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Introduction To The Accident Essay, Research Paper

It was a clear sunny day at Kennedy Space Center in Florida with a temperature of 36 degrees which was 15 degrees cooler than NASA has ever sent a shuttle to space. Aboard the space shuttle was a civilian school teacher which made the Challenger such a publicized event. After being delayed five times from bad weather the Challenger was schueled to be launched at 11:38 AM Eastern Standard time on January 28, 1986. Seventy-three seconds after leaving the launch pad 39B the Challenger would explode.

The Challenger Tragedy

The problems started .6 seconds after ignition. With the temperature

at 15 degrees below the NASA experience mark, a black smoke started

to come out of the bottom field joint of the right SRB. The black smoke was the O-Rings and the joint insulation being burned. The smoke averaged at about three puffs per second. Then the last puff of smoke was seen was at 2.7 seconds which was an indication that the field joint was not sealed correctly.

The arrow points to the black smoke.

The second problem was at forty-five seconds when three bright flashes were seen on the Challenger’s wings. Each flash lasted approximately one thirteenth of a second. When the film was enhanced it is clearly visible that the flashes were coming from the right SRB. The three hundred and five degree flame was coming from the aft center of the aft joint of the SRB. The flame was the gas burning that was coming out of the SRB. At fifty nine point three seconds the flame was clearly visible with the naked eye. As the flame increased in size, the flame had begun to push against the external tank by the rushing air around the orbiter. This made the struts that held on the SRB very weak because of the heat. Sixty four point seven seconds was the first sight that the flame was hitting the external tank. The color of the flame changed. The flame color change indicated that the flame was mixing with the hydrogen substance that the external contained. The top tanks were oxygen and the bottom was hydrogen. The flame also indicated that there was a leak in the hydrogen portion of the external tank. A small glowing light appeared between the external tank and the Challenger’s black tiles forty-five milliseconds after the color change.

The small orange glowing light is visible.

When the clock was at 72 seconds there was a sudden chain of events that destroyed Challenger and the seven crew members on board. All of these events happened in less than two seconds. By now the lower strut, that connected the right SRB to the External Tank was very hot and very weak. With the amount of force given by the SRB, the lower strut broke off and away from both the right SRB and the External Tank. Which allowed the right SRB to rotate freely around the top struts. The SRB was out of control, the bottom of the SRB swung around hitting, burning and denting Challenger’s wing. At 73.12 seconds into flight a white vapor was seen from the bottom corner of the right SRB. The External Tank was weak because of the intense heat which the flame had produced. The dome structure under the External Tank failed and fell.

The hydrogen inside the external tank acquired a hole and started to release liquid hydrogen contents. Since the hydrogen was out of it’s tank the tank shot forward hitting the oxygen tank which also burst. The white vapor seen was the hydrogen and the oxygen mixing. Milliseconds after the white vapor was seen there was an explosion. The challenger was traveling at the speed of Mach 1.92 and at 46,000 when the hydrogen and oxygen exploded. Before the challenger exploded there was a cloud of gray smoke that engulfed the challenger which grew larger but under the gray cloud there was a red smoke which was the control system burning from the wreckage of the challenger . All sorts of debris was falling off of the challenger towards the ocean. Both of the SRB’s flew off of the challenger in opposite directions. The SRB’s were detonated by the United States Air Force 110.25 into the launch. Which was 36.6 second after the Challenger exploded.

What caused this Tragedy?

According to NASA this was the problem. “The right field joint sealing was the main suspect to the cause of the accident, because the smoke after ignition and fire during flight, came from the region of the right field joint. The Solid Rocket Booster’s are made up of four main parts. They are joined together by a Tang and Clevis joint. Each part has a Tang on the bottom and a Clevis at the top. The Clevis is shaped like a “U”, while the Tang is in the shape of a straight line. The Tang would fit by sliding down the sides of the “U” of the Clevis. The right Mid Segment connects to the Aft Segment with the Nozzle. The joint that connects these two segments together is called the Aft Field joint. This is the joint that failed on the Right Solid Rocket Booster. The joint is sealed by two rubber O-rings, with a diameter of 0.280 inches (+ 0.005, -0.003). The sealing is used to stop the gases from inside the SRB from escaping. The seal had failed, because the flame seen during the flight was gas being burnt. The gas that was being burnt was coming out the hole where the seal was supposed to be. The seal would have kept the gas from coming out. ”

There were a few causes that could have lead to joint seal failure. These causes were;

“Assembly damage/ Contamination; The joint seal could have been damaged or contaminated during assembly of the SRB. ”

“Gap opening; The gap between the joints open as the pressures are applied. ”

“O-ring compression; This depends on the width of the gap. ”

“Joint temperature; The temperature has effects on the sealing ability of the O-ring. ”

” Putty performance; Putty, Zinc chromate is applied before assembly inside the joint to stop gases going to the O-rings.”

“Assembly could have damaged the seal joint because they were transported horizontally. ”

The temperature was also a main factor in this accident. This was the coldest day that NASA had ever tried to launch a spacecraft into space. It also cause the failure in the joint seal. At low temperature’s the O-Rings do not seal correctly which is one reason the joint seal was not effective.

The picture on the left shows ice that was under the launch pad the day that the Challenger was launched. The right picture shows one of the control boxed which was not used because of the ice.

The conclusion is that the Challenger was just one of NASA’s many mishaps. There were so many problems that led to the destruction of the Challenger. The conditions were too bad for this mission. Human error and nature took place and cause a tragedy. The Challenger will be remember forever and will remain in the history books as one of the nation’s most devastating events.

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