Sustainable Living Aboard Spacecraft
Modern spacecraft utilize complex recycling systems to maintain proper levels of atmospheric gases inside astronaut living spaces. Since we cannot reuse 100% of our waste, this is not a completely sustainable process. Longer expeditions would require bringing containers of oxygen or similar life support systems to ensure that the recycling process could go on as long as possible. Food is also a very important aspect of space travel, yet food cannot be recycled. Travelers must either bring all necessary food with them or grow it on board (Satyapal et al. 2001, Wieland 1998).
The only surefire way to fully maintain food and oxygen levels aboard a spaceship is via plants and their photosynthesis. The two types of plants typically considered for life support use are algae and higher plants. The benefits and drawbacks of these two types of plant life as detailed by Salisbury et al. are shown below in Figure 1 below
Figure 1. Benefits and drawbacks of algae and higher plants aboard spaceships, information retrieved from Salisbury et al.
The point that algae leads to nutrient deficiency over time is a very compelling component for the (primary) usage of higher plants. These plants can be grown by using xenon lamps roughly as powerful as sunlight. Although successful experimental trials have taken place in remote locations on Earth, there has not yet been an entirely successful attempt to grow a higher plant in outer space (Salisbury et al. 1997).
A more fully encompassing dietary recycling loop titled MELiSSA has been proposed. MELiSSA utilizes varied types of bacteria and plant life in four separate compartments to create a highly sustainable system of interactions (Hendrickx et al. 2005). The interaction diagram for the MELiSSA design as created by Hendrickx et al. is shown in Figure 2
Figure 2. “Scheme of the MELiSSA loop” retrieved from Hendrickx et al. 2005
It is important to note that life support systems go beyond the role of providing food, water, and comfortable living conditions for astronauts. These support systems must be able to decisively combat any sudden on-board emergency such as a fire. Fires rob the closed habitat of its precious oxygen and can throw sophisticated systems such as the MELiSSA loop into chaos. It is highly important to have fallback systems in place in case of emergency situations (Wieland 1994).
Future spacecraft may be extremely large, maybe the size of small cities. These spacecraft will be able to have complex sustainable life support systems of both plant and animal life. With a spaceship large enough, life on board can fully simulate life on Earth and provide thousands of travelers with an entirely stable habitat.
References:
Salisbury FB, Gitelson JI, Lisovsky GM. 1997. Bios-3: Siberian Experiments in Bioregenerative Life Support 575:585
Hendrickx L, De Wever H, Hermans V, Mastroleo F, Morin N, Wilmotte A, Janssen P, Mergeay M. 2005. Microbial ecology of the closed artificial ecosystem MELiSSA (Micro-Ecological Life Support System Alternative): Reinventing and compartmentalizing the Earth’s food and oxygen regeneration system for long-haul space exploration missions 77:86
Wieland P. 1994. Designing for human presence in space: An introduction to environmental control and life support systems Abstract
Satyapal S, Filburn T, Trela J, Strange J. 2001. Performance and Properties of a Solid Amine Sorbent for Carbon Dioxide Removal in Space Life Support Applications 250:255
Wieland PO. 1998. Living Together in Space: The Design and Operation of the
Life Support Systems on the International Space Station 1:59
