December 6, 2011 Leave a comment
For this post, I want to discuss the reasons the government decided to retire the Space Shuttle programs. From the information I was able to gather, it seems that two large factors leading to the retirement of the Space Shuttles involved economic and technological disadvantages. The two historical failures of the Space Shuttles (the Challenger and the Columbia tragedies) did not help the help the case of keeping them around either.
28 Jan 1986, the Space Shuttle Challenger exploded 73 seconds after lift-off, resulting in the deaths of 7 crew members. The cause of this failure was the malfunction of an O-ring in the right solid rocket booster of the shuttle. This resulted in a breach in the solid rocket booster joint it sealed, which allowed pressurized hot gas from within the solid rocket motor to reach the outside and impinge upon the adjacent solid rocket booster attachment hardware and external fuel tank. This led to the separation of the right-hand solid rocket booster’s aft attachment. In summary, all this led to the structural failure of the external tank.
01 Feb 2003, the Space Shuttle Columbia disintegrated shortly before it was scheduled to complete its 28th mission, killing the seven astronauts who made up its crew. The failure of the Columbia was a result of damage sustained during launch. A piece of foam insulation the size of a small briefcase broke off from the Space Shuttle external tank under the aerodynamic forces of launch. The debris struck the leading edge of the left wing, damaging the Shuttle’s thermal protection system and leaving it vulnerable to the intense heat generated from atmospheric friction.
Though the initial goal for the Space Shuttle programs was to provide access to space as a routine and inexpensive activity, access to space remained (and still remains) a highly expensive and highly inflexible activity. The price to launch a payload aboard the Space Shuttle is still $10,000 per pound, a figure that has not gone down in over a decade. It is the versatility of the Space Shuttles and their ability to perform multiple roles that made them so expensive.
NASA has always regarded crew safety as its number 1 priority; however, a long-standing drawback to the Space Shuttles was the crew escape system. The requirements for the 2nd generation Reusable Launch Vehicle were a 1 in 1000 Loss of Vehicle and a 1 in 10000 Loss of Crew over the entire flight profile, which implied a 90 percent confidence in the Crew Escape system. Unfortunately, the technology of the Space Shuttles only generated a 75 to 80 percent confidence in the system according to the data of the Naval Aviation Center. The Crew Escape system only operated when the shuttle is in a controlled gliding flight after reentry and is unable to reach a runway. It was thought to be pointless to pursue further advancements in an aging technology when the cost of these begins approaching the cost of developing a replacement for the whole system.