NASA is set to begin testing a radical ‘nuclear engine’ that could provide power for astronauts on the Martian surface.
Dubbed the ‘Kilopower’ it would use a uranium rector the size of a toilet roll to create heat.
A high efficiency Stirling engine would then convert this to electricity, in a system that works in a similar way to a car engine.
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NASA plans to test the radical nuclear power source on Earth later this year. Pictured, an artist’s impression of the system on the Martian surface.
HOW IT WORKS
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, similar in some way to an automobile engine.
NASA’s Space Technology Mission Directorate (STMD) has provided multi-year funding to the Kilopower project.
The technology could produce from one to 10 kilowatts of electrical power, continuously for 10 years or more.
The average U.S. household runs on about five kilowatts of power.
Testing is due to start in November and go through early next year, with NASA partnering with the Department of Energy’s (DOE) Nevada National Security Site to appraise fission power technologies.
‘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,’ said Lee Mason, STMD’s principal technologist for Power and Energy Storage at NASA Headquarters.
The Y12 National Security Complex in Oak Ridge, Tennessee is providing the reactor core for the tests of the system.
Having a space-rated fission power unit for Mars explorers would be a game changer, Mason claims.
It would kill off worries about meeting power demands during the night or long, sunlight-reducing dust storms.
The ‘nuclear engines’ that could provide power to the first humans on the red planet
‘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,’ he said.
‘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,’ said Patrick McClure, project lead on the Kilopower work at the Los Alamos National Laboratory.
NUCLEAR POWER IN SPACE
NASA has flown a number of missions powered by radioisotope thermoelectric generators (RTGs) over the past five decades.
The technology was onboard the two Viking Mars landers, and the Curiosity rover now at work on the Red Planet.
The Apollo expeditions to the moon, the two Voyager spacecraft, and the New Horizons probe to Pluto and beyond, as well as the just-concluded Cassini mission at Saturn also used it.
Thanks to the Cold War-era space race, U.S. engineers found an easy source – Plutonium-238, a byproduct created during the production of weapons-grade plutonium-239.
RTGs produce electricity passively with no moving parts, using the heat from the natural decay of their radioisotope heat source.
‘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,’ said David Poston, Los Alamos’ chief reactor designer.
‘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.’
‘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 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.’
Small enough in size, multiple units could be delivered on a single Mars lander and operated independently for human surface missions.
THE STIRLING ENGINE
Robert Stirling, who designed the famous Stirling engine, was a Scottish clergyman who lived in Perthshire in the 1800s
The Reverend Dr Robert Stirling was a Scottish clergyman who lived in Perthshire in the 1800s.
He invented what he called the ‘Heat Economiser’ – a device for improving the thermal and fuel efficiency of a variety of industrial processes.
Stirling obtained a patent for his engine in 1816, however he described a number of additional applications for use in glass and other furnaces.
In 1818, Stirling built his first practical version of his engine, designed pump water from a stone quarry.
In the 1820s, he teamed up with his brother, James, who suggested that greater power output might be obtained using air pressures greater than atmospheric pressure.
The brothers received further patents in 1827 and 1840 for improvements to their air engine.
His original 1816 patent contained all the elements of what is now called the ‘Stirling cycle engine’ – a power piston, a displacer to move air between hot and cold ends, and a regenerator.
Robert Stirling’s original design was called the ‘Heat Economiser’, a device for improving the thermal and fuel efficiency of a variety of industrial processes
The power piston compresses air in the cold end of the displacer cylinder, which then shifts the air from the cold to hot end. The piston is driven back by the air expanding in the hot end.
Unfortunately, none of his experimental work of papers have survived, except two model engines, which now live in the Universities of Glasgow and Edinburgh.