The research airplane program’s primary goal was to develop technology that we could put to useful purpose – supersonic high-speed aerodynamics… We had plans to take us [all the way] into space. That was part of the long-range goal for the research airplane program. Unfortunately, that got diverted by many other circumstances.
The productivity of an airplane is gauged by its speed times its payload, divided by its fuel consumption. The way to get that productivity is to go fast. And the way to go fast is to go high. With the engines that we were developing in those days, we were trying to find out what it took to go high so that we could go fast and get the productivity that we needed for the air transport as we saw it at that time – and the way we see it today.
Unfortunately, we took a moratorium on that development for some years; but we are back on track today with the National Aerospace Plane, which is nothing more than an extension of the very successful research airplane program.
On his third flight on the X-15 Crossfield ran into longitudinal instability with pitch oscillation. Crossfield described his actions in the cockpit and how he responded to the problems with the aircraft:
Well, the checkout in the X-15 was rather abrupt in that, on our first flight, we flew it as a glider alone. That gave me three minutes and fifty-eight seconds to learn how to fly the airplane and bring it in for a landing.
On the approach and landing, I had a control problem that really turned out to have a very simple solution. But the airplane, for all intents and purposes, appeared to be unstable and pitched to me, which meant that it was very difficult to control it. The pitching oscillations got very high and I had to figure out a way to get the airplane on the ground at the bottom of the pitching oscillation so that it would not wrap up in a ball of metal.
As it turned out, I succeeded. However, I landed at 140 knots instead of my anticipated 174 knots.
Crossfield described how they adapted the controls to enable the pilot to handle the aircraft when it was in violent motion:
With the X-15 we anticipated that there could be some rather violent motions on re-entry or in some of its maneuvers. One of the difficulties with flying the high speed jet aircraft with the powerful flight control systems is that the man’s arm gets into the thing. The weight of his arm feeds the action of the airplane. That is the so-called “JC Maneuver.”
For the X-15 to preclude that possibility, we made a control system such that [the pilot] could put his arm into a rest that would resist all of these external forces and control the airplane only with the movement of his wrist. With the axis of control being in this manner – with the roll control – we made it so that it could roll on the armrest… So we took all of this spring and mass system – [the pilot’s] arm out of the control system – to make it a very precise control system. It was part of the design of that system that [caused] the problem I had on the first landing. And it was easily correctable.
Crossfield commented on the distinction between pilots and “test pilots”:
Well, we keep talking about test pilots but there is no such thing as a “test pilot.” There are all kinds of people. There are tall people, small people. Some of them are functionally illiterate and some are intellectual. Some are moral. Some are immoral. They are all just people who incidentally do flight tests. It is a profession just like anything else. There is not, to my mind, any common thing called a test pilot.
The opportunity to be a test pilot… is there for all – and probably within the grasp of most. In my mind, we should divest ourselves of this idea of special people [being] heroes, if you please, because really they do not exist.
Crossfield described how his experience has been applied to contemporary aircraft:
At one end of the jet airplane era – with very powerful control systems – we found that the [pilot’s] arm began to become an important part of the inertia. As we got into the jet era and high-speed flight – the very powerful control system that we had – we began to see the effects of a man’s arm on the control stick having an effect on the airplane as the forces on his arm varied.
With the X-15, we anticipated… some of the violent maneuvers [on re-entry] that could probably cause us some problems. So what we did was design a sidearm controller to preclude any input from his arms. It consisted of an armrest that you could hold your arm down on so that the only thing that was involved in the control of the airplane was the rotation of the wrist, with the pitch axis being… through that point and rolling your arm on the armrest. As a consequence then we could take all of that spring and mass system out of the control system. This proved to be a very useful development that we now find very often in our current-day fighters which would have had the same problems if they didn’t go to something of this nature.
Also, that sidearm control was a contributor to the problem that I had on the first landing and we corrected that quite easily.
Crossfield described what happened with the ground test on the first XLR99 engine. He explained why he was in the cockpit when the engine exploded and what happened to him:
When we installed the large engine on the X-15, [because of] our flight test plan we were going to demonstrate that the engine could be started. It could be throttled from 50 to 100 percent as designed on the first flight. The way that we were flying, I was limited to the speeds that I could allow the airplane to get so it took a very precise engine-on-off and thrust program to stay within that flight plan. To make sure that all of the systems would respond to this plan we made the last test of the engine on the airplane on the ground.
This is kind of humorous because the pilot gets into the airplane to run the engine. Everybody else gets into the block house. That is called “developing the confidence of the aviator.” In doing that run, we had a propulsion system failure that was born of something unique to the ground run that caused the airplane to blow up. About 1,000 gallons of liquid oxygen and 1,200 gallons of… and 800 pounds of 98% hydrogen peroxide got together and did their chemical thing. It was a pretty violent activity for a moment or two. It was like being inside the sun. It was such a fire outside that it was a very brilliant orange. The fore part of the airplane, which was all that was left, was blown about 30 feet forward – and I was in it. Of course I was pretty safe because I was in a structure that was designed to resist very high temperatures of re-entry flight.
Crossfield explained how he became a test pilot:
Well, I am an aeronautical engineer, an aerodynamicist, and a designer. My flying was only primarily because I felt that it was essential to designing and building better airplanes for pilots to fly. My professional endeavor really was more in that line than being a pilot per se. It was part of the whole circumstance of designing and building airplanes.
Chapter 2
Rockets Away – Escape from Earth
From the Second World War to the space race
On 8 September 1944 a German V-2 rocket hit Chiswick, West London. The V-2 was a ballistic missile known to its engineers as Aggregate-4. Nazi propaganda minister Joseph Goebbels announced it as Vergeltungswaffe-2 or V-2, the second in a series of “vengeance weapons”, the first being a robot jet plane known as the V-1. The V-2 was fuelled by liquid alcohol and liquid oxygen (LOX), weighed 14 tons and carried 1 ton of high explosive.