The agreement, announced October 21, 2026, from Los Alamos, New Mexico, extends the company’s line of nuclear power development. It builds directly on the Kilopower Reactor Using Stirling Technology, or KRUSTY, work performed in 2018 by key members of the SpaceNukes team while employed by Los Alamos National Laboratory and NASA. That effort was the only full-power ground test of a new American space reactor in five decades.
Under the current agreement, SpaceNukes and Los Alamos National Laboratory will design, build, and conduct a follow-on nuclear ground test of a Kilopower reactor incorporating active control rod operation. This represents an advancement beyond the passively controlled architecture demonstrated in the 2018 KRUSTY test. The Fat Cat program is managed by Dr. Tabitha Dodson in DARPA’s Defense Sciences Office and seeks to advance autonomous reactor operation for national security missions.
The phased program structure includes design, procurement, and integration gates leading to the ground demonstration. It is intended to produce both nuclear-tested hardware and the engineering basis for autonomous, actively controlled reactor operation. Integration work will be conducted at the company’s workshop in Medina, Ohio, led by Chief Engineer Marc Gibson.
Patrick McClure, COO of SpaceNukes, said the award recognizes the maturity and continuity of the team that designed, built, and tested KRUSTY in 2018. He said the company is proud to work alongside Dr. Dodson and Los Alamos National Laboratory to deliver the next demonstrated step in American nuclear power. CEO Andy Phelps said there is no substitute for demonstrated technology when American national security objectives are at stake, adding that the award allows the company to advance the work begun in the KRUSTY program and bring another tested capability forward for the nation.
According to the company, the work positions American industry to provide reliable nuclear power across a broader range of mission profiles, including those requiring dynamic power management and rapid response under varying operational conditions. SpaceNukes holds a license from Los Alamos National Laboratory for the Kilopower technology and operates from headquarters in Los Alamos, New Mexico, with workshops in Los Alamos offering additive 3D printing and in Medina, Ohio, offering thermal and vacuum capabilities.
The program advances through design, procurement, and integration gates leading to the ground demonstration, with integration work proceeding at the Medina, Ohio, facility under Marc Gibson.
