NASA Looks At Railgun-Like Rocket Launcher

coondoggie writes "NASA is looking hard at a way to blast spacecraft horizontally down an electrified track or gas-powered sled and into space, hitting speeds of about Mach 10. The craft would then return and land on a runway by the launch site."

Comments

Well, this is not a

[ScrewMaster]

new idea, exactly, but I guess it's good to see NASA looking at other possibilities. There are many. I remember MIT doing work on alternate launch technologies back in the seventies, if not earlier. The mass driver was one (a giant electromagnetic linear accelerator) although the idea was kicked around in science-fiction long before that. My current favorite is a possibly-reusable rocket whose reaction mass is water, using heat energy provided by ground-based lasers. You could launch things into orbit all day long with a setup like that. Probably need a dedicated nuclear power plant to run the thing.

Re:Well, this is not a

[pilgrim23]

http://www.youtube.com/watch?v=G3yN6WfpaUQ its been done

Re:Well, this is not a

[PolygamousRanchKid]

Well, I believe this critter was up and at it in the 70's at Princeton: http://en.wikipedia.org/wiki/Gerard_K._O'Neill

Re:Well, this is not a

[ScrewMaster]

Well, I believe this critter was up and at it in the 70's at Princeton: http://en.wikipedia.org/wiki/Gerard_K._O'Neill

Yah. Him too. Sometimes I forget that Google is my friend.

Re:Well, this is not a

[rjstanford]

Ah, Heinlein, may you never cease to spin.

Anyway, the other think to consider (especially for things like laser-based launches) is that the current "spit out a ton of speed really quickly and then coast your way to orbit" approach really sucks. Even a slow nice steady boost will get you to orbit without needing to hit escape velocity.

Re:Well, this is not a

[timeOday]

Oh, it was already imagined in sci-fi novels and childrens' TV programs? Quick, somebody tell NASA before they waste a bunch of money developing a usable capability!

Re:Well, this is not a

[findoutmoretoday]

Yes, escape velocity is about is more an expression for energy, not speed.  But the slower you go the more energy you need, and in a certain way the higer the escape velocity will be.

Re:Well, this is not a

[Nyeerrmm]

Who coasts into orbit? Once the engine cuts off in most any launch vehicle you've achieved orbit.

Get going at the right speed from the ground and you'll enter orbit as long as there's not a mountain in the way (you'd probably want to boost your periagee afterwards though). The main reason you go up before accelerating to orbital velocity is that you get above the atmosphere and don't lose as much energy.

Re:Well, this is not a

[ScrewMaster]

Even a slow nice steady boost will get you to orbit without needing to hit escape velocity.

Well, sure, you could do at a walking pace ... if you had the reaction mass.

Re:Well, this is not a

[camperslo]

Yes, in addition to Fireball XL5, it was also done in When Worlds Collide.

Re:Well, this is not a

[BlueStrat]

Ah, Heinlein, may you never cease to spin

Yes, Heinlein used this tech as a centerpiece enabling technology for Moon->Earth grain shipments (and as a kinetic weapon used against Earth once the rebellion started..."throwing rice") from a lunar penal colony in his superb science fiction novel "The Moon Is A Harsh Mistress". I highly recommend the story. Heinlein was amazing at predicting tech & science advances far, far ahead of any of his contemporaries.

In the above Heinlein novel, a rail launcher for Earth was proposed for several possible locations. These proposed locations shared certain characteristics, among them was elevation/altitude at the launcher exit point.

NASA could do a lot worse than taking some more inspiration (IIRC he's generally credited with the concept of communications satellites) from such an intellect.

Strat

Re:Well, this is not a

[InfiniteWisdom]

"spit out a ton of speed really quickly and then coast your way to orbit" approach really sucks

A "nice slow steady boost" will burn an enormous amount of fuel.

Let's say your rocket weighs 1,000lb. If you provide = 1000lb of thrust your rocket will just sit there. If you provide 1001lb of thrust it'll start to accelerate every so slowly... if you provide 1002lb of thrust you'll accelerate twice as fast, but only burn ~0.1% more energy.

You'll go faster (for a given thrust) as you burn up fuel and thus shed weight, but at any weight, the higher the thrust, the smaller the percentage of energy you spend just overcoming gravity, and the more you spend accelerating the vehicle.

And don't forget, that if you got above the atmosphere "slow and steady"... if you're under orbit velocity, you're going to fall right down unless you plan on burning fuel forever.

Re:Well, this is not a

[ScrewMaster]

IIRC he's generally credited with the concept of communications satellites

Nope. That was Arthur C. Clarke, another of the grand masters of hard science-fiction.

Re:Well, this is not a

[BJ_Covert_Action]

Depends on what engine and what launch vehicle you are talking about actually. Some of the larger, multi-stage vehicles will cut off the main booster or first stage before achieving a true orbit. This is usually followed by such a short coast that the primary cut-off doesn't matter. The rest of the launch vehicle will continue gaining altitude until ignition of the second stage. This isn't always the case, but, like I said, it depends on the vehicle and payload you are flying.

Re:Well, this is not a

[mdielmann]

There are a number of reasons why rail guns are more attractive than a "steady boost".
First, we don't have anything that gives a steady boost for any reasonable amount of time at a reasonable amount of force. Rockets just don't last very long in the overall scheme of things, and laser-based propulsion systems don't have enough force to launch any appreciable payload (yet).
Second, rail guns don't require you to accelerate fuel in order to keep on accelerating. This puts an effective limit on rockets, and anything the rail gun adds pushes out our capacity based on the fuel limit.
Third, the higher/faster you're going before you start using conventional rockets will reduce fuel requirements, increase payload, or increase orbit. This is somewhat related to the second item, but not entirely. Conventional rockets require you to bring your fuel with you, which reduces payload capacity, and this compounds with the effects of being deeper in the gravity well.

Re:Well, this is not a

[pixelpusher220]

Yeah but going mach 10 at ground level isn't exactly rainbows and ponies either...

Re:Well, this is not a

[BlueStrat]

IIRC he's generally credited with the concept of communications satellites

Nope. That was Arthur C. Clarke [lakdiva.org], another of the grand masters of hard science-fiction.

Ahh, right you are! Clarke and Heinlein are two of my favorite sci-fi authors. I really should have gotten that right. :/

Strat

Re:Well, this is not a

[Shadow Wrought]

Yeah but going mach 10 at ground level isn't exactly rainbows and ponies either...

True, but you do have the potential to turn ponies into rainbows...

Re:Well, this is not a

[pclminion]

There is no such thing as "coasting into orbit." When the power cuts off, you are either in orbit or you aren't. When there is no thrust, your kinematic state is determined for all time -- you're purely under the laws of freefall mechanics. If you're not in orbit when the engines cut, you'll either hit the ground or escape the gravity well. There's no transitional period -- if there were, what forces would be acting to cause the transition? Gravity is a conservative force.

Re:Well, this is not a

[Nyeerrmm]

Fair enough. I think what the grandparent was trying to imply was to use a "Slow-push" method to get to orbit, with continuous thrust, rather than a traditional Impulsive transfer trajectory -- something which doesn't really apply to getting out of the atmosphere in the first place.

Re:Well, this is not a

[sumdumass]

How does inertia or momentum figure into that? It seems to me that you would coast for a while before gravity takes control.

Re:Well, this is not a

[robot256]

That would be a rather unfortunate pony, and a rather monochromatic rainbow. Do these things come with windshield wipers?

Re:Well, this is not a

[robot256]

before gravity takes control.

As the GP said, gravity is a conservative force. It is ALWAYS in control. Right now, gravity from distance stars is pulling us in their direction--the force is infinitestimal but present nonetheless. It is an extreme colloquialism to say that when you throw a ball up in the air gravity "takes control" when it starts to fall down, never mind that gravity caused the slowing of its ascent as well. Same as in orbits.

"Coasting into orbit," in your colloquial usage, simply means cutting the engines at a lower altitude than the final orbital altitude. To pull it off, you have to be going faster than orbital velocity at the lower altitude so that after your engine is cut off, some of your kinetic energy is transferred to potential energy, and you slow down while still going up until you reach the final orbit. This is no doubt used for small portions of most flights. But the GP's point is correct; anyone who understands Newtonian physics will be able to tell whether and what orbit you will reach once you cut your engines, thus no one ever bothers to talk about "coasting".

The only difference with a railgun-only launch system is you reach the maximum velocity at ground level and spend the *entire* trip to orbit "coasting." This is not what NASA is proposing. They will use the railgun only as the first stage, followed by scramjets and an orbital-insertion rocket engine, which is a much more realistic proposal.

Re:Well, this is not a

[ScrewMaster]

IIRC he's generally credited with the concept of communications satellites

Nope. That was Arthur C. Clarke [lakdiva.org], another of the grand masters of hard science-fiction.

Ahh, right you are! Clarke and Heinlein are two of my favorite sci-fi authors. I really should have gotten that right. :/

Strat

Me too. If there's a story one of them wrote that I haven't read, well, somebody please tell me so I can read it.

Re:Well, this is not a

[Anonymous Coward]

It would be expensive, and you'd want to terminate the track off the side of a mountain to gain as much altitude as possible, but with a strong enough vacuum system in place to reduce pressure in the tunnel it would certainly be possible. Be one giant fucking launch track though.

Re:Well, this is not a

[Anonymous Coward]

"Gravity is a conservative force."

Dammit, did the Tea-Party get to them too?

Re:Well, this is not a

[brianerst]

He may not have invented the comsat, but he did invent the waterbed!

The wiki on him has a nice list of stuff generally thought to have been presaged in Heinlein's works.

Re:Well, this is not a

[Ruie]

Ah, Heinlein, may you never cease to spin.

Anyway, the other think to consider (especially for things like laser-based launches) is that the current "spit out a ton of speed really quickly and then coast your way to orbit" approach really sucks. Even a slow nice steady boost will get you to orbit without needing to hit escape velocity.

There is a good reason for that - if you are carrying your reaction mass with you then it is more energy efficient to expend it quickly rather than drag it out.

Re:Well, this is not a

[cyclomedia]

actually orbit is a kind of freefall, just one where you never hit the ground, so having an initial trajectory pointing diagonally upwards is all you need, you just need to get the angle and velocity right. There is no "orbit" that you park in or land on, it's freefall all the way down.

Re:Well, this is not a

[CrimsonAvenger]

Even a slow nice steady boost will get you to orbit without needing to hit escape velocity.

Hint: if you're in orbit, you never hit escape speed (not velocity - the only direction that matters is that you not be aimed at the ground - any other direction will mean that you escape from Earth's gravitational control).

That said, a normal rocket's boost is about the most fuel-efficient way to reach orbit. Slow and steady might get you there eventually, but at a vastly higher cost in fuel or reaction mass.

Re:Well, this is not a

[u17]

When you cut off your engines, you *are* in orbit. There is no "final" orbit to go to from there. The only question is, does your orbit intersect the Earth or not :-)

Re:Well, this is not a

[dwinks616]

Tea-bag party isn't "conservative", they are just lunatics.

