Tim Furniss/LONDON

ILS International Launch Services will offer the up-rated Russian Proton M booster for commercial launches to geostationary orbit (GEO) in 1999. With a 50% increase in payload capability, the rocket will be the most powerful on the commercial market.

The Proton M, which will replace the existing Proton K, will be capable of placing 3,500kg payloads into GEO and the equivalent of 7,600kg into geostationary transfer orbit (GTO). It will have a new upper stage, the Breeze M, a derivative of the Breeze K stage which has been flown on the Rokot launch vehicle. This will replace the current Proton K's liquid-oxygen/liquid-hydrogen DM fourth stage, while the three stages of the K model will be improved.

The first prototype of the new vehicle will be tested in 1998. The main enhancements will be a digital control system adapted from the Zenit launcher, improved first-stage RD-253 engines offering a 7% increase in thrust, and a modified propellant-feed system to reduce residual propellant.

The Stage 2/3 interstage structure will be reinforced, and weight reductions achieved where possible. The improvements are designed to produce a 6.2% increase in the payload weight delivered into the standard 51.6í-inclination, 200km Earth orbit, to 22,500kg. The Proton has a KVD-1 cryogenic upper stage, which could place up to 4,500kg into GEO after 2000.

The single-engined Breeze M stage, which is powered by the same nitrogen tetroxide and unsymmetrical demthyl hydrazine, storable propellants as the Proton's three stages, will be fitted with a toroid external propellant tank which quadruples propellant load. The tank is emptied preferentially during transfer-orbit firings, and then jettisoned.

The engine of the new stage can be restarted more than eight times during flight, carrying out multiple apogee, perigee and plane-change burns, to equatorial inclination. It can also ignite sub-orbitally to complete the ascent phase of the Proton M, increasing payload performance, if necessary.

The Atlas 2AS has a 3,670kg-to-GTO capability, while improved Atlas 2ARs and 2ARS, using Russian modifications, will increase this in 1998 to 3,870kg and 4,140kg, respectively. ILS has 14 commercial contracts for the Atlas fleet, not including military obligations.

The competitive Zenit 3 Sea Launch offers a maximum 6,900kg GTO capability. The Ariane 5 offers a theoretical one-satellite GTO capability of 6,800kg.

Source: Flight International