Thermoplastics to Mars - "Manufacturing" the first missions

C M Edwards · 2002-06-03 11:59:47

Mars probably has raw materials available for the manufacture of plastics, particularly hydrocarbon polymers. So, in the far distant future, it is reasonable to expect settlers to have their own source of these materials.

However, I think we should consider how plastics can be used by the very first missions.

Consider polyethylene and polypropylene. Both can be synthesized from methane, though that may not be of great importance to early missions. Both are thermoplastics that are easily melted and cast into almost any shape. They can also be cut, drawn, pressed or worked by almost any other method at the proper temperature. Between them, they can be used to build shelters or ships, derigibles or drinking glasses. Equipment cases, including XRF chambers, mixers, and other bulky items, can be made from pre-cast sheets of these plastics instead of having to be stored fully assembled for the whole trip. They also make great rocket fuels, burning as well as or better than most hydrocarbons. Methane and propane are better, true, but not nearly as dense and harder to store. And you can make the tanks to store them out of plastic, including the insulation and every fitting. A launcher using polyethylene as fuel has engines that are largely solid blocks of plastic, providing it with better structural integrity. A vehicle whose superstructure is made of these plastics can be melted down for fuel & materials using relatively simple equipment. And if that?s not enough, a block of plastic large enough for use on site weighs slightly less than the same amount of water ? which, incidentally, these plastics can both be burned to obtain.

We can send enough plastic to build an entire base and furnish it, too. It would fit in a few cubic meters. If that were practical, the hab sent need be scarcely larger than the Earth Return Module.

If we ask the first crews to build a base aside from the can they arrived in, I think we should send them some plastic to build it with.

CME

Phobos · 2002-06-03 14:17:24

I think it if we're serious about setting up any kind of permanent colony, it's a must that we pretty much do what you suggested. A colony is going to need manufacturing ability so it can replace materials and increase the habitat size of the colony on a whim should the need arise. It could
be interesting sending engineering experiments along with the crew that would enable them to identify minerals in the regolith and try to extract and purify them on a small scale. I agree also that we should send materials so the crew can experiment with building things like domes. It probably wouldn't be to much of a problem to give them materials to build something like a 10x20 meter dome. Then the next mission that arrives could bring equipment to make the dome or whatever structure the crew set up habitable. Might be good for greenhouse experiments.

Shaun Barrett · 2002-06-04 19:13:27

As usual, C M Edwards comes up with fascinating food for thought!
It's a fabulous idea to use moldable, expandable lightweight materials to actually make what we want on Mars. It puts me in mind of stuff you can buy at hardware stores. I forget its name and constituents, but you spray it into awkward spaces and it expands into all the nooks and crannies and then solidifies. It's not a tough material but is a good insulator and can be cut and sanded once set.
Perhaps using compressed Martian air, we could do something similar with melted blocks of polymer to create all sorts of structures and insulation layers at a Mars base?
Can you, in fact, use compressed air to expand liquid polyethylene and polypropylene into a kind of foam which will set? And does anyone know whether such 'foams', such as expanded polystyrene, are, or could be made to be, good radiation shielding?
One more thought! What's the vapour-pressure of liquid polyethylene? Could we heat it and work with it out in the open on Mars, or would it explosively boil away or otherwise deteriorate?
:0

Josh Cryer · 2002-06-05 10:46:03

I am not sure about the vapour pressure of polyethylene. Liquid polyethylene would most likely cool the second it left the sprayer, much like a spray of water would freeze instantly. It's an interesting idea, though. Spraying liquid plastics on underground walls would be a lot easier than sealing them with bricks.

Don't forget, though. Aluminum and iron are very abundant on Mars. And concrete is relatively easy to make. So we very many options. Obviously the simplest construction plans are the best. So concrete moulds with steel reenforcement would make quite strong, yet very simple to design, structures. If only we could automate such construction with AI.

C M Edwards · 2002-06-05 11:01:53

Excellent idea, Shaun. Polyurethane foams are great for composite construction, as is styrofoam and similar plastics. With the addition of layers of fiberglass or other plastics, they can be made remarkably strong. You can find how-to directions in books on auto repair, fiberglass, and aircraft composite construction.

Regarding Josh's fear of the plastics freezing, I suspect it would be practical to heat slow cure plastics. As for most thermoset plastics (like two-part epoxy, polyesters, etc.), these produce their own heat through chemical reactions that take place within the setting plastic.

The polyurethane foam fillers that are sold in cans have relatively high compressive strength, which makes a layer of it quite strong when layers of cloth are epoxied to either side. (To break it, one must crush the foam and/or rip the cloth ? not an easy task with fiberglass & kevlar.) Your question about the affect of air pressure is important, though. The vapor pressure limit affects the solvent, not the plastic left behind. But it?s important to note that the ?triple expanding? formulas for polyurethane foams are not as strong as the regular variety because the gas pockets get larger before the foam sets. I suspect that you couldn?t take a can of polyurethane off of the shelf at Lowes? and expect it to work on Mars, because it would expand too much to retain its strength.

