The Construction of Space Shuttle Launch Complex 39-B

A very personal and technical written and photographic history, by James MacLaren.

Page 56: PCR Main Doors, Complete System.

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A day in the life.

Payload Changeout Room Main Doors, with Door Hoists installation underway.

And the Hoists are well worthy of the time and effort required to understand them, in and of themselves, as well as being marvelously illustrative of the way iterations manifest themselves in the real world, and (differently) on the drawings that purport to depict that real world, so we're going to spend good time and effort on the Hoists only, before moving on to the story of the Doors themselves, ok?

That might be Steve Skinner coming down off of the scaffoldboards onto the uppermost Torque Tubes Access Platform on PCR Main Door Panel 2L, but then again, maybe not. No way to tell with certainty.

Our other ironworker, mostly obscured by the Door Hoist that's being installed, must remain unnamed, alas.

Business as usual for Union Ironworkers at the Pad, hanging off the side of the cliff face very near the top of a pair of gigantic bi-fold doors that are 62 feet tall, directly straight up above the far edge of the RSS Main Floor steel framing and deckplates in the Orbiter Mold Line area at 135'-7", external to the main cavity of the PCR, which itself is 82 feet above the Pad Deck, which of course is an additional 50 feet above the bottom of the Flame Trench and the surrounding wilderness of the Merritt Island National Wildlife Refuge.

The photograph does not so much as hint at it, but this is a truly fearful place.

The story with these Door Hoists is more than just a little bit murky, and I retain very little by way of my own personal memories as to the fine details of what, when, how, and the rest of it, so we're going to be doing a little research here, as we go along with the story of the hoists, before continuing with the Doors themselves.

Things that went up without problems, things that fell under the heading of "low profile" in my own, at that time, view of things, just sort of get subsumed into the background fog of memories that may or may not even have existed in the first place.

I was up there this day and I took this photograph with my own camera, of that there can be no doubt, but what I might have been doing, I cannot recall in the slightest.

We're looking down and across from a vantage point up on the Antenna Access Platform, which we learned about back on Page 30, over on the very farthest left side where the little flip-up platform over there meets the top of the Left Orbiter Side Seal Panel, but the precise angle of the photograph gives me to believe that I was crouched down some, to get as much of the Hoist that you see in our photograph, to show, from where it's partially-hidden up underneath the Ledge of the Antenna Access Platform.

The hoist itself constitutes one of those items in our drawing packages that has the power to mislead us greatly, via the inclusion of revisions into older packages, revisions which came significantly later, after the original package was already done and bought-off.

We're being told to install it as part of Contract Drawings Package 79K24048, which is what we were using when I worked for Ivey Steel, but somewhere along the line, after the fact, somebody inserted some contradictory stuff into 79K14110, which came before, and which was the Contract Drawings Package we were using when I worked for Sheffield Steel, years earlier, and if you stumble across that stuff unawares (and it's all dated, except that the dates you see, may or may not be your very best friends), it will leave you scratching your head, 'cause it makes no chronological sense at all.

The "later" stuff, on 79K24048 tells us to initially furnish and install this pair of very-complicated hoists at the top of the PCR Main Doors, all well and good, and here's S-279, which is the general arrangement drawing for all of this stuff, and which is the work you're seeing get done in the photograph at the top of this page.

These hoists had the ability to be manually pivoted from side to side on a vertical shaft, as well as extend in and out by means of a hinged boom segment which was operated by a pretty hefty screw jack, toward and away from the face of the PCR Door, which gave them excellent mobility and freedom of motion for working the Torque Tubes that held the Orbiter's Payload Bay Doors rigidly in place while they were open, to keep them from destroying themselves by bending out of shape under the influence of gravity down here on the earth's surface. The hoists were exceedingly complicated, and rather than get into it verbally, now that you've already seen the general arrangement drawing, I'm just going to let you see the series of drawings that depict the hoists in full, and let you marvel at all the complexity on your own, without comment.

So here you go:

The PCR Main Door Hoists, as detailed on drawing package 79K24048 sheets...

S-280

S-281

S-282

S-283

S-284

S-285

S-286

And yet, somehow, the earlier stuff, the 79K14110 stuff, finds a way to tell us to remove them!

And we've actually been taken to the drawing that tells us to do that already, back on Page 36 when we were working for Sheffield Steel, way before any of this 79K24048 stuff had ever been dreamed up in the first place, back when we were learning about "Torque Tubes," and here's one of at least two drawings that calls for the removal of these yet-to-be-installed hoists, highlighted to draw your attention directly to the nonsensical notation for the removal of the hoists on A-53, which is also referring us to detail 'G' on drawing A-53A, and when we go look at that, we get full confirmation of the "removal" along with a rendering of the hoist, which, curiouser and curiouser, not only does not quite look like the same hoist we started out with, by installing it in the first place, on 79K24048 S-279, but it also doesn't even manage to look like the hoist on A-53, one sheet previous, which referred us to it, and what the hell is going on here, anyway?

And hey, what the hell, it's not goofy enough already, right? Let's head on back to one of the drawings which got invoked back on Page 36, that introduced us to the Torque Tubes (which is what these little flip-ups that hang off the external side of the PCR Main Doors are all about in the first place), and play a little, "Can you spot the difference?" with that.

79K14110 A-48A.

And since I'm such a nice guy, I'll help you along with our little game of Spot the Difference, and ask you straight up, "Do you see ANY hoists on this drawing?"

Hmm?

So ok, so no hoists.

Instead, you get a set of "Torque Tube Manipulator Arms," and yes indeed, we've already been through all of that stuff before too, back on good old Page 36, where I never so much as hinted at the baffling trickiness yet to come with this stuff. You had enough on your plate at the time without me tossing even more deeply-confusing stuff on top of what was already there, so I just let it go.

But now, things have finally gotten completely out of hand, and the timeline on our drawings has become completely scrambled, and things keep changing in ways both large and small, and like it or not, we're going to have to dig in if we ever expect to make any kind of real sense out of any of this, so as that, in the future, we stand a fighting chance of understanding what, and when, we're seeing in photographs of the RSS which we might ever be encountering henceforth as we traverse the internet, coming upon them as we go.

Oh boy, more history!

And, just so you know, these platforms threw me for a pretty good loop, too, back when I was working for Sheffield Steel and we were building the RSS in the first place.

There are few better examples in all of the drawing packages available to me of just how bad it gets with revisions, and in particular, uncommented revisions that refuse to mention what got changed, how, why, when, anyofit.

In the beginning...

RS&H designed the towers of Pad A, and up to this point, I've kept you more or less in the dark, insofar as allowing you to gain the misinformed opinion that Pad A is covered by drawing package 79K04400, which certainly covers a LOT of Pad A, but there is also a LOT that it does not cover, and by now you should be familiar enough with just how tricky this stuff all is, traveling through this bewilderingly phantasmagoric landscape, to allow you to make proper sense of drawing 79K04400 sheet V-1A, and yes, that goddamned "A" is yet another manifestation of things tacked on after the fact.

And our confusion with the flip-up platforms and hoists on the exterior sides of the PCR Doors stems directly from the fact that, for reasons unknown, from the very beginning, that stuff was handled separately, complete with its own pair of separate and distinct 79K numbers, and NAS10- contract numbers, and you can see that here, on V-1A. Which means that the original Pad A 79K04400 drawings I have for this area do not in any way address this stuff at all.

And of course, if some additional kind soul, or souls, were to come along, and find a way to flip me ANY of the listed 79K drawing packages that you see included on V-1A, in similar manner as has already been done by other Anonymous Benefactors, well then, that would be nice, and then I'd get to incorporate them into this treatise, and in so doing, permit me to further add to my goal, which is the increase and diffusion of knowledge regarding this so-far badly neglected aspect to the History of the Space Shuttle, and that really would be kind of nice, wouldn't it?

The structural steel for the Doors was, unusually enough, called out on one of the architectural drawings, and you can see that here, on Pad A drawing 79K04400 sheet A-48, and the elevation view of the exterior side of the Doors was called out a couple of sheets prior, on A-46, and the most significant thing about both of these drawings is what's not there, which I've pointed out to you on A-46.

The existing, accessible, photographic record of these platforms and hoists is less than ideal, with some of the most interesting photographs appearing with differing dates, and even NASA's own archives leave serious questions as to exactly when any given image might have really been taken, so... kinda keep that in mind, ok?

