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Plasma Rocket Successful Full Power Test

Posted by ScuttleMonkey on 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."

5 of 169 comments (clear)

  1. Plasma Rockets Suck. by TheRealZero · · Score: 5, Funny

    LCD rockets have sharper colors.

  2. Re:The interesting part (to me anyway) by Anonymous Coward · · 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.

  3. Re:Are there useful numbers on this? by bornyesterday · · Score: 5, Informative

    check out http://www.adastrarocket.com/Jared_IEPC07.pdf

    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

  4. Re:The interesting part (to me anyway) by Anonymous Coward · · 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.

  5. Physics doesn't work like you seem to think by MarkusQ · · Score: 5, Informative

    accelerating fuel forward so you can spit it back later.

    I have no idea what that even means, or is even supposed to mean. I quote it only to highlight that the source of your skepticism seems based entirely on a gross misunderstanding of the technology involved.

    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 other advantage is maximum top speed. If your hydrazine rocket can expel mass at, say, 1000 mph (making numbers up here) then the top speed of your rocket is 1000mph for reasons I hope are obvious.

    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