International Launch Services (ILS), the commercial marketing arm of the Russian rocket manufacturer Khrunichev, has announced that the Proton four-stage rocket is going to be modularised to offer a new family of smaller launch vehicles, in addition to a growth version. At the top end of the scale, the Proton M rocket is going to be further improved to a new Proton M+ standard, which will allow it to carry payloads of up to 7,100 kg into GTO (Geosynchronous Transfer Orbit). This launch vehicle should be available by 2018.
However, to capture other markets, using the propulsion/stage modules it is developing, Khrunichev has decided to offer a Proton Medium version that does away with the second stage of the Proton M. A stretched version of the current Proton M first and third stages will provide a three-stage rocket (including the Breeze M upper stage) capable of launching 5,700 kg to GTO and 2,400 kg to a sun-synchronous low Earth orbit. This rocket will be made available in 2018.
Further to this, by reducing the six first-stage engines to four, a new Proton Light rocket may be produced in 2019. This will be capable of launching 1,450 kg payloads to sun-synchronous orbits.
Comment by David Todd: Whether all of these versions get built remains to be seen. The Proton Light, for example, would directly compete with the Angara 1, also offered by ILS. Nevertheless, it seems likely that at least the Proton M+ will be built.