From Orlando Sentinel.... The proposed Monday launch of the space shuttle Endeavour has been scrubbed and NASA officials are not yet sure when they will reset the blastoff, NASA spokesman Mike Curie said. Tuesday and Wednesday launches also have been ruled out. There is a chance for an end-of-the-week launch, but only NASA can squeeze it in after the Air Force launches its own rocket, an Atlas V, on Friday, May 6 from Canaveral Air Force Station, adjacent to Kennedy Space Center. NASA officials are checking with the Air Force to see if the launch might be delayed. If that is not possible, and NASA cannot squeeze an Endeavour launch in on Saturday, the next opportunity might not be until Tuesday or Wednesday, May 10 or 11. That’s because the Russians are launching a Soyuz to the International Space Station, and Endeavour would have to wait until it leaves before the shuttle can dock there. NASA has determined that the problem that caused them to scrub Friday’s original attempt is contained in a switchbox called the load control assembly, rather than in a thermostat, a NASA spokesman confirmed Sunday morning. The load control assembly is much more difficult to reach and will require perhaps two days of testing by engineers before it can be fixed and replaced. That determination dashed hopes of NASA officials who hoped that the technical glitch was in a thermostat, which could have been swapped out easily allowing for a Monday launch attempt. On Friday, NASA scrubbed the original launch attempt shortly after noon when one of the heaters on a fuel line that powers the craft’s hydraulic systems appeared to be failing. Those hydraulic systems in turn control the pilot’s ability to maneuver the shuttle in the atmosphere. If the heaters don’t work, the fuel lines could freeze and rupture, and the hydraulics might fail. NASA doubles up all systems, and consequently there are two string heaters wrapped around each fuel line. Only one heater string was failing, launch director Mike Leinbach said. The other would be enough to keep the shuttle flying fine, but NASA did not want to lose the protection of redundancy. NASA began planning for a Monday launch under the hope that the problem was in the thermostat. But after technicians got to the aft compartment on the shuttle Saturday night they tested the thermostats and concluded they were fine. That led to the conclusion that the problem is in the switchbox that controls the thermostat, the load control assembly. Exactly why it failed is unclear. More details will becoming available after a press conference NASA has called for this afternoon.