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NASA Plans Test of New Plasma Drive
Posted by
timothy
on Wed Aug 06, 2008 01:43 PM
from the please-don't-bring-carrie-ann-moss dept.
from the please-don't-bring-carrie-ann-moss dept.
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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Technology: Plasma Rocket Successful Full Power Test 169 comments
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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Yes, attach it to the ISS (Score:4, Funny)
Re:Yes, attach it to the ISS (Score:5, Funny)
Parent
Re:Yes, attach it to the ISS (Score:4, Insightful)
Parent
Re:Yes, attach it to the ISS (Score:5, Interesting)
actualy because this design heats the gas to a plasma state then uses EM waves to move it to create thrust - the idea could be used on just about any gas - your effeciency would be how much energy goes into heating it to a plasma state and keeping it there.
this is a great idea because they could design one engine and while the gas is consumed it could be replaced by any gas - and electricity is the true source of the power to run the engine..
we already know what gasses are readly avaliable on mars - design one to run on say H to get there (assume Hyrdogen is the easiset to heat to plasma sate) but have the engine also able to run on the gasses from Mars.. then when it gets there refill the tanks.. carge up the batteries (or use a nuke power source on the thing) and come on back - or keep going.
think of a ship with this type of drive.. then think about adding say a Bussard collector http://memory-alpha.org/en/wiki/Bussard_collector [memory-alpha.org] (i know we would have to invent a bussard collector but the idea is not that hard)
if this works they way the say it does - it is going to be one of the best propultion advances for traversing our solar system.
and with us having probes leaving our system - the data from there might show that there is a good ammount of particals in the space between systems.. if that is true then you could use this to send probes to other systems. sure it would take awhile but i bet they can alwasy make improvements.
Parent
Re:Yes, attach it to the ISS (Score:5, Interesting)
not much to do there, at all. You should get right on it, and we'll be heading toward Mt. Lookitthat within a few months. *rolleyes*
Parent
Re: (Score:3, Interesting)
Re: (Score:3, Funny)
Careful, you might end up buried partway in a cliff [snopes.com]with a plasma drive hanging out your rear bumper.
Actually, the (supposedly) true story [blogspot.com] of the Rocket Car Legend is a rather interesting read.
Makes me happy (Score:4, Insightful)
plasma exit velocity? (Score:5, Interesting)
Re:plasma exit velocity? (Score:5, Informative)
Parent
Re:plasma exit velocity? (Score:5, Informative)
From wiki:
Current VASIMR designs should be capable of producing specific impulses ranging from 3,000 to 30,000 seconds (jet velocities 30 to 300 km/s). The low end of this range is comparable to some ion thruster designs. By adjusting the manner of plasma production and plasma heating, a VASIMR can control the specific impulse and thrust. VASIMR is also capable of processing much higher power levels (megawatts) than existing ion thruster electric propulsion designs. Therefore it can provide orders of magnitude higher thrust, provided a suitable power source can be provided.
Parent
Re: (Score:3, Informative)
Let's see, a kiloton of TNT = 4 x 10^12 joules all released in a fraction of a second.
A megawatt of power for 30,000 seconds (8 hours) = 3 x 10^10 joules, so no nuking here.
Also, unless I misunderstand this, you don't get more energy as thrust than you can put in as electricity. So to get that megawatt of power out, you need a megawatt of electricity in. Solar panels will only get you 1300 W / m^2 with 100% efficiency at the Earth's orbit. I guess you need a really long extension cord.
Re:plasma exit velocity? (Score:4, Informative)
Parent
Re:plasma exit velocity? (Score:5, Interesting)
This sounds a lot to me like it *is* an ion drive. I didn't RTFA, but a plasma is characterized by a separation of the electrons from the nuclei. The only difference between that and an ion drive is that not necessarily all electrons are stripped from the atom in an ion drive.
I don't know how (or if) you would distinguish between ionic hydrogen and a hydrogen plasma (hydrogen atoms have only one electron...)
