NPO Yuzhnoye is working on an upgraded version of the Zenit 3SL launcher which would enable the Boeing-led Sea Launch company to offer launches of payloads weighing an additional 1.5t to geostationary transfer orbit (GTO).

The new Zenit would comprise a first stage with a core liquid-oxygen tank with kerosene propellants contained in two 22m- (72ft) long, 2.2m-diameter strap-on stages. The booster has a similar second stage and a cryogenic DM stage to the Proton.

Operated by Sea Launch from the Odyssey offshore platform in the Pacific Ocean, the uprated booster would be able to carry payloads weighing 7.5t into GTO, compared with the present 6t capacity.

The upgrade is needed to match the increased GTO capacity being offered and planned by uprated Ariane 5 boosters.

The current Ariane 5 has a 5.8-6t to GTO capability which will be increased to up to 8t by the first of three new models, the most powerful of which will carry 12t to GTO by 2005.

Source: Flight International