Free Bold They Rise: The Space Shuttle Early Years, 1972-1986 (Outward Odyssey: A People's History of S) by David Hitt, Heather R. Smith

that would allow the astronauts to control use of that software to control the vehicle. In addition, he said, a conflict arose because of the computer use needed to develop and test that software. To the engineers who were using those computers to design the vehicle, the time the astronauts spent testing and practicing with the flight control software seemed like “video games.”
We ended up building a team of people: Joe Gamble, who was working the aerodynamics; Jon Harpold, doing guidance; and Ernie Smith, who was the flightcontrol guy. They all worked in E & D [Engineering and Development]. We all got to going around together in a little team, and we would all go to the simulators together, and we would all study things. We built a simulator from Apollo hardware that was called . . . ITS , the Interim Test Station. We had a couple of people—Roger Burke and Al Ragsdale were two sim engineers that had worked on the CMS [Command Module Simulator] and the LMS [Lunar Module Simulator]. They were very innovative, and they took these things before we had the Shuttle Mission Simulator that was back in the early part of the design and went to the junkyard and found airplane parts and built an instrument panel out of spare parts and had a regular chair that you sat in and had different control devices that we had borrowed and stolen from places. These folks were so innovative; they could hook it all up.
    “They took the initial aerodynamic data books and put them in a file so we could build something that would try to fly,” Mattingly said.
We even took the lunar landing scene television. In the Lunar Module Simulator they had a camera that was driven by the model of the motion and it would fly down over the lunar surface, and so you can see this thing, and that was portrayed in the LMS as what you’d train to. So they adapted that to a runway. We tried to build a little visual so we could have some clues to this thing, put in a little rinky-dink CRT [cathode-ray tube] so we could play with building displays. And we got no support from anybody. I mean, this wasn’t space stuff. And it is probably one of those things I was most proud of, because we were able to get this thing into someplace where we could actually tinker with how we’re going to fly the vehicle and what we’re going to do and what the aerodynamics mean. It was only possible because we had these two simulator guys who were wizards at playing with software and this team from E & D who joined us.
We ended up realizing that we had built an electric airplane that had essentially only one operating flight control system. So we said, “Well, what if we’re wrong? No one has ever flown a Mach 20 airplane. This whole flight envelope is something that nobody’s ever had the opportunity to experience. So what do you suppose our tolerance is to this?” Because wind tunnel models for the ascent vehicles, they fit in your hand, because the tunnels that were able to handle these things were small. The wind tunnel models for the orbiter were larger, but they’re still not all that big, and going through this tremendously wide flight regime where the air density is going from nothing to everything, and it’s justhigh speeds to low speeds, I said, “What’s the chance of getting all that right?” And yet as we played in these simulators, . . . we proved to ourselves that, boy, if you’re off on that estimate of the aerodynamics, you can often play with the software to make it right, but if the real aerodynamics and the software you have don’t match, it’s a real mess. I know I worried a lot about that.
So we came up with a concept that we would have some tolerances on the aerodynamics, and we would try to make sure that the flight control system could handle these kind of uncertainties in aerodynamics. We did something which is not typically done—we decided to optimize the flight control performance to be tolerant on uncertainties rather than the best