The Dynamics of Human Spaceflight Systems – Part V
By Dr. Gary L. Deel, Ph.D., J.D.
Faculty Director, School of Business, American Military University
This is the final article in a five-part series on the dynamics of human spaceflight systems for interplanetary and deep space missions.
In part IV, we looked at the need to protect spacecraft from the harsh outer space environment while maintaining comfortable temperatures for crews. In this final part, we’ll explore the challenges surrounding keeping human spaceflight crews fed and hydrated during their missions.
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An obvious factor to be considered in interplanetary space station design is how the crew will have clean drinking water and adequate food. On the international space station (ISS), engineers designed a system that allows the station’s water supply to be safely recycled from clean water to waste, then through a series of filters back to clean water again. This idea may not sound appetizing, but its safety and efficacy have been well-established. There is no reason to believe that the same technology would not work on interplanetary voyages, so the water problem appears to have been solved.
With the Water Problem Solved, the Food Challenge Is Not So Easy to Overcome
The food challenge is not quite so easy to overcome, however. Currently, ISS crews receive food rations through periodic resupply missions. In other words, the crews get food delivered on a regular basis. This works because the ISS is in perpetual orbit around the Earth, and therefore is always within reach of low-Earth orbit rockets. However, interplanetary missions obviously would not be so conveniently accessible. So for these voyages there are two main alternatives: 1) carry all the food necessary for all crew members for the entire round trip, or 2) grow food on board so that a food supply can be constantly replenished.
The first option is inarguably easier on the crew, as no one would have to be responsible for cultivating food crops. However, this of course would limit food varieties to either non-perishable foods or those that can be freeze-dried for storage and then rehydrated as needed. Then there is the significant consideration of storage space needed for all of the food supplies.
A Six-Member ISS Crew’s Round Trip Journey to Mars Would Take about Two Years
If a six-person crew of the ISS made a journey to Mars, it is likely that the shortest possible round trip — due to planetary orbital periods — would take about two years. This would mean that, at three meals per day, the space station would need to be able to stow more than 13,000 meals on board. It goes without saying that this would add considerably to the cost and design challenges of the mission.
That is not to say that option two, growing and harvesting food, is easier. Experiments have been conducted in space on the feasibility of growing things in microgravity. Generally, they have suggested that plant production in artificial environments — such as indoor gardens, hydroponics, and other models — is feasible. Technologies such as artificial lighting, irrigation, and humidification do a passable job of simulating natural conditions on Earth.
However, farming — whether in space or on Earth — requires specialized knowledge and skills. So this likely means that one or more crew members would need to have an expertise in agriculture, which would complicate crew selection criteria.
Second, while such a space station would not need space to store its food for the voyage, it would need more than just a little space to manage its crops. Farming demands a large amount of square footage. Even though crops can be stacked vertically in specially designed shelves to make efficient use of interior space, they would still require a lot of growing space. Given the number of crew members who would need to be fed with these crops, the farming modules would probably consume most of the habitable area in such a space station.
Another consideration would be variety. Many different crops could potentially be grown in artificial environments, but astronaut farmers would have to consider the crew’s dietary needs in selecting foods that would complement each other well nutritionally and provide the most caloric value.
Additionally, at a minimum, different plants would have to be grown because of the need for crop rotation to ensure that soils and growing environments are not depleted of nutrients and resources necessary for cultivation. So, although the idea of growing food on a space station is attractive because it makes food available on trips of virtually unlimited lengths with relatively fixed infrastructure requirements, it isn’t without its own challenges.
Tying a bow around this series, the challenges facing interplanetary space station designers and engineers are both numerous and serious. However, none of these problems is without a potential solution. With a sincere effort of human innovation and ingenuity there should be no doubt that we will eventually overcome these obstacles and make human deep space travel a reality.
About the Author
Dr. Gary Deel is a Faculty Director with the School of Business at American Military University. He holds a J.D. in Law and a Ph.D. in Hospitality/Business Management. Gary teaches human resources and employment law classes for American Military University, the University of Central Florida, Colorado State University and others.