Clocks begin ticking for Wednesday's blastoff
BY WILLIAM HARWOOD
STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION
Posted: September 3, 2006
The countdown began at 8 a.m. for a launch try Wednesday at 12:29 p.m., a week and a half behind schedule because of a launch pad lightning strike Aug. 25, which prevented an Aug. 27 launch, and then tropical storm/hurricane Ernesto.
As with Atlantis' first launch try, the 76-hour 23-minute countdown began six hours earlier than normal. That will give engineers a better chance of getting the shuttle's fuel cell system loaded with liquid oxygen and hyrogen Monday morning before any afternoon storms can develop and provide additional time to handle unexpected problems.
The latest Air Force weather forecast calls for an 80 percent chance of acceptable weather Wednesday, dropping to 70 percent "go" Thursday and Friday.
"Our primary concerns for launch are cumulus clouds within 10 nautical miles of (launch) complex 39B and isolated showers within 20 nautical miles of the Shuttle Landing Facility," according to the forecast.
"The probability of KSC weather prohibiting launch increases slightly the following two days due to a frontal boundary approaching Central Florida from the northwest. This boundary with strong upper level winds from the west may cause anvil clouds from thunderstorms in the Gulf of Mexico and along the west coast of Florida to (move) east toward KSC."
NASA safety rules forbid a launch if electrically active anvil clouds move within a few miles of the launch site.
A detailed countdown chart is posted here.
Here is a summary of countdown highlights (in EDT):
Sunday 09/03/06 08:00:00 AM Countdown begins Monday 09/04/06 12:00:00 AM ** Begin 4-hour built-in hold 04:00:00 AM ** Resume countdown 05:30:00 AM Fuel cell oxygen loading begins 08:00:00 AM Fuel cell oxygen load complete 08:00:00 AM Fuel cell hydrogen loading begins 10:30:00 AM Fuel cell hydrogen load complete 12:00:00 PM ** Begin 10-hour built-in hold 10:00:00 PM ** Countdown resumes (now in synch with standard count) Tuesday 09/05/06 06:00:00 AM ** Begin 13-hour 33-minute hold 03:00:00 PM ** Rotating service structure to park position 07:33:00 PM ** Resume countdown 08:43:00 PM Fuel cell activation 10:33:00 PM Final fueling preps; launch area clear Wednesday 09/06/06 12:33:00 AM ** Begin 2-hour built-in hold (T-minus 6 hours) 01:03:00 AM ** External tank ready for fueling 01:23:00 AM ** Mission management team go/no-go tanking meeting 02:33:00 AM ** Resume countdown (T-minus 6 hours) 02:33:00 AM Liquid oxygen/hydrogen transfer line chilldown 02:43:00 AM Liquid hydrogen (LH2) slow fill 03:03:00 AM Liquid oxygen (LO2) slow fill 03:23:00 AM LO2 fast fill 03:33:00 AM LH2 fast fill 05:33:00 AM ** Begin 3-hour built-in hold (T-minus 3 hours) 05:33:00 AM ** External tank in stable replenish mode 07:59:00 AM ** Astronaut weather briefing 08:09:00 AM ** Astronauts don pressure suits 08:33:00 AM Resume countdown (T-minus 3 hours) 08:39:00 AM Astronauts depart crew quarters 09:09:00 AM Crew straps in 09:58:00 AM Astronaut communications checks 10:23:00 AM Hatch closed 11:13:00 AM ** Begin 10-minute built-in hold (T-minus 20m) 11:23:00 AM ** Resume countdown (T-minus 20m) 11:24:00 AM Backup flight computer loads OPS 1 software 11:34:00 AM ** Begin final built-in hold (T-minus 9m) 11:44:49 AM ** NASA test director launch status verification 12:19:49 PM ** Resume countdown (T-minus 9m) 12:23:49 PM Hydraulic power system (APU) start 12:25:54 PM LO2 tank pressurization 12:26:52 PM LH2 tank pressurization 12:28:18 PM Shuttle computers take control of countdown 12:28:49 PM LaunchIf Atlantis is delayed Wednesday, the crew will have two more launch opportunities before the current September launch window closes: at 12:03:07 p.m. Thursday and at 11:40:35 a.m. Friday. After that, the flight would be delayed to late October unless NASA relaxes a self-imposed requirement to launch Atlantis in daylight. NASA managers are in the process of reviewing that rationale.
The official crew patch for the STS-115 mission of space shuttle Atlantis to resume orbital construction of the International Space Station.
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