Speaker
Description
To ensure that near-Earth space remains commercially and scientifically viable in the future, it is of great importance to reduce the amount of space debris in orbit and minimise the generation of new debris. Major space actors such as ESA and NASA have issued guidelines for reducing space debris. An important part of this is the removal of discarded rocket stages and satellites from orbit. One of the cheapest and easiest methods of removal is uncontrolled re-entry into the Earth’s atmosphere with the aim of burning up the hardware. To ensure that the risk of such re-entring debris endangering humans on Earth is minimised, the design philosophy "Design for Demise (D4D)" seeks to reduce the amount of debris reaching the ground as much as possible.
This work explored how additive manufacturing can be used for D4D, primarily through its freedom of form, but also by influencing material behaviour. The overall aim was to use additive manufacturing to create demisable designs for joining primary structures, where it breaks apart on re-entry at higher altitudes than it would normally do. Previous research has shown that the longer high enthalpy flow exposure of subsystems that can be achieved in this way can significantly reduce the amount of debris that reaches the Earth’s surface.
Two concepts were investigated in this study; a patch concept and an insert concept. First, a preliminary investigation was carried out, in which the re-entry conditions were examined, a suitable design material was selected and preliminary satellite designs were proposed based on an existing satellite mission. Subsequently, the selected material CF30-PEEK was subjected to a mechanical and thermal characterisation in order to have suitable material parameters available for the subsequent simulations and to investigate how additive manufacturing may affect them. In the next step, the designs were examined by Finite Element Analysis for their stability, iteratively adjusted, optimised and finalised in order for the structure of the satellite to be able to bear the loads occurring during launch. Finally, re-entry simulations were performed with ESA DRAMA for the finalised designs to determine the altitude at which the primary structure of the satellite is expected to fail and break apart. In the process the satellite models were scaled up to give break-up estimates for satellites of different sizes when implementing the proposed designs. It was shown that a failure of the primary structure occurred above 97 km for all designs and satellite sizes up to a maximum investigated satellite mass of 4000 kg, and even a maximum break-up altitude of 107 km was reached. The targeted exploitation of the freedom of form of additive manufacturing played a decisive role in the development of the designs.
