Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84; site calmasd.UUCP Path: utzoo!linus!decvax!tektronix!hplabs!sdcrdcf!sdcsvax!sdcc3!sdcc6!calmasd!rfc From: rfc@calmasd.UUCP (Robert Clayton) Newsgroups: net.columbia Subject: Re: Columbia's Tiled Damaged by Rain Message-ID: <542@calmasd.UUCP> Date: Thu, 15-Aug-85 17:28:15 EDT Article-I.D.: calmasd.542 Posted: Thu Aug 15 17:28:15 1985 Date-Received: Mon, 19-Aug-85 23:07:15 EDT References: <4010@alice.UUCP> <199@mot.UUCP> <521@calmasd.UUCP> <47@darwin.UUCP> <1400@cbosgd.UUCP> Organization: Calma Company, San Diego, CA Lines: 57 > In article <47@darwin.UUCP> ian@darwin.UUCP writes: > >>> how interesting! Columbia's tiles survive atmosphere re-entry only to get > >>> beat up by a rainstorm (which you'd think would be gentle) coming at it at > >>> a couple hundred mph. > > > >>A several hundred mph blast of water is extremely destructive. > >>Fortunately in a storm the water is dispersed, but I suspect it compares > >>to a sand blaster in terms of destructive potential. > > 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. The original posting was in regard to the tiles. Metal routinely endures sandblasting - it is a common method of preparing metal for priming and painting. I haven't held these tiles, but pictures I've seen give me the impression they could not endure extended exposure to a sand blast effect. The tiles, as I understand it were chosen for their lightweight insulation characteristic. Strength and wear resistance were limitations the designers were forced to accept. They allowed for this by making them replacable. Getting this discussion back to shuttle-related matters, The reason the tiles were chosen was that designers were trying to make a structure cheaper than Titanium. In the early '70s, welded all-Titanium structures were reserved for exotic craft such as the SR-71 Blackbird. The shuttle's goal was to find low cost structures that would lend themselves to production line fabrication. For the few shuttles made, a Titanium craft probably would have been cheaper, but that is not the point. The project was intended to research designs that could eventually lead to assembly line production of shuttle craft. I would be interested in knowing if this structure is indeed less expensive. Ignoring the intial year or so when tiles were dropping like flies but studying the later years when the shuttle operations arrived at steady state, have the operating costs imposed by these tiles been low enough to compete with Titanium structures? Recognise as well that Titanium structures are probably less expensive now due to improved fabrication techniques. Since the early '70s, there have been improvements in welding, adhesive bonding and Numerical Control Machining. In addition, there have been great reductions in the cost of Finite Element analysis and CAD/CAM. This greatly reduces the prototype stage of design and its high costs. This would significantly reduce costs in the low volume production of shuttles. I suspect that a second generation shuttle, designed for a production run of perhaps as many as 25 craft, might re-evaluate the problem and choose a Titanium structure that would not require (so much) insulation. Bob Clayton GE Calma San Diego, Ca.