Propellant Depot - Cryogenic Depot Architectures and Types

Cryogenic Depot Architectures and Types

In the depot centric architecture, the depot is filled by tankers, and then the propellant is transferred to an upper stage prior to orbit insertion, similar to a gas station filled by tankers for autos. By using a depot, the launch vehicle size can be reduced and the flight rate increased. Since the accumulation of propellant may take many weeks to months, careful consideration must be given to boiloff mitigation.

In simple terms, a passive cryogenic depot is a transfer stage with stretched propellant tanks, additional insulation, and a sun shield. In one concept, hydrogen boiloff is also redirected to reduce or eliminate liquid oxygen boiloff and then used for attitude control, power, or reboost. An active cryogenic depot is a passive depot with additional power and refrigeration equipment/cryocoolers to reduce or eliminate propellant boiloff. Other active cryogenic depot concepts include electrically powered attitude control equipment to conserve fuel for the end payload.