Thermal Vacuum testing basics
Thermal vacuum chambers provide environments that most realistically simulate the environment in which products and components will be used. For aerospace, the satellite and space vehicle systems, subsystems, and components must pass carefully planned environmental testing to ensure reliability and safety.
Thermal vacuum chambers have been used for many years of reliability testing. Kennedy’s call to send a man to the moon required components of NASA’s Apollo Lunar Module, as well as the other electronics equipment destined for space be reliably tested with environmental simulations. Even wristwatches worn by astronauts were tested.
The radiative and conductive thermal environments test to expose flaws and identify weaknesses. Heat transfer by convection as in a typical temperature chamber is not possible in a vacuum. Reliability evaluation for disintegration or deterioration and lifespan of the product are part of the plan. The strongest, most cost-effective materials can be verified.
The thermal vacuum chamber is used to heat and cool devices by way of conduction or radiation. Thermal platforms, use Liquid Nitrogen or other refrigerant liquid to maintain cold temperatures and radiant or conductive heaters to keep the temperature at a hot set point. Temperatures generally range from -300F/-150C to +300F/150C. Sizes vary from benchtop to large walk-in systems.
The rigid enclosure, called a vessel or bell jar, has the air and other gases removed from inside with a vacuum pump resulting in a low-pressure environment (the vacuum) within the chamber. Conductive heat transfer achieves set point with less energy and time.
The vacuum chamber uses mechanical and cryogenic/turbopump systems to decrease pressure in the chamber.
Thermocouples or RTDs (Resistance Temperature Detector) are commonly used in vacuum chambers to measure the temperature/control at different locations of the device while the system is operating. Click here for a discussion on RTDs v. thermocouples.
Ensuring good surface-to-surface contact for conductive heat transfer is very important. Eliminating particles or gapping in between surfaces is yet more important in a vacuum than in atmospheric testing.
Using secondary or multiple sensors in the thermal vacuum chamber helps verify important zones in the device under test. Click here for more advice.
With the thermocouples attached to the monitored locations, the vacuum chamber pressure is lowered. As the chiller lowers the temperature, ambient pressure drops.
Thermal cycling subjects the device under test to alternate between high and low temperatures within the range that is required while a vacuum is maintained. To demonstrate component survival at temperatures in space, logging is correlated with other device tests that are being performed.
Thermal vacuum testing has contributed greatly to our advancements in aerospace. Over the last 70 years, the ability to simulate the harsh environments of space has saved us great fortunes of money and time allowing us to advance beyond expensive and risky trial and error processes.
Contact TotalTemp Technologies to answer your benchtop thermal vacuum testing questions and find out more.