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SpaceX Dragon V2

What'south the state of the art in applied materials for space? For case, what would you lot use to make a next-gen space suit? Or the spacecraft that brought it to an exoplanet? For our purposes, let's avoid what's coming over the horizon; nobody wants to read almost vaporware, or the kind of poorly-advised gimmick that looks shiny but ends up killing people. Hither we're just going to cover things that are in active utilize, or at the very least, are beta testing in the field.

There are a few different classes of technological development. Broadly, the recipes we use to make new materials have coevolved with manufacturing methods, and the things nosotros're trying to do with our materials have become much more ambitious. We're courtship ever greater hazards, and we have to reach a corresponding level of mastery over the composition and performance of the materials we use.

There are a couple basic kinds of materials, too. Avant-garde composites layer together separate materials, while alloys melt or dissolve things together to get a homogeneous finished product.

Consider ceramics. The classical definition of a ceramic is an oxide, nitride, or carbide material that'due south extremely hard and brittle, which is to say that it breaks if yous hit information technology with a large enough physical stupor. Ceramics are often strong under pinch, only weak nether tension and shear stresses. Only when ceramic materials are heated until they're as stringy every bit spun sugar and then blown through nozzles into fibers, they tin so exist processed into soft, flexible fabrics like ceramic wool, silica felt, and "flexiramics." These materials just flatly won't burn down, so they're useful when in that location's an awarding for soft, shock-absorbent padding that's also flame-retardant.

Glass-ceramics are a little more familiar to most of us, if by another name: Gorilla Glass, which is normally seen in smartphones today. It's an aluminosilicate drinking glass formed past letting molten glass nucleate around ceramic dopant particles that are only soluble at high temperatures. When it cools, this gets you somewhere betwixt l and 99% crystallinity, according to Corning. The resultant material is very little similar a glass except for its transparency. When tempered, the rest between tension and compression makes the stuff tough as hell. Glass-ceramics also play well with electrically conductive coatings, and engineers use that feature on spacecraft windows to keep them complimentary of condensation and ice.

Material Chemistry

Spacecraft windows are a great application of materials science. I way of making space-worthy windows is fused silica, which is 100% pure fused silicon dioxide. Another crazy window material is aluminum oxynitride, which is actually a transparent ceramic we use to make things impenetrable. In a video produced by i manufacturer of aluminum oxynitride bulletproofing products (see beneath), 1.half-dozen inches of AlON was sufficient to completely stop an armor-piercing .fifty cal round. AlON and fused silica both kickoff out equally a fine powder chosen frit, which is tamped into a mold so only broiled at the almost unearthly temperatures into a single piece of transparent, super-hard material.

Unless you're working with 100% pure substances, which in many cases isn't possible, the thought of doping is central to all of this. Doping means calculation a pinch of something special to an otherwise mundane recipe, to take advantage of the special affair's benefits without dealing with the flaws information technology has when pure. In many cases, what results from doping ends upward bearing little resemblance to either of its parent materials.

Metallurgy relies a lot on doping, which in this instance is called alloying. There are some pretty fantastical things we tin practice with metals. Aluminum-niobium alloys accept cook temperatures high enough to withstand the thermal surroundings inside the Falcon 9's engine nozzles. But it'due south merely considering they also use regenerative cooling: propellant cycles through chambers in the nozzle walls, cooling the bell and warming the propellant. (It'south a heat pump.) Alloys involving gilt and contumely are useful because they just will not corrode, no matter the temperature or chemical farthermost. Like the anti-caking additives in Parmesan cheese, there even exist metal alloys that involve silicon only because the silicon makes the molten metal flow more readily, and therefore better suited to circuitous casting.

Friction-stir welding, which physically melts together the ii materials existence welded so that they become one structural entity, solves the problem of joinery for some of SpaceX'due south aluminum-alloy parts.

Image credit: Nature.

We encounter novel cloth chemistry a lot in semiconductor inquiry, and lately control over the dopant has go fine enough to introduce single-atom point flaws into a diamond lattice. This manufacturing precision is also critical to so-called "high-entropy" alloys, which are hybrid mixtures of 4, five, or more than different elements that tin can yield tremendous gains in toughness, as well as making things made from them thinner, lighter, and more durable. A metallurgist from MIT has made a high-entropy steel-like alloy that's both extremely hard and highly ductile, which are characteristics that I and anybody else thought mutually exclusive.