In both cases you give the propellant momentum with either electric or electromagnetic force, and both are much more efficient than chemical rockets. I would also expect both to have miniscule thrust compared to chemical rockets, and hence only be appropriate for navigation when you already have orbital or superorbital velocities.
Parent
Re:plasma exit velocity? (Score:5, Informative)
Ion drives use electromagnetic fields to accelerate particles with an accelerator. Most times they use heavy atoms like xenon.
VASIMIR makes plasma from light elements like hydrogen and then use electromagnetic fields to heat the plasma... by controlling the temperature you can change the thrust/momentum the engine creates.
(at least that's what I heared).
Parent
Re:plasma exit velocity? (Score:4, Funny)
More importantly how does it compare to twin ion engines? The empire wants to know!
QIE - Quad Ion Engines, now with the added benefit that they don't look like bowties. Under utilized as the name isn't very catchy...
Parent
Re:plasma exit velocity? (Score:5, Informative)
Wiki - the source of all knowledge - has some good details.
http://en.wikipedia.org/wiki/Variable_specific_impulse_magnetoplasma_rocket [wikipedia.org]
Parent
Re:plasma exit velocity? (Score:5, Informative)
VASIMR (Variable Specific Impulse Magnetoplasma Rocket) [wikipedia.org] is a variation on the Magnetoplasmadynamic thruster (MPDT) [wikipedia.org] that has been in development for a decade or two. These thrusters are coveted for their rare combination of high specific impulse (i.e. efficiency) and thrust to weight ratio (power). Such a combination makes them ideal for manned missions, as they allow space craft to fly under constant, high powered thrust. This is the "holy grail" of space travel because it cuts down the TIME in flight significantly. Thus the summary's mention of a 90 day flight time to Mars. (Normal flight time using a minimal Hohmann Transfer is ~1.5 years.)
Obviously, the exact thrust numbers depend upon the rocket. However, the VASIMR rockets have a range of specific impulses from 3,000 to 30,000 seconds. You can see how that compares to Ion Thrusters here [wikipedia.org]. Chemical rockets tend to top out at 500 seconds and thus don't even place when compared to VASIMR or Ion thrusters. The only reason why we want to keep using chemical rockets once we have better thruster technology is that all these new technologies lack the thrust to weight ratio to get a rocket off the ground. i.e. They are only good for space travel. Atmospheric flight need not apply.
Parent
Re:plasma exit velocity? (Score:5, Informative)
(Normal flight time using a minimal Hohmann Transfer is ~1.5 years.)
I think you forgot to divide by two. The duration of the whole Hohmann Earth/Mars transfer orbit is about this long, but you only use half of it to get there.
Parent
Re: (Score:3, Interesting)
Good catch. So 8.5 months [iki.rssi.ru] for a one-way trip vs. 3 months. I'll take the VASIMR any day of the week. :-)
Re: (Score:3, Interesting)
This is the part I don't get, but you probably do. Why would I lower the exhaust speed, instead of lowering the mass?
The distances a spacecraft can travel in a given time are limited by the mass of "stuff" it can throw back multiplied by the speed, with which it is thrown. So, one would think, the most efficient engine would be throw "stuff" out as fast as it can, and if lower thrust is desired at times, it would th
Re:plasma exit velocity? (Score:5, Informative)
Actually, the main reason to have a variable Isp (specific impulse) engine is because there's a direct trade-off between Isp, and energy.
Note that momentum transfer increases linearly with velocity and mass, but kinetic energy increases linearly with mass and with the square of velocity. Thus, to make a given amount of mass go faster requires a lot more energy.
A more concrete example: You want to impart a total impulse of 2MV. You can either get it throwing out a mass M at 2V (mass efficient), or by throwing out a mass 2M at V (energy efficient).
In the first case, you use 1/2 M (2V)^2 = 1/2 M 4V^2 = 2MV^2 energy, while in the second case, you use 1/2 2M V^2 = MV^2 energy, or half as much, for the same total impulse. This only gets worse the bigger the velocity difference gets.
