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Comment by ofirg | Hacker News Reader

Is the radiation not similar to the one you get in space? seems like that would be a cheaper place to test the effects of radiation.

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Depends where in space. From the article: "the International Space Station orbits within the Earth’s magnetic field, and so it is exposed to much lower radiation levels than the lunar surface".

from the article:

> Growing plants on the ISS is a complex business, and Porterfield says a chief concern is that plant roots depend on gravity to draw water.

So while the radiation might be similar (I'm not sure), other variables are different.

I’m sure they have considered this and/or doing it already but you’d only need a small centrifuge to simulate gravity for an experiment.

A small centrifuge won't work; you get a strong coriolis effect. A large centrifuge could, but the ISS doesn't have one of those. It would need to be huge to be absolutely sure your data is accurate.

Late to reply back but I’m not sure why that matters when all you are looking for is roots to have enough stimulation to uptake water.

Plant roots don’t need gravity to draw water! Plants use evaporation and the tensile strength of water (yes, really!) to draw water up against gravity.

While that is true, plant roots and stems use gravity to know in which direction to grow (roots down and stems up), so that will cause problems in space.

NASA has succeeded to grow some plants on the ISS, by making them grow towards a source of light (i.e. LEDs), but until now this has worked only for some very low-growing plants, like lettuce and some varieties of cabbage, not for plants with deep roots and high stems.

It should be much easier to grow algae in the absence of gravity, but those are not as tasty as terrestrial plants.

You could probably engineer some palatable food items with algea and mushrooms. I would put my money on fungus as a food source.

I think you are thinking of capillary action, adhesion, and vacuum pressure. Water does not have tensile strength.

Water is capable of sustaining pressures of -140 MegaPascal, or about -1400 atmospheres.[1]

[1] https://www.nature.com/articles/nphys2475

That is still different than mechanical tension.

It's very odd to phrase it as "tensile strength", but capillary action is an expression of surface tension, which is the result of molecular cohesion--two (water) molecules resisting separation. In other words, strength under tension, with measurable stress and strain. With some squinting, you've got tensile strength with elastic deformation.

I think you are right and that is what they are getting at, but it is more a property of the system, not thee material. It is hard to reconcile fluid flow of a liquid with tensile strength.

They're also testing the effects of reduced gravity.

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