Shuttle Discovery ready to lift off, weather permitting. Photo Credit/NASA TV
Discovery will be prepared for a Thursday launch attempt, NASA’s Mission Management Team decided following a lengthy review on Wednesday of an intermittent voltage irregularity in the circuitry of a backup main engine controller.
However, the passage of a cold front through Central Florida increased the odds of weather violations from scattered showers, low cloud ceilings and possibly severe thunderstorms to 80 percent at NASA’s Kennedy Space Center for a scheduled lift off at 3:29 p.m., EDT.
Mission managers will reconvene early Thursday to go over the weather forecast. An extremely dismal outlook might prompt a decision to hold off, said Mike Moses, the mission management team chairman.
During an 11-day mission, Discovery’s 39th and final flight, a six-member crew has trained to equip the International Space Station with an equipment storage module and an external spare parts rack as well as carry out two spacewalks for external maintenance..
The controller issue surfaced Tuesday, when the backup side of the No. 3 main engine controller failed to activate normally. Each of the three rocket engines is equipped with a primary and backup controller, which function like computers to operate the engines and alert the shuttle’s flight control system of a serious problem.
Following a period of normal activity on Tuesday, the controller experienced a small voltage drop.
MMT chairman Mike Moses called for a Nov. 3 to 4 launch delay, while engineers reviewed the performance history of the controller circuitry. Ultimately, the experts concluded some transient contamination in the circuit breaker was to blame. The circuit breaker was opened and closed multiple times to scrape away the contamination. Further testing showed normal operation.
High winds are forecast behind Thursday’s frontal passage. Blustery conditions forecast for Nov. Friday and Saturday pose potential launch pad and runway head wind violations. Discovery’s launch window closes after Nov. 7 because of high solar heating on the station’s orbital plane.