The Launchbox PoD 12: Why the Space Shuttle looked the way it looked

By Francis Castanos



The story of the Space Shuttle is a complicated and tortured one. So have a drink or, better yet, a shot of dark brown coffee and fasten your seat belts. It all started with the orbiter. The original Shuttle (from the summer of 1968 to the summer of 1971) was fully reusable. The first stage was the size of a 747 and somewhat like a hybrid of the (Boeing) S-IC, X-15, and Jumbo Jet. The second stage was the size of a 707. Incidentally, F-1s were considered expendables, although they had been fired for astonishingly lengths of time, for a rocket engine – many minutes or even one hour. This was pretty absurd in retrospect. Also because the SSME lacked raw thrust (blame LH2 again), while the orbiter would take only take 3 of them, the booster would need twelve or F-1s. As well as jet engines to flyback to the launch site. Same for the orbiter, it had a pack of jet engines – which were still used until 1974 ! Have a look at the pictures below. Basically the Shuttle went from the first image to the second image.

Fully-reusable shuttle of North American Rockwell (1969) as drawn by NASA
How the finished Shuttle ended up looking. Again, as drawn by NASA.

The first picture shows how the Shuttle plans looked in 1970 – the drawing is actually the original concept from North American Rockwell, who ultimately built the actual Shuttle used.

But while it was the same contractor – Rockwell – it wasn't the planned Shuttle, not by any means. Because the final result is, well, the second picture.

By this point one is left scratching their head and wondering, how the frack did THIS happen? Where was the huge tank in the original design? (Even if that orbiter looks bigger, there is seemingly no way to ram the final, colossal external tank into it). And what on Earth happened to the booster(s)? It all started with the orbiter (again). In the days of internal tankage, the orbiter was to be packed full with liquid oxygen and liquid hydrogen. Why Liquid Hydrogen, incidentally? Because everything else sucks, except for in density, where it is Liquid Hydrogen that is awful compared to other options. Hydrogen has the most energy (specific impulse) while being reasonably non toxic but, if not deep cryogen, still needs to be stored hundreds of degree below zero which risks making metal brittle. Crucially, it takes 6 tons of oxygen to burn 1 ton of hydrogen, so you need a lot of oxygen. On top of that, while oxygen is very dense, hydrogen density is abysmal: 200 grams of liquid hydrogen takes as much volume as 1 kg of oxygen. The end result was striking: the internal tankage orbiter gets punished twice. Oxygen os dense, but an enormous quantity was needed. And hydrogen was the polar opposite (lame pun assumed): a very little amount of the stuff nonetheless took a huge volume. In fine, both prop volumes equally matched and were a perfect annoyance. The price to pay was a fat orbiter 200 ft long, to store vast ammounts of both liquids, meaning the heatshield would be very broad, an immense surface to protect, perhaps thrice as much as, say, Columbia (sigh). One of the (very) few nice side effects of these huge tanks was, when empty – that is, in orbit and particularly during reentry – the orbiter would be mostly empty volume, that is, more akind to a balloon than a metal brick as per the final result we all know. The end result was that the fully-reusable Shuttle was a huge beast, and it would be also damn expensive: $10 billion in development cost. If spread over only six years – 1972 to 1978 – that would be nearly $1.7 billion a year. And since Nixon OMB and all the Karths and the Mondales and Proxmires in Congress had both decided to reduce NASA's ENTIRE budget to a mere $3 billion a year, you can see where this is going. NO WAY. For the record, at the time NASA also had to fund aeronautic research and space science and Viking and Hubble and Voyager and Skylab and telecommunication satellites and Goddard science satellites and many, many others areas. By summer 1971 the fully-reusable Shuttle was dead on arrival. NASA told the aerospace giants to look for solutions to make it cheaper and smaller and also easier to build. And there started a gradual downward spiral. The hydrogen tank was the first to be kicked out of the orbiter and made disposable. Curiously enough, the LOX tank did not immediately followed and as such, there were some hybrid orbiters before the final move - both tanks out. And then something unexpected happened. By dropping the tanks, not only did the orbiter shrunk, but also the booster(s). It boiled to, the larger the tanks, the smaller the booster(s) with a lower speed, making them easier to recover (you guess where this going. More on this later). So just like the orbiter the booster(s) started shrinking in size, performance, and cost, too. What's more, it no longer needed to be piloted like the orbiter or... a Boeing 747. It could be dunked into the ocean under parachutes. Alas, the more the booster(s) and orbiter shrunk, the more the external grew, fatter and fatter. And thus started the spiral that led to the familiar Shuttle. And then, another shift happened. At the beginning the booster(s) fired first, lifting the whole stack before the orbiter engines started in flight. This was called series burn. And it went through the window when the aforementioned spiral was pushed to its ultimate, logical end. By this point somebody suggested to use the orbiter engines right from the beginning, and fire that in parallel with the boosters. This instantly added a huge amount of thrust at lift-off, apparently "for free". Yeah. While this time the orbiter was (seemingly) unaffected by this, the tank and booster(s) were not, and the tank grew to truly huge proportions. The move also greatly complicated what was now called the SSME, the Space Shuttle main engine. This is because rockets don't start the same at all on the ground or in flight. Plus in order not to burst the orbiter structure during flight, thrust had now to vary during flight, from 100% at liftoff to 70% in the thick of the atmosphere to 100% again for the final push into orbit. The combination of ground-starting and throttleability (geez, what a word) turned the SSME into a beast of an an engine. As if a staged combustion of liquid hydrogen, plus reusability, were not already a tall order. When later the orbiter outweighed its weight limits, more and more thrust had to be added. Now the boosters had shrunk to a point their performance could be VERY miserable. No need for sophisticated SSME or massively powerful F-1s: solid-fuel or pressure-fed could do the job. The later a rocket without a turbopump, where the props are pushed into the engines by pressure only, as the name entails. Think Bob Truax's legendary Sea Dragon.


James Fletcher's official portrait as Head of NASA

On March 15, 1972 NASA administrator James Fletcher went for big solid-fuel boosters. Some said that since both Fletcher and Morton Thiokol were both citizens of Utah, this was pork barrel spending. This is an unfair urban legend: there was a Congressional Inquiry on that, that found nothing. A young Al Gore himself tried to dig up

that skeleton after Challenger and was humiliated.

By April 1972 the Shuttle had found its familiar shape, although many details would change over the 8 next years, and even between generations of orbiters – Enterprise to Challenger & Columbia to Discovery & Atlantis to Endeavor. This is only part of the story, however. Another important aspect relates to the military involvement. Also the Soviets. Let's review this if only briefly. Military and Soviet involvement in the Shuttle early history is altogether a maddening and hilarious story. Pretty much bonkers, too. And certainly unbelievable. The military, first. NASA quickly found the Shuttle needed 40 to 60 flights a year to beat the dumb ordinary rockets into submission. To achieve that however it had to fill its payload bay with every single commercial, civilian and foreign satellites, plus the robotic probes, plus manned spaceflight, plus creating new markets by being cheap to launch. And of course the military. Very important. Officially it was USAF, orphan of both DynaSoar and MOL. The reality was that the NRO pulled the strings in the shadows: the spy satellite agency very own existence was negated until 1992. From 1959 to 1984 no less than 250 cheap, mass-produced Agena-based spysats were launched, most of them CORONA and GAMBIT. By the early 70's however the paradigm was changing: 144 CORONA would be replaced by only 20 KH-9 HEXAGON. In June 1971 a new breed of spy satellite – the KH-9 - was launched by a Titan III, and it was an enormous beast: 60 ft long, 10 ft wide, 40 000 pounds. Sound familiar? These numbers roughly match the Shuttle payload bay and it is NOT a coincidence. 40 years after the facts the NRO has acknowledged the KH-9 HEXAGON drove the Shuttle payload bay size. Incidentally, no KH-9 would ever be launched by any Shuttle, the NRO having quickly (by 1975!) thrown its involvement in the program under a bus. Only after its severe requirements shaped, if not ruined, the entire Shuttle. Go figure. In a nutshell, so long and thank you for all the fish, and also thank you for having supported the shuttle - like a rope supports a hanged man. The military also drove the crossrange, somewhat: KH-9 had to go into polar orbit for full coverage of USSR. Except The Cape couldn't handle that without dropping bits of Shuttle boosters and tanks all over the East Coast and... Cleveland. So Vandenberg it was, the former MOL launch pad in California. And then come the bizarre idea of launching from Vandenberg and land back after a single orbit, with the Earth having rotated below – the so-called missions "3A" and "3B". And here, come the Soviets. While the US military was merely hypocritical, the Soviets then just went idiotic. And the story even weirder. In a very bizarre, completely insane twist of Cold War -fueld paranoia, the Soviets went completely bonkers and ended believing that the Vandenberg mission would drop, not a KH-9 in polar orbit but rather, a Polaris warhead on Moscow for a decapitation strike. Read that carefully, again. The Shuttle would be a space nuclear bomber to incinerate Moscow by surprise. Read the details here. The Shuttle would liftoff from Vandenberg, overfly Moscow during ascent, then dive down to 50 miles sneaking above the SAM belts and below the A-135 ABMs, flip over, open the payload bay doors, drop some Polaris or Minuteman warheads right into Moscow, incinerate the Politburo without any warning, close the doors and ascend again before crossranging over 1500 miles to catch back Vandenberg and land. Okay... And no kidding, the idiots who come with that whackiness were not scary Soviet generals from the Stalin days but actually top Soviet matematicians, and the best of the lot with that, disciples of the great Keldysh. Most of them veterans of Sputnik and Vostok trajectories.

