Satellites are very expensive to build and put into orbit, and engineers work to ensure they last as long as possible. But there is a limiting factor: the need for fuel.

Most satellites are passive objects orbiting the Earth. They need to maintain a location where solar panels are pointed toward the Sun and communications antennas are pointed toward the Earth. Many satellites also need to be able to adjust their orbits to move to a new orbit or counteract the effects of orbital perturbation.

All these activities require fuel, because after a few years a multimillion-dollar spacecraft that is still in excellent condition becomes unusable. To prevent this, Northrop Grumman is developing in-orbit service modules. These robotic spacecraft have the ability to dock with satellites that have run out of fuel, act as an additional propulsion system, provide additional capabilities such as a new power source, or perform minor repairs.

This is necessary for US space forces because their military satellites place special emphasis on movement activities. These vehicles must be able to change orbit frequently to explore a specific spot on Earth, discover another spacecraft, or escape a threat.

The ability to refuel is an obvious solution, but the problem is that the evolution of the technology requires significant standardization to ensure systems are compatible with refueling satellites.

The U.S. Space Force and Northrop Grumman are developing a joint refueling system based on the PRM, a passive refueling station where SSC satellites can dock. This means that future SSC spacecraft will be equipped with a PRM-compatible interface.