Cape Canaveral (FL) - NASA has postponed the planned launch of the space shuttle Discovery until at least March 15 (Sunday) due to "a leak associated with the gaseous hydrogen venting system outside the external fuel tank." The system is used to channel excess hydrogen gas safely away from the launch platform. The launch was originally planned for this evening at 9:20pm EDT after having already postponed it previously to inspect possible control valve cracks that were seen on last November's launch of Discovery's sister ship, Endeavour.
Liftoff is now scheduled for Sunday, March 15 at 7:43pm EDT, though the exact date and time "is dependent on the work necessary to repair the problem." NASA managers plan to meet tomorrow at 4pm EDT to further troubleshoot the cause of the leak and, if possible, solidify a revised liftoff schedule. Due to the rotation of the Earth, position of the International Space Station and the flight path required to get there, a consideration
According to NASA:
"Discovery's STS-119 flight is delivering the space station's fourth and final set of solar array wings, completing the station's truss, or backbone. The arrays will provide the electricity to fully power science experiments and support the station's expanded crew of six in May. The 14-day mission will feature four spacewalks to help install the S6 truss segment to the starboard, or right, side of the station and the deployment of its solar arrays. The flight also will replace a failed unit for a system that converts urine to potable water.
"Commander Lee Archambault is joined on STS-119 by Pilot Tony Antonelli and Mission Specialists Joseph Acaba, Steve Swanson, Richard Arnold, John Phillips and Japan Aerospace Exploration Agency astronaut Koichi Wakata. Wakata will replace space station crew member Sandra Magnus, who has been aboard the station for more than four months. He will return to Earth during the next station shuttle mission, STS-127, targeted to launch in June 2009."
The space shuttle's main engines are environmentally friendly. They burn hydrogen and oxygen in a controlled explosion which provides propulsion. The shuttle's two solid rocket boosters (SRB), however, operate on a solid propellant commonly referred to as Ammonium Perchlorate Composite Propellant, or APCP. It is comprised by weight of 69.6% ammonium perchlorate, 16% aluminum, 0.4% iron oxide, 12.04% polymer and a 1.96% epoxy curing agent. Aluminum is the primary fuel chosen because of its energy density (31.0Mj/kg). While the SRBs produce 1.8x the thrust of the liquid fuel Saturn V heavy lift rockets used to take man to the moon, they are responsible for leaving the huge trails of smoke seen when the shuttle launches. There is much debate over the extent of damage caused to the atmosphere by the shuttle's launches.
See NASA's shuttle website.