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X-15 drop from the B-52 (Air Force Flight Test Center History Office)

Above & Beyond: An Extra Two Seconds

Above & Beyond: An Extra Two Seconds

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(Continued from page 1)

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.

As Allavie rolls the B-52 onto the heading of 222 degrees, at the launch speed of 0.82 Mach, I start the first-stage ignition. Think of this as a pilot light on a gas stove; there is no real power yet because it’s "idling." Joe Walker calls the countdown: "Four…three…two…one…LAUNCH!"

I flick the "Drop" toggle switch. The X-15 falls away and I shove the throttle forward. The acceleration is tremendous, and as I pitch up in a 40-degree climb, the G-forces build. X-15 pilot Bill Dana was fond of saying that because of the 4 Gs against the chest endured during powered flight, the X-15 is the only aircraft in which he was glad when the engine quit.

The plan called for an 80-second burn to reach 282,000 feet and Mach 5.15. But this engine performed very well, and by topping off the LOX, I was able to burn the engine for an extra two seconds, which allowed me to accelerate to Mach 5.45 and peak at 314,750 feet, becoming the first person to fly an aircraft above 300,000 feet and also the first pilot to fly a winged vehicle into space.

The X-15 now starts to decelerate. I can feel the MH-96 firing. At this altitude my standard controls are ineffective, so the MH-96 is now using jets of hydrogen peroxide to control yaw, pitch, and roll, keeping the nose on the proper heading.

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