KSC-06-S-00158

Next on the NASA Space Shuttle Status Report: Space Shuttle Discovery is at the launch pad, her cargo is loaded and NASA is ready to launch_ And with the launch just days away, final preparations are under way at NASA's Kennedy Space Center. We have a mission overview. Plus, we'll take you from closeouts to the countdown right now. Stay right where you are. Space Shuttle Discovery is ready to fly again and the NASA Space Shuttle Status Report starts right now_ The Shuttle is at the pad, the crew is here, the payload is ready, and NASA is poised to launch mission STS-121 with a crew of seven to the International Space Station. I'm Tim Potter, NASA test director at the Kennedy Space Center in Florida, and this is the NASA Space Shuttle Status Report. On July 1 at or about 3:45 Eastern Daylight Time, NASA plans to return to flight once again. So, what does this mission entail? Mission STS-121 is a continuation of last summer's STS-114 return-to-flight test mission to the International Space Station. For this mission, Commander Steve Lindsey and his crew will continue evaluating new shuttle safety improvements. The mission is expected to last 12 days. They'll also carry supplies and a third member to the International Space Station. At least two spacewalks are planned. Now, here is a behind-the-scenes look at how the final days before flight will unfold. Now that the crew has arrived, they will participate in a few training exercises, then rest for the big day. Final vehicle closeouts are under way, and our landing teams have been deployed both here in the U.S. and in Europe. The countdown for this launch will be conducted by the NASA test directors from the brand new Firing Room 4 in the launch control center and will take about three days to accomplish. At T-3 days the cryogenic reactants that power Discovery’s fuel cells are loaded into the onboard tanks. At T-2 days, final preparations for the space shuttle’s main engines are done as well as activating Discovery’s communication systems. The ascent switch list, which configures Discovery’s systems for launch, is completed and then the rotating service structure, which has been protecting the vehicle during its stay at the pad, is retracted out of the way for launch. On launch day, at T-6 hours, the space shuttle's external tank is loaded with super-cold propellants. Once the tank is in stable configuration, a team heads to the launch pad for final inspections and the crew heads to the pad to board the space shuttle. Less than an hour before the launch window opens, a final 'go_no go' poll is taken. A number of things happen in the last few minutes prior to flight. At T-7 minutes, 30 seconds, the orbiter access arm is retracted. At T-5 minutes, the pilot starts the auxillary power units which provide the ship with hydraulic pressure to operate the flight controls that will keep the vehicle on its intended trajectory as it climes to orbit. At T-2 minutes 55 seconds, the liquid oxygen tank is pressurized, and one minute later, the liquid hydrogen tank is pressurized. At T-31 seconds, the onboard computers’ ground launch sequencer takes control of the final commands for launch. At T-6.6 seconds the command to start the main engines is given. And finally, at T-0 the solid rocket boosters are ignited and it’s launch time_ That’s all the time we have for this week’s Space Shuttle Status Report. Stay with NASA TV and nasa.gov as NASA safely returns to flight on mission STS-121 to the International Space Station July 1st. You will be able to see all the launch day activities right from your television set, computer screen or your iPod_ Live coverage of the countdown begins on NASA TV at 10 a.m. or you can log onto nasa.gov and experience the launch right from your computer. For the NASA Space Shuttle Status Report, I'm Tim Potter. The journey continues_