Sunday at 3:15p.m.: Good news: we each asked a question at the press briefing, which you can see in repeats on NASA-TV today! Anna asked about how they make some of the determinations to send the astronaut crew home. Doug asked a technical question about the load control box, which is being replaced in hopes of fixing the problem that’s delayed the launch. In fact, Doug’s question and the official answer leads us to think that maybe the box is the source of the problem, but maybe something upstream in the electronics caused the short in what is essentially like a circuit sub-panel you’d have in your garage or laundry room.
That leads us to the bad news: the earliest possible launch date is May 8, and that seems incredibly optimistic, even though Launch Integration Manager Mike Moses called it a “typical electronics failure.” Tomorrow, engineers will remove the problematic box, which will be examined to prove that the failure occurred there. While that forensics work is being done, a new load control box will be inserted in the aft avionics bay of the space shuttle. Engineers will guide the 40- to 50-pound box into place using guide rails. Once in place, all nine systems connected to the box must be tested upstream. In other words, it would be like replacing that sub-panel in your garage, then turning on each light bulb and the washer and the dryer in order to ensure the whole system is working properly and that each individual component is receiving adequate power. That testing takes a full two days, and as Doug’s question implied, that testing could lead them to discover that the electrical problem lies upstream in one of the nine systems, perhaps some debris or a bad solder on a line or something else.
As the team on Launch Pad 39A makes progress over the next day or two, the launch management team will look at the mission schedule to determine the next reasonable launch date. For instance, a May 9 launch with the extra days they want to add to the mission, for a total of 16 days in orbit, would put Endeavour‘s undocking from the International Space Station (ISS) on the same day as the scheduled Soyuz undocking. Those two events must be decoupled because ISS, shuttle, and Soyuz crew workloads and sleep shifts are adjusted for different tasks, such as launch, undocking, and landing. Undocking on the same day would require two crews working different schedules, when even astronauts are human and, therefore, need some rest.
And of course, if the delay gets extended past a certain point, Endeavour’s launch could push Atlantis‘s launch further into the summer. The exact time needed between launches depends not just on getting Endeavour off the pad to make room the next shuttle, but also on preparing the pad for the last space shuttle launch, which depends upon how much damage is done during Endeavour’s launch. The hard-working folks at KSC can’t start cleaning up after Endeavour until she actually leaves the Earth, and we just don’t know when that will be. Despite the optimism of Shuttle Launch Director Mike Leinbach that May 8 is possible, we just can’t imagine that any time before May 10 is realistic. We should all know more tomorrow or Tuesday.