SpaceX was this close to launching another rocket on Sunday. The company’s Falcon 9 had already ignited its engines, but with less than a second to go its onboard computers aborted the mission. In a quick tweet, SpaceX founder Elon Musk explained what went wrong.

There’s some jargon in Musk’s tweet to unpack. The phrase “hold for boat” actually refers to a boat that was spotted out at sea within the restricted area around the Falcon 9’s flight path. As a result, the launch was delayed for a few moments before proceeding again. The launch was scrapped officially after the liquid oxygen used to fuel the rocket became too warm, making a successful launch unlikely.

This is the third cancelled SpaceX launch for the current mission, which involves bringing an SES satellite into orbit. It’s possible the company will try again later this week.

Source Elon Musk