joe walker x-15 record...

 

On this date, Aug. 22, 1963: NASA Chief Research Test Pilot Joe Walker, on his 25th and last flight with the X-15 program, attempted to fly to maximum altitude. Engineers had predicted that the X-15 was capable of reaching 400,000 feet but simulations had shown that a safe reentry from that altitude was risky. For this flight, number 91, the flight plan called for 360,000 feet to give Walker a safety margin. Experience had shown that slight variations in engine thrust and climb angle could cause large overshoots in peak altitude, so this was not considered an excessive safety margin.

Walker and the X-15 were airdropped from the Boeing NB-52A Stratofortress the High and Mighty One at 45,000 feet above Smith Ranch Dry Lake, Nev., about half-way between Reno and the NASA High Range Tracking Station at Ely. Walker ignited the Reaction Motors XLR99-RM-1 rocket engine.

This engine was rated at 57,000 pounds of thrust. Experience had shown that different engines varied from flight to flight and that atmospheric conditions were a factor. Thrust beyond 60,000 pounds was often seen, but this could not be predicted in advance. The flight plan called for the duration of burn to be 84.5 seconds on this flight. The X-15 climbed at a 45-degree angle.

As Walker was about to shut down the engine according to plan, it ran out of fuel. The total burn time was 85.8 seconds, just slightly longer than planned.

Milton O. Thompson, in his book At the Edge of Space: The X-15 Flight Program, said of the flight, “At burnout, Joe was passing 176,000 feet and traveling at 5,600 feet per second. He then began the long coast to peak altitude. It would take almost 2 minutes to reach peak altitude after burnout. Two minutes does not seem like a lot of time but try timing it. Just sit back in your easy chair and count off the seconds