There has been a great deal of talk about these 2nd generation bio fuels especially biodisesl from algae, and I was thinking about how spaceflight could really use them.It seems to me that these algae technologies could be used to provide both nutriution and oxygen for human spaceflight. The algae fuel systems consume CO2, water, and sunlight to produce oxygen and simple sugars, like all plants do. However unlike the plants that we normally eat, they do not require all the various minerials and conditions that are required for more complex lifeforms. They also have growing times on the order of a few days, which is very fast compared to plants. What I have been thinking is that long duration human spacecraft could use a simple pipes on the outside of the spacecraft as a bio reactor. The pipes would be exposed to the sunlight, and will use filters and shutters to filter out radiation that is harmful for the algae. CO2 would be extracted from the crew area, concentrated, and pumped into the bio reactor. The algae would then consume the CO2 and release O2, which would be pumped back into the crew cabin. Of course new food processing techniques would have to be developed to transfer the sugar filled algae into something edible. If you think about it algae, as well as, other simple organisms are ideal for space food production, because unlike the more complex lifeforms that we receive most of our food from they require little in resources, and have very quick growth times. Since they are simple they can also be easily genetically engineered to produce the things we need from sunlight.
There's a big snag though, humans cannot eat more than ~100g/day of algae (or more generally single cell proteine) without getting gout. Somewhere during our evolution we lost the ability to break down uric acid, which is a product of DNA / RNA digestion and when we get too much of it, it forms the painful crystals responsible for gout. Spirulina is an excellent food supplement, but not suitable as the main component of your diet. Plus you don't want to be eating nothing but algae soup every day.Fish on the other hand do have the ability to break down uric acid, and Tilapia thrive on a Spirulina diet, so the combination would be very useful for human consumption.
You'd think it wouldn't be that hard to remove the uric acid component, though.
Do not know how you extract CO2 from air.Activated carbon and recycle the activated carbon?Other than chemical processes [such as making methane for example]not sure how you get this impurity out of the air- 1000 ppm is .1 % and might might want to tried to get down to level of 1000 ppm.One could mix the water with the air- use cold and pressurized water- maybe? A problem is no gravity.Edit: I think growing some thing like lettuce and tomatoes could be easier. And lots herbs: clives, Watercress, mint, etc.
Algae have been studied for bioregenerative life support, notably in ESA's Melissa project. Spirulina turns out to be one of the best candidates. It is chock-full of everything you need, including vitamins.There's a big snag though, humans cannot eat more than ~100g/day of algae (or more generally single cell proteine) without getting gout. Somewhere during our evolution we lost the ability to break down uric acid, which is a product of DNA / RNA digestion and when we get too much of it, it forms the painful crystals responsible for gout. Spirulina is an excellent food supplement, but not suitable as the main component of your diet. Plus you don't want to be eating nothing but algae soup every day.Fish on the other hand do have the ability to break down uric acid, and Tilapia thrive on a Spirulina diet, so the combination would be very useful for human consumption.
Aquaculture is a wonderful idea if you can afford the mass budget of all the water. For example, if your mission requires long term high energy GCR shielding, then you might require 5 tons per square meter of water anyway.But if you need to conserve mass, aeroponics seem to be a more promising direction. Besides minimizing water mass, aeroponics also minimizes disease spread.
Quote from: IsaacKuo on 10/07/2011 02:56 pmAquaculture is a wonderful idea if you can afford the mass budget of all the water. For example, if your mission requires long term high energy GCR shielding, then you might require 5 tons per square meter of water anyway.But if you need to conserve mass, aeroponics seem to be a more promising direction. Besides minimizing water mass, aeroponics also minimizes disease spread.All the water would be recycled.
Aeroponics requires far more resources due to slow growth times, and lower concentrations of raw materials.
Quote from: gbaikie on 10/07/2011 03:07 amDo not know how you extract CO2 from air.Activated carbon and recycle the activated carbon?Other than chemical processes [such as making methane for example]not sure how you get this impurity out of the air- 1000 ppm is .1 % and might might want to tried to get down to level of 1000 ppm.One could mix the water with the air- use cold and pressurized water- maybe? A problem is no gravity.Edit: I think growing some thing like lettuce and tomatoes could be easier. And lots herbs: clives, Watercress, mint, etc.First of all, pure CO2 is not a requirement. Algae in its natural environment works fine with CO2 in the concentration it exists in our atmosphere just like plants.Second of all, CO2 can be concentrated using filters, and a variety of other methods.Lastly concentrating the CO2 is desirable because it allows the algae to grow faster due the greater access its raw material, carbon.Like I stated before the problem with lettuce, tomatoes, as well as other more complex forms of life is that they have grow slower, require more minerals, and are more sensitive to their environment, thus they require more resources.
Like I stated before the problem with lettuce, tomatoes, as well as other more complex forms of life is that they have grow slower, require more minerals, and are more sensitive to their environment, thus they require more resources.
... if one could mix crew air with water of algae- just not sure what best way to do this in zero gee. In gravity you simply pump the air into the water- something similar those bubbly things in a fish tank.
The only filter I know that takes CO2 out of the air is a carbon activated filter. A carbon activated filter is good for taking any impurity out of the air. But these filters wear out and need to be replaced with fresh carbon activated filters. That's not a big problem bring lots of fresh filters- but getting the carbon dioxide captured from the air with these filter to the algae in the water is the part I don't know how one could do.We could skip the use of any other kind removable CO2 from the air if one could mix crew air with water of algae- just not sure what best way to do this in zero gee. In gravity you simply pump the air into the water- something similar those bubbly things in a fish tank. Perhaps one turn water into a mist- like garden hose. Do in a box and water will clump to together and you pump out the liquid water [enriched with CO2 of crew air]. If this is cold the crew air would not return to crew with much humidity and water will mix well with CO2.Edit: And/or simply remove humidity from crew air, and put that water in the algae water.
Note that if you're using tilapia for food rather than directly using the algae for food, you cut your effective productivity by an order of magnitude. Each layer of a food chain is roughly an order of magnitude cut in efficiency. In contrast, aeroponic crops can be used directly for the entire diet--including complete proteins from a variety of legumes.
Quote from: strangequark on 10/07/2011 03:24 pmYou'd think it wouldn't be that hard to remove the uric acid component, though.The uric acid is produced by the human body as it breaks down the RNA/DNA from the algae, so you'd have to somehow break down the uric acid inside the human bloodstream, or to break down the food before eating it as they presumably do for intravenous feeding. I've read there is an experimental drug that can help the body break down uric acid, but I think it has nasty side effects.And of course, that still doesn't solve the algae soup all day, every day problem.