Miniature thruster propels single cubesat to lower orbit

by

This article was updated and corrected on Aug. 22 at 3:30 pm Eastern time with information on the cubesat propulsion system.

SAN FRANCISCO – Germany’s University of Wurzburg Experimental-4 (UWE-4) cubesat avoided a potential collision in early July while lowering its altitude with a NanoFEEP electric propulsion system from Technical University of Dresden.

It was the first time a one-unit cubesat performed a collision-avoidance maneuver, said Istvan Lorincz, Morpheus president and co-founder, whose firm is working to find commercial applications for similar thrustersMorpheus co-founder Daniel Bock was one of three inventors who patented the electric propulsion technology while studying at the Technical University of Dresden.

The growing popularity of small satellites is prompting companies around the world to develop miniature thrusters to help cubesats avoid collisions, change altitudes, fly in formation and leave orbit when their missions conclude.

From June 23 to July 3, the UWE-4 cubesat fired its NanoFEEP thrusters several times to reduce its altitude by more than 100 meters. By comparison, natural orbital decay would lower the altitude 21 meters in the same timeframe, according to a University of Wuerzburg news release.

One July 2, as the UWE-4 cubesat was lowering its altitude, the University received a warning from the U.S. Air Force’s 18th Space Control Squadron of a July 5 conjunction with a retired Iridium satellite.

When UWE-4 mission operations personnel analyzed the conjunction, they determined the UWE-4 cubesat would not collide with the Iridium satellite because it would be orbiting at a lower altitude. As a result of the analysis, UWE-4 mission operations personnel continued firing thrusters to lower the cubesat’s altitude. They received no further conjunction messages.

The UWE-4 cubesat includes four NanoFEEP thrusters housed in its rails launched in late 2018. One of the thrusters worked properly, one thruster worked intermittently and two failed to work, Klaus Schilling, University of Wurzburg professor of robotics and telematics, said by email. The 160-gram NanoFEEP developed by the Technical University of Dresden combines a liquid gallium propellant with a chip-based neutralizer.

“In his doctoral thesis, however, Alexander Kramer made very clever use of the control system actuators available, the remaining one electric thruster and six magnetorquers for relative orientation with respect to the Earth’s magnetic field, to perform all the planned maneuvers,” Schilling added.

The UWE-4 program, funded by the German space agency DLR, is focused on developing technologies for formation flight of cubesats.