SpaceX is taking another crack at delivering supplies to the International Space Station and landing the rocket on an ocean barge.
The company's unmanned Falcon rocket is set to blast off before dawn Saturday from Cape Canaveral, Florida.
On Tuesday, steering-system trouble halted the countdown at the last minute. A suspect motor was replaced.
The rocket holds more than 5,000 pounds of space station supplies. NASA needs the shipment more than ever because of a launch explosion last fall that destroyed another company's supply ship.
Good weather is forecast for the 4:47 a.m. launch.
Once Dragon is headed to the station, SpaceX will attempt to fly the first-stage booster to a platform in the Atlantic for a vertical landing. Such a test is unprecedented.
