VASIMR Plasma Thruster To Be Tested Aboard ISS

Toren Altair brings news that NASA and the Ad Astra Rocket Company finalized a Space Act Agreement earlier this week to test the Variable Specific Impulse Magnetoplasma Rocket (VASIMR) on the International Space Station. The agreement hinges on a series of requirements for the thruster's performance and efficiency in ground-based tests. "The primary technical objective of the project is to operate the VASIMR VF-200 engine at power levels up to 200 kW. Engine operation will be restricted to pulses of up to 10 minutes at this power level. Energy for these high-power operations will be provided by a battery system trickle-charged by the ISS power system. These tests will mark the first time that a high-power, steady-state electric thruster will be used as part of a manned spacecraft." Reader clarkes1 points out related news of a runway trial for Virgin Galactic's WhiteKnightTwo, the mothership that is designed to carry SpaceShipTwo from the ground to 50,000 feet. A very brief video shows the oddly-shaped plane moving down a runway under its own power.

Comments

Nice acronym

[Concerned Onlooker]

Oy VASIMR...

Bugger that namby pamby stuff

[David Gerard]

Just give 'em gigantic pounding thrust, none o' this wussing about with plasma. OXYGEN AND KEROSENE. It was good enough for Wernher von Braun!

Re:Bugger that namby pamby stuff

[Anonymous Coward]

Pfft, specific impulse wins once going further than orbit. Suck it V2!

Re:Bugger that namby pamby stuff

[Titoxd]

Um... yeah, right.

If you want to do any deep-space maneuvers, you have to carry all that liquid propellant (be it LO2/LH2 or LO2/RP-1, for the rocketry equivalent of a gas guzzler (specific impulse of 200-500 s), instead of carrying a small amount of high-efficiency propellant with a specific impulse of up to 10000 s.

VASIMR and the like won't get you off the ground, because their thrust-to-weight ratio is less than one--meaning they can't beat the force of gravity here on Earth. But once in space, if you're going far, their performance characteristics mean that you can sometimes get to your destination faster and cheaper than you can with ordinary impulse-maneuvered chemical rockets.

Re:Bugger that namby pamby stuff

[Anonymous Coward]

As far as concepts go, you pretty much can't get more gigantic pounding thrust than Freeman's.

Re:Bugger that namby pamby stuff

[Mr. Bad Example]

> Just give 'em gigantic pounding thrust

It's what keeps the ladies coming back!

Re:Bugger that namby pamby stuff

[Anonymous Coward]

Projected is 30000s specific impulse when fully powered. 10 times that of the average jet engine.

Re:Bugger that namby pamby stuff

[Anpheus]

Real men, not like Wernher von Braun, simply hitch a ride on a cannonball to their duration.

Baron Munchausen would have a lot to teach you kids.

Re:Bugger that namby pamby stuff

[Anonymous Coward]

Ya don't need any gigantic thrust for something like the ISS that is just going in circles. The VASMIR on the ISS is just being used to counteract atmospheric drag.

Re:Bugger that namby pamby stuff

[KozmoKramer]

Get your ass to Mars,Get your ass to Mars,Get your ass to Mars, Get your ass to Mars....

Re:Bugger that namby pamby stuff

[sketerpot]

Real men are idiots. Wernher von Braun would be smart enough to know that a dude riding a cannonball would need to do a burn around the time he reaches apogee in order to move into a stable orbit. Your cannonball still needs to have rockets on it.

Re:Bugger that namby pamby stuff

[Anonymous Coward]

Don't you talk about the Baron like that! He'd find a way to do it! He'd get Adolphus to fire a shot at just the right time while Berthold spun the cannonball and would meet up with the King and Queen of the moon just like that!

Don't listen to him, Baron! We believe in you!

Re:Bugger that namby pamby stuff

[Mista2]

My goodness, electric thrusters, space stations, private spaceflight and the Martin jetpack. You could almost start believing we are finally living in the 21st century! But where is my flying car damnit!

Re:Bugger that namby pamby stuff

[Anonymous Coward]

its good, but not enough..

imagine the horror of an oxygen crisis (in contrast to our oil crisis) when we start burning up oxygen in large quantities

Re:Bugger that namby pamby stuff

[aqk]

Phooey on yooey, you humourless nerd!

We repeat:

Just give 'em gigantic pounding thrust [today.com], none o' this wussing about with plasma. OXYGEN AND KEROSENE!

Werner knew best! It's the American way! Dammit, just ask any American automobile company!

Nice, but...

