only..."

It fires armed airborne bomb/missile launchers, sounds like a weapon to me.

Actually they are developing railguns for launching projectiles and weapons. If the weapon doesn't need to have a chemical propellant it makes it much smaller and you can carry a lot more. All electric propulsion is being worked on as well. This is all part of the larger Navy initiative towards all-electric ships. Electricity is cheap and plentiful when you have up to 8 reactors onboard.

As a side note, the Navy did a study for converting smaller ships to nuclear instead of oil. The cross-over point for total cost of ownership/operations was at $140/barrel for oil.

Re:A linear induction motor is not a railgun.

[kindbud]

Perhaps. But depending on the capacity of the steam reservoir - which is presumably huge on a nuclear aircraft carrier - the pressure drop is almost certainly negligible.

It's not. I've manned the steam generator control station on an aircraft carrier, and the drop in water level and steam pressure is dramatic and it takes several minutes to recover. Of course, we had 16 steam generators on the USS Enterprise in the 80's. Perhaps the newer carriers with just 4 steam generators (2 per reactor) are more efficient. But I do recall flight ops were a very very busy time for the MMs in the hole.

This looks like a big improvement. Electricity generation is a much closer to a steady-state kind of operation for a naval nuclear power plant.

Re:A linear induction motor is not a railgun.

[BitterOak]

You know that the starting velocity is zeroish(maybe a little bit of taxiing; but negligible) and that the end velocity is 240mph; this makes calculating average acceleration over those 300 feet trivial;

Actually, it doesn't. Average acceleration is defined as the change in velocity divided by the time interval over which the velocity changes: a_avg = delta v / delta t. The problem here is that you aren't given delta t, but rather the distance through which the jet accelerates. Now, if you know the acceleration is constant, it is easy to calculate the acceleration by means of the formula v_f^2 = v_i^2 + 2a delta x, but for non-constant acceleration, delta t over a fixed distance will depend on the shape of the acceleration curve. Therefore the average acceleration will also depend on the shape of the curve.

Re:A linear induction motor is not a railgun.

[kindbud]

They are producing steam for the generators that produce electricity for the engines.

Are you sure about that? Isn't the Gerald Ford one of the Nimitz class carriers? Those have steam turbines to turn the screws. ...after Wikipedia lookup...

Nope, it's the first of a new class. How about that. Last time I saw an electric motor turning a screw was at prototype training following nuclear power school.

Damn! They're going to launch it with systems installed that only use half the available generating capacity. They expect to be able to put lasers on it in the future and have the juice to fire them. Sci Fi is no longer Fi.

Re:A linear induction motor is not a railgun.

[afidel]

The advantage is they are building in massive electrical generation and distribution into this generation of carrier. They are looking forward to railgun and solid state laser point defense systems to replace the current CIWS which is thought to be outclassed by today's best surface skimming missiles and will surely be outclassed during the 50+ year horizon for the class. Add in reduced maintenance and increased availability during peak operating times (all jets scramble) and you have an easy sell. It's also much easier to patch a damaged electrical system, all you need is the right gauge spare cable and a few tools. With a steam system you have to find the leak (no TDR) and patch it to a high pressure steam fight finish, a much more difficult task.

Re:A linear induction motor is not a railgun.

[afidel]

I could see a role for LIM directly as a weapon only if there were some application where you need to launch a relatively very heavy projectile at relatively small exit velocity.

I wonder if you could get a LIM up to enough velocity to launch shore bombardment shells? Then again I'm not sure enough electro-chemical storage for such a system would be any less dangerous than a powder magazine if it should be hit =)

Re:A linear induction motor is not a railgun.

[apoc.famine]

If you've got seawater on your flight deck, there's a pretty good chance you're not launching airplanes off it...

Re:A linear induction motor is not a railgun.

[Hylandr]

Since you seem to be the expert, can you please give us that equation so the rest of us can perform said simple task?

- Dan.

Re:A linear induction motor is not a railgun.

[AK Marc]

An induction motor of this type should have nearly linear force, thus you could assume the acceleration to be constant and that would be a reasonable assumption. With that assumption, then the answer does become trivial.

I'll round 240 mph to 100 m/s and 300 ft to 100 m. Why? Because I don't do imperial (born and bread in the US, and use SI whenever I can).

That makes the average acceleration 100 m/s^2. Trivially. If you think that wrong, then come up with a better answer. "I think that requires too many assumptions" doesn't work.

Re:A linear induction motor is not a railgun.

[Anonymous Coward]

Bread? Yep, you have an education from the states.

Re:A linear induction motor is not a railgun.

[Cold hard reality]

It's actually 50 m/s (5G), from a*x = v^2/2

Re:A linear induction motor is not a railgun.

[Goldenhawk]

Uh, not so fast. The US Navy boasts almost all-weather ops.

http://www.youtube.com/watch?v=EZRMpxUniOw
http://www.youtube.com/watch?v=ZoBZUQLBrp8

Launching aircraft or not, the equipment is still right there in the same spot.

Re:A linear induction motor is not a railgun.

[Anonymous Coward]

As being an MM many years ago, I can attest that steam is a real bitch to deal with. First there's a lot of maintenance involved to keep the cat risers in top order. And the steam to operate them places a lot of demand on the plants. If it's hard to "make water" for some reason, some birds may not be flying that day. (Running generators to charge capacitors means you could keep a lot more of that water in closed loop and a lot more held in reserve.) Not only that, but steam isn't exactly the most efficient working medium. Steam or at least the heat associated with it has a funny tendency to leak out in places and thermal insulation isn't perfect, so you have a lot of spaces on a carrier that can inadvertently become saunas. (And it's already too F'ing hot in places like the Persian Gulf. A/C can't always win when adjacent to some steam system.) A slow leak (as opposed to a much more noticeable one that's jetting out), is going to end up with a lot of water or condensation pooling around somewhere. (There's usually catch trays for that, but that means more plumbing. And those drains can and will plug up at times. Not to mention extra valves for DZ and all that.) Also with the rush of steam in pipes, there's a LOT of noise generated. Just the whoosh of the mass moving, or constant tic-tic-tic of thermal expansion and places where water hammer may be occurring in the lines. Then of course with the steam catapult systems, there's these huge pistons. So those things are massive in their own right in addition to the weight of the aircraft. And they're not exactly easy to work on and require a whole lot of grease. If there's a big enough problem with one of those, the carrier pretty much has to go back to the shipyard.

Now some old timers may look at it with disdain, as it makes A-Div less needed aboard ship. Not to mention there'd be less talk between M-div and topside. But from my perspective, anything that means less running outside of the plant for engineering means that the ship would be operating much more efficiently. Less shit to fix, and therefore less shit to go wrong. Then again life in E-Div on a carrier will probably get more interesting, as more and more systems go from steam to electric and require EMs where MMs used to be involved.

Re:A linear induction motor is not a railgun.

[ScrewMaster]

Bread? Yep, you have an education from the states.

You are presuming that it was a spelling error rather than a simple typo.

Re:A linear induction motor is not a railgun.

[DaveAtFraud]

When my brother was on the USS America (1973) they had a few waves break over the flight deck during a cruise that took the ship north of the Arctic circle. He took some really spectacular pictures so not just "a story." The America was only a tad smaller than the Nimitz and Ford. They wouldn't have been there if they didn't think they could operate aircraft.

Cheers,
Dave

Re:A linear induction motor is not a railgun.

[tagno25]

or the entire plane would, but it would be a small pile of metal, oil, fuel, and human remains.

Re:A linear induction motor is not a railgun.

[bruce_the_loon]

You've missed the second derived acceleration formula. a = (v^2 - u^2)/2s

Makes me sad for physics education in schools these days.

Re:A linear induction motor is not a railgun.

[Anonymous Coward]

Average acceleration is defined as the change in velocity divided by the time interval over which the velocity changes: a_avg = delta v / delta t. The problem here is that you aren't given delta t, but rather the distance through which the jet accelerates.

Explain why V**2 = u**2 + 2as would not give the average acceleration.

Re:A linear induction motor is not a railgun.

[rrohbeck]

Agree. It looked like the acceleration could be smoother at the beginning, in the first 10th of a second. There was a big jerk at first.

Re:A linear induction motor is not a railgun.

[Neil Boekend]

[continuing] A linear induction motor on the other hand is build of a fixed long rail of coils, individually controlled. The moving part is a magnet (or another coil, but that's more difficult albeit more powerful). By enabling the different coils in the right sequence the magnet moves.
A mag-lev train works in the same way, but of course these use the magnetic fields for friction-free bearings as well.

Re:A linear induction motor is not a railgun.

[arivanov]

Not necessarily. Multiple injection steam pusher is a concept old as the world. Most submarine launchers are like that - as the missile goes up more nozzles come into play on the sides giving it a good enough kick to clear the submarine and the water above it without breaking it in the process.

The article misses the biggest advantage of electric vs steam. Electric has a much lower chance of failures in sub-zero temperatures. Steam is a nasty business at -5 or less. It condenses and freezes at all the inevitable leaks along the catapult pusher path. A couple of launches and the pusher is bound to get stuck damaging the aircraft in the process.

IMHO, A ship with an electric catapult (or a ramp) has "Arctic/Antarctic war" stickered all over it. On the positive side this means that we are done with the Gulf and its surroundings. On the negative side this is one place which has seen very little war (except the North Atlantic portion of the Arctic in 1941-44).

Re:A linear induction motor is not a railgun.

[ShooterNeo]

I think you meant to say "peak acceleration". You graph the acceleration at a bunch of time intervals during the launch and the peak is the highest value. (or there's a way to figure it out using calculus if you have an equation for acceleration vs time)

Re:A linear induction motor is not a railgun.

[Jubedgy]

Not to mention that with steam system maintenance comes pages and pages of quality assurance paperwork. Do the skimmers trust ships force to do that kind of work still, or would that be an IMA level job?

Is the steam going through it generated in the actual S/G's and so would that limit maintenance on the steam portion to nukes? I'd be pissed if I had a bunch of MIPs for coner equipment I had to maintain...though I guess that's what the electricians have to live with.

Re:A linear induction motor is not a railgun.

[Churnits]

Bah! Just go and watch Top Gun and time how long it takes for them to take off on your watch.

Re:A linear induction motor is not a railgun.

[shutdown -p now]

It's certainly an interesting post, but with all the mysterious acronyms scattered around, it kinda feels like reading the latest treatise on agile software development. Can you explain what DZ, MM, EM, A-Div, M-Div and E-Div are for better understanding?

Re:A linear induction motor is not a railgun.

[fotoguzzi]

And activities in the Aleutian Islands.

Re:A linear induction motor is not a railgun.

[norpan]

There are only two significant figures in 240, and only one in 300. Please do not do metric conversions with more significant figures than your inputs.

On the contrary, please don't drop significant figures during intermediary calculations. But do round the final answer to 6.5.

Re:A linear induction motor is not a railgun.

[AliasMarlowe]

You've missed the second derived acceleration formula. a = (v^2 - u^2)/2s
Makes me sad for physics education in schools these days.

No, he didn't. He expressed it in a trivially rearranged form:

easy to calculate the acceleration by means of the formula v_f^2 = v_i^2 + 2a delta x

Makes me sad for the state of reading comprehension.

Re:A linear induction motor is not a railgun.

[Jonner]

Same accelerator concept though. Maybe what they have built is flexible enough to handle both roles.

Yeah, it's the same concept much as a firearm and internal combustion engine are based on the same concept. How many gasoline engines are also capable of firing high velocity projectiles?

Re:A linear induction motor is not a railgun.

[wisty]

Or maybe EM accelerators act on the whole airframe, while catapults need to be hooked onto specific points, so there is essentially no internal stress with the "rail gun" (except for stress on non-magnetic parts, like the pilot).

Re:A linear induction motor is not a railgun.

[hitmark]

Especially if one can have staggered banks of capacitors sitting, so that one or more bank charges while another is used to get the aircraft up. Unless the turbines of the reactor can power these things directly without any need for buildup. Then its a simple question of flipping the switch.

Re:A linear induction motor is not a railgun.

[bruce_the_loon]

I meant he missed the point of it. Average acceleration is a average line through the entire acceleration profile and can be simply calculated by the formula as stated by the GGGP.

Re:A linear induction motor is not a railgun.

[riverat1]

No, the aircraft are still hooked up by the nosewheel to the catapult. It's as blackraven said. They can control the acceleration more finely with a linear induction motor than with a steam driven catapult.

Re:A linear induction motor is not a railgun.

[Anonymous Coward]

Linear induction motors (sometimes referred to as coil guns) and rail guns work on different principles. The author of the original article has made the mistake of conflating the two, calling the catapult system a rail gun, where it is actually based on an induction motor.

Steam catapults work on steam pressure, which will be higher at the beginning of the launch, putting higher transient loads on the airframe. The amount of force from a steam catapult is harder to regulate than an induction motor. An induction motor system works similarly to an electric motor so you can control the force it applies to give an even acceleration along the whole length of the path, placing lower peak loads on the airframe of the aircraft being launched. Because of its even power delivery, it can produce a consistent force along the whole length of the take off run and apply more useable power overall.

