Space Power: Government, Industry Explore Nuclear, Solar Space Engines.

• Author: Luckenbaugh, Josh

COLORADO SPRINGS, Colorado--More commercial and military activity is taking place in space, and the Defense Department and industry are investing in emerging propulsion technologies to move systems in orbit faster, farther and more efficiently.

Traditionally, spacecraft have used chemical reactions to release energy and generate thrust. However, this method is far less efficient than using nuclear thermal propulsion, said Lockheed Martin NextGen Strategy and Business Development Senior Manager Lisa May.

While nuclear thermal propulsion has the same thrust as chemical, "it is two to four times more efficient," May told reporters recently. Using specific impulse, or ISP--the measure of efficiency for a propulsion system --chemical has around 400 seconds of ISP, whereas nuclear has "beyond 700, up to 900" seconds, "which is what NASA has been talking about for getting humans to Mars," she said.

In 2021, the Defense Advanced Research Projects Agency selected Lockheed Martin as one of three prime contractors--along with General Atomics and Blue Origin--for Phase 1 of its Demonstration Rocket for Agile Cislunar Operations, or DRACO, program to showcase the potential of a nuclear thermal propulsion system in space, a DARPA release said.

This January, NASA announced it had partnered with DARPA on the DRACO program, describing a nuclear thermal rocket engine as "an enabling capability for NASA crewed missions to Mars." The goal is to demonstrate the system in orbit in fiscal year 2027, with the Space Force providing the launch vehicle for the DRACO mission, a DARPA statement said.

The program is about to enter Phase 2, which "will primarily involve building and testing on the non-nuclear components of the engine" such as valves, pumps, the nozzle and "a representative core without the nuclear materials in it," DARPA's program manager for DRACO Tabitha Dodson said during a panel discussion at the Space Foundation's Space Symposium in April. Dodson said then a Phase 2 decision is "quite close." However, at press time in mid-July, no contracts have been awarded.

Phase 3 of DRACO "will involve assembly of the fueled [nuclear thermal rocket] with the stage, environmental testing and launch into space to conduct experiments on the [nuclear thermal rocket] and its reactor," DARPA's website stated.

"There are no facilities on Earth that we could use for our DRACO reactor's power test... so we've always baselined doing our power test for the reactor in...