[orkybash]

Where's the ommminous hummmmm?

white knight 2 looks too fragile

[theshowmecanuck]

Maybe it is strong enough, but with the only join between the two hulls being a wing, I don't think I would want to travel in it or under it. Reminds me of something I heard in a documentary about the competition for for the joint strike fighter between Boeing and Lockheed Martin. One of the LM guys said something like a principle of winning many of these competitions is that it has to look like fighter plane. The idea being that theres looked more like a fast scary fighter while the Boeing fighter had that giant scoop and didn't look like a 'traditional' fighter. White Knight 2 doesn't look like something that should be safe... at least to me.

Re:white knight 2 looks too fragile

[Gothmolly]

And you're an aeronautical engineer, and thus qualified to make that determination? Oh wait...

Re:white knight 2 looks too fragile

[AikonMGB]

You must not fly at all then, since with any airplane, the only join between the hull and the sky are the wings.

Aikon-

Re:white knight 2 looks too fragile

[Nyeerrmm]

Actually, on any airplane, the wing has to be able to support the full mass of the aircraft, albeit spread over the entire surface of the wing. If you think about it, it has to have the aerodynamic pressure be at least equal to the mass of the aircraft. And then all that load gets transferred to the spars, so on a normal single-wing aircraft, the central spar is carrying the entire aircraft mass, if its the type of design that carries through the middle of the aircraft.

Also, in order to strengthen it to support the weight of SpaceShipTwo, you can do it without any visible change, just make the spars in the wing heftier.

As far as having to make it look cool, of course they do... its supposed to appeal to people who want to spend $200k going to (suborbital) space. And given that the methods to check the structural soundness of such a set-up are well established, and that Rutan isn't an idiot, I'd imagine it can handle worst case scenario loads with a safety factor of 1.2 or 1.3, as is common for any aerospace application.

Re:white knight 2 looks too fragile

[ionix5891]

dont worry only the rich would get to ride on this, and if anything happens to them, well oh dear :)

Re:white knight 2 looks too fragile

[ceoyoyo]

When you fly in an airplane, everything is essentially suspended from the wing. Would you rather have everything hanging from a single point on that wing, basically making the longest possible (balanced) lever, or have the weight split in two and attached at two points?

Re:white knight 2 looks too fragile

[Harlan879]

Would you rather have everything hanging from a single point on that wing, basically making the longest possible (balanced) lever, or have the weight split in two and attached at two points?

Well, from the point of view of moment of inertia, I'd much rather have the weight at the center, actually. That plane is going to have some seriously weird torque going on when it makes turns.

Re:white knight 2 looks too fragile

[mtargettuk]

which of the two cockpits does the pilot sit in? or is there one in both?

Re:white knight 2 looks too fragile

[Cally]

You could just about persuade me to take a trip in the mothership, but I wouldn't go near the SS2 for all the tea in China - not until they've done, say, one percent of the number of test flights needed to certify a typical normal civil light aircraft, and not had any unfortunate incidents like the one that so nearly killed the pilot on the first SS1 launch. It blows my mind that people are willing to slap down hundreds of thousands of dollars for the chance to be torn to shreds by centrifugal force, incinerated by an engine failure, or even simply spiralling gently down with half the control surfaces missing for a nice leisurely twenty minutes before lithobraking.

On the other hand, conneisseurs of huge explosions are eagerly awaiting the first test flight of Falcon-9, which as the name suggests bundles nine of the Falcon S1 engines that put their test mass into orbit a few months back. Unlike F1 which have been at Kwajelien Atoll in a US army test range, F9 launches from the Cape. There's no keeping spectators and TV crews away from that baby, no sir!

Re:white knight 2 looks too fragile

[Teancum]

It should be pointed out that the "payload" (aka Spaceship two and "other stuff") is going to be carried about from the center of the aircraft.

The alternative would be to build something like a C-130 that would toss the "payload" out of the back of the vehicle. But then again, why do you need to wrap up an aerodynamically efficient "payload" with a hull that will only add more weight and engineering costs?

It is an amazing vehicle, and it will be interesting to see it in flight with the full operational mode including the spacecraft.

BTW, I'm certain there is extra reinforcement on the center span between the two hulls, if only to support the "payload", much less to be able to deal with the additional torque due to the two fuselages.

Re:white knight 2 looks too fragile

[Napoleon The Pig]

And given that the methods to check the structural soundness of such a set-up are well established, and that Rutan isn't an idiot, I'd imagine it can handle worst case scenario loads with a safety factor of 1.2 or 1.3, as is common for any aerospace application.

The SF is actually prescribed for the majority of civilian applications. Since the MTOW of White Knight 2 is greater than 12,500 pounds it falls under FAR Part 25 for certification requirements. The limit load SF prescribed from FAR Part 25.303 is 1.5.

Re:white knight 2 looks too fragile

[ceoyoyo]

Most aircraft carry both their engines and fuel outboard in the wings with no problems. Considering the mass of a fully fueled SpaceShip 2 hanging in the middle, the mass layout of White Knight 2 probably isn't really that much different than a single fuselage aircraft with wing mounted engines.

The dual fuselage and dual tail design is a bit unusual in commercial aviation, particularly today, but it's been used a fair amount through history.

Re:white knight 2 looks too fragile

[LenE]

... and not had any unfortunate incidents like the one that so nearly killed the pilot on the first SS1 launch.

Huh. I never would have guessed that this might have happened on the first SS1 launch, as I just had a nice chat with Mike Melvill last night and he was remarkably in one piece. As far as I know, he wasn't nearly killed by anything in the SS1. He made many flights during that test program, and survived all without a scratch.

Seriously, SS1 was a research program, a one-off prototype. Nothing like it had flown before, and nothing like it since. The devil is in the details, and when you are in a flight envelope which does not overlap much with publicly available information, you occasionally will find the devil. Much was learned from SS1, and luckily, everyone who flew it made it home unharmed, thanks to brilliant people who deciphered the problems and made appropriate corrective actions.

-- Len

Re:white knight 2 looks too fragile

[khallow]

Huh. I never would have guessed that this might have happened on the first SS1 launch, as I just had a nice chat with Mike Melvill last night and he was remarkably in one piece. As far as I know, he wasn't nearly killed by anything in the SS1. He made many flights during that test program, and survived all without a scratch.

Well, people who have near death experiences often look like people who haven't. In Mr. Melvill's case, SpaceShipOne went into an uncontrolled spin during the rocket boost phase. Fortunately, he was able to regain control when it reentered the atmosphere. It sounds dangerous enough that a less skilled (or an easily panicked) pilot might have died.

Re:white knight 2 looks too fragile

[stockard]

The margin of safety for the majority of commercial aircraft is actually 1.5 in the US. When the military releases the RFP for new aircraft, they'll specify the margins they want, but it's typically 1.5. They'll also sometimes add in requirements for no permanent deformation at 115% of load in key components of the structure. Since this would be the first commercial passenger space plane, I imagine Rutan will be pretty conservative on the margins.

Re:white knight 2 looks too fragile

[WindBourne]

I am surprised that you are not modded up. Everybody forgets that this really is rocket science. It takes a while to get it down esp. when trying new ideas. And I am thankful that Scaled AND SpaceX are doing just that. Scaled is quite a bit more RD, but even SpaceX has its share of trial/errors going on.

Re:white knight 2 looks too fragile

[Archon-X]

When you're wealthy, you seek experiences, not items.
Anyone can buy a bugatti - not everyone can experience zero g.

Re:white knight 2 looks too fragile

[Teancum]

Had SS1 gone into the additional mission phase as was originally anticipated, I'm quite certain this issue would have been resolved.... and it certainly is being accounted for in the SS2.

Since SS1 went to the Smithsonian, there was no reason to keep tinkering with the launch regime, and it was sufficient to note that it was an issue. The SS2 test flights will certainly be interesting in this regard, but the larger mass may help it keep a slightly more stable flight profile as well.

It was a good point you made here, however, that the flights weren't without incident and could have ended catastrophically. I certainly wouldn't want to be on the first flight of SS2 without having substantial experience as a professional test pilot, of which Mike Melville certainly is one of those. It also doesn't hurt that the White Knight & SS1 share the same flight controls (as does the WK2 & SS2), so there was some built-in real-world flight experience that Mr. Melville could fall back on instead of purely simulator experience.

Re:white knight 2 looks too fragile

[Napoleon The Pig]

Actually all the military stuff is governed by MIL-HDBK-516. They don't explicitly specify a SF when they release the RFP. The whole process is extremely tailorable to the specific aircraft being designed, meaning there are no hard requirements just vague criteria like "Verify that the airframe is designed such that ultimate loads are obtained by multiplication of limit loads by the appropriate factors of uncertainty. Also verify that the ultimate loads are used in the design of elements of the airframe subject to a deterministic design approach." (MIL-HDBK-516B, 5.1.5)

That criteria is used as the starting point for negotiations between the aircraft designers and the airworthiness certification offices. Not all criteria listed in 516 are applicable to all aircraft so the first task is to go through the document and determine what is applicable and what isn't. If a criteria is found to be applicable you can't modify it in any way, but you can enact a standard to fulfill that criteria. These standards are the primary source of negotiation between the certification offices and the designers. For example, a typical standard for criteria 5.3.3 (Stresses and strains in airframe structural members are properly controlled...) would be something like a SF of 1.33 for cast parts, 1.15 for fitted parts (if not demonstrated by static test), and 2.0 for bearings for elements with relative motion. However if an aircraft manufacturer comes back with a new process for casting a part that reduces foundry quality control problems and can prove through testing that they have a more accurate construction method thus reducing the need for a factor of safety, then they'll most likely get a reduction on that standard.

Anyway, long story short:

None of the military requirements are set in stone. The standards are negotiated with military technical area experts (TAE). From that the designers submit an Engineering/Data Requirement Agreement Plan (EDRAP) and use that document to outline all the analysis testing and evaluation needed to be done. Since the testing and evaluation is a huge cost driver for the developer they want to reduce the number of tests performed on the system. Each test creates an artifact that is submitted with the agreed upon EDRAP as well as other documents (system safety outline, FMEA, etc) which are then sent back to the certifying authority who then determine whether or not all the requirements were met. If they have been, then a flight clearance is released for that design.

And that, in a nutshell, is the military airworthiness certification process.

Re:white knight 2 looks too fragile

[LenE]

Mike has had his share of scary moments in experimental planes, but this famous episode ranks way down the list, and was certainly not a near-death experience. It was not an uncontrolled nor uncommanded spin, and he regained roll stability well before entering the atmosphere by using the RCS system, which was implemented on the vehicle for just such occasions.

This flight was a test flight. It lead to changes in the flight profile that eliminated the aggravated roll condition. All of the following flights were successful at avoiding the excessive roll. Lessons were learned and applied.

Both Mike and Brian Binnie experienced what would best be described as massive sensory overload from the whole launch experience. No amount of simulator flying could have prepared them, and the test program was far too short to give them enough familiarity to overcome the overload. In this condition, it was hard enough for them to remember their own names while the rocket was firing, let alone keep the flight controls doing what they were supposed to do.

My sarcastic comments about Mike being in one piece were aimed at the hyperbole statement about him being "almost killed" on the first flight. While it made a stunning piece of video with the earth spinning around the windows, he was not in any danger at the time. He told me that since he was basically in microgravity at the time, he could close his eyes and not tell that he was spinning at all. He focused on doing his job and using the RCS system to arrest the roll.

A roll and a spin are two different things. In the case of a plane spinning in thick atmosphere, many times this is an unrecoverable condition. At the very least, it takes non-intuitive action to break out of the spin. Also the chance of structural failure caused by aerodynamic forces tends to make spins very deadly, hence the sense of danger for commonly understood spins. When you take the atmosphere away and configure the vehicle to counter exo-atmospheric orientation problems with the feather and an RCS system, the problem is greatly minimized. So while stunning and hair-raising for all of the arm-chair pilots to watch, the situation on that SS1 flight was not serious beyond the fact that such flights and conditions had not been experienced before.

-- Len

Re:white knight 2 looks too fragile

[cs668]

I don't think he/she ever claimed to be an aeronautical engineer.

He simply pointed out that a big part of getting people into a vehicle was marketing and their perception of the safety, and in a for profit venture I would hope that they are taking marketability into account as well( even though technically it's meaningless )

Re:white knight 2 looks too fragile

[Cally]

Everybody forgets that this really is rocket science.

That's exactly the point. It's rocket science, not sightseeing trips in a hot air balloon. Seems to me SS2 is selling sightseeing tickets on vehicle of a /type/ that has only made two previous flights. Would you have got on the third flight of any type of rotary wing aircraft? Good luck to them, I know Scaled are very good at what they do, and I hope it all goes well for them. That's all.

Re:white knight 2 looks too fragile

[WindBourne]

Well, Actually, I MIGHT consider going on something designed by Scaled. They have some of the best engineers in the business and have a LONG reputation for safety. The current stuff is NOT all that different from their previous work (SS2 is a derivative of SS1 and WK2 is not that difficult; LOTS of other work out there). All in all, I would consider being one of the originals.

Re:white knight 2 looks too fragile

[TheLink]

If "zero g" is all that you're looking for, all you need to do is fall :).

Re:white knight 2 looks too fragile

[Archon-X]

I'd have thought falling would have been the opposite of zero g :D

Re:white knight 2 looks too fragile

[TheLink]

The ISS is falling all the time. It just keeps missing the ground (and most of the atmosphere).

Re:white knight 2 looks too fragile

[dragonbutt]

I'd have thought falling would have been the opposite of zero g :D

Thats just the abrupt stop at the bottom

Re:white knight 2 looks too fragile

[theshowmecanuck]

Yeah... I do understand that the engineers did the math. The reason it looks dicey to me is that it is connected out where the wingtip would be and it doesn't look like they kept the same profile on the wing all the way across. It looks like it gets narrower. And then I thought about how a lever works on a pivot... But I'm sure it has to be sound or they would not have spent the money building it. :) Now all I need to do is make my second million to enjoy a ride on it. And write off the first million while I'm at it since I don't think it is ever going to come in anyway.

