Once upon a time, out on Cape Canaveral, they had a place they called the SPIF. No lie. That's really the name of the place. SPIF stands for Shuttle (as in Space Shuttle) Payload Integration Facility. Cripes, but they do love their little acronyms out there.
It just so happens that I was one of the people who worked out there.
Twice, in fact.
I was there on behalf of the people who furnished the structural steel out of which the SPIF was built, and later on I was there once again, on behalf of the people who played a role in the final tweaking and twiddling to bring the damn thing on line for the end user, the Air Force.
Wherein lies the story of The SPIF Cap Rails.
Way back in the early 1980's, Sheffield Steel furnished the structural elements that would be used build the SPIF. I believe the prime contractor on that job was an outfit called Belko. Or something like that. Been a while. We (Sheffield Steel) fabricated and delivered the steel beams and columns to Belko at the jobsite, which was out at the Titan III ITL (Integrate-Transfer-Launch) area on Cape Canaveral Air Force Station, and washed our hands of the matter at that point. What Belko did with our steel after they took delivery of it was none of our concern.
Amongst all the steel, were some "Longeron Columns." Four of 'em, in fact. Said so right there on the structural blueprints. "Longeron Column." Nobody had the faintest idea what the hell a longeron column was, though.
Being the curious-natured sort that I am, I went to the trouble to ask all and sundry what a longeron column was. Nobody knew. Not one single person. And there was no mention of any such beastie in the specs, either. Just that cryptic "Longeron Column" notation next to a few pieces of heavy iron on the drawings, and nothing more than that, anywhere. Odd.
Whatever else they may or may not have have been, the longeron columns were the heaviest steel members that we furnished for the entire project. Great big heavy steel I-beams over a foot square in cross section, weighing well over a hundred pounds per running foot. For this fact alone, they were odd. Everything else we furnished was real light by comparison. Bunch of junky little W8x15's, some platform framing, and stuff that tied back to the existing structure inside of one of the low bays ("low" being a very relative term when dealing with some of the psychotically outsize stuff that exists here and there on the Cape) of the SMAB. SMAB, what a laugh riot! Yet another bizarre acronym. Stood for Solid Motor Assembly Building. The Titan III people hung the solid rocket motors (SRM's, of course) on the sides of their liquid-fueled Titan III cores inside of the SMAB. There was a 350 ton bridge crane up in the rafters of that building, and that's a fairly respectable bridge crane. The SRM's were heavy. Anyhow, there it was. A whole bunch of light steel, tying four outsize columns in place. Looked funny.
Sitting there in one of the two low bays of the SMAB, the SPIF has two "integration cells." The integration cells were the place where the military, or the CIA, or whoeverthehell, was going to place their supersecret spy satellites and mystery machines into a sealed canister for transport over to Space Shuttle launch pads 39A and 39B. Once at the pad, the canister (And again, please do not forget the ridiculous outsize nature of things on the Cape, please. The word "canister" invokes an image of something inside of your house, maybe on a shelf in the kitchen, that you put stuff in, but this particular "canister" was actually quite a bit bigger than your whole damn house.) would be opened up behind closed doors (Yeah, not normal doors, either. Everything's giant.) under a cloak of secrecy and the tip top secret gizmos would be stuffed into the payload bay of the Space Shuttle. From there, it's an eight minute ride to darkest outer space where the devices could go about their clandestine business far from prying eyes. On the structural steel erection drawings (Yup, that's what they're called. Erection drawings.) our longeron columns looked to be at the exact center of both integration cells. A nice matched pair of them about twenty feet apart, standing vertically, in each cell. Hmm...
All of this goofiness should have told somebody something. Or somebody should have told somebody something. Or something. But of course, nothing of the sort occurred. "So what if they've got special labels on every drawing even though nothing else does." "So what if they're longeron columns and nobody knows what the hell that means." "So what if they're four times heavier than everything else that ties them to the existing structure." "So what if they live in the exact center of the integration cells." "Fuck 'em."
And so we did.
The longeron columns were delivered to the job site at the SMAB. Just like all the rest of the structural elements that we furnished for this project. On the back of a flatbed semi-trailer. A very long flatbed semi-trailer, but a flatbed semi-trailer nonetheless. Placed there by a crane on wooden cribbing along with a mess of other steel members. Fresh from our fabrication shop in Palatka, Florida. Ready to go. With bolt-holes drilled, clip angles and gusset plates welded on, and all the rest. Ready to be assembled into a shiny new SPIF.
