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Second Stage Ascent
T plus 7:40 minutes
Main engines throttled down to maintain acceleration below 3g's for structural limits.
T plus 8:30 minutes
Main engine cut off sequence begins.
T plus 8:33 minutes
Main engines throttled down to 65 percent thrust.
T plus 8:40 minutes
Main engine cutoff, automatic sequence confirms main engine shut down and begins external tank separation sequence.
T plus 8:58 minutes
External tank separates from orbiter.

IMAGE: Video of second stage ascent
During second stage ascent the shuttle shoots towards space after the boosters have separated.

IMAGE: Mission Basics

Space Shuttle Basics

Second Stage Ascent

The three space shuttle main engines, attached to the rear of the shuttle orbiter, continue to fire until about 8.5 minutes after liftoff, burning a half-million gallons of liquid propellant from the large, orange external fuel tank as the shuttle accelerates. The main engines burn liquid hydrogen the second coldest liquid on Earth at minus 252.7 degrees Celsius (minus 423 degrees Fahrenheit) and liquid oxygen. Since the hydrogen and oxygen can reach a temperature as high as 3,315.6 degrees Celsius (6,000 degrees Fahrenheit) as they burn higher than the boiling point of iron the engines operate at greater temperature extremes than any other piece of machinery ever built.

IMAGE: space shuttle main engines
The three space shuttle main engines propel the spacecraft into orbit for eight minutes and forty seconds after launch.

The engines' exhaust is primarily water vapor as the hydrogen and oxygen combine. As they push the shuttle toward orbit, the engines consume the liquid fuel at a rate that would drain an average family swimming pool every 25 seconds and they generate over 37 million horsepower. Their turbines spin almost 13 times as fast as an automobile engine spins when it is running at highway speed.

Eight and a half minutes after launch, with the shuttle traveling 8 kilometers (5 miles) a second, the engines shut down as they use the last of their fuel. A few seconds after the engines stop, the external fuel tank is jettisoned from the shuttle. The only part of the shuttle that is not reused, the tank re-enters the atmosphere and burns up over the Pacific Ocean. The shuttle orbiter, the only space shuttle component that will circle the Earth, weighs only about 117,934 kilograms (260,000 pounds). The shuttle has consumed more than 1.59 million kilograms (3.5 million pounds) of fuel during its first 8 minutes of flight.

Curator: Kim Dismukes | Responsible NASA Official: John Ira Petty | Updated: 03/16/2005
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