Eco-Design of future reusable launchers: insight into their life cycle and atmospheric impact

Abstract

Reusable launch vehicles (RLV) are slowly emerging as a solution to reduce space access costs, bringing potential benefits from novel breakthrough space application. Whilst space presents an ideal platform for addressing global issues, it raises an "adaptation-mitigation dilemma". Launch vehicles are the only anthropogenic object emitting directly into every layer of the atmosphere, and reusability may introduce additional burdens. Although it may ensure a rational use of materials through the recycling of major components, its potential sustainability gains with respect to equivalent expendable launch vehicles (ELV) has not been quantified. The correct understanding of these are therefore critical to ensure sustainable design choices for space transportation. This study reviews current state of knowledge on launchers environmental impact and eco-design before introducing a preliminary life cycle and atmospheric impact assessment of the different technologies for first stage reusabiltiy. Reusabiltiy showed possible early reductions in material resource depletion which was independent of propellant choice and recovery strategies. In terms of climate forcing, reusability was only beneficial when fully carbon neutral propellant production was assumed for hydrolox, ammolox technologies, and possibly for methalox if soot production is kept under sustainable limits. VTHL performing In-Air-Capturing recoveries also showed reduced climate forcing potential. Stratospheric ozone depletion potential was estimated to increase by 18-34 % for VTVL vehicles, and 12-16% for VTHL with respect to ELV. In addition, high sensitivity with mixture ratios, flight profiles, staging condi- tions and aerodynamic capabilities was identified, which require detailed assessments with higher fidelity design methods. Future launch impacts from large scale space activities were also estimated to no longer be negligible, although some margin for mitigation exists among the various design options, and recent regulatory developments internalizing climate change costs might significantly affect the business case of RLVs. In addition, high altitude atmospheric impacts, particularly those from soot emissions, appear to dominate the potential life cycle impact and uncertainty, especially for hydrocarbon fuelled launch vehicles. This is further exacerbated by the commonly used but unsuitable weighting based on aviation and ground based emissions. These might affect the absolute and relative comparisons significantly and therefore, results from this study must be taken with caution. Future studies should employ state of art atmospheric modelling and adequate approaches to weight the various life cycle impacts, enabling design for mitigation while avoiding burden shifts.