Machines don't just happen. They are dreamt, designed, developed, built and flown. The Space Shuttle Orbiter came out of the same malaise era that brought us rich Corinthian leather, 180 HP V8s and chassis stiffness akin to a wet sheet. Nonetheless, the orbiter was a remarkable machine. It was designed and built by Rockwell International in Palmdale, CA after an extensive design competition to develop the next generation of space vehicle after the Apollo program and the a Saturn V. The idea was to operate a space craft that could be reused, land and takeoff at multiple sites, fly frequently and cheaply and to haul just about anything. We can debate if the finished product lived up to this billing, but I won't do that here. What we will do is talk about how the shuttle was built.

To operate as NASA desired, taking off like a rocket and gliding back for landing, meant that the shuttle would be a hybrid between a spacecraft and an aircraft. Propulsion, life support and cargo carrying design features would be recognizable to those dealing with spacecraft. The entry and landing requirements resulted in many features and design techniques that are common with airliners and high performance aircraft.

The fuselage of the shuttle would be assembled from frames, stringers and skins in a way familiar to anyone who has been around aluminum aircraft. Riveted or bolted members widely utilizing aluminum were used long with a smattering of composite structures and a few high test details.

The orbiter used some lifting body research in the development of its aerodynamics. That and thermodynamic requirements needed for the heat shield necessitated a flat belly.

This is not favorable for taking pressurization loads of the cabin. As you can see in the image below, the crew cabin was actually circular in shape, like a standard airliner, and was mounted in a cradling structure on the main fuselage. A shell was then installed over the top of it. This forward structure was then bolted to the structure around the keel and sides of the cargo bay. The fact that the cargo doors opened also necessitated a keel structure that was stronger than you would typically see on an airliner. Extensive use of truss structures helped provide a light weigh solution to this problem.

The orbiter's delta wings are constructed in a fairly typical way. Spars run inboard and outboard with forward and aft ribs along with stringers building up the structure. Skins are either aluminum sheet or sheet with bonded corrugated bonded doublers. This stiffens the panels with a relatively low weight penalty. The wheel well structures use this design technique as well.

The tail structure differs significantly from what you would see in an airliner simply because it must house the thrust structure of the Space Shuttle Main Engines. When you have to transfer 500,000 lbs of thrust from each of the engines into the stack you need a beefy structure. The fact that the engines gimbal to help steer the shuttle on climb means that you need need even more strength. While the main orbiter structure was fairly conventional, the thrust structures for the engines used some high test stuff. Strips of titanium were bonded together under very high heat and pressure and then had boron epoxy bonded to the outer surfaces for added stiffness.

The Orbital Maneuvering System pods on the upper portion of the aft fuselage were made with carbon composite skins and honeycomb cores. These cores had to be vented to prevent delamination from trapped air when the shuttle got to orbit.

Orbiter systems were also fairly conventional, but with a high level of redundancy. Most systems are triple redundant, meaning there are three of each. This type of redundancy meant there was a low probability of a full critical failure of a system.

Landing gear and tires on the orbiter were also fairly conventional. In fact, the orbiter gear were deployed simply by gravity. There were no hydraulics like you would see on an airliner. Tires were provided by Michelin and were pressurized to 300 PSI. A bit more than a standard airliner. While an airliner tire is typically designed for 200-300 landings, the orbiter tires were designed for just a few. In fact, they weren't reused that often.

I could spend hours writing about the orbiter's thermal protection system. I won't. There are lots of articles out there talking about the trials and tribulations of getting that system to work. The orbiter utilized carbon-carbon wing leading edges and nose cone, silicon tiles on the belly and parts of the fuselage and thermal blankets in lower temperature areas. It was amazing in its capability, but fragile.

The Space Shuttle Orbiter itself was a remarkable spacecraft that did some pretty amazing things. True, the fact that it was designed to act as a spacecraft and aircraft meant there were some compromises. Also, the fact that we didn't always operate it as it should have been shouldn't be held against it. The loss of Challenger and Columbia can be attributed to design issues with other parts of the shuttle stack and not the orbiter. In fact, once NASA got around to building the station, a mission that the Orbiter was really designed for, it excelled.

Additional photos of the orbiters under construction:

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