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Plasma Rocket Successful Full Power Test
Posted by
ScuttleMonkey
on Mon Oct 27, 2008 02:05 PM
from the to-infinity-and-beyond dept.
from the to-infinity-and-beyond dept.
Matt_dk writes "VASIMR is a new high-power plasma-based space propulsion technology, initially studied by NASA and now being developed privately by Ad Astra. A VASIMR engine could maneuver payloads in space far more efficiently and with much less propellant than today's chemical rockets. Ultimately, VASIMR engines could also greatly shorten robotic and human transit times for missions to Mars and beyond."
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Science: NASA Plans Test of New Plasma Drive 266 comments
Sallust writes "Flightglobal has an interesting article about the testing of a new electrically powered plasma engine called the Vasimir. It's being developed by former astronaut Franklin Chang-Diaz and promises to greatly reduce the time and fuel required for interplanetary journeys. According to the article: 'The Vasimir involves the injection of a gas such as hydrogen into an engine that turns it into a plasma. That plasma is then energised further using radio signals as it flows through the engine, a process controlled by electromagnetic waves from superconducting magnets. Accelerated and heated through this process the plasma is focused and directed as exhaust by a magnetic nozzle. Vasimir is many times more efficient than conventional chemical rockets and far less fuel is needed.' The developers are finalising an agreement with NASA to fit a scaled-down version of the engine to the ISS to conduct operational tests. There is also a concept video on YouTube suggesting a journey time for a manned craft to Mars on the order of 60-70 days."
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Plasma Rockets Suck. (Score:5, Funny)
Re:Plasma Rockets Suck. (Score:5, Funny)
Plasmas have deeper blacks, to really show that cosmos better.
Parent
Re:Plasma Rockets Suck. (Score:5, Funny)
Parent
Re: (Score:3, Funny)
Re:Plasma Rockets Suck. (Score:5, Funny)
Mine's coloured in alternating stripes of Happy and D#. How about yours?
Parent
Re: (Score:3, Informative)
Mine tastes like blue and sounds like the smell of rose petals...
Although, in honesty, unless I take very large doses (greater than 400 micrograms), I find the only synaesthesia I get is seeing sounds. I love "watching" Halcyon and On and On towards the end of a good trip... There's some really nice wavy bits there and the colours in the vocal sounds are quite incredible.
With increased dosage, I've experienced almost every other kind of synaesthesia, but I'm not sure I've seen "happy" (although I may have
Re: (Score:3, Funny)
I'm still waiting for OLED rockets.
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The interesting part (to me anyway) (Score:5, Informative)
Re:The interesting part (to me anyway) (Score:5, Informative)
The Argon is not an energy source, it is merely propellant. Argon is chosen due to ionization potential. There is no splitting of argon (that consumes energy rather than producing it)
Power would have to be carted up separately, and in the case of a plasma drive it would presumably be nuclear.
Parent
Re:The interesting part (to me anyway) (Score:5, Insightful)
I thought it seemed fairly straightforward.
1. the hotter the flame, the more thrust you have and the more efficient the thrust. Your limit is when it's hot enough to melt the rocket's nozzle.
2. Since it's a plasma, you can control it with a magnetic field, to the point that its heat won't affect the rocket's nozzle.
More efficient=less fuel needed. In addition to keeping the heat away from the metal, being able to control it with a magnetic field means you don't have to have a moveable nozzle to steer the thing, making it possibly simpler than traditional designs.
Parent
Re:The interesting part (to me anyway) (Score:5, Informative)
There are only two things that matter in determining how much delta V you can get from a given rocket, Exhaust velocity and Propellant mass fraction.
The exhaust velocity is the mean velocity of the exhaust.
The propellant mass fraction is the fraction of vehicle launch mass that is propellant that will be slung out the back.
Now, in a conventional rocket, the propellants are typically accelerated by a simple thermodynamic gas generator (turbopumps and a chamber to burn the propellants to create high pressure hot gas) followed by a nozzle to convert the pressure and temperature into velocity. There are inherent limits in this process, not least that the heat source and reaction mass flow are inexorably coupled.