Of grade the choice of dopant is important. Tantalum and tungsten are hard, dense, radiation-resistant metals that were stirred into the titanium to make Juno's "radiation vault." The vault protects the delicate circuitry in the science payload, sacrificing itself to embrittlement so that the electronics tin live as long equally possible.

Radiation hazards can exist mitigated with shielding — basically, putting atoms between your payload and the high-energy charged particles that can flip $.25, corrode metals, and curt out connections. Atomic number 82 is the obvious choice on earth, just atomic number 82 doesn't work for space flying, because it's as well soft to withstand the vibrations and too heavy to be applied in any case. That'southward why Juno'southward radiation vault is mostly titanium; information technology's tougher than aluminum and lighter than steel.

It'due south really a major problem, trying to figure out how to keep electronics running as long as we can while they're in space. You can't make a spaceship without a computer in it. And while we keep making circuits smaller and keep cutting their ability requirements, at a certain point there are physical floors of size and power consumption. Almost those thresholds, information technology's exquisitely easy to perturb a system. Radiation damage, thermal differentials, electric shorting, and physical vibration all pose hazards to electronic circuits. Spintronics could aid to advance computers, providing much greater computing bandwidth for use doing whatever you lot'd need to practise on an interstellar voyage. They could also put a hard maximum on the EM hazards that are so damaging to electronics in an intense magnetic field, similar the i around Jupiter. Only until we make optical circuits or spintronics real, we're going to have to effigy out how to brand good old electronics behave in space, and that'll probably involve a good old Faraday cage.

Composites

Composites are tough to produce because they often crave extremely specialized manufacturing facilities, huge autoclaves and the similar. Just when they're proficient, they are very, very expert.

Multi-layer insulation (MLI) is both thermally and electrically insulative, and NASA uses the stuff practically everywhere they tin. MLI is what makes spacecraft expect like they're covered in gold foil. But there's a kind of MLI for applications where the whole shebang needs to be electrically grounded, as well, and that uses a metal mesh instead of the tulle-similar fabric mesh between its layers of foil.

SpaceX uses rigid composites in their vehicle structure, layering together carbon fiber and metallic honeycombs to produce a structure that'southward both very light and very stiff. Foams and aerogels can practice lightweight, rigid, thermally impermeable layers too.

After retrieval, this is what the fairing from the Falcon 9 looked like. Note the carbon fiber wrap sandwiching the metallic honeycomb.

Later retrieval, this is what the fairing from the Falcon ix looked similar. Note the carbon fiber wrap sandwiching the metallic honeycomb.

Composites excel against concrete hazards and stressors, but rigid materials aren't the only manner to get. The Axle inflatable space hab module, which I affectionately telephone call a bounce castle in a can, is fabricated of flexible composite materials including a unique glass fabric called beta cloth. NASA and others have been using beta cloth and things like it since the late 90s, and for good reason: The stuff is just incommunicable to faze. Made of PTFE-coated glass fibers in a handbasket-weave fabric, it's the love child of fiberglass and Teflon. Information technology's practically impossible to cut or even scratch with the hardest, sharpest blades. Because it'southward flexible, it's impact-resistant. It's impervious to corrosion even by free atmospheric oxygen attack. Scientists shot it with lasers and that'southward what finally made it starting time to degrade.

Like to beta cloth, at that place's also the flexible Chromel-R metallic material, which we use in chafe-resistant patches on spacecraft bodies and space suits. Chromel-R is like the woven glass mats of beta cloth, but made of hard, coated metal wires. Furthermore, scientists constitute that the "stuffed Whipple shield," which is a layered confection of ceramic-fiber material and Kevlar, worked better than aluminum plating to stop hypervelocity ceramic pellets simulating infinite droppings — by melting or disintegrating the pellets (PDF).

Infinite suits are actually the perfect application for flexible composites. No unmarried material is resistant to everything. Only if you sandwich together thin layers of several materials that are each resistant to most things, you lot go an everything-proof exo-suit that tin notwithstanding curve and flex with the wearer. Add a layer of Darlexx or similar, a la SpaceX's next-gen infinite suits, top it off with a layer of flexiramic cloth, and you have a fireproof force per unit area suit. Put a layer of non-Newtonian fluid cushioning and some ceramic-blend trauma plates in there too, and at present information technology's fireproof body armor. All you need then is a HUD in your helmet, and maybe some loftier-density memory cream in the seat cushions. This is stuff we could do but with products bachelor today.

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Superlative image credit: SpaceX Dragon V2 interior