The UnPressurized Cargo (UPC) is the use of available area in the Orion Service Module (SM) by the Explorations Systems Project at NASA’s Goddard Space Flight Center. The overall objective of the study was to determine the feasibility of utilizing Orion’s SM-UPC capability for the ISS Design Reference Mission for scientific and technology type payloads, and the required interface accommodations to the SM. This capability, collectively referred to as UPC Exploration Carriers, accommodates two modes of UPC payload operations, Free-Flyer and Attached Payloads.

Supporting the Free-Flyer study, the NMDB provided analysis for both chemical and low-thrust propulsion systems that allowed mission design to LEO, GEO, Elliptical orbits, and also lunar and libration orbits. Trajectory design analysis was performed to provide data for both the feasibility of such missions as well as for the system engineering design parameters (fuel, mass, communication and tracking, power, etc). Several mission types were investigated and by using a low-thrust system similar to the ESA Smart-1 program, a lunar mission was found to be achievable. Trades were performed and a Mission Design Lab (MDL) study was supported to find a preliminary design. Analysis covered the LEO considerations of orbit maintenance and orbits achievable based on Delta-V (DV) and fuel volume requirements. The lunar mission (and libration orbit mission) used advanced approaches of gravity assist to a near Earth weak stability boundary transfer to minimize the required DV for lunar orbit insertion. The Free-Flyer consists of a small sub-satellite that is deployed (ejected) from the SM into ISS LEO orbit (~400km at 51.6°) and is completely independent of Orion. The GSFC mission design team conducted a point design for a Lunar Orbiter as a bounding case, capable of carrying a 50 kg payload injected into a stable lunar orbit with a mission life of 2-3 yrs on station. A Solar Electric Propulsion system was selected over a chemical system in order to maximize payload mass. However, chemical propulsion is a better option for LEO type orbits and offers a payload mass of approximately 100 kg in ISS inclination and altitude with an estimated mission life of 5 years.