Antiproton Driven Bi-Modal Fusion Propulsion System

The Gasdynamic Mirror (GDM) fusion reactor is investigated for utilization as a propulsion device, as well as for use as a surface power system when driven by antiprotons in both instances. The deuterium-tritium fusion reactions in the device will be initiated by the heating provided by the fission fragments and the annihilation products resulting from the “at rest” annihilation of antiprotons in U target nuclei. The energetic pions and muons of the proton-antiproton (or neutron) annihilations in the U nucleus can heat a DT plasma to several keV during their lifetime. The remaining heating to about 10 keV is provided by the fission fragments. Fissioning of U by “at rest” annihilation of antiprotons has been shown to be nearly 100% efficient, and the process can thus be effectively used in heating a suitable plasma to thermonuclear temperatures. With GDM as a steady state fusion reactor, and assuming certain efficiencies for the various components of the system, we calculate the energy multiplication factor “Q” needed to sustain the steady state operation either in the “propulsive” mode or in the power-producing mode. With the aid of a system and mission analyses, we find that approximately 3.5 micrograms of antiprotons are required to accomplish a round trip mission to Mars in about 59 days. A similar amount is required to initiate and sustain the power-producing mode where gigawatts of electric power may be generated. Although roughly nanograms of antiprotons are currently produced annually, it is expected that hundreds of milligrams or even several grams will be produced annually in the next decade or so when Mars missions may be contemplated.