Storms threaten SpaceX launch
SpaceX is back on the launch pad in hopes of making a critical delivery to the International Space Station.
Lift-off is scheduled for 3.25pm (8.25pm) today but stormy weather may force another delay.
Nasa's commercial supplier was foiled by a leaky rocket valve during Monday's launch attempt. The valve has been replaced.
The unmanned Dragon cargo ship contains 2.5 tons of station supplies, including material for urgent computer repairs.
A backup computer failed outside the space station last Friday.
Astronauts will conduct a spacewalk to replace the computer in the next few days.
Nasa says the material on the Dragon is desirable for the repair job, but not essential.
Much-needed food is also aboard, along with a new spacesuit and spacesuit replacement parts.