After two consecutive failures to launch because of bad weather conditions, on July 1 and 2, NASA's STS-121 mission is said to be "go" for the third time this July 4, 2006. "We're go to continue with the launch countdown," William Gerstenmaier, NASA's associate administrator of space operations, "I don't think we're taking any additional risks than we did in our original [flight] assessment."

Foam has been a long issue for the Discovery. This time there is too much foam loss, approximately less than one-tenth of an ounce. It fell from the uppermost bracket connecting a 17-inch liquid oxygen feedline to Discovery's orange external tank.

Although officials say that it is less than 50 per cent of the acceptable launch debris standards, there could be an ice build up of up to 0.0024 pounds and could fill the divot left by the liberated foam piece. Ice is also a potential launch debris risk.

NASA has been working on how to go around the foam issue for three years now. If you remember, this kind of matter caused the Columbia to sustain sizable damage during it's launch in January, 2003.

Discovery is now back on track to launch NASA's STS-121 mission on July 4. Liftoff is currently set for 2:37:55 p.m. EDT (1837:55 GMT), with current weather forecast predicting a 60 percent chance of favorable conditions for flight.