Re:Well, this is not a

[dwinks616]

and laser-based propulsion systems don't have enough force to launch any appreciable payload (yet).

And they never will. Lasers will NEVER be able to push anything into orbit, period. E=MC2. If you make E big enough to push a payload into orbit, your E ends up turning into M. Lasers only a bit more powerful than what we have now will end up creating matter in their pumping chambers and halting their output. The top few lasers on the planet are pretty close to the maximum power lasers can attain before spontaneously creating mass from the light they make. What may work, however is using a laser to beam power to the "solar" cells at the bottom of a space elevator and using that power to inch up the elevator cable.

Re:Well, this is not a

[robot256]

Oh my, you are right. You never "coast" into a circular orbit from a "lower altitude at a higher velocity", you simply end up in an elliptical orbit. Which may or may not intersect the earth, as you so accurately put it.

I just hope this post gets modded up as much as my previous (incorrect) one.

Re:Well, this is not a

[yodleboy]

"Heinlein was amazing at predicting tech & science advances far, far ahead of any of his contemporaries."

True, except for the proliferation of computers and the radical miniaturization of electronic components we enjoy today. Heinlein missed that completely. It's all tubes and wires in his stories and tasks that are done quickly by computer today (calculating an orbit for example) are nearly always done by hand. It's almost as if he had a blind spot for computers and envisioned a future society where math was the cool subject.

he's still one of my favorite authors of all time.

Re:Well, this is not a

[Muad'Dave]

That's rather eloquently called Sparking the Vacuum.

Re:Well, this is not a

[dave420]

There is always the idea of a space-plane with a hybrid engine. Instead of pushing upwards through a dense atmosphere while carrying oxidiser, use the lift of wings in that dense air and the oxygen in the air to burn fuel. Once the atmosphere is too rarefied to provide enough oxygen, switch to the internal oxygen tanks. A plane like that can burn for significantly longer (one such design, Skylon, can burn for nearly 47 minutes) than a comparable rocket engine.

Re:Well, this is not a

[Anonymous Coward]

extreme colloquialism

Wow, that would be a really awful name for a band.

Re:Well, this is not a

[BlueStrat]

"Heinlein was amazing at predicting tech & science advances far, far ahead of any of his contemporaries."

True, except for the proliferation of computers and the radical miniaturization of electronic components we enjoy today. Heinlein missed that completely. It's all tubes and wires in his stories and tasks that are done quickly by computer today (calculating an orbit for example) are nearly always done by hand. It's almost as if he had a blind spot for computers and envisioned a future society where math was the cool subject.

Well, he didn't miss it completely. You have to compensate for his time frame. Heck, he was born in 1907 and discharged from the navy in 1934, well before WW2. Radio was still a relatively new tech then. We're talking 3 years before Amelia Earhart's last famous flight. He did have the co-lead character "Mike" (short for "MYCROFT"), who was a self-aware computer (he "woke up" one day) in Heinlein's 1966 novel "The Moon Is A Harsh Mistress".

he's still one of my favorite authors of all time.

Same here. My top-three classic sci-fi author list contains Asimov, Clarke, and Heinlein. Vernor Vinge has done some great work more recently. There are many more worthy of mention, too many to list here.

Strat

Re:Well, this is not a

[BJ_Covert_Action]

Well, yeah, that makes sense then.

Re:Well, this is not a

[mdielmann]

Yes, there's the ultimate limit you mention there, and even if you could capture all that energy from a laser, it still won't be enough to generate a useful amount of acceleration. Definitely a useful proposal for a space elevator crawler, where you don't have to fight the force of gravity at the same time.
I haven't done the numbers, but I can imagine a time where a small electric engine of some kind can generate enough thrust from a small number of high-powered lasers being used to supply power to get a small payload into orbit. Continuous acceleration can do pretty amazing things.

Re:Well, this is not a

[Anonymous Coward]

Ooh, can it be a AWESOME Double Rainbow?? Please, please, please?

Re:Well, this is not a

[ScrewMaster]

He may not have invented the comsat, but he did invent the waterbed!

Arguable as important a technological and social advance as the geosynchronous satellite, I'd say.

Re:Well, this is not a

[Anonymous Coward]

Even a slow nice steady boost will get you to orbit without needing to hit escape velocity.

Yes, but if you're at orbital height and you're not at escape velocity then you're coming right back down again in a big hurry. If you're in orbit (i.e. circling the planet in a stable manner), then by definition you are going at least at escape velocity.

Re:Well, this is not a

[Anonymous Coward]

Sure, go ahead and get shot into space and be squished like a bug. I'll just use the elevator... Space Elevator

Re:Well, this is not a

[ScrewMaster]

"Gravity is a conservative force."

Dammit, did the Tea-Party get to them too?

No, but they've begun measuring rocket engine power output in "Limbaughs".

So sue me.

Re:Well, this is not a

[pixelpusher220]

Unless your tunnel extends into space, going from significantly reduced pressure into higher pressure is going to be like a bug and a windshield.

Maybe someone should tell them...

[Anonymous Coward]

That space is up.

Re:Maybe someone should tell them...

[arkane1234]

Space is not up, it's all over, we're on a sphere.
You can go to your right and ignore gravity completely to reach space.

Re:Maybe someone should tell them...

[ScrewMaster]

That space is up.

Up is relative. Space is away.

Re:Maybe someone should tell them...

[AnonymousClown]

That space is up.

You see, they'll fire the spacecraft horizontally and it'll fly really really fast until it falls off the World into orbit.

Re:Maybe someone should tell them...

[Spectre]

Space is not up, it's all over, we're on a sphere.
You can go to your right and ignore gravity completely to reach space.

Damn it, we've been doing this rocketry thing the hard way.
The easy way is just to "ignore gravity"!

(Yes, I know what you mean, but it is more fun this way :)

Re:Maybe someone should tell them...

[butterflysrage]

so basically the trick is to fall down and miss?

Re:Maybe someone should tell them...

[sconeu]

You're being facetious, but that's exactly what would happen.

Re:Maybe someone should tell them...

[Yvan256]

Up and at them!

Re:Maybe someone should tell them...

[Anonymous Coward]

If I've learned one thing from Superman, it's that the formula for flight is up, up, and away. Therefor it is 2/3 up, and 1/3 away.

Re:Maybe someone should tell them...

[Ethanol-fueled]

Ignoring gravity works when you run off the edge of a canyon or your ACME rocket runs out of propellant. You don't fall until you actually look down and remember gravity.

Re:Maybe someone should tell them...

[GigG]

"Fall down and miss" is orbital dynamics at is most basic.

Re:Maybe someone should tell them...

[Anonymous Coward]

Ignoring gravity works when you run off the edge of a canyon or your ACME rocket runs out of propellant. You don't fall until you actually look down and remember gravity.

So all the issues with overcoming Earth's' gravity well since the inception of the manned space program have been due to astronauts not keeping their eyes on the stars?

Huh. Explains a lot.

Re:Maybe someone should tell them...

[Anonymous Coward]

Whoosh!

(that's the sound the craft would make going by overhead, nothing like the sound of his humor sneaking by you disguised as facetiousness..)

Re:Maybe someone should tell them...

[Ironhandx]

This needs more +1 insightful as well as some +1 informative. This is exactly what would happen. In fact rocket launches already take some advantage of this fact. Going absolutely straight up would cause a whole world of hurt on the vertical frame and require extra fuel. Launching on an angle mitigates this. Basically you're traveling further to get out of the atmosphere but using less energy overall. If ground based launch facilities can get it to 600 m/h and then a scram jet can get it to escape velocity it could be a much much more efficient model.

They've done very little research into the subject other than some launch off the back of a jumbo jet tests over the last 20-30 years. There has to be a better way than just brute force high energy rocket fuel.

Re:Maybe someone should tell them...

[ScrewMaster]

If I've learned one thing from Superman, it's that the formula for flight is up, up, and away. Therefor it is 2/3 up, and 1/3 away.

Yes, but I understand that for other countries the formula may be different. Remember, he was all about Truth, Justice and the American way. So, for example, when Russia wants to launch a spacecraft, they have to use Up, Up, and the Soviet way, which as we all know, is somewhat different.

Re:Maybe someone should tell them...

[spazdor]

NASA should hire people with surprising bodies and/or opinions to jump out and reveal/explain them, providing a needed distraction at the critical moment.

Re:Maybe someone should tell them...

[godel_56]

Whoosh!

(that's the sound the craft would make going by overhead, nothing like the sound of his humor sneaking by you disguised as facetiousness..)

At Mach 10 it'd be more of a Bang! than a Whoosh!, probably taking out your windows in the process.

Re:Maybe someone should tell them...

[geekoid]

Space is around.

Re:Maybe someone should tell them...

[ozmanjusri]

Up, up and away!

Re:Maybe someone should tell them...

[nospam007]

I ignore Gravity all the time, alas she doesn't ignore me.

Re:Maybe someone should tell them...

[The Wild Norseman]

That space is up.

Yeah, but the enemy's gate is down.

Re:Maybe someone should tell them...

[EnsilZah]

I sometimes lay outside and try to think of the sky as 'out' rather than up.

Re:Maybe someone should tell them...

[crafty.munchkin]

Yes it is... while NASA spent $1 million developing a pen that works in zero-g, the Russians used a pencil!!!

Re:Maybe someone should tell them...

[martas]

douglas adams reference, nice

Re:Maybe someone should tell them...

[tophermeyer]

Yes it is... while NASA spent $1 million developing a pen that works in zero-g, the Russians used a pencil!!!

Actually, turns out this was a worthwhile program. Considering we will be carpooling our manned space flight with the Russians for the next several years, it might be nice to be able to write them a check up there for gas and tolls.

The fools never realized that a signature with Space Pencil is not legally binding.

Re:Maybe someone should tell them...

[Coren22]

Funny, but false.

http://www.snopes.com/business/genius/spacepen.asp

Re:Maybe someone should tell them...

[Anonymous Coward]

glad someone else got that

Re:Maybe someone should tell them...

[Anonymous Coward]

NASA didn't spend any money on that fancy pen. It was developed independently by a private company which offered it to NASA for marketing purposes only. $1 million may have been spent on its development, but that wasn't taxpayer money and certainly had nothing to do with a desire on the part of NASA to have the pen in the first place. See: http://en.wikipedia.org/wiki/Space_Pen

Note too that the Russians used a grease pencils instead of a standard graphic pencil you would have for your school work. NASA used the graphite pencil for the early Mercury and Gemini missions, but switched to the space pen in part due to concerns about bits of the pencil (graphite is a conductor) getting stuck between electrical contacts and causing a short. Also, given the Apollo missions were done in a 100% oxygen environment (partial pressure was the same as on the Earth at sea level), there was some concern about the wood in the pencil acting as a potential fuel source for fire and therefore an alternative was sought.

Re:Maybe someone should tell them...

[billybacs]

I just read this book for the first time recently. Hooray for getting references.

NASA still cannot do simple math.

[drcheap]

"...hitting speeds of about Mach 10."

