Starship In-Orbit Refueling Test

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Settling Thrust DynamicsSettling Thrust Dynamics
Cryogenic Propellant TransferCryogenic Propellant Transfer

Starship In-Orbit Refueling Test

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aetheris

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SpaceX is gearing up for a groundbreaking demonstration of in-space refueling technology, with plans to transfer propellant between two orbiting Starships as early as March 2025, according to NASA officials. This critical milestone will pave the way for future lunar missions and represents a significant step towards SpaceX's ambitious goal of enabling long-duration space travel.

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Starship-to-Starship Docking

SpaceX's Starship docking system, based on the flight-proven Dragon 2 design, is being developed to enable critical spacecraft connections for lunar missions

. This system will allow Starship to:

Dock with NASA's Orion spacecraft and Gateway station in lunar orbit
Connect two Starships for in-orbit refueling operations
Potentially link with other spacecraft following International Docking System Standards

Recent testing at NASA's Johnson Space Center validated the system's ability to perform both active and passive docking roles across over 200 scenarios

. This versatile capability is essential for Starship's role in the Artemis program and future deep space exploration, enabling crew transfers, resupply missions, and the assembly of larger structures in orbit

4 sources

Settling Thrust Dynamics

SpaceX is developing techniques to manage propellant behavior during orbital refueling operations. A key challenge is controlling propellant slosh and ensuring proper settling in microgravity conditions. To address this, SpaceX plans to use "settling thrusters" to generate a small acceleration, positioning the liquid propellants at the bottom of the tanks for efficient transfer

. The company is working to characterize the optimal settling thrust levels and durations needed to facilitate smooth propellant flow between vehicles while docked in orbit

. Key aspects being studied include:

Propellant slosh dynamics as Starship maneuvers in space
Required settling thrust levels to properly position propellants
Ullage maintenance to prevent gas ingestion during transfer
Pressure control systems to drive propellant flow

Mastering these complex fluid dynamics is crucial for enabling reliable orbital refueling, a cornerstone of SpaceX's plans for long-duration missions beyond Earth orbit

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Cryogenic Propellant Transfer

SpaceX's cryogenic propellant transfer technology is crucial for enabling long-duration space missions, including lunar landings. The company has already demonstrated intertank transfer of cryogenic propellants during Starship's third test flight in March 2024

. This successful test involved transferring approximately 10 metric tons of liquid oxygen between tanks within a single Starship vehicle

. The next major milestone is a more complex ship-to-ship propellant transfer demonstration planned for 2025. This test will involve launching two Starships into low Earth orbit, with one serving as a "tanker" and the other as the recipient spacecraft

. Engineers must address several challenges, including managing propellant slosh in microgravity, determining optimal settling thrust, and controlling boil-off during the transfer process

. Successful development of this technology is essential for NASA's Artemis program and SpaceX's ambitious goals of making life multi-planetary