The longeron columns were put in the shake-out yard along with everything else. The shake-out yard, in case you didn't know, is where structural steel is dropped off at the job site before it can be used in the actual job. It's gotta go somewhere. So it gets picked up by a crane, unceremoniously laid onto bare ground, and just sits there in the shake-out yard until somebody needs it. Sometimes it's up on cribbing, sometimes it's not. As I recall, the area northwest of the SMAB where we put the longeron columns was an area of hummocky sand and grass, rutted with truck tire gouges and generally chewed up by the action of large construction equipment. The longeron columns were summarily deposited on cribbing where they could lay and relax somewhat into the contours of what they were laying upon as long steel pieces will do. Even the heaviest steel framing members, when sufficiently lengthy, have a peculiar rubberyness or even plasticity about them. They're not brittle or rigid at all.
My interest in the longeron columns quickly faded. I had other, more important, matters to deal with. As soon as we'd delivered all the steel, the kind folks at the company I worked for promptly laid me off. See ya. Nothing personal you understand, just that we've failed to pick up any further work on the Cape and can't really justify the expense of having you around. No hard feelings? Sure.
It was not until the passage of two years, one divorce, and the loss of my house, that I would encounter the longeron columns again.
Time passes quickly when you're having such a good time.
Eventually, I was hired by another company that did business in construction out on the Cape. My time had come, albeit a couple of years late.
As luck would have it, Ivey Steel was at that very instant involved in a little something called the SPIF Cap Rails. SPIF! Well alright. I know all about the SPIF. Sign me up. And they did.
The SPIF cap rails were a very small, but very important, part of one of those outré government installations that you generally have to see to believe. The SPIF in its finished form. As any of you who have worked in the military can attest, things aren't always done in the simplest and most straightforward of manners.
As an example of government/military buffoonery, tomfoolery, and maybe even skulduggery, the business of installing the goddamned SPIF cap rails would qualify nicely.
We'll start by describing the cap rails' bizarro job in life before we get into the meat and potatoes of what went wrong with their installation.
Inside the integration cells of the SPIF, the payloads that are scheduled to fly in space have to be manipulated. Things have to be done with them before they can put 'em on top of a rocket. Or inside of a Space Shuttle. Things like servicing and checkout. Perhaps even maybe a little monitoring here and there of the plutonium or uranium in a radio-isotopic thermo-electric generator. Maybe only just some basic plumbing checks for live systems that contain things like nitrogen tetroxide, or maybe unsymmetrical dimethylhydrazine, both of which also just happen to be horrifyingly corrosive and toxic chemicals, or .... well, you get the idea. Some of the stuff going on inside that fucking SPIF is pretty hard-core. Some of this shit will straight-up kill you right away. And some of it will lie in wait, deep inside of you, for a decade or three, and then come at you all sneaky-like after you've forgotten all about it, and finish you off then. None of this crap can ever be considered "user-friendly." And even the more mundane operations all have to be done to a pathologically precise set of tolerances. Once the damn bird's on orbit, it becomes impossible to go and fix things. So they're pretty excitable about doing things right, down on the ground. So in order to do all of this, specialized handling equipment becomes necessary. The cap rails provided a precision gripping surface for a strange device that "walked" up and down the cap rails by means of a set of special notches that were machined into the rails. Using the cap rails, the system could lift or lower, or whatever you needed, any of the space hardware that was being worked on. We're talking seriously high tech, here.
The cap rails looked just about like what you'd expect something like that to look like. They were about six or eight feet long each as I recall, about ten inches wide and maybe two or three inches thick, and they were made out of some kind of extra-fancy special steel that just happened to be stainless as a sort of side effect caused by it's peculiar precision qualities. On each cap rail, at regular intervals, square notches were machined across them from one side to the other. The notches were about two inches wide by an inch deep. The rails also had bolt-holes drilled through them, here and there, in between some of the notches. The holes were wider at their top, with a shelf about half way through, where they narrowed up quite a bit. When screwed into place, the bolt heads rested down on that shelf without protruding above the upper surface of the cap rail, while the shank of the bolt went right on through the cap rail and out the other side. The bolts themselves were fanciness incarnate. Socket-head jobs about half a foot long by three quarters inch in diameter. They were spec'd out as "fillister head cap screws." It took a whopper-sized allen-head hex tool to turn 'em. I'd dealt with bolts like this before while working out on The Cape. Aircraft bolts is basically what they were. The kind of thing that holds the wings on that 747 you rode. Run about a hundred bucks apiece. Toss in another twenty five for the nut. In 1983. Probably cost a little more, nowadays.
