14 DAY TRIAL // After two consecutive days in which mishaps prevented the space shuttle Discovery from launching, mission controllers have again initiated the countdown sequence for the STS-128 assembly flight to the International Space Station. The spacecraft is now scheduled to take off at 12:22 am EDT (0422 GMT), on Friday morning. The decision to allow Discovery's flight was taken only after five successful tests at opening and closing the troublesome valve that prevented Discovery from taking off recently.
The valve “didn't break itself apart. All five times it did exactly as it was expected to do. They can take that to the mission management team Thursday for discussion,” Allard Beutel, a NASA spokesperson, told Space on Wednesday. If today's scheduled meetings are conclusive, and mission controllers, planners and agency officials agree to allow the shuttle to fly, then the fueling procedure will start at around 3 pm EDT (1900 GMT). Some 526,000 gallons of super-cold liquid hydrogen and liquid oxygen propellants need to be added to the shuttle's 15-story external tanks during this step.
Even if the early morning attempt at launching the mission fails, for technical reasons, the space agency still has another window later in the day, at 11:59 pm EDT (0359 GMT, August 29th). If, however, engineers decide that more work is needed on the valve, then the entire flight will be postponed until October 17th, as the last launch window closes on August 30th. In September, two flights are scheduled to the ISS, one from a new type of Japanese unmanned space probe, and the other from a Russian Soyuz capsule, which will ferry up new crew members and supplies for the ISS.
In addition to the valve, engineers also discovered a small hydrogen leak on the main tank. Although it is well under the agency's safety limits, mission controllers opted to investigate it as well, especially given the fact that it is located fairly close to the defective valve. In order for shuttles to launch, their two fuel valves, one for hydrogen and the other for oxygen, need to work exquisitely well. Any glitches in these instruments, and any launch attempt could end in tragedy. Therefore, it remains to be seen whether Discovery will launch tomorrow. Consent must be achieved at meetings today, in order for this to happen.