December 5, 2006
"Students at Christa McAuliffe's high school wildly cheered her blastoff today and then sat in stunned silence as the space shuttle Challenger exploded during its climb into orbit." (United Press International; January 28, 1986).
Christa McAuliffe, who taught social studies at Concorde (N.H.) High School, was the first teacher to fly into space when tragedy struck the Challenger on its 10th launch. As the world watched in horror, the space shuttle literally broke apart and took the lives of McAuliffe and her six fellow crew members.
Lift-off is one of the most dangerous times for astronauts flying on shuttle missions... the other is re-entry, as witnessed by the loss of the Columbia and its seven-member crew in 2003 after returning from a 16-day flight into space.
Now, the countdown is underway for the 33rd launch of the space shuttle Discovery on Thursday December 7th at 9.35 PM (EST). Read here and learn how NASA's engineers can get the 2,000 ton spacecraft off the ground and flying through the sky at over 20 times the speed of sound."
Developing the Launch Concept
Did You Know?
The first rocket was launched on March 16, 1926 in Massachusetts.
NASA's Space Shuttle program started in 1968. What engineers were looking for was a "two-stage" system where the shuttle could be launched like a rocket and land like a plane.
Their original design had a large winged vehicle ("Booster") sitting on top of a smaller winged vehicle ("Orbiter"). Both would be manned and launched in the vertical position. The idea was for the Booster to fly the Orbiter to an altitude of 80 km (50 miles) where they would separate. The Orbiter would fire up its engines and continue into space, while the Booster returned to earth.
But after crunching the numbers, the engineers realized that such a system would be too expensive. Many modifications later, they finally settled on a design — a reusable winged orbiter (where the crew are stationed), two reusable solid-fuel rocket boosters and an expendable liquid fuel tank.
Fuel for Thought
When fully loaded, the shuttle weighs 2,041,166 kilograms (4.5 million pounds). That's a lot of weight to send hurdling up into outer space. Let's look at the two key parts of the shuttle that provide the necessary power:
Solid Rocket Boosters (SRB)
The shuttle uses two SRBs, which are basically "rockets" each measuring 45.4 m (149 ft) in length. They are bolted to the launch pad and contain a solid fuel consisting of powdered aluminum (has a rubbery feel like a pencil eraser). When ignited, they generate a total of 29.4 million Newtons (6.6 millon pounds) of thrust (upward pressure), which is about 80% of the force needed for lift-off.
Did You Know?
The thrust of the SRBs is equivalent to 32 Boeing 747 jumbo jets running at maximum throttle.
The remaining 20% is provided by 3 engines located at the tail of the orbiter.
The main engines are supplied by the external tank. It is the largest component of the space shuttle and connects to both the orbiter and the SRBs. The tank is actually divided into two — the forward (upper) half contains 143,351 gallons of liquid oxygen and the back (lower) half holds 385,265 gallons of liquid hydrogen.
Did You Know?
The power generated by the main engines is 23 times more than that produced by the Hoover Dam.
"Go For Main Engine Start"
That's the command given at 10 seconds before lift-off... and puts in motion a series of events that pose a high risk for the astronauts.
First, flares are set off to burn away any residual hydrogen that may have accumulated under the main engines. Next, valves are opened to allow the hydrogen and oxygen from the external tank to flow to the engines, which are then ignited one after another.
Did You Know?
The rate at which fuel flows to the main engines is equivalent to emptying an average-size pool every 25 seconds.
Once the engines reach 90 percent thrust (about 3 seconds before lift-off), the SRBs are ignited. This is always left to last, because once the rocket boosters are started, there is no way of turning them off. Finally, small explosives blast away the bolts holding the SRBs to the launch pad.
Now things start cooking.
As the space shuttle rises from the launch pad, we see what looks to be a lot of smoke and flames. In fact, the "smoke" is steam from the evaporation of millions of gallons of water that are sprayed during lift-off to protect against fires and to muffle the sound waves.
T plus 2 minutes
Two minutes after the launch, the fuel in the SRBs has been used up and the shuttle is at an altitude of about 48 km and traveling at 4650 km/h. The boosters are separated from the shuttle and they continue to climb to 75 km before falling back to earth.
Did You Know?
The Challenger was 73 seconds into its flight when a structural failure on the shuttle caused liquid oxygen and hydrogen to spill. Although a huge fireball was created, the orbiter remained intact and continued to fly for 2 minutes and 45 seconds before hitting the ocean.
T plus 5 minutes
At an altitude of 5 km, parachutes on the SRBs are deployed so that they can safely fall to the Atlantic Ocean and be retrieved for future missions.
T plus 8 minutes
When the orbiter, now traveling at 27,000 km/h, reaches an altitude of 100 km, the main engines are shut off and the external tank is jettisoned (when it reaches the earth's atmosphere again, it will burn up).
Finally, a few directional adjustments are made and the orbiter is off to meet up with the International Space Station. It's now time for the astronauts, their families and the ground support team to relax a bit... at least until the orbiter has to return to earth in the next couple of weeks
For the past 19 years, biology teacher Philip Browne has taught students at McAuliffe's school about the history of flight into space. On each anniversary of the Challenger's tragedy, he takes students to visit her grave and the planetarium that was built in her honor.
"I don't want anybody to forget ... their bravery, their dedication. They were people who loved life. They wanted something better for the world" he recently told Associated Press.
1. National Aeronautics and Space Administration (NASA). Click here.
2. Kennedy Space Center. Click here.
3. Christa McAuliffe Planetarium. Click here.