Proton-proton fusion has the big advantage of being completely aneutronic.<br/>
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I assume that TL 12+ fusion plants use nuclear dampers to permit the reaction in non-stellar core conditions.<br/>
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Another handwave I use is that the very large power plant fuel volumes in the design sequences are in fact mostly used by the thrusters to add kinetic energy to the ship.<br/>
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When 1 gram of hydrogen is good for a megawatt-week of energy, canonical fuel rates don't make a lot of sense.<br/>
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If the bulk of the fuel is converted directly to kinetic energy, you get close to 30G-days worth of thrust for 1G manoeuvre drive equipped ships (at least in Megatraveller).<br/>
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This assumes an energy to thrust conversion efficiency of 75% and an overall vehicle density of 0.7 to 1 tonne per cubic metre.<br/>
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Now the multi-terawatt heat rejection implied requires another handwave - I invoke a radiator technology that arises from the unified physics that make nuclear dampers, "meson" weapons and "contragravity" possible.<br/>
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In short, waste heat is emitted as a stream of neutrinos. Neutrinic radiators also deal with the heat generated by the power plant, etc.<br/>
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The big advantage of doing this is that the near-c rock problem gets pushed into edge cases with very high mass ratios.<br/>
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The big disadvantage is the added complexity of designing ships with a mass budget.<br/>
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Rob O'Connor <br/>
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