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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."
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'.
Is it transparent?? Plastic usually is/can be. Perhaps this is what they really meant by transparent aluminum. We should really make sure none of this time's whales have been recently stolen!
Why, no I didn't read tfa.
Plastics.
You can toss your spaceship in the blue bin for curbside recycling!
NASA has developed a way to toughen the polymer into a product they call RXF1 which is 'even stronger and lighter than aluminum'.
Yeah, and polyester hats should be much more fashionable than the tin foil ones.
In theory there is no difference between theory and practice. In practice there is. - Yogi Berra
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.
Sorry to bring you up there, but my system weighs around 40kg now with the fluid cooling and it's anything but portable; even If I could work off with it, It'd rip the IEC out of the UPS after 4 feet.
Ripping an new rectum in the fabric of spacetime.
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?
Circumcision is child abuse.
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.
Like the saying goes, never underestimate the bandwidth of a station wagon full of tapes. -Pyrotic
There is no risk to you.
Nobody is asking you to go to Mars and it just so happens that some people still have the spirit of exploration and adventure and will volunteer to go knowing the dangers involved. (I know this to be true because I would raise my hand for the chance).
If America can't find someone to volunteer and do it for the spirit of exploration, China, a few years later will order someone to do it for prestige.
Ripping an new rectum in the fabric of spacetime.
RSS URL is feed://science.nasa.gov/podcast.xml, smartass
I am subscribed with the iPodder app. Again, how is this not a podcast?
--- Eat my sig.
Just taking a look at TFA, it's quite clear that this is a link to an audio file (actually an M3U PL) rather than any mention of a podcast.
This would suggest the file is intended for listening by anyone, anywhere with a Mpeg 3 player thethered or not.
It seems that the term podcast in this case was applied solely by the submitter to Slashdot.
Ripping an new rectum in the fabric of spacetime.
But most architecture just isn't that sensitive to weight. For example, steel frame houses have significant earthquake resistance and are just more durable overall. Most bridges cover modest spans and can continue to be steel and concrete. Further one has to consider the problem of wind force. If your structure is very light for its surface area, then it'll experience increased jostling due to wind. Then you need to engineer some sort of means for stabalizing the structure, maybe guy ropes or some sort of internal computer-controlled weight that counters these motions.
I'd want to see how the material handles long-term exposure to vacuum and large temperature swings before using it in any space-borne structural applications. Most plastics contain plasticizers that help improve flexibility and handling properties, but which slowly evaporate leaving the material brittle (anyone ever see what happens to a plastic milk jug left in the sun for a year?). Moreover, plastics tend to have structural properties that are very temperature sensitive -- at modestly high temperatures, plastics slowly stretch to failure, at modestly low temperatures, they fracture. The "temperature" in space is strongly dependent on whether the surface is facing the sun or not. It's baking hot on the sunny side and freezing cold on the shady side -- not a good environment for plastics.
The history of material science is the history of failures such as the catastrophic failure discovered in Liberty ship hulls in cold North Atlantic waters (learning that some steel alloys are brittle in low temperatures) to the Comet airplane crashes (learning that aluminum fatigues from repeat cycles of stress). I can only hope that NASA does something like LDEF with this material before depending on it to hold its properties for several years of space-exposure.
Two wrongs don't make a right, but three lefts do.
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.
Your design to a real part online: Big Blue Saw
Actually this is going to make spacecraft a lot cheaper. NASA will be producing future vessels in kit form with components attached to a large plastic framework. Construction will be a simple matter of twisting off the right parts and gluing them in place.
Mars atmospheric entry won't be as big a heat problem as earth entry, because of how thin the atmosphere there is. If the plastic was resistant enough for that (which it's still probably not) then they could simply re-enter earth in something else, and leave the spacecraft in orbit, ready for another mission perhaps.
Polyethylene is almost never transparent because it crystallizes very easily with its nice simple ...-CH2-CH2-CH2-... backbone. The resulting microcrystals scatter light and make the stuff milky. If you want transparent polymers, you use a backbone structure that doesn't easily form crystals, for example polystyrene, where the big benzene rings tend to jut randomly left or right out of the backbone.
I would guess that their new form of PE is a variant on long linear PE, with reduced branching of the CH2 backbone. This is going to have an even greater tendency to form crystals (Indeed, the crystals may be an essential part of the high strength feature, because they tie different PE chains together.) So I very much doubt it would be transparent.
No metal can ever be transparent, Star Trek IV notwithstanding, because to be a metal is to have free electrons, and free electrons absorb a broad spectrum of light. Put it another way: if you're a metal, you're a conductor, or equivalently an antenna, and that means you absorb electromagnetic radiation, i.e. light. So you can't be transparent.
I understand one of the disadvantages composite materials have, besides the fact that they cost more and are generally harder to work with, is that their aging and failure modes are hard to predict. If you build airplane or spaceship parts out of metal, you can do small-scale short-time testing of the material and accurately predict the lifetime of the part, its probable failure mode, how its properties will decline as it ages, and the warning signs of imminent failure.
This is not true for composites. Accurate theory to scale up small and short tests to the full design lifetime does not yet exist. Furthermore, composites tend to fail all at once, without warning, and sometimes in response to stresses that previously they easily withstood.
Recall the RSS panels on the Space Shuttle, which failed in Columbia and in the CAIB test under surprisingly small impacts. This is not, I think, because the original engineers had their heads up their asses and didn't design for an impact with a bird or some such. I suspect it's because these composite parts are now 25 years old, and subtle changes due to aging have ruined their original design impact resistance, and have opened up unsuspected new failure modes.
In other words, one of the big virtues of metals is that they are much simpler materials, and the ability to predict the performance of your material accurately is a nontrivial criterion in selecting it.
While plastics are incredibly useful and durable .. from a chemical point of view... I'm much less likely to trust them in terms of long term stability.
I've seen these things dissolve in the slightest bit of an organic solvent (e.g. Dichloromethane or acetone)... and seen them melt with a souped up hairdryer (heatgun) at less than 200 degrees C. I wouldnt feel particularly safe with these materials shielding me from one of the harsher environs known to man (space).
Maby it's just my experience of seeing these substances take damage a lot, but i'd be real uneasy to trust my life to them over a bar of aluminum, which you can easily dip in water/organic solvents and heat to rediculous heats without so much as loosing it's bright metallic glint, let alone the all important structural integretiy.
If they're going to use plastics as a main part of the airframe, they're definately going to have to do some shielding from heat/radiation (U.V. light by itself can be quite destructive to certain plastics).
As frequently happens with NASA tech, I expect this will make its way into the private sector.
How long will it be until they're packaging our scissors, walkmans, and USB hubs in this stuff? You thought those packages are hard to open NOW!
-- I prefer the term "karma escort."
Neutrons are the bad boys. They don't have a charge like protons (alphas) and electrons (beta) so they aren't easy to stop. What makes them nasty is that they are massive and can do some real damage.
Poly (and water) make the best neutron radiation sheilding because it has alot of hydrogen atoms (one proton nuclei) which when hit with a loose neutron, will cause the neutron to loose 1/2 it's energy (two equal mass objects remember). So after a few collisions with a few Hydrogen nuclei (protons), the Neutrons become slow enough to be absorbed into any handy atom's nucleus (hopefully NOT in your DNA)
THAT's why they use Poly sheilding in space craft.
Your thin skin doesn't make me a troll
So this stuff is a fabric, so the implausible tensile strength numbers are probably for the individual fibers, not for a solid piece of the material. (The photo has him holding a "brick" of the material though.) Spider silk is as strong as high strength steel, and is very tough, but no one is suggesting building spaceships out of it. 2.6 times less dense than aluminum gives it about a density of 1, which is what polyethylenes typically are.
So they've managed to build a tough fibrous material. That's good, and it might make for a good micrometorite shield, and possibly a radiation shield. But it's not going to be a replacement for steel, titanium, or aluminum.
The radiation safety field has been using plexiglass (polymethylmethacrylate) as shielding against high energy beta particles for decades so its not very surprising that another polymer of a similar type can be used to shield against intrastellar particles of a similar type. The thing to understand is that although they liken the structure to that of a garbage bag, the higher the energy of the particle, the thicker the material needs to be and since those particles have very high energy in space, it is likely you are going to have a ten foot thick garbage bag as your shielding in future space ships...
...and it should be known by now
It's an allusion to http://www.imdb.com/title/tt0061722/ (The Graduate).
If you haven't seen the movie, shame on you.