"Starr noted that electric tracks catapult rollercoaster riders daily at theme parks. But those tracks call for speeds of 60 mph -- enough to thrill riders, but not nearly fast enough to launch something into space. The launcher would need to reach at least 10 times that speed over the course of two miles in Starr's proposal."

Mach 10 = 600mph ???

Re:NASA still cannot do simple math.

[Tekfactory]

Perhaps it only needs to get up to 600 MPH before the Scramjet takes over.

If you read any of the articles on their scramjet tests, they need supersonic airflow to create the pressure inside the engine. Once ignited, Mach 10 wouldn't be outrageous for a Scramjet.

http://www.shortnews.com/start.cfm?id=63070

Unfortunately escape velocity isn't Mach 10, but for early test platforms, we already have the tech necessary to do what's in the proposal, and what we might learn from repeated launches and fine tuning the scramjet, seems promising.

Re:NASA still cannot do simple math.

[phantomfive]

The launcher would need to reach at least 10 times that speed

"At least"....for all those times when you can't quite do the math!

Re:NASA still cannot do simple math.

[durrr]

http://en.wikipedia.org/wiki/Scramjet#Theory
Scramjets don't need supersonic airflow, they only need a dynamic pressure that is in the right interval. If you look at the equation in the wiki link you'll see that it will be able to operate at lower speeds at lower altitude, in fact, it will not be able to operate at mach 10 at low altitude at all, but would constantly speed up as it gains altitude to keep an approximately constant dynamic pressure.
Seems elegant enough for me.

And the scramjet would only be a middle stage vehicle, it would carry a rocket craft in addition to put things into orbit.

Re:NASA still cannot do simple math.

[Prune]

The author probably rounded down to 100 times the speed and dropped a zero, possibly as a typo. It's the only plausible explanation I could come up with for this error.

Re:NASA still cannot do simple math.

[drcheap]

The launcher would need to reach at least 10 times that speed

"At least"....for all those times when you can't quite do the math!

Ahh yes, I seemed to overlook the fact that (approx)7600 >= 600. I guess they were correct all along.

Well enough about that, I have to go check out that great "up to 100% off" sale at my local consumer electronics store.

Re:NASA still cannot do simple math.

[X0563511]

Only at a ridiculously low pressure...

(mach is dependent on the speed of sound, which is dependent on the atmospheric temperature and pressure)

Re:NASA still cannot do simple math.

[vlm]

Once ignited, Mach 10 wouldn't be outrageous for a Scramjet.

Well, that seems a bit optimistic for a device that has been successfully flown, what, twice? Its kind of like planning the Boeing 777 the day after the wright brothers first flight.

The real killer with all these "hybrid" lifter designs is they are all ignorant of the virtually unknown 666 rule.

The 666 rule is that Mach 6 (which is tricky for an air breathing aircraft) at 60000 feet (again, tricky) is a whopping 6% of the way to orbit.

So, if, in your wildest dreams, you can simultaneously achieve mach 6 at 60Kft, which would be quite the noteworthy achievement, you've still got 94% of the way to go.

Alternately, you could take the required second stage, and make the fuel tank at least 6% bigger and skip all this air breathing foolishness.

Re:NASA still cannot do simple math.

[Anonymous Coward]

I guess 10 x 60mph = 7,612. Maybe there was a conversion problem there.

    One team, the ones who got to ride roller coasters for the sake of science, were using base 10 and American measurements.

    Another other team stayed back in the lab. They decided to measure the speed as furlongs per sidereal hour, and all the numbers were done in at base 126.

Re:NASA still cannot do simple math.

[bcmm]

Perhaps it only needs to get up to 600 MPH before the Scramjet takes over.

Well, unless something is taking over, this is just a big artillery piece: escape velocity is rather higher than mach 10.

Re:NASA still cannot do simple math.

[ratboy666]

Maybe just missing a "0" -- should be "100 times", but even that's low. Mach 10 is around 6600 mph "where the jets go" and 7700 at sea level.

Of course, escape velocity is 25,000 mph (no friction from the air factored in), but (and I didn't read tfa) it seemed like they want to come back (maybe like a really big boomerang?), so I don't think it matters.

Just for grins, if the thing is launched at a 45 degree angle, it should reach a maximum height of approximately 185 miles, and travel a distance of around 750 miles (every done in US measurements for you).

It will do that in 8 minutes. All presuming no air, which does tend to mess with the calculation a bit :) Still, to accelerate to Mach 10 on a rail? That's something I really want to see! If the projectile weighed in at 1kg (2.2 lbs), the resulting hit would be equivalent to an explosion of 3 lbs of TNT (again, no air resistance factored in).

That's all I got... now I might go read TFA...

Re:NASA still cannot do simple math.

[Anonymous Coward]

You don't need escape velocity to orbit. (but yeah, even that velocity is higher than mach 10)

Re:NASA still cannot do simple math.

[strack]

im pretty sure mach 25 is orbital velocity. which would make mach 6 a bit over 20% of the speed needed. which is more than 6%. and altitude dosent really even come into the equation. if your going mach 6 at 60k feet, your trajectory is gonna get you to the needed altitude for space anyway. the majority of energy needed for orbit is for lateral motion, not height.

Re:NASA still cannot do simple math.

[strack]

well the rail guided rocket sled speed record is mach 8.5: http://en.wikipedia.org/wiki/Rocket_sled

Re:NASA still cannot do simple math.

[dbIII]

Well, that seems a bit optimistic for a device that has been successfully flown, what, twice

It was running in a shock tunnel in 1987 when I first saw one. Flight tests above Mach 6 are expensive so only get used if there's no other way to get the data.

Re:NASA still cannot do simple math.

[urusan]

Well, that seems a bit optimistic for a device that has been successfully flown, what, twice? Its kind of like planning the Boeing 777 the day after the wright brothers first flight.

I don't see how flying a device that actually performs to the required specs (the X-43 reached Mach 9.8 at 43k ft) and then making plans to use this new capability is like planning to make another device that is far better. It's more like thinking about flying regular cargo between two cities the day after the Wright Brother's first flight. Sure it's not happening today or tomorrow, but if we work on it then in a decade or two...

Alternately, you could take the required second stage, and make the fuel tank at least 6% bigger and skip all this air breathing foolishness.

You're missing the point. The advantage of an air-breathing craft is that it can weigh less because it doesn't have to carry all that air for combustion. The lower weight means it takes less fuel to propel, which means it can weigh even less without all that extra fuel. Even better, the first stage doesn't require fuel to be carried on-board at all, allowing less expensive ground-based power to be used. There is great potential for energy savings, which would mean higher payloads and/or less expensive flights.

Re:NASA still cannot do simple math.

[CrimsonAvenger]

Alternately, you could take the required second stage, and make the fuel tank at least 6% bigger and skip all this air breathing foolishness.

Running a few quick numbers, if you're going mach 6 at 60k feet, you'll need about another 6400 m/s deltaV to reach orbit. Which represents a mass ratio of about 4.2 using SME performance (and yes, if you're aiming for an SSTO you probably don't want to use LH2).

Starting stationary from the ground, you need a mass ratio of about 8.0. Rather larger than 6% bigger fuel tanks, eh?

Re:NASA still cannot do simple math.

[vlm]

im pretty sure mach 25 is orbital velocity. which would make mach 6 a bit over 20% of the speed needed. which is more than 6%.

Ouch, hope your physics teacher doesn't see your post. If E=1/2 * m * v**2, the ratio boils down to (mach6)**2 / (mach25)**2 which works out to 36/625 which works out to 5.76 percent. The energy required to gain altitude does matter, if you're going up a couple hundred miles. If it didn't, elevators wouldn't need motors. You are correct that the velocity is where most of the energy goes, and I didn't bother to verify the math, but its vaguely around the remaining 0.24 percent figure.

My point still stands, an idealized orbital rocket at mach 6 and 60kft has only burned about 6% of its total fuel.

Re:NASA still cannot do simple math.

[vlm]

Yes, you've verified the staging equations, but you're still better off with a traditional, simple, ultra reliable first stage. The absolutely cheapest thing about orbital rocket launchers is the propellants, everything from R+D to launch support costs more. "Saving fuel" is a profoundly false economy for orbital launchers. A great way to spend billions to save millions (or less).

Also first stage is arguably the most phase of flight. A terrible place to "innovate".

Re:NASA still cannot do simple math.

[u17]

It's not the altitude that's the problem, it's the amount of propellant that is needed to take you there. Given that the engine burns propellant at a constant rate, you burn the most propellant per unit of altitude when you go slowest, i.e. when you start. Therefore, even if your gain in altitude from rail launching is small, your gain in velocity can be large enough to save *a lot* of propellant, which is the whole point of this exercise.

Re:NASA still cannot do simple math.

[vlm]

There is great potential for energy savings, which would mean higher payloads and/or less expensive flights.

You want higher payloads, find a rocket that works, and make it bigger.

As for less expense, I take it you believe most of the cost of the space shuttle program is liquid H2? If so, you are horribly misinformed. If, by some utter miracle, the shuttle could be operated on flying unicorns instead of solid boosters and H2/O2, calculate the delta cost in the shuttle program. I think you'll be surprised how many decimal places you'll need to use.

Liquid H2 costs about a buck a pound in the quantities NASA uses. (We'd pay closer to two bucks a pound). The entire shuttle tank holds about a quarter million pounds of liq H2. No math phd required to figure that filling the fuel tank costs about a quarter mil. A similar level of math is required to multiply that by about 130 shuttle flights to get a lifetime program cost of a whopping 30 million or so. Wikipedia claims the total cost of the shuttle program from "I gotta idea" to end of program is about 175 Billion. So, liquid H2 fuel cost works out to 30 / 175000 * 100 = about 0.02 percent of total project cost. "Saving fuel" is simply irrelevant.

So, if we risk the lives of every crewman using a new non-man rated engine and/or delay the vehicle program by decades to develop and deploy the amazing fuel free flying unicorn engine system, we will save a whopping two hundredths of a percent of total program cost. Or rephrased, for the R+D to pay for itself, we need the total cost of R+D and deployment to remain below two hundredths of a percent of program cost.

Two hundredths of a percent of project cost is about what you budget for developing and deploying the HR diversity training, or perhaps company funded picnics. Not a realistic budget factor for a new primary propulsion system.

Re:NASA still cannot do simple math.

[u17]

Only the Chinese can use base 126.

Re:NASA still cannot do simple math.

[urusan]

The shuttle program is a horrible example. The shuttle program includes the orbiter in the cost, so that brings along a huge amount of extra financial baggage: astronaut training, experimental design and implementation, orbiter maintenance, and all sorts of other orbiter-centric organizational stuff that would not be part of a pure lifter system.

If you look at a rocket, let's say the Titan IV which has roughly comparable to the shuttle in terms of lifting (and age), it costs around $350 million per unit (and $432 million per launch). Assuming the fuel costs are similar, it's clear that 99.9% of the cost of the rocket launch are the rocket itself, not the fuel.

