Summary
NASA says Sierra Lobo will provide the closed Brayton cycle system that converts heat from SR-1 Freedom’s fission reactor into electricity. The spacecraft is planned to carry a three-helicopter science mission to Mars, launching in late 2028.
NASA has advanced development of the nuclear power module for its Space Reactor-1 (SR-1) Freedom mission, naming Sierra Lobo Inc. to provide the system that will convert reactor heat into electricity. The spacecraft is planned to launch in late 2028 and demonstrate nuclear electric propulsion in deep space while delivering a three-helicopter science mission to Mars.
The work follows contract actions agreed by NASA and its partners. Sierra Lobo’s work will be carried out under NASA’s Space Flight Systems Development and Operations Contract III, awarded in 2024, and will support hardware design, development, testing and operations at NASA’s Glenn Research Center in Cleveland.
Turning reactor heat into spacecraft power
The nuclear power module combines a fission reactor with a closed Brayton cycle power-conversion system. The reactor, being designed and developed by the Department of Energy’s Idaho National Laboratory, produces heat through nuclear fission. Sierra Lobo’s system is to convert that heat into electricity for the spacecraft’s systems and electric propulsion.
In a closed Brayton cycle, a working fluid circulates through a loop: heating makes it expand and drive machinery that generates power, after which it is cooled and recirculated. In SR-1 Freedom, the conversion system links the reactor’s heat to electrical power. That is distinct from using reactor heat directly to propel a vehicle: NASA describes the electricity as powering the spacecraft’s electric propulsion.
NASA says the module will be located at the end of the spacecraft’s boom. The reactor will remain inactive until the spacecraft has left Earth orbit. The agency says safety measures include interagency safety reviews, oversight by a NASA chief safety officer, regulatory compliance and a design process focused on hazards, failure tolerance and nuclear safety.
A Mars mission and a longer-term power objective
SR-1 Freedom is intended to carry SkyFall, a team of three Mars helicopters evolved from NASA’s Ingenuity design. NASA says the helicopters will collect scientific data, demonstrate exploration zones and help identify potential water sources. The agency describes the flight as the first demonstration of fission power beyond Earth’s orbit and as a step toward future deep-space missions using fission-powered systems.
NASA also links the technology to plans for a future Moon Base. Fission systems could provide power during lunar darkness and in locations where solar power alone is insufficient, according to the agency. The SR-1 Freedom update marks progress on a key component, while the reactor and power-conversion system still need to be integrated into the spacecraft for the planned mission.