DESIGN-FOR-DEMISE CONCEPTS WITH ADDITIVELY MANUFACTURED SATELLITE PARTS

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

ADDITIVE MANUFACTURING FOR D4D: THERMOPLASTIC DEMISABLE JOINTS FOR HIGH ALTITUDE BREAK-UP

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 minimize the generation of new debris. At DLR Institute of Structures and Design in Stuttgart, we explore how additive manufacturing can be used for "Design for Demise (D4D)", primarily through its freedom of form, but also by influencing material behavior for a more efficient demise process. The overall aim was to use additive manufacturing to create demisable designs for joining primary structures, where it breaks apart during re-entry at higher altitudes than it would normally do. Demisable joint concepts made of 3D printed CF-PEEK were developed and later upgraded with passive ejection mechanisms using preloaded springs and shape memory materials. Thermomechanical analyses and successful preliminary plasma wind tunnel tests are presented

In-situ manufactured landing pads and berms to enable sustainable operations on the lunar surface

One huge challenge for sustainable lunar operations are the potential adverse effects on surface infrastructure caused by regolith particles, covering the lunar surface. Due to the lack of atmosphere, these particles are not affected by weathering and remain sharp and jagged. Thus, they can damage lander and/or ascend vehicles whose engine exhaust plumes swirl up dust particles. Furthermore, the low gravity environment and the lack of atmosphere do not decelerate the particles as much as on Earth. Therefore, they stay above the surface longer and can travel at higher velocities across larger distances than they would on Earth. This results in risks also for other infrastructure on the moon, such as antennas or solar panels. Electrostatic forces are an additional potential problem, particularly for future crewed missions with high cleanliness requirements. Consequently, to enable sustainable exploration of the Moon, the risk of lunar regolith particles needs to be managed. But already for missions planned for the near future, such as the European lunar lander of ESA’s Argonaut project, the challenge of plume/regolith interaction needs to be tackled. One potential solution is the construction of lunar landing pads, which minimises liberation of loose regolith particles, and berms, which minimise the resulting effects of the remaining regolith particles. Such structures can potentially be realised with in-situ manufacturing techniques, which already show promising results. Manufacturable structures can be similar in their material properties to a variety of materials like concrete, technical ceramics or glass with melting temperatures above 1300~K, depending on the regolith composition. Within the LUNAR ISLANDS (LUNAR In-Situ LANDing Structures) activity, funded by the European Space Agency, an international consortium led by TU Dresden is assessing the effectiveness of in-situ manufactured structures on the containment of high-velocity particles that are generated by the plume-surface interaction of landers. This involves the manufacturing and characterisation of samples from lunar regolith simulants, experimental investigations in the form of cold gas and hot fire tests as well as numerical simulations of the interaction of exhaust plumes and lunar regolith. This contribution provides an overview of the activity, its objectives and work plan, and presents initial results of the first part of the activity. This comprises the driving parameters and requirements for lunar landing pads and berms, which have been derived from numerical simulations in combination with an in-depth analysis of the state of the art