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NASA's Orion spacecraft

Space--an Eternal Frontier


By —— Bio and Archives--April 20, 2018

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Space--an Eternal Frontier
From astronomers to futuristic dreamers, the inter-stellar space is the real frontier—for many centuries already.

Anyone who’s looking at the firmament on a clear summer night is likely to agree. There is a “world” of stars, planets, moons, galaxies, and a host of other—mostly unfathomable—objects out there. One can’t deny that.

However, is that a “good enough” reason to spend mega-bucks on trying to “conquer space?”

Conquering “Space”

Even with all the available super-computer power and far-reaching telescopes, we still have “surprise” asteroid fly-by’s). Occasionally, these asteroids are not just little pieces of rock but football field-size objects. The most recent one, dubbed 2018 GE3, was estimated to measure 157 to 360 ft. (48 to110 m), making the object about 3.6 times the size of the one that leveled 500,000 acres (2,000 square kilometers) of Siberian forest when it exploded over Tunguska (Siberia) in 1908. This latest (in astronomical terms) “speck of dust” took less than a day from being discovered before it reached its closest distance to earth. Not entirely surprising with their typical speed of 50 miles per second. Passing by earth at a distance of 120,000 miles, in astronomical parlance, it was a “close call.”

Now, what does that have to do with inter-planetary or even inter-stellar travel? Among other things, there exist requirements for a host of very special materials.

Material Requirements

Actually, I find it rather hilarious when NASA now thinks that “plastics will save their bacon”, as I see it. As the article states:

“A spacecraft built using more than 100 3D-printed parts could be about to change that. At some point before 2023, NASA’s Orion spacecraft will take a crew of up to four astronauts on a test flight further than humans have ever travelled before. The spacecraft, which will launch atop the most powerful rocket ever built, will circle our planet twice before looping around the Moon and flinging itself back home,” and

“The material is also designed to minimize the risk of anything going wrong with the spacecraft’s electrical systems, says Sevcik [Scott Sevcik, VP of manufacturing solutions at Stratasys]. To get around this, his team added carbon nanotubes that help dissipate the static charge that builds up in the plastic over time, minimizing the risk of nasty electrical faults developing in the middle of a mission.”

The latter point may indeed be a plus for “plastics” as the can easily accumulate high electrostatic charges. That’s especially noticeable in dry winter air when walking across a carpet and touching a metal object, like a door handle; one gets a good electric zap. However, for the novel carbon-infused plastics there are other considerations too, and they are definitely reasons to think twice about such materials. One of the most obvious ones is the lack of stability of nearly all plastic materials. I suspect that most readers may be familiar with their inherent problems, perhaps without recognizing the exact cause. Such problems include increasing brittleness and shrinkage over time; let me explain.

Shrinkage of Plastics

Once in a while, a set of calipers is handy to have for measuring the inside or outside dimension of pipes, the depth of a small hole and so forth. Even in the chemical laboratory I found the Vernier calipers useful.

Vernier calipers;

 Vernier calipers

Of course, such precision instruments, made of high-grade steel are not to be had for next to nothing. When I saw one made of plastic but otherwise looking close enough to the real thing and at a cost of next to nothing, I bought it. That was perhaps two decades ago.

I didn’t need a high precision instrument calibrated to the umpteenth decimal point of accuracy but have an occasional need to know whether a pipe was 2” OD or 2” ID and the like. This cheap plastic gadget is still useful for this purpose. Now, after many years, I noticed one curious thing: The end of the metal wire on the back side (part #3 in the picture), attached to the sliding part (#6-8 in the picture) is no longer flush with the end of the instrument as it used to be when new. In fact, it now protrudes nearly 0.1 cm from the end. What’s the explanation? As I surmise, clearly, a case of shrinkage by the plastic.

 

Continued below...

Of course, metal expands with heat and contracts in cold. However, in contrast to plastic materials, for metals, this is a fully reversible process. Plastics will also expand and contract with temperature changes but never make it back all the way to their original shape and dimensions. They also keep shrinking for a long time. Perhaps you know of a floor with plastic, like polyvinyl chloride (PVC) floor tiles of some age. When originally laid down with care, one couldn’t see any obvious spaces between the tiles. A couple of decades later, there are noticeable spaces between the tiles.

Developing Brittleness

Another problem with many plastic materials is their developing brittleness over time. That’s primarily caused by volatilisation of softening agents (plasticizers) and additional polymerization of the plastic’s molecules. The latter is especially fostered by elevated temperature and by high energy, e.g. UV type radiation.

For some plastics, that effect can be prevented or at least slowed down by addition of polymer stabilizers, substances that act as antioxidants and as photon absorbers. However, not all plastics can be stabilized in that way. For example polypropylene type materials that are widely used in ropes are particularly prone to degradation upon exposure to UV light.

Another Theory

Now, I do want to mention another (theoretical) explanation for the apparent shrinkage of plastics, namely the possible expansion of planet Earth. It was described in several booklets and videos by Richard Guy. At least one of my friends subscribes to that theory and, if increasing property tax bills are related to an expanding earth, he certainly has a point.

Perhaps I’m simply too old-fashioned but, on balance, I still think the shrinkage explanation of plastics is more realistic.


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Dr. Klaus L.E. Kaiser -- Bio and Archives | Comments

Dr. Klaus L.E. Kaiser is author of CONVENIENT MYTHS, the green revolution – perceptions, politics, and facts Convenient Myths


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