""Runway Trial"

[HotNeedleOfInquiry]

Just to pick nits, the proper term is "high speed taxi test".

I know, but it's Saturday morning and I'm bored...

Re:""Runway Trial"

[Napoleon The Pig]

The article states it was actually a low speed taxi test, but I agree with your overall point. I don't think I've ever heard of them as "runway trails" only "taxi tests".

Launch from altitude vs near equator

[ILikeRed]

I think I have heard that the US space program(s) launch near the equator (or as near as they can in the US) to get free energy from the spin of the Earth. I think it is great that Rutan's program uses an aircraft to additionally lift the rocket for the first 50,000 ft or so.

I've looked, but not found the equations - what is the relative advantage of near equator (if any) vs height? Florida is close for the US, but how high would you have to be to make launching off a mountain in Colorado worthwhile? I realize the tallest mountain is only at ~29k feet (8.85km), but even that would have to be a boost out of the gravity well, wouldn't it?

What I really wonder, is why we don't have powered rails launching rockets off the top of mountains - seems like it would be worth the budget - but again, if anyone knows where to find the equations it would be much appreciated.

Re:Launch from altitude vs near equator

[craigavonite]

Would the biggest problem with launching off a mountain not be the environmental impact? I don't see the damage that would be caused to the mountain sitting well with the green vote.

Or the visual impact of such a thing, one of the main reasons people dislike wind farms, pretty mountain pity about the hulking great rocket strapped to it.

Re:Launch from altitude vs near equator

[ZankerH]

The net energy gain and benefit depends on what kind of orbit you're launching into - for example, a launch into an equatorial orbit (as is required for geosynchronous satellites) can only be performed from the equator - barring expensive plane change burns in orbit, while it actually makes more sense to launch into polar orbit from locations away from the equator, since the Earth's spin is irrelevant as the intended orbit is perpendicular to the spin direction. Launching from a higher altitude is largely irrelevant energy-wise, since the majority of the energy wasted on orbital ascent is spent acquiring horizontal orbital velocity (~8km/s), not gaining altitude. While the atmosphere is thinner at 9 kilometres altitude, the logistics required to haul a launch centre atop mt. Everest hardly pay off the energy saved. Launch

Re:Launch from altitude vs near equator

[ZankerH]

In the case of the USA, the location of the Kennedy Space Centre (Florida's east coast) was also chosen because it puts most of the spacecraft's ascent trajectory across the Atlantic ocean, a safe distance from any inhabited areas. Unfortunately, the Chinese don't mind vaporising a village or two in case of a launch mishap.

Re:Launch from altitude vs near equator

[iteyoidar]

It's been a while since I have used these equations, but a basic equation for the mechanical energy of an orbit is:

E = v^2/2 - mu/r

where mu is the gravitational parameter of the earth (3.986 * 10^5 km^3/s^2).

So looking at the energy of something sitting on earth...

The radius of the earth is around 6378 kilometers, and the tallest mountain in Colorado I believe is around 14,000 feet or 4.3 kilometers above see level. So you'd get an extremely small increase in energy by launching higher and reducing the r term by less than one percent, while you'd be reducing your initial velocity by quite a bit since you have to launch at an angle to the earth's rotation or spend more energy changing the plane of the orbit.

This doesn't take into account that you will have less drag at the top of the mountain, but that won't save enough energy to make it worthwhile.

Re:Launch from altitude vs near equator

[Nyeerrmm]

You get some free energy from the spin, yes, but the main reason you try and launch from lower latitudes is that you want to have the option to get a near equatorial orbit inclination. Basically, you can't launch to an inclination lower than your latitude; if you think about it, launching due east (or west, but that would be going against the spin) would put you in an orbit thats the same inclination. If you aim a little north or south you end being inclined a little bit more... whether its north or south changes the position of the ascending node, but not the overall inclination. If you aim due north or south you get into a polar orbit. As far as the additional altitude... its such a miniscule amount that its not worth worrying about.

The reason you may want to have a low as inclination as possible is because if you're going to GEO or lunar or planetary missions, you want to be near zero inclination. In order to get there, you have to do an expensive plane change maneuver, which has a delta-v=sin(i)*V, so getting that inclination lower means big fuel savings.

As far as calculating the fuel savings, just consider the difference between the rotational speed of the point on the surface (sin(lat2)-sin(lat1))*r_earth*(2*pi/24 hrs) to get the additional velocity you get (and thus less delta-v you need to apply on orbit). Running that between the Russian Star City (45 degrees) and the cape (21 degrees) shows that we get ~150 m/s difference, which is nice but not game changing.

