Lunar EVA Emergency Pressurization (LEEP) Shelter: Concept Design Using a Systems Engineering Approach

The European Space Agency has a vision for a collaborative multi-national village to establish a long-term human settlement on the Moon, building on the legacy established by ISS operations. Medical planning and life support considerations for the Moon Village need to address routine operations, special scenarios (e.g. higher risk activities) and emergencies. Within this planning life support systems will be designed with in-built redundancy and back-up options and, typically, also the safety net of a separate emergency system. The aim of this study was to assess the engineering considerations and medical requirements and to design a potential solution for one such emergency life support system; that required for emergency pressurization in the event of spacesuit failure during Extra-Vehicular Activity (EVA) on the Lunar surface.

The system was designed using a Model-Based Systems Engineering (MBSE) approach; beginning with the business justification, formal requirements engineering, and an architecture trade-off to develop behavioral and structural models. Each major subsystem was then considered including physiological requirements, environmental control, thermal control, power supply, and structures and mechanisms. The subsystems were then combined into a comprehensive system, with some consideration for recovery methods.

The proposed LEEP shelter design has mass of 63 kg (equivalent to ~10.5 kg on lunar surface). It would be capable of deployment and pressurization in 60 seconds creating a 5 m3 volume, sufficient for two astronauts in EVA suits. It would be pressurized to 29.8 kPa with 100% oxygen from a compressed gas cylinder with subsequent atmospheric recycling using rapid cycle amine technology to remove CO2. Internal temperature would be controlled between 283-316 K using convection heating and/or vapor sublimation. Power is from a 730 Wh battery to support 28W operation up to 26 hours. Further consideration has been given to system implications for likely medical complications and potential recovery methods.