Shuttle returns to pad for July launch

 作者:庾菩     |      日期:2019-02-27 01:09:03
By Kelly Young (Image: NASA) The US space shuttle Discovery lumbered towards its launch pad on Wednesday in preparation for a July launch – the first flight since the Columbia disaster in 2003. The trip is a familiar one for Discovery, which first rolled to its launch pad on 6 April. But NASA hauled it back to the Vehicle Assembly Building after atmospheric water vapour condensed into ice on a chilled liquid oxygen feedline on its external fuel tank. Workers then swapped Discovery’s external tank with one fitted with a heater to prevent ice build-up. NASA has worked to prevent ice from forming on the tank, since it could rain down during launch and potentially damage the shuttle. A chunk of falling foam from the tank punctured Columbia’s wing and doomed the orbiter to explode on atmospheric re-entry in February 2003. Discovery was initially scheduled to move to Launch Pad 39-B at the Kennedy Space Center (KSC) in Cape Canaveral, Florida, US on Tuesday morning. But technicians ran into delays in attaching the new tank and testing its connections. “That work just took a little longer than expected,” says KSC spokesperson Jessica Rye. NASA also changed the timing of the rollout from around dawn on Tuesday to the early hours of Wednesday morning to avoid exposing the shuttle to afternoon thunderstorms – a mainstay of Florida summers. The rollout comes after workers declared Discovery’s engines free of iron contamination,