After notching its first successful landing of a rocket booster in mid-December, SpaceX experienced a setback on the weekend when it attempted to land another booster. Instead of being on solid land as in December, the target this time was a barge in the Pacific Ocean.

Twice previously, SpaceX has attempted to land rocket boosters on barges and failed. While this attempt was unsuccessful too, it went far better than the previous two landings in January and April 2015, with the booster actually touching down before it slowly began to tilt and eventually topple over.

SpaceX CEO Elon Musk said later that one of the booster’s support legs had failed to lock into place after it had touched down, and that had caused the accident. He further speculated that the failure might have been due to ice build-up from condensation from heavy fog at the time of lift-off.

As might be imagined, a barge landing presents greater challenges than a landing on terra firma. This weekend, waves in the vicinity of the platform were in the three to four metre range. Barge landings offer greater flexibility in the type of launches SpaceX can do, though, so they’re seen as an important step in the development of a reusable rocket booster that would dramatically reduce the cost of space missions.

Here’s a short video clip of the Falcon 9 rocket’s descent: