What Materials Keep Satellites Safe in Space?
Right now, nearly 5,000 satellites are orbiting the Earth, taking pictures, transmitting data, and collecting information both about our world and the space around us. Every one of these satellites faces the brutal environment of outer space — from extreme heat and cold to radiation and space dust. What goes into creating one of these satellites, and what materials keep them safe from the harshness of space?
Engineers need to build satellites out of materials that don't expand or contract much due to temperature fluctuations, which occur frequently in orbit. While space itself is cold, satellites are moving in and out of direct sunlight, which rapidly increases or decreases their temperature. Materials that greatly expand or contract in response to these swings wouldn't survive long.
Within Earth’s atmosphere, temperatures remain fairly comfortable — around 50.3 degrees Fahrenheit or 10.17 degrees Celsius. Your phone might suffer a little at 50 degrees, but it will still function. The problem is, these devices don't stay at 50.3 degrees F, even if they're in near-earth orbit. As soon as they move out of the upper atmosphere, nothing protects them from the brutal cold of space — or the unfiltered solar radiation coming from the sun. In full sun, the temperature can climb to 248 degrees Fahrenheit or 120 degrees Celsius, and in the shade, it can drop to -148 degrees Fahrenheit or -100 degrees Celsius.
Further out, the temperature drops to near Absolute Zero — -457.87 degrees Fahrenheit or -270.15 degrees Celsius.
Satellites are also traveling at anywhere from 7,000 to 17,500 miles per hour, which means they have to withstand immense g-forces and potential impacts with other objects. And of course, they have to be light enough for rockets to get them off the ground without expending too much fuel or increasing costs.
Aluminum or Titanium?
With the substantial amount of materials available, only two metals make the cut when it comes to protecting satellites and other spacecraft — aluminum and titanium. As titanium is much harder to mine and fabricate, most satellites are made of aluminum and its alloys. Aluminum is lightweight, durable, and relatively cheap.
The metal is even used to insulate satellites in the form of aluminum-coated polyimide. The polyimide layer surrounds the exterior, with the aluminum side facing inward. The polyimide is gold-colored, giving the exterior of many of these crafts that iconic gold shimmer even though there's no actual gold in the insulation. It also includes layers of fiberglass, spacers, silver and beta cloth to improve the material's overall insulation capabilities.
Protecting the Exterior
Protecting the exterior of the satellite is vital. Most satellites don't have paint, especially since paint chips in orbit can move so fast they can damage other spacecraft and satellites — this may have been what damaged the ISS' window in 2016.
Powder coating, which adheres a powder to the exterior of an item with electrostatic energy before the finished coating is baked into place, could be an option. Plus, when compared to painting, electrostatic powder coating reduces project waste by 95% because unused powder coat can get reclaimed and reused. Powder coating, or other similar exterior coatings, protect the aluminum from the harsh environment it will encounter once it leaves our planet's atmosphere.
Other Materials in Play
Graphite, boron, carbon, fiberglass, Teflon, Kevlar and many other materials all work together to create a fully functional satellite.
Both graphite and Teflon can be used as dry lubricants to keep moving parts from rubbing together since, in the vacuum of space, you can't rely on liquid lubricants because they'll boil away. Some manufacturers are turning to carbon in the form of carbon fiber because it is both durable and lightweight, reducing the cost of sending these satellites into orbit.
Kevlar — the same material you'd find in bulletproof vests — serves as shielding for both satellites and the International Space Station, protecting them from meteors and space junk that could damage or destroy them.
Most of the satellites that will get launched in the next few years will all feature an aluminum frame because it is lightweight and durable enough to survive both launch and life in outer space. We'll have to see what new technologies NASA and its engineers come up within the coming years to make these devices even lighter and stronger.