by Paul Dye
It was easy to forget that, near the end of the program, we had people working in key positions who weren’t even born when the Shuttle flew into space for the first time. In the long run, of the six airframes built, two were lost in tragic accidents and four survived to be placed in museums long before their time. The same two launch pads were used at the Kennedy Space Center (KSC) from start to finish, and all the vehicle prep was done nearby in the Orbit Processing Facility and the Vertical Assembly Building. Thousands of people worked tirelessly at KSC to get the birds ready to go, and to receive them when they came back. Space Shuttle program management, the operations team, and the astronauts all lived in Houston, working at the Johnson Space Center (JSC). Mission Control was located there, in the same building it occupied for the Gemini and Apollo missions that preceded the Shuttle. The building grew over time, with flight controllers and ground teams eventually occupying five different control rooms and many more support rooms throughout the life of the program.
The JSC Mission Operations team, as it came to be called, was responsible for planning Shuttle missions, training the astronauts and flight controllers for those missions, and then conducting those missions, from the moment of liftoff until the vehicle had been safely returned to the runway and turned back over to the KSC team, who would then prepare it for the next mission. Mission Control was the focal point for the entire operation when a Shuttle was in space, and the center of that focus was the Mission Operations Control Room (MOCR), which oftentimes was referred to by its simpler name, the Flight Control Room (FCR). Teams of a dozen or more flight controllers resided in the FCR at all times during a Shuttle mission, led by a Flight Director. But the FCR flight controllers were really just the tip of the iceberg—each of them was supported by a backroom team of between two and ten people, and those support rooms were supported by their own discipline teams. In addition, the entire engineering community was available and participated in troubleshooting and evaluation work throughout a mission. So when people around the world saw the FCR, what they saw was a fraction of the staff. They really had no idea the number of people supporting those men and women who oversaw the entirety of a Shuttle flight.
Sitting in the middle of the FCR was the Flight Director who oversaw all real-time operations and, in fact, had the responsibility and authority to do whatever he or she felt was necessary for the safe and successful execution of the mission using procedures and rules that had been developed over the years of space operations. A Flight Director led the team to execute the mission plan and to modify it as required to achieve the mission they were sent to do and then bring everyone back to Earth. It was easy for those outside the business to think that the astronauts and the people in that small room did it all, but anyone who filled one of those positions would be the first to admit that we all stood on the shoulders of giants—and an uncountable number of giants at that. It was a huge operation, and it was hard for those deep in the trenches to get a handle on it. It was the job of the Flight Director to “conduct the orchestra,” so to speak, to bring all the disparate parts, plans, and systems together to achieve the mission goals. The hardware and software (supplied by the engineering and programming community) had to be ready, the mission planning had to be ready, the payload had to be ready, the crew and flight control teams had to be ready—and when they were, it was a magnificent thing to watch. Many would argue that the team was at its best when it encountered difficulties, and it would be hard to argue with that—for watching great people use their skills and talents to overcome obstacles is an amazing thing to behold.
The Space Shuttle was the product of many different disciplines working on its physics, structure, and systems. A Flight Director had to grasp it all—though he or she was surrounded by experts who could support that knowledge with details. And the Shuttle was all about details. Millions of lines of computer code had to be right. The mathematics and physics of orbital mechanics had to be calculated to many significant digits. Systems were only as good as the tiniest nut or bolt. And everything depended on the skills and knowledge of the many people who had to do complex jobs accurately and at exactly the right time.
Before we can really talk about what it was like to fly the Shuttle, we need to understand how and why it flew. From the basics of orbital mechanics to the esoteric nature of complex systems and flight plans—it’s important to know why and how things worked on the Shuttle in order to put the events during thirty years of missions in context. New flight controllers spent at least two years coming up to speed on the basics of spaceflight before becoming certified for the simplest backroom position. I’ll try to condense that primer down a bit—but still give you insight and an appreciation for the complexities of the Space Shuttle systems.
To many, the Space Shuttle looked like an airplane. In fact, that observation isn’t far from the truth. Built primarily of aluminum and some exotic metals, the Shuttle was manufactured by an airplane company (North American Rockwell) using the knowledge and skills they had obtained from decades of building some of the finest aircraft ever to grace a military ramp. Immediately preceding the Shuttle program, North American built the Apollo Command and Service Modules, and before that the X-15 research aircraft. Before that—some of the best fighters and bombers of World War II and the Cold War. They knew how to build airplanes.
The Orbiter itself was the size of a small airliner, a short DC-9 perhaps. Because I grew up with the early years of the space program, it was easy for me to think of spacecraft being the size of those used during the Mercury, Gemini, and Apollo programs. So when I first saw an Orbiter, I was shocked and amazed—the fact that something this big could go into space was almost incomprehensible. You almost have to look at the two generations of spacecraft side by side to see just what a huge leap the Shuttle was from what had come before. It wasn’t as tall as a Saturn V, the rocket that took Apollo to the moon—but so little of that vehicle came back. The fact that the entire Orbiter returned was simply mind boggling.
