MECHANICAL CHARACTERIZATION OF DEPLOYABLE THIN SHELL CFRP BOOMS FOR THE CUBESAT “DE-ORBIT SAIL”

The risk for spacecraft in Low Earth orbit (LEO) to be hit or damaged is increasing due to a growing space debris population. Reduction and limitation of this risk is addressed by de-orbiting end-of-life maneuvers. To realize such a maneuver a drag augmentation device that increases the drag efficient surface of a satellite, acting with the residual atmosphere and accelerating the decay of orbit altitude until re-entry into Earth’s atmosphere, is necessary. Currently such a device is being flown with the CubeSat based drag sail satellite DeorbitSail by the University of Surrey, DLR, and other partners. The goal is to demonstrate the in-orbit deployment of a 4 m x 4 m drag sail, suitable for small and medium size satellites, as an end-of-life de-orbiting device. The device has a squared sail design utilizing 4 triangular membrane sail segments that are deployed and spanned out by thin shell CFRP (carbon fiber reinforced plastics) booms developed by DLR. The focus of this paper is on one of the main structures, the deployable thin shell CFRP-booms that are susceptible to buckling. Properties and characteristics of full scale booms regarding structural load capacities in all applicable load directions are being determined in a newly introduced vertical test stand. Thresholds and robustness for certain load cases like axial compression and lateral bending, and load carrying capabilities after buckling several times, are determined and quantified in practical testing, thus specifying the boom performance in reality. This is of high importance in order to be able to predict and design a robust drag sail structure, not failing due to overloading in space. This paper gives information of the applicable loading on the booms derived by the space application, the used test stand and equipment as well as the testing itself. Finally the acquired test results are analyzed and discussed