As far as sky launch or mountain launch, I learned a great little rule of thumb here a few weeks ago, the 666 rule. Launching from Mach 6 at 60000 feet (probably much higher than any reasonable air launch system), gives you only a 6% energy savings for orbital systems. So, it really doesn't give you a whole lot for the added complexity, which is why as far as i know theres only one air-launched system, an Orbital Sciences rocket that launches off an L1011. The reason why it works for Virgin/Scaled Composites is that it gives you probably 30% of the energy needed to reach the altitude, but not the orbital velocity.

As far as equations... the atmospheric drag models make launch hard to judge, but what is cleverly called the "Rocket Equation" is a really easy way to look at fuel usage with impulsive delta-vs... usually a more valuable quantity than energy since it directly applies to the amount of fuel needed and used.

Re:Launch from altitude vs near equator

[Anonymous Coward]

IANARS (I Am Not A Rocket Scientist), but...
Launching from an airplane or from a mountaintop has almost nothing to do with getting out of our gravity well and a whole lot to do with getting out of our atmosphere.

Escape velocity from the earth's surface is 11.2km/s (i.e. if earth didn't have an atmosphere to slow things down via friction, you could shoot an object up at that speed and it would never fall back down). Escape velocity in low earth orbit is 10.9km/s, only a couple of percent less due to being farther out of the earth's gravity well, but tremendously easier to achieve because there's no air in the way to slow you down.

Launching from a moving plane, or via a powered launching system, can contribute to your velocity directly, but again the problem is the atmosphere. The fastest atmospheric vehicles we can make (military planes and such) only get up to around mach 3 (and they do that tens of kilometers up, in thinner air), which is about 1 km/s, whereas escape velocity is 11.2km/s and even to reach low orbit requires about 8km/s. Imparting a really significant fraction of a spaceship's final velocity before it leaves the atmosphere would require reengineering the ship to survive atmospheric friction at those velocities, which might cost you a lot of mass.

Re:Launch from altitude vs near equator

[Deadstick]

As far as satellite launching is concerned, the height of the launch site is utterly trivial. In order to achieve a low earth orbit, you have to accelerate an object to about 23,000 feet per second; for a one-pound object, that will take over 8 million foot-pounds of energy. Lifting that same object from sea level to the top of Mt. Everest will take 29,029 foot-pounds.

The latitude of the launch site offers some tradeoffs. A site on the equator will give you a few hundred extra feet per second than one at 45 degrees latitude, not a real big advantage. However, a launch directly into orbit will always put you in an orbit whose inclination is at least the latitude of the launch site. Launch from Cape Canaveral, and you'll be in an orbit inclined at least 28 degrees from the equator. You can make it higher, but not lower. If you want to get an equatorial orbit -- which most communications birds need -- you have to launch into the inclined orbit first, fly to the equatorial plane, and then make a "plane change" maneuver which takes a substantial fraction of the energy it took to put you in orbit. From the equator, you can launch directly into any inclination, which is why the European Space Agency birds come out of French Guiana.

rj

Re:Launch from altitude vs near equator

[khallow]

It's not utterly trivial, but it's well below the major stuff (net delta v, air resistance and gravity losses, Earth's rotation, etc). I did the calculation a long time ago and got a savings of something like 20 m/s for launching at 50k feet instead of sea level. In comparison, the total delta v from sea level tends to be about 9-10 km/s. So it doesn't help much, but it does mean you can squeeze in a little more payload or you get a little more leeway for putting the payload in orbit.

Re:Launch from altitude vs near equator

[khallow]

As far as sky launch or mountain launch, I learned a great little rule of thumb here a few weeks ago, the 666 rule. Launching from Mach 6 at 60000 feet (probably much higher than any reasonable air launch system), gives you only a 6% energy savings for orbital systems.

Energy is cheap. Mach 6 is a quarter of the delta v you need. That significantly reduces the amount of propellant that you need to get the rest of the way. For example, you could find some way to boost your speed by Mach 6 three more times to get to orbit (or more accurately two and a half, roughly).

Two scientists aboard the ISS

[RevWaldo]

- "Rochambeau for it?"
- "Two out of three?"
- "Deal."
- "OK. Rock-paper-scissors-Shoot! Rock. Rock-paper-scissors-Shoot! Paper. Rock-paper-scissors-Shoot! Rock."
- "I win!"
- "Yeah, you win... go ahead and say it.."
- "Helmsman! Engines to FULL IMPULSE POWER!"
- "Doofus." (pushes button)

Re:Two scientists aboard the ISS

[Robin47]

I can't hold her, Captain, she's breaking up!!

Re:Two scientists aboard the ISS

[tcolberg]

Helmsman: "But sir, she'll fly apart!"

Cpt. Sulu: "Fly her apart then!"

