Shuttle Discovery heads for launch pad on Tuesday

Engineers are readying the shuttle Discovery for rollout to pad 39A early Tuesday, one day later than planned because of work to assess the impact of a check valve failure in the steering system of the ship's left-side solid-fuel booster. The valve problem apparently caused a hydraulic system pump to spin backwards during a high-pressure leak check, possibly damaging the pump and one of the booster's hydraulic power units, officials said. More

(Source: Spaceflight Now - Aug 4)