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Recent Developments in Nuclear Power for Space Exploration

KiloPower: A Gateway to Abundant Power for Exploration:

NASA Glenn, Cleveland, OH – NASA is pushing forward to test a key nuclear energy source that could literally empower human crews on the Mars surface, energizing habitats and running on-the-spot processing equipment to transform Red Planet resources into oxygen, water and fuel. (Video)

The agency’s Space Technology Mission Directorate (STMD) has awarded multi-year funding to the Kilopower project (NASA slides – PDF file). Testing started this Fall and will go through early next year, with NASA partnering with the Department of Energy’s (DOE) Nevada National Security Site to evaluate fission power technologies.

kilopower slide from NASA 2016

Lee Mason, STMD’s principal technologist for Power and Energy Storage at NASA Headquarters, explains;

“The Kilopower test program will give us confidence that this technology is ready for space flight development. We’ll be checking analytical models along the way for verification of how well the hardware is working.” 

NASA’s Glenn Research Center in Cleveland, OH, is managing all phases of the Kilopower Project, from designing and building the hardware, with contributions from NASA’s Marshall Space Flight Center in Huntsville, Alabama, through developing the test plan and operating the tests. The Y12 National Security Complex in Oak Ridge, Tennessee is providing the uranium for the reactor core.

The DOE/National Nuclear Security Administration infrastructure and expertise are instrumental for success, Mason points out, are the talents of Los Alamos National Laboratory engineers in New Mexico.

Patrick McClure, project lead on the Kilopower work at the Los Alamos National Laboratory, says;

“A space nuclear reactor could provide a high energy density power source with the ability to operate independent of solar energy or orientation, and the ability to operate in extremely harsh environments, such as the Martian surface.”

David Poston, Los Alamos’ chief reactor designer, adds;

“The reactor technology we are testing could be applicable to multiple NASA missions, and we ultimately hope that this is the first step for fission reactors to create a new paradigm of truly ambitious and inspiring space exploration. Simplicity is essential to any first-of-a-kind engineering project – not necessarily the simplest design, but finding the simplest path through design, development, fabrication, safety and testing.”

Moving Beyond Solar power  – Mason points out the pioneering Kilopower reactor represents a small and simple approach for long-duration, sun-independent electric power for space or extraterrestrial surfaces. Offering prolonged life and reliability, such technology could produce from one to ten kilowatts of electrical power, continuously for 10 years or more.

“What we are striving to do is give space missions an option beyond RTGs, which generally provide a couple hundred watts or so,” Mason says.

The prototype power system uses a solid, cast uranium-235 reactor core, about the size of a paper towel roll. Reactor heat is transferred via passive sodium heat pipes, with that heat then converted to electricity by high-efficiency Stirling engines. A Stirling engine uses heat to create pressure forces that move a piston, which is coupled to an alternator to produce electricity.

Having a space-rated fission power unit for Mars explorers would be a game changer, Mason adds. There would be no worries about meeting power demands during the night or long, sunlight-reducing dust storms.

Mason emphasizes that it solves those issues and provides a constant supply of power regardless of where you are located on Mars. Fission power could expand the possible landing sites on Mars to include the high northern latitudes, where ice may be present.

“The big difference between all the great things we’ve done on Mars, and what we would need to do for a human mission to that planet, is power. This new technology could provide kilowatts and can eventually be evolved to provide hundreds of kilowatts, or even megawatts of power. We call it the Kilopower project because it gives us a near-term option to provide kilowatts for missions that previously were constrained to use less.”

The novel energy-providing technology also makes possible a modular option for human exploration of Mars. Small enough in size, multiple units could be delivered on a single Mars lander and operated independently for human surface missions.

BWXT to Develop Advanced Nuclear
Thermal Propulsion Technology for NASA

As NASA pursues innovative, cost-effective alternatives to conventional propulsion technologies to forge new paths into the solar system, researchers at NASA’s Marshall Space Flight Center in Huntsville, Alabama, say nuclear thermal propulsion technologies are more promising than ever, and have contracted with BWXT Nuclear Energy, Inc. of Lynchburg, Virginia, to further advance and refine those concepts.

bwxt LEU

Fact Sheet – includes a conceptual design of a totally contained engine ground test.

Part of NASA’s Game Changing Development Program, the Nuclear Thermal Propulsion (NTP) project could significantly change space travel, largely due to its ability to accelerate a large amount of propellant out of the back of a rocket at very high speeds, resulting in a highly efficient, high-thrust engine.

A nuclear thermal rocket has double the propulsion efficiency of the Space Shuttle main engine, one of the hardest-working standard chemical engines of the past 40 years. That capability makes nuclear thermal propulsion ideal for delivering large, automated payloads to distant worlds.

“As we push out into the solar system, nuclear propulsion may offer the only truly viable technology option to extend human reach to the surface of Mars and to worlds beyond,” said Sonny Mitchell, Nuclear Thermal Propulsion project manager at Marshall. “We’re excited to be working on technologies that could open up deep space for human exploration.”

An NTP system can cut the voyage time to Mars from six months to four and safely deliver human explorers by reducing their exposure to radiation. That also could reduce the vehicle mass, enabling deep space missions to haul more payload.

Given its experience in developing and delivering nuclear fuels for the U.S. Navy, BWXT will aid in the design and testing of a promising, low-enriched uranium-based nuclear thermal engine concept and “Cermet” — ceramic metallic — fuel element technology.

During this three-year, $18.8-million contract, the company will manufacture and test prototype fuel elements and also help NASA properly address and resolve nuclear licensing and regulatory requirements.

BWXT will aid NASA in refining the feasibility and affordability of developing a nuclear thermal propulsion engine, delivering the technical and programmatic data needed to determine how to implement this promising technology in years to come.

Background on RTGs

Plutonium_pelletNASA has used radioisotope thermoelectric generators (RTGs) for decades to convert heat from the natural decay of radioactive elements (PU-238) directly into electricity.

Nuclear fission provides a compact, reliable source of electricity, especially in situations where solar panels would be ineffective.

The radioactive decay of the PU-238 isotope causes a temperature difference across plates of two different kinds of metal — one connected to the reactor and the other to a radiator, which produces a voltage. RTGs have the benefit of containing no moving parts, which could wear down on long missions, with no chance for maintenance or replacement.  Advanced nuclear power systems, like Kilopower, use a Stirling Engine, which does have moving parts, and which also has an estimated 14 year operational life.

Infograpohic on Nuclear Energy for Deep Space Missions

Source (used with permission): SPACE.com: All about our solar system, outer space and exploration

For more than 50 years, NASA's robotic deep space probes have carried nuclear batteries provided by the U.S. Department of Energy. Even the crewed Apollo moon landings carried nuclear powered equipment.

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