22'033 Mission to Mars Design Presentation

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Survey of Space Nuclear Power Options
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Dr. Andrew Kadak And Peter Yarsky MIT 12.11.03
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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

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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)

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UHPDC Core Layout
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Outline

• Power Conversion
• Thermophotovoltaics (st)
• Thermionics (st)
• Brayton Cycle (dy)
• Rankine Cycle (dy)

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Thermophotovoltaics (TPV)

• LM transfers the heat from the core to the
  internal radiator
• All power is radiated towards TPV collector
• TPV collectors generate DC from thermal radiation
• Unconverted heat is dissipated via the external
  radiator

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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.

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Thermionic Converters (TIC)

• TIC Benefits
• Single or Dual Layered Concepts
• Static and Direct
• 12-15 efficiency for TH 1200 K
• 25 or higher efficiency for TH 2200 K
• Temperature of heat rejection is 750 K
• TIC Challenges
• Direct Contact with the Fuel

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Conceptual Unit Cell
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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

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Argon Brayton Cycle
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Comparisons
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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)

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Results for 1200 K
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Comparisons
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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)

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BONUS SLIDES

• Slides in case we need clarification

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Single Layer Concept

• LM flows through UHPDC
• LM heats the emitter
• Electrons flow towards collector
• Collector is in direct contact with external
  radiator

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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