DESIGN-FOR-DEMISE CONCEPTS WITH ADDITIVELY MANUFACTURED SATELLITE PARTS

Kurzfassung

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, a design philosophy called "Design for Demise (D4D)" seeks to reduce the amount of debris reaching the ground as much as possible. This work explores how additive manufacturing can be used for D4D, primarily through its freedom of form, but also by influencing material behaviour. The overall aim is to use additive manufacturing to create satellite designs where the primary structure breaks apart on re-entry at high altitude. Previous research has shown that the longer exposure of subsystems that can be achieved in this way can significantly reduce the amount of debris that reaches the Earth’s surface. In the course of this work, first, the theoretical foundations on which the work is based are summarised. Then a preliminary investigation is carried out, which examines the re-entry conditions, selects a suitable design material and presents preliminary satellite designs. Subsequently, the selected material CF30-PEEK is 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 affects them. In the next step, the designs are examined with ANSYS for their stability, iteratively adjusted and finalised in order for the structure of the satellite to be able to bear the loads occurring during launch. Finally, re-entry simulations are performed with ESA DRAMA for the finalised designs to determine the altitude at which the primary structure of the satellite will fail and break apart. The designs are scaled up to also be able to give break-up estimates for satellites of different sizes. It was shown that a failure of the primary structure occured 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.