10/14/03 NIAC 7600-039 FINAL REPORT 1 Phase II Final Report NASA Institute for Advanced Concepts A Realistic Interstellar Explorer a. INSTITUTION: The Johns Hopkins University Applied Physics Laboratory 11100 Johns Hopkins Road, Laurel, MD 20723-6099 b. TITLE OF INVESTIGATION: A Realistic Interstellar Explorer c1. PRINCIPAL INVESTIGATOR: Dr. Ralph L. McNutt, Jr. Voice: 443-778-5435 Fax: 443-778-8950 [email protected] c2. BUSINESS POINT OF CONTACT: Mr. E. Dale Wilder, Jr. Voice: 443-778-6505 Fax: 443-778-5892 [email protected] d. REPORTING MONTH: June 2002 - FINAL e. IDENTIFICATION: NIAC CP 99-02 GRANT NUMBER 07600-039 PHASE II ADVANCED AERONAUTICAL/SPACE CONCEPT STUDIES f. DATE OF SUBMISSION: 14 October 2003 10/14/03 NIAC 7600-039 FINAL REPORT 2 Table of Contents A Realistic Interstellar Explorer ......................................................................................... 1 Table of Contents................................................................................................................ 2 1.0 Introduction and Programmatics................................................................................... 5 2.0 The Proposed Work ...................................................................................................... 8 2.1 Advanced Concept Description. ............................................................................... 8 2.2 Advanced Concept Development Plan ..................................................................... 9 2.2.1 Equivalent Mission Performance Requirements.............................................. 10 2.2.2 Nuclear Pulse Propulsion................................................................................. 10 2.2.3 Solar Thermal Propulsion ................................................................................ 10 2.2.4 Cyrostats for STP with LH2 ............................................................................ 11 2.2.5 Low-Thrust Propulsion Concepts .................................................................... 11 2.3 Spacecraft Systems ................................................................................................. 11 2.3.1 “Table-top Spacecraft.”.................................................................................... 11 2.3.2 Architecture Issues........................................................................................... 11 2.3.3 Phase II Tasks .................................................................................................. 12 2.3.4 Thermal and Mechanical System..................................................................... 12 2.3.5 Communications System ................................................................................. 12 2.3.6 Propulsion ........................................................................................................ 13 2.3.7 Power System................................................................................................... 13 2.3.8 Software and Autonomy. ................................................................................. 13 2.4 References and Bibliography from Phase II Proposal ............................................ 13 3.0 Interim Report Contents.............................................................................................. 15 4.0 Mission Design ........................................................................................................... 16 5.0 Guidance and Communication.................................................................................... 19 5.1 Star-Tracker Technology ........................................................................................ 19 5.2 Integrated guidance and communications system................................................... 19 6.0 Power .......................................................................................................................... 20 6.1 Am 241 as a Heat Source – Followup .................................................................... 21 6.2 Communications with DOE.................................................................................... 24 6.3 Notes on Nuclear Materials for Space Use............................................................. 25 6.3.1 Pu-238 Supply.................................................................................................. 25 6.3.2 In-space Nuclear Reactors ............................................................................... 28 6.3.3 Summary.......................................................................................................... 32 6.4 GPHS Issues............................................................................................................ 33 6.5 Am-241 RTG .......................................................................................................... 34 6.6 Stirling Converter Issues......................................................................................... 37 6.7 Radioisotopes for Advanced RTGs and Radioisotope Sail Propulsion.................. 37 7.0 Thermal and Mechanical............................................................................................. 42 7.1 Propulsion System Parametric Study...................................................................... 43 7.1.1 Introduction and Background .......................................................................... 43 7.1.2 Parametric System Trade Study....................................................................... 44 7.1.3 Assumptions..................................................................................................... 44 7.1.4 Results.............................................................................................................. 44 7.1.5 Outstanding Technical Issues .......................................................................... 46 10/14/03 NIAC 7600-039 FINAL REPORT 3 7.1.6 Current Notional Spacecraft ............................................................................ 47 7.2 Master Equipment List............................................................................................ 48 7.3 Spin-stable Probe Configuration............................................................................. 49 7.4 Mass considerations for thermal shield and propellants......................................... 51 7.5 System Evolution.................................................................................................... 53 7.6 Materials Concerns for the Solar Thermal Engine ................................................. 54 7.7 Addendum............................................................................................................... 59 7.7.1 Coating Issues .................................................................................................. 59 7.7.2 Mass Estimates................................................................................................. 60 7.8 Thermal Analysis of New Probe Configuration ..................................................... 63 8.0 Propulsion ................................................................................................................... 65 8.1 Fission Propulsion for Realistic Interstellar Explorer Concept .............................. 65 8.1.1 Background...................................................................................................... 65 8.1.2 Critical Assembly............................................................................................. 66 8.1.3 Kinetic Theory ................................................................................................. 66 8.1.4 Americium-242m and Other Possibilities........................................................ 68 8.1.5 Supply and Production Issues .......................................................................... 70 8.2 Summary of Nuclide Properties.............................................................................. 72 8.3 Cryostat Results ...................................................................................................... 74 8.4 Hot Hydrogen Erosion ............................................................................................ 74 8.5 Propellant Chemistry and Optimization.................................................................. 76 8.5.1 Propellant and Shield Reactions ...................................................................... 76 8.5.2 Nozzle Design – with Ammonia Propellant .................................................... 77 8.5.3 Heat Exchanger Pressure Losses – With Ammonia Propellant....................... 79 8.5.4 Conclusions...................................................................................................... 79 Table 1. Ammonia Propellant Analysis Results ........................................................... 80 Table 2. Hydrogen Propellant Analysis Results ........................................................... 81 Table 3. Methane Propellant Analysis Results ............................................................. 82 Table 4. Diborane Propellant Analysis Results ............................................................ 82 Table 5. Hydrazine Propellant Analysis Results........................................................... 83 8.6 Metal Hydride Storage of Hydrogen....................................................................... 85 8.7 NERVA and High-Temperature Materials ............................................................