Speaker
Description
Previous D4D studies at system level have clearly shown that, in order to reduce the risk posed by re-entering satellites, an integrated approach to design for demise is more efficient or, for large satellites, even required. Re-entry simulations demonstrated that solutions at component or equipment level might not be enough to effectively reduce the re-entry casualty risk, and that a system-level approach is almost invariably better, or even necessary. The early break-up of the spacecraft main structure (in particular if adopted in combination with re-designed critical elements), or the early separation of critical payloads, can improve the overall demisability, significantly reducing the casualty risk on ground.
The solution presented here is the innovative system, referred to as Demisable Joint (covered by the TAS-I patent N.TO2014A000998.), based on a standard Aluminium joint in which two modifications are implemented:
• one of the aluminium cleats is modified introducing an opening,
• a washer, made of a material with low melting point, is adopted replacing standard aluminium washer.
During the operative life the elements are kept together by the force exerted by the screw, but during re-entry, when the demisable washers demise, the two elements of the joint are free to slide transversally w.r.t. the screw axial direction. Therefore, due to the mechanical loads experienced during re-entry, they will separate. The detailed re-entry simulations performed, showed that replacing current joints for connecting S/C external panels with this re-designed joints will cause the S/C to break up at an altitude higher w.r.t. the one achieved with current joints design.
The main advantages and the novelty of the solution proposed are the extreme simplicity of its design, that consists is a minor, but crucial, modification of S/C current joints, with very low system level impacts and very low cost. The Demisable Joint can be implemented in current satellites without need of modifying the current overall S/C design, manufacturing and integration process.
In conclusion, the Demisable Joint is a simple solution which, if proved effective by test, could be largely applied to future satellites.
