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Old September 23 2011, 08:29 AM   #49
John O.
Rear Admiral
 
Location: the bush
Re: The DARPA 100 Year Starship

Bump.

This conference is coming up in about a week, just putting the final touches on my presentation. The paper's already been submitted and accepted. When publication rolls around in a few months I'll see if I can upload/attach a copy into this thread.

Incidentally I have better data now for the 'sweet spot' ideal operating condition. I'm not sure how much I kept this thread apprised of how my concept design changed but it advanced into a new variation of potential fusion propulsion. We call it the "Viper Pulsed Fusion Rocket". Viper evolved as an inside joke attempt to meld together "PFR" and "HIIPER" into "PFHIIPER" (Viper). I'm gonna summarize extremely briefly and you guys can read the paper later if you want. We feed a helicon plasma into an IEC, get fusion through some breakthrough technologies (some of which have been invented, 1 or 2 haven't), we get power production (~140 MW), and thrust by magnetically collimating the alpha particles that come out of the reaction, putting them through a direct energy conversions cycle to syphon off enough power to run the system (~24 MW IIRC), and then comes the interesting part. People have theorized about something called "Diluted Fusion Product" propulsion whereby you essentially convert the "nuclear thermal rocket" idea of a fission reactor into a fusion reactor. We take the alpha particles which are extremely energetic, and mix them with a neutral gas like hydrogen, in a magnetically confined chamber, and exhaust the mix. Assuming various efficiencies (many allowing for significant losses), we get pretty good numbers:

Thrust: 660 N
ISP: 30 million

Operating off-optimal you can actually get thrust up to about 3 kN and it only brings your ISP down to.... idk, 1-3 million I think. Pretty awesome.

On a 2-month low thrust transfer to Mars, with about 1000 kg of propellant, the engine could pull about 460 MT of cargo. Beast eh?
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Last edited by John O.; September 23 2011 at 08:48 AM.
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