gandalf_der_13te

source: https://www.scientificamerican.com/article/how-solar-became-the-cheapest-form-of-energy-in-the-world/

i just did some rough engineering/math to figure out how to build domes to live in. Assumption of course is inside pressure p = 0.2 bar.

• Assuming that you want to source as much construction material as possible on-site (In-Situ Resource Utilization), simple materials like Polyethylene might be advantageous to more complex materials like carbon nanofiber etc
• Polyethylene can be processed at temperatures around 200°C, while steel would have to be heated to 1500°C. Especially in the early days, plastics are clearly cheaper than steel. Let's see whether we can get away with it:

A room-sized dome (i.e. sphere, but only the upper half, with sphere-radius r = 10 m, so maximum diameter d = 20 m if you cut at half height) with inside pressure p = 0.2 bar would require a thickness d = 6.66 cm roughly, if it's made of PE. That does not sound undoable! In fact, that sounds entirely reasonable and doable.

There's a third, less well-done page:

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this isn't really a new community but i think promoting it from time to time makes sense because it has barely any subscribers and most people probably don't know about it. so i'm promoting it here to maybe give it some fresh new views! enjoy

Edit: because i'm stupid, here's the link: !mars@discuss.tchncs.de

the point is that you can actually live inside the rockets when they first land, you don't need to build extra housing immediately. this significantly simplifies the mission requirements, at least for the first few years.

tank volume is about 1000 m³, which stores about 5000 kg of oxygen assuming 5 bar of pressure, which lasts a crew of 10 for about half a (martian) year, or about as long as the winter sand storms threaten to reduce solar panel production, so you have enough oxygen to breathe through this time.

it is a myth and misleading to assume that energy supply has to be constant. it is good enough if you can intermittently replenish your live support resources.

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.

i think the article does a wonderful job at illustrating the point without even uttering a single word

you know about these mattresses that they sell for swimming?

they are entirely made of plastic and could be produced on-site. the advantage is that as the structure size is smaller, you need less material to build the greenhouse, and also since it has a steeper curvature, it can be pressurized more easily (the less curvature, the thicker the materials have to be to hold the pressure within).

to harvest the algae, you'd open the lid on one side and let the whole goo out, including the water, which you then put through a filter to extract the algae out, then you can recycle the water.