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We rely on satellites and structures in space for communications more than ever before. They help provide us with television pictures, telephone calls and a wide variety of communication signals, whilst surviving the hostile environment of space. Artificial satellites are able to complete these tasks and endure in space thanks to the unique materials used to create them.
The materials used in space are, more often than not, the most advanced materials that humans have created and we are constantly researching and creating new and improved materials. These materials need to possess a number of unique properties to be effective in space.
The Properties Materials Need to Function in Space
An object that is continually moving in and out of the sun’s direct heat is in constant temperature flux, which can cause it to expand and contract. As a result, scientists consider a material’s ability to maintain its size and shape despite temperature changes, which is known as dimensional stability.
Structures in space also need to be able to withstand its uniquely harsh environment. This is considered a material’s environment stability. In space this means that the material can remain stable in despite the presence of radiation and the vacuum of space.
The most important properties of a new material which will be used in space are strength and stiffness. When an object is in orbit around the Earth it will be subjected to incredible forces that will tear apart weaker structures.
The launch alone can put a material under up to three times the force of gravity, meaning that each component will weigh up to three times as much as it would on Earth. The material must maintain its integrity and not break or bend under immense forces or the satellite will not function once it reaches space.
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Once the satellite is in space, it must retain its functionality in microgravity where its component materials will weigh even less than they would on the Earth. This variation in gravitational strength means that the materials used must be incredibly versatile and unique in their integrity.
The structure must also be able to withstand the cabin pressure coming from within the satellite. On the International Space Station, the oxygen within it can exert a force of up to 15 lbs per inch on a surface.
If the material is not strong enough to withstand that 15 lbs per inch force it could rupture and cause an air leak, threatening the lives of everyone on-board.
Another threat to satellites to consider is the amount of projectiles which will come into contact with the structure. The shrapnel of older defunct artificial satellites still orbits around the earth today as space junk.
These high velocity metal scraps can shred newer still functioning satellites if the materials used are not strong enough to shrug off these projectiles.
In addition to these man made threats to artificial satellites, meteoroids in space can reach speeds of 42km/s (faster than a bullet) and pose a significant threat to satellites.
As launching an object into Earth orbit is already such an expensive venture, the materials under consideration must be economically viable. Scientists must consider how expensive a material is to create and how expensive it will to test a material.
In many cases, scientists will be unable to pursue studying a material as funding the testing of the material will be too expensive. In order for a material to be feasibly used in space it must also be incredibly lightweight. A single kilogram of extra mass can increase the cost of the launch by thousands of dollars.
The Materials up to the Challenge
Kevlar
One of the materials that often is able to fit the bill is Kevlar. Kevlar, a material used in bulletproof vests and armour, is an incredibly lightweight and strong material making it perfect for space travel.
In addition to its high strength, kevlar also is incredibly resistant to temperature changes making it ideal for the orbiting structures that move in and out of the sun’s direct heat as they orbit the Earth. Kevlar’s toughness and durability also makes it ideal for protecting artificial satellites from dangerous orbital debris.
Materials Tested on the International Space Station
Aluminum
Another material that often used in space is Aluminum as it is light in weight. On its own, aluminum is not incredibly strong but when combined into alloys with other metals into it becomes much stronger.
Aluminum alloys are often strong and lightweight enough to be functional in space structures and satellites. Aluminum is used for the shutters on the windows of the International Space Station in order to protect the windows from impacts.
These windows already are made with glass thicker than panes of glass on earth and often with twice as many panes. However, the additional aluminum shutters guarantee the safety of the astronauts within.
The Materials of the Future
The materials of the future are going to need to pass even more rigorous testing in order to be functional in more ambitious endeavours.
NASA Langley is working on a structure that will allow a telescope to remain focused and steady on a distant object without moving more than four millionths of an inch. This must be done by counteracting the small vibrations that may be caused by scientific sensors and other attachments on satellites.
Future artificial satellites and space structures must be able to counteract these vibrations and maintain the precision and accuracy that more advanced scientific devices require. These new materials and experiments will allow us to further explore and expand into space.
Sources and Further Reading
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