Variable Specific Impulse Magnetoplasma Rocket (VASIMR)

Heimdall · 2007-04-27 17:34:54

It seems development and testing of the VASIMR technology by Franklin Chang-Diaz in Costa Rica is going very well. Does anybody know if the challenges involved make it feasible for having a finished version ready for a NASA Mars mission in, say, 2027? Would NASA consider it, or are they planning for chemical propulsion only? What benefits would be had from having a reasonably high-powered VASIMR engine as opposed to chemical propulsion for a Mars trip, aside from the radiation shielding?

GCNRevenger · 2007-04-27 18:45:31

VASIMR?

-Not worth the trouble with available or near-term power sources. Its just too big of an electricity hog to achieve the performance promised by the technology. We're talking megawatt scale generation here in an extremely light weight package that is beyond anything done to date. The cost of such an arrangement nuclear or solar is extreme and would doom the early Mars program. In fact, for a nuclear plant to achieve this kind of performance, it would have to be a vapor core reactor and solar may not be able to at all, particularly at Mars distance (42% of light at Earth).
-It only cuts trip time in half or so due to its poor thrust, and if we're going through all the trouble to make a uber-engine ship, then I'd think it should do better then that. This isn't likely to be fixed by any sort of power source even in the long term, because of the low thrust VASIMR produces.
-Chemical engines are cheap and safe. If we can do 6mo in zero gravity, then there really is no reason not to use them. VASIMR on the other hand is extremely complex, with high-power electrical conversion electronics, plasma generator, RF generators, magnetic confinement bottle/nozzle, and of course the cryogenic cooling system to keep said magnets cold. Possible? Sure. But it won't come cheap.
-The only big side benefit offered by VASIMR is the magnetic field generated by the engine might offer some protection from charged particle radiation. However, a big chemical rocket with doped plastic shielding would probably cost no more than VASIMR for Earth-Mars trips. This would be a must for manned flight around Jupiters' inner moons, but otherwise? Probably not worth it.

Now if we had power-dense, compact fusion reactors to make/heat the plasma then sure. But not until then probably.

Heimdall · 2007-04-28 03:00:08

What about other kinds of nuclear rockets? Are there any kinds of nuclear rockets which could realistically (technically) be considered for near-term NASA use? I've been going through some of your past posts concerning this subject, and I find them very interesting and enlightening.

I'd like to point out that I'm very happy that NASA is finally doing actual and realistical work in order to go to Mars and the Moon, so I'm not complaining, unlike some alt. spacer types with their sci-fi plans. Chemical is fine by me as long as it gets people there safely and according to plan -it's just that nuclear seems to promise so much possibility. Given that the VASIMR has apparently been the subject of a long-term research effort with at least some form of higher-level acceptance, I thought that maybe that was a contender.

How far away do you think practical use of nuclear rockets is, realistically, and what would the actual benefits be? Would the space program be completely transformed by NASA having access to a reliable nuclear rocket, or would the effects be more mariginal? Have materials research come up with new possibilities over the last few years which brings nuclear rocket technology closer to being a reality? Or are nuclear rockets still just a pipe dream? Would a NERVA style rocket or a gas solid core rocket be possible and practical to implement today?

GCNRevenger · 2007-04-28 07:39:42

Well, you've got basically three other nuclear rockets, all three of them thermal and high-thrust:

-NERVA solid core engines, simple proven engines with good thrust, cheap and quick to build (reltively). Basically an all-ceramic nuclear reactor with liquid hydrogen pumped through it and out the nozzle. Unfortunately, no solid of any kind can resist temperatures needed to achieve >1000sec Isp.
Isp: 900-1000sec
Dev cost: low
Dev time: low
Flight cost: medium
Side benefit: could be easily modified to generate kilowatt-scale power when not firing.
Drawback: low maximum temperature limits Isp.
-Gas Core Nuclear Rocket (GCNR), my favorite, an advanced design that uses a moving vortex of liquid hydrogen (perhaps spiked with carbon black) to confine Uranium gas or plasma in its center. Because the Uranium never touches the engine, far higher temperatures could be achieved. The design might be further refined with the use of electromagnets to compress the Uranium, reduce fuel loss, and increase reaction rate even further.
Isp: 3000sec (simple)-5000sec (refined)
Dev cost: high
Dev time: high
Flight cost: low
Side benefit: safe armored Uranium storage
Drawbacks: most complex nuclear engine
-Nuclear "Salt Water" Rocket (NSWR), Bob Zubrin's Sunday afternoon rocket idea, uses a water-Uranium salt solution sufficiently salty that it will easily go critical if you brought together a significant volume of it. This would be expelled out the back of the engine at high speed before the onset of the chain reaction.
Isp: 5000sec (low ball) - 10,000sec (high ball)?
Dev cost: medium-to-high (require in-space testing only)
Dev Time: high (require in-space testing only)
Flight cost: medium-to-high
Side benefit: Uses water for reaction mass, relatively simple design, possibly permitting easier in-space refueling.
Drawbacks:
- -Most dangerous of the three due to the natural tendency of the fuel to go critical
  -Special shielded fuel solution tank offsets waters' density advantage over Hydrogen
  -Uses large amounts of Uranium, could be expensive and is the largest security hazard.
  -Need for large amounts of Uranium could offset space refueling with mined water.
  -Large minimum ship size for high-Isp required
  -Nuclear safety nuts would scream if the solution were pre-mixed on Earth. And rightly so.

As far as practicality, I think that all three engines are possible, but probably the NERVA-style engine is the only viable near-term one, with NSWR coming in a distant second place. In the longer term its a tossup, but NERVA's low maximum performance would hinder it.

Now if you were thinking of doing the whole round trip with a single vehicle, and you didn't want to use aerobraking, then NERVA would be the only viable option within NASA's budget, since the much larger Delta-V would make the mass of chemical fuel unrealistically large.

I think that the latter two nuclear engines do show lots of promise long term, but the NERVA engines not so much. With aerobraking, getting to Mars only requires about 33% less fuel for 900sec (nuclear) versus 450sec (chemical), and the boiloff problem is worse for NERVA.

Heimdall · 2007-04-28 09:27:49

Thank you for a good answer. More questions!

Do you know of any research carried out today concerning GCNRs? Has any feasibility studies been made? Do you have any guesses about NASAs view of the technology? Or has their post-Nixon strategy of "going nowhere fast" excluded all research on new propulsion systems?

I also find it strange that VASIMR is subjected to a 20 year research effort (however limited) when the technology seems to hold so little promise or be so dependant on future breakthroughs to be at all realistic. Any thoughts on that?

GCNRevenger · 2007-04-28 11:30:50

As far as I know little work on the GCNR concept has been carried out since the ideas' invention beyond some pre-computer table-top fluid dynamics models and some low-definition physics studies. Nobody has picked it up with intent to actually build the thing yet to my knowledge.

Well, after Nixon most everything at NASA that didn't go into building or justifying Shuttle went away to large degree I bet, but VASIMR has subsisted since its inception on NASA's love for pie-in-the-sky or silver bullet technologies ("breakthrough propulsion," Scramjet SSTO, X-33).

VASIMR in particularly has also been kept going by this annoying tendency for famous scientists to scream and cry to the media when their pet project faces the wrong end of an honest cost-benefit analysis. The final Hubble servicing mission is a good example of this, the old scope' has long exceeded its design life and the cost to try and prop it up a little longer is a waste. But since the Hubble astronomers are certified celebrity scientists now NASA was left with no choice thanks to the PR disaster cancellation would entail.

VASIMR, being headed by an astronaut (star power), is actually the perfect example of this phenomenon, with almost no even medium-term applications, money is still being spent on it while budgets are tight. Witness how NASA had to try and cut the program while he was busy with a Shuttle mission, when he wouldn't have time to try and intervene. The VASIMR people are too attached to their pet project, the lack of a practical power source be damned.

The common notion that NASA managers are always the fount of evil and never the employees just isn't so. I should like to suggest that the legion of rumors from anonymous sources - and even one occasion of altered leaked documents - is also due to such employees seeking a way to derail plans they don't like.