One thing we do know for certain, is that Enterprise, which was used for flight drop-tests among other things, was sent to KSC, mated to an ET and dummy SRB's, and rolled to Pad A for a variety of fit and function checks on May 01, 1979, so anything showing Enterprise on the Pad must be from that date or later, and here's an image of Enterprise sitting on Pad A during a water deluge test of the MLP that NASA's present-day image archive insists is from February, 06, 1980, but I'm not so sure I actually believe that, and one of the reasons is the sky behind the Pad is a summertime sky (It's hot out there. Actually, it's hot as hell out there.) filled with summertime clouds, and yes, those clouds in Florida are that recognizable, and the angles of the shadowing on everything also looks they're coming from a midday sun in May, June, or July, so I'm going to presume the "Date Created: 1980-02-06" notation on the NASA Image and Video Library page for "NASA ID: ARC-1980-AC80-0107-14" to be bogus, and stick with the period of time between May 01, 1979 and July 23, 1979 given on the NASA History web page as being accurate for the purposes of our digging down into what was, and was was not, part of the towers at the time, using images of Pad A with Enterprise on it.

(Also, note the existence at this early stage of the game, of the Extensible Pipe Boom Nightmare we learned about on the previous page, as well as the lack of a GOX Arm near the top of the FSS, the OMS Pods Heated Purge Covers down low on the RSS, as well as other significant items, which perforce, came later, or were removed/altered/replaced later, no doubt as change orders of one kind or another.)

And now all of that has finally been properly established, we can see (not the very best image, but it's the very best we've got, and if you overzoom way the hell in on it, you can very definitely tell that the hoist is there), by the summer of 1979, the Flip-ups and the Hoist, had already been furnished and installed over on Pad A.

What that might be, extending as a dark line from the Personnel Door down at the bottom of the PCR Main Door, running up past the flip-ups and taking a right-angle bend over to the area of the Hoist, I cannot know, but I'm guessing it's something associated with all this, in its very first incarnation, which was subsequently removed/replaced/dunno, which I have no record of, no drawing for, and no idea what it really is or what it's really for. But it's definitely something, right? Ah well, so it must be.

Regardless, the existence of the hoist and flip-ups in our summertime 1979 photograph squares well enough with our original Pad A drawing 79K04400 A-46 of the Doors (no hoist, no flip-ups) with dates of March and April 1975 down in the title block, followed by our tacked-on version of Pad A drawing 79K04400 V-1A with dates of March (which was when I walked in through the door of the Sheffield Steel trailer at Pad B for the very first time, as their new answering machine) and June 1980 in the title block and contract completion dates of Sep 10, 1978 for the flip-ups, and June 09, 1979 for the hoists.

And then it gets interesting.

The hoists disappear.

Here's an image of Columbia's Flight Readiness Firing, with a hard date of February 20, 1981, and... no hoist. Zoom way in on the image, and you can clearly see that the Torque Tubes are there complete to the small detail that they're yellow, but how they managed to work them, I do not know. Maybe the hoists came down temporarily for some reason? Don't know. Look close, and you can see the mounting brackets for the vertical shaft that allows the hoist to pivot, but...

And I have no idea what's going on with this kind of thing above and beyond the fact that as they began using their RSS in an operational mode on Pad A, they learned things as they went along, and as with any other new and heretofore unproven system of this size and complexity, initial presumptions were found to be less than ideal at various points along the way, and using lessons learned operationally (which never quite manage to track along in full agreement with what is originally designed and presumed) alterations became necessary, and often enough, the initial alterations themselves were at some point found to be suboptimal, and were returned to and altered again, and you'd like to get it all squared away with the least possible expenditure of time and effort to do so, but it doesn't always work out that way in the real world, and sometimes, you find yourself having to come back to something more than you want to, because it continues to evidence characteristics, operationally, that turn out to be... not quite what you desired, and you find yourself iterating, and there's really nothing you can do about it, except do your very best, and then look hard and long at the results and be ready to see and adjust for the fact that you missed a little something in your latest iteration, and must therefore, iterate again, and for reasons I'll never know, our PCR Door Hoists turned out to be one of the things that required multiple iterations before it finally settled down and assumed its final form, operationally.

And of course, over on Pad B, we were recapitulating the iterative steps they found themselves having to address on Pad A, and attempts were made to incorporate only those iterations which things finally settled down into without wasting time and money by having to hit all those intermediate iterations which it turned out were necessary to get there, and...

...it gets hairy...

...and the timelines, the histories, of the iterations, become braided, and in the end you wind up with two different stories, on two different Pads, and for those of us standing outside, there will never be a way to successfully unbraid each and every thread.

So in the beginning, there's nothing, and then we furnish and install, and then somebody (maybe us, maybe not) removes, and then something else altogether shows up instead (maybe), and the process may or may not repeat, with or without branches coming in from elsewhere or heading out in other directions as things proceed.

We've seen the drawings with nothing, so here's a couple of drawings with something.

The corresponding sheet to Pad A drawing 79K04400 A-48 over at Pad B is 79K14110 A-55, and it's different.

But A-55 is weirdly different, and it calls out the additional steel for the fixed portion of our little flip-ups exclusively, along with the support steel inside the door panel that holds them up, and the flip-up part only gets shown in outline, with a note referring us to drawing 80K54235, which is a completely different number from the corresponding 79K drawing package number which was called out for these things over on Pad A which we saw on 79K04400 V-1A, and oh boy, here we go, down the rabbit hole again.

And of course, since we've gone spelunking down the rabbit hole yet again, we discover that the corresponding sheet to 79K04400 A-46 over at Pad B, which is 79K14110 A-53, shows us, sure enough, that the Hoists are now there, but only insofar as we're being told to remove them, and where the hell did they come from in the first place if 79K04400 and 79K14110 never told anybody to install the damn things to begin with, and oh yeah, we have to wait till 79K24048 gets released, along with the contract that contains it, and there they are, in all of their exquisite detail, and the timeline on this stuff has developed quite the doubled-back-on-itself kink, hasn't it?

And of course, being the Good Little Contractors that we are, we dutifully remove the goddamned things (and based on incontestable photographic evidence this clearly wouldn't be the first time a thing like that has happened, except that we didn't remove them, and the sonofabitches were still sitting right there on the doors when I departed the pad for the final time in the last week of 1985), and now what?

No idea what, that's what.

And all throughout this entire tangled tale of hoists and torque tubes and flip-ups, nobody's been asking what happens with the flip-ups when the hoists are missing, and the presumption is that the hoists are kind of double-duty, and get used to not only manipulate the Torque Tubes, but also raise and lower the flip-ups, but nowhere along the line, at any place, has a thing like that actually been spelled out, and now that you mention it...

...hmm.

So maybe we should just forget untangling this mess for the time being, and go have a look at the corresponding sheet to Pad B drawing 79K14110 A-53, which itself is the corresponding sheet to Pad A drawing 79K04400 A-46 (yep, that makes THREE of the goddamned things, all purportedly showing us the exact same thing), and we've already seen it before, 'cause it's what actually calls out the hoist for initial installation in the first place, but it is the corresponding sheet to 79K14110 A-53, so here you go, here's 79K24048 sheet S-279, and hey looky there, how about that? The hoists do raise and lower the flip-ups.

Except for when the flip-ups are farther down on the Door, and the hoists aren't used for them, and instead, each flip-up gets its own individual hand-operated lifting system.

So it's neither fish nor fowl, neither here nor there, and...

This is stupid.

But it's also deeply fascinating, and seeing this stuff shimmering into and out of existence, morphing from one form to another as it did so...

And before we lose all ability to keep track, bouncing erratically between Pad A and Pad B, with the years rolling by, stuttering and stumbling through things as we go, I need to let you know that over on Pad B, for all the combined Sheffield and Ivey years when I was working in the presence of the platforms right up until the initial installation of the hoists when I was working for Ivey, the platforms never changed. Never moved. Never nothing. Hell, I never even knew what they really were.

Beginning with Day One, whenever it was that Wilhoit first put these platforms on the PCR Doors (and for the small fixed portion of these platforms, I don't even know if they went up with the Doors or if they got added on later, after the Doors were already in place) I have zero recollection of that Day One, and then, from that time forward, my recollections of these platforms remain pretty thin.

At some Sheffield/Wilhoit point, I noticed they were there, and I recall wondering to myself at the time, and wondering again every so often going forward in time from there, "What the hell are those things?" But beyond that...

...nothing.

