Firefly Aerospace plans to carry a radioisotope heater unit from Zeno Power aboard a lunar landing mission scheduled for 2028, to test the ability of a small nuclear heat source to keep equipment operating during the lunar night, when temperatures fall to about 170 degrees Celsius below zero.
The companies announced on August 19 that a Blue Ghost lander mission will include a package Zeno calls Survive-the-Night. The self-contained package contains a radioisotope heater unit, or RHU, that uses the radioactive isotope Americium-241 to produce 5 watts of thermal power. This heat will be used to protect the package and its components, including communications, electrical power and associated subsystem equipment.
Tyler Bernstein, chief executive of Zeno Power, said the practical goal of the experiment is simple: to send a signal five days after the start of the lunar night confirming that the payload is still operating. This aligns with an incentive NASA included in a recent mission solicitation under the Commercial Lunar Payload Services program to demonstrate technologies that enable equipment to survive the lunar night. Firefly was one of three companies selected for that solicitation in June.
Why Does This Test Matter?
Current lunar spacecraft generally operate during lunar daylight periods, but surviving the night allows equipment to operate through multiple cycles rather than ending the mission at sunset. This capability is becoming more important as NASA develops plans for a lunar base that will require more continuous power and thermal systems.
Firefly believes the experiment will provide data to help it assess the use of RHUs on later missions, either to protect a specific payload or to heat the entire lander. The companies did not disclose the package’s mass or size, but Bernstein said the heater unit itself is approximately the size of a silver-dollar coin.
Technical and Regulatory Test
This will be Zeno Power’s first space mission, as well as the first mission for this type of commercial radioisotope-heating power source. In July, City Labs launched the first commercial satellite equipped with a nuclear power source, but it used a tritium battery producing power at the microwatt level.
The challenge is not limited to manufacturing the unit. The companies are working on procedures to safely integrate the payload into the Blue Ghost spacecraft, along with the testing and preparations required for launch. Zeno describes the mission as a test of the regulatory approval pathway for launching commercial nuclear payloads, a pathway that has only recently been tested in practice with the City Labs satellite.
Toward a Larger Lunar Market
Zeno is increasing production of RHUs in anticipation of future demand that could reach hundreds of units as the number of missions headed to the lunar surface grows. The company is also developing power sources that use Stirling generators to produce electricity, and said it has secured sufficient supplies of Americium-241 to meet these plans.
Other landing companies are conducting similar tests. Intuitive Machines said it also sought the survive-the-night incentive in the same CLPS solicitation, and that a landing mission it won in June and is scheduled to launch in August 2028 will likewise use an RHU based on Americium-241. A company official said the incentive is worth $15 million, but noted that the mission needs compensation from NASA because a suitable commercial market for insuring nuclear payloads is not available.