I found this story in the New York Times to be very interesting. I won’t post it in its entirety but will include a couple of excerpts.
“Until just a few years ago, some of the computers used in testing the shuttle’s boosters still contained Intel 8086 microprocessors, which are from the family that powered the first I.B.M. personal computers in the early 1980’s. That microprocessor has 29,000 transistors and operates at a speed of 10 million cycles per second. Today’s microprocessors tend to have 55 million transistors and run at a speed of 3.4 billion cycles per second.
The sensor system is far from the only shuttle component with potential problems.
Age-related complaints abound. Workers have sweated over the shuttle’s main engines, which endure some of the most pronounced stress of any component. Documents for the Discovery’s flight readiness review in June showed that engineers had found and dealt with tiny cracks along seals in the main engines and ruptures in some of the engines’ nozzle tubes.
In the solid rocket boosters, corroded bolts have been discovered in the motors’ nozzle joints. Elsewhere, a leak was discovered in a flexible hose used to deliver oxygen to the crew before the launching of the shuttle Endeavour in 2002; corrosion was later found in similar hoses.”
You wouldn’t think that the shuttle would be better equipped, but the article does show some reasons why they might be like this.
“And while the shuttle undergoes the kind of stresses that no conventional aircraft endures – the bone-rattling launching, the extreme cold of orbit and the fiery re-entry – Mr. Readdy, a former astronaut and pilot, said the high-stress periods were relatively brief for the shuttles, which might fly just dozens of times. By comparison, the average fighter jet undergoes far more wear and tear over its lifetime, he said.
NASA and others involved in the space program also note that older technologies, like the transistors hand-soldered onto circuit boards in the controller box for the fuel level sensors, may be more reliable than the delicate microprocessors found on newer craft.
“Sometimes high-tech doesn’t go with robust,” said Jeffrey Carr, a spokesman for United Space Alliance, the main contractor for the space shuttle.”
Ok, I lied, you have received most of the article, but it is just so interesting to me.
“The space agency has regularly upgraded aspects of the shuttles as well, as when it replaced the instrument panels and dials in the cockpits with modern flat-panel displays. Still, examples of the problems of an aging shuttle come up frequently. Just last week, the agency’s inspector general issued a report describing continuing problems with a kind of wiring used throughout the shuttles as a “safety risk.”
The document, which was first reported on nasawatch.com., said the wires were coated with an insulator known as Kapton that tended to break down over time, causing short circuits and, potentially, fires.
In a 1999 flight of the Columbia, a short circuit occurred five seconds after liftoff and caused two of the six computers that control the shuttle’s main engines to shut down.
NASA grounded the shuttle fleet for five months, and inspected and repaired some 1,300 problems it found with Kapton wiring on the Columbia alone. Many areas of wire that were inaccessible were not checked, and the accident investigation board recommended that the agency “develop a state-of-the-art means to inspect all orbiter wiring, including that which is inaccessible.”
But the agency has quietly dropped plans to comply fully with the recommendation to develop new nondestructive testing technologies, largely because of the Bush administration’s decision to retire the shuttle fleet by 2010.
The report assumed that the shuttles would be flying until 2020, as NASA had previously stated. The agency said the new system could not be ready before 2009 and would cost too much.
The inspector general’s report said that because no good alternative to Kapton had been found, any next-generation vehicle might also use it, and so the testing method would not be wasted. The report concluded that NASA was not following its own rules for managing risks.
Mr. Readdy said that the new procedures for inspection and documentation of all work done on the vehicles has greatly reduced the risk from Kapton wiring, and that even inaccessible wiring could be tested indirectly by monitoring either end of the inaccessible areas.
Dr. Griffin has compared the shuttle to a clipper ship, which he referred to as an amazing technological achievement now past its time. Of the shuttle, he said in a news conference this month, “I am in awe of the brilliant engineering that has gone into developing it maintaining it and sustaining it.” But, he added, “It’s time to move on.”