Specific impulse Isp, s

1.129 x 105

4.183 x 105

Figure 8.21. Mass budgets for two MCF propulsion systems (adapted from [Kammash, 1995]).

Figure 8.21. Mass budgets for two MCF propulsion systems (adapted from [Kammash, 1995]).

higher than in experimental fusion reactors (see Appendix B). ICF propulsion systems have received less attention, so that similar detailed analyses have not yet been performed; the example in Figure 8.22 is far less informative. The conclusion is that such estimates need to be taken with many grains of salt; see also [AIAA, 2004]. For instance, the mass budget in Figure 8.21 is inconsistent; the total length of the mirror engine (of order 50 m) is reasonable if the plasma number density is indeed as high as 1022cmin fact, in the most advanced tokamak being designed (the ITER fusion reactor) plasma density is an order of magnitude lower because of instabilities. Since the mirror engine length scales linearly with density, using a more reasonable value such as 1021 cm~3 predicts a length of order 500 m. Notice also that the D-3 He engine has Q = 1, meaning a neutral energy budget (power obtained equal to auxiliary power to create plasma), leaving no net power generation. The neutron flux (of order 600MW/m2) is more than 10 times that ever obtained in any tokamak reactor, therefore it sounds wildly optimistic, besides posing enormous structural problems due to radiation damage. Even with the prospective of future

Driver: Mass, metric ton


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