“Space… the final frontier.” Every Star Trek fan knows the starting monologue to the show and the movies. However, the “final frontier” of the near-earth orbit has become a satellite parking lot, crowded with over 6,540 satellites of all sizes. And that’s just the beginning.
SpaceX’s Starlink project plans to add 7,518 more satellites. They hold the record of sending up 143 satellites in one flight in January 2021. Each satellite weighs 590 pounds and costs $250,000.
Building a satellite can cost hundreds of millions of dollars. Launching one can cost from $20 million to $200 million depending on the satellite’s size, the country, and the launch vehicle.
Due to the enormous investment and potential safety hazards if they fail, NASA requires that satellite builders test each part and component in space-like conditions. That’s where a space environment simulator or simulation chamber with thermal vacuum testing comes into play.
What Is Satellite Testing?
Since the U.S. space program began, satellite and component testing in a thermal vacuum chamber has been mandatory to comply with various regulatory standards in the aerospace and defense industries. Thermal vacuum testing mitigates the risk and prepares the satellite for the extreme environment and temperatures encountered in orbit.
We take satellites for granted, but without them, we are almost helpless. Cellphones, the internet, GPS navigation are just some of the ways they have improved our lives.
Every nut, bolt, motherboard, hard drive, and finished satellite must pass rigorous testing in space-like environments before they can receive a “Go for Launch.” There are four testing conditions every component must pass:
- Vibration, Shock, and Acoustic levels of launch conditions
- Electro-radiation
- Pressure variations down to a total vacuum
- Thermal variations from ambient ground level to space conditions
The governments and industries who pay for these satellites want reassurance that everything will still work after a violent launch and the harsh space environment. Once in orbit, there is no retrieving or repairing a satellite.
Manufacturers and subcontractors rely on various facilities around the country that have space simulation chambers to test their equipment.
Space Simulation Testing
Space simulation chambers are the answer to satellite and durability testing. They recreate space-like conditions here on Earth. So, how strong is the vacuum of space?
Scientists consider the boundary of space to be 100km from Earth, where the pressure is 2.7 x 10-03 mbar. Most satellites orbit between 200 and 2,000 km from the surface, called Low Earth Orbit or LEO. For example, the International Space Station’s orbit is 400 km, where the vacuum is 10-07 mbar.
A space simulation chamber can create the same vacuum down to 10-07 mbar. Using ultra-low temperature process cooling equipment, these thermal vacuum chambers can also recreate the lowest temperatures a satellite will experience.
The different vacuum pumps required to create such a high vacuum work at high temperatures. Keeping the various processes cool during testing is the job of the process chillers. Process chillers for any application are essential to maintaining the pumps operating at total capacity.Some vacuum chambers can be relatively small, fitting in only a few components. The Lyndon B. Johnson Space Center’s space simulation chamber, Chamber A, has a 45-foot diameter floor that can hold up to 50,000 pounds. It can hold an entire satellite and rotate 180°.
Pressure Vessels for Parts or People
A pressure vessel is any container that resists high internal or external temperatures and pressures. Two vessels that come to mind are a scuba tank and a passenger jet cabin. Both keep the pressure contained. A vacuum chamber is a pressure vessel that keeps pressure out while it has a vacuum inside.
Space simulation chambers must withstand pressure from the atmosphere and maintain a vacuum of 10-07 mbar to mimic the space environment. Inside the chamber, researchers can simulate atmospheric conditions from ground level to space and back. Every part must pass these tests before being used in a satellite. Vacuum chamber technology lets manufacturers know if their parts can withstand the rigors of space travel.
Some of the testing parameters inside a vacuum chamber include:
- Humidity (RH)
- Low Temperature
- High Temperature
- Various Pressure Levels
- Atmospheric Altitude
- Radiation
- Vibration
Another benefit of vacuum chambers is the process of degassing. Degassing is a process that uses a vacuum to remove trapped gas molecules from parts and materials like resin, silicone, rubber, and other flexible compounds.
There are pressure vessels for human occupancy (PVHO) built to hold one or more people. They can test space suits and life support systems in a controlled environment.
Pressure vessels that can control and alter the temperature along with the pressure are called thermal vacuum chambers.
Thermal Vacuum Chambers
The vacuum of space is not the only physical problem satellites face. Temperatures can fluctuate by 500 degrees. External surface temperatures of the International Space Station reach 250 degrees F (121° C) on the sunny side and -250 degrees F (-157° C) on the shady side.
All satellite materials must withstand the same thermal conditions. Something called a thermal shroud recreates those temperature extremes inside the thermal vacuum chamber.
What is a Thermal Shroud?
The thermal shroud is a plate that allows heating or cooling of the items in the chamber under a vacuum. Supercooled fluids circulate through the thermal shrouds recreating the low temperature of space. Testers apply an array of xenon lamps to simulate the sun’s heat radiation.
The PID (proportional–integral–derivative) temperature controller regulates the set temperatures during testing. One side of the shroud will be black, and the other will be highly polished and reflective. A thermal shroud transforms a plain vacuum chamber into a thermal vacuum chamber. Researchers can test components for thermal durability under the vacuum of space.
Process Cooling Keeps Vacuum Pumps Running
There is a tremendous heat transfer in vacuum pumping, thermal loads, and high vacuum chambers. Without proper pressure vessel cooling or process cooling, the materials and systems can overheat, causing damage. Custom chillers and cryogenic pumps keep the process cool and avoid heat damage.
One process cooling solution is a portable application called Fluxwrap Fluid Channel Blankets. Like a blanket, they can wrap around uneven surfaces such as tanks or drums. A circulating cooling system keeps the process at a constant temperature.
The Critical Importance of Satellite Testing
The space simulation test is mandatory for anything that will launch into space. Without testing inside thermal vacuum chambers, launching satellites would be impossible.
A NASA report revealed that between 2000 to 2016, of all small satellites launched, 41.3% failed or partially failed. That’s almost one out of every two small satellite missions ending in either a total or a partial mission failure.
Space simulation testing is not guaranteed, but it will substantially reduce the likelihood of inferior parts and components making their way into space. At the very least, testing can uncover design flaws that would otherwise go unnoticed until it’s too late. North Slope Chillers offers several levels of portable, compact, and powerful recirculated process cooling equipment down to -112°F. These units are easy to install, remove, and relocate. For specifications, please contact us today at (866) 826-2993 or email us at [email protected].
