What Materials Can Survive in Space?June 7, 2019
Space puts all materials under severe stresses, allowing only the most robust products to survive. Testing materials for space is crucial to ensuring the devices that use them will last in the worst conditions known to humanity without a repair service anywhere in sight. Without testing, the efforts of putting satellites into orbit are for naught when the devices fail in the heat of the atmosphere or the cold of space. A thorough examination is more than a series of steps in the process. It should be an essential component of ensuring aerospace products will survive.
What Are the Harsh Conditions of Space?
Space puts satellites and other devices under extreme conditions. Temperature, gravity, radiation and pressure are only some of the variables that are not like those on Earth. Anything that needs to get into orbit and survive for any length of time should have resistance to extreme levels of these factors.
1. Temperature Spikes
Temperatures shift from high to low as an orbiting device moves into the sunlight or behind the Earth’s shadow. For example, NASA’s Orion spacecraft designed to travel outside the moon’s orbit will experience temperatures ranging from -101 to 288 degrees Celsius (-150 to 550 degrees Fahrenheit). Because the Orion will carry a human crew, the temperature inside the living and working quarters must remain a stable 25 degrees Celsius (77 degrees Fahrenheit).
To accomplish this task, NASA will combine temperature controls and a thermal protection system to keep the astronauts inside safe. The temperatures become even more extreme upon reentry. Moving at a speed of 25,000 mph, the friction of the atmosphere will generate heat around the spacecraft up to 2,760 degrees Celsius (5,000 degrees Fahrenheit). The craft’s AVCOAT heat shields will protect the ship at their own expense. These single-use shields will disintegrate during reentry.
Launching a spacecraft requires overcoming the Earth’s gravitational pull, but during the upward momentum of leaving the launching pad, the craft will experience up to three times the force of Earth’s gravity. Materials used on the spacecraft cannot break, bend or weaken under such effects.
After the craft goes into orbit, the gravitational force drops to almost zero. This shift from high to no gravitational force can affect the integrity of low-grade materials or those not designed to withstand such stresses.
Outside the protection of the Earth’s atmosphere, radiation levels increase. But those values that reach a spacecraft depend on how high that craft orbits the planet. Those in low-Earth orbit will experience less radiation than those in higher orbits or destined for even farther travel. Solar storms can drastically spike the radiation levels with little notice.
On the Orion, which will experience much more radiation than satellites in Earth’s orbit, several redundant systems will protect the craft and astronauts from radiation. Four computer systems will continue to check themselves throughout the journey. A separate backup computer will keep the spacecraft in operation should radiation cause the other four computers to fail. Astronauts will have a specially shielded storm shelter to retreat to in case of solar storms, and NASA is currently testing unique radiation-protective clothing that astronauts can quickly don to keep their organs safe from radiation damage.
Spacecraft will experience internal and external forces. For example, the internal pressure from oxygen inside the International Space Station is 15 pounds per inch. The structure of the craft must stand up to this force from the inside in addition to retaining its shape from exterior pressures on it such as gravitational changes during launch.
Over time, the number of defunct satellites still in orbit has increased. These shells create large amounts of space junk around the Earth, and any craft in orbit will experience several impacts from this refuse. Like the current satellites, older models had similarly durable constructions. So, their materials are robust and can create significant damage to new satellites that can’t withstand the impacts.
In orbit, space junk is not the only problem for satellites. Meteors can reach speeds faster than bullets, 42 kilometers per second (26 miles per second). At these rates, even small space rocks can pierce a hole in a weak part of a satellite. Natural and human-made debris are real threats to any spacecraft, which is why testing impacts during material test programs should be an essential part of any orbiting spacecraft’s creation.
Vibrations may not occur in space, but spacecraft will experience much movement during and immediately after launch. Swept sine testing looks at how satellites handle a variety of vibration frequencies. By testing a range of motion on the materials, scientists can find weaknesses and correct them before the craft reaches orbit.
What Types of Objects Need to Survive in Space?
Various craft must be built to stand up to the extremes of space. Satellites, shuttles and even extravehicular mobility units (EMU) all need to have components that protect from impacts, pressure, radiation and temperature swings. Since these all need to withstand similar conditions with only the levels varying, testing for survivability overlaps for many types of spacecraft.
Satellites are the most common spacecraft. Earth has 1,500 active satellites in orbit, both commercial and government-owned. Today, everything from GPS to communications come from satellites. If one of these orbiters fails, millions of users could find themselves at a loss. Additionally, the company operating the orbiter would need to pay for another launch. Testing satellites for space ensures that companies’ investments in their spacecraft are well-placed.
Individual materials need testing on the craft, and the systems require examination, too. For satellites, the batteries, fuel cells, solar panels, communication system, electrical components and antennas are only a few of the elements we test to ensure they will operate in concert correctly once the device reaches orbit.
