After a much anticipated launch of the space shuttle Discovery, NASA decided to cancel it for technical reasons.
Less than two and a half hours from lift off, as the astronauts were strapped in, they received word from mission control that the launch was being cancelled.
NASA says the problem is with a faulty tank sensor, and one of the four sensors was showing a low level of fuel when the tank was full with 535 thousand gallons of liquid hydrogen and oxygen.
The problem isn't expected to be a quick fix.
Discovery is not expected to launch until next week at the earliest.