VASIMIR is essentially an ion drive variant which separates the reaction mass from the power source, and which allows the specific impulse to be varied (the number of NewtonSeconds of thrust per kg of fuel), this is useful as it allows for high thrust burns at relatively low specific impulse and low thrust burns at much better fuel economy to be mixed at will with the same motor.
The electrical power generator is an interesting problem, as most thermal generators on that scale would seem to need a vast amount of radiator to dump the waste heat from the condensers or equivalent. I suppose you could dump some of it into the fuel before it hits the injector, but that is going to be limited. Most likely the plan is to charge batteries with solar power, then discharge them rapidly to give a series of short burns.
I could see some sort of high temperature nuclear plant being flown, but as radiated power rises as the 4th power of absolute temperature, the radiators would have to run really hot to get good overall specific impulse from the complete propulsion assembly (Which means a relatively poor thermodynamic efficiency for the overall electrical plant), this might be a reasonable tradeoff.
Of course the political problems with launching a small reactor would be 'interesting'.
HTH.
Regards, Dan.
Parent
Re: (Score:3, Informative)
it's not really the heat, but the velocity. you can have cold-as-ice propellant if you can throw it away from you fast enough.
of course, with chemical rockets, there is usually a relationship between heat and velocity, but that's not necessarily true for plasma engines.
Physics doesn't work like you seem to think (Score:5, Informative)
I'm not the person to whom you were responding but I suspect the misunderstanding is on your end, not his. The meaning of the phrase is quite clear; in a system with sustained thrust the fuel (and reaction mass) used in a later portion of the trip has to be accelerated (along with the rest of the ship) for the whole proceeding portion of the trip. This means that, early in a long trip, the majority of the fuel/reaction mass you use accelerating the remainder, and only a small fraction is accelerating the payload. That's why large rocket use stages.
The "reasons" may be obvious to you, but they aren't valid. The actual relationship between final speed (from a standing start in some reference frame) and the exhaust velocity has as a factor the natural log of the starting mass over the payload mass. So (to use your made up numbers) if you started with a ship that was 90% hydrazine (by mass) your final velocity would be 1000*ln(100/10) mph or about 2300 mph, over twice your exhaust velocity. If the ship was 99% fuel, the final velocity would be 4600 mph, and so on.
--MarkusQ
Parent
Re: (Score:3, Informative)
Ion, plasma, arc-jet, and the like are all about taking a small reaction mass (aka propellant) and ejecting it out the back at the highest speed possible. F=ma dictates that you can achieve a large force by tossing a large mass at a relatively low acceleration, or by tossing a sm
Re: (Score:3, Insightful)
Keep in mind that unless you are doing something like a Bussard ram scoop that is collecting material enroute, the only thing you have to be able toss out the back of your vehicle is reaction mass you have brought with you.
So your top "speed" is limited to exhaust velocity. All of these more exotic propellant systems are about increasing the efficiency of throwing the mass to increase the velocity of the vehicle.
The problem with these propulsion systems is that none of them are strong enough to be able to
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Re:top speed is HUH?! (Score:5, Informative)
top speed = v * ln(M/m) + v0
where:
v = exhaust gas speed
M = starting mass of rocket + fuel
m = ending/empty mass of rocket
v0 = initial velocity
so the exhaust gas might be only 1000mph but you can go pretty much up to the speed of light if you can get ending mass to 0...
Parent
Constant Boost? (Score:5, Interesting)
Re:Constant Boost? (Score:5, Insightful)
In theory, we could always do that, in practise I don't think we'll ever do that. Getting anywhere really fast burns a ton of extra energy, plasma drive or not. Most of the really long-distance missions haven't accelerated to that speed, they've done a slingshot trip around jupiter or something like that. Even on a Mars mission we're really just waiting for Mars to be in the right position to leap orbit and minimize the rocket use, not plotting a course or going from full impulse to full stop in seconds like you see on Star Trek. It would still cut a lot of costs but the cheapest route is still the slow one.
