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Down-to-Earth Uses for Space Materials
Popular mythology has connected many familiar products such as Tang, Teflon, and Velcro with the space program. In actuality, none of these was specifically developed for space applications; but the persistence of these myths suggests a general conviction that space exploration has yielded tangible benefits for day-to-day life on Earth. And yet, many people might not even recognize commonplace materials that did, in fact, derive from the space industry.
For example, in the early 1950s, a small firm known as the Rocket Chemical Company sought to create a line of rust prevention solvents and degreasers for the aerospace industry. One product of this effort can still be found in most homes today—the lubricant WD-40. The name is an abbreviation of Water Displacement Formula #40, because it reportedly took 40 tries to get it right. Convair, an aerospace contractor, first used WD-40 to protect the outer skin of the Atlas missile from rust and corrosion; but engineers quickly realized the material would prove equally useful around the house. Today, few people are aware of its space-race roots.
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The lubricant WD-40 was originally developed for the space industry. The original package is shown on the left. Photos courtesy of WD-40 Company | |
Viscoelastic polyurethane foam, popularly known as memory foam, was developed in 1966 by Stencil Aero Engineering Corp. under a NASA Ames contract for crash and vibration protection for the Apollo program. Under sudden impact, the foam deforms, releasing energy in the process, then slowly returns to its original shape. Over an extended period of time, the foam "senses" body temperature and weight, conforms to the shape of the body, and provides the perfect amount of support—especially during periods of increased g forces, such as liftoff and reentry.
The first company to market the foam soon moved beyond aircraft seating to medical applications, which today account for some 80 percent of sales. Because of its open-cell structure, the foam permits easy removal of moisture from the contact area, thus making such applications as seating and mattress pads, as well as molded cushions, especially effective. The properties that have made viscoelastic foam successful in medical applications have made it equally successful in veterinary medicine—in prostheses, braces, and splints.
The foam continues to serve for shock protection—its original application—in the automotive industry. The foam has even found its way into saddle pads for horse racing. Other sporting applications include rafts that will not sink when punctured and archery targets that "self-heal." The stiffest foams are also finding their way into bulletproof vests and personnel carriers that may be exposed to land mines and roadside bombs.
WD-40 and viscoelastic foam are just two examples of useful materials that were specifically developed for space applications; but equally important are the materials that were available, but not commercially viable, until the space industry took an interest in them.
Titanium is a case in point. Twice as strong as aluminum, half as heavy as steel, resistant to heat and corrosion, and abundant in nature, titanium was highly sought by a burgeoning aerospace industry. But titanium never appears naturally in its pure state, and is difficult to process. Only after an extensive effort, partly fueled by aerospace interest, did large-scale production and use as a structural material become possible. Titanium has been a significant enabler of space exploration: the Mercury, Gemini, and Apollo capsules were largely made of it, and the space shuttle and the International Space Station have many titanium parts. Closer to Earth, it's widely used in aircraft for firewalls, outer skin, landing-gear components, hydraulic tubing, engine supports, and the housings of jet engines.
Titanium's corrosion resistance made it especially useful for naval applications, especially propellers and shafts. This same corrosion resistance and lack of toxicity made titanium the metal of choice for medical applications; most artificial joints, dental implants, and prostheses are built on titanium bases. Titanium has also found its way in to a number of sporting products, like golf clubs, fishing poles, and football helmets.
Another Apollo-era technology that has found terrestrial applications is metallized plastic film. The first large-scale application of this technology was in Echo I, launched in 1960. Echo, the first passive communications satellite, was essentially a huge balloon of aluminized Mylar polyester film. While metallized plastic films had been produced for decorative purposes on a small scale for years, the market was limited before the aerospace industry took an interest.
Echo I, the first passive communications satellite, was essentially a 30.5-meter balloon of aluminized Mylar polyester film. The material is now widely used. NASA |
Researchers soon produced a double-sided fabric for the manned space program that became NASA's most widely used insulator. This radiant-barrier technology was initially designed to protect against the intense heating of reentry, but soon found applications on satellites in orbit, in space suits, and around sensitive instruments. The orbital environment experiences temperatures ranging from nearly absolute zero to more than 260°C; conventional insulation on a space suit would have required a layer 2 meters thick; clearly, the radiant-barrier material has been a real enabling technology for the space program.