While this does support your assertion that saving fuel for cost reasons is not that important, it brings up another important issue that this system addresses. This launch system idea is mostly reusable as only the last stage is used up. You might say that the shuttle is reusable and it is much more expensive than a plain old rocket launch, but this is not really true as the shuttle costs $450 million per launch for a proportionately larger payload than a Titan IV, and that even includes the cost of the blinged out orbiter and everything that goes along with it...so really a reusable launch system has the potential to be substantially cheaper if it is well designed, even with the added complexities. Using the shuttle for anything less than shuttle orbiter-centric missions is a huge waste, but there's no way to separate the launcher and orbiter without creating a new system.

Additionally, the first two stages of this system would undergo far less stress than the shuttle does during its missions. The reusable part of the system not undergoing re-entry each mission means lower construction and maintenance costs compared to the shuttle system. It should also be safer than the shuttle system for these reasons (and the ability of the payload to detach during the second stage). Also, due to the lack of a built-in orbiter it would be far more flexible. Basically this gets us the best of both worlds (shuttle and traditional rocket). The lower energy costs are just bonuses.

The R&D costs for such a system are one time only. One of the main reasons projects like the B2 bomber and Space Shuttle were so costly was because the R&D costs were spread out over only a handful of units/launches. If this system is successful then it could lead to very large numbers of units produced and a very low cost per unit/launch.

Lastly, as some others have pointed out, there are secondary uses for research into air breathing hypersonic aircraft. The R&D effort may be worth it regardless of the success or failure of using it as a space launch platform.

Re:NASA still cannot do simple math.

[CrimsonAvenger]

All I was aiming for was to point out that the 666 rule was drivel. If you're at mach 6 at 60k feet, there's a great deal more than a 6% increase in fuel requirement to make up for that.

And while the first stage may be a terrible place to innovate, it's also utterly necessary to innovate there. The only way to bring launch costs down dramatically (say, by an order of magnitude or two) is to make your first stage trivially reusable. You needn't even manage mach 6 at 60k feet. Mach 4 at 60k feet from a trivially reusable (as in - as reusable as an airliner) would help immensely.

Note, by the way, that the SR-71 achieved a sizable fraction of "mach 6 at 60k feet" with 70's technology (mach 3.5+ at 85k+ feet). The problem is more one of size than of performance - we're talking a vehicle that can carry a 300 ton vehicle as cargo....

NASA plays too much Quake

[zero_out]

Railguns? Rocket launchers? Too much Quake I say.

Re:NASA plays too much Quake

[X0563511]

Indeed. Isn't this a mass driver?

Re:NASA plays too much Quake

[ScrewMaster]

Indeed. Isn't this a mass driver?

Or a Gaussrifle.

Re:NASA plays too much Quake

[X0563511]

Nope. It might be a Gaussian Accelerator or something like that, but it's no rifle. I'd hate to be spun like that on launch :)

Re:NASA plays too much Quake

[Anonymous Coward]

You'd end up nothing more than a Gaussian blur.

Re:NASA plays too much Quake

[ScrewMaster]

You'd end up nothing more than a Gaussian blur.

Yes, but you could use a CSI-style reverse algorithmic to recover the pilot's data.

Let's hope NASA is better at math than TFA

[Just_Say_Duhhh]

According to TFA, the sled will be "hitting speeds of about Mach 10." That's fast, but then the TFA says, "electric tracks catapult rollercoaster riders daily at theme parks. But those tracks call for speeds of 60 mph -- enough to thrill riders, but not nearly fast enough to launch something into space. The launcher would need to reach at least 10 times that speed"

Sorry, but 10x roller coaster speeds isn't close to Mach 10.

NASA is on to something interesting here. It would seem that MagLev is required (no wheels can handle that speed), and it would be interesting to see what kind of acceleration they can get out of LIM's. Rocket propulsion seems a waste in this application. It might help bullet-train technology, and we can get some new spin-off inventions from NASA.

Re:Let's hope NASA is better at math than TFA

[Fnord666]

According to TFA, the sled will be "hitting speeds of about Mach 10." That's fast, but then the TFA says, "electric tracks catapult rollercoaster riders daily at theme parks. But those tracks call for speeds of 60 mph -- enough to thrill riders, but not nearly fast enough to launch something into space. The launcher would need to reach at least 10 times that speed"

Sorry, but 10x roller coaster speeds isn't close to Mach 10.

I think he is looking for more like 128x. Furthermore TFA calls for reaching that speed in two miles. Anyone want to figure out the acceleration needed? There wouldn't be anything left but goo.

Re:Let's hope NASA is better at math than TFA

[jdgeorge]

You're expecting a particularly informed, insightful article about rocket science in NetworkWorld? Seriously?

Re:Let's hope NASA is better at math than TFA

[movrev]

Accelerating up to supersonic speeds on a maglev track is quite problematic from a controls/stability perspective. The generated shock waves will bounce off of the ground/track creating some interesting ground effects which will mess up the launch unless properly controlled. I'm sure their proposal is to get the sled up to about Mach 1, at which point they'll be able to take off with a ramjet engine. Once they reach around Mach 5 in the atmosphere, they could transition into a scramjet configuration which can theoretically allow them to reach orbital speeds. This specific problem has been in NASA's mind for a number of years now. I used to work on this precise thing in collaboration with them around 5 years ago.

Re:Let's hope NASA is better at math than TFA

[ISoldat53]

It's all that metric to inches stuff NASA can't seem to get right.

Re:Let's hope NASA is better at math than TFA

[FishTankX]

You could do even better by putting a good part of the maglev track in a vacuum. This would allow frictionless acceleration and possibly allow you to achieve ludicrous speeds. Possibly subjecting the package to be launched to hypersonic wind fronts for a lesser period of time.The trick would be the transition zone though. Maybe an airlock that's programmed to open at the correct time?

Re:Let's hope NASA is better at math than TFA

[movrev]

You could do even better by putting a good part of the maglev track in a vacuum. This would allow frictionless acceleration and possibly allow you to achieve ludicrous speeds. Possibly subjecting the package to be launched to hypersonic wind fronts for a lesser period of time.The trick would be the transition zone though. Maybe an airlock that's programmed to open at the correct time?

And at that point, the hypersonic payload will literally crash into the thick atmosphere close to the ground. You could launch it along the side of the mountain or from inside a mountain to reduce the density of the atmosphere that you encounter when coming out of vacuum, but you'll still have significant technical challenges.

Re:Let's hope NASA is better at math than TFA

[godel_56]

You could do even better by putting a good part of the maglev track in a vacuum.

[ . . . ] The trick would be the transition zone though. Maybe an airlock that's programmed to open at the correct time?

I've thought about this before. How about you pump the launch tube out to a dirty vacuum and cap it with a frangible plastic cap laced with explosives?

You detonate the explosive charge just before the capsule reaches the cap and the pressure bow wave pushes the shattered pieces out of the way.

Re:Let's hope NASA is better at math than TFA

[Anonymous Coward]

NASA is on to something interesting here. It would seem that MagLev is required (no wheels can handle that speed), and it would be interesting to see what kind of acceleration they can get out of LIM's. Rocket propulsion seems a waste in this application. It might help bullet-train technology, and we can get some new spin-off inventions from NASA.

Don't overthink it. Existing rocket sleds just use low-friction pads. They get up to 6400 mph, or about mach 11.

Re:Let's hope NASA is better at math than TFA

[amh131]

Back of the envelope for 6000 mi/hr (100 x 60 mph rollercoaster) in 2 miles gives something on the order of 114 G.

Re:Let's hope NASA is better at math than TFA

[BitZtream]

LIMs are 'theoretically' unlimited, you just have to space them out properly and sequence them fast enough. In practice of course, its entirely different. I think for most practical purposes of terrestrial motion, they will be practically unlimited until we invent inertial dampeners of some sort.

Re:Let's hope NASA is better at math than TFA

[Athanasius]

This is really just bad wording in his opening paragraph.
Really it's that:

1. 1) The railgun part needs to get things up to 600mph, 10x the rollercoaster speed.
2. 2) Once launched at 600mph off the railgun the scramjet fires up and eventually gets the thing to 'Mach 10'

The Universe Today article is worded a little better: http://www.universetoday.com/73536/nasa-considering-rail-gun-launch-system-to-the-stars/

Re:Let's hope NASA is better at math than TFA

[serutan]

This article explains it a little better. The rail launcher's job is just to get a scramjet vehicle off the ground by hurling it into the air at 600 mph. Then the scramjets take over and accelerate it to Mach 10. Then at 60,000 ft a second stage lifts the payload into orbit using rocket engines. They're just trying to eliminate the humongous first stage that currently comprises most of a typical rocket's weight.

Re:Let's hope NASA is better at math than TFA

[wvmarle]

Speeding up from 60 mph to mach-10 immediately made me think of one of the mantras of the Mythbusters: "if it's worth doing, it's worth overdoing!"

Re:Let's hope NASA is better at math than TFA

[Vectormatic]

which will still have your vehicle suddenly hitting a wall of atmospheric pressure, if you do everything right. At these kind of speeds that is probably like hitting a brick wall

Re:Let's hope NASA is better at math than TFA

[Neil Boekend]

There are some other issues. Modern systems are far from fast enough to correct the magnetic forces at high speeds. The whole system works like an mass spring system with a reverse dampener. Every fault causes the system to oscillate until you compensate. The speed limit is caused by the compensation time.
[assuming 0.01ms @ mach 5 is enough]
If you, for example, need a compensation time of max 0.01 ms @ mach 0.5 you'd need 0.005 ms @ mach 1 and 0.5 microseconds @ mach 10. To get some control with 100 A currents you'd need a PWM system with Mosfets. 16 bit PWM (for the high level control) at these speeds would require 0.5/(2^16)= 0.000008 microsecond = 8 nanosecond resolution. Can it be done?
[/assuming 0.01ms @ mach 5 is enough]

Re:Let's hope NASA is better at math than TFA

[trout007]

I took a look at the actual proposal. The launch speed off the rails is about Mach 0.5-1.5. The purpose of this test is to try different speeds. The rail is the "first stage". If the Mach 1.5 can be achieved than the second stage would only need a ram(Mach 1.5-4) /scram(Mach 4-10) jet for the second stage. Lower than Mach 1.5 the ram jet isn't as efficient and they might need high speed turbines or rockets to get get to 1.5 at least for testing. Mach 1.5+ would be required for an operational vehicle This would be reusable. The third stage would be capable of orbital insertion. What this system allows is the use of an air breathing second stage without having to have a rocket to get it up to the speed that a Ramjet needs to operate. You don't actually need maglev. Rocket Sleds use greased steel on steel and they got them above Mach 8. The maglev is great if you can do it because it reduces friction and cushions the ride so it might be better for an operational launcher.

Re:Let's hope NASA is better at math than TFA

[EvilDroid]

The proposal is to use the launcher to get up to the speed at which a scramjet can ignite, not Mach 10. The scramjet will then take you to Mach 10.

Net Assets' launcher?

