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>> Obviously anything less than break-even is not worth having > No. Not at all. Yes -- if the fusion reactor didn't achieve break-even, the designers would b

by lutusp 14y ago

>> Obviously anything less than break-even is not worth having > No. Not at all. Yes -- if the fusion reactor didn't achieve break-even, the designers would be better off using an ion thruster. Also, the NASA documents that describe the project assume that break-even must be achieved: http://www.nasa.gov/directorates/spacetech/niac/2012_phaseII_fellows_slough.html http://www.nasa.gov/directorates/spacetech/niac/2012_phaseII... Quote: "an in-depth analysis of the rocket design and spacecraft integration as well as mission architectures enabled by the FDR need to be performed. Fulfilling these three elements form the major tasks to be completed in the proposed Phase II study. A subscale, laboratory liner compression test facility will be assembled with sufficient liner kinetic energy (~ 0.5 MJ) to reach fusion breakeven conditions." They are talking about doing away with the present lines of fusion research, which haven't achieved break-even, and using a different method. But they don't suggest that this, or some variation, might be used for conventional power generation. > Although it would be desirable, it's not required to make it a net-positive reaction Yes, it is -- that is required. Were this not true, the designers would be better off using an ion thruster, which already exists and is quite efficient. > As the article mentioned, you can power this rocket with an ISS worth of solar panels ... Yes, that's in the description, but the power available (200KW near earth, 100KW near Mars) is not enough to propel the relatively heavy craft to the mission profile (i.e. 30 days to Mars) without some other source of energy, like from a net fusion power gain > 1.

schiffern 14y ago
A rocket only needs to achieve thermal break-even. A power plant needs to achieve electrical break-even, which includes the unavoidable loss from converting the heat to electricity in a heat engine. In this way a system can be simultaneously useful for space travel but useless for power generation.
- lutusp 14y ago
  > A rocket only needs to achieve thermal break-even. A power plant needs to achieve electrical break-even ... Yes, all true. But if a fusion reactor ever achieved break-even, that would be such a breakthrough that the specifics would be reduced to footnotes, and both thermal and electrical applications would soon follow. > In this way a system can be simultaneously useful for space travel but useless for power generation. My point is that if break-even were to be achieved, it would be break-even for both applications. The reason is that the plasma conditions for fusion break-even would have much more in common in the two cases than the differences.

by lutusp 14y ago

schiffern 14y ago

A rocket only needs to achieve thermal break-even. A power plant needs to achieve electrical break-even, which includes the unavoidable loss from converting the heat to electricity in a heat engine. In this way a system can be simultaneously useful for space travel but useless for power generation.

lutusp 14y ago
> A rocket only needs to achieve thermal break-even. A power plant needs to achieve electrical break-even ... Yes, all true. But if a fusion reactor ever achieved break-even, that would be such a breakthrough that the specifics would be reduced to footnotes, and both thermal and electrical applications would soon follow. > In this way a system can be simultaneously useful for space travel but useless for power generation. My point is that if break-even were to be achieved, it would be break-even for both applications. The reason is that the plasma conditions for fusion break-even would have much more in common in the two cases than the differences.