Forward-looking: NASA is working with DARPA to develop a new fission-based engine for next-generation spacecraft. The space agency wants to test the prototype by 2027 so the technology can be adopted for future human trips to deep space and Mars.

NASA and DARPA are playing with atoms, and they are eager to show the world the results. The US military research and development agency will work with a contractor company, which will be chosen in the coming weeks, with a total expected budget of hundreds of millions of dollars.

The two US agencies want to develop and test a spacecraft engine based on nuclear fission, a technology that NASA has used for decades to power the most daring exploration missions like the twin Voyager probes and the Mars Science Laboratory. Those were all unmanned missions; using nuclear power for a crew-based mission is still uncharted territory.

NASA has been studying nuclear propulsion for space exploration for decades, depicting nuclear fission as a potential alternative to conventional, chemical-based rocket engines. Nuclear fission, which would produce thermal energy to turn a hydrogen propellant into the thrust needed to move a spacecraft onward, is much more efficient that traditional propellants.

With this hypothetical nuclear engine, NASA engineers say a human trip from Earth to Mars would take four months instead of the estimated nine months needed with a chemically-powered engine. Shorter travels would greatly reduce the time astronauts would be exposed to dangerous deep space radiations, and it would require fewer supplies and food as well.

According to Pam Melroy, NASA deputy administrator and former astronaut, "if we have swifter trips for humans, they are safer trips." DARPA is already working on a nuclear-powered space program, and NASA is now taking part in it too. The space agency will provide a $110 million budget for fiscal year 2023 alone.

Two years ago, DARPA awarded some funds to General Atomics, Lockheed Martin and Blue Origin to design a nuclear reactor for a spacecraft. In March, the US agency will pick the company tasked with manufacturing said reactor. Instead of space exploration, DARPA wants to use the new engine to move satellites around the Moon as part of the US Space Force initiative.