Parent
Re: (Score:3, Funny)
You can't go full impulse to full stop in seconds without inertial damping anyway. Duh.
{/STAR TREK FANBOY}
Re:Constant Boost? (Score:5, Informative)
Typically these rockets are more efficient than their chemical cousins. For a given reactant mass, rockets will give you more thrust (can't get into orbit with anything but rockets at this point) but the plasma and ion engines are more efficient, low-thrust but higher change in velocity (delta-v.)
As it was described, a mars mission using an ion engine would not leave the space station with a dramatic blast of flame. The captain would say "turn the engine on," go, get coffee, watch a movie, look out the window and still be able to wave back to people at the station. Tune back in three weeks later and he'll be moving at a clip that would make chemical rockets weep in jealousy.
Parent
Re: (Score:2)
Sounds like the smart move would be to combine the systems to get the best of both worlds (some sort of chemical/plasma/ion transmission system)
Re: (Score:3, Informative)
If it launched from a station in orbit, it will need to accelerate from 5mps to 7mps to break orbit. Does this slow acceleration imply that VASIMR power ships will have to circle the earth a few times to build up speed?
The Numbers (Score:5, Informative)
The Wikipedia entry says it can be tuned for an Isp of 3,000k seconds to 30,000k seconds.
A liquid fueled chemical rocket has an Isp of about 500 seconds. A really good fission thermal rocket, maybe 1000 seconds. The Deep Space 1 ion rocket could do 3.1k seconds.
How to turn this into usable numbers:
Find the exhaust velocity. Vex. Multiply the Isp by "g". So, your chemical rocket has an exhaust velocity of about 5 kps, and your VASIMIR 30 kps.
The figure out the velocity change you want. Vd.
Then:
M(o)/(M(o)+M(f)) = e^(Vd/Vex)
M(o) = Mass of spaceship without reaction mass
M(f) = Mass of reaction mass
e = natural log number, about 2.178
A Hohmann orbit trip to Mars orbit from Earth orbit without need for aerobreaking of the like might require 20 kps. Hohmann orbit to Mercury, 40 kps.
Drawback to ion drives and VASIMIR is a really, really low thrust. You might be better off with lower efficiency but higher thrust or you'll lose the fuel (uh, reaction mass) savings in consumables, and/or risks to your crew from flares.
Parent
Re:The Numbers (Score:4, Informative)
Your VASIMR ISP figures are out by 1000. It's 3000 to 30000 seconds, or 3 to 30 k seconds, NOT 3000 to 30000 k seconds.
Generally, if you're going a decent distance, you SAVE time with a high ISP engine, even if it is low thrust. "Decent distance" depends on the specifics, but for most of these engines Mars is far enough away, the moon, probably not.
Parent
Fusion adaptation? (Score:2)
The VASIMR engine works with plasma, a very hot gas at temperatures close to the interior of the Sun. Plasmas are electrically charged fluids that can be heated to extreme temperatures by radio waves and controlled and guided by strong magnetic fields. The magnetic field also insulates any nearby structure; so temperatures well beyond the melting point of materials can be achieved and the resulting plasma can be harnessed to produce propulsion.
Anyone know if this could be used in fusion reactor containment?
Re: (Score:3, Interesting)
However, in the long term, this could be key to getting workable fusion reactors. If the technology for a plasma engine becomes widespread with several independent firms working on it, it's entirely possible that a big breakthrough for fusion reactors will come from
Re: (Score:2)
Yup, [wikipedia.org] as planned for ITER [wikipedia.org].
Thanks, Andrei [wikipedia.org]
Now we just need a good hull... (Score:3, Funny)
Preferbly General Products #2 with a statis field.
Re: (Score:3, Funny)
a statis field.
