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Launch Timeline - PowerPoint PPT Presentation

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Launch Timeline. PowerPoint created by Shirley Garrett using Space Camp handout. T- and T+. T stands for Time T- stands for time remaining before the launch takes place T+ stands for time elapsed after liftoff. “T” – 43 hours.

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Launch timeline

Launch Timeline

PowerPoint created by Shirley Garrett using Space Camp handout

T and t
T- and T+

  • T stands for Time

  • T- stands for time remaining before the launch takes place

  • T+ stands for time elapsed after liftoff

T 43 hours
“T” – 43 hours

  • Is when the countdown to a shuttle launch begins. The countdown takes more than 43 hours. The clock stops at scheduled times for the technicians to do things to prepare for launch. These are called built in holds.

At t 6 hours
At T- 6 hours,

  • A 2-hour built in hold will take place.

  • The external tank is filled with 500,000 gallons of liquid hydrogen and liquid oxygen. It will not be finished being filled until just before liftoff.

At t 2 hours and 30 minutes
At T-2 hours and 30 minutes,

  • The crew will begin to ingress (or enter) the orbiter.

  • Once they are suited up for launch, the crew will leave the crew quarters. They will then ride out to the launch pad and take an elevator up the top of the launch pad, where they put on their helmets and get ready to ingress (enter) the orbiter.

At t 7 minutes thirty seconds
At T-7 minutes, thirty seconds,

  • The Crew Access Arm will be removed so it will not be damaged by the launch.

At t 31 seconds
At T-31 seconds,

  • Mission control will announce Auto Sequencer Start. Up until now, the shuttle is controlled by mission control. After Auto Sequencer Start the orbiter’s computers will be in control.

At t 15 seconds
At T-15 seconds,

  • Mission control will activate the Sound Suppression System. This releases 300,000 gallons of water onto the launch pad.

  • This prevents the accumulation of heat, but it also lessens the intensity of the sound that is produced.

  • Even with this system you must still be 3.5 miles away to prevent damage to your heart and ears.

At t 6 seconds
At T-6 seconds,

  • The Space Shuttle Main Engines ignite and the shuttle will sway slightly. This is called Twang.

  • Unlike the SRB’s, these liquid fueled engines can be turned off, so if a problem is detected launch can be stopped.

5 4 3 2 1 liftoff
5, 4, 3, 2, 1, LIFTOFF!!

  • When the countdown clock reaches zero, the solid rocket boosters are ignited. Explosives bolts allow the shuttle to leave the pad.

  • A successful launch is when the shuttle moves 2 inches above the launch pad.

At t 7 seconds
At T+ 7 seconds,

  • The shuttle clears the tower of the launch pad.

  • At this time the location of Mission Control changes from Kennedy Space Center to Johnson Space Center in Houston, Texas.

At t 10 seconds
At T+ 10 seconds,

  • The shuttle rolls over, so it will be on the right path to reach orbit. The Roll Maneuver also puts the External Tank on top so it will absorb most of the aerodynamic stress during the launch phase.

At t 1 minutes
At T+1 minutes,

  • The shuttle is reaching the speed of sound. MAX-Q, Maximum Aerodynamic Pressure. The pilot will throttle down the SSME’s to reduce pressure as the shuttle moves through the sound barrier. The SRB’s are designed to automatically slow down at this point.

At about t 2 minutes
At about T+2 minutes,

  • The Solid Rocket Boosters have used all their fuel. When they are released, they fall with parachutes into the Atlantic Ocean. There are ships waiting to tow the SRB’s back to Kennedy. They will be refilled in Utah and used on another mission.

At t 8 minutes and 40 seconds
At T+8 minutes and 40 seconds,

  • The SSME’s are turned off. This is called MECO (Main Engine Cut Off). This is done to prepare the Orbiter for ET separation.

  • After MECO, the astronauts start to float inside the orbiter.

At t 8 minutes and 50 seconds
At T+ 8 minutes and 50 seconds,

  • The External Tank is released from the orbiter. The ET falls away and burns up over the Indian Ocean.

At about t 10 minutes
At about T+ 10 minutes,

  • The orbiter is now orbiting 250 miles above Earth. The orbiter can only move by using the OMS and RCS thrusters. The OMS engines or the Orbital Maneuvering System are used for large movements in space. The 44 RCS or Reaction Control System engines make small movements. If the pilot wanted to get close to the Space Station, he would use the OMS engines to get close and the RCS engines to dock to the station.

At about t 1 hour and 30 minutes
At about T+1 hour and 30 minutes,

  • The Payload Bay doors open. The orbiter’s cooling system will not work without the doors open. The doors will remain open until it is time to get ready to land.

  • At this point the orbiter is traveling 17,500 miles per hour. The orbiter will remain in orbit from 7 to 18 days depending on the mission.

Time to come home
Time to come home!

  • The OMS engines will slow the orbiter so it falls out of orbit. The orbiter uses S-turns and the speed brake on the tail to slow down to 200 miles per hour for landing.

  • The pilot and commander will only have one chance to land. There is no fuel for the engines like there is on an airplane. On the ground, the drag chute and landing gear brakes will stop the orbiter.

  • Welcome Home!