Speakers
Description
Background: Post-mission disposal is the final phase in the Life Cycle Assessment (LCA) of a spacecraft and is the yardstick used to evaluate the environmental impacts of disposal options on human health and the environment.
To date, the leading negative environmental impact identified (in the re-entry phase) is danger to human populations from surviving debris reaching the Earth’s surface. To minimise risk, regulations have been imposed on spacecraft to prove that the design process and re-entry plan hold a causality risk of less than 1 in 10,000. This requirement underpins the Design for Demise (D4D) philosophy that aims to limit the mass and size of debris falling back on Earth by designing spacecrafts that will burn up effectively during re-entry. D4D focuses on the difficult challenge of building a spacecraft that can both function and is demisable. But it does not study the environmental impact on the upper atmosphere from the particles and gases released during re-entry and burn up.
Discussions on this topic have been slow to begin as the space sector has viewed the problem to be trivial – supported by theoretical atmospheric modelling research – although ESA acknowledges that a lack of empirical research to inform the models makes the findings too uncertain to draw firm conclusions. Recently, metals from spacecraft were found in the upper atmosphere by climate scientists, that has fuelled debate on the magnitude of the problem. But D4D has benefits for managing space debris and argument are still in play on why studying the impact of atmospheric ablation on the upper atmosphere is neither a priority nor a good use of limited resources.
Focus: In this talk we outline the current state of knowledge on this complex topic – knowns, unknowns. unknown unknowns - based on an ongoing in-depth review of the complex phenomenon (funded by the UK space agency). Recently, in response to increasing concern over the potential impact of D4D on the upper atmosphere, a flurry of papers, newspaper articles, and social media blogs have appeared, many claiming a direct link between D4D and ozone depletion. But how rigorous and reliable is this body of knowledge?
