Impact of Icing on Launcher's Thermal Control: ARIANE 5 ESCA Experience

During ascent of a previous ARIANE 5 - Launcher the stage separation system (SSS) of the cryogenic upper stage (ESCA) exceeded its qualified lower temperature limit at the event of stage separation (SS). Although, for that flight the proper cutting of the stages by the SSS embedded pyrotechnical device could be achieved, detailed studies followed this unexpected cold temperature drop as outlined in this paper.

These investigations identified the formation of frost/ice on ground and its subsequent sublimation during ascent as the important contribution to the observed phenomenon. Consequentially, counteractive measures have been successfully applied for subsequent flights, where up to now a temperature limit violation of the SSS has never been encountered again.