CME

A PS for backyard tinkerers: The polyurethane sealer formula sold at hardware stores (the paint, not the foam) is not ideally suited for structural composites because it?s quite rubbery compared to epoxies when it dries. However, it is ideal for rubberizing cloth. For instance, one could apply it to nylon to make an inflatable, air-tight structure.

C.COMMARMOND (FR) · 2002-08-28 13:21:48

Hi all,

This is a very good idea to manufacture (build) objects on Mars but, about plastics, the only way i see to use them at the first time is underground as a kind of concrete. Why?

Because the 'simple' plastics are very sensitive to cold and to UV, both things very common on Mars. Another point is the machnery needed to form 'correct' objetcs from raw plastic. You will need press, for example, to make a seat, you need a 1000 Tons(pressure) press which weigh 10 tons (i saw one working) and need a lot of energy.

But because plastic molecules (methane, propane...) will be created during the sabatier reaction needed to make rocket fuel, we can consider them as 'free' and if we can use them to seal underground structures, it would be fine to be able to use them.

So It is a good and 'easy' to use idea. I'll continue to think about practical details...

CC

C M Edwards · 2002-08-28 20:54:19

Hello CC.

There are a lot of plastics that will be just as difficult to work with as you say. However, polyethylene and polypropylene are not among them.

Neither of these plastics evaporate readily in vacuum, so they can be worked with in the open. Both have relatively low melting points -- around 100C. Rather than pressing them, they can be pooled, drawn or blown like glass.
Special shapes with exact tolerances will require heavy molds, though. And some sort of press will be needed to work the plastic, but to form melted liquid, not solid blocks of plastic.

Polyethylene withstands cold very well. It's brittleness temperature (the temperature at which its strength is reduced by half) is -90C. Polyethylene is also resistant to sunlight and very strong. (High density versions compare favorably to aluminum and kevlar.) It's a common material for children's playground equipment.

Polypropylene is not so good in cold, and it eventually breaks down and turns brittle in sunlight. It's brittleness temperature is just 0C. But it has a unique property: It is almost immune to thermal stress. Changes in temperature do not crack or warp it. Polypropylene pipe can be used for liquid nitrogen, and polypropylene dishes are safe in hot dishwashers where polyethylene dishes would be deformed by the heat.

Polyethylene is useful enough to justify taking some with us when we go to Mars. However, if you absolutely must chose between the two, choose polypropylene. It can be made on Mars directly from the propane byproducts of a Sabatier Reactor, using a second catalyst chamber. This eliminates the need to take a block of it with you from Earth.

CME

C.COMMARMOND (FR) · 2002-09-03 14:53:50

Hi, CM,

you seem to know what you speak about, so i agree with you. The only point i maintain is that it is not easy to obtain shaped (forms ?) or flat plastic from simple machines. I saw the complex machines sold in France for this purpose... I hope you could find simple ones.

CC

Echus_Chasma · 2003-01-11 14:17:10

It can be made on Mars directly from the propane byproducts of a Sabatier Reactor, using a second catalyst chamber.

Doesn't the Sabatier reaction create methane?
Can you create different hydro-carbons using a Sabatier?

soph · 2003-01-11 14:22:49

Plastic is a byproduct of the reaction, which is primarily used for its methane product.

As I was re-reading this I read CC's posts...we could actually use the plastic for underground structures in addition to building the base, which should be the primary use of plastic.

I was thinking that we could build our bedrooms underground. That would add another layer of radiation shielding, add some privacy, and free up our surface area for other uses. The first bases will have to use space wisely.

SpaceNut · 2018-06-20 18:22:56

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#1 2002-06-03 11:59:47

Re: Thermoplastics to Mars - "Manufacturing" the first missions

#2 2002-06-03 14:17:24

Re: Thermoplastics to Mars - "Manufacturing" the first missions

#3 2002-06-04 19:13:27

Re: Thermoplastics to Mars - "Manufacturing" the first missions

#4 2002-06-05 10:46:03

Re: Thermoplastics to Mars - "Manufacturing" the first missions

#5 2002-06-05 11:01:53

Re: Thermoplastics to Mars - "Manufacturing" the first missions

#6 2002-08-28 13:21:48

Re: Thermoplastics to Mars - "Manufacturing" the first missions

#7 2002-08-28 20:54:19

Re: Thermoplastics to Mars - "Manufacturing" the first missions

#8 2002-09-03 14:53:50

Re: Thermoplastics to Mars - "Manufacturing" the first missions

#9 2003-01-11 14:17:10

Re: Thermoplastics to Mars - "Manufacturing" the first missions

#10 2003-01-11 14:22:49

Re: Thermoplastics to Mars - "Manufacturing" the first missions

#11 2018-06-20 18:22:56

Re: Thermoplastics to Mars - "Manufacturing" the first missions

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