Space bread

In the first week of the mission, I reactivated some sourdough starter given to me by a kind friend. I rehydrated it and administered its first feeding, then went back to my work. When I returned, I found that it had fallen victim to the #1 killer of sourdough: a soapy dish sponge. Lesson 1: label your starter.

Fortunately I had enough dried starter to fail ten or twenty more times, so a couple days later I reactivated some more. I fed it and it grew. I fed it some more, stirred in the water and flour, and licked the spoon before putting it in the dishtub. Lesson 2: no eating the starter. A brief and very fizzy battle for my digestive tract ensued. Laura: 1. Sourdough: 0. But it was a near thing.

Let’s talk about zero-G. A clinostat is an instrument used to simulate low gravity. Basically, it’s a small machine that rotates around one axis that sits at an adjustable angle from vertical. When rotated horizontally, it simulates zero-G. It can be set at other angles to simulate Mars gravity, Moon gravity, anything between zero and Earth. Clinostats are commonly used with microbe cultures or small plants to study the effects of low gravity. A crewmate of mine brought a clinostat to the hab.

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Clinostat on loan from ISU

Of course, the first thing we cultured in zero-G was sourdough. My crewmate and I printed up a new capsule for the clinostat more suited to the quantity and consistency of sourdough starter/dough. When the starter had finally grown enough to take some for bread, I pulled off a piece of dough during the final rise and stuck it in the clinostat. We sealed it off with a super high tech system involving a piece of oiled fabric and a rubber band and let it rise. News flash: space bread doesn’t taste any different.

The next order of business was to actually culture the starter in the clinostat. Now, to function properly, a clinostat capsule needs to be completely full at all times. Otherwise, the air pocket moves around and induces shear forces that change how the tumbling simulates low gravity. So we filled the capsule we printed up all the way with starter. Because we were trying to be somewhat scientific, we had a similar volume of starter sitting in a bowl next to the clinostat – this keeps age of starter, feeding, and temperature throughout the day constant. At some point, we’ll print another clinostat capsule identical in shape for use as a control – then air flow to the starter will also be more constant.

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Capsule, take 1. Pro-tip, fabric stretches when oiled.

The capsule rotated all day. When it was time for feeding, we took it off and measured the change in mass. Oddly, it had gained mass, whereas the starter on the floor had lost mass. To feed it, we dumped out the starter, stirred in the flour and water, and refilled the clinostat capsule completely with the fed starter. We popped on the cloth cap, and let it go. A few hours later, we checked back in to find starter leaking everywhere. Lesson 3: starter expands after feeding. A lot. Fortunately, my crewmate had thought to put a dish under it in case the cap didn’t hold. I collected up the starter and made dough with it. It was absurdly active – it nearly overflowed the bowl I used to rise the dough. We tried to cultivate zero-G starter once more with elastics over the cap, with the same (delicious but messy) results.

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Bread bowls, also possible on Mars.

Remember, we live in a dome. We live off the grid, and we ran into a water emergency. The upshot for the sourdough was that we couldn’t afford the water to clean up the giant mess that it will continue to make in the clinostat until we figure out how to contain the beast. So we had to temporarily discontinue our space bread experiments.

So in the meantime, the next step was to improve our capsule. We designed a new capsule with two parts that could be connected with elastic to allow for expansion of the contents to approximately twice their initial volume. But as you’d expect from a new piece of equipment, it didn’t work at all at first – we left far too little space between the inner and outer parts for them to slide against each other properly. Sanding commenced.

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New and improved capsule, now with oil seal.

Water was delivered, and we resumed our experiments. If you’ve ever made something out of papier-mâché, you’ll anticipate our next problem. The sourdough starter, which is mostly flour and water, acted as glue. Solution: an oil seal. But during all this prototyping, a more systemic problem emerged.

Sourdough starter contains a symbiotic balance of yeast and bacteria. The bacteria produce lactic acid – that’s why sourdough is sour. Since the initial rehydration, the bacteria in the starter has proven to be the fitter organism for hab bread life and has completely out-competed the yeast. So I’ve given the sourdough a new lease on life. I’ve started again at step 0, learning from lessons 1 and 2.

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Space bread, (hopefully) coming soon to a hab oven near you.
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