Starship Propellant Transfer Demonstration

This article is about the propellant transfer demo between Starship vehicles. For the initial propellant transfer demo between tanks on a single vehicle, see Starship flight test 3.

The Starship Propellant Transfer Demo is expected to occur in 2026.^[1] A similar test occurred during Starship's third test flight, though the transfer during that test was between two tanks on the same vehicle.^[2] The ability to refuel a Starship in low orbit is critical for the Artemis program,^[3] as Starship HLS requires approximately ten tanker launches to reach the lunar surface.^[1]

Starship Propellant Transfer Demo

Mission type	Flight test
Operator	SpaceX
Spacecraft properties
Spacecraft type	Starship
Manufacturer	SpaceX
Start of mission
Launch date	NET 2026
Rocket	Super Heavy
Launch site	Starbase, OLP-A or OLP-B
Orbital parameters
Regime	Low Earth orbit
Payload
Liquid Methane (CH4), Liquid Oxygen (LOX)
SpaceX Starship flight tests ← Flight 10

Mission profile

The mission profile for the Starship Propellant Transfer Demo will begin with the first launch. This launch will deliver the upper stage into orbit around the earth, while the first stage returns to the launch site for a catch. The second launch will repeat this profile three to four weeks later, and dock with the first Starship.^[4] Once docked, the vehicles will use a pressure differential between them to force propellant from the second vehicle into the first.^[1] After this is complete, the two ships will undock, reenter, and be caught.^[1]

Payload

The second launch in the propellant transfer will fly an unknown amount of propellant as its payload.^[1] In order to prevent the propellant from boiling during the vehicle's time in orbit, significant insulation and vacuum jacketing will be added to the propellant lines inside the vehicle.^[1] This change was introduced on the first Block 2 vehicle, S33.^[5]