Cross-feeding propellant between stacked spacecraft

A system comprising:

• at least two spacecraft, including at least a first spacecraft and a second spacecraft, the at least two spacecraft disposed together, in a launch configuration, for launch by a single launch vehicle;
• wherein:
• in the launch configuration, the first spacecraft is mechanically coupled with a primary payload adapter of the launch vehicle, and the second spacecraft is mechanically coupled with the first spacecraft by way of an inter-spacecraft coupling arrangement;
• the system is configured to be deployed, following injection into a first orbit by the launch vehicle, by separating the first spacecraft from the primary payload adapter while the second spacecraft is mechanically coupled with the first spacecraft;
• the first spacecraft includes a first onboard propulsion subsystem including a first propellant storage arrangement;
• the second spacecraft includes a second onboard propulsion subsystem including a second propellant storage arrangement;
• the first onboard propulsion subsystem includes one or more thrusters configured to execute an orbit transfer maneuver from the first orbit to a second orbit;
• and
• the system includes a propellant line arrangement that detachably couples the first propellant storage arrangement with the second propellant storage arrangement.