SpaceX was forced to abort the launch of its Falcon 9 mission to the International Space Station on Saturday, just half a second before liftoff.
As SpaceX CEO Elon Musk points out in a tweet, "Recalling rockets after launch is not an option".
The launch was aborted when the flight computer detected slightly high pressure in the engine 5 combustion chamber, possibly because too little fuel was flowing into the engine.
"During rigorous borescope inspections of the engine, SpaceX engineers discovered a faulty check valve on the Merlin engine," says the company. "We are now in the process of replacing the failed valve."
Initial tests show that the new valve is working properly.
The two-week mission will mark the first time a privately constructed spaceship has ever docked with the ISS. It's a test flight, designed to check out the poeration of the ship's sensors and automatic propulsion systems.
In December 2010, SpaceX made history by becoming the first private company to send a spacecraft into orbit and back.
The company now plans to try again tomorrow at 3.44 am if repairs are successful; there'll be another opportunity early Wednesday morning. The weather looks good for tomorrow's slot.
"We're ready to support when SpaceX is ready to go," says Alan Lindenmoyer, NASA's manager of the Commercial Crew and Cargo Program.