Hell… I was all ready to post a link earlier today so you could watch the Endeavor shuttle launch and then NASA went and postponed it, as so often happens. Going into space is risky business and the slightest change of weather or the slightest thing that’s out of place, no matter how possibly inconsequential is a reason to recheck everything. So, Endeavor’s last flight has been postponed until at least Monday if not later.
During today’s countdown, engineers detected a failure in one of two heater circuits associated with Auxiliary Power Unit (APU) 1. Heaters are required to keep the APUs’ hydrazine from freezing on orbit. Attempts to activate the heater were not successful and engineers now believe the problem might be associated with a Load Control Assembly, which is a switchbox, located in the aft end of Endeavour, or an electrical short in the wires leading into or out of the switchbox.
Endeavour’s external tank will be drained, technicians will enter Endeavour’s aft compartment overnight and by tomorrow afternoon, will put in a platform to gain access to the avionics bay where the Load Control Assembly is located. Once there, they will assess whether they need to remove and replace the switchbox, or fix an electrical wiring short.
Because of this, Leinbach said there will be a minimum 72-hour scrub turnaround.