There was a weird little set of inaccessible platforms hanging off the exterior face of the PCR Doors that had a strangely-shaped curved flip-up part which had been locked in its raised position from the very beginning, and which was never lowered or otherwise worked on to any degree by any individual or group, and until we wound up installing the hoists and platform winching system ourselves, there the platforms sat, inscrutable and immutable, as I remained insensible, about the whole damn thing, and prior to the hoists and winch stuff going up, since the platforms never moved, any questions passing through my mind about how any of it might work, or what it might be for, remained fleeting, only half-considered, and would invariably get swept away in short order by whatever else it might have been that I was doing at the time, whenever those fleeting questions returned once again to briefly poke at me, but never hard enough to cause me to actually dig in and get to the bottom of things.

And even after the hoists went in, I still never learned what this whole platforms-and-hoists system was all about. What it was for. What it did.

And it was not until I decided to write these essays, using the help of my newfound Treasure Troves with the material I'm able to dredge up on the internet, that I ever so much as suspected what really goes on with the Orbiter's Payload Bay Doors, and the Torque Tubes that keep them from breaking when they're opened and closed out on the Pad, which of course dictates the furnishment and installation of a whole bunch of other stuff that you're going to need in order to work those Torque Tubes, thus explaining the ultimate sense of the whole deeply-mysterious and bizarrely-contrapted thing.

As for how they managed to work this stuff over on Pad A, as the hoists seemed to come and go, into and out of existence, as is clearly visible on our various photographs, I have no earthly idea, and in the end, the hoists disappeared for once and for all, on both pads, and were finally replaced on 79K14110 sheet A-48A (and yes, for those of you keeping score at home, this is the fourth version of things going all the way back to 79K04400 A-46 all of which are purportedly showing us the exact same thing) by a set of Torque Tube Manipulator Arms, via a whole slew of new 80K drawing packages that I don't have, and the flip-up platforms shimmered and shape-shifted one last time along with that, and at some point, counterweights were installed on them, at which point they became quite-easily hand-operated, lift and lower, thus precluding the need for any purpose-designed lifting gear, and about all I can say about any of it, is "What took them so long?"

And just to put another little twist into things, this is all stuff you've already seen. With your own eyes.

We passed this way back on Page 36, and if you click this link, and read down from where it takes you, clicking links as you go along, you'll see that it's all right there, in plain sight, complete with photographs of it.

But it's all too much.

It's all too overwhelming.

Nobody could ever be expected to be absorbing all of this stuff, at each step along the way.

Hell, even with me right here, holding you by the hand, taking it slow, pointing things out in very specific detail with words and images as I go along, it's still almost impossible to absorb.

And I know that, which is why, when I revisit someplace we've already been before, I try to be very careful to point out those things which I did not specifically point out before.

So here's that same photograph showing the PCR Main Doors from Page 36 that I just linked you back to, but this time I'm going to specifically point out those counterweights, and that way, you'll know.

Where it is.

What it is.

And how it works.

So now let's leave the hoists behind and go ahead and give the PCR Main Doors themselves the good close looking-at which they so richly deserve.

They've been showing up here and there all through my narrative, but they've never been the center of attention, and I do not have any photographs of them specifically, and we've already pretty well familiarized ourselves with the general sense of them just now, learning about the hoists and flip-ups on them with this page, so...

Why not?

So ok.

So here's the PCR Main Doors in plan view, shown on Pad B drawing 79K14110 sheet A-54, looking down on them from straight overhead, with all of the major components shown, highlighted, and labeled.

In this view, you can see that they were attached to the RSS Main Framing on the pair of big W36's on Column Lines 3.4 and 4.6 that held the whole RSS rigid in this area, and defined the opening of the PCR, as well as holding a lot of OTHER stuff rigidly in place, including the Canister Guide Rails and the Orbiter Side Seal Panels, neither of which are shown in this drawing.

We've met the Doors several times already, and on one occasion I was careful to advise you that, regards "left and right" with the whole RSS, the PCR Doors are problematic, because, for unknown reasons, they chose to break their "Everything is in reference to left and right on the Orbiter," rule, and the left PCR Main Door matches with the right wing on the Orbiter, and... sigh.

So ok, so we'll be mindful of that one, right?

Right.

The Doors constitute some fairly heavy iron, and we're already aware of that one too, but one of the heretofore-unspoken implications of how large and heavy they really are, dictates that they be suspended in place. The Doors do not "sit" on anything. They "hang." And they "hang" in a funny way, from a single point, on a single panel.

Ten hinges for "outer" Door Panel 1L or 1R, attached to each of the big Column Line 3.4 and 4.6 W36's, just ain't gonna cut it with something like this, and the "inner" door panel (Panel 2L or 2R), the largest of the two bi-fold panels that go together to make up one door, has a sort of "spine" to it, in the form of a W27x84, which is by far the heaviest piece of steel in the doors, and which, being a W27, is so big that it actually sticks out behind the rear (PCR Interior) side of the main surface of the Door on that side, and that thing is there to not only stiffen up the door panel, it's also there holding the whole door panel up, all by itself.

I've drawn your attention to the W27 sticking out behind the interior face of the Doors before, back when we were continuing to curse the LRU, on drawing 79K14110 M-57, but I only did so by way of showing you how tight the clearances were between that W27 and the LRU Strongbacks, and left the construction of the Doors strictly alone at the time, because I was already firehosing you with too goddamned much information on Page 37, and enough was enough, but right now, it's no longer enough, so... let's go.

This whole "suspension" business with the Door is a thing that can trip you up if you're not paying close enough attention to it, 'cause the Doors have Door Tracks recessed into the floor of the PCR, and a casual glance at that end of things might cause you to believe that whatever it is that runs back and forth down in that recessed Track, is what's holding up the door panel as it does so, but it's not. It's just a guide, and it's nothing more than that.

It is not load bearing.

The real work gets done overhead, up at the top of the door panel, so now that we've got a kind of an idea of what we're getting ourselves into, let's go get a look at all of that, ok?

And just because... just because doors are considered "architectural" items... they went ahead and lumped all their PCR Main Door stuff in with the rest of the 'A' drawings, just as if it's "architectural", but really, it's no such thing.

The PCR Main Doors are serious business, and constitute an integral part of the overall structure of the RSS, and they're big as hell, and they're heavy as hell, and goddamnit, they're structural, not architectural, and if you don't believe me, well then, let's go find what's holding them up, and by golly here we are right back into the depths of the 'S' drawings, dealing with structural steel.

The upper Door Tracks live just behind the curtain wall of the Antenna Access Platform, and are suspended from above, tying all the way back to the RSS Primary Framing, including our good friend the big W36 that everything in the whole world seems to be tied to at one point or another in some way.

And sure enough, to find where it all comes from in the beginning, we'll need to go back to 79K14110 sheet S-39, and start digging in.

Oh boy, here we go.

And with as much time as we've already spent on the Antenna Access Platform, I'm expecting S-39 to be an old familiar face to you by now, so I'm not going to get into it too deeply, above and beyond advising you that it has a few detail callouts telling us where to go to see how this thing is put together, and A and B in particular, taking us over to S-58, tell the tale.

And here we are on 79K14110 structural sheet S-58, and now it becomes pretty obvious that we're working real structural iron here with keeping the PCR Main Doors up in the air in the first place, and keeping them there rigidly in the second place.

And no, it's not the heaviest iron you'll ever find in this tower, but it's... heavy enough, and one of the tip-offs with this is that they're using W8x24's for their diagonal bracing. In general, when you see somebody not using double-angles for diagonal bracing, and instead going to the use of wide-flanges, you can be pretty sure that they do not want anything involved with it to be going anywhere.

"We put it there, and we intend for it to stay there, and it's not going anywhere, to any degree.

So ok. Heavy enough iron, and when I do some exceedingly quick and dirty weight calculations for just the steel framing alone, for the larger (inner) door panel, I come up with a weight of over 15,000 pounds, so...

Heavy enough, I guess.

Which means that the upper Door Track which is carrying the full weight of the doors has some work to do, which we can now expect to be reflected in its construction, which construction needs to be very rigid and stiff so as whatever's up there moving the door can be relied upon with confidence, to travel cleanly, smoothly, and properly every single time without fail...

So let's go give that a look, ok?

And when we go to 79K14110 A-61 to get a look at it...

Yeah...

That thing's pretty muscular...

Just a hair under 20 feet long and not quite 2 feet wide, and that's a W18x119 there in the center of things, backed up with a bunch more heavy stuff that's either full-penetration welded or very-solidly bolted to it, and you're not even allowed to use the Chain Tubes or the Track Plates in your calculations, but you can rest assured that those things too, are contributing to the overall stiffness and sturdiness, and whenever the nomenclature for stuff shifts away from words like "beam" over to words like "girder" and...

