NASA/TP--2001-211274 Prospects For Nuclear Electric Propulsion Using Closed-Cycle Magnetohydrodynamic Energy Conversion R.J. Litchford, L.J. Bitteker, and J.E. Jones Marshall Space Flight Center, Marshall Space Flight Center, Alabama October 2001 The NASA STI Program Office...in Profile Since its founding, NASA has been dedicated to CONFERENCE PUBLICATION. Collected the advancement of aeronautics and space papers from scientific and technical conferences, science. The NASA Scientific and Technical symposia, seminars, or other meetings sponsored Information (STI) Program Office plays a key or cosponsored by NASA. part in helping NASA maintain this important role. SPECIAL PUBLICATION. Scientific, technical, or historical information from NASA programs, The NASA STI Program Office is operated by projects, and mission, often concerned with Langley Research Center, the lead center for subjects having substantial public interest. NASA's scientific and technical information. 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Hanover, MD 21076 1320 (301)621q)390 NASA/TP--2001-211274 Prospects For Nuclear Electric Propulsion Using Closed-Cycle Magnetohydrodynamic Energy Conversion R.J. Litchford, L.J. Bitteker, and J.E. Jones Marshall Space Flight Center, Marshall Space Flight Center, Alabama National Aeronautics and Space Administration Marshall Space Flight Center • MSFC, Alabama 35812 October 2001 Acknowledgments This work was sponsored by the Advanced Propulsion Research Project Office, Advanced Space Transportation Program, George C. Marshall Space Flight Center (MSFC), National Aeronautics and Space Administration. The authors acknowledge and thank Tara Poston (MSFC/TD30) for her expert assistance with the trajectory analyses. The first author expresses special thanks to John W. Cole for many illuminating discussions pertaining to specific energy requirements for deep space missions. The NASA Principal Investigator was Ron J. Litchford, TD15/ASTR TRADEMARKS Trade names and trademarks are used in this report for identification only. This usage does not constitute an official endorsement, either expressed or implied, by the National Aeronautics and Space Administration. Available from: NASA Center for AeroSpace Information National Technical Information Service 7121 Standard Drive 5285 Port Royal Road Hanover, MD 21076 1320 Springfield, VA 22161 (301) 621 0390 (703) 487 4650 ii TABLE OF CONTENTS 1. INTRODUCTION ...................................................................................................................... 2. SYSTEM ANALYSIS ................................................................................................................ 4 2.1 Thermodynamic Cycle Analysis ..................................................................................... 7 2.2 Specific Mass Analysis ................................................................................................... 11 2.2.1 Fission Reactor .................................................................................................... 12 2.2.2 Magnetohydrodynamic Generator ....................................................................... 12 2.2.3 Magnet Confinement Structure ........................................................................... 13 2.2.4 Saddle Coil Winding--Linear Generator ............................................................ 14 2.2.5 Helmholtz Coil Winding--Disk Generator ......................................................... 15 2.2.6 Turbocompressors ................................................................................................ 17 2.2.7 Regenerator .......................................................................................................... 17 2.2.8 Radiator ............................................................................................................... 18 2.2.9 Electric Thruster .................................................................................................. 19 3. SYSTEM ASSESSMENT .......................................................................................................... 20 4. MAGNETOHYDRODYNAMIC TECHNOLOGY ISSUES ..................................................... 24 4.1 Conceptual Design of the Nonequilibrium Disk Generator ........................................... 24 4.2 Neutron-Induced Ionization Enhancement ..................................................................... 27 5. MISSION CAPABILITY ASSESSMENT ................................................................................. 30 6. CONCLUSIONS ........................................................................................................................ 34 REFERENCES ................................................................................................................................. 35 iii LIST OF FIGURES . Schematics of (a) linear and (b) disk MHD generator configurations ....................................... 2 2. Essential components of a nuclear electrical propelled spacecraft based on a closed-loop MHD Brayton cycle powerplant .......................................................... 5 . Schematic of a closed-loop nuclear MHD Brayton cycle powerplant with regenerative heating and intercooled multistage compression. Installation is shown coupled to high-power electric propulsion .............................................. 6 . Temperature-entropy diagram for a closed-loop Brayton cycle powerplant with regenerative heating and intercooled multistage compression .......................................... 7 . Illustration of a circular crescent coil cross section for a linear channel of diameter D. Note that 2a = D + c is a geometric constraint .......................................................................... 14 . Illustration of a Helmholtz coil winding for a disk generator of diameter D. Note that the coils are separated by a distance r = D/2 ............................................................. 16 . Thermal efficiency of an MHD generator Brayton cycle using helium as the working fluid ................................................................................................................... 20 . Specific mass characteristics of a disk MHD Brayton cycle powerplant using helium as the working fluid ............................................................................................. 21 . Disk MHD powerplant specific mass attributes for/_N = 40% and l_s,g = 70%. The working fluid is helium ...................................................................................................... 22 10. Scaling of MHD powerplant and propulsion system specific mass with net electrical power ............................................................................................................ 23 Variation in design parameter F with M and T e ......................................................................... 25 Design lofting for a 100-MWth MHD disk generator using cesium-seeded helium working fluid ................................................................................................................. 26 13. Computed electrical conductivity versus relative density for pure 3He. Solid lines correspond to a gas temperature of 1,500 K ..................................................................... 28 V LIST OF FIGURES (Continued) 14. IMLEO as a function of specific impulse for a 40-MW e nuclear MHD space power installation delivering a 100-t payload to Mars .................................................... 31 15. Optimal trajectories for 120- and 180-day transits. Assumes 100-t payload and 40-MW