An aerostable drag-sail device for the deorbit and disposal of sub-tonne, low earth orbit spacecraft

There is an increasing amount of debris in low Earth orbit arising from the disintegration and collision of old spacecraft which have not been removed from orbit. A ‘bolt-on’ deorbit device to be attached to new spacecraft is therefore proposed, which would deploy an aerostable drag sail at end-of-life. This drag sail would interact with the rarefied atmospheric gases and plasma present at altitudes of up to 1,000 km and thus denude energy from the orbit, causing it to become lower and lower until final re-entry of the host becomes inevitable. At this point the drag sail would collapse and both the host and the deorbit device would be destroyed by aerothermodynamic forces. This work develops the deorbit device concept by demonstrating that aerostable drag enhancement is an effective and competitive deorbit mechanism. This is done by: • Calculating the aerodynamic, solar radiation pressure and gravitational influences on the deployed drag sail and using them to model the performance of the device. • Using the results of that modelling to identify the optimum shape, size and deployment conditions of the drag sail. • Further calculating the structural strength required to resist the aerodynamic loads until the desired collapse altitude. • And finally by using that information to assemble a conceptual design which demonstrates the practicability of the system.