The Orbiter had a fairly conventional configuration for a delta-winged aircraft (one with all the lifting surface located all the way aft, and shaped like triangle). Its fuselage was taken up mainly by the cargo bay, the crew compartment was at the front, the wing was fairly far back, and it was topped off with a tall vertical tail. There was no need for a separate horizontal tail because of the delta wing, and both pitch and roll control were provided by the elevons—a combination of elevators and ailerons. The rudder (the hinged rear portion of the vertical tail), was designed in two pieces and hinged at the front. These two sides could split, spreading out in a V shape to act as a speed brake for better management of energy during the final approach to landing.
The aircraft had conventional tricycle landing gear, with two wheels on each main gear strut, and twin nosewheels on a single strut. Many airplane-savvy people who saw an Orbiter up close were surprised to find just how far aft the wings were mounted—but that was a consequence of the delta planform. The main spar (the primary load-carrying structure in the wing) was actually located at the very rear of the payload bay, so most of what people considered to be the usable space in the Orbiter was located ahead of the wing. This actually created challenges when designing missions because you had to work hard not to make the vehicle nose heavy by putting too much stuff up front. The ideal payload was a useful dense mass in a small package, located near the rear of the payload bay—anything heavy and forward was just a problem.
The payload bay was mostly empty space, of course, until it was loaded. Two large payload bay doors allowed the entire top to open up, and the Shuttle always had to fly with the doors open when it was on orbit to expose the cooling radiators (located on the sides of the doors) to dissipate the heat generated by the vehicle’s systems. The crew compartment, located forward of the payload bay, was the only pressurized, habitable volume in the spacecraft—the payload bay and the aft compartment (which could be considered as the engine room) was allowed to operate at a vacuum
while the vehicle was in space. A series of vents allowed air to flow out of the unpressurized spaces as the vehicle flew out of the atmosphere on ascent, and then flow back in as the vehicle descended to land. Mechanical doors closed the vents off during the hot part of entry to prevent high-energy plasma from torching anything inside.
The engine room, or aft compartment, housed all the mechanical systems needed to support the main engines. Their power heads were actually inside the structure. The main engine nozzles stuck out the rear of the compartment, of course. The aft compartment itself was filled with plumbing and wiring—the guts of a mechanical beast, with all sorts of tubes, ducts, and pumps representing the mechanical organs of the monster. Although the types and functions of the equipment might baffle the average aircraft mechanic, the construction and complicated nature of wiring and plumbing equipment would have made him feel right at home.
Attached to the upper rear corners of the aft fuselage were two large pods—one on either side—that housed the Orbiter’s aft maneuvering jets: the Reaction Control System (RCS) and the Orbital Maneuvering System (OMS) engines. All the propellant for these rockets was stored in these aft pods. Along with another set of tanks and jets in the nose (the forward RCS pod), these accounted for all the fuel used to maneuver the Orbiter while it was in space.
Fuel and oxidizer could be shared between the right and left rear pods, but the forward pod was completely separate, as no one wanted to run propellant lines all the way down the length of the vehicle. The more fuel line you run, the more chances you have for leaks, and the propellants used in the Shuttle were pretty volatile. So the pods were designed to be isolated front to back, and that inability to share propellant between all three pods caused some challenges for the flight control teams over the years. It was manageable, just another limitation, but it would have been so nice at times to be able to share gas all the way around.
As far as the crew compartment, the space available for humans was remarkably large when you compared it to previous spacecraft. Going from a Mercury to a Shuttle would have been like going from a broom closet to a living room—and the Shuttle even made the Apollo feel like a small bedroom. The crew compartment was divided officially into three decks, although this confused the heck out of most people because only two were actually usable. The upper deck, the Flight Deck, was where the primary flight controls resided, and where you really flew the vehicle. The Mid-deck was really the living quarters. It’s where everything was stowed, where you could eat and sleep, and where experiments were usually stowed and operated until larger payload-bay-mounted laboratories came long. We thought of these two spaces as the upper and lower decks. But the Mid-deck was given its name because the Lower Equipment Bay (LEB) was located below the Mid-deck. Technically, yes, it was another deck—but it wasn’t a basement. It was more of a crawlspace, and it was loaded with tanks, plumbing, fans, pumps, and all sorts of mechanical gizmos that needed to operate inside a pressurized space (unlike all the gizmos located in the vacuum of the aft compartment).
The crew compartment also had an airlock—used to prepare for space walks (aka Extravehicular Activity, or EVA) and as a tunnel connecting to the payload bay. It was located in the Mid-deck, and it took up a fair amount of space. Later in the program it was moved out into the payload bay to serve as a mount for the docking system used to connect to space stations such as Mir and the International Space Station (ISS). Moving the airlock gave the crew a lot more room in their compartment, and while it took room from the payload bay, the fact that payloads rarely took up all the space available made this an easy move. The Mid-deck was famous for its walls of lockers that lined the forward and aft faces. A Mid-deck locker was about the size of a small suitcase, and could carry 60 pounds of stuff—whatever that stuff might be. There was a repeating pattern of attachment points on the walls where they could be mounted—just like a set of LEGO bricks. It was a flexible and useful system that allowed for prepacking of cargo and consumables (like food and clothing) from anywhere in the world. Lockers could be shipped fully loaded to the launch site and installed in the vehicle, meaning that no one on the pad needed to pack individual items.
