STS-135 Launch Day

T minus hours, pending any delays, until the end of the era.  The next US venture into space is yet to be decided.  The shuttles served us well for the past 30 years.  Some stats:

- The fleet has traveled 537 million miles in 20,830 orbits around the Earth.

- 355 different men and women from 13 countries have made up the 848 crew launched

- 179 satellites, probes, and other components have been launched

- 52 components have been returned for analysis or repair (only the orbiter can return components)

Life spans of the Orbiters

At T-9 minutes a planned hold will end and the final steps to launch will lead up to the igniting of the solid rocket boosters.  The last 9 minutes are expected to go as follows:

Resume countdown at T-9 minutes (about 11:17 a.m.)

• Start automatic ground launch sequencer (T-9 minutes)
• Retract orbiter crew access arm (T-7:30)
• Start APU recorders (T-6:15)
• Start auxiliary power units (T-5)
• Terminate liquid oxygen replenish (T-4:55)
• Start orbiter aerosurface profile test (T-3:55)
• Start main engine gimbal profile test (T-3:30)
• Pressurize liquid oxygen tank (T-2:55)
• Begin retracting the gaseous oxygen vent arm (T-2:50)
• Fuel cells to internal reactants (T-2:35)
• Pressurize liquid hydrogen tank (T-1:57)
• Deactivate bi-pod heaters (T-1:52)
• Deactivate solid rocket booster joint heaters (T-0:50 seconds)
• Orbiter transfers from ground to internal power (T-0:50 seconds)
• Ground launch sequencer go for auto sequence start (T-0:31 seconds)
• Booster gimbal profile (T-0:21 seconds)
• Ignition of three space shuttle main engines (T-6.6 seconds)
• Booster ignition and liftoff (T-0)