How long does it take for a space shuttle to get out of Earth’s atmosphere? — Nick, Hampshire, Ill.
Marshall Brain Answered:
To answer this question, the first thing we have to decide is where the earth’s atmosphere ends. This is not simple because Earth’s atmosphere is continuous. It gets thinner and thinner as you get farther from earth, but there isn’t really a hard line where space begins. One generally accepted definition is 100 kilometers (62 miles) up, aka the Karman Line. See this page for details.
So we can ask, How long does it take the shuttle to reach an altitude of 100 kilometers?
The solid rocket boosters burn for about two minutes, and they fall off about 30 miles up. So they get the shuttle about half way there. In addition, they helped the shuttle accelerate from zero to 3,500 MPH in two minutes. So it doesn’t take long to go the next 32 miles. Not only is the shuttle going 3,500, but it is accelerating. It will be traveling at a speed of 17,000 MPH six minutes later.
Let’s ignore the acceleration (this page indicates the shuttle is only going 3,887 MPH at 2:26). At 3,500 MPH, the shuttle is traveling approximately one mile per second. That means it only takes 32 seconds more to reach an altitude of 62 miles. If you want to take acceleration into account, it is a few seconds less.
So it takes approximately 150 seconds for the shuttle to get out of earth’s atmosphere.
Here’s what it looks like when the SRB detatches:
For more info see: How Space Shuttles Work