An unmanned SpaceX Falcon 9 rocket taking supplies to the International Space Station (ISS) exploded just 2 minutes and 19 seconds into its mission, showering burning debris into the Atlantic off Florida's coast.
The 208ft (63m) rocket, privately owned by billionaire entrepreneur Elon Musk, was due to deliver food, scientific equipment and other supplies to the ISS on behalf of Nasa. The Falcon 9 was also carrying a school science experiment to see how worms behave in space and an International Docking Adaptor, designed to allow a wide variety of spacecraft to dock.
A video on the SpaceX website shows the rocket taking off and apparently operating normally as it accelerates into the sky. However, as it reaches supersonic speeds at a height of 27 miles something causes it to explode in spectacular fashion.
An update on the SpaceX website said: "The vehicle experienced an anomaly on ascent. Team is investigating. Updates to come."
Elon Musk, who was celebrating his 44th birthday, tweeted: "There was an overpressure event in the upper stage liquid oxygen tank. Data suggests counterintuitive cause."
He added: "That's all we can say with confidence right now. Will have more to say following a thorough fault tree analysis."
This is the latest setback for SpaceX, which has recently made two attempts to land reusable rockets aboard floating barges in the ocean. Both attempts failed. Musk tweeted after one of the attempts: "Close, but no cigar."
Refuelling the ISS has posed a problem for Nasa, which discontinued its own Space Shuttle programme on cost grounds in 2011. Last October (2014) a rocket owned by another private company exploded on the launch pad. In April this year a Russian spacecraft fell out of control.
The three astronauts aren't in immediate trouble, as they have sufficient supplies for four months.
Astronaut Scott Kelly Tweeted from aboard the ISS: "Watched #Dragon launch from @space_station Sadly failed Space is hard Teams assess below @NASAKennedy #YearInSpace".
A Russian craft will make another attempt at resupplying the ISS next Friday (3 July).