Subject: pre-launch and post-abort Shift report Date: Tue, 20 Jul 1999 02:42:03 -0400 From: "Paul P. Plucinsky" hi Folks, We got real close tonight, 8s away from launch before there was a manual override to abort launch. There was a reading on the primary H2 sensor in the aft engine compartment which indicated the H2 level was 624 ppm and the limit is 5 ppm. The reading was transient and dropped below 5 ppm in a short time. The redundant sensor never indicated there was a reading higher than 5 ppm. Nevertheless, the KSC folks had to intervene and manually abort launch based on the primary reading. A human operator called a cutoff at 8s before launch and we all know that main engine start is 6s before launch. So, the KSCteam moved very quickly to abort the main engine start. The KSC folks are working the problem and the plan now is to go for a 48 hr recycle. THERE WILL NOT BE ANOTHER LAUNCH ATTEMPT IN 24 hrs; so get some sleep. If it is simply a faulty reading in the sensor, we should be in good shape for a 48 hr recycle. If it is truly a leak in the engines, we have a much longer delay ahead of us. The KSC team plans to replace the balky sensor and they need at least two days to do the repair. Other than that, the countdown went smoothly. There were no problems in the TST or the OCC; we were all ready for launch. KSC says that they only had 3 minor problems in the countdown. Both ACIS and HRC agree that a 96 hr delay is acceptable. This would allow us two more launch attempts before the window supposedly closes on Saturday. Both ACIS and HRC have been asked to asses the possibility of holding more than 96hr. The teams need to work the issue tomorrow. We also need to assess if EPHIN can tolerate a 96hr delay. stay tuned, Paul