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

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

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

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

Radioisotope Thermoelectric Generator (RTG) have been used since the Apollo days Pu-238 Pu-238 Non-weaponizable Non-weaponizable 87.7 year half-life 87.7 year half-life Alpha decay plus gamma rays Alpha decay plus gamma rays Heavily encapsulated Heavily encapsulated Qualified against accident scenarios- fire, impact, explosion Qualified against accident scenarios- fire, impact, explosion 6-8% conversion efficiency 6-8% conversion efficiency No moving parts No moving parts Around 200 kg/kWe Around 200 kg/kWe Continuous power Continuous power

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) 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 The New Horizons mission to Pluto – the highest- priority exploration mission of the decade – depended on INL fabrication

Radioisotope Power Systems (RPS) Current RTGs are simple, robust, and proven technology Current RTGs are simple, robust, and proven technology Pu-238 running out Pu-238 running out CSNR is currently examining possible alternative isotopes and new materials to ensure immobilization in accident scenarios CSNR is currently examining possible alternative isotopes and new materials to ensure immobilization in accident scenarios INL has facilities to fabricate new RPS systems INL has facilities to fabricate new RPS systems Current design study: Using RPS sources for space power and for long duration (>2yr) Remotely Piloted Vehicles for planetary observation Current design study: Using RPS sources for space power and for long duration (>2yr) Remotely Piloted Vehicles for planetary observation

Radiation Doses What is your average mREM dose? What is your average mREM dose? 360 mREM/year 360 mREM/year A nuclear power plant worker can receive up to: A nuclear power plant worker can receive up to: 5,000 mREM/year 5,000 mREM/year What is an astronaut’s dose? What is an astronaut’s dose? 1,000 mREM/week 1,000 mREM/week

Energy Densities of Known Sources Reaction Specific Energy (MJ/kg) Chemical7-10 Fission (100%) 71E06 Fusion (100%) 750e06 Antimatter90000e06

NTR was developed and proven in the Rover/NERVA programs in the 1960s Pewee operated at 2550 K for 40 minutes at 503 MW 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 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 Pewee was envisioned as an orbital tug to support a Lunar base

CSNR Summer Fellows Study results- NTR-based ESAS Architecture

Systems Nuclear Auxiliary Power (SNAP-10A) Reactor 650 We (45 kWt) 650 We (45 kWt) Satellite malfunction after 43 days Satellite malfunction after 43 days U-ZrH x fuel (93% 235 U) U-ZrH x fuel (93% 235 U) Hastelloy ® N cladding Hastelloy ® N cladding Be reflector rods Be reflector rods B 4 C control sleeves B 4 C control sleeves NaK coolant NaK coolant Thermoelectric Thermoelectric 435 kg reactor mass 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.

Jupiter Icy Moons Orbitor (JIMO) 7 yrs to Jupiter, 11 yrs to first science 7 yrs to Jupiter, 11 yrs to first science Nuclear reactor Nuclear reactor kWe kWe Estimated mass= 11,820 kg Estimated mass= 11,820 kg length of a football field length of a football field Mass chemical stage to escape earth = 12,000 kg Mass chemical stage to escape earth = 12,000 kg Specific mass = 100 kg/kw Specific mass = 100 kg/kw

Europa Hydrothermal vents exist on Earth on the bottom of the oceans 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 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 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 Similar vents may exist on Europa Tidal forces may have heated the Europa crust enough to melt an ocean under the ice 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 Conceivably, life may have developed in the Europa ocean also

Thanks to James Cameron and Earthship Productions

To Paraphrase: Developing a new propulsion technology to travel to the outer planets-- $2B 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 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 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

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. 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.

Summary Nuclear technologies have been used in the US space program from the beginning Nuclear technologies have been used in the US space program from the beginning All missions beyond Mars have been enabled by RTGs 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 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 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 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 The CSNR Summer Fellows program is successfully examining innovative technologies for space