All of this stuff, cap rails and bolts, was finely machined. If you looked at any of it in the light just so, you could see a sort of "grain" where the milling machine had made its last pass over the area. Everything was shiny and gleaming, with sharp, unyielding edges that would cut you if you bumped up against it the wrong way. We're talking about things that were machined to the thousandth of an inch here. Or better. Some fancy goddamned crap, ok?
Stop for a minute and try to see this stuff in your mind's eye. Bunches of these cap rail things, six or eight feet long each. Heavy motherfuckers. No way you'd pick one up by yourself. Bunches of the bolts. Packed very nicely and exceedingly well-organized. All looking like something out of one of those cheap science fiction movies from back in the 50's. Stainless steel glinting in the light. Machined edges that would cut you.
The payload bay in the Space Shuttle is sixty feet long. So there had to be at least that much cap rail in each of the places where it was installed. Lotta cap rail.
But there was a fly in the ointment.
The cap rails, although strong as hell, weren't strong enough to support the satellite to the required degree of insane precision, while also supporting themselves. So they lived on top of something stronger. They constituted a cap on that something. That's what the bolts and bolt holes were all about. That's why they were called "cap" rails.
Guess what that "something stronger" was?
The fucking longeron columns.
My cue to re-enter the story on a personal level.
And there, two years later, the longeron columns stood. Literally. The SPIF was mostly complete and the longeron columns were all nice and hung by all that support steel, all of which was furnished and installed to AISC standards. The American Institute of Steel Construction. AISC is the spec that they build things like bridges and skyscrapers to. Get your hands on a copy of the AISC Steel Construction Manual, some time, if you can. Makes for some fascinating reading. I more or less lived, ate, slept, and breathed that goddamned book for ten full years of my life. That fucking book is the bible. And the integration cells in the SPIF were built to it. Complete with folding access platforms on every level, keypunch locks on every entrance, seventy-foot high, RF-shielded doors, and a space-age slick epoxy floor that the monster air pad machine glides across. Can any of you see where this is going yet? No? Well maybe think of building an airplane or a rocket to bridge-construction tolerances, ok? Think about that, maybe.
The setup for this job was simplicity itself. Bolt the cap rails to the longeron columns without breaking anything and go get paid for it. Which we did. But except for...
Except for the Air Force quality control guy had a little something up his sleeve. A little something that played a similar tune as all that close-tolerance milling which the cap rails were put through.
He had a fixture. He had a goddamned motherfucking fixture. Two fixtures, actually.
And he bolted his little fixtures to the top and bottom of the longeron column just above and below the very ends of where the cap rails were bolted on. And then he adjusted them up, all nice and pretty-like. And in between his well-adjusted little fixtures, he strung a piano wire. Nice and thin. And then he tensioned it up, but good. Nice and taut. Nobody ever had the balls to actually pluck the fucking thing, to see what kind of note it would have played, but I'm sure it would have been a fine note indeed. It was the very definition of straightness, plumbness, and trueness, just above the surface, for the entire, over sixty foot, length of the cap rail.
And then, with fiendish delight, he put a little doodad on the cap rail that mimicked the action of the machine that manipulates the payloads. the little doodad had a piece that stuck out past where the piano wire was. The piece that stuck out, had a little hole in it. The little hole was about the size of a goddamned BB, like comes out of a kid's BB gun. And inside the little hole about the size of a goddamned BB, the piano wire was stretched on through, right in the center of the hole, not touching the edge of the hole, at any place along its goddamned BB-sized circumference.
And then the Air Force quality man, jaws slavering in carnivorous anticipation, ran the little doodad up the cap rail.
Wherever the shape and location of the longeron column caused the cap rail (which was, of course, bolted to and riding on top of it, and was therefore forced to go wherever the fucked up longeron column went) to waver one way or another far enough so that the piano wire touched the edge of that damnable hole about the size of a goddamned BB which was being carried along up the cap rail as a part of the guy's doodad, a little light would come on, and the quality man would stop, and make a note of it.
That fucking light spent far more time on, than it did off.
We were screwed.
