Thermal Vacuum Test I

Outgassing under vacuum : Thermal Vacuum Test I

According to ECSS-Q-70-02A: "A thermal cycling test for the screening of space materials and processes" (For investigation of mass loss as function of time, see: Thermal Vacuum Test II).

The Thermal Vacuum Test I is used for the qualification of materials proposed for use in spacecraft and associated equipment and for optical devices. The aim of this test is to determine the amounts of outgassing products. For the test, materials are submitted to climate for water uptake. Then they are subjected to thermal vacuum (125°C for 24h). Finally they are again submitted to climate. Additionally, in the vacuum chamber cooled "collector plates" are mounted directly above the heated cups with the materials. These plates collect some of the outgassing species.

With this test the outgassing properties can be determined by the following parameters (see figure below):

• CVCM : Collected Volatile Condensible Material is the mass gain of the collector plates divided by the initial mass of the material
• RML : Recovered Mass Loss is the difference between initial mass and mass after re-climating (shows the amount on non-water products)
• TML :Total Mass Loss is the difference of mass directly before and after vacuum test (shows the amount of all outgassing products in percentage of initial mass)
• WVR : Water Vapour Regained is the amount of water uptake after vacuum test

Example for total mass loss (TML) in vacuum test (125°C) and recovering of water in climate afterwards (VWR).

Performing this test according to ECSS-Q-70-02A "A thermal vacuum test for the screening of space materials" requires a regularly re-approval by ESA. Last audit and re-approval was done January 2002. Tests may also performed according to ASTM E 595-93 "Standard Test Method for Total Mass Loss and Collected Volatile Condensable Materials from Outgassing in a Vacuum Environment".

Thermal Vacuum Test I characteristics