A reusable module is affixed atop a reusable orbital vehicle (OV). Various configurations of the reusable module have identical external dimensions in the region of attachment to the OV to permit interchangeability. Different configurations can accommodate a variety of missions of different type and duration. A variety of cargo modules of different configurations allow cargo to be uplifted into orbit. In one embodiment, the cargo module is an unpressurized cargo module in which the cargo is exposed to the environment of space during the unloading process. The cargo module may also be a pressurized cargo module. In an alternative embodiment, the cargo module may include both a pressurized cargo module and unpressurized cargo module.