The in-space flight demonstration of a nuclear thermal rocket engine vehicle will take place no later than 2027. The project is called Demonstration Rocket for Agile Cislunar Operations (DRACO).

DARPA partnered with NASA's Space Technology Mission Directorate on the DRACO project.

They will use the TRISO pebble bed fuel made by BWXT.

The agreement is structured as a milestone-based other transaction authority agreement with a total value of $499 million, said Tabitha Dodson, program manager for DRACO at DARPA.

Officials did not disclose the thrust the DRACO engine will produce, although Calomino said it will have a specific impulse, a measure of efficiency, of about 700 seconds. That is significantly higher than even the best chemical engines (260-460 ISP. most around 300-340) although the design goal for NTP systems is 850 to 900 seconds.

NTR (Nuclear thermal rocket) propulsion offers a high thrust-to-weight ratio around 10,000x greater than electric propulsion (ion drives) and with two-to-five times greater efficiency than in-space chemical propulsion.