Development and operation of venting system of ascent unit of Zenit-3SL sea-based integrated launch vehicle

The paper describes technical aspects of development and operation of a unique venting system for unpressurized compartments of the ascent unit of Zenit-3SL integrated launch vehicle developed within the International Sea Launch project (Sea Launch) with the participation of RSC Energia (Russia), Boeing company (the USA), Kværner company (Norway) and GRB Yuzhnoe (Ukraine). The system drains air from gasdynamically connected ascent unit unpressurized compartments during a flight to ensure minimum pressure drops acting on the external shells of frame compartments and their partitions, and meet requirements of spacecraft developers for environment parameters in their location area. Reviewed are main performance data, system test phases in the course of development, and its operation specifics.