Defense Advanced Research Projects Agency (DARPA) has requested immediate funding to demonstrate a nuclear thermal propulsion (NTP) system in space, according to the Pentagon's fiscal 2020 budget request, reported by Aviation Week & Space Technology.

DARPA's budget request includes approximately $10 million to begin the new program in 1H20.

The new space program is called Reactor On A Rocket (ROAR), will develop a high-assay low-enriched uranium (HALEU) propulsion system.

"The program will initially develop the use of additive manufacturing approaches to print NTP fuel elements…In addition, the program will investigate on-orbit assembly techniques (AM) to safely assemble the individual core element subassemblies into a full demonstration system configuration, and will perform a technology demonstration," DARPA’s budget document states.

The propulsion system superheats liquid hydrogen in a nuclear reactor and propels the plasma out a rocket nozzle. HALEU is more efficient than NASA's current chemical rockets, reducing flight time by a significant margin to deep space destinations.

According to Aviation Week, HALEU is being "developed as a fuel source for next-generation nuclear reactors, will use the fissionable isotope uranium-235 (U-235) with a concentration of more than 5% but less than 20%. This assay of U-235 is much lower than the 90% used in US naval reactors but also higher than the average 3-5% U-235 used in commercial reactors, allowing for smaller reactors."

Breakthroughs in nuclear technology have enabled engineers to develop cheaper, lighter and dependable NTP systems than when NASA tested its Nuclear Engine for Rocket Vehicle Application (NERVA) program in the 1960s.

Once the NTP system is mounted onto a rocket, DARPA is expected to pilot test missions into deep-space, but no timeframe has been given in the budget request.

The budget request also had no mention of what the flight demonstration mission would involve. Often dummy payloads are mounted within the capsule to avoid damaging expensive space probes.

Could DARPA's ROAR program to mature nuclear rocket engines be for deep-space travel under President Trump's new Space Force?