[knarf]

Hey, it looks like someone read that Net Assets novel by one Carl Bussjaeger but decided that the trick could be done without using the libertarian sauce Bussjaeger pours over it. Bussjaeger ended up deciding that a rail gun or other tracked thing would not work so he went with a supersonic ground effect launcher.

Finally...

[Prune]

After all the hype that we've been hearing over the years about rail-guns and seeing a few military and hobbyist demos on video sites, this one piece of near-former sci-fi may be finally coming to fruition as a usable approach. It's a great example of the sort of thing that had to wait for technological improvements and refinements, rather than a fundamental scientific or technological breakthrough, and is the convergence of several technologies. I'm encouraged to see more progress on such things which seems to have in recent years been eclipsed by information technology's faster cycles and overhyping in media (and I say this as someone who makes his living as a software engineer).

Re:Finally...

[ScrewMaster]

After all the hype that we've been hearing over the years about rail-guns and seeing a few military and hobbyist demos on video sites, this one piece of near-former sci-fi may be finally coming to fruition as a usable approach. It's a great example of the sort of thing that had to wait for technological improvements and refinements, rather than a fundamental scientific or technological breakthrough, and is the convergence of several technologies. I'm encouraged to see more progress on such things which seems to have in recent years been eclipsed by information technology's faster cycles and overhyping in media (and I say this as someone who makes his living as a software engineer).

I, well, I agree. And make my living the same way. I've also been a science-fiction fan since I was a kid (Clarke, Heinlein, Norton, Silverberg, Harrison, Dick, you name it I probably read it) and honestly I've been disappointed by the past forty years, at least so far as near-space development is concerned. I thought, well, I'd hoped we would be way further along than we are, and had we continued the pace of development after the end of the Apollo program we would have be. But we chickened out, let our leaders dilute the vision and throw away the many of the gains we made during the sixties.

I'm always flabbergasted at the people who seriously believe that investment in space is a waste of time and money. Try to tell them that the economic benefits from that investment outweigh the costs, and they laugh at you, and say we would be better off spending it on "social programs." Hell, what the world has gained from, say, advanced weather prediction alone would pay for the space program.

The big problem is determining where to spend your resources in order to get the most ROI. Hell, for that matter, defining the ROI is something many people, politicians especially, simply can't agree.

Re:Finally...

[Anonymous Coward]

No. Sorry to disappoint all the folks who just don't get it, but this is not going to be a railgun. As a software engineer, your confusion on this is certainly excusable -- after all, even SF and video games, by and large, seem determined to make sure nobody understands what a railgun is.

At present, railguns suck -- even the Navy's version (the only thing close to being productized) is anticipated to need rail replacement/rebuild every dozen shots or so at first, with the hope that they can improve on that once it's operational. That's entirely feasible for a weapon that fires what's essentially a metal slug (perhaps a few hundred or thousand dollars) with range, accuracy, and damage on par with a $500,000 cruise missile; the money saved more than allows for having a bunch of replacement rails (only a few feet long) on hand, and replacing them can be done fairly quickly. They suck, it's just that cruise missiles suck even more.

But on a miles-long track, replacing or refinishing the rails is an insanely slow and expensive undertaking -- not that it's completely infeasible (after all, rockets, short of SSTO, suck pretty hard too), but you'd have a hard time solidly beating rocket launch rates and costs, and with the enormous capital outlay to build the launch ramp, you've gotta be sure you can undercut the competition and make it back. No, the reason it's called "railgun-like" in TFT, and "an electrified track" in TFS, rather than simply a railgun, is because it's going to be a linear induction motor or similar (in fact, probably a LIM to get up to Mach ~2, then a scramjet the rest of the way), not a linear homopolar motor, or (as the LHM with a projectile-armature is commonly known) railgun.

Oh, and FWIW, another quite interesting launch-ramp concept is the BFG's ram accelerator concept -- IMHO the most promising of the various alternative-launch-schemes-with-websites (aka crazy bastards looking for VC). Highly recommended reading for alternative launch geeks, especially those with enough sense to realize they won't see a geosynch space elevator in their lifetime...

Re:Finally...

[HawaiianToast]

Well, the application forms for funding are coming to fruition at least...

Re:Finally...

[Anonymous Coward]

may be the only light rail the US ever sees.

Re:Finally...

[DerekLyons]

After all the hype that we've been hearing over the years about rail-guns and seeing a few military and hobbyist demos on video sites, this one piece of near-former sci-fi may be finally coming to fruition as a usable approach.

Nope, this piece of "near former sci-fi" is just as far from fruition as it ever was.
 

It's a great example of the sort of thing that had to wait for technological improvements and refinements, rather than a fundamental scientific or technological breakthrough, and is the convergence of several technologies.

It's a great example of people not learning from the past and re-inventing the square wheel because now they have the tech to make carbon fiber square wheels instead of those old fashioned wooden ones.
 
But they're still square wheels.
 
The basic problem with a railgun is that it give only a fraction of the velocity required - and it does so only in one plane. (Orbital velocity has both a horizontal and a vertical component, railguns provide velocity only in the horizontal, cannons only in the vertical.) So you end up still needing a substantial rocket stage in order to provide the missing velocity - but now that rocket stage needs to be reinforced (thus increasing parasitic mass) in order to stand the stresses of being handled (while fueled) horizontally and of having to maneuver while still deep in the atmosphere[1] and insulated against structural heating from friction due to it's high speed low in the atmosphere... You end up not gaining anything over the conventional approach.
 
Railguns don't work because we lack some wonder technology for the gun - they don't work because the structural sums don't add up for the booster. Any materials improvement that you could apply to a railgun boosted launcher, you can also apply to a conventional launcher, which still leaves the railgun launcher trailing in performance and cost.
 
Railguns and a host of other alternative launch schemes look so simple and obvious that people simply cannot convince themselves that they don't work. So, they keep throwing money and tech at the problem convinced that this time it will work, it's so simple it just has to work. So NASA will waste a couple of hundred million dollars dicking around with the new gun - and then they'll discover the problem of booster design (again). And just like the last dozen times they've done this, the project will quietly be dropped.
 
Until the next time someone comes up with a PowerPoint presentation showing how this time it will be different.

[1] If you ever watch a rocket launch, you'll notice it goes more-or-less straight up for a couple of miles before starting to pitch over - there's a reason for that.

Re:Finally...

[interval1066]

Then after the professor trots the dancing girls out of the giant bullet-capsule the moon will grimace and wince as the bullet-capsule will be stuck in one of his eyes.

Re:Finally...

[Mr. Slippery]

honestly I've been disappointed by the past forty years, at least so far as near-space development is concerned. I thought, well, I'd hoped we would be way further along than we are, and had we continued the pace of development after the end of the Apollo program we would have be. But we chickened out, let our leaders dilute the vision and throw away the many of the gains we made during the sixties.

The "vision" of our leaders during the 1960s was 1) let's beat those darn Russkies at the propaganda game, and 2) let's be able to deliver a nuclear warhead to any point on the surface of the earth.

That's it. We've got the ICBMs, and our big propaganda conflict these days is with guys living in caves.

There's just not much reason to go into space. Satellites and robot probes, sure, but we've had many of those over the past 40 years, so that not what you -- not what we SF fans -- want. We want Man In Space. But there's just nothing you can have them do up there in orbit that's worth the expense of putting them there, except maybe repair the satellites -- and even there robots will be able to do the job cheaper in a few years. And there's not a lot of romance in being a free-fall Maytag repairman.

(I am not sure if I am playing devil's advocate here or not.)

Try to tell them that the economic benefits from that investment outweigh the costs, and they laugh at you, and say we would be better off spending it on "social programs." Hell, what the world has gained from, say, advanced weather prediction alone would pay for the space program.

If you want economic benefits on earth, you put your money here. Spin-off is a lousy argument. If you want faster computers, it makes much more sense to fund computer research than to fund a trip to the moon so some test pilot can plant a flag and have a photo op, on the theory that we'll need faster computers to guide his trip.

Sure, weather satellites are valuable; that doesn't justify manned moon shots.

If the justification for the manned space program is that it's inspirational, than it's just performance art -- put it under the NEA. If it's supposed to create jobs, it's just make-work, and we can instead have make-work projects that address pressing problems like renewable energy.

Re:Finally...

[Jeremi]

The basic problem with a railgun is that it give only a fraction of the velocity required - and it does so only in one plane.

Maybe I'm missing something, but can't you point the railgun in any direction you want? Granted it's probably cheaper to run the track along the ground, but you could at least in principle aim it straight up, or diagonally, or any other direction...

Incidentally, I suspect the appeal of the railgun is similar to the appeal of a Space Elevator... if you can supply the fuel/energy from the ground, rather than having to pay to lift a few thousand gallons of rocket fuel mass into the air, that's a big win.

Re:Finally...

[DerekLyons]

he basic problem with a railgun is that it give only a fraction of the velocity required - and it does so only in one plane.

Maybe I'm missing something, but can't you point the railgun in any direction you want? Granted it's probably cheaper to run the track along the ground, but you could at least in principle aim it straight up, or diagonally, or any other direction..

It doesn't matter *where* you point it - you cannot reach a stable circular orbit with a single impulse from the Earth's surface, only an (unstable) elliptical orbit. You'll always need a rocket stage to convert that elliptical orbit into a stable circular orbit.
 
You can change the size of the required stage by altering your launcher systems's angle, but at the cost of vastly increasing the cost of your launcher system.

Re:Finally...

[Jesus_666]

Note that the railgn in this design is not supposed to impart significant velocity to the craft. It's just supposed to et the craft to a speed where scramjets can become operational. The scramjet-powered "first stage" then takes the craft to "the upper reaches of the atmosphere" where a more conventional rocket stage takes over.

Now, I'm not an expert but to me it seems like they're trying to create a more easily reusable first stage, using the railgun as little more than an ignition helper.

Re:Finally...

[DerekLyons]

Now, I'm not an expert but to me it seems like they're trying to create a more easily reusable first stage, using the railgun as little more than an ignition helper.

Even so, you still have massive impacts on the booster in the form of the structural reinforcement that will be required, additional insulation, etc... etc... The sums still don't add up.

jellied brains

[FranTaylor]

Oh the acceleration! Hopefully this is not for manned flights!

Re:jellied brains

[Anonymous Coward]

This might blow your mind...

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

I just wonder what kind of sonic boom would result from a Mach 10-25 flight, or if they are planning on building this up a mountain. And if you build a longer track, you have lower G-forces.

And I wonder if the mag-lev tech would be good enough to accelerate a lot of weight, or if they would still need booster rockets. Interesting concept, and it could make space travel quicker.

Re:jellied brains

[ISoldat53]

Sounded like they are planning on building it at the Cape Kennedy launch facility.

One faster

[Anonymous Coward]

Well you could you know, make it one faster, you know go up to Mach eleven. Well, it's one faster, isn't it? It's not ten. You see, the Russians, you know, will be launching at Mach ten. You're on Mach ten here, all the way up, all the way up, all the way up, you're on Mach ten on your magnetic sled. Where can you go from there? Where? Nowhere. Exactly. What we do is, if we need that extra push over the cliff, you know what we do? Mach Eleven. Exactly. One faster.

