Colliding Beam Fusion Electric Power System for Mars Exploration

Concepts and Approaches for Mars Exploration 6130.pdf

Colliding Beam Fusion Electric Power System for Mars Exploration. Joseph A. O’Toole1, Frank J. Wessel2, N. Rostoker2, and M. Binderbauer2, 1Los Alamos National Laboratory, 1663 Bikini Atoll Road, MS H805, Los Ala- mos, 87545, 2University of California, Department of Physics and Astronomy, Irvine, CA 92697-4575.

Introduction: Exploration of Mars, by robotic means We have evaluated the confinement physics in a and eventually manned exploration, will require significant CBFR based on the Vlasov-Maxwell equation, in- levels of reliable, high-density electric power. An electric cluding a Fokker Planck collision operator and all power system based on fusion energy possesses distinct sources and sinks for energy and particle flow. The advantages. If developed successfully fusion energy sources results indicate that the CBFR could be scalable in the would be characterized by high fuel energy density, low output power range of 106-109. Most, if not all of the system mass, modest fuel requirements, and the abundance critical technologies needed to demonstrate the CBFR of fuel sources throughout the solar system. NASA plans a readily exist: superconducting magnets, vacuum sys- FY01 new program start with a goal of realizing a fully tems, beam injectors, etc. Moreover, low energy, operational fusion space propulsion system within 20 years; pulsed FRCs have already attained parameters close to a similar time frame as envisioned for the MARS Explora- the range needed for fusion energy. A 50 MW electric tion Initiative. The development milestones for a planetary- power system might involve the following (approxi- based power system and space propulsion system are syner- mate) design parameters: 1-meter diameter, 7-meters gistic extensions of our existing efforts to develop an Earth- length, magnetic field ~ 7 Tesla, ion beam current ~ based energy source. This paper reviews the scientific and 10 A, and fuels of either D-He3, P-B11, P-Li6, D-Li6, technology base for our design and describes options for the etc. use of this technology on a Mars mission. A description of the electric power system and its function will be discussed, along with a development Near term power for planetary exploration: We be- time-scale, followed by some options for its use in gin by considering the Colliding Beam Fusion Reactor Mars explorartion. (CBFR). [1], [2], [3] In a CBFR the plasma core is The R&D milestones for our Earth energy research confined inside a “high beta” (β ≡ plasma pressure / program are to complete phase 0 - scientific feasibil- magnetic pressure) magnetic cavity that extends along ity, phase 1 – engineering feasibility, and phase 2 – the axis of the cylindrically symmetric system. Such a commercial feasibility within a three to six-year pe- compact, high-beta system is characterized by a rever- riod. Appropriate modifications to this schedule would sal in the direction of the applied magnetic field, on- be possible to reflect efforts related to space propulsion axis, and the absence of appreciable magnetic field /planetary power system testing. within the fusion core plasma; it is generally referred to as “field-reversed configuration” (FRC). [4] The References: [1]N. Rostoker, M. W. Binderbauer, plasma in an FRC sustains a large circulating current, H. J. Monkhorst, Science 278, p. 1419(1997). [2]N. hence generating a self-magnetic field that adds to the Rostoker, F. J. Wessel, H. U. Rahman, etc. Al. [3] ∼ ambient field. Injected ion beams (Eion 1 MeV) http://fusion.ps.uci.edu. [4] M. Tuszewski, Nuclear maintain the current and replenish the spent fuel. In Fusion 28, p. 2033(1988). the confined-ion frame-of-reference the particle distri- butions are thermal and the circulating current is un- neutralized. The ions orbit size is comparable to the dimensions of the system, hence classical transport of the particles and energy are predicted, reducing the size and mass of the system by many orders of mag- nitude compared to other fusion concepts. Finally, beam injection enables the use of aneutronic fusion fuels. The reaction product of such fuels are predomi- nantly charged particles that can be collimated effi- ciently along the axis of the open-ended system, and converted directly to electric energy. The system scales well to low power, and with heavy nuclear shielding not being required, results in a compact, light weight system suitable for deployment.