Tim Furniss/LONDON
NASA will not give the go-ahead for the launch of the Russian Zvezda service module to the International Space Station (ISS) aboard a Proton booster on 12 July until a successful second launch of the booster with uprated engines. Second-stage engine failures caused the loss of two Protons last year.
A Proton, featuring the first set of new second and third stage engines, successfully launched the Gorizont satellite on 6 June. There is confusion as to which launches will precede the Zvezda Proton launch, which will also feature a set of new engines.
Three Proton launches have been provisionally set for late June. Protons with an original set of pre-accident engines are due to fly on 22 June and 30 June, carrying the Express A3 and Sirius satellites, respectively.
The crucial second flight of a Proton with the new set of engines manufactured after the two Proton losses was set for 20 June, but the flight has been delayed for over a month because the military Geyzer-class communications satellite payload is not ready.
A second launch of the Proton with recently manufactured engines is seen as a crucial confidence-booster before the Zvezda launch.
Any Proton failure before the Zvezda launch will inevitably cause its delay. The loss of the service module itself would delay the construction of the ISS by at least a year. The interim control module - which is being funded by NASA as a replacement for the Zvezda, should it be lost - was to have been ready in December, but is reportedly six months behind schedule.
Meanwhile, as well as proving the new engines for the Proton, the 6 June launch was also the first geostationary flight to feature a new Breeze upper stage. The success of the Breeze upper stage was an important step for International Launch Services, which markets Atlas and Proton launchers.
The Breeze M stage can increase the Proton's geostationary transfer orbit delivery capability to 5,500kg (12,100lb), compared with the 4,930kg capability of the DM upper stage.
Source: Flight International
