Guidelines for In-Space Cryogenic Propellant Transfer

The ability to perform in-space cryogenic propellant transfer is critical to the success of the Artemis campaign. The Human Lander System (HLS) for the Artemis Program includes two vehicles – the SpaceX “Starship” and the Blue Origin “Blue Moon Mark II”. The concept of operations for both spacecraft requires the transfer of cryogenic propellants in space. The transfer of cryogenic propellants between independent spacecraft has never been demonstrated. But progress is being made. Under the provisions of a NASA Space Technology Missions Directorate (STMD) 2020 Tipping Point Contract, SpaceX demonstrated a tank-to-tank transfer of liquid oxygen during its March 2024 Starship flight. In 2024, the Cryogenic Fluid Management Portfolio Project Office (CFMPP) at NASA’s Marshall Space Flight Center tasked a group of engineers to write a high-level guidelines document for In-Space Cryogenic Propellant Transfer (ISCPT). The document is not prescriptive in nature but is intended to assist NASA and Commercial Projects in developing architectures and ConOps for systems under development. The document includes several different sections. First, the document “sets the stage” by making some initial assumptions. Then the document discusses procedures for settled propellant transfer, unsettled propellant transfer, cryocoupler construction, and safety considerations.