G forces are a function of the amount of force and the mass of the object. For an item of a given mass, the harder you push, the higher the G force. For the same amount of force, a lighter object will be accelerated faster. A fighter aircraft needs more force to accelerate it to a given speed than a drone that might weigh 1/4 as much and is probably not built to take 4x the acceleration loads of a fighter. With an induction motor, it's much easier to just turn down the power when you're launching a lighter drone aircraft.

The catapult is unlikely to suit adaptation as an artillery system - for a start, it's 300 feet long. Most of the research into electromagnetic artillery systems concentrates on rail guns because it's easier to use one to accelerate a small object to high speeds. This is a different problem.

Re:A linear induction motor is not a railgun.

[mpe]

Actually they are developing railguns for launching projectiles and weapons. If the weapon doesn't need to have a chemical propellant it makes it much smaller and you can carry a lot more.

Possibly also a higher rate of fire and able to sustain fire for longer without the the gun overheating.

Re:A linear induction motor is not a railgun.

[JustinRLynn]

MM = Machinist Mate, think Mechanical Engineer but for maintenance operations on mechanical equipment. EM = Electrician's Mate, think Electrical Engineer but for maintenance operations on electrical equipment. A-Div: various shops and other groups that maintain the mechanical systems such as Hydraulics, AC, Steam and Heat, the catapults, fire pumps and water distribution systems, among others. M-Div: Machinery division refers to the group of MMs. E-Div: same for EMs. Afraid I don't know what DZ means, though it's a METAR code for drizzle, so perhaps that's what's being referred to. No first hand knowledge here, just stuff gained from reading, so please if you've got first hand or links, please correct.

Re:A linear induction motor is not a railgun.

[sglines]

That is going to be one electronically loud ship. Nothing like electronic stealth to fight the blue meanies with.

Re:A linear induction motor is not a railgun.

[peragrin]

well that and electricity is easier to do a larger variety of things with. You need to go faster, divert power from weapons, and aircraft launching to the motors. (up to hull speed more)

It sounds like Science ficition, but that is how many of the ships of today operate. They are using diesel electric engines and driving electric motors for speed. You can keep pumping electricity into them until you fry something. you just keep going faster and faster, until you hit top hull speed, then it doesn't do you any good.

The Navy and Army are also looking into localised biomass-fuel converters. Can you imagine a Carrier that can make it's ownJet fuel. Even if it is only 30% of what is needed it is a huge help. They need electricity too.

Re:A linear induction motor is not a railgun.

[MightyYar]

His typing teacher was British.

Re:A linear induction motor is not a railgun.

[Anonymous Coward]

I believe that the engagement of the Civil War took place in the area of the Aleutians...

Re:A linear induction motor is not a railgun.

[Nyh]

To accelerate a 100000 pound object to 240 mph requires an energy of 260 MJ (sorry I converted all units to SI before I started calculating so you have to convert it back to BTU or kcal or whatever the right unit for energy you want to use yourself). Assuming a linear acceleration over 300 feet to 240 mph gives an acceleration time of 1.7 s. This results in an average power of 153 MW. AFAIK there is no electrical turbine that will supply an extra 153 MW at the flip of a switch. Electrical energy has to be stored somewhere to let the catapult work.

Nyh

Re:A linear induction motor is not a railgun.

[peterbye]

A lot fewer moving parts and better control over the stroke energy
And a lot less dangerous for the deck crew with no steel cables whipping about

Re:A linear induction motor is not a railgun.

[John Hasler]

> How do you put field current into the, um, rotor?

You don't. It uses permanent magnets.

Re:A linear induction motor is not a railgun.

[John Hasler]

> EM = Electrician's Mate, think Electrical Engineer

The "Mates" are skilled technicians, not engineers.

Re:A linear induction motor is not a railgun.

[JustinRLynn]

Right right, should've been more clear on that.

Re:A linear induction motor is not a railgun.

[Anonymous Coward]

Perhaps. But depending on the capacity of the steam reservoir - which is presumably huge on a nuclear aircraft carrier - the pressure drop is almost certainly negligible.

It's not. I've manned the steam generator control station on an aircraft carrier, and the drop in water level and steam pressure is dramatic and it takes several minutes to recover. Of course, we had 16 steam generators on the USS Enterprise in the 80's.

32. Eight reactors, 4 steam generators per reactor.

Perhaps the newer carriers with just 4 steam generators (2 per reactor) are more efficient. But I do recall flight ops were a very very busy time for the MMs in the hole.

...

Nope. Somebody was lying to you. We just needed to watch our water levels in the secondary. Which on the EnterPig you had to be on top of anyway - and that was 20+ years ago. I can't imagine how bad that ship is now.

Of course, some could fuck up even the watching of water levels. One PPWO "lost" 7,000 gallons of water - and it wasn't even during flight ops. Since the 4 steam plants on the Enterprise could be interconnected in some ways, he was calling around to the other EOS's trying to find his lost water. The joke in the wardroom later was, "How the hell can you lose 7,000 gallons of water? And not be able to find it? 7,000 gallons of water will find YOU!" Prior to this incident, this one officer's nickname was "Rock" - as in "dumb as a". After someone remarked "He's not a rock, he's a fucking boulder" because of the "lost" water, he was known as "Boulder".

The full nickname has been redacted to protect the not-so-innocent.

Re:A linear induction motor is not a railgun.

[John Hasler]

Unless the turbines of the reactor can power these things directly without any need for buildup.

They can't, but the system stores energy in flywheels, not capacitors.

Re:A linear induction motor is not a railgun.

[Ornlu]

The acceleration is 207.5 ft /s^2. That's 6.4G.

Re:A linear induction motor is not a railgun.

[GooberToo]

The steel cables are used for the aircraft recovery arresting system. Basically, aircraft have a hook which catches one of the cables as the aircraft hits full throttle in case it misses, as can be seen in the beginning of this video. If it catches, the cable then slows and stops the aircraft on the deck. If they miss, the must go around an try again; which is why they are at full throttle.

Re:A linear induction motor is not a railgun.

[SHaFT7]

Then go take a shower? With other guys?

Re:A linear induction motor is not a railgun.

[Beezlebub33]

Well, the arrester wires are still there, and they always seemed more deadly to me.

Re:A linear induction motor is not a railgun.

[couchslug]

"A linear induction motor is not a railgun. "

Except when trolling for page hits. :)

Re:A linear induction motor is not a railgun.

[confused one]

Same accelerator concept though.

Unless you mean: "uses electrodynamics to drive the sled forward", you're wrong. They're not even close.

Re:A linear induction motor is not a railgun.

[Anonymous Coward]

it would seem they just pushing it at full throttle for the whole distance.

Yep, unimpeded by any pesky linking verbs.

Re:A linear induction motor is not a railgun.

[Anonymous Coward]

There are only two significant figures in 240, and only one in 300. Please do not do metric conversions with more significant figures than your inputs.

Zeros can't be significant?

You fail.

Re:A linear induction motor is not a railgun.

[sean.peters]

Maybe what they have built is flexible enough to handle both roles.

It's not. The Navy is working on a separate rail gun system as a weapon. EMALS, because of its physical configuration, would not be capable of launching weaponry.

Re:A linear induction motor is not a railgun.

[Anonymous Coward]

7,000 gallons of water will find YOU!"

You just blew your cover, Boris. It sounds like you were serving on a Soviet Russian carrier.

Re:A linear induction motor is not a railgun.

[Migraineman]

I'm wondering if the ham radio guys will be able to hear carrier operations. "Fwwweeeep!" Hey Earl, that sounded like an F/A-18.

Of course, that information works for both sides. When your opponent is listening to your carrier ops, you run the EM launcher a bunch of times, leading him to believe a fighter wing is inbound.

I'm sure they've considered RF emissions. If for no other reason, RF emissions are energy in the system that's not used for the primary purpose.

Re:A linear induction motor is not a railgun.

[gman003]

Surprisingly, your deduction of where the Navy expects the next war to be isn't too far from reality. As the Artic cap melts, significant oil reserves are being uncovered, and both the US and Russia are making claims to it. There's already been some minor show-of-force incidents, but a full naval war is not completely impossible.

Re:A linear induction motor is not a railgun.

[EvilBudMan]

I thought they already put a magnetic catapult on the last Nimitz class carrier built. It's already been proven in amusement park rides and it is easier on the planes, however, the nuclear power generators on the Ford are supposed to be very powerful. They might be even powerful enough to power a laser capable of bringing down supersonic sea skimming missiles and supercavitating torpedoes. That would be cool but using maglev tech to launch planes is old news.

Re:A linear induction motor is not a railgun.

[EvilBudMan]

It's a huge improvement. I thought the last Nimitz class carrier was going to get this as well. I wonder what they are going to call the new ones? The "Ford" class just doesn't sound quite right. The USS Enterprise had the most battle stars of any ship in WWII. The one you were on will be in service for over 50 years (the second oldest ship behind the Constitution). And then there is there Star Trek thing. That will leave us without a naval vessel named Enterprise. Something about that just doesn't sound right.

Re:A linear induction motor is not a railgun.

[Anonymous Coward]

I converted all units to SI before I started calculating
[...]
over 300 feet to 240 mph

Oops.

Re:A linear induction motor is not a railgun.

[Anonymous Coward]

Well if the new British carriers have these installed, which I believe they're due to, then they might be useful in the South Atlantic if Argentina gets a bit feisty, which they do, every time they have an internal political crisis and need to deflect attention away from problems at home with a bit of good old fashioned nationalism.

Last time there was no issue because they used the invincible with it's ramp, and harriers which are of course VTOL capable anyway. As they've been ditched for F35s towards the end of the decade whose VSTOL capability may well still be limited to STOL then something like this may well be necessary to protect British South Atlantic and Antartic territory.

Re:A linear induction motor is not a railgun.

[jklovanc]

For simplicity sake I will use some round numbers.
Vf = 100m/s
d= 100 m

By the constant acceleration equation 100^2/2*100 = a = 50m/s^2 Since the acceleration is constant the average speed is Vf/2 = 50m/s therefore dt = 2 seconds. By definition constant acceleration is also average acceleration.

Now what would happen if all the acceleration happened in the first ten feet.
The constant acceleration equation would be 100^2/2*10 = 500m/s^2 Average speed is still 50m/s therefore it would take 10/50 = .2 Seconds to travel the 10 m. The other 90M would be covered at a speed of 100m/s therefore dt for that segment would be 90/100 = .9. The average acceleration would be (500*.0.2 + 0*0.9)/(0.2+0.9) = 90.9m/sec2

Since 50m/s^2 90.0m/s^2 the poster is correct that average acceleration is dependant on the shape of the acceleration curve.

Re:A linear induction motor is not a railgun.

[drinkypoo]

My understanding of the reason that they reduced the number of reactors after the Enterprise was that anything that took even one of them out of commission was pretty much going to reduce it to fleeing and you don't need a grip of reactors for that. The plan for a carrier is for it to be well-defended enough to not need that kind of redundancy.

This looks like a big improvement. Electricity generation is a much closer to a steady-state kind of operation for a naval nuclear power plant.

It seems to my untrained eye and brain that the major advantage here is that control of electricity is easier than control of steam. It causes less parts to wear out, they wear out more predictably, and they are easier to replace. Either way you're having to deal with a similar amount of power to get the same job done and given a rate of power production (it is my understanding that nuclear reactors don't get turned up and down as quickly as my rangetop) many of the issues with a steam catapult will be present with any catapult.

Re:A linear induction motor is not a railgun.

[Anonymous Coward]

We call such a storage system: Capacitor

Re:A linear induction motor is not a railgun.

[Libertarian001]

I'll concur. Parent was standing Feed Control Operator in Engine Room Upper Level. I was standing Feed Pump Operator in Engine Room Lower Level. Our watch stations had to talk on head sets to coordinate.

Re:A linear induction motor is not a railgun.

[Anonymous Coward]

http://zonalandeducation.com/mstm/physics/mechanics/kinematics/EquationsForAcceleratedMotion/EquationsForAcceleratedMotion.htm

Re:A linear induction motor is not a railgun.

[tehcyder]

a full naval war is not completely impossible.

Only in the minds of naval planners.

The US isn't going to piss around with boats when they've got fucking nuclear missiles to scare the Russians off with.

Re:A linear induction motor is not a railgun.

[Fyzzler]

I did it in English units, but my answers match yours. Assuming constant acceleration with zero velocity at start. 240 mph terminal velocity over 300 feet. Time = 1.7045455 seconds, and acceleration is 206.50667 feet/sec^2 which works out to a gforce of 6.4533333

This was a nice opportunity to use the Scilab 5.3 that I just installed this morning.

Re:A linear induction motor is not a railgun.

[shadowfaxcrx]

Of course they are. Don't forget the Russians have fucking nuclear missiles too, and they have an annoying plan to launch them if we ever launch ours.

The nukes will be deployed only when it's obvious we're about to lose the conventional war in a big way, just as theirs will be.

Re:A linear induction motor is not a railgun.

[VolciMaster]

My understanding of the reason that they reduced the number of reactors after the Enterprise was that anything that took even one of them out of commission was pretty much going to reduce it to fleeing and you don't need a grip of reactors for that. The plan for a carrier is for it to be well-defended enough to not need that kind of redundancy.

The Enterprise, as the first nuclear naval vessel, went with a very conservative design - they put in one reactor to replace each of the diesel engines on the previous design, ending up with 8 reactors.

