CAPE CANAVERAL, Fla. (AP) — NASA's top spaceflight official says it's "a tough day" for the space agency, after an unmanned SpaceX rocket broke apart minutes after launch.

The rocket was headed for the International Space Station with a cargo of supplies, including a first-of-its-kind docking port. It's the second consecutive failure of a shipment to the space station and the third in eight months.

In April, a Russian cargo ship spun out of control and came down. And last October, another company's supply ship was destroyed in a launch accident.

NASA official William Gerstenmaier says there was nothing common among the three accidents, "other than it's space and it's difficult to go fly."

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