The lockers started out being identical, but it wasn’t long before someone invented the double locker (it mounted in the same space as two regular lockers). And then someone incorporated an experiment into a locker-like device, with a control panel on its front door. And then someone invented a collapsible locker, and a soft locker. But everything was always referenced back to a standard size and weight—the Mid-deck Locker Equivalent (MLE). Hundreds of years from now, when humans are exploring distant planets in spacecraft of unimaginable size and complexity, my bet is that they will still be building cargo and equipment manifests based on MLEs, and no one will remember where the term came from—just like today when we measure liquids in gallons.
The Mid-deck was the location for sleeping, eating, and, of course, using the bathroom—the Waste Management Compartment was located over in the corner, just near the side hatch, where the crew entered the vehicle. The Waste Management Compartment was a little alcove that housed the space toilet and lots of hygiene stowage—toilet paper, towels, cleaning supplies, and the like. Famous for malfunctions, the toilet actually worked pretty well most of the time—it is just remembered for the times it failed because, well… it was more than a little inconvenient to have a crew of seven people all floating around, waiting for the toilet to get fixed. Very few things—other than maybe a fire or a cabin leak—took precedence over fixing the facilities when they were having issues. Thousands of items were stowed in the Mid-deck, from food and clothing to cameras and scientific equipment. Tools for fixing things, spare parts for the Orbiter and space suits, and all the accouterments for daily living filled the locker space. And bulky items such as Launch and Entry Suits (the orange suits the crew wore just for getting into orbit and coming home) took up nooks and crannies in the corners.
The Flight Deck was usually crowded with people, of course—that was where so much of the work was done when you were flying. The robot arm was operated from there, and windows looked out on the payload bay to provide line of sight for moving things around. The forward part of the Flight Deck was familiar to anyone who has ever seen an airliner’s cockpit—lots of switches, instruments, and control panels all around. All critical controls were placed here, things that needed to be operated in a hurry on ascent or entry by the commander and pilot. The aft station controls were for on-orbit operation. Located on each side of the aft station were consoles that could hold mission-specific panels—controls that were designed to operate specific payloads. They would be changed out to support whatever mission was being flown.
While public relations pictures of the Orbiter’s Flight Deck usually look pretty clean and organized, the reality is that when a Shuttle was flying, the Flight Deck became a sea of wires and cables fastened to console and panel surfaces with Velcro straps and loops of duct tape. Cables were needed to connect laptop computers (which didn’t exist when the Orbiter was designed, so there were no provisions for LAN or power cables), for cameras and camcorders, and for all sorts of experiment cables that needed to connect boxes to each other and into the Orbiter systems for power and data.
In the early Shuttle days, we envisioned that it would be far too complicated to have every astronaut wearing a headset with a cable attached to the vehicle—everyone would get hopelessly tangled up, or would have to remain in one spot for hours. So we designed a wireless communication headset—a box was worn on the hip or thigh, and a headset was connected to that. It was an early form of a cell system, in some respects. And it was awful. A lot of time was spent trying to connect up, there was interference, batteries went dead… I remember long training sessions with multiple crewmembers all trying to figure out how to make it work. Eventually, the system simply fell into disuse in favor of a simple handheld microphone and a cabin speaker—just like pilots used in the old days, before the invention of comforta
ble, lightweight headsets. We discovered that it was just as easy to let everyone hear the ground calling, and for someone to pick up the mic to answer back. It was only during ascent and entry that you needed instant communications anyway—going simpler just made things more civilized on orbit.
While it is easy to concentrate on the form and structure of the Orbiter when looking at how it operates, the real heart of the vehicle were the systems that made it work. The early flying machines rarely had anything more than cable-controlled flying surfaces and an engine that ran at full throttle (when it ran at all). The pilot had a wicker chair and maybe a rope to use as a seat belt. There were precious few instruments—maybe a couple of gauges to monitor the engine—and, of course no communications other than shouting at people on the ground.
Modern aircraft have a huge variety of systems, many of which now challenge the Space Shuttle in complexity and sophistication. After all, the Shuttle design was essentially frozen in the mid-1970s, and a lot has happened since then. But even given that modern technology has progressed, the Shuttle is still one of the most complex flying machines ever built, primarily because it had to be a rocket, a space station, and a winged entry vehicle—not to mention an airplane—all in one package. As such, the variety and complexity of the systems were far beyond just about anything mankind has ever built. In order to understand how and why the Shuttle was operated and flown the way it was, it is necessary to take a look at those systems and the people who operated them—so let’s begin.