As the instruments of satellites are getting more sophisticated, they are also getting more sensitive to external influences. Deposition of gases due to the low-temperature environment can be one of these external influences. For the European-Chinese SMILE mission, a Soft X-Ray Imager (SXI) is present which has CCD’s exposed to very low temperature. As water vapour is present in the air, as well as water absorbed into the paint of the enclosure, ice deposition could happen under specific conditions. To assess the outgassing of PU1 paint, an experimental outgassing study has been performed at room temperature. Additionally, numerical simulations are performed both in the continuum and the molecular regime to assess the proper functioning of the venting paths. A semi-theoretical correlation is provided which allows calculating the mass flow leaving the instrument based on the internal pressure and temperature. For the specific application of the SXI instrument, the venting rate of the enclosed air is assessed. Also, the outgassing of water vapour should not result in pressure conditions which could trigger ice deposition on the cold CCD surface. Based on the performed simulations and experiments, no issues are expected for the SXI.

The latest characterization of turbulent spot growth accounting for wall temperature and compressibility effects along with a formulation of the transitional Reynolds stresses are assessed in the present γ-α transition model. Additionally, previous model developments to reproduce the normal intermittency profile are now rederived based upon the exact Klebanoff profile. Furthermore, destruction and production terms of the intermittency equation are further refined assuring a more generic transition model. The construction of this transition model is primarily set up to be independent from the used turbulence model, allowing the most suitable to be selected by the user for the envisaged application. The newly developed γ-α model is validated with the classical SST turbulence model for subsonic (with and without pressure gradient) and supersonic (with and without shock wave boundary layer interaction) test cases and has shown to outperform the classical γ-Reθt model in onset location prediction, skin friction slope and overshoot.