alb@alice.UUCP (Adam L. Buchsbaum) (07/19/85)
The tiles of the shuttle Columbia were damaged when the ship fly through a 30-second rainstorm atop a Boeing 747 en route to KSC, NASA said today. Initial estimates said that a few hundred would have to be replaced, and a couple thousand would need new outer coating. The Columbia, temporarily housed in the VAB, will be moved to the OPF tomorrow.
fred@mot.UUCP (Fred Christiansen) (07/30/85)
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.
--
<< Generic disclaimer >>
Fred Christiansen ("Canajun, eh?") @ Motorola Microsystems, Tempe, AZ
UUCP: ihnp4!{attunix, btlunix, drivax, sftig, ut-sally!oakhill}!mot!fred
ARPA: oakhill!mot!fred@ut-sally.ARPA AT&T: 602-438-3472rfc@calmasd.UUCP (Robert Clayton) (08/05/85)
> 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. > -- > << Generic disclaimer >> > Fred Christiansen ("Canajun, eh?") @ Motorola Microsystems, Tempe, AZ > UUCP: ihnp4!{attunix, btlunix, drivax, sftig, ut-sally!oakhill}!mot!fred > ARPA: oakhill!mot!fred@ut-sally.ARPA AT&T: 602-438-3472 Do not underestimate the power of any massive particles in a high velocity fluid stream. Commercial sand blasters operate at 60 mph and are used to remove heavy corrosion from steel and to erode stone surfaces in buildings. Shotblasters operate at 100 mph and are used for shotpeening metal parts - a work hardening process used to strengthen steel castings and forgings. In the last century, hydraulic mining was used to wash away mountain slopes to expose pay dirt in California's gold country. These hydraulic cannons can be seen today along the roadside set up as historical monuments. They are the size of field artillery pieces. From the look of them, it is unlikely they would have operated above 50 mph. Extensive flumes and aquaducts were built to channel the water to them. Hydraulic mining is used today to mine iron ores. 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. Today, commercially available cutting tools use high pressure water jets to cut steel plates 6 inches thick. Water is not harmless. Bob Clayton GE Calma, San Diego R&D (619) 458-3400
ian@darwin.UUCP (08/09/85)
>> 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. So making sure they have _clear_ weather to land in is not just for the photographers, eh? :=)
mark@cbosgd.UUCP (Mark Horton) (08/14/85)
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.
jeq@laidbak.UUCP (Jonathan E. Quist) (08/15/85)
In article <1400@cbosgd.UUCP> mark@cbosgd.UUCP (Mark Horton) writes: >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? From a description of Voyager, the aircraft designed and built for the sole purpose of flying around the world, non-stop, non-refueled: "(The airfoils) both had to somehow avoid the deleterious effects of bugs, rain, and even ice for 10 days and through 25,000 miles of the earth's far from pristine atmosphere. ... What John (Roncz) came up with was an airfoil shape that controls *where* the inevitable bugs will hit the wing surface..." (from "John Roncz, the Arisotle of Airfoils", _Sport Aviation_, July, 1985) This effect, though not always designed in, is valid nonetheless. (Currently, the around the world flight attempt is expected to occur sometime in the autumn of 1986.) Jonathan E. Quist Lachman Associates, Inc. ihnp4!laidbak!jeq ``I deny this is a disclaimer.''
gwe@cbdkc1.UUCP ( George Erhart ) (08/15/85)
In article <1400@cbosgd.UUCP> mark@cbosgd.UUCP (Mark Horton) writes: >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. 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.
rfc@calmasd.UUCP (Robert Clayton) (08/16/85)
> 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.