NUCLEAR ISOMERS

[sanman2]

Since energetics is the key trumping factor for overcoming the earth's gravity well, we need more energetic power sources than mere chemical fuels. I've read that there have been some recent new successes announced in the past few months in nuclear isomer research. As we know, nuclear isomers are atomic nuclei whose protons and neutrons have absorbed extra energy to keep them at a higher energy state, analogous to the idea of electrons absorbing energy and being promoted to a higher energy state. But the far heavier mass of the protons and neutrons means they absorb way the hell more energy. This is the kind of energy we need to power space travel.

Re:NUCLEAR ISOMERS

[Adambomb]

Overcoming earths gravity is not the issue. The issue is maintaining a long enough specific impulse for the craft to continue to accelerate long enough to make interplanetary distances livable. The kind of propulsion needed to break earths gravity is the opposite, it needs to emit much of its thrust in a short period to beat out good old g's negative acceleration.

We need both to power space travel. We're getting pretty good at the latter already. VASIMR is NOT for earth->orbit launches, but for orbit->elsewhere transit.

Re:NUCLEAR ISOMERS

[GreenTom]

IMHO (and I am not a rocket scientist), this misses on two fronts: the difficult thing with rocket propulsion is reaction mass, not energy, and nuclear energy states are more energetic than electron states because of the higher binding energies of the strong (or is it weak?) force compared with electromagnetic forces, not because of the greater masses of protons and neutrons.

Re:NUCLEAR ISOMERS

[Teancum]

E = m * v^2

The trick here is to improve the "velocity" of the reaction mass as close to the speed of light as possible if you want to get rid of it efficiently.

Yes, energy is the key here and not necessarily mass. Normal chemical rockets really don't send the reaction mass out the nozzle at that high of a velocity, and instead make up for that by simply shoving out huge amounts of propellant. That is fine as long as all you are trying to do is go up a couple hundred miles in altitude, but it won't get you anywhere other than low-earth orbit in a respectable fashion.

With the price of getting anything into orbit costing currently close to $10k per pound (give or take an order of magnitude here, but at roughly this price), reaction mass for interplanetary missions (or even geosynchronous orbit station keeping) is incredibly expensive and you tend to run out of it in a real hurry.

By increasing the energy density of the reaction mass, you can sustain a burn for a much longer period of time. Alternative propulsion techniques (VASMIR & ion propulsion) try to take advantage of perhaps a trade-off of lower thrust rates in exchange for huge specific-impulse (how efficient the rocket engine is with its fuel).

Keep in mind that specific impulse is usuallly measured in pound(force)-seconds per pound(weight), which is why (falsely) they are usually quoted in units of seconds. The metric unit would be N-s/kg.

BTW, if you start to throw energy into the energy states of electrons and atomic nuclei, don't forget Einstein's famous E=m*c^2 formula, as that also applies in a huge way into reaction mass as well. Yes, this is high energy physics we are talking about here... like what is found in nuclear accelerators like CERN, but on a production device.

Re:NUCLEAR ISOMERS

[techno-vampire]

E = m * v^2

Sigh! So close, and yet so far away. E = .5*m * v^2 is what you meant.

Re:NUCLEAR ISOMERS

[GreenTom]

Right, right, I completely agree if we're talking about interplanetary travel. In that case, you want to get your specific impulse as high as possible, so maximizing the energy per unit of reaction mass is the most important thing. But the comment I was responding to was talking about getting to orbit, and for that, raw thrust is important. E = .5mv^2, but momentum = mv, so thrust scales as the square root of energy. Trying to lift off the ground with a low-reaction mass engine likely requires unreasonable amounts of energy. Of course, anything that gives you more energy does help.

Re:NUCLEAR ISOMERS

[aqk]

Oh phhooey! Once again:

Just give 'em gigantic pounding thrust [today.com], none o' this wussing about with plasma. OXYGEN AND KEROSENE!

Ask GM. Ask Chryler! They KNOW!

Re:NUCLEAR ISOMERS

[khallow]

Do you have some links to this work? Yes, I can and probably will google for them, but hey, I'm the lazy reader and I know there's more of me than there are of you. :-) I wonder what the decay time is for these isomers. Wouldn't be much point to them, if they have a half life of 5 microseconds.

Quantum Lens

[Paracelcus]

Focus gravity by distorting a microscopic region of space with intense EM pulses.

Re:Quantum Lens

[Anonymous Coward]

The aliens seem to be having good success with this technology.

Not that simple.

[DerekLyons]

If you want to do any deep-space maneuvers, you have to carry all that liquid propellant (be it LO2/LH2 or LO2/RP-1, for the rocketry equivalent of a gas guzzler (specific impulse of 200-500 s), instead of carrying a small amount of high-efficiency propellant with a specific impulse of up to 10000 s.

