This may be counterintuitive, but designing satellites that can “better fall” is one of the key strategies for combating space debris. Developed by the European Space Agency’s Clean Space Initiative, this approach is called “design for demise” and involves making sure that abandoned satellites completely fail and burn up when they re-enter the atmosphere.
Space re-entry devices must burn out completely over the course of an atmospheric immersion to be safe, but in practice, some pieces can currently reach Earth, and some are large enough to cause serious damage. As part of a larger effort called cleansat, the European Space Agency is developing technologies and techniques to ensure that future low-orbit satellites are designed according to the “D4D” concept – design for demise.
Some of the heavier satellite components are more likely to survive the re-entry process. One element of D4D’s research concerns the incorporation of such massive objects within plasmonic wind tunnels that are capable of reproducing atmospheric re-entry conditions. Another is to plan ways to ensure the early collapse of the return wreckage.
During re-entry, extreme heat flows and mechanical loads usually cause the satellite to rupture at an altitude of about 75 km. Only after this height, most of the indoor equipment exposed to heat flow will also begin to break down, but the higher breaking height design means that the indoor equipment will be exposed to heat flow for a longer time, which greatly improves its destruction. Possible ways to ensure this include multiple fusible links that hold satellite panels together or the use of “shape memory alloys” that change shape with temperature.
Clean Space also uses DRAMA (Debris Risk Assessment and Mitigation Analysis) software to calculate the compliance of a given satellite project with space debris mitigation standards and to ensure that the latest research findings are considered, with the goal always of minimizing the risk of casualties below critical ones. With a value of 1 in 10,000.
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