Is space suit using algae for oxygen production possible?

Question

Current space suits carry oxygen bottles for oxygen and some sort of non-regenerative carbon dioxide scrubbers for removing carbon dioxide. This obviously means that a space suit is only able to provide life support for a very limited time.

Around 30 liters of algae and water is able to provide enough oxygen for a human to breathe and remove the equivalent amount of carbon dioxide. This has been experimentally verified first by Shepelev and then many others. However, in some experiments this algae was spread over 8 m².

So, my question is - would it (theoretically) be possible to build a suit that would use algae as regenerative life support?

• Is it possible to carry the algae in a wide enough spread layout to rely on natural sunlight, for example, on Mars?
• Is it possible to carry a power source capable of producing enough artificial light for the algae for extended periods of time?
• Atmospheric leakage would have to be replenished somehow, but perhaps this could be a smaller oxygen bottle lasting for a very long time?
• Water vapor would have to be condensed but that could work like it does on current suits?

Answer 1

The one critical problem is heat dissipation.

Imagine components of such a space suit.

8m^2 utilizing sunlight is far too unwieldy to carry around. This needs to be far more compact.

30l is bad, but not very bad. It can be done in a way that would be useful in microgravity. Think multiple thin modules composed of moisturized algae caked between layers of thin LED growth lights. An active pumping system (sorry, no gravitational bubbling separation in microgravity) with water reclamation/reintroduction, a good RTG battery to keep it powered, extra filters for moisture and other contaminations. Everything works... except for the heat.

Solar irradiation on Earth in a moderate climate in reasonable though not excellent weather would be of order of 200-300W per m^2. So, 1000-1500W. Efficiency - let's extremely generously assume 10% (normally 3-7%). So the RTG alone creates at least 9kW of heat. Even if we use different power sources we still have 1-1.5kW for growth lights, and that's still not including the pumping, any active thermoregulation systems, mixing etc. The spacesuit is an oven that would require simply huge radiators - something far too unwieldy to use as a portable unit.

I could see a system like that used even with very small spacecraft. I could picture it used on a space station with non-autonomous space suits tethered with air hoses. But the heat dissipation needed just won'tfit in the volume of any practical spacesuit.

Answer 2

Spacesuits use rebreather technology. Exhaled air is passed through CO2 scrubbers, then measured for oxygen content. Oxygen from a 100% oxygen source is added to the air stream to bring it back up to normal.

Exhaled air still has oxygen in it, so the air stream only needs to be 'topped up'.

There's actually more to it - the air handling system also removes excess humidity, odors, and other possible contaminants. Water condensed from the humidity goes into a storage pocket that the astronaut can draw from. There's a secondary O2 system in case the main life support system fails. It's good for at least 30 minutes, depending on the design. That's barely enough time to get someone back into the ISS atmosphere. While using an algae system separately to generate the oxygen used in the space suits might be feasible, at the very least it would highly increase the complexity of the air handling system in a space suit, making it much more prone to disastrous failure.

Answer 3

Photosynthesis has terrible efficiency. Photosynthesis has an efficiency of only a few percent, maybe at best 10% if your LEDs have an optimized spectrum.

Conversion of electricity to light is subject to LED efficiency. It looks like LEDs are something like 12% efficient (or maybe as much as 50% efficient).

So maybe like 1–5% of your power is going to oxygen production. So as @SF said, heat dissipation would be a limiting factor. It's likely that some other chemical process could do better. There was a lot of work for converting carbon dioxide into hydrocarbons in the early 2000s. Most of these produce start with 2CO$_2$ $\rightarrow$ 2CO + O$_2$ and then convert combine the CO with H$_2$ produced by electrolysis to make hydrocarbons. You'd have to be careful with the CO though so as not to poison your astronaut. There have been other suggestions.

Answer 4

You would need way too much. Joel from "JoelCreates" tested this and has almost managed to reach equilibrium by using 4 x 50 gallon tanks full of algae, all of which needs a lot of light and airflow. Here's a great video:

Answer 5

Answer: NO

It would require approximately a metric ton of nutrient to provide O2/CO2 processing for a single person. There are significant difficulties operating such a system in microgravity. See How much algae would you need to fully support a person? for details

PS: Shepelev calculated 30 liters would be enough, but "The oxygen content initially produced by the algae plummeted rapidly by the close of the first day" https://kk.org/mt-files/outofcontrol/ch8-c.html. He was operating under normal gravity. Microgravity makes it much more challenging to separate microbubbles of gas from liquid media.