Polywell In Space? NASA funding?

[ladajo]

Yes the curent idea is to go all LM-2500 variant gensets. Even now, the last go round I saw on plant line up was a reduction gear with one Power Turbine and one Electric drive. Ironically, one LM-2500 driven Power Turbine can run the shaft at 5/6 capacity. The second engine at full tilt only adds 1/6. Gotta love the power function.

The envisoned rig is the GT/Electric version of CODAG.

We'll see where it goes.

They still have not cracked the nut so well regarding load smoothing for GTGs on Warships driving propulsion. Warships are not commerical straight liners. They, by the nature of the business, race about like small kids in a bouncy tent. There is an initiative to re-wicker engineering managment along the lines of MSC and the Civilian constructs, but so far telling navy bridge teams to drive around like a commercial vessel is not working so well. Go figure.

[Tom Ligon]

I had barely started with EMC2 when I took a message from someone at NASA bugging Dr. Bussard for another proposal, evidently for some push called "Strategy F". If you want to know how serious it was, do a search. I've found nothing on it ... probably never made it out of the cube farm. The idea was to find a way to use fission of fusion to power a way to Mars, and at the time there was a 2/3 chance that would be a Bussard idea. The options were essentially to revive the fission propulsion program NERVA (derived from Rover), use the Polywell ideas Bussard had been writing about (archives at Askmar.com for any new forum participants), or find some way to use a tokamak, which was essentially a non-starter due to the size.

Alas, the folks asking had no money. Evidently what they were doing was desperately searching for a program so they could go on drawing a paycheck. Bussard had apparently been feeding them freebies for a while but seeing nothing in return.

NASA has known about the Polywell and propulsion possibilities at least since the mid 90's and it has some people there who would dearly love it ... it would power VASMIR or similar systems nicely. But until it is making proven power, it is unlikely they'll be able to take it past the PowerPoint stage.

[Ivy Matt]

The double connection to Houston (U. Houston and NASA JSC) in alexjrgreen's link, combined with JSC being the contracting office for Solicitation Number NNJ12440017Q, probably clinches this as part of the Tarditi/Miley/Scott effort.

And then there's this (previously posted by paperburn1 in another thread), Solicitation Number NNJ12440032Q, which specifically mentions "N Plasma Laboratory (NPL) Associates", which is undoubtedly the same as Miley's Nuclear Plasma Laboratories. In addition to Miley's conceptual work with Tarditi, I imagine this device constructed by Miley's graduate students is relevant to the JSC contracts.

[DeltaV]

I hope the "Not Invented Here" flu doesn't surface.

NASA and Navy should both be at least thinking (PowerPointing) about all promising fusion approaches, including Polywell, FRC, DPF and improved IEC variants. One or two of these are going to stand out from the crowd within a few years.

PowerPoint is cheap. We understand about the lack of hardware funding, but don't have to like it (penny-wise, pound-foolish).

[93143]

Now that might work.

Isp = 10,000 seconds gives Ve= 98100 m/s so let the SSTO produce 6 MN of thrust gives a mass flow, mdot = 61.16 kg/s, with engines burning for 600 seconds to reach orbit at 9.2 km/s. I calculate MR = 1.09832 and reaction mass (fuel) expended is about 36.7 tonnes.

So given an SSTO massing 373 tonnes at launch and 340 tonnes at LEO those numbers might work.

0.5 * 6 MN * 98100 m/s = 294.3 GW

[Aero]

Now that might work.

Isp = 10,000 seconds gives Ve= 98100 m/s so let the SSTO produce 6 MN of thrust gives a mass flow, mdot = 61.16 kg/s, with engines burning for 600 seconds to reach orbit at 9.2 km/s. I calculate MR = 1.09832 and reaction mass (fuel) expended is about 36.7 tonnes.

So given an SSTO massing 373 tonnes at launch and 340 tonnes at LEO those numbers might work.

0.5 * 6 MN * 98100 m/s = 294.3 GW

Oh yea. Energy = 1/2 F * Ve = 1/2 mdot * Ve^2 . I guess with that much energy available, a lot of things might work.

But really, it is only needed for 10 minutes so its only 49 GWhr which is only a little over 42 kilotons of explosive energy and that's easy. Just need to extract the energy a little more slowly and we're home free.

Say, at one time that was called Orion, wasn't it?

[DeltaV]

I'll hold out for Isp on the order of 10^3. That should bring the energy requirement down.

[GIThruster]

IIRC, there are no materials that can confine an exhaust plume above about 5,000 Isp. If you want to go higher, you need to confine it magnetically.

In any event, IIUC, fusion systems have a lower power density than fission systems, despite the reaction itself is higher power, and both have a lower power density than chemical, so they're never going to make good launch systems. They're really much better for interplanetary missions and Isp's like 20,000. In any event, I doubt fusion's low system power density will ever make it a better option than TRITON and given the interplanetary nature of the mission, objections to fission fall away pretty fast.

Fusion is not what we need for a better launch system. It's what we need for cheap, clean power here on Earth.

[93143]

In any event, I doubt fusion's low system power density will ever make it a better option than TRITON and given the interplanetary nature of the mission, objections to fission fall away pretty fast.

Fusion has a lower reactor power density than fission, not a lower system power density. Power conversion equipment and radiators need to be considered as well.

Assuming direct conversion can be made to work without unforeseen complications driving up the system mass, a large aneutronic Polywell at ~75% efficiency (with high-temperature coolant) should compare quite favourably with a fission reactor plus thermal plant at ~25% efficiency (drop the cold-side temperature too far and the radiators destroy the mass budget).

Besides, an aneutronic fusion plant has a number of operational and practical advantages over a fission plant, such as fuel and waste handling, reactor control, lack of structural activation, the lack of a large thermal power conversion system to worry about... Fission would certainly make sense for interplanetary if it were the best available, but Polywell with aneutronic fuel could easily render it obsolete.

Also, TRITON only provides kW-range power in cruise mode. Polywell could provide real juice for a high-Isp interplanetary engine; an NTR core is probably suboptimal for high-power fission-electric.

...

Grooved-ring NTR with variable LOX injection could make a spiffy SSTO engine, although ground launch of an NTR (especially manned) has a number of associated issues that something like Skylon doesn't need to deal with. I've kicked around ideas for Polywell-powered SSTOs; they seem to need to airbreathe for a lot of the ascent unless you make extremely optimistic mass assumptions...