What's ahead in space exploration: Potential roles for the INL and the CSNR

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What's ahead in space exploration Potential
roles for the INL and the CSNR

• Steven D. Howe, Ph.D.
• Director
• Center for Space Nuclear Research
• 7/17/07

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We shall not cease from exploration, and the end
of all our exploringwill be to arrive where we
startedand know the place for the first
time -T.S. Eliot
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Tangible Benefits

• Sulfur volcanoes on Io around Jupiter-
• Planetary geology, ionosphere of Jupiter,
  magnetospherics
• Seas of methane and shorelines on Titan around
  Saturn
• Alternative atmosphere meteorology
  xeno-chemistry
• Ancient ocean beds on Mars
• Geology atmospheric decay early life?

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Intangible Benefits

• Finding an ocean on Europa
• Demonstrating US technological capability by
  sending humans to Mars
• Seeing the lights of a Lunar base each night
• Motivating more students to pursue math and
  science

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Radioisotope Thermoelectric Generator (RTG) have
been used since the Apollo days

• Pu-238
• Non-weaponizable
• 87.7 year half-life
• Alpha decay plus gamma rays
• Heavily encapsulated
• Qualified against accident scenarios- fire,
  impact, explosion
• 6-8 conversion efficiency
• No moving parts
• Around 200 kg/kWe
• Continuous power

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INL currently plays a key late-stage role in RTGs
for space missions

• INL is responsible for final assembly and testing
  of Radioisotopic Thermoelectric Generators (RTGs)
• The New Horizons mission to Pluto the
  highest-priority exploration mission of the
  decade depended on INL fabrication

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Radioisotope Power Systems (RPS)

• Current RTGs are simple, robust, and proven
  technology
• Pu-238 running out
• CSNR is currently examining possible alternative
  isotopes and new materials to ensure
  immobilization in accident scenarios
• INL has facilities to fabricate new RPS systems
• Current design study Using RPS sources for
  space power and for long duration (gt2yr) Remotely
  Piloted Vehicles for planetary observation

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Radiation Doses

• What is your average mREM dose?
• 360 mREM/year
• A nuclear power plant worker can receive up to
• 5,000 mREM/year
• What is an astronauts dose?
• 1,000 mREM/week

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Energy Densities of Known Sources
Reaction Specific Energy (MJ/kg)
Chemical 7-10
Fission (100) 71E06
Fusion (100) 750e06
Antimatter 90000e06
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NTR was developed and proven in the Rover/NERVA
programs in the 1960s

• Pewee operated at 2550 K for 40 minutes at 503
  MW
• The engine weighed 5000 lb and would have
  produced a thrust of 15,000lbsf
• Pewee was envisioned as an orbital tug to support
  a Lunar base

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CSNR Summer Fellows Study results-NTR-based ESAS
Architecture
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Systems Nuclear Auxiliary Power (SNAP-10A) Reactor

• 650 We (45 kWt)
• Satellite malfunction after 43 days
• U-ZrHx fuel (93 235U)
• Hastelloy N cladding
• Be reflector rods
• B4C control sleeves
• NaK coolant
• Thermoelectric
• 435 kg reactor mass

Experimental Criticality Benchmarks for SNAP
10A/2 Reactor Cores,A.W. Krass, K.L. Goluoglu,
ORNL/TM-2005/54, April 2005.
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Jupiter Icy Moons Orbitor (JIMO)

• 7 yrs to Jupiter, 11 yrs to first science
• Nuclear reactor
• 100-150 kWe
• Estimated mass 11,820 kg
• length of a football field
• Mass chemical stage to escape earth 12,000 kg
• Specific mass 100 kg/kw

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Europa

• Hydrothermal vents exist on Earth on the bottom
  of the oceans
• Diverse life exists at the vents that has never
  seen the sun and survives on a chemically based
  bio-sphere
• Recent evidence suggests that life on Earth may
  have developed on such vents first over a billion
  years ago
• Similar vents may exist on Europa
• Tidal forces may have heated the Europa crust
  enough to melt an ocean under the ice
• Conceivably, life may have developed in the
  Europa ocean also

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Thanks to James Cameron and Earthship Productions
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To Paraphrase

• Developing a new propulsion technology to travel
  to the outer planets-- 2B
• Building a new probe using radioisotopes to
  penetrate 10 miles of ice-- 200M
• Seeing the looks on the faces of children around
  the Earth as they see the first pictures of a new
  life form in an ocean on another world--
  Priceless

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Our Reach Must Exceed Our Grasp

• The goals of the CSNR and INL are to help the
  country extend its reach as far as
  technologically possible to see what marvels, as
  yet unknown, will come back in our grasp.

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Summary

• Nuclear technologies have been used in the US
  space program from the beginning
• All missions beyond Mars have been enabled by
  RTGs
• Nuclear rockets could enabled a human mission to
  Mars to be completed within 500 days total
• Fission power will be required for the surface of
  Mars for human support
• New alternative isotope power sources may enable
  unique science missions to map other planets
• The CSNR Summer Fellows program is successfully
  examining innovative technologies for space