Re:One faster

[7-Vodka]

It's funny, but I feel like I'm missing a reference.
What am I missing?

Re:One faster

[anonymousNR]

mach 5 reference

When Worlds Collide

[hodagacz]

I guess George Pal got it right.

A rail gun accelerating objects to mach 10

[Just_Say_Duhhh]

built alongside the crawlerway? Just when I thought real estate prices in the Space Coast of Florida couldn't drop any lower, now we have sonic booms being generated at ground level just a couple miles from Merritt Island and Cocoa Beach.

In related news, I just opened "Space Coast Window Repair."

Put the railgun in orbit

[mangu]

Sorry, but 10x roller coaster speeds isn't close to Mach 10.

And even Mach 10 isn't enough, orbital velocity is close to Mach 25. You cannot run at that speed inside the atmosphere, there's no material that could withstand the heat.

I've seen a much better idea proposed. Put that electric accelerator track in orbit. The energy needed to reach orbital altitude is much less than the energy needed to accelerate to orbital speed.

One could launch the spacecraft vertically to an interception with the accelerator track, then it would catch the track and get the needed horizontal speed while already outside the atmosphere.

Re:Put the railgun in orbit

[metrometro]

TFA suggests that the Mach 10 will be to get some scramjets online, which will then boost to high atmosphere, and then pop out a small second (third?) stage rocket.

Re:Put the railgun in orbit

[Just_Say_Duhhh]

But when you catch the "track" to gain orbital velocity, wouldn't that just decay the track's orbit? You'd have to keep adding energy to the "track." I thought the rail gun concept was trying to avoid having to generate all that energy in space (thereby avoiding the need to launch all that extra weight)?

Re:Put the railgun in orbit

[mangu]

But when you catch the "track" to gain orbital velocity, wouldn't that just decay the track's orbit?

Sure, but you would also use the track to decelerate spacecraft from orbital velocity to land on earth, which would cause the track to gain velocity.

Re:Put the railgun in orbit

[X0563511]

... in which case Newton's Laws would adequately describe the reasons why your ultra-expensive orbital mass driver is now an ultra-expensive meteor shower.

Re:Put the railgun in orbit

[X0563511]

(realized i should explain for those that don't get it)

The force applied to the craft by the accelerator will also act against the accelerator. Firing the right way, it would drop the accelerator right out of orbit (it would impart it's velocity into the craft, leaving it with less than needed to maintain orbit, crashing down). Fired the other direction, and the exact reverse would be seen - the accelerator would "push" off of the craft, accelerating and gaining altitude, but the craft would then fall quite ungracefully.

Re:Put the railgun in orbit

[Kilrah_il]

OK, so it's a one-time use accelerator, but it's still good, nay?

Re:Put the railgun in orbit

[Anonymous Coward]

Do you seriously have only a small iota of critical thinking skills?

Think about it for one second. You do not need to do all of your acceleration to Mach 25 on the track. You accelerate to Mach 10 and then the vehicle is released, and it is carrying additional propulsion which then takes it into orbit at the needed velocity.

Your proposal sucks compared to what is brought up in the article (no surprise, space scientists versus internet poster). There is so many fundamental things wrong with putting an electrical accelerator track into orbit to help space craft launch.

First: If the track is to be in orbit, the track itself must have a orbital velocity. Therefore to 'catch' the track as you say, the space craft must be going faster than it. The space craft will then have orbital velocity by the time it catches the track. Since the point of the track is to accelerate a vehicle to orbital velocity it is no longer useful in this position. Even if you have the track catch the vehicle, it doesn't make any sense. Consider the deltaV between the shuttle and the ISS when it docks. There is not much of a difference.

Second: Since the initial idea sucks since the track makes itself obsolete, lets consider that the track is a staging point to go from orbital velocity to a planetary exploration path. However, this idea also sucks. The track itself will probably be light. All you need is some rail, power supply/generation, and energy storage (probably some gigantic capacitors). It also needs to be light (low mass) to actually be built in space, because heavy stuff in space is incredibility expensive. This means that when your spacecraft is launched on the rail, the rail gets rocketed in the opposite fucking direction. Oops! For example, the ISS, the biggest thing we've ever built in space, and the MOST EXPENSIVE THING humans have ever built by a FACTOR OF 10 over then next expensive item, weighs 820,000lbs. Which sounds like a lot until you see that the space shuttle orbital vehicle weighs ~240,000lbs.

Re:Put the railgun in orbit

[BJ_Covert_Action]

Well that might defeat the purpose of such a system. The whole idea behind rail launching anything is to make launches cheaper and simpler. Having to use a rocket stage, to get to low orbit, to rendezvous with an orbital track, to propel a vehicle to its intended orbit probably doesn't match either of those criteria. Besides, the assumption that we would be launching from a track surrounded by atmosphere is pretty unimaginative. The way I see something like this working would involve building more of a tube than a track. Keep the vehicle suspended in the tube using a crapton of really big magnets. Keep the tube vacated of any and all atmosphere (keep it near vacuum). Fire up concentric rings of more magnets that would steadily push the levitating vehicle forward in the tube faster and faster. Ensure that the tube is long enough to get the acceleration and velocity necessary to reach a decent LEO parking orbit and there you have mankind's very first spacegun. Now, would this project be simply or easy? Not at first, no. But if we start doing research with high speed track systems, and taking data regarding the very same aero forces that you mention now, then a few decades down the line we might be better suited to build a spacegun off the coast of California...or wherever.

Re:Put the railgun in orbit

[Somegeek]

How does something going 7 km/sec catch something going zero?

Colliding, I can see. Gently catching and accelerating up to the same speed, I don't see.

Re:Put the railgun in orbit

[mangu]

to 'catch' the track as you say, the space craft must be going faster than it

No. All they need to do is to be at the same place at the same time.

The spacecraft is at the top of its trajectory, zero vertical speed, zero horizontal speed. Exactly at the same time the front of the track reaches that same location. A magnetic force catches the spacecraft so it won't fall down. The same magnetic force accelerates the spacecraft horizontally along the track so it will have orbital velocity by the time it reaches the other end.

The track is bidirectional. It propels spacecraft launched vertically from earth, but it also catches spacecraft coming down. There's a velocity budget to be maintained, it will drop material from orbit to keep its velocity. Where will this material come from? The moon, perhaps. We will have to import mass to the earth as we send mass up.

Of course, the track must be more massive than the spacecraft it will handle. Version 1.0 will not be able to handle manned spacecraft.

Re:Put the railgun in orbit

[qzjul]

Not if the track was a GIANT ring around the whole earth :) Then it would just rotate!

Re:Put the railgun in orbit

[mangu]

The problem with your idea is that the mouth of the tube should be open, otherwise how would the spacecraft come out? To be open it should need to be in a vacuum, otherwise air would come rushing in. You would need a tube extending all the way to above the atmosphere, let's say a hundred kilometers up.

An awesome concept, but not simple or cheap.

Re:Put the railgun in orbit

[Anonymous Coward]

So sorry, but what about Newton's Law of opposite and equal reactions?

From how I see it, on earth, the earth's mass would absorb the reaction. However, in space, your projectile would go one way and your space gun would go the other, with their velocities being a function of their respective masses.

However I must warn you, I am not a physicist.

Re:Put the railgun in orbit

[SleazyRidr]

You just blew my mind.

Re:Put the railgun in orbit

[AshtangiMan]

You're forgetting that we could just slingshot around the sun. I've seen it in the movies and it works all of the time. After the slingshot maneuver, the velocity would be high enough to catch the track, which further accelerates the payload. The track probably has to then slingshot around the sun too, but these are just details to let the engineers figure out. Visionaries like me and the GP can then move on to better problems. Currently I'm working on a way to speed up my commute by slingshotting around the beltway.

Re:Put the railgun in orbit

[BitZtream]

And even Mach 10 isn't enough, orbital velocity is close to Mach 25.

At what distance from the Earth?

Orbital velocity is entirely dependent on your distance from the gravitational source and its gravitational pull.

You already have 'some' orbital velocity just standing on the planet, in fact, you have enough to orbit if you go far enough away from the planet, though it wouldn't probably last very long.

Re:Put the railgun in orbit

[Anonymous Coward]

No. All they need to do is to be at the same place at the same time.

The spacecraft is at the top of its trajectory, zero vertical speed, zero horizontal speed. Exactly at the same time the front of the track reaches that same location. A magnetic force catches the spacecraft so it won't fall down. The same magnetic force accelerates the spacecraft horizontally along the track so it will have orbital velocity by the time it reaches the other end.

The track is bidirectional. It propels spacecraft launched vertically from earth, but it also catches spacecraft coming down. There's a velocity budget to be maintained, it will drop material from orbit to keep its velocity. Where will this material come from? The moon, perhaps. We will have to import mass to the earth as we send mass up.

Of course, the track must be more massive than the spacecraft it will handle. Version 1.0 will not be able to handle manned spacecraft.

So wait, you propose that the track and the space craft meet at a delta V of Mach 25? You see no problem with this? Have you ever rode the shinkansen? You know how much power goes into that thing? I mean I guess it could work if your space craft was a pea size slug of metal.

Re:Put the railgun in orbit

[mangu]

So wait, you propose that the track and the space craft meet at a delta V of Mach 25?

Welcome to the world of engineering.

Re:Put the railgun in orbit

[ravenshrike]

Is someone producing lead spaceships that I don't know about? Any slingshot maneuver that would return the craft to earth in a remotely expedient matter would fry the occupants.

Re:Put the railgun in orbit

[crafty.munchkin]

worst. game. ever.

Re:Put the railgun in orbit

[Anonymous Coward]

Take a very quick look at the length of the track required to accelerate it to orbital velocity and you'll see hey this is incredibly impractical. Even assuming a 10G acceleration you'll need a track several hundred kilometers long.

In orbit. Intercepting a multi-tonned (manned?) vehicle. With small tolerances (otherwise the magnetic fields would have to be enormous). At a closing velocity of 5 miles per second.

There's a reason why NASA is only proposing to accelerate vehicles to 600MPH. Otherwise the track length would be prohibitive.

Re:Put the railgun in orbit

[Neil Boekend]

Yes. And if Spock's educated guess is correct you should even travel back in time!

Re:Put the railgun in orbit

[Vectormatic]

how about having the tube behind the craft pressurized? the pushing force of the air behind the craft should (over)compensate for the air resistance on the front of the vehicle, sort of like a crossbreed between a normal powder-rifle and a gauss-gun...

it would need some rather extreme pressure tanks / explosive / reactant for this trick though

Re:Put the railgun in orbit

[dwinks616]

The point of having it evacuated is to avoid air resistance. Every last bit of energy lost to air resistance is energy gained in heat.

Re:Put the railgun in orbit

[Vectormatic]

hmm, true, i hadnt considered the heating effect, merely the braking effect..

Re:Put the railgun in orbit

[imakemusic]

Unless I'm missing something Newton's third law means that, because the accelerator is not attached to anything, it would be pushed in the opposite direction from the direction of the craft. In effect part of the energy exerted would push the craft up and part of the energy would push the accelerator down. You would effectively get much less force than you would if the accelerator was attached to the ground. Unless, maybe you hang it from the moon by a piece of string...