Heimdall · 2007-04-28 13:24:02

GCNRevenger wrote:

"As far as I know little work on the GCNR concept has been carried out since the ideas' invention beyond some pre-computer table-top fluid dynamics models and some low-definition physics studies. Nobody has picked it up with intent to actually build the thing yet to my knowledge. "

So, wouldn't the case for GCNR propulsion be a very good foundation for a pressure group for constructive criticism of NASA (if only there was a way to keep the alt.space nutheads out)?

What you're saying about VASIMR research justifications and the general conundrums of large organizations like NASA sounds completely plausible, from my experience with politics and large organizations, and NASA must be one of the worst of all when it comes to infighting over resources, considering the sheer volume of public resources at stake (or play, rather...).
Too bad, but then again, without clear focus and leadership, and huge budgets, that's what's bound to happen.

I get the impression that your level of expertise and intimate knowledge of NASA inner workings means that you're probably not the guy that will stick his head out publicly with wild schemes of non-pc nuclear rockets, though ;-)

It would be great with a website where you gather together your arguments for this technology. The message would start spreading from there -"truth will out". I'd love to see that happen, and I'm sure it would attract attention in the right places after a while if it was done right. Ah well, I'll stop preaching, couldn't help myself.

Thanks for your answers, I'd appreciate your thoughts.

GCNRevenger · 2007-04-28 17:09:36

Actually, shy of some big breakthrough in the ease of simulating the engine or NASA cash infusion, I sure hope NASA doesn't invest in it... yet. The superior performance would be nice, but its not necessary for early manned Mars missions. Once we are on Mars with a little base and have a reusable lander, then a GCNR engine makes sense.

GCNRevenger · 2007-04-28 18:17:46

Oh and FYI, I don't work for NASA or any contractor nor their competitors. Just a rocket junky with a particular amusement with nuclear power.

cIclops · 2007-12-11 09:59:43

New agreement with NASA - 10 Dec 2007

This agreement provides a framework for collaboration between the parties, setting out the general conditions governing aspects of their ongoing relationship, including respective rights and obligations, and is intended to promote flexibility, cooperation, efficiency and clear communication during the next phase of Ad Astra’s maturation of the VASIMR™ technology. In June 2005, Ad Astra signed its first Space Act Agreement with NASA which led to the development of the VASIMR™ engine. By maintaining a close relationship with Ad Astra while the VASIMR™ technology is developed, NASA will be able to assess the future utility of the VASIMR™ engine in its exploration programs.

Ad Astra homepage

Rxke · 2007-12-11 13:20:09

:shock:

Wow, I totally didn't realise there were such advanced prototypes out there.

8)

qraal · 2008-02-01 15:34:37

Hi All

GCNRevenger wrote:
"As far as I know little work on the GCNR concept has been carried out since the ideas' invention beyond some pre-computer table-top fluid dynamics models and some low-definition physics studies. Nobody has picked it up with intent to actually build the thing yet to my knowledge. "

The Russians worked hard on GCNRs...

http://www.astronautix.com/engines/rd600.htm

...but the Americans abandoned their Mars program in 1970 and the Soviet leadership lost all interest.

GCNRevenger · 2008-02-01 22:12:07

I'm sure the Russians toyed with the idea, but I doubt that they ran very far with it, a high-performance GCNR engine would require a really substantial research program.

GCNRevenger · 2008-02-01 22:25:20

:shock:
Wow, I totally didn't realise there were such advanced prototypes out there.
8)

The VASIMR engine is still all cute and all, but does anybody notice the fine print? Their website just pretends the power problem is just a little detail. Again, it is not, the lack of a suitable power plant is a show-stopper for a manned VASIMR rocket.

The reduced trip time they cite (3mo vs 6mo for chemical) would require twelve megawatts and a 60% efficient plant which would have to weigh under 50MT, none of which would be anything short of a huge development project that would match or dwarf the VASIMR development. To put things in perspective, NASA and the USAF have played around with various designs, but only produce ~100kW yet weigh several tonnes.

VASIMR needs: 12MW or 12,000kW
NASA has: 100kW

A power plant would have to generate a hundred times that of previous designs, yet only weigh about ten times as much. I'm not saying that it couldn't be done, but rather it shouldn't be done.

