NASA Plans Test of New Plasma Drive

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."

Comments

Yes, attach it to the ISS

[BigDaddyOttawa]

What could possibly go wrong?

Re:Yes, attach it to the ISS

[oldspewey]

It's okay as long as they remember to leave the parking brake on.

Re:Yes, attach it to the ISS

[freddy_dreddy]

I think the point here is to exploit the recent discovery of water on Mars. With conventional fuels you have to take the return-charge with you. Concepts like these allow them to harvest Hydrogen on Mars for the return trip, which is pretty useful. The painful detail (apart from the complexity) is the mechanism for braking - you're f*d if that fails.

Re:Yes, attach it to the ISS

[Amouth]

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 (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.

Re:Yes, attach it to the ISS

[Omega996]

yeah, designing and building a bussard collector isn't that hard, it just needs something that can generate a magnetic field that doesn't diminish as the inverse square of the distance, since your magnetic or electrostatic funnel would have to be huge to pull in enough material to be worthwhile (even inside the heliopause). unless you're planning on not using a vehicle with any live crew or any sort of electronic equipment. I'm sure the difficulty of initiating and sustaining a proton-proton fusion to generate plasma is just a quick fix (no doubt you've already figured out the materials and fuel source for your carbon-nitrogen-oxygen fusion catalyser), as are the problems associated with getting the ramjet to speeds above the solar wind (unless the vehicle is making a quick one-way trip into the sun).

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*

Makes me happy

[SSIlver2002]

It's stuff like this that makes me happy and brings a huge smile to my face. It also makes my imagination go wild! I hope something like this gets implemented sooner than later.

plasma exit velocity?

[oldspewey]

Neither summary nor TFA give any indication of the velocity of plasma exiting the engine. How does it compare with chemical rocket? Ion drive?

Re:plasma exit velocity?

[Intron]

We can guess that it is similar to the DS-1 Ion drive which propels Xenon ions at 30 km/sec.

Re:plasma exit velocity?

[wurp]

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.

Re:plasma exit velocity?

[DarthVain]

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...

Re:plasma exit velocity?

[bodino]

Wiki - the source of all knowledge - has some good details.

http://en.wikipedia.org/wiki/Variable_specific_impulse_magnetoplasma_rocket

Re:plasma exit velocity?

[AKAImBatman]

VASIMR (Variable Specific Impulse Magnetoplasma Rocket) is a variation on the Magnetoplasmadynamic thruster (MPDT) 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. 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.

Re:plasma exit velocity?

[HRogge]

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).

Re:plasma exit velocity?

[avandesande]

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.

Re:plasma exit velocity?

[Dancindan84]

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.

Re:plasma exit velocity?

[rk]

(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.

Re:plasma exit velocity?

[Phil Karn]

I assume you meant "power in the exhaust", not "energy as thrust"?

Re:plasma exit velocity?

[GleeBot]

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).

Nice to see fact moving faster than fiction

[CRCulver]

Who knows if this thing will work out, but it would be amusing if it did. In histrilogy beginning with Red Mars , Kim Stanley Robinson had interplanetary journeys being trimmed down to such short lengths only a couple of hundred years from now, and KSR's work tried hard to be scientifically plausible.

Re:Nice to see fact moving faster than fiction

[spun]

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.

All they have to do now...

[fiannaFailMan]

...is optimize the plasma conduits, although they'd better make sure not to divert too much power away from the main deflector array, I'd hate to have to reconfigure that thing yet again.

Re:All they have to do now...

[lgw]

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.

Re:All they have to do now...

[SlowMovingTarget]

I can think of a number of reasons:

1. It's harder to run out of magnetic fields than it is to run out of copper.
2. Exploding Plasma is way cooler than non-exploding copper. I suppose you could make copper plasma, but see number 1.
3. The old Constitution class used copper wiring, but the space rats and non-corporeal vampiric fart-wraiths kept chewing through it (begin dramatic STOS music). With plasma conduits, the whole ship is one big giant bug zapper.
4. EPS conduits can also predict pregnancy when you pee on them. I'd like to see your copper wire do that!

horray!

[nawcom]

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

[Anonymous Coward]

...have to be playing Magic Carpet Ride

New, it is not

[ivanthered]

The VASIMIR has been in developement since 1979.
http://en.wikipedia.org/wiki/Variable_specific_impulse_magnetoplasma_rocket

I wonder where they will get the 200 kW to drive it from?

-------------
http://borislegradic.blogspot.com/

Re:New, it is not

[Fast Thick Pants]

Sounds like a job for a small, contained nuclear reaction.

Re:New, it is not

[qoncept]

I'm sure in 1979 they could walk in to any corner drug store and buy plutonium, but this is 2008. No, no, the only thing that could generate that kind of electricity is a bolt of lightning, but unfortunately you never know when or where it's going to strike.

Re:New, it is not

[Squiffy]

Seriously, it's only 200 kW? That being the case, a few square meters of solar panel should do just fine, even at Mars like distances, you'd still be getting enough energy that it would be trivial ( something like 5 square meters would be sufficient at even Mars furthest distance of 2.5EE6 KM from the sun)

Yes, I know my figures aren't exact, but this is /., so I'm sure someone will come along and actually do the calculations.

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.

Re:New, it is not

[GleeBot]

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

Summary: They're pushing a very very tiny amount of mass very very fast. For a given amount of thrust, this is very efficient in terms of mass, terribly wasteful in terms of energy.

Engine?

[jdb2]

Engine? The scaled down test version might use something "conventional" as its power source, such as an RTG. But, in order for the VASIMIR to work at full-scale, say in a human Mars mission, the power source is going need a VERY large energy density -- something not achievable with any known and tested chemical reaction. I have no idea why they call the power source the "engine" but perhaps it's to placate the environmentalist wackos who will go nuts after hearing the obvious : the "engine" or power source is a nuclear reactor. It will be interesting ( and probably funny ) to see how this plays out in the long run if NASA sticks with this technology.

jdb2

Re:Engine?

[PeterBrett]

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.

Just make sure...

[mdm-adph]

...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.

Re:that's all good, but..

[oldspewey]

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?