Tuesday’s launch of an unmanned cargo ship to the International Space Station by a private company was canceled shortly before lift-off from the U.S. spaceport in the southeastern U.S. state of Florida.

The countdown for the launch of SpaceX’s Falcon 9 rocket was halted with just over one minute left due an unexpected technical problem. The U.S. space agency NASA says it will attempt to launch the cargo ship early Friday morning.

The rocket will send more than 2,000 kilograms of supplies loaded on SpaceX’s Dragon cargo capsule to the ISS.  But the mission’s main feature is due to happen minutes after launch, when the the rocket’s 14-story-tall lower stage will separate from the upper stage, which will carry the cargo ship into orbit.  The lower stage’s rockets will then automatically refire and and try to guide it to a safe landing on a huge sea-based platform.

A successful landing will put SpaceX one step closer towards its goal of employing reusable rockets in future flights, which the company says will drastically lower the cost of rocket launches. The company has conducted test landings of the first stage on prior supply flights to the ISS, but both of those rockets landed in the ocean.

SpaceX founder and chief executive Elon Musk puts the chances of success at no greater than 50 percent.

Friday’s rescheduled launch is the first resupply mission to the ISS since a rocket owned by Orbital Sciences Corporation, the second private company under contract by NASA to ferry cargo to the orbital outpost, exploded shortly after liftoff in October, destroying cargo as well as a dozen student experiments.

The experiments have been reconstructed and are will be sent to the ISS aboard the SpaceX vehicle.

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