The cap rails, by virtue of living on the back of the longeron column, were so out of plumb that the whole thing was called off on account of they got afraid that the metal edges of the little hole in the quality guy's doodad would chafe the piano wire so hard it would break the sonofabitch.
Remember the longeron columns? Laying out there in the shake-out yard, slowly conforming their shape to the shape of the cribbing that supported them on the hummocky sand and grass?
It was bunghole city.
Now we learned what they meant when they put "longeron column" all over the damn drawings. It meant that these bastards were going to become the backbone of a finicky precision device that had to remain plumb, square and true to within mere hundredths of an inch along its entire sixty-foot length.
I have since learned that a "longeron" is one of the longitudinal, as in "lengthwise," structural members of an airplane's fuselage, or sometimes a rocket, and its job is to keep the airplane, or rocket, from coming apart, breaking into pieces, and falling to the ground all over the place. Fairly serious job to be doing, hmm?
They don't use the AISC Manual of Steel Construction to build airplanes and rockets, either.
The cap rails were taken down and placed in storage.
Many people gathered together in many groups and came up with many fine ideas as to what should be done about the problem.
Some wanted to straighten the longeron columns. This was soon shown to be untenable. Owing to the heaviness of the longeron columns, forcing them into hundredths-of-an-inch straightness along their considerable entire length would be tantamount to placing the icing on a wedding cake, using a Nimitz-class aircraft carrier to do so. There was nothing in the laws of physics that actually forbade such a thing, but you could use up a considerable fraction of the entire age of the universe in successfully prosecuting the endeavor.
Some wanted to relax the stringent requirements for plumbness, squareness and trueness of the cap rails. "How much?" said the people who owned the satellites. "Oh, two or three inches in any direction," came the reply. The satellite people, whose job it was to fuss and fiddle with machines that could cost upwards of HALF A BILLION DOLLARS each, were revived with smelling salts and the conversation was directed elsewhere.
Some wanted to scrap the whole damn thing and build something new and better that would work right the first time. After being shown the catastrophic effects this would have upon the program schedules and budgets for trifling items like the Space Shuttle, Titan III, the NRO (National Reconnaissance Office), the CIA, the DIA (Defense Intelligence Agency), and a few others of equal stature, these people crept quietly out of the room and were not heard from again.
Some wanted to shim the cap rails. This was met with great gnashing of teeth by those who wanted to maintain the not-so-imaginary line formed by the cap rails as originally designed, but when it was shown that there was no way in hell the problem could be fixed in reasonable time, for reasonable money, any other way, they relented.
And so, after due consideration and review by the cognizant authorities, the word was handed down from on high: Go thee, and shim thy cap rails until they doth conform as unto plumb, and square, and true.
Easy for you to say.
The business of shimming things into a proper configuration appears deceptively simple. After all, how hard can it be? Just keep stuffing things under there until you're out where you belong. To understand the fallacy of the above, you must understand how, exactly, something like a longeron column can be out of whack.
Maybe go get a sheet of paper and draw a nice, fat, square letter 'H' on it.
Very nice. You're quite the artist.
Our letter H represents a longeron column viewed in cross-section. Like we'd sliced it in half and are looking down it longways or something. If this were one of the official structural drawings, it would be a "plan view" as opposed to an "elevation view."
The legs of the H represent the flanges of the longeron column. The crossbar of the H represents the web of the column. No, I didn't just now make those names up. That's what that's really called. Flanges and web. Got it? Ok.
You might not know it, but there are four(!) separate and distinct ways that you can push that H around to really horse things up if it was supporting some cap rails.
Keep in mind that the H has one and only one location that it can remain in, to within half the diameter of a fucking BB, if it is to remain plumb, square and true, per the plans and specifications that came walking in through the door unannounced, when it came time to fasten the cap rails to it.
One way to mess things up would be to draw your H a little higher or a little lower than the line it sits on right this second. If it was a letter in a sentence, it would be a little out of place, either too high, or too low.
Another way to mess things up would be to push your letter a little further along, or further back, on the line it now sits on. If it was a letter in a sentence, it would might drift away, pas t the letter in front of it, or perhaps ahead of, or merely nærby behind it.
The third way for our H to be mislocated, would be if it was twisted. Imagine our H with a pin stuck right through the middle of the crossbar (the web). Without actually moving the H anywhere, we could spin it. We could spin it right, or we could spin it left. A lot or a little.
