NASA and DARPA to partner on nuclear thermal propulsion demonstration

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WASHINGTON — NASA and the Defense Advanced Research Projects Agency will cooperate on the development and flight demonstration of a nuclear propulsion system with applications for both national security and space exploration.

During a special session of the AIAA SciTech Forum Jan. 24, NASA Administrator Bill Nelson announced that the two agencies would work together on DARPA’s existing Demonstration Rocket for Agile Cislunar Operations (DRACO) program to demonstrate nuclear thermal propulsion (NTP), a technology that offers more efficient propulsion than conventional chemical rockets.

“NASA will partner with our longtime partner, DARPA, to develop and demonstrate advanced nuclear thermal propulsion,” Nelson said in brief remarks at the conference. “Our goal is to launch and demonstrate a successful nuclear thermal engine as soon as 2027.”

The partnership is governed by a non-reimbursable agreement signed by the two agencies earlier this month. NASA will be responsible for the development of the nuclear engine, with DARPA handling integration of that propulsion system into a spacecraft and launching it.

“We’ve been focused on structuring with clear lines of responsibility,” said NASA Deputy Administrator Pam Melroy on a panel after Nelson’s announcement. NASA had been cooperating on DRACO at a lower level before this announcement.

“The bottom line is that we have really strong communication,” said DARPA Director Stefanie Tompkins on the panel. The teams at both agencies “will adapt as needed” over the course of the program.

Neither DARPA nor NASA have disclosed details about the DRACO demonstration mission itself, using a spacecraft called X-NTRV in the agreement. Melroy said on the panel that the vehicle would operate in orbit at an altitude of at least 700 kilometers, and perhaps as high as 2,000 kilometers, to ensure that any radioactive materials would have decayed to acceptable levels before reentry.

The two agencies had been separately pursuing NTP projects. DARPA started DRACO with three Phase 1 awards in April 2021 to teams led by Blue Origin, General Atomics and Lockheed Martin to work on preliminary designs of reactors and spacecraft.

In May 2022, DARPA announced it was soliciting proposals for DRACO Phases 2 and 3 to develop and test the engine and perform a flight demonstration, then planned for fiscal year 2026. DARPA had not selected an awardee at the time of the NASA partnership, but Tompkins said an award could come in “a couple of months.”

NASA has also been working on NTP technologies, including awards in July 2021 in cooperation with the Department of Energy to teams led by BWX Technologies, General Atomics and Ultra Safe Nuclear Technologies. Those contracts, valued at $5 million each for one year, covered NTP reactor design.

NASA has been pushed by Congress to invest in NTP, with appropriations bills setting aside funding for such work at levels often far above what the agency requested. NASA leadership, though, has embraced that technology more recently as critical to future human missions to Mars, a finding from a February 2021 National Academies study that called on NASA to pursue “aggressive” development of nuclear propulsion so that it would be available for a human Mars mission in the late 2030s.

“The key thing is that this will allow us to evaluate the opportunity to move faster,” Melroy said of NTP, referring to its potential to shorten travel times to and from Mars because of its higher efficiency. “If we have swifter trips for humans, they are safer trips.”

DARPA, and the broader national security community, is interested in NTP because of the much greater maneuverability that it offers, Tompkins said. Asked about what kinds of maneuverability, she responded, “all of the above.” DARPA has previously discussed using the technology for operations in cislunar space between the Earth and moon, an area of increasing national security interest.

“Our goals are not in conflict,” Tompkins added. “We are very much looking for the same thing.”