Often, the limiting factor in electric propulsion technologies like these is the power supply, not the thruster. Generally, to get the max Isp all the time you'd need a power supply so massive (like a nuclear reactor) as to completely throw off the mass fraction.
So generally, the way these systems are proposed to be operated is with a fixed power budget, and switched between mass efficient, low thrust mode (for long term delta-V), and mass inefficient, high thrust mode (for certain maneuvers).
Parent
Re:plasma exit velocity? (Score:5, Funny)
Google 'microwave plasma balls' and you will get the idea.
I'm completely in awe that I didn't get a single porn site on the front page doing that search.
Parent
Nice to see fact moving faster than fiction (Score:4, Interesting)
Re:Nice to see fact moving faster than fiction (Score:5, Interesting)
Fact is often capable of moving faster than fiction, it just takes a collective decision to make it so. We could have been to Mars already, just like we could be feeding everyone in the world. We just don't care enough.
Parent
All they have to do now... (Score:4, Funny)
Re: (Score:3, Interesting)
And this is superior to simple (relatively non-lethal) copper wires because...?
Re:All they have to do now... (Score:4, Insightful)
You can only put so much current through a busbar. What do you do when a solid copper bar 4 inches across won't carry the power you need? Eventually the size and mass of the busbar required make scaling up in power impractical. For drives, weapons, computer cores, and the like it makes sense.
Of course, that doesn't explain why the bridge consoles exploded regularly - that's just lowest-bidder construction.
Parent
Re:All they have to do now... (Score:4, Informative)
I can think of a number of reasons:
Parent
cool (Score:2)
all is left now is for someone to come up with a warp drive :p
horray! (Score:4, Funny)
we will bring the name of Jeebus to Mars before the Apocalypse that Revelations speaks of begins.
*runs away after starting un-needed religious flamewar*
But the radio signals (Score:3, Insightful)
...have to be playing Magic Carpet Ride
New, it is not (Score:5, Informative)
The VASIMIR has been in developement since 1979.
http://en.wikipedia.org/wiki/Variable_specific_impulse_magnetoplasma_rocket [wikipedia.org]
I wonder where they will get the 200 kW to drive it from?
-------------
http://borislegradic.blogspot.com/ [blogspot.com]
Re:New, it is not (Score:4, Informative)
Parent
Re:New, it is not (Score:5, Funny)
Parent
Re:New, it is not (Score:5, Informative)
From the article you linked, the Earth gets 1366 Watts per square meter. 200000/1366 = 146.4.
Near Mars, which gets about half of that flux, you need about 300 square meters.
Parent
Re: (Score:3, Informative)
I wasn't arguing against the use of solar panels. I was correcting OP's arithmetic.
I forgot to include a treatment of the actual efficiency of the solar panels we know how to build. We can build 18% efficient panels, and we might have figured out how raise that efficiency to 50%, so the actual area would be between 300/.5 and 300/.18 (i.e. 600-1700) square meters.
Re: (Score:3, Informative)
A bit simplified, but here are the basic physical relationships:
Power = Energy / Time.
Energy (kinetic) = 1/2 Mass * Velocity^2.
Force (thrust) = Impulse / Time
Impulse = Mass * Velocity.
Over a period of 1 second (Time = 1):
Energy = 50 kW * 1 second = 50 kJ = 50000 kg m^2/s^2 = 1/2 MV^2
M = 2 (50000 kg m^2/s^2) / V^2
Impulse = 0.5 N * 1 second = 0.5 kg m/s = MV
M = (0.5 kg m/s) / V
(0.5 kg m/s) / V = 2 (50 kg m^2/s^2) / V^2
V = 2 (50000 kg m^2/s^2) / (0.5 kg m/s)
V = 200 000 m/s = 200 km/s
M = 2.5e-6 kg = 2.5 mg
Summa
Engine? (Score:5, Interesting)
jdb2
Re: (Score:3, Informative)
I think the parent poster was trying to differentiate between an RTG (like Voyager has) which relies on the natural decay of radioactive isotopes and a full-bore nuclear fission reactor which induces decay with a neutron chain reaction.
