Discovery Still Go for Launch

Shuttle set to fly at 3:51 p.m. local time

Cape Canaveral, Fla., 12 July 2005--Almost obscured in the haze, the space shuttle Discovery sits on its launchpad in the stifling heat and humidity of the Florida summer, but most eyes are on the skies at Kennedy Space Center (KSC) in Cape Canaveral, as the countdown continues for a Wednesday launch. Hurricane season has started early and with a vengeance. Florida is still picking up after hurricane Dennis swept through the area last weekend and another hurricane--Emily--is already brewing in the Atlantic. NASA's forecasters, however, are cautiously optimistic, putting the chances that the weather will be okay for launch at 60 percent.

If Discovery can't launch tomorrow at its appointed time--3:51 p.m. Eastern Savings Time (7:51 p.m. Greenwich Mean Time)--it will have to wait almost 24 hours for another attempt on Thursday. The practicalities of orbital mechanics mean that the shuttle must launch within a few minutes of its launch time or it will be unable to rendezvous with its destination, the International Space Station (ISS). If the launch can't go ahead on Thursday, KSC will stand down for a day to give the launch crews a break, and try again on Saturday.

NASA can keep trying until 1 August, when new rules established in the wake of the 2003 loss of the shuttle Columbia would mean the Discovery--and the crew of the ISS who are awaiting much needed parts and supplies--would have to wait until September before another attempt. These rules mandate that both the launch and the landing of the Discovery must take place during daylight so that ground- and air-based cameras can photograph the shuttle to verify that no piece of debris--like the chunk of insulating foam that mortally wounded the Columbia--has struck the Discovery.

In the two years since the Columbia disaster, much of NASA's efforts have gone into eliminating or reducing potential sources of debris, especially from the giant external tank, which holds the 726 000 kilograms of cryogenic propellants that feed the space shuttle main engines during the spacecraft's 8-minute ascent. It was foam from this tank that struck the leading edge of Columbia's left wing, knocking an approximately 30-centimeter hole that let in superheated air during the shuttle's descent, destroying the Columbia.

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