Heimdall · 2008-02-05 02:04:46

I'm not saying that it couldn't be done, but rather it shouldn't be done.

Sounds reasonable. So what would be your dream mission architecture (propulsion, habs, ISRU etc) ?

GCNRevenger · 2008-02-05 15:39:54

For Mars? Chemical rockets for propulsion, rigid HABs if the outbound HAB ands or TransHAB for the surface if not, etc. NASA's DRM-3.0, bulked up with Ares-V size payloads instead of Magnum, would be nice.

corneliussulla1 · 2008-03-18 10:31:56

I wonder has anyone seen detaisl on the new Hyperion reactor.

This reactor is the size of a bath tub and produces around 100MWe. A version of this may just be what NEP and VASIMR in particular needs. The other good thing is it is a start up from Los Alamos and is privately funded therefore more likely to come to fruition.

I can't post URL butsearch under reactor name should leed you to info on this project

GCNRevenger · 2008-03-18 11:04:25

Not so fast,

The trouble with this reactor is two fold: first off, how do you get the energy out of the core and convert it to electricity? In the Hyperion concept, this is with a heavy steam turbine and low-temperature radiator/condenser. Getting such a contraption on a space vehicle is going to be extremely heavy.

Second, the core operates at a fairly low temperature, which will make cooling systems big and heavy as well.

Making a dozen-megawatt reactor light enough is easy, cooling the reactor is the hard part.

corneliussulla1 · 2008-03-18 14:18:54

Well I am no Reactor Engineer although i am an electronic's one. You can use thermo electronics to convert the power. There is a lot of work going on in this field in the car industry to raise the effeciency of gas vehicles

These things are not space ready but they are plausable answers to they may be plausable answers to thermo electric problem

With regard to core temp. It is true that the current design envisages using uranium hydrates and operates at 400 to 800 degrees. However there is another design which uses thorium hydrates and this can operate at 1900 degrees. I think nerva was planned to operate at 2800.
I am not sure of the calculations around heat readiators in space but this has got to help.

What do you reckon, is this a possible near term solution say 10-20 years

GCNRevenger · 2008-03-18 16:12:09

Thermoelectrics don't have the needed efficiency; for instance the SNAP-100 reactor that the USAF was working on actually put out 2MWt of heat energy, but the poor conversion efficiency of the thermoelectric converters it used (5%, 5W of electricity from 100W heat) limited its electrical output to only 100kWe. Even a doubling of this to 10% would not yield enough power from a reactor of practical mass to run VASIMR.

The core in the Hyperion reactor uses Uranium Hyride btw, which i any case won't get hot enough, and Thorium Hydride on its own can't undergo fission. And, while NERVA could operate at very high temperatures, the core literally melted/ablated at these temperatures and were not suitable for long-duration use at those power levels.

What we need is something like this: http://www.inspi.ufl.edu/gcr.pdf ...the cost of which would bankrupt NASA within the next 10-20 years, if they had to develop this along with a massive VASIMR engine.

corneliussulla1 · 2008-03-19 07:14:10

When was the work on SNAP 100 done. One company Powerchip reckons there technology can get conversion rates as high as 70-80% carnot Efficeincy. Even at 50% this would reduce the radiator size quite significantly. Go to this site input to calc

http://www.powerchips.gi/technology/pcalc.shtml

However i am dubious about this technology it appears to be to good to be true. I wonder how big the company is and what they have done to date. A lot of these companies are slideware although they have a number of patents

The Hyperion reactor produces about 70 MW thermal and around 27MW Electrical energy

Regards Thorium Hydride it is mentioned by Hyperion guys as part of there patent i think. I am not sure how they do it but they appear to think they can.

So if we assume a 50% Thermal to Electrical conversion as described by Power chip and if we can get the reactor to 1900 degrees. Would this be a practable solution?

