NASA has assigned Sierra Lobo Inc. to provide equipment that converts reactor heat to electricity aboard a planned Mars spacecraft, advancing a mission designed to test nuclear electric propulsion beyond Earth orbit.
The equipment will use a closed Brayton cycle and be integrated with a reactor under development at the U.S. Department of Energy’s Idaho National Laboratory. NASA is targeting a late 2028 launch for the spacecraft, called Space Reactor-1 (SR-1) Freedom.
Sierra Lobo’s assignment falls under a NASA contract for spaceflight development and operations awarded in February 2024. The overall contract has a maximum potential value of about $282.1 million. NASA gave no separate price or completion date for the SR-1 assignment in its Oct. 20 announcement.
Electricity from the reactor is intended to power the spacecraft and its propulsion system. NASA says the reactor will remain off until SR-1 has left Earth orbit. The agency’s safety plans call for reviews involving multiple agencies and continuing oversight by a NASA chief safety officer.
The spacecraft will incorporate the Power and Propulsion Element developed for NASA’s Gateway program. A NASA technical presentation identifies removing excess heat and integrating the nuclear module with the spacecraft as engineering challenges. SR-1 Freedom program director Steve Sinacore said the contract actions would “reduce technical risk” as NASA works toward its launch target.
NASA announced the mission in March as a planned first use of a fission reactor for propulsion beyond Earth orbit. The agency has cited SNAP-10A, a U.S. reactor flown in 1965 that remained in Earth orbit, as a historical comparison. NASA also says lessons from SR-1 could guide a later reactor intended to supply electricity on the lunar surface where sunlight is unavailable.
SR-1 is planned to carry three SkyFall helicopters to Mars. NASA schedules a first Mars flyby in 2029, with the helicopters landing after a second approach in fall 2030. The agency has scheduled a virtual SkyFall landing-site workshop for Feb. 9-10, 2027.
