Satellites using superconducting rings that generate electromagnetic fields (EMF) could use the shear torque from the EMF to station-keep in formation in orbit.

It would mean spacecraft would no longer have to carry propellant or heavy thrusters to maintain attitude and position. However, the spacecraft would need a reaction wheel to counteract unwanted shear torque.

A technology testbed has been built by researchers at Massachusetts Institute of Technology’s department of aeronautics and astronautics and the team is developing the control algorithms for the EMF and reaction wheel system.

EMF solutions for station keeping would be uploaded to the satellite if necessary to adjust for environmental and spacecraft change during the course of the formation’s operational life.

The spacecraft’s superconducting rings would be energised by the solar panels. The rings would generate dipole fields, which have torque and angular momentum.

To move the spacecraft 90° on its axis, for example, the angular momentum is needed; but where the momentum of another ring’s dipole is not helpful, the reaction wheel would absorb that energy.

Because the wheels can only absorb so much angular momentum, the Earth’s EMF could be used as a receptacle.

Source: Flight International