1. Survey of Space Nuclear Power Options

2. Dr. Andrew Kadak And Peter Yarsky MIT 12.11.03

3. Dec 10 th and 11 th, 2003MIT 22.033 / 22.902, Mission to Mars Introduction The goal of current work at MIT is to identify potential Power Conversion Options with use of an Ultra High Power Density Core (UHPDC) that will be scalable to achieve requirements for a plethora of exploration missions, eventually meeting the needs for a manned mission to Mars

4. Dec 10 th and 11 th, 2003MIT 22.033 / 22.902, Mission to Mars The MIT - UHPDC Ultra High Power Density Core –Fast spectrum –Tightly coupled / leakage controlled –Reactor Grade Plutonium (PuC) ~60% Pu239 / ~20% Pu240 –Honey Comb Fuel Nb cladding –20 cm x 20 cm x 20 cm –10 – 11 MWth (liquid metal)

5. UHPDC Core Layout

6. Dec 10 th and 11 th, 2003MIT 22.033 / 22.902, Mission to Mars Outline Power Conversion –Thermophotovoltaics (st) –Thermionics (st) –Brayton Cycle (dy) –Rankine Cycle (dy)

7. Dec 10 th and 11 th, 2003MIT 22.033 / 22.902, Mission to Mars Thermophotovoltaics (TPV) 1.LM transfers the heat from the core to the internal radiator 2.All power is radiated towards TPV collector 3.TPV collectors generate DC from thermal radiation 4.Unconverted heat is dissipated via the external radiator

8. Dec 10 th and 11 th, 2003MIT 22.033 / 22.902, Mission to Mars TPV Challenges TPV efficiency decreases with higher cell temperature The temperature of external radiator is the coldest the TPV cells can be (900 K) It is unlikely that TPV Power Conversion will be scalable.

9. Dec 10 th and 11 th, 2003MIT 22.033 / 22.902, Mission to Mars Thermionic Converters (TIC) TIC Benefits –Single or Dual Layered Concepts –Static and Direct –12-15% efficiency for T H ~1200 K –25% or higher efficiency for T H ~2200 K –Temperature of heat rejection is ~ 750 K TIC Challenges –Direct Contact with the Fuel

10. Dec 10 th and 11 th, 2003MIT 22.033 / 22.902, Mission to Mars Conceptual Unit Cell

11. Dec 10 th and 11 th, 2003MIT 22.033 / 22.902, Mission to Mars TIC Comparison Low Temperature Single –1200 K emitter / 750 K collector –12% efficiency / 400 kWe High Temperature Dual –2200 K emitter / 750 K collector –25% efficiency / 900 kWe High Temperature Single –2200 K emitter / 1200 K collector –12% efficiency / 2500 kWe

12. Dec 10 th and 11 th, 2003MIT 22.033 / 22.902, Mission to Mars Argon Brayton Cycle

13. Dec 10 th and 11 th, 2003MIT 22.033 / 22.902, Mission to Mars LowMedHigh T1 (low)400 K473 K533 K T2665 K780 K890 K T3 (high)1200 K1400 K1600 K T4830 K970 K1100 K Net Work300 kW560 kW950 kW Efficiency0.200.190.20 Mass Flow Rate5.5 kg/s9.1 kg/s13 kg/s Reactor Power1.5 MW3.0 MW4.9 MW Pressure Ratio3.183.133.18 Comparisons

14. Dec 10 th and 11 th, 2003MIT 22.033 / 22.902, Mission to Mars Sodium Rankine Cycle Sodium because: –2100 R (1167 K) saturation temperature at 15.4 psia (1.05 atm) –Neutronic Inertness –Heat Removal Properties (UHPDC) –Saturation Curves are steep (scalability) –Little Pumping Power Required –Phase Transition (maximal radiator usage)

15. Dec 10 th and 11 th, 2003MIT 22.033 / 22.902, Mission to Mars Results for 1200 K Turbine Efficiency0.950.90.85 Cycle Efficiency11% Turbine Work [MW]1.18 MW1.15 MW1.14 MW Turbine Outlet Pressure [psia] 4.03.73.2

16. Comparisons

17. Dec 10 th and 11 th, 2003MIT 22.033 / 22.902, Mission to Mars Conclusions Dynamic PCU technology is more effective and scalable than Static (Sodium Rankine in particular) Static direct energy conversion is still attractive from a reliability standpoint (TIC in particular)

18. Dec 10 th and 11 th, 2003MIT 22.033 / 22.902, Mission to Mars BONUS SLIDES Slides in case we need clarification

19. Dec 10 th and 11 th, 2003MIT 22.033 / 22.902, Mission to Mars Single Layer Concept 1.LM flows through UHPDC 2.LM heats the emitter 3.Electrons flow towards collector 4.Collector is in direct contact with external radiator

20. Dec 10 th and 11 th, 2003MIT 22.033 / 22.902, Mission to Mars HEU alternative Less Reactive Fuel –Larger Core More Fuel Mass More shielding Required No Fertile-Fissile Species (240Pu) –Larger Reactivity Swing More demand on Control Devices Work Still in Progress on CBA