you remember the last post i made in this community about farming on mars in small greenhouses?
yeah, that rings a bell. i just wanted to know how to construct these plastic tubes sothat they would hold 1 bar of pressure inside. so i did some calculations. they are a real mess, don't look at them:
(r/d is the ratio of the tube radius to the wall thickness btw. r/d = 300 is the point where it tears, so having a thicker wall than that should be fine)
i mostly wrote this down as a reminder for myself sothat i can roughly understand what i did later.
anyways, the results are: basically you can make such a tube with 10cm diameter easily out of polyethylene or any other type of polymer with only a wall strength of 1mm. it will hold, it won't burst. i used some insights from ultimate tensile strength, linear elasticity (Young's modulus) etc.
basically what i did is to assume that the force that the wall material exerts to push to the inside is equal to the gradient in spring-energy that would be stored inside the wall material depending on radius. So dW(r)/dr = F is the force with which the wall material pushes inward, where W(r) is the mechanical stress energy stored in a slice of the tube of 1mm thickness.
ask if you want to know something. i'm tired rn and can't tell what i might have missed.
Have you looked at the characteristics of alginate? I ask because you'll want to make these tubes out of something you can source more of, because they will get damaged.
producing plastics on site is already possible with today's technology, from just water and CO2:
https://blog.bccresearch.com/global-co-based-plastics-market-turning-a-green-gas-into-valuable-polymers
if you want a keyword to read up on the whole process: https://en.wikipedia.org/wiki/Syngas