Shuttle Challenger Accident

QUESTION:

How, why, and where did the space shuttle Challenger go down in 1986?

ANSWER:

The Space Shuttle Challenger broke up on Tuesday, January 28, 1986 at 10:38 AM  Tomah time (CST). Launched from Kennedy Spacecraft Center, the 25th Shuttle mission, the vehicle with seven astronauts aboard, disintegrated 73 seconds into launch. It was about  9 miles high and going about  1500 miles per hour. Because it was moving so fast, the crew compartment traveled another 3 miles up before it reached its peak altitude of about 12 miles.

All shuttle flights are launched toward the east out over the Atlantic Ocean. The rotation of the Earth from west to east imparts a speed of close to 1000 mph in the direction the Shuttle is going. It’s like a free “kick in the pants”. The speed needed to get into orbit around the Earth is 17,500 mph, which works out to about 5 miles per second.

What was the cause of the accident? The Shuttle is powered by 3 main engines that are fed liquid hydrogen and liquid oxygen, both stored in a large External Tank. The Shuttle is also powered by two Solid Rocket Boosters (SRB’s), one on each side of and strapped to the External Tank. The fuel is ammonium  perchlorate (oxygen) and aluminum (fuel). It is poured in the casting, much like pouring fudge candy, and hardens. It feels like a pencil eraser.

The SRB’s are about 150 feet long and made in 4 segments, designed so each segment fits on a railroad car and can be railed back to Utah for refilling.

The Shuttle was destroyed after the lowest joint on the right hand SRB failed. The two O rings allowed a breach or opening for extremely hot gases from inside the rocket engine to hit the SRB attachment hardware, then the External Tank.

Two events happened at about the same time. The hydrogen tank, the lower part of the External Tank, ruptured due the hot gases burning through the tank, and the SRB pivoted into the top of the ET.  It was aerodynamic forces that tore the Shuttle apart, not the big explosive fireball we see on TV and in pictures. The SRB’s were remotely destroyed by the Range Safety Officer before they could come back over land and do damage.

A cold weather system has moved through Florida the night before the launch. The cold temperatures made the O rings brittle and not able to seal properly. Even so, the Shuttle might have made it through the 130 seconds needed for the SRB’s to burn, except for the sheer winds at altitude that buffeted the vehicle.

Investigation and analysis after the accident indicated that when Challenger broke apart, the crew compartment remained intact. Several of the emergency oxygen packs had been turned on. Investigations after the accident, showed that the oxygen remaining in the tanks was consistent with the expected usage during the 2 minutes 45 second fall to the ocean.

But the seven astronauts could not have survived the impact with the ocean, hitting the water at over 200 mph. The crew compartment was found 6 weeks after the accident in several hundred feet of water and roughly 20 miles east off the Florida coast. The bodies of all seven crewmembers were found strapped in their seats. They were returned to their families. Scobee and Smith were buried in Arlington National Cemetery, McNair in Lake City, South Carolina, Onizuka in the National Cemetery in Hawaii, Jarvis and Resnick were cremated and ashes scattered over the ocean.

Teacher Christa McAuliffe was interned in Concord, New Hampshire, not far from the classroom in which she taught.

 

 

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