Re:Put the railgun in orbit

[ResidentSourcerer]

So you speed up the spacecraft and slow down the railgun.

Back to the drawing board.

Hmm. I guess if the railgun has enough umph, you could accelerate some mass the other way.

Good Now you have things in the same orbital plane, going in opposite directions.

Back to the drawing board.

Ok, for the railgun to gain momentum again, you accelerate a smaller mass, but send it at greater than earth escape velocity.

But it's still in solar orbit, in one that will eventually come close by again. Can we keep track of a few zillion of these 10-30 km/sec objects?

Back to the drawing board.

Ok, when we de-orbit, we also use the railgun. This way we drop the rocket straight down. If we drop as much mass as we orbit, the railgun averages out.

Oh joy. Drop straight down from 150 km up. And just how do we dispose of that energy. Remember that half the air that you will use for braking is below 18,000 feet.

Back to the drawing board.

Sigh.

Re:Put the railgun in orbit

[GooberToo]

I think its wonderful that someone who clearly didn't read the article and made a nonsense comment based on a lack of knowledge gets moderated, "insightful". I would like to subscribe to your news letter. Obviously I won't actually read it, but when I comment on random topics after receiving your news letter, I presume others will believe me to be extremely insightful.

I'm honestly not sure which is worse, your "best effort" comment or the "best effort" moderator.

Re:Put the railgun in orbit

[X0563511]

You would have to put the object into a ballistic path that meets at vectors as close as possible. Of course, you still have the issues I outlined above, in addition to dealing with the object not dragging it right back down on it's ballistic.

Mach 10

[rbanffy]

So, the rail takes the x-43-like launcher to 600 (10x60) mph? That's not nearly enough to ignite the engine. Assuming it gets 5 times as fast (3000 mph should be enough to ignite it) it will be very close to the ground. 3000 mph close to the ground must generate non-trivial amounts of heat (and broken windows). Ignore that (because the launcher appears to have SR-71-like engines) for a moment and imagine the launcher now has to propel itself to the upper atmosphere, where it reaches Mach 10 (something we never did on an air-breathing engine) points itself upward (perhaps getting rid of more atmosphere) and launches the expendable stage. The launcher then glides back to the ground and lands safely.

Am I the only skeptical one here?

I am glad NASA is thinking on stuff, but, seriously, they could as well think about viable stuff. They don't need milestones like these - they need, as one expert once said, "inchstones".

Re:Mach 10

[qzjul]

Mach 1 == 1,236 kilometres per hour (768 mph) (at sea level I presume)

Mach 10 -> 12,236 km/h or 7680 mph


Somewhat faster than the 10x60; (yes I realize TFA said something about 10x60mph)

Payload Weight

[decipher_saint]

I have no idea how heavy the Shuttles (or Soyuz capsules for that matter!) are even without the massive fuel tanks/rockets but I imagine this will take a lot of energy to get the job done.

I think it's a great project for two main reasons:
1. Figure out how to generate and store a big chunk of energy.
2. Use it to accelerate and object to escape velocity.

There is so much potential for discovery in both areas it boggles the mind.

If they're launching horizontally...

[jenningsthecat]

...then by definition they're launching at a tangent to the earth's surface. This means that they'll have to punch through a lot more atmosphere than they would have to with a traditional perpendicular launch. I wonder how much they're really gaining with this strategy.

Re:If they're launching horizontally...

[vlm]

...then by definition they're launching at a tangent to the earth's surface. This means that they'll have to punch through a lot more atmosphere than they would have to with a traditional perpendicular launch. I wonder how much they're really gaining with this strategy.

Since they are depending on a miracle occurring in engine technology, maybe they are expecting an equal miracle to occur in wing technology, to get a high mach number wing with a slow glider like lift to drag ratio so they can pull up at the end of the launch rail thing. Piling on that many pipe dreams, they may as well ask for a flying unicorn.

Re:If they're launching horizontally...

[Anonymous Coward]

Because it it would be so fucking hard to curve the very end of the ramp upwards? Typical designs for such launchers (whether cannon, ram accelerators, linear motors (like this one), scramjets, whatever) usually go for about 20-30 degrees exit angle -- but by doing the bulk of the acceleration horizontally, and only curving the end up, you don't have to build a mile-long gun barrel suspended in the air at a 30-degree angle.

And yes, they still have to ballistically punch through a motherfucking ton of atmosphere -- these kind of launchers always benefit from being built at the highest altitude you can manage (subject to having a large enough flat(ish) stretch to build it, and logistics of delivering payloads and supplies to the launch site).

Please, before anyone else makes an ass of themselves with retarded assumptions, could you just go to tbfg.org and fucking skim some of their papers? It's just possible that, even if this isn't rocket science, some rocket scientists might have given it a little more thought than you have in the ten minutes since you saw it on slashdot.

Re:If they're launching horizontally...

[strack]

you have absolutely no idea what your talking about. the thing will be going at at least mach 1 at least when it leaves the rail. it dosent need that much wing at that speed to stay aloft. the only reason airplanes have large wings is so they can get off the ground at the low speeds nessecitated by runways. nevermind the fact that it will also be accelerating quickly up through the mach numbers. and what, you cant angle the track upwards? like up the side of a mountain perhaps? as for a miracle in engine technology, the x-51 has sucessfully demonstrated the required scramjet technology already. tadaaa.

Re:If they're launching horizontally...

[Muad'Dave]

If you curve up the last 1/10th mile of the track in a circular shape with the end of the track at a 30 degree angle to the ground, you'll pull just shy of 24 g's transiting the curved part at 600 MPH (=880 fps) for 0.6 sec. The end of the track would be 135 ft in the air.

Assuming the highest safe track height to be 200 feet, you'd have to curve the last 782 ft of track, which would exert 16 g's for a 0.89 second.

If you curved the last mile up at 30 degrees (assuming you could make 600 MPH in the first mile), you'd only get 2.39 g's for 6 sec, but the track would be a whopping 1351 feet in the air!

Naturally higher angles would be worse - if you wanted to go straight up, the last 1/10th mile scenario would result in 72 g's for 0.6 sec and a ramp height of 336 ft.

Re:If they're launching horizontally...

[vlm]

you have absolutely no idea what your talking about.

Obviously. I only know L/D ratios always decrease with vehicle speed.

Fast enough to reach orbit is...

[gurps_npc]

fast enough to kill a human. I may be mistaken, but I am pretty sure that is the case. Current fighter pilots reach speeds high enough to black out (and/or red out). At said speed, they can't reach orbit. I can see no way for us to create a purely (or even mostly) land based launch system to supply enough energy in a short period of time to reach escape velocity. Not even if you built it on the Tibetan plateau that reaches 5000 meters above sea level.

To keep the human alive, we need a slower, longer burn, which requires an engine on the craft, not on the ground.

Re:Fast enough to reach orbit is...

[tibit]

You black out when you fly a curved path -- that's the only way to generate sufficient accelerations. To merely fly fast, all you've got is the mass of the aircraft (and your butt) counteracted by the engine thrust. Gives a nice buttkick, but not nearly enough to cause any distress.

The fighter pilots black out when they make turns, and for that they don't need to fly fast at all. You can easily black out on an aerobatic biplane with a prop engine.

Re:Fast enough to reach orbit is...

[SteveAstro]

SPEED doesn't kill you, acceleration might. Bear in mind you are currently moving at at least 1000 MPH.

Re:Fast enough to reach orbit is...

[Anonymous Coward]

Intertial dampers, fool!

Re:Fast enough to reach orbit is...

[Anonymous Coward]

deceleration will.

Re:Fast enough to reach orbit is...

[Anonymous Coward]

Everyone know these things are only good for shooting giant robots off the top of pyramids.

Sci Fi had it first

[Anonymous Coward]

About damn time. Heinlein suggested it, the US has been capable of it for 40 + years. But I guess a rut is a rut.

What about launch loops?

[postermmxvicom]

If NASA starts looking at alternatives, I'd be interested in what they say about Launch loops. They always looked cool to me. Maybe one day NASA will look at those also?

Re:What about launch loops?

[robot256]

So we have a 4000-mile long rubber band zinging above our heads at 18,000 mph? What happens when it snaps?

Are rail guns like lasers

[SnarfQuest]

re rail guns enough like lasers that they need shark keepers?

Why at sea level?

[Anonymous Coward]

Why would they do this at sea level? This should be done somewhere in the American West, at altitude. At 10K feet there is a heck of a lot less air resistance. Could be done on one of the Air Force ranges for sonic boom sake.

Re:Why at sea level?

[istartedi]

I was thinking this too. Edwards AFB maybe? Hmmm... only about 2500 ft apparently. We can get to 5000 feet easily on a lot of places out west though, and I'm sure the military already controls a lot of flat land at that altitude or greater. 10000? I don't think you can do that without the extra hassle of building on very steep land.

Re:Why at sea level?

[Neil Boekend]

Mt. Whitney is 14k5 feet and fairly close to the equator. Closer to the equator means less fuel required to move to a geosync orbit and more speed due to the rotation of earth. The angle of the slope can be used to gain initial altitude AND orbital speed so the steep land actually helps.

Re:Why at sea level?

[istartedi]

Common sense may not apply in this situation. Fighting gravity up a hill might be more costly than shooting out at a slight angle and using aerodynamics to vector up. I was thinking more along the lines of construction costs than operational costs. You can't just drive a backhoe up there.

Mt. Whitney is not a candidate because AFAIK, it's in a national park. Such construction would be fought tooth and nail. It may or may not be legal without an act of Congress. More time. More money.

If altitude+equator is the dominant term in the operational cost equation, then the US is at a disadvantage. The Himalayas make Mt. Whitney look rather wimpy.

I think it's pobably outside both our knowledge domains to make a call on this, unless you actually authored a well-researched report, with actual calcs of construction costs for various scenarios, operational savings, and the time to recoup the increased construction costs due to better operational efficiency.

Of course, if the government does it, some political concern will probably cause them to do it a dramaticly higher construction AND operational costs. Senator from $BadLocation will bring the pork to his state.

Re:Why at sea level?

[Neil Boekend]

I think it's pobably outside both our knowledge domains to make a call on this, unless you actually authored a well-researched report, with actual calcs of construction costs for various scenarios, operational savings, and the time to recoup the increased construction costs due to better operational efficiency.

Nah, they shouldn't follow us blindly. That's all. We can talk about it and feel superior when we guessed correctly of course.

Friction?

[MaWeiTao]

I'm a complete layman here, but it seems to me that friction from air would be a serious problem at the speeds a vehicle would have to be propelled off this launcher. By the time conventional rockets have achieved a significant speed they're already fairly high in the atmosphere. I can't see a launch tower being practically ramped up high enough to overcome these effects. The vehicle would have to survive the stresses of heat and friction at launch and reentry. There's also the matter of drag kicking in before the second rocket fires. And I suppose another question is how many Gs would be placed on a vehicle using this method compared to traditional launches. This sounds comparable to firing a bullet from a gun which seems like it would be a rather violent launch.

