Above and Beyond: An Extra Two Seconds
- By Robert M. White as told to Al Hallonquist
- Air & Space magazine, May 2010
Air Force Flight Test Center History Office
(Page 2 of 4)
"Bob, you know we never let beginners fly this thing," he replies. "You just stick to your toy airplanes and leave the real flying to the pros."
The climbout goes smoothly. The drop pilots will breathe easier after we pass 26,000 feet. Below that altitude, they cannot release the X-15 in an emergency; I would not have enough time to fully jettison the propellants. The excess weight of residual propellants would result in a faster-than-normal landing, and that extra weight could cause structural failure. We had discovered the problem when an X-15 landed with residual propellant: Its fuselage buckled and landing gear collapsed. Above 26,000 feet, the X-15 pilot can either bail out or vent the tanks and land.
During our ascent some of the liquid oxygen (LOX) has boiled off. I have the panel operator top it off. I’ll need all the fuel and oxidizer I can get to surpass 300,000 feet.
We’ve been flying northeasterly en route to the Delamar Lake launch point. Allavie has to time his 180-degree turn to launch me precisely: Being slightly off course could greatly displace the X-15 from the planned route, especially during reentry.
Initially, the B-52 pilot dropped the X-15. But if a pilot tried to yell over the interphone that he wasn’t ready, he might not be heard, and on one flight, the X-15 was very nearly dropped before the pilot was ready. Now the X-15 pilot has complete control of the drop.
One minute prior to launch, I see that a glitch causes the Minneapolis Honeywell MH-96 flight control system to shut down. The "Mini-Honey" takes into account the variables that occur over a vast range of altitudes and speeds—temperatures, atmospheric and dynamic pressures, and more. Without it, the aircraft might not be controllable during reentry. (A precursor to the "fly by wire" systems in virtually all current military aircraft, the MH-96 made the X-15 easier to control with either the aerodynamic control system for flight in the atmosphere or the reaction control system, which was used at very high altitudes where there is no discernible atmosphere.)
Standard procedure says to abort if this system is not working. The MH-96 had been thoroughly tested in prior flights by Neil Armstrong, and performed well. So it’s understandable that when a shutdown occurs, things get a little tense in mission control and on board the B-52.
I do a reset; the MH-96 comes back.