SpaceX to demonstrate Starship's in-orbit refueling in 2025 according to NASA

image credit SpaceX

According to a recent report, NASA has laid out SpaceX's plan for an in-orbit refueling demonstration of Starship. SpaceX has already conducted successful test transferring liquid oxygen between tanks inside a Starship during a test flight, under a NASA Tipping Point contract.

Amit Kshatriya, NASA's Deputy Associate Administrator for the Moon to Mars Program, has officially confirmed the success of SpaceX's in-flight propellant transfer demonstration. This pivotal test involved the transfer of cryogenic propellants between tanks on Starship during the recent orbital test flight 3.

"On Flight 3, they did an intertank transfer of cryogens, which was successful by all accounts," Kshatriya remarked. He also highlighted the ongoing analysis of the test and the critical importance of understanding slosh dynamics and maintaining ullage—the space at the top of a tank that allows for the expansion of the liquid.

The next major milestone is the actual in-orbit refueling demonstration planned for 2025. This will involve a series of complex operations, including managing the slosh dynamics of the propellants and ensuring the correct amount of settling thrust is applied to facilitate the transfer.

Refueling spacecraft in orbit is a complex challenge that involves transferring volatile cryogenic propellants in microgravity conditions. For SpaceX's Starship, which is designed for missions to the Moon and Mars, mastering this technique is essential. The ability to refuel in space would enable longer missions, reduce launch costs, and potentially allow for the reuse of spacecraft.
The Five-Step Technical Process to refuel the Starship in low Earth orbit will be as follow -

1. Orbital Mechanics : The journey begins with the launch of the 'target' Starship into a carefully calculated orbit. After a waiting period of three to four weeks, the "chaser" Starship embarks on its mission to rendezvous with its counterpart.
  
2. Docking Maneuver : In the vastness of space, the chaser Starship performs a sophisticated docking maneuver. This critical step involves aligning and connecting with the target Starship in a belly-to-belly configuration, setting the stage for the next phase.

3. Propellant Transfer : The core objective of this operation is to transfer a substantial amount of liquid oxygen—no less than 10 metric tons—from the header tank to the main tank within the upper stage of the Starship.

4. Slosh Dynamics : One of the most significant challenges is managing the slosh dynamics of the propellants. As the Starship maneuvers in orbit, engineers must maintain precise control to prevent any destabilization.

5. Settling Thrust : Once the Starships are securely docked, engineers apply a calculated amount of settling thrust. This ensures that the propellant flows smoothly between the two colossal spacecraft.

Implications for Artemis and Beyond

The success of SpaceX's refueling technology is pivotal for NASA's Artemis program, which aims to return humans to the lunar surface. With a scheduled lunar landing in 2026, SpaceX's Starship is one of the contenders for transporting astronauts to the Moon using Human Landing System (HLS) version of Starship . Beyond Artemis, in-space refueling could revolutionize the way we approach space travel, making it more akin to refueling a car on a long journey rather than the current one-way trips.