File image of the Proton rocket launching the Zarya module to begin ISS assembly in November 1998. Photo: NASA

The Proton rocket being used to carry Zvezda to orbit is a derivative of a launcher first introduced in 1965. It is built by the Krunichev State Research and Production Center in Moscow and has a reliability rating of 98 percent.

With Zvezda perched atop the rocket in a protective fairing, the three stage Proton stands 180 feet (55 meters) tall and measures up to 24 feet (7.3 meters) wide. At launch, the vehicle will weigh 1.54 million pounds (700,000 kilograms).

The six RD-253 engines powering the Proton's first stage will generate about 1.9 million pounds (8,450 kilonewtons) of thrust during the first two minutes and six seconds of flight. The second stage, powered by four RD-0210 engines generating 475,000 pounds (2,113 kilonewtons) of push, will fire for about three minutes and 24 seconds.

A single 125,000-pound-thrust (556 kilonewtons) engine, another RD-0210, in the third stage will operate for about four minutes and 17 seconds to inject Zvezda into an initial orbit measuring 220 statute miles by 115 statute miles (354 kilometers by 185 kilometers).

The engines use nitrogen tetroxide, an oxidizer, and unsymmetrical dimethyl hydrazine, a fuel, as propellants.

Khrunichev and its engine manufacturer Voronezh Mechanical Plant spent nearly four months determining why two Proton rockets suffered nearly identical failures last year. On July 5 and October 27, 1999, the second stages of Proton boosters malfunctioned, sending the rockets crashing back to Earth.

Investigators concluded poor workmanship during the construction of second stage engines more than six years ago doomed the rockets. Debris and foreign materials were left in the engines, causing the powerplants to explode during launch.

Russian officials have developed plans to prevent similar engine problems in the future including better quality control processes during manufacturing and special examinations of all flight motors.

Design changes including the new Phase 2 RD-0210 engine used by the second and third stages have been incorporated and were flight tested last month when a Proton safely placed the Gorizont-45 communications satellite into its proper orbit. The second qualification flight occurred on the evening of July 4 when a Geyser data relay satellite into orbit for the Russian Ministry of Defense.