FULL SCALE FLAT FLOOR TESTING OF A 500-M²-CLASS SOLAR SAIL DEPLOYER

Kurzfassung

Solar sailing missions rely on deployable systems for large area to mass ratios once in space, while still being small enough for launcher envelopes in the stowed configuration. Many of these deployable systems feature booms that are flattened and subsequently coiled onto a spool/hub. As part of a collaborative deployable space structures research effort of NASA and DLR, a boom deployment mechanism for a future 500 m² solar sail has been developed since 2017. To achieve the respective solar sail size goal, 16.5 m long booms produced by NASA were integrated into a DLR-designed deployer. This considerable size, as well as the lightweight construction of the booms and respective deployable systems makes ground testing a significant challenge. Some systems for gravity compensation and boom alignment will be presented in the paper. However, the main focus is the functional flat floor testing of the integrated boom-deployment mechanism system, as well as its challenges. The testing performed includes full deployment as well as stowage of the booms. Both have been performed multiple times. The latter is one of the key parameters determining packaging efficiency, which in turn confirms design assumptions. During system development, small scale tests and models have been used in preparation of flat floor testing of the 33 m span cross of the full-scale booms and deployment mechanism. Hence a small chapter is also devoted to analysing the differences in behaviour between small- and full-scale deployment systems. More parameters that are vital to design decisions have been determined this way, such as driving belt force or hub brake torque. This paper also focuses on development goals and needs for future steps to achieve higher levels of technology readiness, such as the balancing of driving motor force, synchronisation of its transmission and the countering hub brake torque.