VASIMR Plasma Thruster To Be Tested Aboard ISS 81
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.
Nice acronym (Score:3, Funny)
Bugger that namby pamby stuff (Score:5, Funny)
Just give 'em gigantic pounding thrust [today.com], none o' this wussing about with plasma. OXYGEN AND KEROSENE. It was good enough for Wernher von Braun!
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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
NUCLEAR ISOMERS (Score:4, Interesting)
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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-
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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!
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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.
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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
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Sigh! So close, and yet so far away. E = .5*m * v^2 is what you meant.
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Not that simple. (Score:2)
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
Yes, but... (Score:2)
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 vehicl
Re:Yes, but... (Score:5, Insightful)
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.
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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!
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> Just give 'em gigantic pounding thrust
It's what keeps the ladies coming back!
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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.
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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!
white knight 2 looks too fragile (Score:2, Insightful)
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And you're an aeronautical engineer, and thus qualified to make that determination? Oh wait...
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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 )
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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 (Score:5, Informative)
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.
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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, incine
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... 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 en
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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.
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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 m
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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
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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.
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When you're wealthy, you seek experiences, not items.
Anyone can buy a bugatti - not everyone can experience zero g.
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I'd have thought falling would have been the opposite of zero g :D
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I'd have thought falling would have been the opposite of zero g :D
Thats just the abrupt stop at the bottom
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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.
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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 sub
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dont worry only the rich would get to ride on this, and if anything happens to them, well oh dear :)
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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?
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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.
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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 [wikipedia.org] 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 mod [wikipedia.org]
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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.
""Runway Trial" (Score:3, Informative)
I know, but it's Saturday morning and I'm bored...
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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 (Score:4, Interesting)
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.
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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.
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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 red
Re:Launch from altitude vs near equator (Score:5, Interesting)
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.
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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).
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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 f
Re:Launch from altitude vs near equator (Score:5, Informative)
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
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Doesn't matter (Score:1)
Two scientists aboard the ISS (Score:4, Funny)
- "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)
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Helmsman: "But sir, she'll fly apart!"
Cpt. Sulu: "Fly her apart then!"
Quantum Lens (Score:2, Interesting)
Focus gravity by distorting a microscopic region of space with intense EM pulses.
In Unrelated News... (Score:2)
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.
doing the obvious on the ISS (Score:4, Insightful)
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.
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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? (Score:2)
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 (Score:1)
Batteries? (Score:2)
Related News? (Score:1)