A new type of nuclear reactor has been designed to power outposts on Moon and Mars and it could be ready for its first in-space trial within a few years. The next step is a flight test for Kilopower experimental fission reactor which completed a series of ground tests from 2007 to 2018. Patrick McClure, Kilopower project lead at the Los Alamos National Laboratory said that Kilopower should be ready by 2022 although no off-earth demonstration has been scheduled yet.
He added that three years is a doable time frame which is not NASA’s stand who has been developing the project in collaboration with DOE. NASA’s Voyager 1 and Voyager 2 probes along with Curiosity Mars rover and New Horizons spacecraft employ radioisotope thermoelectric generators which convert the heat produced by the radioactive decay of plutonium-238 into electricity. RTGs produce relatively low power. It produces nearly 110 watts of electricity in Curiosity and the upcoming Mars 2020 rover.
A crewed outpost on Mars has higher energy demands around 40 kilowatts even for a small research envisioned by NASA for the late 2030s. Electricity will be required for water purification, oxygen generation for carbon-dioxide dominated atmosphere, charging up rovers, etc. Kilopower is a fission reactor and generates heat by splitting atoms into electricity through Sterling engines. The reactor was able to successfully convert 30% of the fission heat into electricity compared to 7% of regular RTG’s in a ground test series known as KRUSTY (Kilopower Reactor Using Sterling Technology). The project started in 2015 but the basic concepts were proved back in 2012 via an experiment called Demonstration Using Flattop Fissions (DUFF). KRUSTY and DUFF are characters in the Simpsons animated universe.
The reactor is designed to produce an output of 1 kilowatt of electrical power and can be scaled up to 10 kilowatts. NASA would need 4 of such reactors including one spare reactor. The 10-kilowatt machines would be just 11 feet in height and weigh close to 2000 kilograms. Without the astronaut shielding, it would weigh close to 1500 kilograms which would mean burying it in the ground.
The reactors are quite safe and there is no threat of radiation exposure if the rocket crashes back on Earth. The reactor is a self-regulating one if it gets too hot, the Stirling engines draw more heat away from uranium core and if temperature drops, the core naturally contracts which trap more neutrons and more splitting collisions. The device will need to dump a lot of heat on Mars due to the conversion efficiency of 30% will mean 70% of the heat will remain. It will come equipped with radiators.
A potential moon lander was the first task given to them as a demonstration mission for Kilopower but the concept will not end up flying as it targeted the lunar North pole and NASA was interested in the South Pole. Kilopower is the first fission reactor concept developed in the US in the last 40 years and is surely a milestone. US had previously launched reactors in experimental satellite, SNAP-10A in April 1965 but had to shut down after just 43 days. Although the Soviet Union was able to launch more than 30 fission reactors aboard satellites from 1967 to late 1980s.