There's some pretty close-tolerance stuff going on in there, with regards to both surface finishes and overall "plumb, square, and true" characteristics for the whole assembly, and...

Pretty muscular work, and pretty tight work, all the way around.

So ok, so now we know what's holding it all up in the air, and holding it all in place up there, so what makes it go?

And what makes it go is the Carriage Assembly, and we get an excellent look at it on 79K14110 sheet A-60, but it's kind of lost in there among all the other stuff, and I'm going to kind of feed it to you by degrees, and in our first view, all we're really paying attention to is the Carriage Assembly itself (which you're viewing from the top, the front, and the side, along with its Bearings (which are properly referred to as "Cam Followers" on the drawing), sitting inside of the lower portion of the Track Girder which is holding the whole schmutz up and rigidly in place. The rest of it is all there, too, but it's a little overwhelming, so for this moment, leave well enough alone, so you can clearly visualize this thing, which is built like a little battle-tank without treads (the shape of strong has a funny way of returning again and again, in the most far-flung and unrelatedly-diverse places you could imagine), rolling back and forth along the length of that Track Girder, pulling the PCR Main Doors with it, as it rolls to and fro in there.

The bearings along the bottom side of the Carriage are what bears the weight of the Door pulling downward, and they have a nice strong smooth path to travel across in the form of the Track Plates, which we saw (along with a bunch of other stuff) on the previous drawing we looked at, 79K14110 sheet A-61.

But that's not enough, and those doors see a pretty substantial wind load (along with other side-loads) every once in a while (hurricane winds of 130 mph on just the inner door panel 2R or 2L all by itself only, can go above 35,000 pounds, and you'd better be ready for it, if Florida decides to throw it in your face one fine day), so there are additional cam follower bearings on the sides of the Carriage, which, when pushed one way or the other by any of the side-loads which might be encountered, have their own set of Track Plates, to keep things firmly where they belong at all times, in all places, in all situations.

So now that we've got the Carriage more or less properly understood, let's take a look at what connected it to the door it was pulling back and forth, open and closed.

And right back to A-60 we go for that, but this time I've highlighted it differently in order to draw your attention the the business at hand, but you are in no way relieved of duty as regards continuing to understand what we saw on our previous look at A-60 when it was the Carriage that was our center of attention.

And here on this version of 79K14110 A-60 we can see the Hanger Stud Assembly in orange, and the guts of it is a 3¾"Ø very high strength AISI 4340 steel pin that's 13⅛" inches long, having a special shoulder-screw embedded into its top end, and the shoulder-screw transfers the weight of the suspended Door down into a STRONG spherical thrust bearing ("Radial Static Load Limit 239,000 lbs, Thrust Static Load Limit 295,000 lbs, Ultimate Static = 1.5 x Static Load Limits") which we do not have the drawings for, but what they gave us on A-60 is plenty enough to visualize this thing, which is held up by the Carriage Assembly, which is held up by the Track Girder, which is held up by the structural steel of the RSS, which is held up by the RSS Truck Drives and Hinge Column, which are held up by the Concrete of the Launch Pad, that lives in the house that Jack built.

And this Hanger Stud is cunningly designed to allow it to move around right where it needs to move around as the Door rotates with respect to the Carriage Assembly as it gets opened and closed, while at the same time, remaining rock-solid everywhere else, including along the length of the AISI 4340 pin in areas where that pin cannot be permitted to bend, even as it remains free to rotate, and it's strong as all holy hell throughout all of this, and a whole host of mechanical and structural problems associated with a gigantic bi-fold door rotating and moving back and forth precisely, inside of a huge steel frame, get solved in a single stroke with this thing...

Yeah.

Pretty good stuff, right here, holding the PCR Main Doors up.

Well alright, how about the part that moves the carriage?

And for that, we'll back up to drawing A-58 and take a look at the mechanism which used an air motor (they don't like using electrical motors in places like this if they can avoid it, because there's always the chance that one or more of the volatiles they're forced to work with in this business might get loose and reach explosive vapor concentrations in the air, and electrical motors are constantly sparking inside, and sparks and explosive vapor concentrations do NOT get along very well, and... they use air motors instead) to spin a couple of sprockets that drove a side-by-side pair of chains which attached to the Carriage Assembly, that ran it back and forth inside of the Track Girder, taking the Door along with it, wherever it went.

This is all pretty straightforward stuff, and 79K14110 A-58 speaks for itself pretty well, now that you've come as far as you have with understanding the whole system, and I'm just going to highlight the notes associated with the main players in this system, but I'm also going to highlight a couple of notes about how tightly this thing was crammed in up there with barely enough room to fit, especially in the area beneath the big wide-flange that carried the PGHM Bridge Beam Rail over there where the Track Girder very nearly touches the insulated metal paneling which made up the walls of the PCR, and over on the other end of the Track Girder, where the back side of the Curtain Wall that made up the back side of the Antenna Access Platform was so close that they had to actually clip the corner off of the enclosure that held the Chain Return Sprockets and the Takeup Assembly they needed for fine adjustment of tension on the Chains.

To get an overview sense of just how close together it all is up there, let's go to A-56 and take a look at it in plan view.

And looking down on it from above with drawing 79K14110 A-56 (Pay a little extra attention to that drawing number, "A-56", ok? We're gonna be having some fun with it here, in just a bit.), we can now clearly see that the Payload Changeout Room Insulated Metal Paneling, the PCR Main Doors along with their Track Girders, and the Curtain Wall of the Antenna Access Platform along with its Monorail Transfer Doors, all fit together up here without any room to spare. This whole thing is tight.

And we can never forget that the whole point of this thing, the whole point of the Payload Changeout Room is to provide a Clean Room environment for servicing and emplacement of Payloads into the Space Shuttle's Cargo Bay.

The whole thing was driven by the requirement for clean clean clean. This is the place where the Hubble Space Telescope would one day be given its final pre-launch checkout and servicing, prior to being placed into the Cargo Bay of Discovery and taken into orbit, and when you're working with things like that, the place where you do the work needs to be clean.

And it's bigger than a hotel in there, and there's this gigantic pair of bi-fold doors to give us access coming in from the great outdoors in there, and despite the fact that we're dealing with an opening in the side of our hotel that's big enough to roll something the size of the Hecita Head Lighthouse, complete with the lighthouse keeper's home, right on through it with plenty of room to spare, that same opening comes with a requirement to be able to shut it closed and seal it tight enough to maintain hospital-operating-room levels of cleanliness, every time we close it back up again, and over the course of the Program, it got opened, and then closed back up again, a LOT.

So the PCR Doors required exceptionally good seals at every point around their perimeters, which of course, did not stay put, thus necessitating seals that could deal with this kind of thing.

For the vertical portions of the Doors, this seal requirement wasn't all that much different than what you might encounter on a "normal" door, in a "normal" place, writ large.

Back when we looked at Pad B drawing number 79K14110, sheet A-54, we were given a glimpse of things in overview, and all of the vertical surfaces were shown, complete with seals, but there wasn't enough detail to make sensible use of it, so let's start in on that, ok?

But of course, it can't be simple or straightforward, so before we dip our toe into this water, I'm going to advise you that, once again, sigh, we're going to be crossing paths with the same sort of revisions mess (and it stems from the same underlying reason, too) that we endured earlier, while plumbing the depths of the Torque Tube Access Flip-ups up at the top of this page, and we're going to see notes that will want to take us to drawings containing things that never once entered into anything that was done while I was out there working on the Pad (offered here without comment, just to let you see them, and maybe puzzle over things for yourselves, 'cause I'm not getting into it here) 79K14110 sheet A-48 which is pretty obvious, and the more subtly-altered 79K14110 sheet A-63, and rather than even mess with that crap at all, I'm going to just jump over to the Pad A drawings, 79K04400, for the unsullied versions of things, as they originally appeared before Lockheed and Rockwell got their grubby mitts on them, and changed them in infuriatingly-close-mouthed ways, rendering them nearly incomprehensible in so doing. But it turns out that not even that little workaround comes without risk, and we still need to mindful, lest we run afoul of the trickiness yet to come.

So we have to look at drawings for the vertical seals on the Doors, using the Pad A drawings, and get a load of what the drawing number is for this one!

So here's 79K04400 sheet A-56 (Same drawing number! Same old "A-56" drawing number that we just used, farther up on this page, detailing work that was done on Pad B! But it's a different drawing! And it's showing us completely different stuff! Yikes! So watch out there, ok? It'll turn into a hall of mirrors on you, if you let it.), and it shows us how the vertical seals are done, and up in the "elbow" area where the two panels (R and L) of the bi-fold Door come together when the Door is closed, and it's simplicity itself to just run a standard heavy neoprene jamb seal down the Door, which provides good closure with excellent sealing capability, and that's shown up at the top of the drawing.