Maybe it's all a non-issue. On the surface it seems really neat.

Re:Friction?

[ScrewMaster]

This sounds comparable to firing a bullet from a gun which seems like it would be a rather violent launch.

Depends. If you used a linear accelerator (e.g. a mass driver) of sufficient length, you could accelerate at one G. You'd probably want more than that, though, to keep the size of the launcher manageable.

That's so 1980's....

[Jedi Holocron]

I guess it's Back to the Future...or is that Past...

This kind of

[Anonymous Coward]

splitting annoys the hell out of me

Old idea, see "The Moon Is A Harsh Mistress"

[Anonymous Coward]

by Robert Heinlein

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

It's a real shame the government is so darn corrupt, incompetent and shortsighted or we'd probably have this level of technology already. Oh well, I guess mansions and yachts for playpeople are far more important.

The NASA version

[PagosaSam]

"Emerging Technologies May Fuel Revolutionary Launcher"

It looks more like the rail truck accelerates the launch vehicle to mach 1 which leaves the end of the track and the scramjet lights and carries it and its payload to mach 10 at about 20 miles altitude. The payload then separates from the launcher, the rocket ignites and sends the payload into orbit. The launch vehicle returns and lands for reuse.

This sounds a lot more feasible than a mach 10 rail gun!

Great idea

[Thagg]

I agree that this idea has been around a while -- it's still a great idea.

Scramjets are really pretty simple devices compared to rocket engines. This machine would be like the first and second stages of a three-stage rocket, saving something like 80% of the mass. (OK, most of that mass is relatively cheap kerosene and LOX, but still.) Getting a sled up to Mach 1 to get the scramjets started is really not that challenging. If they don't start correctly, you just slow down ... and nothing bad happens.

One thing that people don't point out is that if somebody built this, and it worked as well as it appears, then they would have a huge leg up in the further development of space. You might well have, say, Puerto Rico building the guideway in order to bring development money to the region.

The Plan is Not Mach 10 on the Track!

[Somegeek]

Everyone is banging their head over trying to hit Mach 10 on the track.

TFS and everyone else is misunderstanding the proposal.

The current idea is for the sled on the track to accelerate a scramjet up to about 600mph, then the scramjet lifts off, flies up to altitude and at about mach 10, releases a rocket which boosts the payload into orbit.

Sled (reusable) on the ground = 1st Stage
Scramjet (reusable) in the atmosphere = 2nd Stage
Booster Rocket in space = 3rd Stage

All extensions of more or less current technology.

Re:The Plan is Not Mach 10 on the Track!

[Anonymous Coward]

Here is the the link.

Re:The Plan is Not Mach 10 on the Track!

[strack]

even if the plan was mach 10 on the track, rocket sleds achieve mach 8.5 on tracks on the ground already.

Re:The Plan is Not Mach 10 on the Track!

[dargaud]

Sled (reusable) on the ground = 1st Stage ... All extensions of more or less current technology.

For those who haven't seen this video of the land speed record on a sled at an unbelievable 2884m/s (yeah, that's over Mach 8!)

A fatal flaw in the ointment

[Anonymous Coward]

is the sonic boom this launcher would produce. Remember the 1970s-era SST that was scrubbed mainly due to this problem, and the SST was only a Mach 2-3 airplane. I would rather not think about the sonic boom that a ground level Mach 10 launching would produce.

Physics 101 answers

[Anonymous Coward]

For mach 10 you can pull 4G's for 256km or 16G's for 64km or 64G's for 16km or 256G's for 4km

*then* you need to worry about aerodynamic and separation stresses at Mach 10 at ground level.... yeah.

Still the Shuttle at MaxQ is only around Mach 2 at 35,000 ft....(~9000m)

At 4G's (manrated) Mach 10 would take 256km -- or Mach 2 (Max Q anyone?) at 16km.

Maybe you could build it near Leadville, CO (3,094 m) -- the NIMBY's will *love* you.

NOT A Railgun

[Anonymous Coward]

TFA title is wrong. Bad journalism. Sensationalist title. This is not a railgun, this is a linear induction motor. Yes, they're right, they are used for amusement rides.

Spinal Tap

[FiloEleven]

The bit in question.

I, on the other hand, knew the reference but feel like I'm missing the humor.

Bad Physics

[sjbe]

Anyway, the other think to consider (especially for things like laser-based launches) is that the current "spit out a ton of speed really quickly and then coast your way to orbit" approach really sucks.

Why on earth was this moderated interesting? Is wrong information interesting now? You can't coast to orbit. When the power shuts off you either are in orbit or you aren't. Gravity doesn't take a holiday just because you are out of propellant.

Even a slow nice steady boost will get you to orbit without needing to hit escape velocity.

You can't get into orbit without hitting escape speed (escape velocity is actually a misleading term because it is a scalar). Escape speed doesn't have to be fast (in fact it can be any speed) but again, once the engines shut off you had better be at the escape speed necessary at that altitude or you will fall back to earth.

If a slow steady boost was practical, we'd be doing it. Rocket scientist is a synonym for smart for a reason. We lack the technology to escape earth's gravity well slowly in an economically practical way. I'm not even sure we could do it at all with our current capabilities, but I am sure we can't (yet) do it cheaply.

Re:Bad Physics

[EvilDroid]

Yes, speaking of bad physics, why can't you coast to orbit? If an object at 10 ft altitude is moving at a high enough velocity, it sure as hell is going into orbit unless something gets in its way, without any additional propellant.

Re:Bad Physics

[FatLittleMonkey]

(Since you replied late, I assume you won't mind an even later reply.)

If an object at 10 ft altitude is moving at a high enough velocity, it sure as hell is going into orbit unless something gets in its way, without any additional propellant.

...with a perigee 10ft above the ground.

Probably less. When you turn off your propulsion the maximum perigee is your current height. And then only if your velocity is horizontal to the ground; if you're angled upwards (and you will be), perigee is even lower than your current altitude.

At that point, you are in a nominal Hohmann tranfer orbit. But if you don't do an orbital burn at apogee, you will continue back down to perigee (hitting the atmosphere and/or ground first. Hence the "nominal".)

So the railgun payloads have to have a smallish rocket engine to normalise/circularise their orbit. And that rocket (and associated gear) has to survive the railgun's acceleration. Not impossible, but it means you are not just launching "dumb" payloads.

(Assuming velocity is below escape. Coz I'm assuming you weren't just being a pedantic dick.)

Apologies to Douglas Adams

[sjbe]

Ignoring gravity works when you run off the edge of a canyon or your ACME rocket runs out of propellant. You don't fall until you actually look down and remember gravity.

The real trick is to throw yourself at the ground and miss...

Quicklaunch Inc

[Anonymous Coward]

While NASA is busy trying to come up with a way to spend a bunch of money on a boondoggle: John Hunter is moving NOW.

http://www.youtube.com/watch?v=1IXYsDdPvbo

Rail Guns haven't accomplished nearly the speeds of hydrogen gas guns which have lower maintenance costs. Their disadvantage is incredibly high G forces in contrast to rockets or rail guns, but that isn't an issue for launching fuel and supply's to an orbital depot, and robots can handle it.

The ONLY way that humanity is going to see a man on Mars or Venus this century is if they stop treating cargo with the same soft touch humans require to stay alive.

Getting humans in to space and getting liquid fuel in to space are two very seperate problems, and the fuel expense of treating inanimate objects like they were G-force sensitive humans is immense.

As far as I can tell: the only reason space guns were abandoned in favor of rocket technology was because rockets had more military strategic value, and because rockets can transport humans safely.

Does your car's gas tank have air conditioning and a seat belt?

Not a Rail Gun

[florescent_beige]

The rail gun aspect to this is a red herring.

The track is used to accelerate the craft to ramjet speed so it can fly.

Fun fact about rail launchers: to get to LEO speeds, limiting acceleration to 3g's in case you want to carry people, you need a launcher 800 km long. You would probably want the launcher to be inside an evacuated tube to cut down on air resistance and aero heating, but you still might have the problem of exploding once you exit the tube and hit the atmosphere.

This proposal of NASA's is just an flinger to get a ram/scram jet up to ram speeds. You could make a simpler engine that way, you wouldn't have to include turbines to accelerate from a standstill, something ramjets don't do.

Answers are incorrect because ...

[dbIII]

You've got the wrong assumption for a maximum speed there.
The railgun is to accelerate to a speed where a scramjet kicks in.

Hyshot kicked in around mach 7 but it's minimum speed would be lower (I think there were mach 5 shock tunnel tests with ignition but can't remember, but I know mach 6 scramjet ignition was happening 23 years ago).
As for getting from there to mach 10, X-51 got up to mach 9.6 in ten seconds. I don't know what speed it ignited at.
That's still a big track but shortens it to easily fit in Texas :)

Aim for mach 4 (and typo above)

[dbIII]

Apparently X-51 is designed to ignite at mach 4, so that's the speed the railgun has to reach with current scramjet technology.
I made an error above, it was X-43A that got to mach 9.6 in ten seconds.

Duh!

[crhylove]

I've been saying this to friends and family for years.

Of course, actually BUILDING the fucker....

Even closer to the concept...

[Anonymous Coward]

Fireball XL5 demonstrated its application in the early 60s!

Fireball XL5 entry

It's not velocity that kills you.

[Ihlosi]

fast enough to kill a human. I may be mistaken, but I am pretty sure that is the case.

It's not. Velocity doesn't kill, but excessive velocity changes do. Keep dv/dt within certain limits, and a human will be fine all the way up to a fraction of c.

Probably been done already...

[Anonymous Coward]

But I suppose that gives new meaning to the phrase "running someone out of town on a rail"

getting images

[Anonymous Coward]

from Indiana Jones and the Crystal Skull

Also Concorde Replacement

[Tekfactory]

Unless I missed something, 600 MPH in 2 miles is just a hair over 1G, perhaps there is some dual use planned for the research. If you can get the Mach 10 part out of the Scramjet consistently and keep the Gs low, it wouldn't make a terrible Singapore, Australia, New Zealand shuttle.

Journalists can't convey simple ideas.

[trout007]

I took a look at the actual proposal. The launch speed off the rails is about Mach 0.5-1.5. The purpose of this test is to try different speeds. The rail is the "first stage". If the Mach 1.5 can be achieved than the second stage would only need a ram(Mach 1.5-4) /scram(Mach 4-10) jet for the second stage. This would be reusable. The third stage would be capable of orbital insertion. What this system allows is the use of an air breathing second stage without having to have a rocket to get it up to the speed that a Ramjet needs to operate.

Hint from Anime

[Anonymous Coward]

Yeah but going mach 10 at ground level isn't exactly rainbows and ponies either...

I recently saw an anime that used a rail launch system and they used a rocket assisted ice bullet to break the Mach and create a slip stream in front of the launching craft. Air friction would rise enough to melt the ice then the launcher would return. I'll see if I can find the name of the anime later today.