We have known that fuel transfer capability is critical for the $3.5 NASA-SpaceX Lunar Starship program. SpaceX will test as much as they can in the single Starship launches as previously discussed by NASA. SpaceX will have to progress as quickly as possible with monthly or more frequeent Starship launches and tests ASAP to get close to the NASA lunar Starship schedule.

Lakiesha Hawkins, deputy associate administrator for NASA's Moon to Mars program office, one of her slides (at a Congressional Committee presentation) in 2023 said SpaceX is moving quickly toward various propellant transfer demonstrations.

Cutaway diagram was by Tom Dixon

SpaceX Has a $52 million cryogenic fluid management NASA Tipping point award.

This test would involve transferring super-cold propellant from one tank to another inside a Starship spacecraft. It's a precursor to future, more complex demonstrations involving two giant Starships docked together in Earth orbit. Then SpaceX will be ready to send a Starship toward the Moon for a test landing without astronauts onboard.

The demonstration will include technology risk assessment, design and prototype testing, and in-orbit demonstration. It will also provide insights for larger vehicle-to-vehicle transfers, which is a key capability for SpaceX's lunar lander.

This is a critical capability to enable the landing on the moon with SpaceX Lunar Starship.