Currently, several solutions exist to limit the outgassing-related risks. They include controls and procedures during the assembly integration and tests (AIT), in ground or in-flight bake-out, selecting materials with low-outgassing properties, improving their chemical formulations, optimizing the view factor between potential contamination sources and sensitive parts of the spacecraft, or the use of absorber coatings(1) or honeycombs. Anti-contaminant coatings are also currently investigated to repel(2) or decompose(3) the outgassed species (e.g. by photocatalysis). These solutions are promising but are complex to develop and their efficiency in-orbit is difficult to validate.

Instead of dealing with the outgassed molecules, it is proposed to directly limit the outgassing itself by means of thin films which would act as a barrier to the outgassing. Encouraging results were already published earlier by others(4). To investigate this approach, Atomic Layer Deposition (ALD) was used to coat a 3D-printed polyether ether ketone (PEEK) sample with a thin coating (about 110 nm) consisting of oxides. Dynamic outgassing experiments were performed to study and compare the kinetics of outgassing for a coated and a non-coated sample.

The obtained results suggest, firstly, that PEEK materials have very favourable outgassing properties with negligible collected volatile condensable material (CVCMs), and, secondly, that the coating slows down notably the kinetics of outgassing and the reabsorption of what was attributed to moisture. If these results are confirmed by further investigation, and permit to reduce the CVCMs, this solution could be applicable to a wide range of materials having complex geometries and could improve other properties such as thermo-optical properties.

(1) Abraham; N. S. (2015; July). NASA applications of molecular adsorber coatings. In Contamination; Coatings; Materials; and Planetary Protection Workshop (No. GSFC-E-DAA-TN24976).
(2) doi.org/10.2514/1.A34230
(3) doi.org/10.1016/j.actaastro.2023.08.039
(4) doi.org/10.1038/s41563-019-0565-3