In Star Trek IV: The Voyage Home, one of the biggest obstacles the crew faced in their mission to bring back a couple of humpback whales from the 1980s was converting the interior of a Klingon Bird of Prey to carry the whales. The crew decided on building a holding tank out of plexiglass, which Scotty procured by trading the formula for transparent aluminum. The material – a one-inch slab of which could replace a six-inch slab of plexiglass – was complete science fiction until just a few years ago. Now it’s looking like transparent aluminum will soon be making its way to the battlefield.
Far lighter and stronger than traditional “bullet-proof” glass, transparent aluminum armor could replace the heavy panes currently used in combat vehicles. The actual transparent aluminum part of the armor is made of aluminum oxynitride, a mixture of aluminum, oxygen, and nitrogen that starts out as a powder. The powder is molded, baked at a high heat, then liquefies and cools quickly into a solid. The resulting crystalline structure of the solid is loosely configured (like a liquid) but extremely rigid, giving it a “level of strength and scratch resistance that’s comparable to rugged sapphire.” That’s pretty tough, but it isn’t transparent (or its fully strength) until the final solid gets a good polishing. The highly polished, clear ceramic is combined with a layer of glass and a polymer backing to make a transparent armor capable of withstanding .50 caliber armor piercing bullets at half the weight of traditional transparent armor.
Unfortunately, in this case, thinner, lighter, and better also means (3 – 5 times) more expensive. Proper facilities and technology to handle making large enough sheets of transparent aluminum armor for windshields and so forth are lacking. As transparent aluminum becomes more commonplace in semiconductors and barcode scanners, though, the price of production could come down and we might see this bit of Star Trek tech popping up more often.