Sound Barrier: Solutions Debated

The story of how the Bell XS-1 came to be begins with a debate over the most suitable powerplant to break the sound barrier.

The quest to break the sound barrier started long before Yeager took to the cockpit of the XS-1.

Over four years after Ezra Kotcher’s original suggestion for transonic flight research in the autumn of 1939, the AAF decided to act upon his recommendations.  After 1939 Kotcher had become chief of the Vibration and Flutter Unit of the AAF Aircraft Laboratory at Wright Field, the service’s principal aeronautical research and development center.  Kotcher requested that the Design Branch of the Aircraft Laboratory at Wright Field investigate two configurations, one using a General Electric TG-180, an axial-flow turbojet of approximately 4,000 lbs-thrust then under development, the other using the 6,000 lb-thrust Aerojet rocket engine.  By April 1944, the Design Branch had completed the comparative designs and from every performance stand-point, the rocket-powered aircraft appeared the better way to attempt transonic research. 

A TG-180 engine being tested at Convair, San Diego.

To the Navy, such a craft should be jet-powered and have the possible military utility.  The NACA (National Advisory Committee for Aeronautics) generally preferred a jet-powered design purely for research purposes, but would (very) reluctantly consider a rocket-propelled one.  The AAF, likewise, had concerns about a purely research project and was receptive to jet propulsion, but favored a more radical rocket-propelled approach.  By mid-1944, Kotcher had succeeded in persuading the AAF to support a rocket-propelled design.  First Lieutenant Abraham Hyatt, a Marine Corps officer and graduate of the Georgia Institute of Technology with a BA in aeronautical engineering, had worked before the war with the Curtiss, Martin and McDonnell aircraft companies.  

The Douglas D-558-1 Skystreak.

Accordingly, on September 22, 1944, Hyatt issued a memorandum for circulation through the Bureau on a proposed turbojet-propelled high-speed research airplane. Hyatt’s proposed Navy airplane obviously represented the more conservative approach towards the problem of high-speed research; an approach more in keeping with the views of NACA-Navy engineers.  Ezra Kotcher and the AAF on the other hand, favored a more radical rocket-propelled aircraft. Both men’s visions laid the groundwork-literally-for the Navy’s Douglas D-558-1 and the AAF’s Bell XS-1, the first of America’s transonic-supersonic airplanes borne of the ‘compressibility crisis’. 

Lawrence Bell.

When Lawrence D. Bell formed the Bell Aircraft Corporation in July 1935, Robert J. Woods was a 31-year old project engineer with Consolidated (which was moving from New York To San Diego) brimming with ideas and ambitions.  Rather than go to San Diego, he immediately left and joined Bell.  On November 20, 1944, while on a trip to the Air Technical Service Command at Wright Field,  Woods stopped at an old friend’s office after hours.  The old friend was Major Ezra Kotcher.  What began as a friendly chat between two engineers unexpectedly developed into a serious discussion on the problems of high-speed aircraft.  Cautiously, Kotcher advanced the research-aircraft concept, asking Woods if he might be interested.  When Woods demonstrated a desire to involve the company, Kotcher responded in detail. Telling Woods that the AAF wanted a special nonmilitary-type high-speed airplane, unencumbered by military requirements and built well overstrength for safety.  Woods agreed to commit Bell on the spot: the AAF had found its contractor.

Next page in this exhibit.

San Diego Air & Space Museum

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