Part 10 of 12 Parts
Sixteen research projects drawn from NASA, the space industry and academia will receive grants from the NASA Innovative Advanced Concepts (NIAC) program in order to study the feasibility of their concepts. Here are more of the projects:
14. Making Soil for Space Habitats by Seeding Asteroids with Fungi
Jane Shevtsov
Trans Astronautica Corporation
Any big, long-term human space habitat will have to grow most of its own food and recycle as many nutrients as possible. For missions that can be easily resupplied, it would make sense to grow crops hydroponically. However, soil-based systems possess important advantages in the context of a large settlement that cannot be affordably resupplied from Earth.
One proposed habitat design is a cylinder that rotates to create artificial gravity and support up to eight thousand people. Such habitats might be used for asteroid mining, space manufacturing and research. Such a habitat would be self-sustaining with respect to food and also would also have ample green space for the support of crew mental health and to function as part of the life support system.
Attempting hydroponic crop cultivation at this scale would run into serious problems with the amount of machinery required and the concomitant proliferation of failure points such as pumps and piping. In addition, hydroponic systems require nutrient solutions and do not lend themselves to the recycling of agricultural and human waste. Such recycling is easily accomplished with a soil-based system through composting the waste and the use of thermophilic methods that are effective at killing pathogens.
The Trans Astronautica team proposes the creation of soil from carbon-rich asteroid material and the use of fungi to physically break down the material and chemically degrade toxic substances. They will use fungi to turn asteroid material into viable soil. The basic concept is to inoculate carbonaceous asteroid material with fungi to initiate soil formation. Fungi are excellent at the decomposition of complex organic molecules, including those that would be toxic to other forms of life. For example, oyster mushrooms have been shown to successfully clean up soil contaminated with petroleum by digesting the hydrocarbons making up the petroleum. Fungi hyphae can penetrate long distances into cracks and exert huge amounts of pressure which physically breaks down rock. Evidence indicates that fungi played a key role in early soil formation on Earth.
The approach of the Trans Astronautica team will consist of two tasks to be accomplished under Phase 1.
1) Task 1 will be to identify the leading fungal species for experimental use on simulated asteroid material. This will be followed by a sturdy of their solid production rates and the effects of physical parameters such as temperature, humidity and oxygen concentration.
2) Task 2 will be the evaluation of a number of different approaches for performing the breakdown of asteroid regolith by fungi in space. These approaches will be ranked in terms of productivity and estimated costs, as well as sizing them to support a target mission habitat within a reasonable amount of time.