See the first 12MWe VASIMR mission to mars here

http://www.youtube.com/watch?v=Zj53rVWK5z0

I have seen that INSPI stuff before but there is no detail at the site on the solution. I dont think they have any real funding behind their research. If someone elses technology developed for everyday use on earth can be doctored to space it would provide a much more likely solution

corneliussulla1 · 2008-03-19 07:32:06

Here is another qauntum well thermo electronic technology that pushes effeciency up from 5-10% today to 50-60%. It is especially effective the larger the change between hot and cold and that suits our space application very well. See slide 3 and 14 of below presentation. This also looks like real technology that has been demonstrated in the lab

http://www1.eere.energy.gov/vehiclesand … 7_bass.pdf

GCNRevenger · 2008-03-19 12:58:07

Yeah that does sound awfully good to be true, 50% efficiency?

The latter link you provided had a 25% efficiency if I read it correctly, which is pretty darn good... the catch is its only good for 6mo and only at lowish temperatures thats going to make the radiator system awfully heavy. You also need a very effective radiator to hit low enough temperatures.

Its a good start though

Edit: I am a little worried that such a device might not stand up to intense radiation all that well however.

corneliussulla1 · 2008-03-20 05:39:48

The key to success with thermo electronics is getting a higher ZT. At present the best materials have a ZT of 4.5. These are new materials created using nanotechnology. You can see on slide 3 if the hot side is 1000 C or 1273K then with cold side at around 320K we can get 45-50% effeciency. The reason they show at lower temperatues is because the technology is being developed for Cars to extract energy.

Not sure about suitability for space however JPL has done some work on Thermoelectronics and believe that it is a good solution for radio isotope power systems see slide below. This is slightly out of date as it talks about older technology than the systems discussed above you can see that they are talking about ZT of 1.2 or 1.4. The research done by the car industry has realy changed the ballpark as far as thermoelectronics is concerned

http://trs-new.jpl.nasa.gov/dspace/bits … 5-1662.pdf

So with Hyperion we are taking about a 27MW Elect and 70 Mw Thermal assuming 45% eeffecient themo electronics we need to radiate 38,5 Mega watts Thermal and can use about 60 Mwe to drive the VASIMR engine. That is a lot of thermal energy to radiate but with this system we are getting to Mars in about 6 weeks and potentially Jupiters moons inside 6 months using technologies which are under development by private industry at present. Obviously there are large hurdles to put this stuff in space but it is not like starting from scratch.

Not sure how all this effects radiator size but if this sort of technology can be scaled to the type of appplication we are talking about it must have a significant effect on the viability of Mars mission using

This link is to some research done on radiator size for multi megawatt radiators in space aplications

http://stinet.dtic.mil/oai/oai?verb=get … =ADA351428

JoshNH4H · 2008-03-20 14:03:14

wouldn't sterling cycle generators be much more efficient than thermocouples?

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#1 2007-04-27 17:34:54

Re: Variable Specific Impulse Magnetoplasma Rocket (VASIMR)

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Re: Variable Specific Impulse Magnetoplasma Rocket (VASIMR)

#3 2007-04-28 03:00:08

Re: Variable Specific Impulse Magnetoplasma Rocket (VASIMR)

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Re: Variable Specific Impulse Magnetoplasma Rocket (VASIMR)

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Re: Variable Specific Impulse Magnetoplasma Rocket (VASIMR)

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Re: Variable Specific Impulse Magnetoplasma Rocket (VASIMR)

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Re: Variable Specific Impulse Magnetoplasma Rocket (VASIMR)

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Re: Variable Specific Impulse Magnetoplasma Rocket (VASIMR)

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Re: Variable Specific Impulse Magnetoplasma Rocket (VASIMR)

#10 2007-12-11 09:59:43

Re: Variable Specific Impulse Magnetoplasma Rocket (VASIMR)

#11 2007-12-11 13:20:09

Re: Variable Specific Impulse Magnetoplasma Rocket (VASIMR)

#12 2008-02-01 15:34:37

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Re: Variable Specific Impulse Magnetoplasma Rocket (VASIMR)

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Re: Variable Specific Impulse Magnetoplasma Rocket (VASIMR)

#16 2008-02-05 15:39:54

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#17 2008-03-18 10:31:56

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#18 2008-03-18 11:04:25

Re: Variable Specific Impulse Magnetoplasma Rocket (VASIMR)

#19 2008-03-18 14:18:54

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