Draper labs has developed a way to use less fuel to maneuver objects in orbit. This was tested on Aug 1st using no less than the International Space Station during a routine docking mission with a Russian Progress resupply ship. It usually takes about 300 kilograms of propellant to change orbit and rotate the station so that docking can occur at the pre-designated docking orbit. With this new approach, known as the Optimal Propellant Maneuver (OPM), the same orientation of the station was achieved using only 20 kilograms of propellant. This approach can be used for all satellites in low Earth orbit, thus allowing for greater operational life of currently operating satellites and a decreased launch cost of future satellites due to those satellites requiring less fuel on launch.
The OPM is an improvement on the ZPM, or Zero Propellant Maneuver which was also developed by Draper labs. The ZPM underwent testing because it could rotate the stations orientation using only the stabilization and control gyroscopes, thus using no fuel. Once the proper orientation was achieved, thrusters would fire to change the orbit of the station. Unfortunately, The ZPM maneuvers were very slow and caused minor thermal problems due to the slow change of orientation. Then, the necessary thruster firings would use a large amount of fuel and put an increased strain from the force of the thruster firings. The path for the thruster firings was the most direct along the Eigen axis but this does not mean that it is the most efficient path to take. There are certain disturbances that the OPM can take advantage of during a maneuver. Aerodynamic drag is one of these disturbances and while there is not much atmosphere is low Earth orbit, there is enough to eventually de-orbit all low Earth orbit satellites. By changing the orientation of the station or satellite, this drag can be used to change the orbit while only using minimal propellant.
This new approach was a international cooperation from the U.S., Europe, and Russia. The U.S. guidance computers coordinated the firing of thrusters on the E.S.A. automated transfer vehicle that docked to the station in March and the Russian flight software controlled the actual firing of the thrusters according to the plan developed by the U.S. based Draper labs. This new maneuver didn’t require any changes to the flight software, the maneuvers were simply entered into the existing software for execution. This means that most likely existing software on other satellites will immediately be able to benefit from this type of maneuver without having to modify anything on the satellite. This international cooperation is a prime example of how the I.S.S. is being used to advance spaceflight by providing a test bed for new technologies that were not even thought of when planning of the I.S.S was under way.