Northrop Grumman's Passive Refueling Module (PRM) has been selected as the preferred model by the U.S. Space Force to develop in-orbit satellite refueling standards for the Space Force's Space Systems Command (SSC) to extend the mission life of satellites.
The cost of building a satellite and putting it into orbit is eye-watering. Therefore, engineers work hard to make these space machines last as long as possible. However, there is one limiting factor that is almost impossible to get around: the need for propellant.
Most satellites are not passive objects orbiting the Earth. They need to maintain a certain attitude so that their solar panels are pointed toward the sun and their communications antennas toward the Earth, and to avoid rolling over. Many satellites also need to adjust their orbits to enter new orbits or to offset the effects of orbital decay.
Unfortunately, all of this consumes propellant, and after a few years, the multimillion-dollar spacecraft will be as useless as a chocolate teapot.
To avoid this, Northrop Grumman and others have been developing on-orbit servicing modules. These robotic spacecraft can dock with satellites that are running out of fuel, breathing new life into the satellite by acting as a supplemental propulsion system, providing additional functionality (such as a new power source) or even performing minor repairs.
This is very attractive to the Space Force because of its high propulsion requirements for military satellites. These assets need to be able to change orbit frequently to survey a specific point on the Earth's surface, investigate another spacecraft, or evade a threat. Even if these maneuvers are used only during exercises, their propulsion is very expensive.
Being able to refuel is an obvious solution, but the problem is that developing such technology requires a lot of standardization work to ensure that these systems are compatible with the refueling systems of visiting satellites. Otherwise, a scenario we are all too familiar with will occur: going to charge a smartphone, only to find that you brought the wrong charging cable.
This is not a new problem. Space agencies have been dealing with standardization issues for more than half a century -- ever since the United States and the Soviet Union had to develop a common docking mechanism for the 1975 Soyuz Apollo mission, in which the Soyuz Apollo command module had to dock with the Soyuz spacecraft.
As far as the Space Force and Northrop Grumman are concerned, the plan is to develop a common refueling system based on the PRM, a passive refueling station that SSC satellites can dock with. This means that future SSC spacecraft will be equipped with interfaces compatible with the PRM, which will be orbitally tested on future operational missions.
SSC also funds Northrop Grumman's development of the Geostationary Auxiliary Support (GAS-T) orbital tanker.
Rob Hauge, president of Northrop Grumman's Space Logistics Division, said: "In an increasingly competitive and crowded space sector, on-orbit refueling will allow spacecraft to continue maneuvering to respond to threats, avoid debris and extend satellite life. As the first and only company to successfully provide commercial on-orbit servicing missions in geosynchronous orbit, we will continue to work with SSC and other government customers to mature in-orbit refueling capabilities."