Space Shuttle Discovery appears to have so far jumped the hurdle that caused a launch scrub on July 13, as all four Engine Cut Out (ECO) sensors passed testing during the start of propellant loading into the External Tank (ET) in the early hours of Tuesday morning.
Discovery is due to launch at 10:39am EDT (3:39pm UK time) with even the weather improving chances of launch to 80 percent. Several factors remain, with the all important T-9 minutes hold a crucial time for the Shuttle – as she checks over all her systems ahead of the first launch in two and a half years.
Several factors remain, with the all important T-9 minutes hold a crucial time for the Shuttle – as she checks over all her systems ahead of the first launch in two and a half years.
However, the ECO issue – where LH2 sensor 2 failed to correctly tell Discovery what its status was – appears to have been solved by grounding work (to protect against Electromagnetic interference) and creative wiring.
“Well, it appears that the ECOs are working fine,” said a source this morning. “A couple minutes after we had ALL eight ECOs go wet (in both tanks) they turned on the SIM circuit, so that all eight ECOs indicated DRY. This is exactly what we wanted to see, and it also indicates that they’ve fixed the problem.
“As we thought, it was probably the wiring in the Orbiter (what was in there before was out-of-spec as far as grounding/shielding). That’s pretty much all they did, was to replace the bad wiring in Discovery… and probably all they really needed to do!
“The ECOs will remain in this test mode until the crew is loaded (should be any minute) and then I think they’re planning to switch them back to normal operation (i.e. will indicate WET).”
More tests remain to prove the problem has indeed been fixed, as Discovery sits on the pad – passing the T-3:00:00 hold.
“I believe they will re-test them later in the count, and hopefully we’ll get the same readings we’re getting now.”
Second test passed:
“They removed the SIM commands, and the sensors – all eight – returned immediately to WET, as we hoped,” noted the source. “Apparently there is still one more test to be performed, which is an OMRSD req’t. Not expecting any problems.”