Alligators & Rocketships

Pre-Launch

Shuttle Stack up 5 Percent Slope	As the stack nears the pad, hydraulic lifters raise the rear of the crawler as much as six feet to keep the Shuttle vertical while climbing the five percent slope up to the pad's surface. During most of its stay at the pad, the Rotating Service Structure is rolled around the orbiter to provide access for technicians, engineers, and inspectors, as well as to protect it from the weather and birds. The Shuttle will stay at the pad for at least a month undergoing final preps for flight. These preps include putting the payload in the payload bay and performing interface testing, loading hypergolic propellants, installing the pyrotechnics (ordnance devices), and practicing countdown with the crew. Then, approximately four days prior to launch, the countdown begins.	Shuttle Launch Pads Shuttle on Pad-Rotating Service Structure Open
External Tank	About 18 hours prior to the actual launch, the Rotating Service Structure is finally rolled away from the Shuttle. The external tank is filled with liquid hydrogen and liquid oxygen (about nine hours before launch). Liquid hydrogen flows through the main propulsion system piping and main engines to chill them down to approximately minus 420 Fahrenheit just prior to launch. This loading process will take almost three hours, which is a long time compared to the eight-and-a-half minute drain during ascent.
Pre-launch Breakfast	Before launch, the crew will be awakened, have breakfast, get suited up, and depart for the launch pad. They will begin boarding the vehicle about two and a half hours before launch, and with less than one hour to go, the closeout crew will close the hatch and vacate the area.	Boarding the Crew Transport Vehicle
Personnel are required to don cleanroom-grade clothing ensembles before entering the crew compartment and follow cleanroom rules and regulations. Prior to crew compartment entry, materials and equipment must be checked by an orbiter integrity clerk stationed outside the white-room entrance for compliance to program requirements.		In the White Room -- Boarding the Vehicle