Re:A linear induction motor is not a railgun.

[shadowfaxcrx]

Why would that be a reasonable assumption. Far more reasonable would be that the curve would get steeper over time. It would be easier on the airplane if you started (relatively) slow and increased power to get to the required takeoff speed by the end.

Think of a car. It's pretty easy to take 1g of lateral acceleration if you're on a skid pad and build up to it - quite another to take 1g when it's from being hit by a truck.

Looking at current common applications of these motors in launch situation - roller coasters, you'll notice that the LIM doesn't just blast them instantly to 90mph. It actually starts out somewhat slow and then accelerates them (relatively) gently over time.

Re:A linear induction motor is not a railgun.

[Fyzzler]

Slight correction. G-force is 6.4184332 My prior answer used 32feet/sec^2 instead of g = 32.174 ft/s^2

Re:A linear induction motor is not a railgun.

[kimvette]

It couldn't be done that way; legacy fighters are mostly aluminum, newer ones are built mostly of pressed composite layups or molded composite plastics.

The aircraft is being towed just as with conventional catapults; you can plainly see the brackets in the video. One bracket in front of the wheel at about 45* angle, and one in the back at about a 30* angle. The piston (not the correct term) upon which the linear motor works is what those rods are connected to. The aircraft is basically going along for the ride, and is not part of the linear motor.

Re:A linear induction motor is not a railgun.

[Anonymous Coward]

OMG, you served in the engine room on the Enterprise!!!!!
I feel like a total fangirl, but what's Scotty like in real life?
Which color shirt did you wear?

Re:A linear induction motor is not a railgun.

[budgenator]

Probably not, as the steam piston moves down the bore, it takes increasing volumes of steam to be delivered to maintain the constant presure and that is unlikely to be possible. The gas flowing through the pipes is going to encounter resistances which will cause presure and temperature flucuations, the nice dry superheated steam is going to have areas where condesation occures and saturated steam results causing even more flocuations. Most of these effects will be chaoic and erratic so they build some over-kill into the system to compensate. The video of the launch looked real nice and smooth, regualar steam catpults launches seem much more jerky.

Re:A linear induction motor is not a railgun.

[ceswiedler]

You know, this is why I still read Slashdot. For one out of every 100 opinions, someone will step up with an obscure but useful bit of knowledge or experience.

Re:A linear induction motor is not a railgun.

[Anonymous Coward]

It gets pretty cold during winter around the Korean Peninsula...

Re:A linear induction motor is not a railgun.

[Anonymous Coward]

Not really. Acceleration with non-zero jerk will involve different calculations than constant acceleration. There's a reason Hooke's law isn't the first thing they teach you in a high school physics class.

It's still easier than the alternative; solving any math/physics problem on slashdot with zero jerk seems to be an impossibility...

Re:A linear induction motor is not a railgun.

[mrmeval]

http://en.wikipedia.org/wiki/Electromagnetic_Aircraft_Launch_System

The energy is stored

Energy storage subsystem: The induction motor requires a large amount of electric energy in just a few seconds -- more than the ship's own power source can provide. EMALS' energy-storage subsystem draws power from the ship and stores it kinetically on rotors of four disk alternators.Each rotor can store more than 100 megajoules, and can be recharged within 45 seconds of a launch, faster than steam catapults.

The A1B reactor produces about 312MW though an exact figure is elusive I found one article that stated they put out approximately 3 times the A4W reactors output.

Oddly that article claims a launch energy of 122MJ yet the following statement matches your initial numbers. The EMALS' 300-foot (91 m) LIM will accelerate a 100,000-pound (45,000 kg) aircraft to 130 knots (240 km/h). it could be the 240km/h should be used in lieu of 240mph?

Re:A linear induction motor is not a railgun.

[budgenator]

In 20 years you'll probably need an arctic ice break to keep the Puget Sound open. There hasn't been any statistically significant global warming for 15 years and the last 2 years have been frickening cold. It's snowing all over North America, It's snowing all over Europe, it's snowing all over Asia and winter just started! Hell it's even snowing in Australia, and it's Summer down under. Air temperatures are plummeting, Sea Surface temperatures are falling and Sea Ice extent and thickness is rebounding, oh and Polar Bear are population is much higher than previously thought.

Re:A linear induction motor is not a railgun.

[kindbud]

The USS Enterprise uses the same reactor design as the USS Long Beach CGN-9 (now decommissioned and sitting as a decapitated hulk in Bremerton, WA.). The Long Beach was the first nuclear powered surface vessel ever launched. The Navy only had two designs in the early 60's, one for subs and one for surface vessels. The Big E got 8 reactors because that's how many it took to drive it and also generate steam for the catapults. The Long Beach had two of them. Of course, she had no catapults.

Re:A linear induction motor is not a railgun.

[peterbye]

Thanks for the clarification, I was thinking the steam catapult was like a real catapult, with a wire that pulled back and released.

Re:A linear induction motor is not a railgun.

[Z8]

No, BitterOak's post already said that it would be trivial under the assumption of constant acceleration, but the average acceleration in the absence of that assumption depends on the shape of the curve.

To give a simple example, suppose the aircraft is given a small impulse at t=0 to give it an infintesimal velocity. A year later it reaches the end of the rail and is given a huge impulse to get it to 240mph. The average acceleration is quite small because it took the jet a year to only accelerate 240mph total.

Re:A linear induction motor is not a railgun.

[MerlynEmrys67]

I am assuming that they use stored electricity... But not all that power will be provided by the catapult. There are engines on the plane that produce thrust as well running at full throttle. I would assume that they can provide some of that 153 MW of work during the launch.

Re:A linear induction motor is not a railgun.

[Anonymous Coward]

DZ = Dog Zebra

The US Navy (and probably other navies as well) have specific "material conditions" to control flooding/fire. Condition Z (phonetically Zebra) is a very high state of readiness, generally associated with the ship being at General Quarters. DZ fittings, such as valves, hatches, and doors, must be closed when Condition Zebra is set. The DZ fittings must also be closed when the ship is running in a darkened state to prevent stray light sources from giving away the position of the ship.

Re:A linear induction motor is not a railgun.

[Anonymous Coward]

Which means they know a lot less calculus and are a lot more useful.

Re:A linear induction motor is not a railgun.

[riverat1]

Yeah, the negative global cooling trend.

Re:A linear induction motor is not a railgun.

[riverat1]

While you're freezing your ass off there was rain in Barrow, Alaska in mid November and temperatures in Western Greenland have been around 18 F higher than normal for this time of year. Arctic sea ice for November was the 2nd lowest on record after 2006 which preceded the record sea ice minimum of 2007. December isn't doing much better.

Regarding your comment "There hasn't been any statistically significant global warming for 15 years..." here is the exact transcript excerpt of what Phil Jones said that is the source of that denier meme:

BBC: Do you agree that from 1995 to the present there has been no statistically-significant global warming?

Phil Jones: Yes, but only just. I also calculated the trend for the period 1995 to 2009. This trend (0.12C per decade) is positive, but not significant at the 95% significance level. The positive trend is quite close to the significance level. Achieving statistical significance in scientific terms is much more likely for longer periods, and much less likely for shorter periods.

BBC: How confident are you that warming has taken place and that humans are mainly responsible?

Phil Jones: I'm 100% confident that the climate has warmed. As to the second question, I would go along with IPCC Chapter 9 - there's evidence that most of the warming since the 1950s is due to human activity.

The warming trend that Phil Jones calculated may not have reached the 95% confidence level of statistical significance (a somewhat arbitrary distinction) but it was over the 90% confidence level.

And 2010 may still set a new record for global temperature. It's sure to be in the top 3 years of the instrument record.

Re:A linear induction motor is not a railgun.

[nickthisname]

I, for one, am glad you enjoy paying taxes. Too bad you don't know how your civilization is maintained. There is a difference between RPG and RPG, explore this for a while.

Re:A linear induction motor is not a railgun.

[shutdown -p now]

I have no clue as to what your post is about. Can you be more straightforward?

(FWIW, I know the difference between RPG and RPG. I even know the difference between the other two RPGs!)

Re:A linear induction motor is not a railgun.

[Trongy]

Turboielectric warships were used in the earlier part of the 20th century. For example the first US aircraft carrier http://en.wikipedia.org/wiki/USS_Langley_(CV-1)

Re:A linear induction motor is not a railgun.

[noidentity]

My comment was about this linear induction motor.

Re:A linear induction motor is not a railgun.

[St.Creed]

[citation needed]

2010 is one of the three hottest years worldwide since 1850. The decade 2000-2010 is the hottest decade worldwide since recordkeeping on temperature began (which for all practical purposes is the same as "hottest decade ever!"). On what records do you base your statement?

Re:A linear induction motor is not a railgun.

[jmichaelg]

I computed a similar acceleration. Then I checked my work by watching the video and saw that the jet starts moving at 1:55 and is lifting off at 1:59 which means 4 seconds to go from 0 to 240 instead of 1.7 seconds.

.

That tells me they don't uniformly accelerate the plane and that it requires half the power to get the plane airborne than the 1.7 second calculation requires. You can see from the video that it takes the plane about a second to move its own length or 60 feet (assumed it was an f18) which means it starts out at a slower acceleration than it must have to cover the remaining 240 feet in 3 seconds.

Nonetheless, going from 0 to 240 in 4 seconds has got to be one hell of a hoot.

Re:A linear induction motor is not a railgun.

[tsotha]

There's that, but also the steam catapults have a longer cycle time. In theory the linear motors will be able to launch aircraft as fast as they can be put into position. Seems like that would be a pretty big deal if you had hostiles inbound.

Re:A linear induction motor is not a railgun.

[treeves]

The Enterprise was not the first nuclear naval vessel. The Nautilus SSN-571 was. And the second was also a submarine.

Re:A linear induction motor is not a railgun.

[riverat1]

Yeah, it's offtopic but I was just responding to budgenator's BS.

Re:A linear induction motor is not a railgun.

[Anonymous Coward]

What? The average acceleration is not dependent upon the shape of the acceleration curve. The average a is the constant a that is required to accelerate 100,000 lb to 240 mph in 300 ft. The areas under a constant a curve and a varying a curve will be identical if we are accelerating a fixed mass over a fixed distance to a known final velocity. The shape is irrelevant.

Re:A linear induction motor is not a railgun.

[AK Marc]

Why would that be a reasonable assumption. Far more reasonable would be that the curve would get steeper over time. It would be easier on the airplane if you started (relatively) slow and increased power to get to the required takeoff speed by the end.

If you needed a specific speed at a specific distance, a constant acceleration would be much easier on the airframe. Anything else requires higher peaks.

Think of a car. It's pretty easy to take 1g of lateral acceleration if you're on a skid pad and build up to it - quite another to take 1g when it's from being hit by a truck.

No, your example is poor. For one, that's a silly example because almost no crashes are that light, so people will think of higher accelerations. Also, if you design for it, 1g is not high at all and wouldn't be that big a deal. But a side-impact at 1g would be an issue because it would be a quick jolt in the direction least supported. But then, that kind of misdirection seems to be the real point of your statement, to grasp at silly false logic to justify an incorrect opinion.

Looking at current common applications of these motors in launch situation - roller coasters, you'll notice that the LIM doesn't just blast them instantly to 90mph. It actually starts out somewhat slow and then accelerates them (relatively) gently over time.

I've been on one. I think the name was Superman at Six Flags Magic Mountain (Los Angeles), however I may be mistaken on the name as it has been a few years. It most certainly did have a constant-acceleration profile, though I didn't take my accelerometer with me to verify.

Re:A linear induction motor is not a railgun.

[Shakrai]

Something about that just doesn't sound right.

Naming our flag ships after politicians really pisses me off. Yorktown, Enterprise, Hornet, Saratoga, Essex, Midway, Samar, Wasp, etc, etc. These are all names that would make a lot more sense for carriers than naming them after not-even-dead Presidents.

Re:A linear induction motor is not a railgun.

[shadowfaxcrx]

What's easier on you, if I put my hand on your head and push, or if I punch you? Call it silly all you want, but the sudden impact start is going to be harder on the airframe than the sloped acceleration.

And if you give the launcher full power from the beginning, it jolts the aircraft. My entire point was that avoiding the jolt is easier on the aircraft. If you think that's a poor-silly-incorrect-false-logic-formed opinion designed to misdirect, then it says something about your grasp of physics, much less that of common sense.

Re:A linear induction motor is not a railgun.

[hitmark]

Interesting. I keep envisioning something like those big slow wheels found on steam trains, but checking the actual topic online presents me with a much more compact but high speed system. I suspect there is some crazy materials involved in the connection between flywheel and dynamo when it comes time to dump the energy into the rail.

Re:A linear induction motor is not a railgun.

[ormondotvos]

Amazing. A completely wrong post. I got a good laugh. Your children won't.

Re:A linear induction motor is not a railgun.

[AK Marc]

What's easier on you, if I put my hand on your head and push, or if I punch you?

If you have to accelerate my head by 10 m/s^2 in 10 cm, it doesn't really matter. But your irrelevant comparisons of trauma aren't related to things like metal fatigue, which would be the points of interest. The peak acceleration of the head would be *more* if you pushed than punched, and there exist levels where punching wouldn't cause harm and pushing would.

