Endeavour looking good for launch – LON ability boost

by Chris Bergin

Endeavour is enjoying a smooth countdown ahead of Wednesday’s launch of STS-118, with no major issues being worked, as shuttle managers met at the L-2 MMT (Mission Management Team) meeting.

Meanwhile, External Tank technicians have cleared the sensor issue with ET-120 for flight, which was the uncertain element of Discovery’s LON (Launch On Need) requirement in support of STS-118.

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The launch countdown (S0007) started ticking down last night ahead of the Wednesday evening launch, which will see Endeavour lift-off on her first flight in nearly five years.

‘The STS-118 – S0007 LCD is currently proceeding on schedule according to the bar chart and we are on schedule for launch at 18:36:40 Eastern on August 8, 2007,’ noted the latest overview of status. 

A surprisingly short problem list, created Monday morning, points to a very healthy shuttle on the pad, with those the few problems noted receiving successful troubleshooting or waivers, thus clearing any constraint to launch.

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‘Ground Support Equipment (GSE) transducer is off scale low. Transducer was R&R’d (Removed and Replaced) and successfully retested,’ noted a couple of examples on processing information Monday.

‘Right GN2 tank is not closing out. There was a small GN2 leak in the GSE. Engineering has a manual work around for the automatic sequencer. This successfully worked with only a minimal delay in operations.

‘Panel L4 Inst OS circuit breaker (cb) was ‘closed’ and should have been ‘open’. Inadvertent switch throw on lighting cb. Will be closed as human error.’

Shuttle managers have been meeting today at the L-2 MMT meeting, although documentation shows that there are hardly any problems to be worked.

However, as discussed ahead of STS-118’s Flight Readiness Review (FRR), a review of the CSCS (Crew Shuttle Contingency Support) situation – the amount of days the STS-118 crew can stay on the ISS, should a problem arise with Endeavour – has been aided by the projected date Discovery – the LON shuttle for STS-118 – will be ready to launch in the case of a rescue.

This was under review in case engineers had to changeout some of ET-120’s liquid level sensors at KSC, sensors which had shown ‘high resistance’ problems via tests conducted at the Michoud Assembly Facility prior to being shipped. However, further tests have added confidence that the sensors can fly ‘as is’.

‘Received data on ET-120 LOX loading sensors (eight),’ noted Shuttle Standup/Integration information. ‘Prior to leaving MAF, four were shifted to higher resistances. Assessment indicates loose swage at sensors.

‘Rationale (for flight is) based on: 1) sensors believed to be functional (even wiggly sensors); 2) sensors that did not shift were very stable; 3) worked with PSIG on loading logic relying on stable sensors. Data shows additional shift on four sensors that shifted previously, but none on sensors they relied on remaining stable.

‘At MAF, identified additional data supporting that the logic sensors still work even if have resistance changes. Logic presented at FRR is intact for ET-120. Considered to still have a good LON tank.’

Meanwhile, the latest weather forecast evaluations for STS-118’s launch remain favorable, with a 70 percent chance of acceptable weather for Endeavour’s lift off.

‘An area of low pressure is developing off the coast of the South Carolina/Georgia border, and an associated surface trough is moving into the Central Florida area,’ noted an air force weather report, which was presented to Shuttle manager Monday morning.

‘Although the atmosphere has been too dry the past few days for Kennedy Space Center (KSC) to have afternoon thunderstorms, moisture will increase in the atmosphere today, and there is a 30 percent chance today of isolated thunderstorms over KSC.

‘An area of high pressure will develop in the Gulf of Mexico the next several days, and an upper level ridge will set in over the Eastern U.S.

‘As short wave troughs move through the upper levels and relative humidity increases through the atmosphere Tuesday and Wednesday, isolated coastal showers could affect the area. The offshore low may cause thunderstorms over the Gulf Stream, and the easterly flow aloft may bring the anvils from these thunderstorms into the area on launch day.

‘Still, overall, the weather pattern is favorable given an August day in Florida.’

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