While I applaud finding a use for the whole lot of them, I'm not sure just what kind of protection you'd get from strapping a bunch of Big Government democrats and republicans to your hull... oh wait, you meant stasis not statist ;)
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I need to know... (Score:2, Funny)
...whether this technology is more like Windows or Linux before I can form an opinion.
Unless there's an RIAA angle, of course.
But where does the energy come from? (Score:2, Informative)
This is all fine with regards to the rocket equation, but that's just about conservation of momentum. You still have to provide it with energy, and 2*H2+O2 -> 2*H2O happens to be as good as you can get in terms of energy/mass ratio. As I see it, this plasma rocket is not really useful without a nuclear power source of some kind.
Re:But where does the energy come from? (Score:4, Informative)
Parent
Re:But where does the energy come from? (Score:4, Informative)
I think they've already solved that one.
SNAP [wikipedia.org]
RTG [wikipedia.org]
Nuclear Reactors for Space [world-nuclear.org]
Parent
Re: (Score:3, Interesting)
Only nuclear reactors. RTGs deliver too little power. A Polywell would be nice if it woks.
Specific Impulse? (Score:2)
The article didn't mention is, so I'll ask the crowd: does anyone know what the specific impulse [wikipedia.org] of this device would be when completed?
Wiki says 3k to 30k seconds (Score:4, Insightful)
The same incorporates "variable specific impulse" so you have to use a range.
3,000 seconds is comparable to a ion motor.
30,000 seconds is better than the predicted Isp of the Orion nuke-bomb drive.
Parent
Finally repulsor propulsion! (Score:2)
Wamprats (Score:4, Funny)
Are there useful numbers on this? (Score:4, Insightful)
OK, this is a classic plasma rocket - ionize an inert gas (here argon) and push it out with an electric field (not done in this test). So what are the numbers? How much argon are they using per unit thrust? How much electric power does this take. Is 200KW the input, or the output?
You still have to carry reaction mass; that's the argon. So you can't just keep boosting as long as you have power.
It's not a bad idea, but it's not clear how good the implementation is.
Re:Are there useful numbers on this? (Score:5, Informative)
it's a paper that the researchers published last year describing what they had done with the previous version of the engine and what they planned on doing with this version
Parent
Arrrrrgon? (Score:4, Funny)
Q: What's a pirate's favorite rocket propellant?
A: Arrrrgon!
Q: What's a pirate's favorite sock pattern?
A: Arrrrgyle!
Q: What's a pirate's favorite rating system?
A: Arrrrbitron!
Q: What's a pirate's favorite Dudley Moore movie?
A: Surprisingly, it's 'Micki and Maude'
Lowest possible Orbit? (Score:3, Interesting)
So, does anyone know what the lowest possible orbit is one can use that thing from?
One reason ion engines cannot be used from ground to orbit is that they need a vacuum to operate, the other one is that the trust is too low to get into orbit.
With Vasimir however one can get higher trust than with typical ion engines. Could it be possible that suborbital trajectories might be enough?
To get a usable orbit one needs an engine which raises the perigee from the ground to a point outside the atmosphere (I even tried this in Orbiter once), could it do that too?
Re: (Score:3, Informative)
While I don't have an answer to my question, let me mention that I somehow had the dream of ion engines being the best thing since sliced bread since they have such a high exhaust velocity (v_e).
Since v_e affects the delta v linearly as opposed to logarithmically like the mass fraction this is just such a nice knob to play with.
Unfortunately the power plant weight of the ion engine is something we are stuck with forever, so there is no nice mass ratio involved with ion engines.
The other thing is that accord
What about the sharks? (Score:3, Funny)
This isn't going to become a useful technology, like lasers, until you can mount it on a shark!
Re: (Score:3, Interesting)
Mind you, much like ion drives, it can only be used in a vacuum, making it totally useless for load-lifting object *into* space and really only useful for moving them around while up there. Ion drives have classically been used as station keeping drives on space stations and
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Re: (Score:3, Informative)
Funny how you guys have forgotten the work and effort which goes into this or how the saying goes,
"Per aspera ad astra"