I personally would call you a liar because you are selecting words for their emotional impact which deceive. Purposeful deception (even without a falsehood) meets my definition of a lie. And that makes you a liar. The peak acceleration (and thus, greatest trauma) must, by definition, occur with the "most gentle" acceleration. As such, you keep proving yourself wrong, but using words that attempt to coat the physics with emotion to confuse and deceive.

And if you give the launcher full power from the beginning, it jolts the aircraft. My entire point was that avoiding the jolt is easier on the aircraft.

I thought your point has devolved into "I'm right and you are wrong, and I'll say whatever it takes to make me think I've won the argument because winning arguments is important to my self image."

The gentle initial acceleration requires a greater peak acceleration, and thus greater stress on the airframe. No amount of irrelevant discussions of "jolt" (irrelevant in any properly engineered system) will affect that.

Re:A linear induction motor is not a railgun.

[shadowfaxcrx]

You know, I thought you were just rude, but now I realize you're an asshole. Even if you're convinced you're right, there are nicer ways to go about saying it, but you can't quite manage them, can you? I'm not trying to deceive, or use trickery to prove a point. You, on the other hand, are attempting to veil your complete failure to grasp basic concepts in insults. Internet bullies don't impress me or anyone else with a modicum of intelligence. Next time, try harder when you want to troll.

And by the way, no, we're not talking purely about metal fatigue, or had you forgotten that airplanes aren't just slugs of steel?

On second thought, don't bother answering that. I try not to waste too much time arguing with jackasses.

Re:A linear induction motor is not a railgun.

[AK Marc]

Your comments are solely about the "airframe" until that is properly addressed. Then you hint that you were thinking about the people inside them the whole time you were saying "airframe." When you change your argument every time someone responds in order to pretend to always be right, then you will always be right.

If you have gentle initial acceleration and a fixed distance in which to accelerate, you must have a greater peak acceleration with the "gentle" method than the "jarring" sudden and constant acceleration. Yes, I concede that a very quick ramp up to max acceleration would likely be more comfortable for the occupants. But then, I'd point out that such massive on/off acceleration has already had a good bit of studying because of the manner in which multi-stage rockets worked and that instantaneous acceleration is impossible so that even the most jarring methods will still ramp up over some small period.

But no, we can't discuss the pros and cons, instead you make up useless and confusing examples filled with emotional words picked to obviously support your position to the detriment of communication or the truth.

Re:A linear induction motor is not a railgun.

[Anonymous Coward]

The military maintains civilization? Boy is that a gas.

This kind of stupidity could only come from someone who was both stupid enough to join the military and has gone through their brainwashing regimen.

Enjoy wallowing in your own ignorance.

Re:A linear induction motor is not a railgun.

[EvilBudMan]

I guess they just ran out of Admirals on the Nimitz class. I don't get it either but I guess the one that had the most do do with keeping the money flowing and happens to be Republican gets a ship named after them. They skipped Carter and Clinton.

Hmm...The USS NIXON.

Re:A linear induction motor is not a railgun.

[Lucractius]

These unmanned aircraft mentioned in all the text could very well include a low tech drone 'cruise missile'.
That makes the catapult technically capable of launching weapons. Just not a very good one.

Very cool

[O('_')O_Bush]

Now they only need a more efficient way of catching the planes when they land.

Re:Very cool

[radish]

I'm imagining a giant electro magnet.... :)

Re:Very cool

[nanospook]

Jello..

Re:Very cool

[__aaeuwj6541]

200 kilos of ferrous + 1 sabot + 1 300f launcher = very very big gun

Re:Very cool

[Anonymous Coward]

Now they only need a more efficient way of catching the planes when they land.

According to wikipedia, It will have an electromagnetic arresting system to stop the planes. See http://en.wikipedia.org/wiki/USS_Gerald_R._Ford_(CVN-78)#Launch_systems

Re:Very cool

[reaper]

When I was working on the arrestor portion in 2001, we had a system controlling two linear induction motors attached to the arrestor cable. Turns out that yes, you can use this type of system to stop planes, it is effective in many situations where planes come in at odd angles (the system pulls the plane towards the center of the deck), and you can recover power from it.

However, if you wire the position encoders backwards, the motor cores eject quite violently as soon as the control system is turned on. Thankfully, interns are surprisingly good at dodging.

Re:Very cool

[Centurix]

As with some other technologies, I think they could take a hint from nature. In particular the frog where we fit-out every air-craft carrier with a giant sticky tongue which shoots out when the plane gets within striking distance.

Re:Very cool

[Neil Boekend]

It would be advisable not to copy to much. Crushing and digesting every plane that tries to land is way to expensive...

Re:Very cool

[ikkonoishi]

So what you need then are arrestor cables for the induction motors.

Yo dawg! I heard you like stopping dawg! So I put an arrestor on your arrestor so you can stop while you stop.

Re:Very cool

[Anonymous Coward]

How about landing on a large rubber mat?

Seriously, the Royal Navy experimented with landing a Sea Vampire on large rubber mats. See www.livingwarbirds.com/de-havilland-vampire.php for a video of it working.

They were called Flexible Decks. The brilliant Eric 'Wrinkle' Brown describes the test in one of his books. The tests were mostly successful, but the idea was not progressed with.

Anyone interested in test flying and post-war aircraft should really read Brown's books.

Rail Gun Weld

[Anonymous Coward]

Isn't one of the problems with railguns that sometimes the projectile will weld itself to the rail? What happens if that occurs with a jet launcher on the rail, and a plane hooked to that?

Re:Rail Gun Weld

[osu-neko]

Isn't one of the problems with railguns that sometimes the projectile will weld itself to the rail?

Only at sufficient speeds/friction. There's no reason a railgun-based aircraft launcher would be more prone to this problem than a steam-based one.

What happens if that occurs with a jet launcher on the rail, and a plane hooked to that?

Same thing that happens now if the thing gets stuck.

Re:Rail Gun Weld

[causality]

Isn't one of the problems with railguns that sometimes the projectile will weld itself to the rail? What happens if that occurs with a jet launcher on the rail, and a plane hooked to that?

As another poster pointed out, this technically isn't a railgun. It's a linear motor. This is more like a mag-lev train. The other big advantage is that in a real railgun, the rails need frequent replacement.

If you were expecting technical accuracy from our esteemed professional Slashdot editors, that day has not yet arrived. They're still trying to figure out how to work a spell-checker and how to use basic English grammar. As long as the ad revenues and the paid account revenues keep on flowing, I suppose they don't feel much pressure to get these things right.

Re:Rail Gun Weld

[Anonymous Coward]

This is not a rail gun. It's a plain old electric motor in linear form.

Re:Rail Gun Weld

[Rakishi]

Only at sufficient speeds/friction. There's no reason a railgun-based aircraft launcher would be more prone to this problem than a steam-based one.

As I understand the issue, it has nothing to do with friction. In fact it's probably more likely to get welded if it's going too slowly.

A rail gun is basically an arc welder in a way, you're passing massive amount of energy in the form of electricity through the interface between the rails and projectile. A high power rail gun has enough energy passing through to basically vaporize nontrivial amounts of metal off the rails every time it's fired. If you're unlucky on the other hand it'll simply weld the projectile to the rails.

Re:Rail Gun Weld

[Anonymous Coward]

Specifically, it's a linear synchronous motor.

After all, a railgun is also a linear motor, specifically a linear homopolar motor.

Really, though, this goof isn't particularly disappointing; it seems like everyone gets railguns wrong, so at least the editors have an excuse. However, they routinely pass far more obvious errors...

Re:Rail Gun Weld

[Nefarious Wheel]

Isn't one of the problems with railguns that sometimes the projectile will weld itself to the rail? What happens if that occurs with a jet launcher on the rail, and a plane hooked to that?

The pilot is in for a short, yet highly interesting flight.

Re:Rail Gun Weld

[Nefarious Wheel]

As I understand the issue, it has nothing to do with friction. In fact it's probably more likely to get welded if it's going too slowly.

A rail gun is basically an arc welder in a way, you're passing massive amount of energy in the form of electricity through the interface between the rails and projectile.....

Think of a long, overpowered Jacob's Ladder with a slug where you'd expect the expanding arc.

Re:Rail Gun Weld

[Jonner]

Isn't one of the problems with railguns that sometimes the projectile will weld itself to the rail?

Only at sufficient speeds/friction. There's no reason a railgun-based aircraft launcher would be more prone to this problem than a steam-based one.

More importantly, this catapult isn't a railgun. Unlike a railgun, there's no projectile rubbing on the conducting rails in a linear induction motor.

Space Flight?

[bl4nk]

I've always wondered, why haven't electromagnets been utilized for escaping Earth's atmosphere? It's cheaper and more

Re:Space Flight?

[cheater512]

Rockets output power evenly over the entire take off. Electromagnets need a structure around the projectile to continue propelling it but there is no way to make it that tall.

Re:Space Flight?

[fuzzyfuzzyfungus]

The concept has been advanced; but my understanding is that(beyond the capital costs of building a gigantic magnetic accelerator) there are issues, for most payloads because of the incredible acceleration needed.

A rocket enjoys continuous thrust, so it can be relatively leisurely about reaching escape velocity. A magnetically accelerated pod has only the length of its accelerator track(and, unless you want that track to be very short or very expensive, you are likely launching at an angle other than vertical, thus travelling through more atmosphere to reach orbit). This means that your accelerator pod ends up pulling some hundreds of Gs for a few seconds, which cuts down on the sort of payloads you can launch. Water? sure. Food? some forms. Crew? only if you like meat paste...

Re:Space Flight?

[Nyeerrmm]

Don't forget fuel. The least 'sci-fi' way to really open up the solar system is to use something like railguns to get fuel (and water too) to orbit for cheap, and get the crew and food to orbit using cheap things like the Dragon/Dream Chaser/Orion Lite capsules.

Most of the Saturn V stack was fuel. If we can get a reliable on-orbit refueling infrastructure in place, you could launch a moon landing on a Saturn I and do it easily within the current NASA budget. No heavy lift needed.

Re:Space Flight?

[Albinoman]

If you want a space launch vehicle capable of escape velocity, that's 11,200m/s. The space shuttle is about 3Gs or 9.8*3=29.4m/s^2. It would take just under 6 1/2 minutes at that acceleration and needs a rail over 1,300 miles long! Now the problem is you are pointing at the horizon. No sudden turns at 7mi/s.

Re:Space Flight?

[Nefarious Wheel]

Rockets output power evenly over the entire take off. Electromagnets need a structure around the projectile to continue propelling it but there is no way to make it that tall.

You don't need "tall". You can make do with a straight, horizontal structure tangent to the planetary (or lunar) sphere. You have to punch through more atmosphere (if from the Earth, and let's not talk about noise ordinances), but you can certainly achieve orbit from a horizontal electronic accelleration structure. From the Moon, no-brainer. Less structure, make it longer. As long as it's straight enough at the muzzle you'll get your escape velocity.

Re:Space Flight?

[strack]

the angle of the track is not really a problem. you bore a tunnel straight down, or at a angle, to get the desired angle. this also allows you to have a track a few kilometers long. and you dont rely on the track to provide all the acceleration. the launch assist from such a track would be enough for a practical, reusable, single stage rocket with a reasonable amount of payload.

Re:Space Flight?

[wagnerrp]

A ten kilometer long track at a survivable 4g acceleration gets you to about Mach 8. Discounting air friction all the way up, you've still only got enough energy to make it about a third of the way to orbit. You can't dig down to arbitrary depths for obvious reasons. A shallow launch angle is just going to increase your frictional losses. You can't build a ramp at the end of the track without killing your crew.

Magnetic launch is a nice idea and may work fine for bulk materials that can withstand very high acceleration, but it just doesn't scale for human launches.

Re:Space Flight?

[91degrees]

Now the problem is you are pointing at the horizon.

Just build it perfectly straight and rely on the earth dropping beneath you. You're traveling a decent distance around the earth, so if you start horizontal by my calculations you'll have an 18 degree elevation and a starting altitude of a couple of hundred miles.

Re:Space Flight?

[necro81]

It's been bandied about for a long time. The problem is the energy involved (or, more directly, the velocity). In order for this concept to work, you'd need to accelerate the payload to an orbital velocity (several kilometers per second), at ground level, before it even left the surface. That's roughly Mach 10, something we've never even come close to achieving at anywhere close to sea level. You'd also need to add in a lot of extra velocity, because you'd lose a lot to air friction. Building a hypersonic payload capsule is no easy task.

Then there's the practical concerns of how you'd built the thing. The size of the thing depends greatly on how much acceleration your payload can tolerate. If it were a linear accelerator, it would need to be tens of kilometers long (the last few kilometers would be passed by in about a second!). A circular one would probably need to be at least several kilometers in diameter (so that centripetal acceleration doesn't crush you when your tangential velocity is kilometers per second, increase radius). It'd all need to be superconductive, too. The closest we've ever built to something like that is the LHC, which can impart on a cluster of protons, in a vacuum, at liquid helium temperatures, roughly the equivalent energy of a fast-pitched baseball. The actual acceleration is done based on electrical charge, which makes it pretty easy - the big magnets just steer the beam in a circle. A payload is electrically neutral, so the acceleration would be done magnetically (like this new aircraft catapult), which is frankly more difficult to do.

