Life support systems

Abstract

Basic human needs-a breathable atmosphere, water, food, and waste removal- are all natural life support functions and in normal life they are basically provided by our planet’s ecological system. These basic needs are the same for humans in space as on Earth, but nature must be copied by mechanical and physicochemical equipment. In particular, the limited volume and the very high cost of transportation require the application of individual weight, volume, and power-optimized systems for any given mission duration. The conditions are very similar to those in a submarine, apart from the fact that in an emergency the submarine can reach a safe condition in a short time. The similarities and systems used in submarines were amongst the first inputs for the design of spacecraft life support systems. Concepts optimized to mission duration are mandatory because human needs and space missions are both very much time dependent. In addition, the stability of these systems, just as for the Earth’s ecological system, cannot be realized by large buffer capacities but must be achieved by sophisticated design solutions and high reliability. Modern life support systems can handle the recovery of oxygen and water to a very high degree, which reduces the resupply mass quite considerably. For future systems the food loop must be at least partially closed by growing plants from waste products in order to further reduce the difficult resupply or initial high transportation costs. This chapter provides an overview of possible regenerative functions and system concepts, life support systems employed in the first 50 years of human spaceflight, and options for future biological life support systems for long-term space exploration.