The fourth, and final, way things could go wrong is if you drew your H poorly. Maybe the crossbar isn't quite perpendicular to the legs, but instead slants a little. Maybe the crossbar is a little high or a little low. Maybe the legs aren't perfectly straight. They could slant a little left or a little right. One leg could slant left while the other slanted right. Or vice versa. Or maybe just the top or bottom half of a leg slants a little, while the other half is straight. Or maybe one of the legs is curved a little bit, one way or another. It turns out that, speaking precisely, there is a tremendous number of ways to draw our H wrong. Each and every one of these is represented by an allowable deviation from "true" as the steel column comes fresh from the factory. Only so much, and no more. But it's there. And it has to be taken into account. Steel mills don't use aircraft and rocket specs to roll heavy structural steel, but I'm sure that by now, you already know that.
Along right now, I can see some of you wondering to yourselves about why I'm going to such lengths to push, pull, and twist this H all over the place. Yes? After all, just put the damn thing in the right spot and be done with it. Why all this fooling around with moving stuff all over the place?
The problem lies in the fact that our longeron column has length. We can tie down the top and bottom of our column to any degree of accuracy we care to use, but what goes on between the top and bottom is out of our control. Along its entire length, our longeron column can wave from side to side, bow from front to back, twist from left to right, and just plain be misshapen any old whichaway. All four of these effects can happen in isolation or in combination with any or all of the others.
Which is exactly what we got.
The damn columns displayed a bewildering array of out-of-true symptoms, none of which remained constant over the length of the column. All four columns!
Laying out there in the shake-out yard had well and truly fucked up the longeron columns. That plus the fact that these were literally run of the mill pieces of steel. If only the Air Force had taken the time to specify, and see to it, that the columns be held to a much higher than normal tolerance for plumb, square, and true. Or maybe design-in the shimming from the beginning instead of making us put the cap rails up, and then take them back down and then have to scratch our heads to come up with a fix with a clock ticking on somebody's goddamed space program.
I dunno. This is where I start getting the feeling that every single bastard that ever sits down at a drafting table or computer screen and designs something, anything, I don't care if it's only a fucking rubber chicken, should have first completed a minimum three year apprenticeship in the field, trying to build some of the lame-brained stuff that engineers can cook up. Those damn longeron columns were exactly where they belonged on every single drawing they were shown on. And in every single instance, they were as straight as an arrow. Just perfect! Nothing to it. Just take the straight edge, lay it on the paper, get your pencil, and....ah shit, the hell with it.
So there we are. With four separate out of tolerance conditions that require three different kinds of shimming to bring them back into spec. Do I hear you ask, "Why three kinds of shims, for four out of tolerance conditions?" Indeed.
If the column waves from side to side, no shim is required. Nice, huh? Not really, though. Instead of shimming, you must wallow out the bolt holes that were factory drilled into the flanges of the column to take the cap rail bolts. Round bolt holes must be transformed into horizontal slots. Through a steel flange that's about an inch and a half thick. Not easy, but doable.
If the column bows from front to back, you merely shim for thickness. Take the place where the column is bowed forward the very farthest, and call that zero. Everywhere else, more or less shim thickness will bring things into line with your "zero."
If the column twists from left to right, you shim for slope. The right half of the shim must be thicker or thinner than the left in an amount that exactly cancels out the amount of twist that is expressed across the width of the column flange upon which the cap rails are bolted.
If the column is misshapen, you make a specialty shim that combines whatever amounts of thickness and slope that are required to cancel out the skewed shape of the column at that point.
Is this enough?
It certainly seems like enough, doesn't it?
It's not enough.
It's not enough that we bring the cap rail on a single longeron column into a condition of plumbness, straightness and trueness.
God in heaven, is there no end to this?
There's the small matter of the other longeron column.
We're not shimming to reestablish an imaginary line. We're shimming to reestablish an imaginary plane. A plane that is defined by the flange faces of the pair of longeron columns that live at the center of each integration cell.
Our machine for manipulating satellites rides up and down both longeron-column/cap-rail sets simultaneously and rigidly connects to both, also simultaneously. The cap rails form a kind of precision vertical railroad for a very fussy train that may not tilt from one side to the other. At all.
