The Real X-Men
Life came at you fast when you flew the X-15.
- By Peter Garrison
- Air & Space magazine, November 2007
(Page 4 of 6)
“You’re talking about the change in the acceleration as you continue to accelerate faster,” says Bob White. “Going from Mach 2 to Mach 3 took so many seconds, 3 to 4 took less, 4 to 5, you’re cutting down, and the pressure on your chest, you get up to the point where you’ve got 4 Gs and it’s difficult to breathe. And so as Milt said it was the only airplane he ever flew where he was glad when the engine quit.”
As fuel was consumed and the airplane grew lighter, acceleration increased, and all the X-15 pilots experienced a peculiar illusion: the sensation that although they were holding a steady pitch attitude—a 30- to 40-degree climb—the airplane was actually continuing to climb until it was rotating over onto its back. White himself once failed to make his planned altitude because the illusion of over-rotating was so compelling that he had to push the nose down momentarily in order to glimpse the horizon.
Flights were extremely short—usually 10 or 11 minutes from B-52 to lake bed.
“The time went by like a flash,” says Joe Engle. “I remember counting down the last minute of countdown. There are certain things you do and check-list and hitting the release button [to detach from the B-52] and then from then on, right after the flight I would have been hard-pressed to go into a lot of detail, between that and the time when you finally slid to a stop and cracked the canopy.
“The other thing I do recall is that the cockpit and the suit were pressurized with liquid nitrogen that could be released through a valve. Cooling was the same way: You just opened up the valve to cool it down. Some of it I’m sure is because the skin would heat up in flight, but I recall turning it up, because everybody said turn it up all the way before you launch, and being almost cold, you know, and then again, this flight going by like the snap of a finger, and sliding out on the lake bed and cracking the canopy, wanting to get it open because I was just drenched in sweat.”
Ships 1 and 2 had conventional controls, plus a three-axis stability augmentation system, which would weakly counteract any unintended motions in pitch, yaw, or roll. Ship 3 had the fly-by-wire adaptive flight control system that Armstrong helped design. The system had two purposes: to make the airplane handle similarly in all flight regimes, and to seamlessly integrate the thrusters, used during the weightless coast above the atmosphere, with the aerodynamic controls. It was thought that the airplane might not be controllable during reentry without artificial stability augmentation until Pete Knight experienced a total electrical failure.
“Pete Knight was the best test pilot that I’ve seen,” says Bill Dana. “He had a flight that launched over Smith’s Ranch and headed for Edwards. At 100,000 feet and Mach 4, both his generators went offline. All the lights came on for a few seconds, and then they all went out. And he never had another electron, that he could see, in the whole flight. He flew the climb using ballistic controls to keep the wings level. He didn’t have an artificial horizon, but he could apparently see out. He kept the wings level over the top and then he wanted to get back to Mud Lake to land there, because it’s a long runway. So he made a 180-degree turn to the left and he used more back stick when he wasn’t developing wing rock or lateral-directional instability, and when the airplane was flying too squirrelly he backed off on the G and he came around, and now he had aerodynamic controls—he had reentered, in other words—and so he flew a dead-stick landing into Mud Lake. To me, that’s the greatest single feat of airmanship that I know of.”
Malfunctions as severe as Knight’s were rare, but if the X-15’s pilots felt anxiety, it probably would have been over that sort of thing—being left helpless out at the edge of the world to be burned up or torn apart by an airplane that had turned savage. Says Bob White: “If you didn’t have a little fear when you stepped into this thing, there was something wrong with you, believe me.”