So, in short,you probably could do it, but it involves enormous technical challenges, a generation or two's worth of R&D, and probably tens if not hundreds of billions of dollars in capital costs. Even then, your payload capacity to LEO may be very small, and it may not be physiologically safe for humans.

What would probably be a better use of technology would be a 747-sized catapult that could gently accelerate (or assist in accelerating) large aircraft down an airport runway up to speeds of, say, 300 km/h.

Re:Space Flight?

[WastedMeat]

you can certainly achieve orbit from a horizontal electronic accelleration structure.

No. Orbits under any inverse square central force are closed. Without a burn to correct the trajectory, the projectile returns to the launcher or the ground that is in the way. Interaction with the atmosphere can't really work, as it would then be passing through the atmosphere every cycle. As soon as it goes ballistic, it is on a closed trajectory if it does not have escape velocity.

Re:Space Flight?

[strack]

the entire first stage of the saturn v rocket got the rocket to about mach 7 before it dropped off. and it was about 2000 of the 3000 tonnes of the fully fuelled saturn v. the point is, any launch assist also gets rid of the weight of fuel you have to accelerate along with the payload, which pretty much squares any benefits in terms of payload and energy expenditure.

Re:Space Flight?

[petermgreen]

The problem then is how do you build a track a couple of hundred miles in the air....

Re:Space Flight?

[91degrees]

Okay, so it's still impractical, but it's impractical for a completely new reason!

Re:Space Flight?

[blair1q]

You're not going to get to orbit on a railgun. You might reach outer space, but you're going to lack angular momentum. You need something to give you that. An oblique shot won't do it. Far more atmosphere to clear that way. And at orbital speeds plus the speed you'll lose to drag, friction heating will vaporize anything you try to use as a shield. If you plan for that and use enough ablative shielding, you've just added huge weight to your vehicle. That weight might as well be a booster rocket. So use a booster rocket and leave the railgun out of it.

Re:Space Flight?

[John Hasler]

I agree that it wouldn't work from Earth but from the Moon it would work fine with a small insertion burn. Might also work from Mars.

Couldn't wedge an "I" in there?

[RyuuzakiTetsuya]

"Dear Gaddafi, I sent you some EMAILS. I hope you get them."

-- President Sarah Palin.

Carrier stumbles over chair, 1000's Embarresed

[Usagi_yo]

USS Gerald R. Ford? You have to be kidding me. What's next. USS Chevy Chase?

Re:Carrier stumbles over chair, 1000's Embarresed

[ilo.v]

USS Gerald R. Ford? You have to be kidding me. What's next. USS Chevy Chase?

They wanted to name one after Bush, but they didn't want it to look bad. Solution: name a different one after Gerald.

Re:Carrier stumbles over chair, 1000's Embarresed

[Anonymous Coward]

Only after someone elects Chevy president.

Re:Carrier stumbles over chair, 1000's Embarresed

[rossdee]

They did name one after Daddy Bush though. (And fair enough because he did fight in WWII in the Navy. Carter got a sub named after him because he was a sub captain.

Re:Carrier stumbles over chair, 1000's Embarresed

[Anonymous Coward]

http://en.wikipedia.org/wiki/USS_George_H.W._Bush

Re:Carrier stumbles over chair, 1000's Embarresed

[DesScorp]

USS Gerald R. Ford? You have to be kidding me. What's next. USS Chevy Chase?

Trust me, many Navy vets (including this one, who served on a carrier) are tired of the Navy naming our biggest capital ships after politicians. Layups like George Washington or Thomas Jefferson, no problem. But Gerald Ford? Really? There's a feeling in the Navy that we should stick to traditional names.... the Essex, the Hornet, the Lexington, etc, for our most prominent ships. But don't look for this practice to end, because appealing to political egos helps grease the Congressional appropriation machine.

Re:Carrier stumbles over chair, 1000's Embarresed

[DesScorp]

They did name one after Daddy Bush though. (And fair enough because he did fight in WWII in the Navy. Carter got a sub named after him because he was a sub captain.

There's a great political cartoon that came out when the Carter was commissioned... "An attack submarine???".

Re:Carrier stumbles over chair, 1000's Embarresed

[LWATCDR]

Carter was never a sub captan. He served on a submarine but was not a commander.
Actually the shouldn't have named the sub after Jimmy Carter or the Carrier after Bush. It is tradition that no Navy ship is named after a living person. It was broken by the Burke class. It was unintentional because it takes so long to design a new ship that the Navy was sure that Burke would have passed on by the time the Burke was launched. He lived to a very ripe old age and mess up tradition.
There is no reason to not name a ship after a President of the US and what most people don't know is that Gerald R. Ford was actually a very good president under considering what he had to work with. He as also a very good and honorable man as politicians go. I don't think you can find a single blemish on his record and historians today say his pardon of Nixon was the right thing to do.

Re:Carrier stumbles over chair, 1000's Embarresed

[Wyatt Earp]

You know that Gerald Ford had a naval career right? He lead a fire control team that saved the escort carrier USS Monterey.

Ford, Carter and George H.W. Bush all had naval careers, both Ford and Bush were on carriers and have carriers named for them, Carter was in the submarine service and has a submarine named for him.

Re:Carrier stumbles over chair, 1000's Embarresed

[Wyatt Earp]

Jimmy Carter left the navy as a Lieutenant, he didn't command a submarine but was part of the nuclear engineering department of USS Seawolf SSN-575

Re:Carrier stumbles over chair, 1000's Embarresed

[ilo.v]

They did name one after Daddy Bush though ... fair enough because he did fight in WWII in the Navy.

My apologies, I assumed everyone would know that, but you are right, we should explain that here.

In the US Navy's defense, they do have a "theme" where many aircraft carriers are named after U.S. Presidents:

USS John F Kennedy
USS Dwight D Eisenhower
USS Thodore Roosevelt
USS Abraham Lincoln
USS George Washington
USS Harry S. Truman
USS Ronald Reagan
USS George H.W. Bush
USS Gerald R. Ford

"Daddy Bush" was indeed a real honest-to-god carrier pilot, and actually did real honest-to-god fighting. He had already been admitted to Yale, with the war time draft deferment to go with it, but joined the Navy instead. He became the Navy's youngest pilot. He was shot down while bombing a Japanese radio tower on Chichi Jima, winning the Distinguished Flying Cross. (His plane was hit and on fire but he finished his bombing run first before bailing out).

My not so funny joke was pointing out that things were going to get a lot less defensible if they continued to follow the calendar and named the next two after Clinton and Baby Bush. (See, ma, bipartisan dissing!)

Re:Carrier stumbles over chair, 1000's Embarresed

[ilo.v]

Oops, missed one:

USS Franklin D. Roosevelt CV 42

Re:Carrier stumbles over chair, 1000's Embarresed

[Col. Klink (retired)]

> Ford was actually a very good president under considering what he had to work with.

Yeah! I mean, unless you consider the fall of Saigon or "Whip It Now" failures...

I'd say his greatest achievement was picking Stevens for the Supreme Court. But that only worked out so well because Stevens utterly betrayed Ford.

Re:Carrier stumbles over chair, 1000's Embarresed

[Anonymous Coward]

Yep, he was the best president to never appear on a presidential ballot.

Re:Carrier stumbles over chair, 1000's Embarresed

[binaryseraph]

Could be worse... Just wait for the USS Jimmy Carter!

Re:Carrier stumbles over chair, 1000's Embarresed

[Mt._Honkey]

The USS Jimmy Carter already exists, as an attack submarine. wikilink

Re:Carrier stumbles over chair, 1000's Embarresed

[Lord_of_the_nerf]

Maybe if they shared similar characteristics to the people they were named for.

I can see the USS Dubya never leaving dock.

Re:Carrier stumbles over chair, 1000's Embarresed

[asylumx]

http://en.wikipedia.org/wiki/USS_Jimmy_Carter_(SSN-23)

Really? Not even a simple google search?

Re:Carrier stumbles over chair, 1000's Embarresed

[binaryseraph]

nope i didn't bother. Honestly didnt think they would do make one after him. how amusing.

Re:Carrier stumbles over chair, 1000's Embarresed

[Wyatt Earp]

The US was out of Vietnam, Congress had stopped funding the South Vietnamese military in the fall of '74, so how exactly is the Fall of Saigon Ford's fault?

Re:Carrier stumbles over chair, 1000's Embarresed

[snakeshands]

Ford at least served on a carrier, the Monterey, during WWII, and was a longtime member of the Defense Appropriations Subcommittee while in the House. Better him than, say, Reagan. Naming things after any recent politicians is noxious, though.

Re:Carrier stumbles over chair, 1000's Embarresed

[Anonymous Coward]

Ford should have been skipped on the basis he was never elected President by the people, or even elected Vice President, oddly enough.

And yes, the tradition should have been reinstated after the exception of Burke. It's bad form, and sycophancy now. Quite agree Ford seemed to be a good and honorable man. Entirely disagreed with him pardoning that bastard Nixon at the time, and quite happy to disagree with historians today. But I don't doubt he saw it as best for the country to put a dignified end to the matter, I just think he was wrong.

Re:Carrier stumbles over chair, 1000's Embarresed

[afidel]

Uh, he was a freaking navy nuclear engineer who went on to be president, of course they named a sub after him.

Re:Carrier stumbles over chair, 1000's Embarresed

[Col. Klink (retired)]

A successful presidency is one in which the President is able to implement his policies. To say "Congress wouldn't do what the President wanted" is the same as saying "the President failed to get Congress to do what he wanted." Surely he would have taken credit for securing more funding had Congress approved it.

Re:Carrier stumbles over chair, 1000's Embarresed

[LWATCDR]

You disagree but yet you must admit that he did it because he honestly thought that it was the best for the country. Think how rarely we can say that about our elected officials today.

Re:Carrier stumbles over chair, 1000's Embarresed

[tophermeyer]

There's a deeper theme with this list (incl. USS Franklin D. Roosevelt CV 42 that you mention in your follow up).

Almost all of those guys saw Military service, with the exception of FDR (but given that little dustup that he Presided over I doubt anyone would hold that against him). And if memory serves all of them saw combat action, with the exception of Reagan (who was nearsighted and was ineligible for foreign service during WWII). Most of them served with distinction (i.e. Kennedy's PT boat disaster, Teddy Roosevelt's cavalry, G.H.W. Bush's pilotry, and Washington winning America).

The weak point of my thinking here is Reagan, who did volunteer but requested transfer to a stateside film/propaganda unit pretty quickly. The rest of these guys are definitely Military men. Doesn't surprise me that they would have carriers named after them.

Re:Carrier stumbles over chair, 1000's Embarresed

[jollyreaper]

You disagree but yet you must admit that he did it because he honestly thought that it was the best for the country. Think how rarely we can say that about our elected officials today.

It removed the consequences from bad governance. You can commit any crime you want and you'll get pardoned. That's bad for business. We didn't go after the Nixon criminals and they came right back in the Dubya administration. We didn't go after the Dubya criminals and they'll come back in the next Republican administration.

Re:Carrier stumbles over chair, 1000's Embarresed

[ThatsNotFunny]

Gerald Ford was not just a politician. He was a Lt. Commander in the Navy during WWII, earning several awards and medals for his service: http://en.wikipedia.org/wiki/Gerald_Ford#Naval_service_in_World_War_II

Re:Carrier stumbles over chair, 1000's Embarresed

[Anonymous Coward]

USS Gerald R. Ford? You have to be kidding me. What's next. USS Chevy Chase?

Trust me, many Navy vets (including this one, who served on a carrier) are tired of the Navy naming our biggest capital ships after politicians. Layups like George Washington or Thomas Jefferson, no problem. But Gerald Ford? Really? There's a feeling in the Navy that we should stick to traditional names.... the Essex, the Hornet, the Lexington, etc, for our most prominent ships. But don't look for this practice to end, because appealing to political egos helps grease the Congressional appropriation machine.

It wouldn't be so bad if (a) names were only used only post humusly, and (b) it was at least fifty years after their death.

This way at least some of the politics related to their name would hopefully be removed / reduced.

Re:Carrier stumbles over chair, 1000's Embarresed

[Anonymous Coward]

Nixon broke the law for political gains, as president. That's outrageous. BS to your "historians". Learn some grammar too.

Re:Carrier stumbles over chair, 1000's Embarresed

[Anonymous Coward]

Actually, the naming convention was broken by the naming of CVN-70 USS Carl Vinson.

http://en.wikipedia.org/wiki/Carl_Vinson

Re:Carrier stumbles over chair, 1000's Embarresed

[ruthless reader]

Are you high!!! The next ones gonna be USS Animal house

Re:Carrier stumbles over chair, 1000's Embarresed

[Anonymous Coward]

Sorry, I agree with those that say we should stop naming ships, buildings, installations etc. after politicians. I would like to see a return to naming them after ideals and absent that we should name them after those who have lost their lives in the service of their country. Start with the Medal of Honor winners and work down. Unfortunately we won't run out of names.

Re:Carrier stumbles over chair, 1000's Embarresed

[Anonymous Coward]

Yeah, because if there's one thing the military needs, it's to grease wheels to get more money.

What, more money in a year than most countries isn't enough for you?

