New Ideas for Space Exploration: Center for Space Nuclear Research (CSNR)

1. New Ideas for Space Exploration:Center for Space Nuclear Research (CSNR) Dr. Steven D. Howe 9/04/09

2. Current NASA Plan: Exploration Systems Architecture Study (ESAS) • Design and build Ares-I- solid rocket 1st stage, Lox/Lh2 second stage – both are new systems • Ares-I takes humans to orbit in the ORION (upgraded Apollo) capsule • Ares V is a heavy lift vehicle – 125 T to LEO • Start Lunar sorties (~10) by 2018 • Establish a lunar Outpost around 2020 • Mars in 2030

3. Lunar Trajectory Objectives • Minimum ΔV trajectory • Time-of-Flight (TOF) is not a significant concern. • Insertion into either equatorial or polar LLO Lunar Orbit Capture (LOC) Low Earth Orbit (LEO) Trans-Lunar Orbit (TLO) Earth Moon Low Lunar Orbit (LLO) Trans Lunar Injection (TLI)

4. CSNR Perspective • Goal of space exploration is understanding our “neighborhood”, i.e. the solar system • Unmanned scientific missions for science and as a precursor to human missions • Ultimate goal is the expansion of human civilization throughout the solar system

5. CSNR Perspective Current propulsion technologies are insufficient for human expansion past the Moon we need the “steamship” equivalent to the sailing ships of the past what is the next propulsion technology - fission, fusion, electric propulsion, sails, beams? According to the Independent Review Panel convened in 1999 to review the propulsion technologies examined in the NASA Advanced Space Transportation Program: “The Review Team categorized fission as the only technology of those presented [45 concepts were presented] which is applicable to human exploration of the near planets in the near to mid-term time frame…” The CSNR proposes that the Nuclear Thermal Rocket (NTR) is the only near term option for improved transportation of humans to other planets

6. Benefits of the NTR have been shown for several missions • Moon - Reduce costs of implementing a Lunar Outpost • Mars - Faster missions for humans; reduced radiation exposure; lower costs for cargo; adaptability to hazards • Good Asteroid - rendezvous • Bad Asteroid/comet - rapid interception • Outer solar system – time to “first science” within a decade for orbitor missions to outer planets and to Kuiper Belt fly-through In short, the NTR opens up access to the entire solar system for humans and robotic probes

7. Nuclear Technologies in Space • Radioisotope Thermoelectric Generators (RTG) • Fission Surface Power (FSP) • Nuclear Thermal Rockets (NTR)

8. The CSNR is pursing a Common Technology for reactor fuels and radioisotope sources The distribution and encapsulation of radioisotope materials and nuclear fuels in an inert carrier matrix will address several issues and requirements for space power applications: Potential to address non-proliferation security requirements. The ability to survive re-entry into Earth’s atmosphere and impact under accident conditions. Assembly & handling safety Reduction in material self interaction such as -n reactions. Self-shielding properties. The SPS acquired with a INL LDRD grant enables fabrication of tungsten parts at nearly full theoretical density

9. Status of Radioisotope Power In 2007, DOE will purchase the last 10 kg of Pu-238 from Russia (ref- Robert Lange, DOE/NE,ANS Space Nuclear Conference, June, 2007) Total of 24 kg will be in the US inventory Four Flagship missions are currently in pre-design which may consume most, if not all, of the PU-238 available to NASA NASA recently called for proposals for Discovery class missions that would use Advanced Stirling Radioisotope Generators (ASRGs) Without a restart of Pu-238 production in the US, no missions will go beyond Mars after ~2017 However, over 1800 other radioisotopes exist that might be applicable to exploration missions

10. CSNR examination of radioisotope power and propulsion • Radioisotopes can have 100,000 times the energy density as current batteries • Examined the use of alternative isotopes • Shorter half lives • Higher power density • Examined new encapsulation techniques

11. 1.2 Isotope Preliminary Selection:

12. Radio-Isotope Heated Jet Engines for Titan Flight Applications • Utilize radioisotope heat sources to power Unmanned Aerial Vehicles • NASA: • ENABLES detailed, high resolution mapping of the surface of planets and moons with non-oxygen atmospheres • DOD/ DHS application and interest: • May enable detailed mapping of the Earth’s ocean bottom • May allow long duration observation of borders or hostile territory Image courtesy of http://saturn.jpl.nasa.gov/news/events/titana/index.cfm

13. Operation Basics • Replace combustion chamber in jet engines with a radioisotope driven heat exchanger • Operates for months to years based on isotope selection • Somewhat throttled • Utilizes ~95% of heat generated • Stable, robust, long-lived Image courtesy of http://saturn.jpl.nasa.gov/news/events/titana/index.cfm

14. Titan Flight Conditions • 200 kg craft • P=1.6 bar; ρ=5.7kg/m3 • Flight Velocity of 20 to 50 mph • Lift to drag ratio of 12 • CL of 0.63 • Required thrust of 8 lbf • Wing planform area of ~10 ft2 Image courtesy of http://saturn.jpl.nasa.gov/news/events/titana/index.cfm

15. Unmanned Underwater Vehicle for US Port Security • Concept of Operations • Scan ships of interest to determine the existence of special nuclear material • Acquire, track, follow, and report the location of ships of interest • Operate without being detected • Outfitted with SNM detection equipment • Close proximity maneuvering near ships • 15-20 knots operation speed • 5-Year mission durations

16. NASA’s FSP program seeks to design and build an “affordable reactor” UO2 fuel, stainless steel clad, NaK coolant Most of the mass is in the radiators Shield mass depends on distance and burial option Estimated cost is $1.8B Fission Surface Power (FSP)

