City Labs Seeks Major Increase in Tritium Heater Limits
The firm wants FAA approval to launch 10 million curies of tritium to keep lunar landers alive during the long lunar night.
Updated on Oct. 31, 2026 in Nuclear
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City Labs has requested Federal Aviation Administration approval to launch 10 million curies of tritium to power thermal heaters for lunar missions. The company plans to use this radioactive isotope to maintain lander temperatures during the two-week lunar night.
Why it matters
Tritium heaters offer a significant mass reduction compared to battery-based thermal management systems, which are currently heavy and prone to failure during the long lunar night. This shift could prevent the total loss of lunar hardware when solar power is unavailable.
A single tritium heater module generates 30 milliwatts of heat using 1,000 curies of tritium. Scaling to 10 million curies would provide 300 watts of thermal output, replacing battery systems that require 5 kilograms of mass per watt.
The players
City Labs
A developer of nuclear-powered satellite components and modular radioisotope heater units.
Federal Aviation Administration
The U.S. government body responsible for regulating commercial space payload authorizations.
The details
City Labs utilizes modular tritium units placed directly onto satellite chips or batteries to provide steady heat. Tritium, a radioactive isotope of hydrogen, releases heat as it undergoes beta decay. By applying these heaters to lunar landers, engineers can maintain hardware temperatures during the 14-day lunar night, avoiding the reliance on traditional chemical batteries that often fail in extreme cold.
Timeline
2019: National Security Presidential Memorandum 20 regulatory path opened.
July 2026: BOHR nuclear-powered satellite launched.
October 2026: City Labs published BOHR telemetry data.
December 2026: Expected formal submission of FAA application.
January 2027: Target date for FAA amendment approval.
The Tech Race
This move marks a rapid expansion from the initial 20-curie payload launched in July 2026 to a 10 million-curie system. The effort positions City Labs to establish a dominant standard for thermal management in commercial lunar exploration.
Commercial lunar mission operators could gain the ability to survive the lunar night without losing expensive landers, potentially saving millions in mission costs. This hardware is intended for integration into future lunar lander designs, pending the upcoming regulatory review.
The takeaway
Reliable heat is the primary barrier to maintaining landers during the 14-day lunar night, an environment that currently risks $400 million in equipment losses. Watch for the FAA's decision on the 10 million curie limit in January 2027, as it will signal the viability of large-scale nuclear heating.
What happens next
City Labs plans to file the formal FAA application in December 2026, with an expected regulatory amendment by January 2027.
Further reading
For more on evolving space power standards, see Nuclear.
Source note: This article includes information reported by Satnews.
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