Drag Sail Development for End-of-Life Deorbit
- Paper number
IAC-08.A6.4.7
- Author
Dr. Peter Roberts, Cranfield University, United Kingdom
- Coauthor
Dr. Stephen Hobbs, Cranfield University, United Kingdom
- Coauthor
Dr. Jenny Kingston, Cranfield University, United Kingdom
- Coauthor
Dr. Ben Graziano, Cranfield University, United Kingdom
- Coauthor
Dr. Patrick Harkness, Cranfield University, United Kingdom
- Year
2008
- Abstract
Current international guidelines require that, at the end of their operational lives, spacecraft be removed from orbit within a maximum of 25 years. This paper considers ongoing work at Cranfield University to develop deployable, aerodynamically stable drag enhancement structures for the end-of-life disposal of low earth orbit spacecraft. Such a device could be deployed regardless of pointing or health of the parent satellite, and significantly reduce the orbital lifetime of the system. Whilst the area-time-product swept by the deorbiting satellite is not significantly reduced, the reduced fragmentation risk resulting from debris collisions with the spacecraft are significant. Altering the sail geometry to maximise the coefficient of drag whilst minimally increasing the drag cross-section is also considered. Finally, plans for a cubesat demonstrator of the concept are discussed. Previous published work at Cranfield has focused on the optimisation of the sail shape to minimise the orbital lifetime of sub-tonne satellites in low Earth orbits whilst also minimising the mass of the deployable device. The optimum is a nearly flat conical or pyramidal sail which benefits from restoring aerodynamic forces which turn the sail into the flow. A summary of the results of this study will be included in the paper. Other unpublished work has focussed on the development of a tool to calculate the aerodynamic surface forces on arbitrary geometries in the orbital free molecular flow regime. This allows more complex geometries to be considered along with different gas surface interaction models. The development of geometries which maximise the coefficient of drag are therefore considered which also reduces the area-time-product. The cubesat demonstration mission is designed to carry a small drag sail demonstrator, triggered by a telecommand, with Nytinol wire struts and Mylar sail material. This will increase the drag area by at least a factor of ten with a similar subsequent reduction in orbital lifetime following deployment. In conclusion, drag sails represent an end-of-life deorbit solution for LEO spacecraft with benefits over tether deployment and deorbit burns, both of which require stable pointing, and therefore represents a robust viable option. Discussion points surround the area-time-product of the satellite which is not significantly reduced with the proposed method, but is not the only metric that should be considered.
- Abstract document
- Manuscript document
(absent)