eder@ssc-vax.UUCP (Dani Eder) (08/17/85)
> >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
tomm@asgb.UUCP (Tom Mackey) (08/19/85)
Previous postings referring to the tile rain damage note that the tiles are of a fragile nature. One author questioned just how fragile they are. I worked at Lockheed Missiles and Space Company (LMSC) from 1977 until 1979, during which time we produced the first ship set of >25000 tiles. Last night I came across a scrap tile that managed to "follow me home" towards the end of my stay at LMSC. The raw material feels like a very fine grained poly- urethane foam, with a glass ceramic coating only a few thousands of an inch thick. This coating is what produces the smooth aerodynamic surface and protects the interior from abrasion. It is interesting to note that eventhough the raw (meaning uncoated...the tiles have been "cooked" several times by the time they are ready for the final coating processes) tile material may be rubbed off like powder with the finger, they required diamond coated end mills to machine them. Yes... each of the tiles are individually machined. I understand the programming for the N/C (Numerically Controlled) machines has been greatly automated by now, but when we first started, MANY of the tiles were individual efforts. The most that could be expected was to run the program in mirror image so as to produce right and left hand tiles. Of course, even that was no help for the many tiles surrounding portals and sensors. There was a southern Calif. company that was experimenting with a differant technique to provide thermal protection. The tiles (on large areas of the ship) were produced to be installed in groups of approx. 24, called an AFA (Array Frame Assembly). This other company was looking at producing a bonded titanium/graphite(?) assembly that would replace about 4 of the AFA's at once. I don't know where that effort went. It sounded promissing at the time, since one of the most serious problems with the first several ship sets was too small a footprint. In other words, the aerodynamic forces would tend to fly the tiles off the bonding surface. A lot of redesign went into reshaping some of the tiles so the bonding footprint could be made larger. This posting, unfortunately, has turned into a random core dump, so forgive me if I got a little off the subject. I welcome comments and questions, and would be glad to further contribute within the guidelines of proprietary constraints. Tom (Gee, I miss aerospace!) Mackey ....bmcg!asgb!tomm
peterb@pbear.UUCP (08/20/85)
I think if the shuttle's exterior skin was made from titanium, then
it would weigh quite a bit, and would change its flight charecteristics from
"a set of car keys" to a brick. Sure in the second generation the added
weight can be designed into it, but still what are you going to do with all
the heat the the titanium stores?
I remember reading a while back about a writer's ride in the
blackbird, and as he was leaving he asked the pilot what the burning smell
was. The pilot pointed out that since the titanium heted up, they had to use
insulation on the inside of the aircraft to preserve avionics, hydralics,
and wiring and conrtol cables from the extreme heat. That is also why
blackbirds are painted black: so the black surface radiates heat faster than
any other color.
So if a second generation shuttle was made of titanium, you would
also have to design in expansion factors for titanium, and insulate
everything on the inside from the extreme heat. The tiles are a perfect
choice for heat insulation. You can hit a tile with a blowtorch until it
starts to turn orange, and then after removing the torch, 30 seconds later
you can handle it safely. Also (depending on the thickness) the heat would
not travel through the tile. This is because the tile is almost like pumice:
it has many little air pockets and is extremely light. But the cost of
insulation and lightness is in its being brittle and soft. Water particles
travelling at high speed can easily fracture the surface of the tile and
slowly cause it to wear down.
Peter Barada
{ihnp4!inmet|{harvard|cca}!ima}!pbear!peterbjer@peora.UUCP (J. Eric Roskos) (08/24/85)
> It is interesting to note that eventhough the raw (meaning uncoated...the > tiles have been "cooked" several times by the time they are ready for the > final coating processes) tile material may be rubbed off like powder with > the finger, they required diamond coated end mills to machine them. Yes... This sounds like ordinary ceramic glaze, is that the case? (I.e., ceramic glazes before you fire them are made up of finely powdered glass, mixed with a binder and suspended in water; they go on with a texture sort of like chalk, but then when fired the glass melts together into a solid surface.) I'm not entirely sure what is meant here; are the tiles like this: ================== <-powdery before, hard after firing oooooooooooooooooo oooooooooooooooooo <-polyurethane foam oooooooooooooooooo ****************** <-bonding site ref'd later in article or is it the polyurethane-foam-like material that rubs off before firing but is hard after? -- Shyy-Anzr: J. Eric Roskos UUCP: ..!{decvax,ucbvax,ihnp4}!vax135!petsd!peora!jer US Mail: MS 795; Perkin-Elmer SDC; 2486 Sand Lake Road, Orlando, FL 32809-7642 "Zbba Cvr!"
mikel@bmcg.UUCP (Mike Lesher) (08/26/85)
In article <900002@pbear.UUCP> peterb@pbear.UUCP writes: >... > I remember reading a while back about a writer's ride in the >blackbird, and as he was leaving he asked the pilot what the burning smell >was. The pilot pointed out that since the titanium heeted up, they had to use >insulation on the inside of the aircraft to preserve avionics, hydralics, >and wiring and control cables from the extreme heat. That is also why >blackbirds are painted black: so the black surface radiates heat faster than >any other color. >... >Peter Barada >{ihnp4!inmet|{harvard|cca}!ima}!pbear!peterb I saw a TV program that detailed the making of the SR-71 (blackbird). It was first painted standard white with normal jet paint. After its first high speed flight it returned black. They then went and tried to develop a high temp paint that would not burn off. I seem to remember that they spend bunches of money, at our expense, with no sucessful attempts. They then said, "Gee, it looks need black." After all, the avg. hull temp. is 1300 degrees F. Mike Lesher (bmcg!mikel), Burroughs Distributed System Group, San Diego, CA.
tomm@asgb.UUCP (Tom Mackey) (08/27/85)
I really did not intend that this discussion go on, but a followup to one of
my previous postings on the shuttle tiles might imply to the casual reader that
the tiles are made of polyurethane foam. This IS NOT THE CASE. Briefly, and
with more than a few omissions, the process of making a single tile goes
something like this (remember this was 7 or so years ago, so the process may
have changed somewhat since then):
A saturated (probably super-saturated) mixture containing silica crystals,
binder, and some other stuff is prepared and the silica crystals begin to
form long "strings". The slurry goes through a sintering process which
compacts the material, removes the excess moisture, and leaves the tile
material with inter-woven strands of glass.