Down at the bottom of 79K04400 A-56, where the Door is very sturdily-attached to the Primary Framing of the RSS, it's a bit more complicated, but they cleverly solved that one with the addition of a bent plate that avoids the trickiness of those big hinges by simply going around them, running the full height of the door on its exterior side, with an additional flat plate screwed on to it, which gave them the ability to adjust things with exquisite precision, where it fit up against another heavy neoprene seal which was firmly mounted on to the big W36 that carried the Door (among other things), rendering an air-tight seal as it did so.

Pretty cool, if you ask me.

But for the horizontal surfaces of the Doors, things get a little more complicated.

And we will need to go back to 79K14110 A-56, to see how that gets done up at the top of the Doors, which, we must always remember, come rotating around into their final location, lined up with whatever it is that's just above them, and this rotation causes things to act like a pair of scissors during final closure and initial opening, and that sort of thing can, and will, tear stuff to hell if it's not accounted for.

We're closing our Doors by bringing them up beneath the outline of the Antenna Access Platform, and along the full length of the Door, we find ourselves coming up underneath the Curtain Wall and the Monorail Transfer Doors.

Yep. The very same Monorail Transfer Doors that I've cursed so many times before.

Fortunately, for the purposes of creating a proper seal with the tops of the PCR Main Doors, the underside of the Monorail Transfer Doors can be treated exactly the same as the underside of the Antenna Access Platform Curtain Wall which abuts them on either side, and as the PCR Main Door comes scissoring in at things with a mostly-sidewise motion, it doesn't actually quite touch anything...

...until they want it to, after it has come to rest, locked in place, and is no longer a moving object.

And, fascinatingly enough, the Door doesn't even quite travel to a position all the way up underneath the steel that's hanging down above it which it needs to seal to, and instead, it remains offset, just a little bit. And it has to stay offset, or otherwise the Track Girder or the Carriage Assembly, or both of them are going to be smashing into something somewhere, and they can't go any higher to let the Door Face come into sealing contact with the back of the Curtain Wall, because if they do that, they're going to be getting into that great goddamned big PGHM Bridge Beam Rail Support we saw on A-58 (which they're labeling, less than helpfully, as the "Payload Manipulator Rail Beam") with an elevation of 199'-7⅝" given for the bottom of its bottom flange, and no, that's definitely not gonna work...

So to avoid all of that hair-pulling impossibility, they simply made use of another flat plate and heavy neoprene seal arrangement extending away from the body of the Door, which let's 'em leave the damn thing be, slightly offset from the back of the Antenna Access Platform, just underneath it.

But this time, things are a little different, and the heavy neoprene seal isn't attached to the Door, and it's attached to the steel framing above it instead, and it's also inflatable (which is why it's not attached to the Door, and this makes running the supply/bleed air lines to inflate/deflate it much less problematic because that way they don't have to follow anything around in there, as it moves, and of course once the Monorail Transfer Doors got welded shut, things became even simpler and more straightforward), and until they open the valve and inflate it, the seal fails to make contact with the top of the Door down there just below it, thus neatly and completely avoiding any concerns about scissoring or any other motion-induced wear.

Again, pretty cool if you ask me.

So here's 79K14110 A-56 again, marked up so as you can see for yourself, with what I just described, and about the only thing I should probably warn you about is that, for who-knows-why reasons, they chose to take section cuts 'E' and 'F' looking in opposite directions, and that can cause you to wonder what side of the Curtain Wall and Monorail Transfer Doors is it anyway, that the PCR Main Door really winds up on?

But A-56 is good, and it's correct, and it gives you a really clean view of a pretty tricky and complicated place, way up there in a very out-of-the-way and hard-to-reach location.

And we're finally done with the top of the Doors, with the exception of one last thing, and that thing would be the locking mechanism that holds them firmly shut, thus keeping the whole PCR buttoned up tight, when the exigencies of high winds demand such a thing, because when you push against the center-hinge of these bi-fold doors from the outside as high winds might be expected to do, that sidewise force works in a way that causes it to want to pull the doors open (and if you've got a pair of bi-fold doors somewhere in your house that you can play around with, you will be able to see how this works), and of course the higher the wind that might be blowing around outside, the less we'd ever want to allow a thing like that to happen, so to cover that potential problem, they put some pretty stout Windlocks on the Door, top and bottom, and since we're still up here at the top of the Door, it's now time to give the Upper Windlock a good look.

So here's all that on 79K14110 sheet A-59, and there's nothing particularly fancy or unusual about any of it. It's just a pneumatically-actuated cylinder with our sturdy Locking Pin on it, and it works with the Carriage Assembly all the way over there to the far end of its travel, Doors-closed, where it throws the Locking Pin downward where holes in the cap plate and web of the W18 of the Track Girder line up with a corresponding hole in the Carriage Assembly, and once that thing is thrown, none of this stuff is gonna be going anywhere, until they actuate the pneumatic cylinder in the other direction, pulling the pin out of the lined-up holes, thus allowing the Carriage Assembly to once-again travel freely along the length of the Track Girder. Again, nothing fancy, but it's very definitely strong.

Ok. That's the top of the Doors.

More than enough to keep idle hands busy for a long long time.

But what's going on as we descend towards the Main Floor of the Payload Changeout Room down at 135'-7"?

Hinges and latches, that's what.

The Door Panels have to be attached to each other (bi-fold doors, remember?), and also to the Main Structure of the RSS, with something that lets them swing, and there additionally has to be something to kind of keep them snugly pulled together along their full 62 foot vertical extent where they close together in the center of the opening for the PCR, above and beyond the Windlocks at the very top and bottom.

And for the most part, this stuff is pretty basic.

And we return once again to Pad A drawing 79K04400 sheet A-56, and now that we're not interested in the seals any longer, we can give the Hinges and Latches our attention instead, and none of it is in any way tricky or unusual, so I'm not gonna dig any deeper than this, except that you need to know, as shown on 79K04400 sheet A-46, the Latches were, as with so very much else on the Towers, manually-operated, and there was a big long steel Torque Tube (but not the ones for the Space Shuttle's Payload Bay Doors) running down the door from the top, all the way to the bottom, with a great big handle on it, located for easy-enough use, where a technician on the PCR Main Floor down there at 135'-7" could walk through the Personnel Door embedded within the Main Door down at its very bottom, yank on the big handle, and engage or disengage things, pulling the Latches to, or releasing them, as operational need dictated. Ho hum.

Except for those cold, windy, rainy days when there wasn't a Space Shuttle or Payload Canister mated to the RSS, leaving this area wide open to the elements, in which case, instead of "ho hum" it would have been "grumble grumble, curse curse."

And at long last we're down on the PCR Main Floor, down at elevation 135'-7", down at downtown, down at the most familiar and home-like area in the whole facility.

And we've been here before, repeatedly, and we're here once again, standing at the edge of the Orbiter Mold Line Steel, looking off into the distance through the Great Opening in the unmated RSS which faces south and east toward Pad A in the behazed distance, to the harsh loud cacophony of needle scalers, keening grinders and drills, intermittent rising and falling whoops tinged with turbine-whine of air-tools spinning up and then spinning back down, coughing and roaring diesel engines, level-toned hisses and occasional jet-engine roar of compressed air, shouted curse words punctuated once in a while with sharp whistles, classically-metallic bangs and clangs and clacks and clicks of steel, light, heavy, and all points in between, meeting other steel abruptly, along with the pops and multi-toned white noise from oxyacetylene torches, with the staticky hiss of arc-welders as near-inaudible background to it.

In certain ways, oddly enough, this sound is very like the sound of the ocean with a high surf beating against the shore. It's loud, and it has the power to drown out spoken words from nearby people and other sounds too, and yet, at the same time, you almost don't even hear it at all. It's just sort of there, and unless something comes along to snatch your attention back to it directly, it's not there. Hard to describe. Very hard to describe this sound.

Steel construction has a smell, too, and that smell hangs in the becalmed air inside of the Great Cavity you find yourself standing within, and it's a funny smell, distinct and immediately recognizable in places where it can accumulate in the air such as the one you're standing in, metallic, but in no way resembling what most people refer to as metallic when they're talking about taste.