Re: (Score:3, Interesting)
Good luck with that. Not only a nuclear reactor, but a heat exchanger, a turbine, and a generator.
Uhhhhh? Have you ever heard of nuclear thermal rockets? NASA's NERVA [wikipedia.org] program? You know a nuclear reactor can heat substances other than just water. I don't know if you were trying to be funny because "a turbine, and a generator" is just stupid.
That's a lot of complexity for a space mission.
And what space mission is not complicated? There's this thing called "technology" that improves exponentially with time and better technology allows greater complexity.
There are more direct ways to generate electricity with nuclear reactions, but none are really practical for this sort of power output, that I'm aware of. I'm thinking a more straightforward application of nuclear power would work better. Something like this. [nasa.gov]
I had thought of Antimatter, but we're talking about a near term mission that uses proven and teste
Re:Engine? (Score:5, Informative)
Good luck with that. Not only a nuclear reactor, but a heat exchanger, a turbine, and a generator. That's a lot of complexity for a space mission.
Look up the SP-100, which was an interesting NASA project designing a small nuclear fission reactor specifically for safe space use. One of the nice things about running a reactor in space is the fact that you only need radiation shielding in the direction where you've got sensitive equipment (i.e. crew). One of the bad things about running a reactor in space is trying to keep it cool.
Parent
Gaseous Core Nuclear Reactor (Score:3, Interesting)
A gaseous core reactor would radiate ultraviolet energy directly to the hydrogen, eliminating the need to generate electricity. Take a look at this article [nuclearspace.com] about a hypothetical design for a non-polluting, 100% reusable nuclear rocket using the Saturn V form factor that could lift 1000 tons of payload into Earth orbit and return an equal payload to a powered landing.
Re: (Score:3, Interesting)
Subm
Just make sure... (Score:4, Funny)
...and get the ownership rights for the drive squared away before you make the trip to Mars -- the last time this happened, the resulting legal battles (between the UN and some free-love hippie with a strange fixation for water) lasted for years.
VASIMR Info available on Atomic Rocket Page (Score:3, Interesting)
Try this Atomic Rocket website [projectrho.com] for some more information on this type of engine outside of Wikipedia. What's interesting about this type of engine is that it's capable of trading thrust (what you want to liftoff) for Specific Impulse (what you want in orbit to get best reaction mass efficiency).
This is a pretty good site for information on all types of potential/possible/theoretical propulsion systems, and what it would take to do "real" solar system space travel. That being said, space travel (even within the bounds of just our solar system) via our current level of technology bites.
As someone else noted, this type of propulsion requires about 10MW of electrical energy to function. That energy is not provided by the propulsion system. Something else has to provide it in a compact, dense and energetic form- namely a nuclear reactor onboard the craft. That's why this type of engine shows up at the "Atomic Rocket" website, even though the engine itself doesn't use any nuclear reactions. Some people might not appreciate that the exhaust is not radioactive, as the power plant is just used for electricity.
Unlike a chemical rocket, a spacecraft using this engine would be able to get to orbit with some payload, and would not resemble "a disintegrating totem pole" getting there. Unfortunately, it also requires a nuclear reactor, a VASMIR engine, a large amount (50-75% of the whole thing) of reaction mass, and probably, wings [projectrho.com].
Exactly What Neds To Be Done (Score:3)
This is exactly what needs to be done: Provide more speed.
Combine that with a cheap and reliable way to get to LEO and you have the beginnings of a real exploration of the Solar System.
Re:that's all good, but.. (Score:4, Insightful)
I wonder, aggregate across the internet - how much storage, energy, and bandwidth is wasted by pointless memes?
... and on the day that the internet crosses some critical threshold in computing and storage capacity and actually becomes a self-aware entity, will it be really annoying?
Parent
Re: (Score:3, Funny)
"I can has DESTROY ALL HUMANS? LOLZ."
[The slashdot yelling filter has not achieved the level of sentience necessary to comprehend satire.]
Re: (Score:3, Funny)
Too soon man, too soon.