The block of material undergoes several cooking processes in micro-wave ovens
which removes all moisture (well, most of it, anyway). The block is then ruff
sawed into tile-sized pieces. I believe the blocks are X-Rayed somewhere in
here to weed out internally flawed tiles.
At this point, the material is snow white, and feels chalky to the touch. It
is dense, with no visible air pockets. If rubbed lightly with the finger, a
powdery residue (which is pure glass) is transfered to the finger. The
N/C programmers used to use scrapped tiles as pencil holders, so you can imagine
how soft it is. A pencil will push right in, as will a finger nail. If
examined under high magnification, the material looks for all the world like
a gigantic snarl of lots and lots of pieces of fishing line. The strands of
glass are completely interwoven, forming a dense, yet open and airy structure
that traps the air. What you are rubbing off is the ends of millions of glass
strands.
Using various holding techniques, the tiles are machined. Usually the IML
(Inner Mold Line - fits the outer aluminum skin of the ship) and sides are
machined first. The tile is then placed with its neighbors in a AFA (Array
Frame Assembly), sucked down with a vacuum, and the OML (Outer Mold Line -
the aerodynamic surface) is machined. This works for large numbers of
relatively flat tiles. For the more complex tiles, as in the "candy cane"
tiles that cover the leading edge of the vertical stabilizer, individual
nesting fixtures are machined out of flawed tile material, the OML is machined
first, and sucked against the nesting fixture for IML and side machining.
Since all the data is available, the OML machining motions can be rotated
and translated, making the nesting fixture cheap and easy to build. They
are usally thrown away after one use.
After inspection, the tiles are coated with the outer glaze and fired. I
did not get to see this process, so I do not know what they looked like at
this point. After firing, and there are several glaze/firing steps, the
IML and half of the sides are white, being coated with a clear glaze, and
the OML and the other half of the sides is either black or white, being
coated with either a black or an opaque white glaze. A narrow strip is left
uncoated, so as to prevent the tiles from exploding in the vacuum of space.
I hope this clears up some misconceptions for some, provides some interesting
information, and didn't put anyone to sleep. It sure is embarrasing for
your boss to walk by and find you with your nose jammed into the keyboard!
Tom Mackey ihnp4!sabre!\
hplabs!sdcrdcf!-bmcg!asgb!tomm
{ ihnp4, ucbvax, allegra }!sdcsvax!/
Burroughs Distributed Systems Group Boulder, Coloradopamp@bcsaic.UUCP (pam pincha) (08/28/85)
In article <1521@peora.UUCP> jer@peora.UUCP (J. Eric Roskos) writes: > >This sounds like ordinary ceramic glaze, is that the case? (I.e., ceramic >glazes before you fire them are made up of finely powdered glass, mixed with >a binder and suspended in water; they go on with a texture sort of like >chalk, but then when fired the glass melts together into a solid surface.) >I'm not entirely sure what is meant here; are the tiles like this: > > ================== <-powdery before, hard after firing > oooooooooooooooooo oooooooooooooooooo <-silicon "foam" (Froth might be a better oooooooooooooooooo term) > oooooooooooooooooo > ****************** <-bonding site ref'd later in article > >or is it the polyurethane-foam-like material that rubs off before firing but >is hard after? From what I know of the stuff, basically that it is a silicon "froth", it is highly likely that you are getting a minor amount of melting during re-entry. The stuff is so insulating that only the outer most layer is affected. It just can't take concentrated point pressures or excessive vibrations -- hence the rain damage (rain drops at high speed lots of concentrated force on a small area -- very condusive to compaction.). ------------------------------------------------------------ P.M.Pincha-Wagener (bcsaic!pamp) (usual disclaimer) ------------------------------------------------------------ >-- >Shyy-Anzr: J. Eric Roskos >UUCP: ..!{decvax,ucbvax,ihnp4}!vax135!petsd!peora!jer >US Mail: MS 795; Perkin-Elmer SDC; > 2486 Sand Lake Road, Orlando, FL 32809-7642 > > "Zbba Cvr!"