Re:Carrier stumbles over chair, 1000's Embarresed

[jafac]

Well, Ford wasn't so terribly bad.
You name one after Clinton, or Carter, and (not that I think they were bad presidents) - you'd have a problem, in the Military. Name one after freaking Nixon - man that'd be a joke.

But they've got a GHW Bush, coming up, and a carrier; Reagan (not bad, for a senile sock-puppet, who was supposed to take a bullet and go down like a man; so the grown-ups could get some work done). But I guess there are plans for a GW Bush. And given the whole torture, and fake war, and no WMD, and failure to actually find OBL. . . that's just kind of sad. I mean, I know he was responsible for more profit for the manufacturer than any other president in history, but, I think a lot of ppl are going to feel pretty uncomfortable serving on a ship named after "Miserable Failure".

Re:Carrier stumbles over chair, 1000's Embarresed

[Anonymous Coward]

I think it is fine that they name ships after presidents who have served in the military with distinction as is true of Ford, Carter and Bush I. Presidents whose service is not terribly distinguished should not get any recognition, nor any strictly civilian Presidents (sorry Presidents Clinton and Obama).

Re:Carrier stumbles over chair, 1000's Embarresed

[hax4bux]

I'll add my 3 hashmarks to that.

Elcromagnetic

[Anonymous Coward]

But how does it work?

Re:Elcromagnetic

[Anonymous Coward]

I don't know. The scientific personnel were upsetting me.

But why have a catapult at all?

[__aagctu1952]

What I'm curious about is why they're using catapults at all - the Russians and the Brits, for example, use a "ski jump" instead. And I read somewhere (unfortunately, I can't remember where - damn you, source blindness!) that that approach is actually better, in terms of aircraft launch rate, as you don't have a complex catapult system that has to be reset for every plane.

So... why are US carriers using catapults, when they seem to me to be just another point of failure? Can someone enlighten me?

Re:But why have a catapult at all?

[Spy Handler]

because US Navy needs to launch large aircraft with significant payload (unlike the brits or russians)

Re:But why have a catapult at all?

[Anonymous Coward]

Only special airplanes can take off using a ski jump. The airplane must be built for short takeoff, which forces compromises elsewhere. The jump itself doesnt give the plane any airspeed at all, it just helps give it an upward vector. With a catapult you can launch a wide variety of more conventional airplanes because the catapult gives them the airspeed needed for flight.

Re:But why have a catapult at all?

[icegreentea]

The maximun launch weight on pure ski-jump systems are much much lower than catapult launches. The old British carriers for example were stuck launching Sea Harriers which had a max take off weight of 12000kg. The F-18 (the original one... they've all been replaced by heavier planes) had an EMPTY weight just 1000kg less than that. It's max take off weight from a US Carrier was almost over twice that of the Sea Harrier.

The new British carriers (suppose to launch Eurofighter variant) will also have a catapult.

The catapult is another point of failure. That's one reason there's 4 on a ship. And that's reason why US had an advantage. They had an unbroken string of experience designing, building, and maintaining catapult systems since the end of WW2.

Re:But why have a catapult at all?

[Anonymous Coward]

US Carrier aircraft tend to be heavier than most other currently operating naval aircraft. CATOBAR (catapult launch and arrested recovery) allows that, while ski jumps or vertical takeoff, which is the alternative, does not. This allows Navy carrier aircraft to perform about as well as land based planes, which things like a harrier do not. Don't expect to see something like an F-18 with a significant number of bombs or a lot of fuel take off from a ski jump- it can't do it. I would expect that whatever the Russians are flying off of their carriers has either a short range or a very light payload. The advantages of the CATOBAR aircraft are significant enough that the Royal Navy is going to build two carriers with catapults in the near future so they can operate them.

Re:But why have a catapult at all?

[LWATCDR]

Yes because cats are a better solution.
You can launch heavier aircraft with a cat than with a ski jump. The Russians and UK can not operate aircraft like the E-2. Also the UK is going to put cats on their latest carrier because the F-35b may fail.
Also a Ski jump can not launch while the carrier as at a stop which can be useful.

So yes the sky jump has one benefit but a lot of drawbacks. The Russians used them because it was a low risk for their first real carrier. The brits used them because they only had the Harrier. It did work very well for the Harrier but the Harrier was not as good of a fighter as the F-14 or F-18. It also was not as good of an attack aircraft as the F-18, A-6, or A-7. But it was better than nothing.

Re:But why have a catapult at all?

[jklovanc]

Where fighter and bombers get all the glory there are a few equally important heavy aircraft that need catapults to launch:

AEW:
Aircraft such as the the E-2 Hawkeye http://en.wikipedia.org/wiki/Northrop_Grumman_E-2_Hawkeye are critical to hiding the location of the fleet. If the enemy sees a ship based radar they know where the ship and usually the fleet is. If they see an airborne radar the fleet could be very far away. Also airborne radar can see further.

COD;
Carier Onboad Delivery, Need those critical parts or personel delivered outside of helicopter range? Need to evacuate critically injured personnel? You need a long range aircraft to do it.

Tankers;
Need to extend range to a target? Need to loiter for long periods on CAP. Need a sip of fuel to get back to the carrier because you used to much afterburners in the fight? Tankers are your friend. This role is currently done in the US Navy by the F/A-18E/F http://en.wikipedia.org/wiki/F/A-18E/F_Super_Hornet#Tanker_role

Without catapults none of these aircraft would get off the deck.

Re:But why have a catapult at all?

[afidel]

The Brits converted their F-35B order to F-35C's in October.

Re:But why have a catapult at all?

[Wyatt Earp]

The Royal Navy carrier(s) will operate the F-35C, at least thats the plan.

Theres no naval version of Typhoon planned, I suppose if F-35 continues to have development problems, the Royal navy could go to F-18 E/F or Dassault Rafale, the only other western carrier based strike fighters in production.

Right now there are only two naval strike fighters in production, Super Hornet, Rafale with three in the near future, F-35C, MiG-29K and Su-33. But the Russians are up in the air on if they are getting the MiG-29K or Su-33 to replace the Su-27K

Re:But why have a catapult at all?

[Viol8]

I think you'll find the harrier was a damn site better fighter and ground attack aircraft than your giving it credit for. Theres a reason the US Marines still use them.

Re:But why have a catapult at all?

[mikael_j]

Well, there's always the Sea Gripen project, and BAE used to be involved in the development of Gripen so it could probably be pitched as a "british" fighter to the british people.

Re:But why have a catapult at all?

[LWATCDR]

They use them for one reason. VSTOL. They can take off and land from LHDs. The Harrier has a shorter range and smaller load than the F-18 and much lower performance.
It also had higher loss rate than any other aircraft during the Persian Gulf wars.
The reason they did so well in the Falklands was because the Mirages were at the limit of their range so couldn't use their afterburners much in combat and the US sold the UK the AIM-9L while the Argentines used old AIM-9s. The Lima could lock on from the front while the older Sidewinders where only tail chase.
The Harrier was not and is not a bad plane. It is the best plane you can have if you do have a real runway or a real carrier. Which is real handy. But why do you think that the Brits are building a real carrier.

Re:But why have a catapult at all?

[LWATCDR]

You left out that even when dealing with attack and fighters having a CAT means more fuel and weapons which is real handy sometimes. Nothing ruins a fighter jocks day more then being low of fuel and weapons with bad guys around.

Re:But why have a catapult at all?

[jgtg32a]

I thought that the Marines were always considered and took credit for being more badass because they had old and second rate equipment?

Re:But why have a catapult at all?

[John Hasler]

> Theres a reason the US Marines still use them.

Yes. Because they plan to operate out of short fields.

Re:But why have a catapult at all?

[demonbug]

Where fighter and bombers get all the glory there are a few equally important heavy aircraft that need catapults to launch:

AEW:
Aircraft such as the the E-2 Hawkeye http://en.wikipedia.org/wiki/Northrop_Grumman_E-2_Hawkeye are critical to hiding the location of the fleet. If the enemy sees a ship based radar they know where the ship and usually the fleet is. If they see an airborne radar the fleet could be very far away. Also airborne radar can see further.

COD;
Carier Onboad Delivery, Need those critical parts or personel delivered outside of helicopter range? Need to evacuate critically injured personnel? You need a long range aircraft to do it.

Tankers;
Need to extend range to a target? Need to loiter for long periods on CAP. Need a sip of fuel to get back to the carrier because you used to much afterburners in the fight? Tankers are your friend. This role is currently done in the US Navy by the F/A-18E/F http://en.wikipedia.org/wiki/F/A-18E/F_Super_Hornet#Tanker_role

Without catapults none of these aircraft would get off the deck.

All true; however, assuming Wikipedia is correct, the F/A-18 Super Hornet actually appears to be the heaviest carrier-based aircraft currently operational at about 30 metric tons (max takeoff). The F-14 was heavier at ~ 34 tons, and the F-35C will be about 32 tons. The E-2C (and C-2) max out at around 25 metric tons (the S-3 Viking, also out of service, was about the same weight); I'm not aware of any other large aircraft that operate off of carriers. The heaviest ever that I can find was the F-111B at about 40 tons, but only 7 of those were built and they never entered service (only flight testing from carriers).

Re:But why have a catapult at all?

[myth24601]

The F-18 (the original one... they've all been replaced by heavier planes) had an EMPTY weight just 1000kg less than that. It's max take off weight from a US Carrier was almost over twice that of the Sea Harrier.

The USA still uses the original F-18 Hornet in many Carrier squadrons (about half are upgraded to Super Hornets and many of those were either replacing A-6 Intruders or F-14 Tomcats).

The new British carriers (suppose to launch Eurofighter variant) will also have a catapult.

Originally they were going to stick with STOVL on the new carrier(probably only one will be built) using the STOVL F-35B Joint Strike Fighter but the recent decision to go with CATOBAR and non-STOVL F-35C also opens up the possibility to use a Navalized Eurofighter as well as E-3 AEW.

Re:But why have a catapult at all?

[modecx]

Hell, I know that some pilots preformed a successful landing and take-off off with a Marine Corps C-130 from the deck of a carrier. Those things weigh 76,000 lbs empty! No way that's going to work with a ramp. It's conceivable that a full-up KC-130 could be serviceable from a carrier with JATO and catapult assist. Not that it's likely this will ever be common practice, but it could be handy.

Steam Power for the Win

[gnapster]

I am immensely tickled to hear that steam power is still being used in some modern context, even if I only learn of it as it is being phased out. I had never realized that this was how aircraft carrier slingshots worked. Are there any other interesting uses of steam power these days, outside of electricity production?

Re:Steam Power for the Win

[Kral_Blbec]

Its the bread and butter of hospital sterilization, but i dont know how interesting that is.

Re:Steam Power for the Win

[Timothy Brownawell]

Steam turbines are basically the way to turn an external heat source into mechanical energy. Typically this is just used to generate electricity since it's so much more convenient to work with, but for a few applications the turbine will be attached directly to something other than a generator (say, a propeller on a big boat). Steam can also be used even more directly; as a heat source / heat transfer mechanism (say, for heating groups buildings particularly in colder climates), for cleaning carpets, for sterilizing things, in industrial chemical processes, apparently as a replacement for liquid water in some kinds of modern clothes-washing machines, ... .

Re:Steam Power for the Win

[Anonymous Coward]

I am immensely tickled to hear that steam power is still being used in some modern context, even if I only learn of it as it is being phased out. I had never realized that this was how aircraft carrier slingshots worked. Are there any other interesting uses of steam power these days, outside of electricity production?

You might be interested in this website: http://www.reliablesteam.com/

Basically just hobbyists, but I was surprised to learn that there is still an active community of people building steam engines, and using them on boats.

Sure whatever

[Anonymous Coward]

This is mega old news. I'm sure I did exactly this in Roller Coaster Tycoon.

Of course, those carts full of people didn't fly quite as well as I'd expect a proper fighter jet would.

The USS Gerald R. Ford was sunk today

[riker1384]

The aircraft carrier Gerald Ford was sunk today, and eaten by a pack of senseless sea-wolves. It was delicious.

is it 13 g's or are my calculations off?

[Anonymous Coward]

I haven't done this in decades but here's the calculations as best as I can remember. Ahhh physics in customary units and fractions, enjoy:

vi = 0
vf = 240 mph = 352 ft/s
dx = 300 ft

dv = vf - vi

dt = dx / dv
dt = ( 300 ft ) / ( 352 ft/s )
dt = 75/88 seconds

a = dv / dt
a = ( 352 ft/s ) / ( 75/88 s )
a = ( 30976 / 75 ft/s^2 )

approximately 413 ft/s^2 or about 13 G's

Re:is it 13 g's or are my calculations off?

[GreenTom]

I think you're off by a factor of 2: dt = dx / (average V). Since it goes from 0 to 352 ft/s, v-bar is 176 ft/s, and dt is 75/44 sec.

Anyone been to Cedar Point?

[GreenTom]

The amusement park in Ohio? They've got a roller coaster that uses the same technology to launch, and it's pretty incredable. There are also a few rides in other parks that use liner induction motros to basically fling you straight up...I havent had a chance to ride those, but I imagine that's about as close most of us will get to a carrier fighter launch. Riding Maverick is what made me realize that being a figher pilot must be kind of like trying to use a computer while riding a roller coaster.

