Life Support Systems for Manned Mars Missions, Overview Thais Russomano Contents Introduction ....................................................................................... 2 Effects of a Hostile Environment on an Earth-Adapted Physiology . ... .. ... .. ... ... .. ... ... .. 3 The Potent Problem of Radiation ................................................................ 3 The Psychological Stress of Being Far from Home ............................................. 5 The Advent of Advanced Life Support Systems ................................................ 5 Closing the Loop on Regenerative Life Support . ............................................... 6 Calculating the Ins and Outs ..................................................................... 7 Bioregeneration as a Solution .................................................................... 8 In Situ Resource Use: An Important Addition ................................................... 10 Making Fiction a Reality ......................................................................... 10 Cross-References ................................................................................. 11 References ........................................................................................ 11 Abstract A manned journey to Mars has long since been the subject of science fiction and fantasy, but continued advances in technology have opened up the possibility. The lengthy distance to the planet, together with its hostile environment present dangers to the health and well-being of space-travelers and huge logistical difficulties in terms of adequate resource provision to sustain a crew for a return journey and time on the planet surface. Advanced life support systems have continued to adapt and develop since the flight of Russian cosmonaut Yuri Gagarin in 1961 and the NASA led Mercury, Gemini, and Apollo missions, T. Russomano (*) Microgravity Centre, The Pontifical Catholic University of Rio Grande do Sul, Porto Alegre, Brazil International Space Medicine Consortium Inc., Washington DC, USA Centre of Human and Aerospace Physiological Sciences, Faculty of Life Sciences and Medicine, King’s College London, London, UK e-mail: [email protected] # Springer International Publishing AG 2017 1 E. Seedhouse, D. Shaler (eds.), Handbook of Life Support Systems for Spacecraft and Extraterrestrial Habitats, DOI 10.1007/978-3-319-09575-2_188-2 2 T. Russomano which required open-loop, disposable systems of short duration only. Arrival of the Space Shuttle program and International Space Station led to a shift in specifications, with emphasis on reusability and long-term use. This ongoing process has resulted in a complex life support system capable of sustaining a six-astronaut crew for several months. Key technologies, such as oxygen gener- ation and water recovery systems, have reduced the need for the costly resupply of some materials to the orbiting space station, but replenishment of consumables, propellant, and maintenance equipment continues. Frequent resupply is an unfeasible option for a long-duration deep-space mission, meaning a bioregenerative life support system will be essential. Research continues in this field, with one example being the European Space Agency managed MELiSSA (Micro-Ecological Life Support System Alternative) project. Further advances in a system providing the essentials for human survival in a Mars environment, together with technology for the use of the natural in-situ resources of the planet, will undoubtedly open up exploration of this new frontier in the coming decades. Introduction A manned space journey to Mars, the fourth planet in our Solar System, will not be an easy task to accomplish, being fraught with difficulties. The huge void of space that separates Mars from planet Earth varies greatly depending on the orbits of the two planets, ranging from 34.8 million miles at its closest to 249 million miles at its furthest, with the average distance being 140 million miles. Travelling from Earth to Mars requires more than a simple “point and shoot” launch of a spacecraft, but will involve planning a trajectory that takes account of the huge distance and the differing orbits of the two planets. Calculations using the Hohmann transfer orbit, which sets the optimum elliptical orbit needed to rendezvous a spacecraft with Mars using the least amount of fuel, have indicated a travel time of between 6 to 9 months, depending on rocket velocity and the proximity of the planets (Seedhouse 2009). Such lengthy flight duration will require a vast amount of propellant in order to leave Earth’s gravity, reach Mars, and still have the possibility of returning home again. In addition to the weight of propellant, however, consideration must be given to the consumables that will be needed to sustain a crew for the return journey, as well as the time spent on the planet surface, and this in itself will be a significant factor. It is estimated that the consumables required for a crew of just six astronauts for a return space mission to Mars will range from 100 to 200 metric tons, though it is more likely to be nearer the higher figure. This enormous amount of weight would require a series of heavy-lift launch vehicles to guarantee the necessary life support systems and supplies would be accessible to the crew. Therefore, it is vitally important that the correct balance is achieved between keeping the payload weight down to a minimum, while at the same time ensuring all essential life support provision is available, given that resupply from Earth or an early return to Earth are not feasible Life Support Systems for Manned Mars Missions, Overview 3 options. In order to achieve this, it will be vitally important that the life support systems adopted for such a journey to Mars and for the time spent on the planet surface be as self-sufficient as possible; to this end, it will be essential that the design of the life support systems be as regenerative as possible, operating to a high degree as a closed-loop system (MacElroy et al. 1992). Effects of a Hostile Environment on an Earth-Adapted Physiology The distance between the two planets is not the only difficulty. Assuming the success of the first stage of the mission and the safe arrival of the astronauts onto Martian soil, they will be faced with an entirely new and hostile environment to which mankind is not yet adapted. The planet Mars is smaller and less dense than the Earth, which creates a lower gravitational force, called hypogravity. Its thin atmo- sphere is rich in carbon dioxide (95%) that is a toxic gas for humans, its atmospheric pressure is very low in comparison to Earth, and the Martian surface temperature ranges from À140 C at the coldest polar caps to 35 C during the equatorial summer (Russomano et al. 2008). It can therefore be seen that the mission as a whole will submit the space travelers to extreme conditions and environments; our experiences to-date with space travel and Low-Earth-Orbit (LEO) space stations has already demonstrated the detrimental physiological and psychological consequences of this exposure. Human anatomy and physiology have been shaped by Earth’s gravitational force over millions of years. When this force is reduced or removed, such as in the microgravity of space, it is known that all body systems are affected. Bones that are no longer required to support the weight of the body begin to lose their mass continuously, particularly so in the lower limbs. Skeletal muscles that are not needed to counteract the effects of gravity suffer a large degree of atrophy. The immune system appears to become less active in microgravity, and the cardiovascular system adapts to the space environ- ment by redistributing blood and fluids from the lower to the upper body, while decreasing the plasma volume and heart size. It has been seen during space missions that astronauts also present a reduction in the number of red blood cells, called space anemia. The vestibular or balance system that is designed to keep our visual world stable and keep us from falling suffers from the moment of insertion into micro- gravity, causing a condition called space motion sickness, which is known to affect 70% of astronauts in the first 72 h of a space mission (Barratt and Pool 2008; Russomano et al. 2008; Seedhouse 2009). The Potent Problem of Radiation A major consideration having serious consequences on astronaut health is the effects of space radiation and the degree to which they will be exposed during a round-trip to Mars and time spent on the planet surface. Radiation can be defined as a form of energy that is emitted or transmitted in the form of rays, electromagnetic waves, 4 T. Russomano and/or particles. It can be divided into: visible light (radiation that can be seen), infrared radiation (radiation that can be felt), and radiation such as x-rays and gamma rays, which are not visible and can only be observed directly or indirectly with special equipment. LEO space missions, such as on the International Space Station (ISS), have shown that crew members are most likely to be exposed to high doses of radiation during solar particle events, also called solar flares. On these occasions, extremely high energy radiation is emitted in a short period of time. Most of this radiation is prevented from reaching the surface of Earth and having consequent effects on living organisms or even the astronauts on LEO missions by our planet’s magnetosphere. NASA data has shown that radiation exposure for astronauts aboard