Satellites destined for geostationary orbit require tests to verify the operation of their propulsion and the longevity of onboard systems to allow the craft to last for ten years or more. These larger satellites have more complex systems, more parts and consequently, require more testing.
Even smaller craft in lower orbits still need testing to ensure they can make it to orbiting altitude safely and do their jobs correctly. By putting small satellites through space simulation testing, we can see how the device will survive in the temperatures, humidity and pressure of space.
In addition to the satellites, the equipment aboard them, including communications devices and cameras, need to have the durability to hold up to the same conditions. Space simulations can help confirm that these devices have adequate protection from the harsh conditions they will experience during use.
While ensuring the overall spacecraft and its equipment will hold up during use, before building the craft, engineers need to know the materials used will not fail when subjected to the extremes of space.
How Materials Testing Ensures Survivability in Space
When designing spacecraft, engineers need to know the types of material to use. Testing the elements in their designed shapes and thicknesses will ensure they can take the stress of going into orbit.
Space materials testing cannot be a portion of the design process engineers overlook. Conditions on Earth differ so much from space that materials used for a satellite will not experience orbit circumstances until after launch without prior testing. No company wants to discover their spacecraft failed as soon as it entered orbit.
To thoroughly examine the strength of materials, testers run the materials through a barrage of tests for multiple stresses the materials would experience in space.
- Impacts: Man-made and natural objects bombard orbiting satellites daily. Impact testing ensures materials can stand up to intense hits.
- Corrosion: This type of testing verifies lifespan before the material breaks down.
- Compression: Compression strength is vital for materials destined to experience the extreme pressures of space.
- Fatigue: Spacecraft undergo intense stresses, and fatigue testing looks at how long the materials will last under the worst forces until they fail.
- Thermal: Exposing the material to the extreme high and low temperatures of space is part of the thermal testing process.
- Flexure: Support materials often need flexure testing to see how much load the parts can handle before bending.
- Flammability: Flammability determines how well materials burn, which relates to how quickly a fire will spread. For safety-related components of aerospace craft, materials need to stop flames instead of moving them forward.
- Composition: For composite materials, a guarantee of their makeup gives you additional information about how to use them.
- Thermomechanical analysis: Thermomechanical analysis looks at the changes a material undergoes through a range of temperatures.
Testing verifies that materials will be able to withstand the conditions in space. Additionally, many regulatory agencies require testing programs to allow spacecraft approval to go into space. When we conduct materials testing, we ensure compatibility with FAA regulations and RTCA DO-160. By fulfilling these requirements, we can verify your materials will be allowed to go into orbit. Spacecraft and satellites cannot survive in space if they cannot get there first.
What Materials Are Used in Space?
Not everything can take the harsh conditions of space, but some materials have proven to excel in that environment.
Kevlar is more frequently associated with its use in bulletproof garments for the military and police. This material has several properties that make it ideal for use in spacecraft. It has strength enough to resist bullets, making it perfect for standing up to impacts from meteors and space junk. Additionally, Kevlar weighs little compared to its durability. It also can experience extreme temperatures without damage to its structure or changing its form.
Another common material used in spacecraft is aluminum. Though itself, aluminum does not have the needed strength for space use, when combined with other metals into an alloy, its strength increases while maintaining its signature light weight. Aluminum alloy performs so well in impact testing that the International Space Station uses this material for its window shutters to keep debris from damaging the windows.
3. Reinforced Carbon-Carbon Composite
For the nose of the space shuttle that encountered temperatures over 1,260 degrees Celsius (2,300 degrees Fahrenheit), NASA used a reinforced carbon-carbon composite (RCC). Other areas of the space shuttle that experienced similarly hot temperatures used this composite.
The benefit of RCC lies in its ability to give off heat applied directly to it as well as indirect heat. The warmth from nearby surfaces on the shuttle traveled to the RCC-covered parts, where the RCC would release the heat, helping the shuttle to cool down, similar to the way a radiator indirectly cools a car engine.
The process used to create RCC created cracks when the designers applied silicon carbide coating at high temperatures. However, when the temperatures around the shuttle rise, the cracks close. This changing of the material’s structure at various temperatures iterates how necessary testing the content is. Without thorough examination, a part made of RCC or similar composure may not perform as expected at elevated temperatures, causing the failure of the piece and the spacecraft it’s part of.
4. Reusable Surface Insulation
High-temperature reusable surface insulation (HRSI) has a black borosilicate glass coating, making this dark surface capable of standing up to the same high temperatures as the nose cone encountered. White parts of the shuttle have low-temperature reusable surface insulation (LRSI) and can only withstand lower temperatures, up to 649 degrees Celsius (1,200 degrees Fahrenheit). The white coloring allows for better control of temperatures inside the shuttle where the astronauts worked.
