# Presentation: 087301

## 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-**
**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?**

## 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**

## 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**

## 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**

**Notes:**
INL is already an important late-stage contributor in the preparation of these so-called space batteries.
Since last year, we’ve been tasked with the final assembly and testing of these units in a dedicated, new facility we have at our Materials and Fuels Complex.
Once we’ve established that the units operate exactly as they’re supposed to, we ship them to NASA.
A “space battery” we’re working on right now is scheduled for use in the New Horizons mission to Pluto – set to launch early next year.  Some time between 2015 and 2020, the INL-provided space battery aboard New Horizons  – will become the first “Made in Idaho” product to venture beyond the Solar System.

## 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 (>2yr) Remotely Piloted Vehicles for planetary observation**

**Notes:**
A large part of the appeal of these systems is their simplicity.
The electricity-generating RTGs take advantage of thermocouples, a technology that’s been around for over a hundred years.
Simply, thermocouples are units made from two very different types of metal.  When one type of metal is heated, while the other is cooled...electric current is induced.  RTGs generate the needed heat from the natural decay of a radioisotope.
The heat-generating RHUs don’t even rely on thermocouples – they directly release the heat energy from radioisotope decay.

## Slide 8

## 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 astronaut’s dose?
- 				1,000 mREM/week

## Energy Densities of Known Sources

| Reaction | Specific Energy (MJ/kg) |
| --- | --- |
| Chemical | 7-10 |
| Fission  (100%) | 71E06 |
| Fusion  (100%) | 750e06 |
| Antimatter | 90000e06 |

## Slide 11

## Slide 12

## 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

## CSNR Summer Fellows Study results-NTR-based ESAS Architecture

## 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.

**Notes:**
The one space nuclear reactor that the U.S. ever launched into space.  High costs and long project development time killed advances of this project in 1965.

## 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

## 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**

## Thanks to James Cameron and Earthship Productions

## 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

## 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.

## 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**