Soylent

closes the Life Support Cycle with two part types:

• solid and liquid waste is reduced to a Sterile Organic Slurry by a Super Critical Water Oxidation Unit.
• Sterile Organic Slurry is fed to algae, cultured in arrays of water filled polymer channels exposed to the sun - producing Oxygen, Food, and Water.

Soylent can be used stand alone as 'cosmetic' parts, or functioning with TAC Life Support.

The part size, mass, volume, and power demands try to be 'fairly realistic'. Quantity/volume of algae required is worked out on the basis of what is required for a 'man day' but not adjusted down to Kerbal size. The assumptions are based on continuous sunlight so if the craft will be experiencing periodic darkness you should scale up the number of Soylent arrays correspondingly. The Super Critical Water Oxidation is exothermic, it's basically a controlled liquid phase fire, so it has modest power demands for pumping and 'ignition'.

This system builds on the work of Evgenii Shepelev who in 1961 sealed himself in an iron casket with 8 gallons of green algae. Two kinds of Algae Array are provided; one reflecting optimistic assumptions, and the other mid range assumptions:

• Solent Red reflects optimistic thinking on algal yield, purely by serendipity this worked out at one small solar array to support a Kerbal! or 11 Kerbals per Gigantor.
• Soylent Green reflects more conservative thinking on algal yield, somewhere between best and worst case a Gigantor sized array will support a Kerbal.

TAC Life Support interoperation

If TACLS is present the parts will inter-operate to 'close the loop'. The resource conversions for 'a man' worth of algae are set to match TAC consumption and production rates. The parts will 'catch up' after being un-focused, for example flying other vehicles or warping in KSC. You need to ensure sufficient buffer resources since the TAC catch up is not perfect. I found the catch up lagged by up to four days, but YMMV, insufficient buffer will kill the crew. KSP doesn't really handle high warp electricity generation correctly so you need a battery buffer to max warp.

The Super Critical Water Oxidation Unit adds a 'sprinkle' of Soylent Starter (essential micro nutrients etc) to the Sterile Organic Slurry it produces. It's a tweakable resource, one part Soylent Starter will support the production of 1000 parts Food.

USI Life Support interoperation

If USI-LS is present the parts will inter-operate to 'close the loop'. The resource conversions to 'a man' worth of algae are set to match USI consumption and production rates. Soylent uses the USI-LS resource converters, so it behaves just like the native USI-LS 'greenhouses' - SoylentStarter resouce is still required.

**It's a joke right? I like realism, how seriously should I take this? **

Although it's named for the fictional Soylent, the functionality is intended to be 'near future'.

I read that a company was starting to produce high protein food pellets for farmed Salmon from processed methane eating bacteria, at under USD 2.00 / kg ( Methylococcus capsulatus ). Naturally I thought - methane, Mars ISRU, food for Mars Astronauts!

Turns out people have been thinking about microbe based life support for a long time. Early experiments in the 1960's, NASA reports from the 1980s 84 & 88 (including 'why not genetic engineering'), a large ongoing ESA research project MELiSSA. These are all proposing some mixed system of algae, bacteria, plankton, etc.

Who knows how close it is, but it seems like there are some compelling reasons to think it will pan out:

• Earth's life support system has microbes as huge and critical component.
• The lower down the food chain you eat the more efficient it is, and you cannot get any lower than microbes. Even if you don't stay right at the bottom it seems like a good place to start.
• Greenhouses are fiddly, labor intensive, take a lot of space/mass, and don't play well with others (for example their equilibrium humidity is higher than humans and electronics like - not a killer but has to be managed).
• We can manipulate microbe bio-mass by pumping water around, since it's all industrial and mechanical it can be automated and run remotely.

On the downside no one has got far enough with the production aspect to start worrying about the palatability aspect - but since people basically like fatty, sweet, and salty you can imagine a super centrifuging thermo mix machine that spits out various blends and textures of pellets, bars, and pastes.

So Algae? not really, but Microbes surely.

Light, Distance, & Yield

The Soylent Algal Arrays use sunlight, the intensity falls off as the inverse square of the distance. Using Kerbin as 100% you get light intensity as % of Kerbin normal:

• 38.98 % @ Duna
• 08.46 % @ Dres
• 04.00% @ Jool
• 01.40% @ Eeloo

The photic zone on Earth goes down to 1% of surface intensity, below that intensity photosynthesis will not operate. But it looks pretty grim, at Jool you need 25 times the collection area to get as many photons as at Kerbin.

It turns out photosynthetic efficiency is linear with light intensity up to 10% of earth surface normal, after that it's 'saturated' and the extra light is not useful. So yield will ramp up from 0% to 100% as light goes from 1% to 10% of Earth surface normal. This gives the yield as a % of Kerbin normal:

• 100% @ Duna
• 86% @ Dres
• 1/3 @ Jool
• 4% @ Eeloo

So for Jool missions you should triple the 'nominal' Algal Array requirements. If you are on a surface with night and day, or in low orbit experiencing periods of darkness you should scale up accordingly. If you will be spending a fairly short time at each end of a trip with periodic darkness then you can just make sure you are a little over break even production and use your life support supply buffer to 'tide you over', usualy there is plenty of time to catch up during transit - just make sure your waste buffer is large enough.

If you are playing in Real Solar System the yields work out as:

• 100% @ Mars
• 100% @ most of the asteroids
• 38% @ Jupiter
• 0% at Saturn - it's sitting right round 1% light intensity

I'd originally intended to have the arrays produce 'photons' for the Algae, however KSPs seemed to bork it under high warp and in any case does not model solar arrays for un-focused craft. Until I resolve this somehow, I have eliminated the photon dependency - just pretend it's there.

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