To decrease de-orbit time and allow for higher-altitude orbits of small satellites, researchers at NASA and the University of Florida have developed a retractable drag device capable of modulating drag area while providing 3-axis stabilization. The device increases area without increasing mass, increasing the ability to control rotation and attitude in 12U, 15-kg CubeSats and other small satellites.
This retractable de-orbiting device integrates into the rear of existing small satellites to decrease de-orbit time and allow for higher-altitude launches. Decades of launches have left Earth surrounded by a halo of space junk, especially in the orbits typically inhabited by small satellites, which are relegated to lower orbits because of their limited lifetime. Space debris, ranging from objects the size of a coffee cup to multi-ton derelict satellites, is a collision risk. To reduce space debris, NASA requires small satellites to de-orbit within 25 years; to do so, the spacecraft rely on atmospheric drag, which reduces velocity and decreases altitude until the satellite burns up in the atmosphere.
This system acts as a self-contained device, integrating four booms that can be extended and retracted in a manner similar to that of a tape measure to control the drag area of a small satellite and facilitate orbital maneuvering. The dart configuration of the booms places the satellite's center of pressure behind the center of mass, providing passive aerodynamic stability akin to that of a flying arrow. Actuating each boom independently provides redundancy and facilitates differential boom deployment for gravity gradient stabilization. Differential boom deployment can also create a clear minimum moment of inertia axis, which results in a preferred rotation direction, stabilizing the attitude.
This aerodynamic and gravity gradient stability, coupled with attitude damping from magnetorquers embedded in the device, provides 3-axis attitude stabilization. This device could replace conventional thrusters and attitude control systems for many missions, reducing costs and increasing reliability. Furthermore, the device can enable controlled re-entry to a specific longitude and latitude above the surface of the Earth, allowing the device to avoid inhabited areas.