Fly To Mars In A Plastic Ship

saskboy writes "NASA reports that an old polymer may be the spaceship material of the future. Polyethylene is in household garbage bags, and it is also an effective solar radiation shield. I learned three years ago in astronomy class that polyethylene is used in the sleeping quarters on current orbiting space vehicles, but now NASA has developed a way to toughen the polymer into a product they call RXF1 which is 'even stronger and lighter than aluminum'. As you may know, radiation in space is currently a major obstacle to manned missions outside of the Earth's magnetic field, so better radiation shielding is essential to planned manned missions to Mars and beyond. Get the mp3 podcast of the article here."

Comments

Metals are becoming obsolete

[Sir Homer]

With carbon fiber being as strong a steel at a fraction of the weight, and plastics that are bulletproof, and it becoming more and more likely that polymers will be used to build next generation cars, bridges and buildings as well as spacecrafts.

But what's the point?

[Stormwatch]

No, seriously, what's the point of a manned space flight to Mars? What can they do that robots can't? Is it really worth the cost and the risk?

Nasa

[3.09 a hour]

Why in Bush's name are we cutting fuding to nasa? After this alumna-plastic and http://www.jpl.nasa.gov/news/features.cfm?feature= 490 aerogel, seems to me they are doing cutting edge USEFULL research.

Re:Plastic aluminum?

[sdpuppy]

I wouldn't be surprised if the main structure could be plastic, with a thin(ner) outer shell of some metal. You get the heat (and tinfoil :-)) shielding from the outer shell but most of the strength would come from the plastic.

If I were designing that thing, I'd put a space between metal shell and plastic - then you have insulation (or a thermos - open the valve in space to evacuate. :-))

Unless we run out of oil!

[FatSean]

Then we'll be mining those landfills...which sounds like an easier job than mining metals.

All sorts of weird future scenarios come to mind...a world where disposable utensils are made of glass or metal or something...because we need the polymers for more important things.

Polyethylene

[chroma]

Polyethylene is one of the most commonly used plastics in the world, and is found in plastic grocery bags, cutting boards, milk jugs, disposable cups, and about a million other things. It's very stretchy, and thus is unlikely to break. It's tough, so that when it gets a hole or crack, the structure keeps its integrity. That's why I use it for armor on my fighting robots.

According to MatWeb, Ultra High Molecular Weight Polyethylene (UHMW-PE) has an ultimate tensile strength of about 40 MPa, while 7075 alloy aluminum has an ultimate tensile strength of 524 MPa . The article claims that this new PE-derived material has a tensile strength 3x that of aluminum. I find a 40x improvement in tensile strength a bit tough to believe.

Re:Plastic aluminum?

[Rei]

Well put, although geometry can throw a wrench into the issue (people don't fly around in nice spaceworthy two-layer spheres :) ). My biggest problem was with the intro:

Polyethylene is in household garbage bags, and it is also an effective solar radiation shield

No, it isn't. It's an effective GCR shield, not an effective solar radiation shield - for solar radiation, you want high Z.

Would you, perchance, have seen a study that actually for once addresses bremsstrahlung doses with more than a passing mention? Every time I see a study on radiation exposure for a Mars mission, after long detailed calculations on what would be needed to meet minimal health standards, there's usually a couple of lines to the effect of "These calculations do not include the effect of bremsstrahlung radiation, which can be expected to significantly increase the total radiation dosage." All of the studies I've seen use incredibly simplistic models (often a 1d radiation source impacting perpendicularly to a one or two layer shield).