gottlieb@alliant.UUCP (Bob Gottlieb) (02/11/86)
The latest Aviation Week and Space Technology (10/2/86) has a particularly interesting number of articles on the shuttle. One of them, "Ruptured Solid Rocket Motor Caused Challenger Accident", describes what they believe/understand/speculate to have happened. I will paraphrase it: A plume of fire about 4x8 feet was detected (by camera) was detected coming out of the joint between the attach joint of the two aft segments of the right SRB. This continued to grow for 15 sec to a plume about 40 feet long. About 2 seconds before the explosion, the right SRB was providing about 100,000 lb less thrust that the left SRB. The flight control system was attempting to compensate for this by swiveling the nozzles of the SRB and main engines (and was starting to work). The leak of fire was acting like a blowtorch against the booster's lower attach points with the main tank, and shortly before the explosion, the lower joint apparently gave, either as a result of the heat, the torque of the thrust of the leak, or both. When the joint gave, the LOX line feeding the main engines was severed (causing the main engines to quit). The right SRB then pivoted around the upper join point, smashing into and rupturing the LH section, destroying Challenger. The AW&ST issue also discussed the possibility of abort at that time. Many NASA people were allegedly critical of NASA acting head William Graham for suggesting "that a potentially viable crew survival abort mode was available for solid rocket motor malfunctions like those that destroyed challenger". It goes on to say that there was basically no way to abort and survive what happened; if there was a problem during SRB burn, the astronauts have had it. An aside on the discussion about ejection seats, et al: I don't think that ejection seats are a viable abort mechanism; however, the type of system used on the F-111, where the entire crew compartment is ejected, might be a viable way to get the crew the h*** out of there if an emergency occurred. Granted, this is 20-20 hinesight, but it might help with future shuttles. It is expensive to implement. To continue with the AW&ST issue: There is a picture of the joint similar to where the leak is believed to have occurred. "The joint has two O-ring seals and is packed with an asbestos-filled zinc chromate putty to prevent gas leakage." Another article does a good job of describing the SRBs, although the title, "Solid Rocket Motor Designed With Conservative Margins", reminds me of the highly positive article on the DIVAD (also known as Sgt. York) air defense gun, shortly before it bacame apparent how faulty the weapon really was (bitch, bitch, bitch :-). With regard to future launches, there is concern that the joint on the SRB many have to be redesigned. This would take at least a year. The issue also names the members of the Presidental Commission. They are: o William Rogers - Sec'y of State, Nixon Administration o Neil Armstrong - former astronaut o David Acheson - Former Sr VP & general counsel to Communications Satellite Corp. o Eugene Covert - Prof Aeronautics @ MIT, consultant to NASA & USAF o Richard Feynman - Prof Theo. Physics @ CIT, Nobel Prize in Physics 1965 o Robert Hotz - advisor to disarmament; former editor to AW&ST o Maj. Gen. Donald Kutyna, USAF - director of Space Systems & CCC, former manager of DOD shuttle program o Sally Ride - astronaut o Robert Rummel - former VP for TWA o Joseph Sutter - Exec VP for Boeing o Arthur Walker, Jr - Prof Appld Physics, Stanford U. o Albert Wheelon - Sr VP for Hughes o Brig. Gen. "Chuck" Yeager, USAF, ret. -- -- Bob Gottlieb UUCP: ...!linus!alliant!gottlieb Mail: Alliant Computer Systems Corp, 42 Nagog Park, Acton, MA 01720 Phone: (617) 263-9110 Foot: "You can't get there from here". --------------------------------------------------------------------------- "I don't know what I'm doing, and Alliant isn't responsible either, so there!"