Terrestrial applications were rapidly developed—most notably, the "space blanket" that weighs a few ounces and reflects and retains 80 percent of the user's body heat. Its insulating properties are life-saving, and its small size makes it perfect for emergency kits. Single-sided metallized tear-resistant fabrics are used for all-weather clothing, enabling the wearer to retain heat on cold days and reflect sunlight on hot days. Radiant-barrier fabrics are also widely used in protective apparel for firefighters.
Metallized films in stiff laminates have found their way into home, office, and industrial insulation, in awnings and canopies. They provide insulation around water pipes for sprinklers and irrigation. They protect food in picnic coolers, pizza-delivery boxes, refrigerated vans, and railroad cars. The technology appears in automobile firewalls and in such specialty applications as candy wrappers, thermos bottles, and auto windshield inserts.
Another intriguing material that got a boost from the space industry is the rheological fluid, which stiffens under magnetic or electric fields. The so-called "smart fluids" in this category can be controlled to provide damping and shock absorption.
The first magneto-rheological fluids—essentially suspensions of iron particles—appeared in 1947. A tendency for the particles to settle out hindered their early development, but they did find some application in auto transmissions in the 1950s and in the Apollo Service Module in the 1960s. Interest ebbed for several decades, but with the commercial availability of stable formulations and faster control circuits, interest exploded in the 1990s. Smart fluids began appearing as resistance brakes in exercise machines, and show potential for use in athletic footwear. They're also making a big impact in automotive-suspension technology, offering a significant reduction in mechanical parts and the ability to change levels of shock and motion 500 times per second. Magnetic smart fluids also offer actuation by wire, which could help reduce the weight and complexity of car steering, braking, clutching, and shifting mechanisms.
In architecture, magnetic smart fluids are used to stabilize high-rise buildings and bridges against earthquakes and high winds. They serve as low-friction seals for rotating shaft motors in x-ray generators, and can also be found in high-speed computer disk drives and in loudspeakers, where they dampen unwanted resonance and dissipate excess thermal energy.
Few materials in NASA's current arsenal are more exotic than silica aerogel. Sometimes known as "solid smoke," silica aerogel is the world's lightest solid substance, with some grades weighing 0.003 grams per cubic centimeter. Silica aerogel is essentially a microscopically fine foam of pure silica; composed of 99.9 percent air, it's an effective insulator that can withstand temperatures up to 1400°C. Strong enough to support many times its own weight, silica aerogel is also the best solid dielectric known and a promising candidate for integration onto ultrahigh-speed microchips.
Silica aerogel became the star of NASA's Stardust mission, capturing particles from a comet's trail. The material is finding terrestrial applications in insulation. NASA |
Silica aerogel was first produced in 1931, but received scant interest outside the laboratory. Decades later, the French space program began investigating the possibility of using aerogel to store rocket fuel. NASA had begun its own research program, and eventually made aerogel the star of its Stardust mission (1999–2006), where it played a critical role as the only known substance that could trap microscopic cometary particles traveling at 6 kilometers per second without damaging them. Its lightness and unequalled insulating properties made it a key part of three Martian rovers.
While the cost of silica aerogel is too high for most terrestrial applications, the material does appear in some commercial products—most notably, in insulating fabrics. Aerogel-based insulated windows could provide a large market, if engineers can find a viable way to manufacture clear aerogel. So far, clear aerogel remains tantalizingly out of reach. Processing aerogel in Earth's gravity causes both irregularly sized and irregularly distributed pores, giving aerogel its characteristic bluish, hazy, smoky look. Experiments in airplanes and in orbit suggest that a more uniform, clear product is possible. Such a product would revolutionize aerogel marketing.
While silica aerogel may be the lightest known solid material, carbon nanotubes are certainly the strongest. Carbon nanotubes derive their remarkable strength from the carbon-carbon covalent bonds that make a nanotube essentially a single molecule. One-sixth the weight of steel, but a hundred times stronger, the material could conceivably replace metals in many structural applications. As "quantum wires," carbon nanotubes could conduct electricity 10 times better than copper—at a fraction of the weight. But the market is still looking for the breakthroughs that will generate continuous fibers efficiently and at a reasonable cost. In 2005, NASA offered an $11 million grant to Rice University to develop a carbon nanotube power cable, hoping for a 1-meter-long prototype by 2010. If the project succeeds, carbon nanotubes could become the biggest thing to hit the market since Teflon and Velcro.
