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Main engine exhaust, solid rocket booster plume and an expanding ball of gas from the external tank are visible seconds after the Space Shuttle Challenger accident on Jan. 28, 1986.
The explosion 73 seconds after liftoff claimed the lives of Challenger's crew of seven astronauts. The cause was determined to be an O-ring failure in the right Solid Rocket Booster; cold weather prior to launch was a contributing factor.

Presidential Commission Report can be found at:

http://www.ksc.nasa.gov/shuttle/missions/51-l/docs/rogers-commission/table-of-contents.html

The following case is based on an actual incident. However, individual actors and company names have been changed due to possible pending litigation. In addition, although conversations and memorandums used are based on evidence surrounding the case, they are hypothetical in nature, and are used to illustrate important issues rather than to attempt an actual reenactment of what "really" happened. In 1982, a television station video crew was filming the raising of their new television tower. The antenna was designed and manufactured by Antenna Engineering, Inc., a moderately-sized local firm. Riggers, Inc., a small local firm, was contracted to raise and assemble the antenna. During the initial design, Antenna Engineering submitted antenna plans to Riggers for their approval. Riggers approved the plans which provided for placement of the antenna hoisting lugs. These lugs provided attachment points for lifting cables which would be used for removing the antenna sections from the delivery truck, and for hoisting the antenna into the air for final assembly on a 1000 foot tower. A crew of riggers who had constructed such towers for many years was on-site. The crew used a vertically-climbing crane mounted on the already constructed portion of the tower to lift each new section of the tower, and finally, the two-section antenna onto the top of the tower. The design called for a three-legged tower, and as each new section was lifted, it was positioned and bolted onto the previous tower sections, one piece at a time. The tower legs were solid steel bars with 8 inch diameters. The tower sections weighed approximately 10,000 pounds and were each 40 feet long. They were raised without incident to a height of about 1000 feet. The two final antenna sections arrived at the site and assembly proceeded as planned, until the last antenna section was ready to be hoisted into position. This section was different from the other sections of the antenna because it had microwave baskets attached to the sides of the antenna. The placement of the hoisting lugs allowed the antenna to be lifted horizontally off of the delivery truck, but the baskets interfered with the lifting cables when the antenna was rotated to a vertical position. A make-shift extension to the lifting lug had to be fashioned by the riggers to permit the last section's vertical hoisting. Unfortunately, on the day of videotaping during the hoisting of this last section, something went wrong, and while the antenna was being hoisted, the bolts on the make-shift lifting lug extension failed. The result was a tragedy. Several riggers fell 1000 feet to their death.

On July 17, 1981, the Hyatt Regency Hotel in Kansas City, Missouri, held a videotaped tea-dance party in their atrium lobby. With many party-goers standing and dancing on the suspended walkways, connections supporting the ceiling rods that held up the second and fourth-floor walkways across the atrium failed, and both walkways collapsed onto the crowded first-floor atrium below. The fourth-floor walkway collapsed onto the second-floor walkway, while the offset third-floor walkway remained intact. As the United States' most devastating structural failure, in terms of loss of life and injuries, the Kansas City Hyatt Regency walkways collapse left 114 dead and in excess of 200 injured. In addition, millions of dollars in costs resulted from the collapse, and thousands of lives were adversely affected. The hotel had only been in operation for approximately one year at the time of the walkways collapse, and the ensuing investigation of the accident revealed some unsettling facts: