WASHINGTON The Sea Launch project is on schedule for its first commercial space mission in late September, company officials told space.com Monday. A final date wont be selected until the flotilla of Sea Launch vessels, including its ocean-going launch pad, leaves its Long Beach, California home port in early September, spokesperson Terrance Scott said.

Sea Launch is planned as a commercial space launch service using a three-stage version of the Zenit rocket launched from a floating platform in the Pacific Ocean. The project is a partnership that includes Boeing Commercial Space Company, Kvaerner Maritime, RSC Energia, and KB Yuzhnoye.

Scott said that the payload for the launch, the Hughes DIRECTV 1-R satellite, is undergoing final checkout in the payload processing facility at the Long Beach complex. The two stages of the Zenit booster plus the Block DM upper stage are also being checked out for flight and for installation aboard the Sea Launch Assembly and Command Ship (ACS).

Once the satellite has been completely checked out in its facility, it will be fueled and sealed inside the payload fairing for the launch. The satellite package and the three stages of the launcher will then be loaded aboard the ACS and the ship along with the Launch Platform will sail from Long Beach harbor for the launch site, normally in the mid-Pacific Ocean near the equator. Upon arrival at the launch location, the mated satellite and booster are integrated in a horizontal position and then transferred to the Launch Platform by crane. The rocket is given final checks, is counted down, and launched from the platform while officials in the nearby ACS conduct mission operations.

The first and thus far only Sea Launch flight took place successfully last March 27 carrying a test payload. The inaugural commercial payload, the DIRECTV-1R, is a Hughes HS 601-HP satellite with 30 percent more broadcast capacity than the previous HS-601 design.

In the partnership, Boeing provides spacecraft integration, payload fairings, and mission operations, Kvaerner Maritime provides the launching platform, RSC Energia builds the rockets Block DM upper stage, and KB Yuzhnoye builds the first and second stage of the Zenit rocket.

The Zenit entered service in the mid-1980s as a launch vehicle for the Soviet military. In a modified form it was also used as the strap-on boosters for the Energia launch vehicle that carried the Buran space shuttle.