17. CSNR alternative:Mobile Nuclear Powered Base

18. Project Description • NASA’s current plan is the US Space Exploration Policy (was Vision for Space Exploration) • Return humans to the Moon and then to Mars • The current plan allows for 5-10 Sorties: • Placing a few humans on the lunar surface for 2 weeks at different locations • Then placing a lunar outpost somewhere that houses 6 humans for 6 weeks

19. Project Description, cont. • Included is a rover that will allow astronauts to travel 300 km in 3 days • Estimated power ~2kWe • Unshielded against lethal solar flares • Adding shielding against solar flares adds ~2 tons • Required power ~10-20kWe • A completely mobile base would: • Reduce number of costly sorties • Allow long stay times • Provide shielding from lethal solar flares

20. Mobility Options – “Wagon” • Habitation Modules • Radiator/Storage Carts • Reactor Cart Reactor at Full Power In Transit

21. 360° Radial Shields

22. Smart Shields

23. CSNR Alternative:Optically Coupled Lunar Reactor • Utilize the tungsten based technology • Free standing uranium loaded tungsten core • Hard vacuum in a totally reflective cylinder • Reflect all light to PV array at base • Advantages • Power conversion unit can be repaired • Beam power to factory • Use process heat • Light weight option allows “landed reactor”

24. Mass Comparison • Mass comparison between Optical System and the FSP. • Is it feasible? • Yes, under these conditions: • Thermophotovoltaic Cells efficiency is increased. • The reflector design can be advanced so more than 50% of the radiation exit after one reflection.

25. Nuclear Thermal Rockets (NTR) offer 2x the performance of the Shuttle engines

26. Recent developments in NASA for Nuclear Thermal Propulsion (NTP) NASA’s Mars Architecture Study (Dec 2007) concluded that the NTR was required for human missions to Mars National Research Council committee (S. Howe served as one of 23 members) that reviewed the NASA Exploration Technology Development Program (ETDP) just reported (8/21/08) that the one technical gap in program was no funding for the NTR.

27. Issues • Ensuring no emission of Radioactive exhaust • Ensuring difficulty of extracting fuel • Ground testing • Operations in space- restart • Reliability – space cold • Cost Tungsten based fuel may solve 1, 2 and 3 Supplying the Lunar Base would address 4, 5 and 6

28. NTR-Based ESAS Architecture EDS NTR

29. Tungsten Cermet Fuels • Hot hydrogen compatibility • Better thermal conductivity • Potential for long life reactors • High melting point (~3700 K) • Resistance to creep at high temperatures • Smaller reactor core then carbide fuels • Good radiation migration properties • Contains fission products and uranium oxide in fuel • More radiation resistant than carbon

30. NTR-Based ESAS Architecture

31. Near Earth Objects (NEO) 08/03/2009 31

32. Problem Statement • Long-period comet, traveling towards Earth with nearly linear trajectory across solar system • Approximation of worst-case scenario • Diameter ~10 km, mass ~3e+14 kg as initial definition • Comet initially observed at ~5 AU (1 AU = 1.49e+8 km) around Jupiter orbit traveling ~18 km/s and gradually accelerating as approaching earth • Parabolic trajectory • Approximate impact time is ~ 297 days ~ 10 months 08/03/2009 32

33. Our Approach • Multiple NTRs (Nuclear Thermal Rocket) launched from LEO • Rockets carry thermonuclear devices (~9 Mt) • Mission design: • Determine NTR trajectory (independent of scale) • Estimate terminal interception yield needed per mass of comet • Conclude feasible problem scale based on constraints (current launch capacity, available warhead yield, etc.) 08/03/2009 33

35. Trajectory 08/03/2009 35

36. Chemical Rocket Mass to LEO vs. Time of Intercept 08/03/2009

37. CSNR Summer Fellowships program has proven the ability to attract top students 4 years running Nationwide search Accept applications for 2 months Unique research projects each year Goals Provide Student Fellows an in-depth understanding of nuclear reactor and radioisotope power and heating technologies applied to space exploration Gain experience using complex computer codes that will be applicable to modeling nuclear systems Speaking and writing experience (weekly presentations by students) Exposure to INL and Idaho Falls Produce sufficient information for production of unsolicited proposals to federal agencies Provide pool to fill “Next Degree” opportunities Identify good fits to INL and not-so-good fits

38. 2009 CSNR Summer Fellowships Funded by a combination of NASA - $100K CAES program development - $25K INL NGNP program – $25K 105 applications – due to USRA broadcast to members Accepted 14 Fellows represent 10 states and 12 universities 4 PhD candidates, 9 MS, 1 undergraduate, 1 DoE intern Disciplines 5 Nuclear eng., 4 mechanical eng., 2 physics, 1 aerospace eng., 1 chemical eng., and 1 computer science Working on “challenging” topics attracts the students Mobile lunar base, nuclear rockets, decoupled fast reactors, isotope powered UAVs and UUVs, “smart” shields, comet interceptors, Mars Hopper

39. Next Degree (NxD) Program Objectives Build technical workforce in the CSNR and provide a feedstream into INL Difficult to develop projects in CSNR without feasibility studies Hard to do feasibility studies using INL staff without funding Shortage of NE graduates- getting worse Students are tempted to leave early for a paycheck Desire is to attract top quality students from around the country to INL/CSNR by engaging them in space exploration projects Many students do not automatically see INL and Idaho as a premier research location NxD students work ½ time at industry competitive salary on CSNR or INL project and ½ time on their next degree Able to retain school affiliation or enroll in Idaho Universities Number of NxD students increased to 7 in FY09 3 PhD and 4 MS

40. Further contact Center for Space Nuclear Research www.csnr.usra.edu Universities Space Research Association (USRA) www.usra.edu Idaho National Laboratory www.inl.gov Dr. Steven D. Howe showe@csnr.usra.edu