Wow.

Good mathematicians, for sure, but VERY LOUSY Cold War analysts. Whatever. Needless to say, this greatly helped the case of Buran, at a time when the Soviets truly banged their heads against (Kremlin) walls trying to wrap their minds over NASA Shuttle economic case. Imagine, 700 flights with 30 mt each, 21 000 tons send into orbit between 1978 and 1990 – WTH ?!!! (I calculated this amounts to 175 Apollo flights or 14 Mars shots – 120 mt and 1500 mt ships, respectively). The only remote answer they could conceived was "thiz iz a mazive ABM – ASAT - FOBS military space program in disguise... !! spaceborne anti-satellite, anti-missile weapons...!! " Wait, does that sounds familiar ? SDI, my dear. Star Wars. Except this was 1973, not 1983, and President Raygun was still 10 years in the future. So the Soviets were kind of randomly right about the Shuttle, except ten years in advance, and of course... the Shuttle was never used for SDI...oh well, forget that. Murphy law as its best, the evil wicked thing. ROTFL. Whatever the Soviets wild speculations about its true purpose, fact is the Vandenberg polar mission cascaded into the necessity of a 1500 miles crossrange... and only a delta wing could achieve that.

This was the next step toward the familiar orbiter, after the external tank: delta wing and huge payload bay. Only the 3*SSMEs were still lacking, somewhat. Whatever, MSC-037 was the first sketch vaguely looking like the familiar orbiter. Variations quickly followed with three or four Apollo J-2s, and then with SSMEs (MSC-40, she is the one!). Oh, and at some point was MSC-042, the familiar orbiter shape except without any engines... NASA's very own Buran. Those russians... And the rest, as they say, is history. Remarkably, while in 1972 the OMB had allocated NASA $5.15 billion over six years (or burst) to build the Shuttle, the Shuttle inevitable cost overrun was "only" 20%, total $6 billion. Not much when compared to such disasters as the C-5 Galaxy or... the F-35. And not bad considering the Shuttle was three years late.

In fact NASA remained on track for a 1978 first launch until 1976-77, when two immense PITA were encountered: falling tiles and exploding SSMEs. Few people realise that while STS-1 happened on April 12, 1981, Columbia had been ferried to the Cape exactly... 2 years earlier (!) on March 27, 1979. There are spectacular pictures of the 747-SCA landing with a peeled-off, white-and-brownish orbiter on its back. Somewhat amazingly, a mere cross-country flight at Mach 0.7 had send the tiles flying away. Geez. What would happen at Mach 27 was now pretty frightening.

Columbia in March 1979

Meanwhile in the years 1977 and 1978 early test fires of SSMEs resulted in larger and larger troubles until KABOOM, both engine and test stand just blew up. Things improved only gradually and so the projected first flight dates started moving further and further in the future at a truly alarming rate. Meanwhile Rockwell and NASA engineers went to The Cape and realized, to their horror, that they would have to examine and re-glue every single one of Columbia's 30 000 tiles.

It took two years to overcome the odds but they finally managed to pull it out. Still the Shuttle that started flying soon proved a difficult beast to be tamed. The most worrying aspect of all this, however was that NASA had bet and promised so much to everybody, there was no space for any doubt about the entire system viability. It was succeed or burst, as simple as that. Well, we all know how it ended some years down the road. More on this in a later entry - the roots of the Challenger disaster.

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