And the words come back again, and make you smile again. "Make it fry like bacon," and the smell is very definitely a combination of overtones and undertones that tell of real heat being applied and employed and accommodated. And the smell of heat has a thousand and one faces. The heat of oxyacetylene as it renders steel into separable pieces, the heat of electrical arcs as they instantaneously render other steel into a surprisingly-runny liquid that freezes solid in another instant as the arc travels onward, tearing the flux on the rod to hell as it does so, occasionally cutting into and rendering to vapor any paint or galvanizing which might have chanced to be in the way as it goes, and just the smell of hot steel, which is certainly not any kind of strong, barely distinguishable in fact, and you have to be close enough to it, but it's there, and your nose sometimes makes you aware of it, but not well enough to keep you out of trouble, should you place something inappropriate upon it, or brush against it, before the temperature comes all the way back down to ambient, because visually it offers no clue of its still-contained heat. No clue that one whole edge of it was glowing red just a minute or two ago. The heats of grinding and thread-cutting are different yet, each olfactory tone with its own peculiarities associated with the particulars of what's being worked, and how, and they offer themselves up and become an integral part of the overall bouquet.

Machinery has a smell, and it too is in the air of the Great Cavity. Oils and heavier lubricants of differing persuasions contribute their share, along with things that you would never expect to smell at all, nevermind evidence themselves with a sensibly distinct smell. Things like gearboxes. Drill bits. Winches. Wire rope. Hardware and tools in general and the gangboxes you find them stored in. They don't always smell, and sometimes they never smell, but oftentimes they do, and when they do, they smell like the metals they are made of, and sometimes the paints and plastics they are coated and sheathed with; they have distinct and different smells, and although they are mostly subsumed into the overall sound of the summation of all the other instruments in this orchestra of molecules wafted to you on thinnest air, they nonetheless can, and do, appear, and contribute.

And of course the smells of the people. Sweat. Cigarette smoke. Boots. Denim. Sleeved welding leathers worn to fend off cascades of molten slag and also the possibility of minute missiles, steel whiskers, and occasional somewhat larger things with temporary attributes of speed and direction. Hard hats. Toolbelts and bolt bags stained and begrimed from years of hard use. Chewing tobacco in tins. Each with its own smell, vanishingly small, or almost enough to knock you down.

And the lingering and mingling smells that adhere to no end of other things, too.

And as the becalmed air slowly walks it all past you, and as you walk past it, the Orchestra of Scent plays, and the music rises and falls, and different instruments make their contribution and then fall silent, playing now loud, now softly, now not at all.

And you stand there with your back to it, gazing out across the fierce wilderness toward the distant ocean, feeling the cool darkness of the Cavity on your shoulders, and it takes on this uncanny homeyness that can never be sensibly communicated to anyone who hasn't felt if for themselves, and at some point you realize you've been staring out into space for far too long, doing nothing (except that it turns out that it wasn't nothing at all, and instead, in some deeply-mysterious way, a small part of your brain detached itself from the rest, silently took command, and then made damn good and sure the tape-recording it was making would stand the test of time, and be here for you, right now, all these long decades later, perfectly preserved, so that you might share it... with like-minded people), and now it's time to turn and return your attention to the Floor Tracks for the PCR Main Doors.

And here it is here, on 79K14110 sheet A-57, and there's not a lot to it, really. Channel-framing, a smidgen over 7 inches wide between the faces of the "Roller Plates" on either side, not a full foot deep, strong enough, but not unnecessarily so, nothing at all like the strength of the Track Girder which we've seen above the Door, with a set of cover plates to keep you from inadvertently stepping in the open trench and breaking an ankle or leg in so doing, and also allowing for uninterrupted travel across the PCR Floor of wheeled things, whatever they might be.

And since it wasn't load bearing, instead of a Carriage Assembly, you got a simpler (but not particularly simple) "Guide Unit" to keep the Door in line, restraining side-to-side motion as it traveled the length of the Floor Track and back again.

And you get to see that Guide Unit here on 79K04400 sheet A-55 (because, yes, once again, the 79K14110 drawings have been altered).

As with things up at the tops of the Doors, there was a Windlock, too, and our drawing that shows it to us is 79K04400 sheet A-57 (and yet again, the confusion of two completely different drawings, both having the same number, A-57, one for 04400 and one for 14110, and this is a snare that wants very much to catch you out, but you're not going to let it, because you have been warned).

And here on 79K04400 sheet A-57, you see the Lower Windlock, and it's a bit different from the upper one, and instead of a pneumatic cylinder, it employs a screw jack to actuate the Locking Pin, and that Locking Pin has no holes to line up with, and instead it simply comes up from below, behind the Guide Roller, and blocks it from backing out of the shimmed corner it has been trapped in, and the Door stays shut, locked in place.

And to finish this Tale of the Payload Changeout Room Main Doors off, another difference down here at the bottom of the Door is that the inflatable seal needs to be attached to the body of the Door instead of the surface it seals against, which is the PCR Main Floor of course, because if you had a seal attached directly to the PCR Floor in this area, whenever the Door was open, the seal would become exposed to foot and/or wheeled traffic, constituting a trip hazard as a low obstruction, and would eventually be degraded and destroyed by such physical contact as it would undoubtedly endure over time.

So it goes on the Door, instead, and you can see that here on 79K04400 sheet A-55, which you just looked at a minute ago, but this time I'm yellow highlighting the note calling for the Seal only, in the interests of decluttering things so as you can more-clearly pick them up visually.

The whole thing was run from a Control Station which was located way back in the far corner of the PCR, in what I consider a poor location owing to the fact that from way back there, behind the PCR Interior Fixed Platforms (and the PGHM, too), visibility was close to non-existent, but with systems of this size and nature, things were never done by lone individuals, and instead there'd be a whole crew on it, each with walkie-talkies, each watching their designated area of concern like hawks, and when a Door went into motion, it did so at a very slow pace, and everybody was on that shit, so I guess it all works out in the end.

Here's where you find the location of the PCR Main Doors Control Station, on 79K0440 sheet A-25.

And we head back to 79K14110 sheet A-53, yet again, and turn our attention to that wonderfully old-timey-looking floor-mounted steel-plate Control Station itself, just to kind of admire it for a little while as we take note of what's on it, and what it does, now that we have a proper understanding of the whole system this thing controls. Which understanding should be causing us to maybe scratch our heads a little, looking at the rendering of this thing on the drawing, because it doesn't really seem to be complete, and where's the controls for the Upper Windlocks, hmm? And the more you look at it, the more you find yourself not seeing things that we know for a fact should be showing up on this thing, and the less it seems to be any kind of complete, and I'm guessing that when they originally drew it, the Doors had not settled down into a final configuration, and they just went ahead and hand-waved this little rendering of the Control Station, knowing that it would get finished off at some point, and a fair amount of paper went back and forth between the mechanical contractor (not us) and NASA before this thing got properly and completely resolved. But really, I do not know, and that's all just a guess.

Which then takes us to the whole pneumatic system for the Doors.

Where we tie it all together on 79K04400 sheet A-58, for once and for all, complete with that whole pneumatic system that drove it, and which was supplied from the 125psi "Launch Sys Interface" shop air which had its own supply, down in the High Pressure Gas Area which lives in the big cutout on the Pad Slope over there on the east side of the Pad...

...and that's how that all works.

So ok. Now that we have come to understand the Doors themselves, physically, as material objects, how 'bout we give a little consideration to the jobS they had to do, keeping things clean clean clean.

And of course it's a total 'duh' moment when it comes to closing the Doors, and keeping the inside of the Payload Changeout Room spotlessly clean, but what about the outside?

And nobody ever even thinks about this, unless they think something along the lines of, "Outside? Whatta ya mean, outside? It's outside! How in hell can a thing like the PCR Main Doors keep a thing like the outside clean? Does it do the whole world? 'Cause that's what's outside, right? Getouttaheah with your stupid goddamned outside. Whatta ya think you are anyway, some kind of funny guy?"

No. And you're not thinking this one all the way through, either.

Unlike every other payload-processing facility that deals with flight hardware, the RSS actually does have to deal with outside, and it happens every time they mate the RSS to either the Canister or the Space Shuttle.

Every single time.

And we've already looked right at it, back when we used 79K04400 sheet A-25 to locate where the PCR Main Doors Control Station is located, but of course our attention was elsewhere, so we cannot expect to have properly seen any of what I'm about to get into. So we're going to go back to 79K04400 A-25 to see what I'm talking about, but before I start talking, I'm going to alter it, by trimming a lot of it off, rotating what's left, cutting and moving various elements in the leftover parts, and then putting labels on it, all to help you visualize where we're about to be going with this, ok?

