UPDATE — Shuttle Launch Delay: What Happened and What’s Next

NASA’s space shuttle Discovery is scheduled to lift off from the Kennedy Space Center tonight — March 11, 2009 — at 9:20 p.m. EDT. You can watch the shuttle launch live, plus keep an eye on all the activity leading up to it during the day, right here.

Space Shuttle Discovery: The Delays

NASA scientists had pushed back Discovery’s launch by about a month because of tiny cracks discovered in the engine compartment’s hydrogen valves. Crews ended up replacing all of the shuttle’s valves as a safety precaution and now say the shuffle is safe to travel.

Discovery’s Mission

Discovery’s mission will include four spacewalks on which astronauts will install a 31,000-pound addition to the International Space Station. The truss, as it’s called, has two solar array wings that’ll convert solar energy into power for the station. It is the final piece of the station’s new backbone. Discovery will also bring a replacement for that much-discussed system that converts astronauts’ urine into drinkable water.

Discovery’s crew is made up of Commander Lee Archambault; Pilot Tony Antonelli; Mission Specialists Joseph Acaba, Steve Swanson, Richard Arnold, and John Phillips; and Japan Aerospace Exploration Agency astronaut Koichi Wakata.

Shuttle Launch Live 2009 Webcast

Below is a live stream from the Kennedy Space Center, courtesy NASA TV. (Note that NASA may come in and out of coverage during the afternoon hours. Nonstop coverage should begin by evening.) You can find the minute-by-minute breakdown of Discovery’s timeline on our Space Shuttle Launch Schedule 2009 page.