NASA replaced the LRSI with advanced flexible, reusable surface insulation (ARSI). The space agency used ARSI for later shuttles Atlantis, Endeavor and Discovery. The application of this insulation reduced the cost of construction and the weight of the shuttle.
5. Nomex Felt
For the coldest areas of the shuttle that experienced temperatures no higher than 371 degrees Celsius (700 degrees Fahrenheit), NASA used reusable surface insulation made of coated Nomex felt. The middle and tail end of the craft in addition to the payload doors had this coating.
6. Thermal Glass
The space shuttles needed windows that would allow the astronauts to see out of clearly without allowing heat to pass through the material. Thermal glass proved the solution to protect the astronauts from both high and low temperatures around the windows and the pressures of space travel.
Silica cloth filled gaps on the space shuttle created by moving parts such as around the landing gear or the loading bay. Another part of the shuttle that used silica in its many forms included the RCC nose cone, which used sodium silicate to seal the cracks created during the coating process. NASA selected silica tiles for lower temperatures zones of the space shuttle, and shuttle builders used borosilicate glass coating for the HRSI portions of the ship.
Why Do These Objects Need to Undergo Extensive Testing?
Aerospace materials testing programs determine whether satellites survive in space as well as the longevity and durability of the materials. They also evaluate other factors to ensure spacecraft can perform their jobs. Without the work of spacecraft, many on Earth would be unable to work due to failure of GPS or imaging services provided by satellites.
Each test program needs to replicate the most extreme possible conditions the spacecraft will experience. In the case of satellites and other spacecraft, testing is not a single phase but a process that occurs throughout the construction of the craft.
Each part of the spacecraft needs evaluation even before the materials come together to form finished pieces. Satellite materials testing ensures the components used to make the parts will hold up to the extremes of space. In fact, environments in space are so harsh and materials must withstand such intense forces that NASA has created composites like RCC to use where natural substances fail. A thorough program of examining the performance of materials and satellite parts to the completion of the product ensures the longevity of the satellite.
Individual components need to undergo trials, which engineers must also run on the more complex parts those pieces make up. Once finished, the craft needs yet another round of tests to ensure it will successfully survive in orbit. Such rigorous testing is a requirement for any spacecraft to verify that it will withstand both the intense launch forces and the extreme conditions in space.
Test programs verify spacecraft can get permission to launch by meeting government regulations for satellites. Additionally, these programs provide valuable insurance for investors in the satellite. With price tags up to $290 million for a standard weather satellite, such projects require assurance the craft will survive.
Currently, no methods of repairing satellites in orbit exist. Any craft launched must be fully prepared to last long enough to accomplish its work. When failures occur, companies lose the cost of construction and launch as well as the work the satellite would have done in orbit. In the case of scientific satellites designed to gather data, such a loss could push research off its forecasted timeline.
Engineers need to know what types of satellite materials testing to conduct. For instance, radiation levels depend on whether the satellite will be in low-Earth orbit or geostationary orbit.
What Kind of Testing Determines Whether Materials Can Survive in Space?
Space simulation testing recreates the conditions satellites experience in space inside a thermal vacuum chamber. This chamber examines the effects of three things satellites must withstand:
- Infrared sun radiation
- High vacuum
- Extremely cold temperatures
Individual events can occur when a satellite experiences these situations that may not happen in Earth’s atmosphere at sea level. For example, outgassing may not occur until the gases are under high temperatures in a vacuum, but this event is the most common reason for spacecraft problems. Essentially, space simulation testing sees how much a satellite or its parts can take before it fails.
Depending on the application, we can adapt simulations to meet specific regulations, such as the military standards for electronic components, how the environment affects equipment and the RCTA’s requirements for testing airborne equipment and external conditions. Meeting these standards and others ensures you will have a safe craft ready for launch.
What Are the Testing Capabilities at NTS?
At NTS, we offer a range of testing for aerospace materials and finished products. Our space and satellite testing include propulsion and space simulation tests for accurate results that reflect the conditions the device will encounter. Because your craft will need testing at every step of creation, we also offer materials testing in addition to trials for parts and the completed satellites.
With 50 years in aerospace testing, our experts know precisely the parameters your equipment must meet to ensure survivability in space. We’ve worked with almost every major space program the United States has had. With such experience in testing the most well-known spacecraft as well as lesser-known but equally important commercial and other craft, we can perform the tests you need to your satisfaction.
For more information or to talk to one of our experts, contact us online. Once you know your equipment needs aerospace testing, let us know. We will give you a free quote so you can begin readying your satellites or other craft for space.