Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/5/84; site ssc-vax.UUCP Path: utzoo!watmath!clyde!bonnie!akgua!whuxlm!whuxl!houxm!vax135!cornell!uw-beaver!ssc-vax!eder From: eder@ssc-vax.UUCP (Dani Eder) Newsgroups: net.columbia Subject: Re: Columbia's Tiled Damaged by Rain Message-ID: <130@ssc-vax.UUCP> Date: Sat, 17-Aug-85 01:32:29 EDT Article-I.D.: ssc-vax.130 Posted: Sat Aug 17 01:32:29 1985 Date-Received: Tue, 20-Aug-85 06:14:36 EDT References: <4010@alice.UUCP> <199@mot.UUCP> <521@calmasd.UUCP> <47@darwin.UUCP> <1400@cbosgd.UUCP> <1095@cbdkc1.UUCP> Organization: Boeing Aerospace Co., Seattle, WA Lines: 40 > >Regular airliners manage to fly at several hundred miles per hour > >and fly through clouds and rainstorms without much trouble. They > >seem to have metal skins designed to not hit the air/water head on, > >but rather deflect it over them. Aerodynamics, right? > > > >I would think the same property would apply to the shuttle. > > I once saw a sample of the shuttle's tile skin. It looked like the kind of > brick you see inside a ceramic kiln. It looked very soft and absorbant. > While the shuttle *is* aerodynamic to some extent, it is still very close to > a flying rock. It does not have the very sharp features that an airliner > possesses. Back when the design of the Shuttle was being decided, NASA decided that developing the Space Shuttle Main Engines was enough of a technical challenge. If there were another difficult piece of technology, the risk of the program failing because the technology was not working would have been too high. At that time there were two candidate thermal protection systems: metallic and ceramic. The metallic technology was not in hand, the ceramic was. The ceramic was therefore chosen. Another area where the technology did not exist at that time (early 1970's) was structure that could stand high temperatures. The basic structure of the Shuttle is aluminum, just like most commerical airplanes. Aluminum, while light, cannot stand high temperatures. The thermal protection had to keep the structure cool, but it couldn't weigh too much. The solution worked out was to tailor the thermal protection to the temperatures it was exposed to, using the lightest materials available. Unfortunately, these materials, which are cermics, are brittle, and hence chip easily and fracture in a way metals do not. Yes, the Orbiter is a kludge, but the best kludge that could be devised at the time. The next generation vehicle will have the benefit of 15 more years of technology development, and will therefore be better in many respects, but it too will be a compromise of available technologies needed to do the job. Dani Eder / Advanced Space Transportation / Boeing Co / ssc-vax!eder