Private space-launch company SpaceX carried a scientific satellite into orbit Sunday but failed again in an attempt to land the rocket undamaged for reuse on future missions.
The Jason-3, a US-European oceanography satellite, was launched from Vandenberg Air Force Base in California atop SpaceX's unmanned Falcon 9 rocket.
The satellite is designed to gather data on oceans, including tracking global sea level rise. The mission is meant to improve weather, climate and ocean forecasts, US space agency NASA said.
NASA hailed the "successful launch" on Twitter.
As the Falcon 9 returned to Earth after deploying the satellite into low orbit, SpaceX attempted to land the spacecraft on an unmanned floating platform in the Pacific Ocean.
The company later tweeted that the rocket landed softly on the vessel, a so-called droneship, within 1.3 metres of the centre of the platform, but one of the legs failed to fully lock and collapse on impact.
SpaceX chief Elon Musk, an investor whose ventures include electric car company Tesla Motors, said on Twitter: "Touchdown speed was ok, but a leg lockout didn't latch, so it tipped over after landing."
A month ago, SpaceX was able to successfully land one of its rockets, proving the principle of reusing the up to 90-million-dollar spacecraft, after previous failures.
Later Sunday, Must tweeted a photo of wreckage on the platform with the comment: "At least the pieces were bigger this time."