Re:Anyone been to Cedar Point?

[NekSnappa]

Actually it's more like taking a physics exam, programming you GPS, and talking on the phone. All while driving a Formula 1 car.
And since we're talking about carrier based planes here. Imagine that you stop the car by catching the axels on a cable while going full speed.

Quake

[timestride]

But can it be used for headshots?

Oh please, gundams have been using them for years.

[BobSixtyFour]

Old news, time to join us in the Cosmic Era/Universal Century time standards :)

Fighters - Railguns

[LongearedBat]

Fighters of the future...
We use railguns to shoot them up.
We use railguns to shoot them down.

Electromagnets?!

[Anonymous Coward]

How the hell do they work?!

Re:Electromagnets?!

[Ungrounded Lightning]

How the hell do they work?!

Like an electric motor that's been unwrapped, flattened, and repeated over and over along a straight track. The stator coils are in the track and the "rotor" is the catapult runner.

Think of the new building program

[Anonymous Coward]

The navy will be hyping the need for new midget carriers. Shorter, flat (read stealthy), stouter to accommodate existing plane loads. Maybe even with ethenol based fuel or solar sails to power molten salt batteries.

Get Ready for a budget increase. I wonder though, to save money will be build them in Hong Kong?

Biri biri

[identity0]

With all this talk of railguns, vectors and accelerators, I am dissapointed that no one has posted Mikoto Misaka.

http://www.youtube.com/watch?v=Iv2v6WpuUG0

Is no one here a Raildex fan?

Drones are more fragile?

[G3ckoG33k]

Drones are more fragile? I thought they should be more robust as there are no humans in them.

But, of course, if they are built essentially as a glider with a mini engine it may well be the case.

Re:Drones are more fragile?

[JaredOfEuropa]

I should think a drone can be launched at a similar or greater accelleration than that of a manned aircraft launching off a carrier. But the steam catapult probably does not provide a fixed amount of accelleration, but a fixed amount of force. Apply this force to a small, light drone, and I think you'll be picking up small pieces of your expensive toy off the flight deck.

Re:Drones are more fragile?

[John Hasler]

> Drones are more fragile?

I think that they may have in mind drones (and other aircraft) that, unlike Navy fighters, were not designed to withstand catapult launching.

Steam catapults can be fun

[serutan]

I used to work with an old guy whose job was to run the catapult on a carrier during the Korean War. He had some good stories about stuff they launched off the deck to "test" the catapult. The best one was an aircraft tractor that had been wrecked during a drag race below decks. Boredom and sailors don't mix.

I love it, but the excess steam made it look...

[drewmister]

more exciting.

We should name them after AWESOME people instead

[Anonymous Coward]

USS Chuck Norris

no burner

[Spy Handler]

from the video it looks like the F18 wasn't even on afterburner and it got airborne as soon as it came off the catapult xD

Re:no burner

[aztec1430]

When are they going to install them at fighter bases? no need for 4 mile long runways for takeoff... just launch straight from the hanger!

Re:no burner

[Anonymous Coward]

Unless the aircraft is heavily loaded, it is standard (at least it was 20 years ago) for the F-18s to carrier launch without afterburners, first of the afterburner equipped aircraft to do so.

Re:no burner

[ErikZ]

Actually, that's a good idea.

You'd save a lot of fuel that's used during takeoff.

I think that commercial airports should get this technology also.

Re:no burner

[aztec1430]

Also - make a 4 mile long version - going up the side of a mountain... - strap a shuttle to it... at the end of the 4 miles it's doing Mach 6...

superman?

[Anonymous Coward]

hasn't the superman ride in some amusement park used this launch method for years now? And why do we need to call it a rail gun?

the mind plays tricks

[Anonymous Coward]

on first scan i thought the headline read "Navy Uses Religion to Launch Fighter Jets"

Re:the mind plays tricks

[Anonymous Coward]

"Navy Uses Religion to Launch Jedi Fighters."

It's not a railgun; it's a linear motor

[karlandtanya]

I would expect a typical steam catapult to be WAY more reliable and maintainable than a linear motor.

I worked with a couple of them in an auto plant over a decade ago. Its job was to shuffle 3 tooling skids around among 3 robot station and one operator load station.

The design needed linear motors so the skids could travel uncoupled. The sequence of motion would have wound up any permanently attached cords or linkages in about 1/2 cycle.

The tools were clearly labeled with official signage as "TFH North" and "TFH South". It was only after working there for several months that I actually heard their real name.

"TFH" stood for "Tool from Hell". They were replaced with a different design next time I worked in that plant.

It's a neat trick and if they can get some benefit out if it, maybe it can be useful.

Good Luck with that

[Anarke_Incarnate]

I have family that works in this very exact field (For the Navy on the aircraft launch systems). This thing MAY work at some point, but boy is it not ready for prime time.

It's more than just the weather

[sean.peters]

Steam systems are a nightmare to maintain in any weather conditions - switching from steam to electricity has been an ongoing process in the Navy for decades. The old Charles Adams class DDGs had all-steam propulsion plants - meaning that every oil pump, fuel pump, and every other system ran on some kind of steam. Those guys spent their lives maintaining steam turbines. As time has gone by, the Navy has gotten away from steam in a big way for exactly that reason - all that steam technology required a lot of sailors to keep running, and sailors are expensive. For what it's worth, I'm qualified as a Navy Engineering Officer of the Watch (EOOW) in 1200 lb steam, so I have some considerable personal experience with this.

I also think that you're likely to get performance improvements from EMALS. So I really doubt that this move has much to do with an anticipated Arctic war - there are big advantages to moving away from steam in any weather conditions.

Re:It's more than just the weather

[drinkypoo]

It seems to me that the only thing worse than having to replace steam turbines all the time is to unmount an axle and replace a bearing all the time.

Re:It's more than just the weather

[sean.peters]

A couple things: 1) you didn't "replace" steam turbines - you reconditioned them. They're too expensive to just toss. And the reconditioning process was pretty labor intensive. 2) You had to do the maintenance a lot more often for the steam turbines. They were constantly developing little steam leaks, for example.

I spent a number of years in the engineering plant of various steam ships, and believe me, the steam equipment was way, way more trouble than the electric equipment.

Re:It's more than just the weather

[drinkypoo]

I meant the turbine itself, you can only regrind it so far before it is out of spec and you have to recycle it, right?

Re:It's more than just the weather

[NSN A392-99-964-5927]

Steam systems are a nightmare to maintain in any weather conditions - switching from steam to electricity has been an ongoing process in the Navy for decades. The old Charles Adams class DDGs had all-steam propulsion plants - meaning that every oil pump, fuel pump, and every other system ran on some kind of steam. Those guys spent their lives maintaining steam turbines. As time has gone by, the Navy has gotten away from steam in a big way for exactly that reason - all that steam technology required a lot of sailors to keep running, and sailors are expensive. For what it's worth, I'm qualified as a Navy Engineering Officer of the Watch (EOOW) in 1200 lb steam, so I have some considerable personal experience with this.

I also think that you're likely to get performance improvements from EMALS. So I really doubt that this move has much to do with an anticipated Arctic war - there are big advantages to moving away from steam in any weather conditions.

I am an ex Marine Commando/ SFSG/ FP (Special Forces Support Group/Fleet Protection) and have spent time on many british warships including HMS Ocean/illustrious etc. Although this is a good idea, I cannot help but see a high failure rate in the Arctic and the Salt Water monkeying with launch control. "Cables on Launch" and steam work. Sorry but I have to laugh, how many pilots will get dumped in the Ocean "cough" "splutter" like a Car that is back-firing and will not start properly in cold weather.

Steam works, besides the pistons and hydraulics get planes and copters up on the flight deck at ultra speed. I can just see this failing. Sorry I am a traditionalist and sticks with what works.

The advantage: maintenance

[sean.peters]

Electrical machinery is about a million times cheaper and easier to maintain than steam machinery. Steam catapults suck up a ton of manhours in maintenance every year, and the Navy would really like not to have to keep doing that.

On USS JIMMY CARTER

[sean.peters]

Not to mention the fact that it continued the practice of totally fouling up the naming conventions for ships. The Seawolf class was the poster child for this: you had USS SEAWOLF, USS CONNECTICUT, and USS JIMMY CARTER. Back in the day, submarines were named for fish. Then it was discovered that fish didn't vote, so they started naming submarines after constituencies: SSNs were named after cities, SSBNs after states. The Seawolf class blew that out of the water (so to speak).

Re:On USS JIMMY CARTER

[Doctor Faustus]

Then it was discovered that fish didn't vote, so they started naming submarines after constituencies: SSNs were named after cities, SSBNs after states

They want to name important ships after cities and states, and they aren't making heavy cruisers and battleships anymore.

Of course, their engines are still steam

[sean.peters]

The rest of the Navy has moved from steam turbines to gas turbines or diesel engines, but a steam generating system is still the most straightforward way to turn a hot nuclear fuel rods into forward motion. So steam is still being used for aircraft carriers in that sense.

Probably won't use railguns to shoot them down

[sean.peters]

Railgun projectiles are not really going to be able to maneuver in flight, so they're not so good for engaging aircraft. Railguns best use is probably in engaging land targets. For the immediate future missiles are going to continue as the anti-air weapon of choice, and further on, laser weapons will do the job.

Re:Probably won't use railguns to shoot them down

[Anonymous Coward]

Guided AA shells have been available for naval guns since at least the 1980s, and (as far as I know) come in sizes down to 3" or so.

Summary is wrong - should be 240km/h.

[drerwk]

Good. Now, noticing that 6.3g is too much for the pilot, someone should figure out that the article has 240mph, when it should say 240km/h. So, it is closer to 3g. This pdf has quite a bit more info. http://www.edn.com/contents/images/207108.pdf

Re:Summary is wrong - should be 240km/h.

[OneAhead]

What makes you think that 6.3 g is too much? Sustaining 6.3 g for 1.75 seconds along the vertical axis is well within the capabilities expected from a fighter pilot. Moreover, the acceleration when catapult-launching a plane is along the horizontal axis which is much better tolerated. Untrained humans are able to tolerate 17 g eyeballs-in for several minutes without loss of consciousness or apparent long-term harm.
http://en.wikipedia.org/wiki/High-G_training

That said, you are right about the 240mph actually being 240km/h. From the pdf file: "The complete EMALS system will use a 300-ft long LIM to accelerate a 100,000-lb (45,000-kg) aircraft to more than 130 knots (67m/sec) and lighter aircraft to 200 knots (100m/sec)". 130 knots is almost exactly 140km/h. However, 45 metric tons is about twice the weight of a typical fighter plane, and I believe the stall speed of jet fighters is significantly higher than 240km/h, especially when loaded. Therefore, it seems reasonable to assume that the 200knots (130mpg or 370km/h) is for fighter planes, which would correspond to an acceleration of roughly 6 g.

Re:Summary is wrong - should be 240km/h.

[drerwk]

I might buy 6g as possible for a pilot on launch. But I am near certain that 130 kts would fly any carrier based loaded fighter.

Re:Summary is wrong - should be 240km/h.

[demonbug]

What makes you think that 6.3 g is too much? Sustaining 6.3 g for 1.75 seconds along the vertical axis is well within the capabilities expected from a fighter pilot. Moreover, the acceleration when catapult-launching a plane is along the horizontal axis which is much better tolerated. Untrained humans are able to tolerate 17 g eyeballs-in for several minutes without loss of consciousness or apparent long-term harm.

http://en.wikipedia.org/wiki/High-G_training

That said, you are right about the 240mph actually being 240km/h. From the pdf file: "The complete EMALS system will use a 300-ft long LIM to accelerate a 100,000-lb (45,000-kg) aircraft to more than 130 knots (67m/sec) and lighter aircraft to 200 knots (100m/sec)". 130 knots is almost exactly 140km/h. However, 45 metric tons is about twice the weight of a typical fighter plane, and I believe the stall speed of jet fighters is significantly higher than 240km/h, especially when loaded. Therefore, it seems reasonable to assume that the 200knots (130mpg or 370km/h) is for fighter planes, which would correspond to an acceleration of roughly 6 g.

Also remember, during the majority of launch operations carriers are moving. So, that 130 knots from the catapult is added to the speed of the carrier (not sure if they go full speed during launch operations; assume 20 kts or so to be safe) giving 150 knots. Launch operations are almost always conducted into the wind, so that provides another few knots air speed for free. Basically, even before catapult launch an aircraft might have an airspeed of 20 or 30 knots just sitting on the deck.

The F/A-18 Super Hornet actually has some pretty advanced systems for increasing low-speed lift at the cost of increased drag (they aren't really designed for clean, top speed) which as a helpful byproduct decreases stall speed. I wouldn't be surprised if the stall speed even fully loaded is in the 130 knot range, although obviously you want to be going faster than that to provide some cushion. Fully loaded you're looking at about 31-32 metric tons fully loaded, so they aren't real light, but likely they can be launched significantly faster than 130 kts.

On a side note, looking at naval aircraft on Wikipedia it looks like there isn't really anything operational heavier than the Super Hornets - the heaviest I see is the F-14 at about 34 metric tons max takeoff (now out of service); I thought the E-2C or S-3 (the latter now also out of service) would be heavier, but they only come in around 25 tons. So right now there really doesn't seem to be any aircraft heavier than the Super Hornet landing and taking off from carriers (the F-35C will be slightly heavier), so saying these fighters are the "light" aircraft mentioned doesn't really make sense.