Which results in a version of 79K04400 sheet A-25 that in no way resembles the original, but clearly shows how the relationships between things that get exposed to the outside environment for unpleasantly long periods of time, and things inside the clean-room environment, change from one to another when things go from demate, to mate.

And you might have to stop and think about it for a little bit, to persuade yourself this really is a serious problem.

The Space Shuttle, unlike every other launch vehicle, does not employ the use of a Payload Faring to protect payloads on ascent.

The Space Shuttle, is the payload faring, and that constitutes a tremendous change in the series of steps which must be gone through before a payload becomes ready for launch.

Whole different work flow. Completely separate deal altogether.

And I'm sure that various parties, at various steps along the design and fabricate pathway, absolutely hated it.

But in the end, they had to accept it, and that was that.

The RSS, with its exposed surfaces of the PCR Doors and Side Seal Panels, the 135'-7" floor steel in the area of the Orbiter Mold Line, and the framing steel all along the underside of the Antenna Access Platform, is a sitting duck for anything that comes along.

And the Orbiter doesn't do much better, either. During rollout to the pad, it's another sitting duck, and even before that, when it's inside the VAB, it's still a sitting duck, because the VAB is very definitely NOT a clean-room environment, and they leave those cyclopitcally-giant doors fully or partially open a lot of the time when there's an Orbiter in there being stacked.

For the Payload Canister, it's not quite as bad, but it's there too, and it must always be taken into consideration.

And you wonder to yourself, "Ok, how bad can it be, anyway? It's not like we're working in polluted air next to a steel mill or your disgusting great-uncle who refuses to quit smoking. Nobody's throwing stuff at it. Nobody's handling any of it with filthy unwashed hands (they occasionally do, actually, but let's pretend they don't). So how bad can it be, anyway?

And really, all of the things just mentioned are valid, and in their absence constitute no hazard to a clean-room environment.

Dust, on the other hand, common everyday dust, turns out to be something that can cause you trouble. Florida in no way resembles the dusty kinds of places you find by the thousands of square miles out West, but it's not entirely dust-free, either. And dust settles and dust accumulates, and dust needs to be paid pretty close attention to, or otherwise it might find its way into something it does not belong in.

But there's more.

Lots more, actually.

One of the things that nobody ever thinks of is Florida's biology.

Stuff like the Hubble Space Telescope cannot stand to be exposed to the tiniest stuff imaginable, lest it gum up the works and render your multi-billion dollar payload significantly degraded or even unusable in some way. Things like pollen! I can just see the oak trees looking at Hubble and growling menacingly, "Say, that's a pretty nice mirror facing straight up, inside of that thing you've got there, and it would be a shame if anything was to happen to it."

And Florida is extraordinarily well-endowed with pollen, at certain times of the year. So even the plants manage to get into the act.

Care to take a chance on your hundred-million dollar DoD payload getting mixed up with some of Florida's mold? I'm sure the higher-ups would have no problem with your decision to just ignore it, and keep right on stroking with that bespoke, one-off piece of hardware you're working with, right?

Something else that people will never ever consider, when thinking about launch structures, is wasps! I'll have you know, from years of personal experience in the matter, that wasps are madly in love with steel launch structures, and sometimes is seems like that higher you go on the structure, the more the wasps like it, and the more of them you will encounter on a very regular and reliable basis. The damn things are all over the place up on the towers, and you need to be ready for them.

Wasps like to make their nests up under overhanging stuff on structures, and... how 'bout the underside of the Antenna Access Platform, or maybe our little Torque Tubes Access Platforms that hang off the exterior of the Doors, or even the Hoists themselves, hmm? Maybe go back to our photograph up at the top of this page, that started all this, and look at it again, with an eye toward, "Hmm, I wonder if there might be any wasp nests up there inside of that thing somewhere?"

Rely on it.

And right now I'm going to jerk this narrative off course, and we're gonna talk about ironworkers again.

And you're an ironworker.

And you're walking high steel.

You're traversing a span.

And you're neither here nor there, midspan.

Which of course is the top flange of a beam somewhere, and it might be four inches wide.

It might be wider.

But it might be narrower, too.

It might be the top flange of some channel framing.

But whatever it is, it's very definitely high steel, and you are on it.

And a wasp flies into your face, buzzes around for a second or two, brushes you behind your left ear, lands, and starts crawling down at an angle toward your shirt collar.

And you're MIDspan.

On high steel.

What do you do?

And it has suddenly become life and death, and "normal" people NEVER allow themselves to think about things like this...

...because they're too terrifying.

Just a stupid fucking bug.

That now holds your life in its hands.

And what you do...


...is nothing.


So.

Are you up to it?

Can you handle it?

Is this something you can deal with?

Mid span?

Because if you can't...

Because if you can't take it...

And you find yourself reflexively twisting and jerking around in an effort to knock that wasp off of you or kill it outright...

...unthinkingly...

...mid span...

...well then...

...things might wind up going badly for you.

And I've mentioned before in this thing about how ironworkers have ice-water running through their veins...

But I will never ever in all my life be able to express even the tiniest fraction of the myriad ways a thing like that gets expressed...

In the real world.

And now I shall return the narrative back to where it was before I jerked it off course.

Back to the Payload Changeout Room, and the insides and the outsides of things.

And we're not talking about getting stung here either, ok?

This has nothing to do with getting stung by a wasp.

Paper Wasps, which are exceedingly common locally around KSC, go around and chew on dead wood and plant stems, and then go someplace else (inside your satellite maybe?), spit the ground-up half-digested wood onto their chosen location, and start building their nest with it.

So I don't know for sure, but I've kind of got a feeling that if they're in there doing something like that, inside your payload, they just might fuck it all up in there with that stuff.

But what do I know? I'm just some structural schmoe, not a payloads vespid entomologist.

Fucking wasps.

And just the mere presence of ground up bug guts between two mechanically-moving parts inside a payload isn't going to be improving things very much, either. Maybe do a little research on what we call "love bugs" down here in Florida. Imagine a payload full of them things! Or the eggs that some moth decided to lay. Or swarms of gnats and midges. Or those great big black evil horseflies that are all over the Merritt Island Wildlife Refuge. Or the smaller gray ones. Or deerflies. Or...

Spiders is another one. Goddamned spiders. And the damn spiders trail silk all over the goddamned place, and it gets into stuff along with the spiders, and it's sticky, and it's a giant pain in the ass.

And a million other kinds of bugs, doing a million other kinds of unpleasant things.

Florida in general is owned and operated by the fucked-up bugs, and the brutal swampland of the Merritt Island Wildlife Refuge in particular, is one of the best places in the world to encounter bugs, and they crawl, and they fly, and they lay eggs, and they build weird little bug construction projects everywhere.

And sci-fi-looking shiny sparkly pristine clean payloads tolerate none of this stuff, and we haven't even gotten started with fucked-up birds getting trapped inside the PCR (with my own eyes, have I seen birds disorientedly flying around inside the PCR), shedding feathers, or deciding to build a nest in some hidden and inaccessible location, and shitting all over everything while they're doing that.

And bats.

And lizards (and snakes too, sometimes).

And...

Pshit.

So ok.

So we're gonna have to do something about all this shit.

And it turns out, that there's really not that much they can really do about it...

Which kind of sucks, when you think about it...

But they do the best they can, anyway...

And what winds up happening is that they use some of the exceptionally-well-filtered air which the PCR is so very-amply endowed with, and they just BLOW everything (or as much as they can, anyway) out of that ever-so-troublesome space in there (you know, now that I think about it, I don't think this space even has a proper name, which is kinda weird), in between the exterior surfaces of the PCR Doors and adjacent hardware, and the exterior surfaces of the Orbiter's Payload Bay Doors (and just a bit of the fuselage, too) or the Canister.

So, in order to understand how that works, we're going to need a basic understanding of how air gets handled by the PCR, and this one turns out (yet again, sigh) to be quite the large and complicated subject, and it includes a few things that make the appearances of the RSS as distinctive as they are, so...

Oh boy, here we go again...

Down into the twists and turns of the HVAC System.

Here's the quick and dirty version of things on a marked-up copy of 79K04400 sheet M-102 to let you see the overall pathway for all the "general purpose" air in there, end-to-end.

