NASA and DARPA aim to perform nuclear engine for future crewed missions to Mars by 2027

A nuclear thermal rocket would significantly cut the transit time and lower risks for astronauts.

The program is called Demonstration Rocket for Agile Cislunar Operations (DRACO). NASA will “lead technical development of the nuclear thermal engine to be integrated with DARPA’s experimental spacecraft”. DARPA will manage the overall program, for instance, system integration, planning, assembling and integration of the engine with the spacecraft.

"Recent aerospace materials and engineering advancements are enabling a new era for space nuclear technology, and this flight demonstration will be a major achievement toward establishing a space transportation capability for an Earth-Moon economy,” said Jim Reuter, associate administrator for STMD.

A nuclear thermal engine would rely on a nuclear reactor. The reactor is used to generate extremely high temperatures needed for atomic fission. Thus, "the engine transfers the heat produced by the reactor to a liquid propellant, which is expanded and exhausted through a nozzle to propel the spacecraft".

Unlike conventional chemical propulsion, nuclear thermal rockets are several times more efficient.

The last nuclear thermal rocket engine testing was performed in the US in the mid of 20th centary — more than 50 years ago.