The actual tradeoff goes something more like this:

a) Large lightweight tanks, large amount of fuel, nearly no [electrical] power supply, medium to light weight engine. Total weight declines significantly across the life of the system. (Weight is dominated by propellant.)

b) Small lightweight tanks, small amount of fuel, a very large and very heavy power supply, lightweight engine. Total weight does not change significantly across the life of the system. (Weight is dominated by the power supply.)

Ion engine proponents like to pretend the power supply problem doesn't exist.

In Unrelated News...

[Geoffrey.landis]

Reader clarkes1 points out related news...

And this reader points out that these two news bits are not, in fact, related.

Virgin Galactic is great, and I'm all in favor of their business (and if I had the money I'd even buy a ticket)... but their vehicle is not designed to get to orbit, and has little or nothing to do with orbital flight.

Yes, but...

[mr_matticus]

I think the point he was making is that all things being equal, you get a lot more travel per launch dollar with the ion/plasma engine.

Break it down into two stages: (I) get to orbit and (II) mill around in space. The launch vehicle will be able to lift the same amount of excess weight for stage II in either case (rocket or ion spacecraft), say 100,000 pounds.

Now, most of that 100,000 pounds can be wasted on propellant, as you point out in your first tradeoff analysis, meaning a smaller and crappier vehicle all around. Or, that "power supply problem" (in which "large and heavy" is still a fraction of the weight of the propellant from case A) allows for an all around larger, better-equipped vehicle.

The tradeoff is still (mostly) a no-brainer. It's not that the problem doesn't exist, it's that it doesn't have equal weight (pardon the pun) to the propellant problem of rockets.

Re:Yes, but...

[Titoxd]

Indeed, the power supply problem does exist, and is actually the limiting factor in the performance of ion thruster engines and electric propulsion in general. That limitation actually causes very high specific impulses to be undesirable as the power supply weight savings exceeds the mass savings in propellant. The ideal specific impulse then becomes an optimization problem.

That said, my point is that there are particular applications for which electric propulsion is better than conventional methods (long-distance robotic missions, to pick one), and there are other applications in which chemical propulsion is better than electric propulsion (such as moving a satellite from low-Earth orbit to geostationary orbit... we don't want to wait months for that to occur!) Kind of like in anything involving engineering, you have trade-offs that you have to consider for a particular mission. But assuming that big liquid propulsion rockets are the solution to all the problems is rather lame.

Doesn't matter

[S-100]

For suborbital flights, the longitude of the launch point is irrelevant. These tourist flights are just going for altitude, not escape velocity. BIG difference.

doing the obvious on the ISS

[heroine]

After 8 years of crews testing obscure basic science, they finally have the first tentative approval for the most obvious experiments some time in the future. Incredible.

Re:doing the obvious on the ISS

[TheLink]

IMO they did do at least one useful and interesting experiment.

It's called space tourism.

Of course, it wasn't NASA's idea (and I hear they didn't like it).

But may be the most useful experiment the ISS has ever done or will ever do.

Is it enough to keep ISS in orbit?

[Loke the Dog]

Obviously, this is just an experiment, but to get some perspective, how much drag does ISS experience?

From wikipedia:
"Assuming expected ion boosting efficiently of 80%, at low end of the throttle VX-200 will be capable of producing 9.24 N of thrust (at an Isp of 3,000 seconds) and in high efficiency mode it can be expected to produce less than 1 N of thrust (at 30,000 s)."

Would that be in the same magnitude as the drag? If so, could this be used for altitude control?

Anyone else get a robotech flashback

[ImNotAtWork]

when I saw the VF (Veritech Fighter) model number

Batteries?

[afidel]

Ok, so they are going to use 200KW for 10 minutes or about 34kWhrs. These guys make a system that is probably currently the best bet for power density vs orbital safety, the EEV version has 1306 Wh and weighs 15.6kg. At 80% discharge that's about 1KWhr. That means that you need ~530Kg of batteries, at $10K/lb that comes out to $12M to launch the batteries for this thing. I was going to suggest ultracapacitors but it turns out they suck for energy density, on the order of less than 6Wh/Kg! Reading on wikipedia (yeah, I know) Lithium Ion batteries with nanowires achieve almost 15kWHrs/Kg (.75 * 4,2000 mAh/g @ a nominal 3.6V per cell) so developing them would save almost the entire launch cost AND get us better batteries for all sorts of terrestrial applications!

Related News?

[Skylax]

In which way is the news about Runway testing WhiteKnightTwo (powered by conventional air-breathing engines) related to testing a VASIMR Engine on the ISS (a Plasma propulsion system with a magnetic nozzle)?