Despite the Gordian Knot snarl of interlocking problems, the matter was solved with deceptive elegance by my boss, Dick Walls. He determined that things could be sorted out by merely taking straight edges and laying them across the column face at each bolt hole location (where the shims perforce must go) and then extending the straight edge over to the other longeron column and measuring the gap (positive or negative) between the straight edge and the centerline of the longeron column. Not that this is easy, or anything. Imagine a crew of ironworkers farting around with two long straightedges, piddling and measuring at every bolt hole along the considerable vertical extent of the longeron columns. Two sets of these measurements were taken, one for each column. When combined, they yielded, via trigonometric analysis, complete information on column twist and misshape. Side-to-side wave was determined by simply measuring the gap between column bolt hole centerlines with a standard measuring tape. Front-to-back bow was dealt with by measuring off of a piano wire. Easy.
Guess which flunky was tasked with grinding out the trig functions for all the measurements at all the bolt holes (I seem to recall there being a bolt every eight inches along the full sixty foot length of each cap rail) on all four of the columns?
Yep. At your service. No computer. Remember, this was back in the early 80's before computers were as common as toasters. Just me and my pocket calculator which I damn near punched the buttons off of.
The result of all that was sheet after sheet of paper filled with closely-spaced handwritten rows of numbers (I think they were four-digit numbers, but they may have been five, or even six-digit numbers. The experience seems to have traumatized me somewhat, and my mind has blocked out some of the memories associated with it.) that defined the slope and thickness of every single shim. If memory serves me well, there was not a single bolt hole on any of the columns that didn't have some kind of shim. Lotta damn shims.
And of course, it wasn't enough to merely calculate the numbers. They then had to be submitted to Martin Marietta (they held the contract with the Air Force to operate the SPIF) for review and approval. For all I knew, Martin probably had to do the exact same thing with the Air Force who was the actual "owner" of the SPIF.
My numbers went to a certain Ben Dusenberry. Ben suffered from one of those terrible maladies that oftentimes gave everybody else around him severe headaches. The sonofabitch was never wrong. Never. Ever. Every single time I caught him in a mistake with these zillions of sets of numbers, close examination would eventually reveal the problem to lie with my numbers, not his. Every damn time.
Despite that, I still managed to get along quite well with Ben. Actually, I was more or less in awe of the guy. And he, despite being able to do things like take triple-integrals and do them in his head (different job, different story, some other time), was an exceptionally down-to-earth person, and was more fun to be around than most people. What he thought of me is, I'm sure, something else.
And so, the time of crunching numbers came to a close. The numbers were forthwith converted into dimensions for the shims to be fabricated.
Aluminum plate was bought. The shims for slope were all milled down to .250 (yep, that's thousandths) inches on one side, and whatever it took, on the other side. The one I'm holding right this very second (you think I'd leave a job this awful without grabbing off a souvenir?) says .209 on it. The .250 is assumed and the number engraved on the shim is the thinner side. Simple. For thickness, we just bought special aluminum shim plate. At the lower limit of thinness, it was weird stuff. Kinda like great big sheets of aluminum foil, all stuck together. Just peel off as many sheets in a clump as you needed. Strange looking stuff.
Finally, after considerable time was lost and money was spent, the cap rails went back up.
There were the usual problems you might associate with the installation of objects that had to remain plumb, square and true to within three or four hundredths of an inch along their whole sixty-foot length, but we prevailed in the end.
The Air Force quality man was made happy and took his damnable fixtures down, never to be seen again. Don't hurry back, every chance you get pal.
I suppose that somewhere along about here in the story, I ought to get to the moral of the tale. Funny part is, I can't think of what the hell the moral ought to be. My guess is that this story contains three or four morals, all intertwined. I don't feel like cracking my head over it, anyway. The trig functions were more than enough.
The job was bought off, and we decamped. More and better goofiness called, just down the beach road at Space Shuttle launch complex 39-B.
Oh yeah, I just remembered the moral of the tale: The whole thing was a complete waste of time and money, in no small amount, all of which was painfully rendered in exchange for absolutely nothing at all.
The SPIF got shitcanned. It was never used, not so much as even once. Following the loss of the Challenger, the military (which never did like the Space Shuttle) took their bat, ball, and glove and went home. Flew all their stuff on Titan III's and IV's from then on. Military Shuttle missions were canceled. Don't let the door hit you in the ass, on your way out.
For all I know, the SPIF is still there. Forlornly gathering dust. But it's probably been ripped out and modified through two or three newer and stranger incarnations, or has been torn down back to ground level and all that remains is sandspurs and dirt.
Who the hell knows?