DOW-UAP-D145, AAWSAP DIRD, Aneutronic Fusion Propulsion I, November 2010

PAGE 3

Aneutronic Fusion Propulsion The Defense Intelligence Reference Document provides nonsubstantive but authoritative reference information related to intelli ence to ics or methodolo ies. Prepared by: Technology Warning Division (DW0-4) Defense Warning Office Directorate for Analysis Defense Intelligence Agency AAP Person 83 Administrative Notes: (U) COPYRIGHT WARNING: Further dissemination of the photographs in this publication is not This product is one in a series of advanced technology reports produced in FY 2010 under the Defense Intelligence Agency, Defense Warning Office's Advanced Aerospace Weapon System Applications....--....... (AAWSA) Program. Comments or questions pertaining to this document should be addressed to ( · ---14-A.E..!'erson Person 1 j AAWSA Program Manager, Defense Intelligence Agency, ATTN: JUIAF - DI/DWb-3,i'- •

PAGE 4

Comparison of Specific Impulse for Various Rocket Designs .............................. 5 Subatomic Particle Mass, Velocity, and Energy .................................................. 9 Nuclear Fission Rockets .......................................................................................................................... 10 Chapter 2: Nuclear Fusion Rocket Design ............................................................ 13 Classic Nuclear Fusion Schemes ....................................................................... 13 Fusion Initiation Methods................................................................................. 14 Inertial Confinement Fusion (ICF) ................................................................... 16 Cavitation (Bubble) Fusion............................................................................... 17 Rocket Design Using Fusion Energy ................................................................. 17 Chapter 3: Aneutronic Nuclear Fusion Schemes .................................................. 18 Chapter 5: Aneutronic Fusion Propulsion Projects............................................... 21 Nuclear Pulse Propulsion ................................................................................. 21 Other Aneutronic Rocket Designs..................................................................... 22 Chapter 6: Speculation on Research Needs Over the Next 30 Years ..................... 25 Surface to Low-Earth Orbit (100 miles) .................................................................................................. 26 LEO to Mars (34 to 249 million miles) .............................................................. 27

PAGE 5

LEO to the Moons of Jupiter and Saturn (460 to 940 million miles).................. 28 LEO to Alpha Centauri (4.22 light-years or 24.8 trillion miles) ......................... 28 Appendix B: Aneutronic Fusion Rocket................................................................ 32 Appendix C: Antimatter Annihilation Rocket........................................................ 36 Figure 1. Liquid-Fueled Chemical Rocket. ....................................................... vi Figure 2. Mass Ratio Increases as Objects Approach Speed of Light ................ 2 Figure 3. Spherical Radiation Shield Surrounding Point Source ....................... 8 Figure 4. Nuclear Fission Rocket Design ........................................................ 11 Figure 5. Schematic Design of a Magnetohydrodynamic (MHD) Generator..... 13 Figure 6. Nuclear Fusion of Deuterium and Tritium ....................................... 14 Figure 7. Low-Temperature Fusion Reactions................................................ 15 Figure 9. Aneutronic Fusion Schemes............................................................ 18 Figure 12. Time Dilation at Relativistic Velocities .......................................... 31 Figure 13. Maximum Achievable Velocity Versus Fuel Usage ......................... 33 Figure 14. Acceleration and Rocket "Clock" Ratio Vs Mission Time on Earth .. 33 Figure 15. Spreadsheet for Sample Mission to Alpha Centauri........................34

PAGE 6

Table 1: Specific Impulse for Various Rocket Engine Types ............................. 3 Table 2: Rest Mass of Various Subatomic Particles ........................................ 10 Table 3: Specific Impulse for Selected Drives ................................................ 35

PAGE 7

Aneutronic Fusion Propulsion Space exploration is limited by existing propulsion technology. Up to now, chemical rockets have been used to reach low-Earth orbit, the Moon, and the outer regions of the solar system. Chemical rockets can use either solid or liquid fuel. Regardless of the type of fuel, their design is similar to that shown in Figure 1. Oxygen is combined with hydrogen or a hydrocarbon fuel in a combustion chamber where high temperatures and pressures cause the exhaust to be ejected through a supersonic nozzle to provide thrust to the rocket. The momentum of the fuel ejected through the nozzle provides the force or thrust that accelerates the rocket forward. There are many variations of chemical rockets, but they all suffer from the need to carry copious amounts of fuel. Other methods have been proposed to decrease the need to carry such a significant mass of fuel into space. Ion drives, for example, are used to provide the very low thrust required to maintain satellites in Earth orbit. The "fuel" that they carry is xenon gas accelerated by electric fields. Nuclear fission propulsion has been proposed for space missions, and thermal nuclear fission reactor rockets were constructed and tested at the Nevada Test Site through Project Rover between 1956 and 1971.1 In these rockets, a nuclear reactor provides heat to liquid hydrogen through nuclear fission and ejects the hydrogen gas through a Laval nozzle to generate thrust. While these rockets must still carry hydrogen fuel as a propellant, these rockets can provide more than twice the performance of chemical rockets by using heat through fission rather than reactive chemicals. The results of the 72 reactor tests conducted under Project Rover were very promising and culminated in the successful 12-minute test of the Phoebus-2A NERVA (Nuclear Engine for Rocket Vehicle Application) reactor that generated over 4 gigawatts of thermal power. One problem associated with nuclear fission rockets is radioactive contaminants. These contaminants in the exhaust make this technology impossible to use in launching payloads from Earth. Additionally, for applications in space, radiation protection must be provided for the crew by adding heavy shielding materials or by locating the crew as far as possible from the reactor propulsion system. Nuclear fusion, as opposed to fission, provides another potential propulsion technology. In a fusion propulsion system, isotopes of light elements are fused together under extreme conditions to form heavier elements, releasing large amounts of thermal energy. This thermal energy can be used to heat liquid hydrogen to high temperatures and expand it through a Laval nozzle to provide thrust in a manner similar to that shown in Figure 1. Typically, isotopes of hydrogen and helium would be used in fusion propulsion systems. Deuterium is an isotope of hydrogen and can be separated from the hydrogen in water. Fusion reactions are difficult to initiate due to the high temperatures and pressures required. Thermonuclear bombs, for example, combine a fusion device with a nuclear fission bomb to provide the high temperatures required to initiate the fusion reaction. Regardless of the conditions required to induce nuclear fusion, the energy release is large. From propulsion standpoint, an advantage of fusion over fission is that for a given amount of thrust, the fusion reaction requires less fuel than either fission or chemical propulsion systems. Fusion reactors using deuterium or tritium fuels are easiest to initiate; however, they generate significant amounts of neutron radiation. This is a hazard for the crew on a