Re:Summary is wrong - should be 240km/h.

[OneAhead]

Actually, I submitted the wrong wikipedia link there:
http://en.wikipedia.org/wiki/G_force#Horizontal_axis_g-force
Again, 6g along the horizontal axis is not a problem for the pilot. Don't know about the equipment...

And I also made a typo in the speeds: 130 knots is almost exactly 240km/h.

Question for you military types

[PPalmgren]

Would this system fail in an EMP situation? For the record, I have no idea if the steam-powered one would have the same problem. It seems like if an EMP were to hit your carrier, it'd most certainly be the most important time for you to be capable of launching. I could see shielding protecting the power generation equipment in either system, but see difficulty in shielding the actual launch system for this setup.

Re:Question for you military types

[John Hasler]

EMP is no hazard to elctrical machinery and high power electronics (besides, it'll all be inside the steel ship). It damages low power systems such as controls and computers and is particularly dangerous to radio and radar systems since they must connect to unshielded antennas and handle weak signals.

If you get hit by an EMP pulse big enough to damage switching devices capable of handling 135MW your decks will be melting.

Re:Question for you military types

[demonbug]

EMP is no hazard to elctrical machinery and high power electronics (besides, it'll all be inside the steel ship). It damages low power systems such as controls and computers and is particularly dangerous to radio and radar systems since they must connect to unshielded antennas and handle weak signals.

If you get hit by an EMP pulse big enough to damage switching devices capable of handling 135MW your decks will be melting.

That, and I'm not sure I'd trust my aircraft's avionics after such a hit...

Re:Question for you military types

[Caerdwyn]

In 1976, pilot Viktor Belenko defected from the USSR, and flew his MiG-25 to Japan. The US and its allies had never had a chance to examine the MiG-25, having only seen it from a distance at airshows and tracked it at insanely high speeds by radar, so this was a golden opportunity. Just how had the Soviets manage to build a Mach 3+ interceptor?

Not exotic materials. To our surprise, the airframe was made of nickel-alloy stainless steel. Its speed capability was simply because it had a freakin' huge pair of engines... and those engines would be damaged by a full-speed run. You could do Mach 3 ONCE... then you had to overhaul the engines. But as an interceptor designed not for dogfighting but for shooting down bombers bearing nuclear weapons, you don't care about repeat missions; its job was to get out there and dump a load of air-to-air missiles. *

The biggest surprise was the radar. 600 kilowatts. Yeah, sure, try to jam a 600Kw radar. Not gonna happen. (For comparison, the radar in an F15, which itself was a response to the MiG-25, is about 15Kw) And even more amazing... it was not solid state. It was a TUBE radar! Those stupid backwards Soviets with their stone knives and bearskins! But wait... tubes are not vulnerable to EMP. This taught us that a lynchpin of Soviet defense against incoming US bombers would be to pop nukes about 100km up along its borders when incoming bombers were detected... to fry the sophisticated American avionics the American bombers relied upon... then shoot down any now-crippled aircraft with Mach 3 missile-platforms.

Upon realizing this, a massive program of EMP-hardening of military avionics and other control systems was undertaken.

A fascinating story, the moreso because it's true.

* (The USSR thought they needed an aircraft with this speed because of the XB-70, which was a US bomber capable of Mach 2+. We never put the XB-70 into regular production, but the USSR had to plan for "what if the US actually did make B-70's?", and the MiG-25 was a mighty expensive response. The USSR was matching US military spending pretty much on a dollar-for-dollar basis with a much smaller economy. Goading the enemy into economic ruin through unsustainable defense spending ultimately brought down the Berlin Wall, and as I understand it has modern applications too... amazing how huge an economic lever a shoe-bomb or exploding panties can be, yes?)

Re:Question for you military types

[ErikZ]

An EMP situation?

You mean, after being hit by a Nuke, would they have trouble launching airplanes?

Yes. Yes they would.

Sill using break away bolt?

[Drethon]

I find it interesting they still use break away bolts. This was done for steam catapults because it takes a fraction of a second for the steam valves to fully open and reach full pressure. I would have though an electrical launch system wouldn't have this deficiency. Are the bolts there for legacy purposes or does it still take a fraction for an electrical launcher to reach full force?

Re:Sill using break away bolt?

[John Hasler]

You wouldn't want the motor core and its attached forty tons or so of aircraft shifting around due to the wind or the maneuvering of the ship. With the armature unenergized reluctance might not hold it.

Re:Sill using break away bolt?

[yurtinus]

Could be wrong here, but I believe the breakaway bolt also holds against the power from the aircraft thrust so that when the catapult launches the aircraft is already under power.

Re:Sill using break away bolt?

[Drethon]

You are correct, I had forgotten about that portion which makes sense for this launch method too as it still takes time for a jet engine to spool up...

Perhaps Zebra

[PSaltyDS]

'DZ' may be a broken reference to "Zebra Fittings", meaning valves that must be shut in every compartment when the ship goes to material condition Zebra (as for General Quarters or Battle Stations). Electrical systems are controlled at a central switchboard, but at every point where a steam line crosses a water-tight bulkhead, there will be additional valves that can be secured to isolate that space for damage control purposes. Those valves bring additional maintenance themselves.

The 'D' means that fitting would be secured for Darken Ship also, which would be odd for a steam valve. An external door would be marked 'DZ', or "Dog Zebra", because you would secure it for either condition Zebra or for Darken Ship.

Or even more likely, 'DC'

[PSaltyDS]

On re-reading the grandparent post, it seems even more likely it was just a typo of 'DC' for Damage Control. I say that because it wasn't referring to actual steam lines, but rather drains.

Some auxiliary steam lines might be zebra fittings and secured for General Quarters, but steam to primary mission systems like the catapults on a carrier would only be secured if actually damaged, not as a precaution. Most drains however are secured for condition zebra.

So it was more like "...steam lines, leading to condensation, requiring additional drains... and the additional DC valves to go with them."

HERE I AM!

[Caerdwyn]

I would worry that the operation of a magnetic catapult (or, for that matter, railgun artillery) would send out a huge, unmaskable burst of radio noise that announces to the world "Here I am! Railgun here! Come and blow me up!". I'm quite sure that the designers have this in mind; I'm not so sure that something can be done about it. It may, of course, be a situation of "sure, you know where our carrier is, so just what do you think you're going to do about it?" Any enemy capable of harming an aircraft carrier is likely to have the capability to know just where they are anyway... it's not like you can hide a quarter-mile-long hunk of metal from a satellite with look-down radar or IR capability. The cat-and-mouse naval battles like Midway are a thing of the past. That being said, I'm sure there's a carrier captain or two out there that would really prefer these things be shieldable.

Field artillery pieces are another matter. Revealing their location is an invitation to disaster. I suspect that generating enough energy to rapidly, repeatedly fire a tank-mountable gun is going to take more of a power supply than can be carried on a tank chassis, so the point may be moot, and rail guns will be either "Big Berthas" or ship-mounted only.

Re:HERE I AM!

[John Hasler]

I would worry that the operation of a magnetic catapult (or, for that matter, railgun artillery) would send out a huge, unmaskable burst of radio noise that announces to the world "Here I am! Railgun here! Come and blow me up!".

The machine operates at relatively low frequencies inside the steel hull. I don't think it will be a serious problem.

I'm definately going to have to find a jerkmeter.

[orichter]

After reading your article, I've decided I'm going to have to see if I can find myself a jerkmeter. If I read the article correctly, you could find someone you think is a jerk, crack them over the head with it and say, "See how big a jerk you are." Of course then I'd probably have to do the same to myself.

Somewhat off topic, but

[mr_bubb]

From "Enterprise", "Lexington", "Saratoga", "Yorktown", we're now reduced to naming carriers after dysfunctional U.S. presidents? I guess if we can go from "Operation Overlord" to "Operation Restore Hope" that's par for the course. Never has one nation sucked so hard at so much.

Wallpapers-az.com

[Anonymous Coward]

9zeci ro iPhone 4 wallpapers are very much a thing of personal preference. Not everyone wants their iPhone 4 to look like a candy bar and, equally not everyone wants theirs to look like something more suited to space travel. Fortunately there is a huge choice of vallpapers, either self produced or purchased. If you decide to purchase walpapers it is certainly best to shop around. Personally I would avoid buying them directly from the web, there are a number of apps available from the app store and these will have passed muster with Apple. iPhone 4 Wallpapers are now available that will show off the iPhone 4 and its Retina Display Support at it's absolute best. These are the sort of dual screen I would go for but be warned, the choice is vast! Generally, expect to pay a little for the apps, but certainly no more than 59 pence. These apps will have a nominal selection of Full HD 4 3D HD immediately available for use, but as a rule a quick download is the norm. The apps generally set the design HQ in different sub sections so it is well worth having a mental picture of what you are looking for and sticking to that idea, that is unless you have plenty of spare time on your hands. Once you have selected your iPhone 4 pc">wallpapers they will be downloaded to your camera roll. Simply do the following, select settings> select wallpapers>select Camera roll or the relevant album>select the iPhone 4 wallpaper you have chosen>tap the set button>then you can select to have your iPhone 4 wallpapers set as Lock Screen, Home Screen or both

That's what flywheels are for.

[Ungrounded Lightning]

AFAIK there is no electrical turbine that will supply an extra 153 MW at the flip of a switch. Electrical energy has to be stored somewhere to let the catapult work.

That's what flywheel/motor-generator systems are for. Crank it up at (relative) leisure, dump it out quick when you need it. Turns a 1.7 second load of 153 MW into a two-minute load of 2 1/6 MW. Much easier to handle. (Also much less copper in the wiring from the reactors to the catapult system.)

While I don't know if the Navy is using a flywheel peaking system on this catapult, it would be a logical move. I have seen reports of such systems being used with actual railgun/coilgun experiments on tank-like platforms.

Supercapacitors might be up to the necessary energy storage these days, too.

EMALS + Ski Jump?

[Anonymous Coward]

I wonder if EMALS can be retrofitted to ski jump carriers, or a ski jump can mixed with EMALS?

Get both the height/flinging advantage of the jump, as well as the smooth control and increased power of the electric catapult.

Since it is a linear motor, there shouldn't be a problem in theory with making a curved catapult track, right?

Plus, if you're in need of space for an EMALS upgrade, you could stuff the flywheels and other components in the ski jump, which is an otherwise awkward space to use...

Re:EMALS + Ski Jump?

[aztec1430]

Why not curve it up the side of a mountain - extend it to 4 miles long... strap a shuttle to it...(accelerate at 3g the whole way) ... zoom!

Let's be fair to the editors.

[Ungrounded Lightning]

If you were expecting technical accuracy from our esteemed professional Slashdot editors, that day has not yet arrived.

Let's be fair to the editors. The "railgun" business (and mistake) is from the headline and text of TFA. (This is USUALLY the case when there are such technical mistakes in the headlines and/or text of slashdot articles.)

The editors' job is to sort out what stories are of interest, not to correct the stories (and potentially corrupt them further). The latter is OUR job as reply posters and (to a lesser extent) the job of the submitters (again with the caveat of potential further distortion). B-)

If you want to flame somebody, lay off the editor and flame the submitter.

That is NOT the measure of a Great President.

[Ungrounded Lightning]

To say "Congress wouldn't do what the President wanted" is the same as saying "the President failed to get Congress to do what he wanted."

Absolutely not.

The Congress is there to determine the "will of the people" and the President to execute it. They are often at odds about what should be done - and it's the job of Congress, not the President, to make the call. The President, as the guy that has to implement the results, has significant input - enough to override a small majority for the opposite view. But if the majority is significant, and the mandate is Constitutional, he has to suck it up and carry out the will of the People as expressed through Congress.

If the President is sufficiently charismatic to sway Congress to his position when it differs from that of a large majority of the population, he's not a great President. He's becoming an Emperor and/or Tyrant.

Now if the Congress deviates from the will of a large majority of the population (i.e. like right now) that's another issue. But it's between the people and Congress.

6.44 g

[idji]

100,000 pounds=45359 kg (not needed to calculate g force)
240 mph= 108 meter/second
300 feet = 91 meter

From highschool physics v^2-u^2=2as
u= initial speed=0, v= final speed=108. a=acceleration, s=distance.
so acceleration = v^2/2s

gforce = a/9.81=v^2/2/s/9.81=108^2/2/91/9.81=6.44g, which is not going to kill a navy pilot, but will make a mere mortal full horrible.

The turbine isn't really the main problem

[sean.peters]

The big problem was always that the pumps would develop steam leaks around the seals. This causes problems: 1) heat buildup in the engineering spaces, which leads to shortened watch times for engineering personnel, 2) fuel economy problems - you have to burn oil to replace the lost steam, and 3) poor functioning of the pump itself - as steam leaks around the seals, there's less available to run the pump.

The turbine itself usually didn't have any problems unless your steam got contaminated somehow... but if it did the results were typically catastrophic. Little tiny drops of water entrained in the steam will seriously screw up your blading. This didn't happen all that often, but sometimes.

The net result is that steam turbines were less reliable and more troublesome than electric motors.