VASIMR

[Aero]

Did we know about this contract for Ad Astra Rocket Company? I know the project has been discussed here.
https://www.fbo.gov/index?s=opportunity ... e&_cview=0

[glemieux]

I remember seeing this around here, but I could be mistaken. I have seen it reported on some space exploration blogs I haunt.

This along with NASA's recent change in focus and Administrator Bolden giving VASIMR as an example of upcoming technologies to be funded and demonstrated at the Feb 6th press conference, gives me a sneaking suspicion that NASA is hoping Ad Astra Rocket company will have success and enable trips to the Moon with their tug concept before they get a new heavy launcher together between 2020 and 2030.

[Betruger]

You should scan thru the NasaSpaceFlight forums.

[Josh Cryer]

Old VASIMR hype paper (PDF): http://dma.ing.uniroma1.it/users/bruno/Petro.prn.pdf

Discusses a Mars mission. Bolden wants to go to Mars.

First time in the history of the Administration (NASA) that Advanced Propulsion was being seriously considered for manned flight. First time. Usually Advanced Propulsion gets a few million a year for research but never ever does it get any money for development for manned vehicles. It's just never happened. The closest thing we ever got was ion, and that proved fruitful for probes.

I'll never forget how amused I was by Ares I guys talking about how much "new technology" was being put in to the thing, and how it was so advanced. Nevermind the fact that all that "new technology" was needed because the design was atrocious to begin with.

There's so much potential out there, too. My current favorite is Dusty-M2P2 (PDF): http://www.rbsp.info/rbs/RbS/PDF/nffp2003.pdf

[Josh Cryer]

Where are we going to get a 200MW (megawatt) space nuclear reactor? Won't that be freakishly huge?

[MSimon]

Where are we going to get a 200MW (megawatt) space nuclear reactor? Won't that be freakishly huge?

The reactor is small. It is the radiators that are the problem.

[Betruger]

If we are to implement Franklin's proposed VASIMR 40 day trip time to Mars from Earth, we need a minimum of 500 MW-e to get it done. [...]

http://forum.nasaspaceflight.com/index. ... #msg538144

And further calcs downstream of that post.

[Aero]

If we are to implement Franklin's proposed VASIMR 40 day trip time to Mars from Earth, we need a minimum of 500 MW-e to get it done. [...]

http://forum.nasaspaceflight.com/index. ... #msg538144

And further calcs downstream of that post.

An interesting link down stream of that post.
http://www.rbsp.info/rbs/RbS/PDF/aiaa05.pdf
41st AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, July 10-13, 2005, Tucson, AZ
Dusty Plasma Based Fission Fragment Nuclear Reactor

A 10 year mission to the 550AU gravitational lens point would require only 180kg of nuclear fuel, and a
350MW reactor power, well within the calculated thermal limit of 1GW. A 30 year trip to the Oort cloud at
0.5 Ly is more strenuous, requiring a 5.6 GW reactor. And a 50 year trip to Alpha Centauri, 4 Ly distant,
is probably not feasible, requiring a 208 GW reactor, and consuming 240 tons of ¯ssion fuel.

[Aero]

Questions on
http://www.rbsp.info/rbs/RbS/PDF/aiaa05.pdf
41st AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, July 10-13, 2005, Tucson, AZ
Dusty Plasma Based Fission Fragment Nuclear Reactor

This seems to be some similarity between the magnetic containment used in this fission reactor and Polywell. The fission fragment reactor achieves both direct conversion with claimed 90% effeciency and direct rocket thrust from fission products resulting in extremely high ISP. It does suffer from the need for a massive moderator blanket, though and I expect that any ship configured using these engines would require shielding. I wonder if a similar design is possible by replacing the fission reactor with a Polywell. It seems that if so, the mass should be smaller, hence performance might be improved.

Another thought. Since the fission fragment reactor can generate either electricity by direct conversion, or thrust from reaction products, does this make it useful as the basis for a hybrid system using rocket thrust for acceleration to ram speed, and the Bussard Ram Jet for cruise acceleration, hence saving on board fuel mass?

[Josh Cryer]

If we are to implement Franklin's proposed VASIMR 40 day trip time to Mars from Earth, we need a minimum of 500 MW-e to get it done. [...]

http://forum.nasaspaceflight.com/index. ... #msg538144

And further calcs downstream of that post.

Thanks for that link.

[Roger]

I think it should be important to note that we have every indication that a 1000-1200MW polywell will be vastly smaller than a 1000-1200MW fission nuke.

VASIMIR will be used only if Polywell fails.

[jmc]

There's one thing I still don't get about VASIMIR which that presentation left me even more confused about.

Non- resistive plasmas are eternally stuck to the fieldlines they are on, the plasmas emitted from VASIMIR into space will be low density and so this statement should apply.

Ampere's law clearly states that magnetic fieldlines must inescapeably make unbroken circles around the currents that produce them.

Thus the magnetic fieldlines comming out of the rocket created by the electromagnets in the rocket make large loops through space and reenter through the front of the rocket.

If the plasma can't disconnect from the fieldlines, then this plasma will also go around in a large loop and end up hitting the front of the spacecraft and delivering no net impulse.

So how is the plasma supposed to disconnect itself from the fieldlines? Does it even disconnect from the fieldlines or is the whole VASIMIR project a pie-in-the-sky fraud?

I believe John Slough mentioned in his list of advantages of the Propagating Magnetic Wave Accelerator that the FRC configurations that were shot out the back end were magnetically disconnected from the spacecraft unlike rival plasma propulsion concepts.

So how is this problem supposed to be overcome?

[Betruger]

I obviously don't know because I wasn't there in person, but I doubt they'd not have noticed this in trial firings of the engine.
http://rocket.itsc.uah.edu/u/cassibj/VASIMR
Scroll down to Engineering Limitations for a couple of second or third hand details.


Wikipedia says

One of the remaining untested issues is: potential vs actual thrust. That is, whether or not the hot plasma actually gets detached from the rocket. This will be confirmed in 2009 when a VX-200 engine will be installed and tested in a large enough vacuum chamber.

IIRC this
http://www.adastrarocket.com/Release_20 ... 9Final.pdf
didn't answer the question. Could be wrong though, there might be some clue in that report.[/img]

[93143]

VASIMIR will be used only if Polywell fails.

VASIMR is a primitive CSR-B. It's a perfect match for Polywell.

[Josh Cryer]

VASIMIR will be used only if Polywell fails.

I hope not. We can't make a fission reactor efficient enough to keep us from having to build a ship something like 2/3rds air craft carrier sized (because of the necessary radiators). Never-mind the fact that we can't currently make 2 5MW reactors at less than .5 kg/kw It would require a revolution in reactor design and efficiency.

What is remarkable is that the more detailed budget proposal mentions NUCLEAR THERMAL.

I was shocked by this revelation. Though I suppose they do have 15 years to build it and by then nuclear should be well on its way to making a comeback and the political environment may be more receptive of it.

Stupid Three Mile Island.

BTW, compare NTR to NEP:





VASIMR is going to be effectively the same kind of design as NEP. The Ad Astra concept art is not capable of radiating away the heat produced by their fission reactor.