ECS Air for the Payload Changeout Room gets sucked in to a long concrete tunnel starting out as ambient air from the Great Outdoors, initially entering the system at the Remote Air Intake Facility way over by the Perimeter Road, enters the concrete body of the Pad at ground level on its west side, and goes into the ECS Room where it gets conditioned in multiple ways and then shoved into Ducts, which go through the ECS Tunnel to the base of the ECS Tower behind the 9099 Building, where it heads up and across to the FSS, traverses the FSS (a lot of the preceding was covered back on Page 41) and heads into the Struts and on over to the RSS down low along its back side, where it splits and enters the pair of Return Air Plenums that take up a lot of space down beneath the PCR, then it gets sucked into the Fan Rooms where the Fans (big ones, 26,000 CFM each) force it into the pair of very distinctive-looking 40"Ø Ducts that run vertically up to the top of the RSS along its back side, and up there it goes through the back wall of the PCR into an extensive array of ducting in the space between the PCR Ceiling and the RSS Roof where it feeds into banks of big HEPA filters that open up on their underside into the PCR, and then the Air flows downward till it reaches the Return Air Grilles on either side of the PCR down at floor level, which then funnel it back into the Return Air Plenums, and the process repeats from there, recirculating existing air and adding to what escapes the PCR through various Dampers because of deliberately and constantly maintained Positive Pressure, with new air coming in from the ECS Duct that goes into the Plenums.

And all of this happens for what's inside of the closed PCR Main Doors, behind them, and is why our Clean Room is clean.

Keeping in mind, that's just the "General Purpose" Air. There's always "other" air, right? But we're not going to be getting into any of that right now. Not required. Would only serve to complicate things, and it wouldn't help our present understanding of things in the slightest. We're gonna leave the "payload" air strictly alone for now. We're gonna leave the "hypergol spill" air strictly alone for now. And all the other "other" air, too. Air is a pretty big deal in the Payload Changeout Room, in case you didn't know.

And our Washdown Air gets grabbed off from all of that, up above the PCR Ceiling, and that's where we now get to return to our story.

And now that we've seen (and understand) 79K04400 M-102, we can get a look at 79K14110 M-92, and read Note 6 over there on the side to see how they use Dampers MD 8 and 9, and MD 29 and 30, to blast that space in there with enough air (we hope) to flush out all the wasps and horseflies and god knows what else that might be lurking in there that our payload is violently and life-threateningly allergic to. And of course, while we're here admiring M-92, we can look over at the right hand side of it to see what they do with their Air, if somebody tips over a teacup full of Hydrazine in there somewhere. Big Hypergol Fun!

And now we go to get an actual look at things (as opposed to a bunch of pug-ugly schematics, which you thankfully never find yourself having to deal with in the world of Structural Steel), and we'll start up above the PCR Ceiling, where all this Air comes from.

And we discover to our horror that it's a huge mess up there!

But we've been doing this long enough by now to be able to make sense of it, and to strictly focus on what we're interested in until we understand it, before we start casting our eyes elsewhere around on the drawing, checking out all of the other neato stuff (never forget, 90 percent of being smart consists in knowing what not to think about) you get to find when you start looking around at all of it, and 79K14110 M-96 has really excellent plan and elevation views of what happens with our Washdown Air up above the PCR Ceiling.

And to really get a proper feel for it, in detail, the next sheet in the package, 79K14110 M-97 section 'A', shows how the hollowness of the Curtain Wall works advantageously as a Duct, and further lets us see, in detail, how that funny "offset" with the PCR Main Doors just beneath it, works to further advantage in allowing our Washdown Air to escape the confines of the PCR interior, and make it out there where it's needed, in that neither-here-nor-there space between the mated Orbiter or Canister, and the closed PCR Doors, and it even shows us the Inflatable Seal that runs along the top of the doors, making sure to keep the differing persuasions of Air separate and distinct throughout it all.

And of course, since knowledge is power, and the more you know, the more you can know, now that we've reached our present level of understanding regarding this insanely-tricky part of our Rotating Service Structure out at Space Shuttle Launch Complex 39-B, we get to see that the position of those Diffusers down there along the lower edge of the Curtain Wall places them in a near-ideal position, sitting right there, aimed directly at it, to more-effectively blow all the goddamned wasps and horseflies off of (or is it just going to rile them up and make them want to go bite somebody?) those Hoists which we see being installed in our photograph up at the top of this page (and now we know that those Diffusers are just out of view hidden behind the near margin of our Antenna Access Platform ledge), which of course is what kicked off this whole bizarre trek through the never-ending pathways we've been following, in the first place.

And our look at that end of things is found on 79K14110 A-30, and if A-30 looks more than just a little familiar, it should, because we beat our head against a wall using it (and other drawings), back on Page 31, where we found ourselves locked a fierce struggle against the Monorail Transfer Doors.

And just to let you really really see how those Diffusers are looking directly down on top of the Hoists, I'm going to crop, chop, rotate, and alter 79K14110 A-30, and 79K24048 S-279 (both of which are by now, from all you've been through with this page, plenty familiar enough to you), and do an overlay, showing how the Diffusers in the Curtain Wall sit in relationship to the PCR Main Doors with the Hoists shown on them.

And here's what our new Frankendrawing has to say about Air and Doors and Curtain Walls and Diffusers and Hoists and Platforms and how they all work together to (hopefully) rid this area of things that don't belong.

So they blast our not-this not-that space with Air from way up on top of everything, and it flows downhill (may as well let gravity do some of the work, too, right?) along with whatever it picks up in the process, and it exits through a pair of cutouts down at bottom end of the very tall, very narrow, oddball set of PCR Insulated Metal Panels with the funny angle to them, which live between the big W36 and the back of the Canister Guide Rail, just skimming barely behind the Side Seal Panels.

And you get to see the very general vicinity of all that on 79K14110 A-17 (although if your very life depended on it, you'd still never be able to pick those "Insulated Metal Panels with the funny angle to them" out of all the rest) which shows us the whole RSS, face-on, from elevation 100'-0" to 242'-0".

And maybe while you're here looking at A-17, stop and consider just how far you've come since the first time you encountered this drawing, all the way back on Page 5, down near the bottom, when MacLaren was still bewilderedly walking around the place with no earthly idea as to where he was, or what he was seeing or dealing with...

...and you, dear reader, were in even worse shape than MacLaren was...

...and give A-17 a closer look, and marvel at just how much of that stuff, you actually recognize now.

Our journey has been a tremendous one so far, and we need to stop every so often, not just to rest, but to consider.

Consider just how far we have traveled along this road together.

Our original starting point is so far behind us now, that it is no longer visible, and we are no longer the same people who set out from that starting point.

It is good to give these sorts of things (and ourselves, too) their rightful acknowledgment, and take maybe a little bit of pride in how far we've come, and where we are...

...now.

That said, A-17 ain't all so very much to see when it comes to getting a proper look at our Air Washdown Exhaust Ducts, so let's return to our journey and zoom on in for a closer look.

And there it all is, on 79K14110 M-100, where we see our Air Washdown Exhaust Duct crammed in there between the W36 and the Canister Guide Rail, not quite hitting the Orbiter Side Seal Panel Torque Tube (and I've got a feeling that the installation work for these things was just loads of fun), a little less than two full feet above the smooth deckplates of the RSS Main Floor, in the near vicinity of the Orbiter Mold Line (which is not shown in this drawing).

What happens to anything that winds up on the floor, beneath those Exhaust Grilles, I do not know.

Maybe they pick it up the old-fashioned way, using the Central Vacuum System, which you can see a schematic of, plus a delightfully old-timey-looking Pump and Separator Unit, as shown here on 79K14110 M-125.

And in all of the ways we've seen on this page (and a few more that we haven't), the PCR Main Doors do their job of keeping the Great Outdoors... outdoors, and keeping the Great Indoors... indoors, although by now you should be fully appraised of the fact that "clean" rooms can only be kept "so clean", and no cleaner, and it comes down to a tradeoff between how much time and expense you might want or need to go to, in order to achieve a given level of "cleanliness" which should be enough to get the job done, and no more, (and there are places on this planet that make the PCR interior cleanliness level look positively filthy in comparison to), and yes, it's cleaner than an operating room at a hospital in there, but you should now be sort of wondering about just how clean it really is inside the room where you're getting your heart-transplant operation.

And above and beyond that...

Well...

Some of that stuff is pretty hard to get to, up in there, up in some of the nooks and crannies up in some of those places...

And there are times, and there are places...

...where letting sleeping dogs lie is the best and most prudent course of action.

Our Clean Room gets an alcohol wipe-down, every time, before it goes operational, and that makes a huge difference...

But there's always those little niggly little places and things...

And...

Enough already.

Let's get on with this, already.

And so they do.

MacLaren's Images and Stories Pad B Stories - Table of Contents

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