... Upper stage Block DM design is based on Block D, which was originally developed under lunar program N1-L3 and the first time it successfully operated in flight was as a part of L1 complex (with Proton launch vehicle) on March 10, 1967. Upper stage Block DM features high reliability proven by more than 30 years of its operational history, and capacity for multiple burns of the main engine, which allows it to perform the required orbital maneuvers. ... Official WEB-site of S.P.Korolev RSC Energia . ...