Sea Launch is a multinational spacecraft launch service that used a mobile maritime launch platform for equatorial launches of commercial payloads on specialized Zenit-3SL rockets through 2013.
By 2013, it had assembled and launched thirty-one rockets, with three failures and one partial failure. All commercial payloads have been communications satellites intended for geostationary transfer orbit with such customers as EchoStar, DirecTV, XM Satellite Radio, PanAmSat, and Thuraya.
The launcher and its payload are assembled on a purpose-built ship Sea Launch Commander in Long Beach, California, USA. It is then positioned on top of the self-propelled platform Ocean Odyssey and moved to the equatorial Pacific Ocean for launch, with the Sea Launch Commander serving as command center. The sea-based launch system means the rockets can be fired from the optimum position on Earth's surface, considerably increasing payload capacity and reducing launch costs compared to land-based systems.
Sea Launch mothballed its ships and put operations on long-term hiatus in 2014, following the Russian military intervention in Ukraine. By 2015, discussions on disposition of company assets are underway, and the Sea Launch partners are in a court-administered dispute about unpaid expenses that Boeing claims it incurred. In September 2016, S7 Group, owner of S7 Airlines announced they were purchasing Sea Launch.
Sea Launch was established in 1995 as a consortium of four companies from Norway, Russia, Ukraine and the United States, managed by Boeing with participation from the other shareholders. The first rocket was launched in March 1999.