NACA Ends Compressor Research

The NACA research on transonic and supersonic compressors remained classified until the late 1950s. (Even the design “bible,” which focused on more conventional stages, was classified until 1958.) Consequently, the results of the research were not generally disseminated to those outside the United States, and even in this country they were not readily accessible. Moreover, unlike the “bible,” the reports themselves were aimed more toward providing a record of what had been done than toward instructing those outside NACA how to exploit the results. Even today, when read from the perspective of our far greater knowledge of transonic and supersonic stages, the reports are not always easy to assess. A large fraction of the knowledge that the NACA had gained on high Mach number stages remained in the heads of the engineers who had conducted the research.

This knowledge diffused out of the NACA through more than publications, however. Many engineers who had worked on high-Mach-number stages throughout the decade left NACA in 1955 and 1956. The Committee curtailed compressor research when Lewis, believing no fundamental problems remained in air-breathing engines, turned its attention to nuclear and rocket propulsion.46 Langley’s Jack Erwin and Lewis’s John Klapproth, Karl Kovach, and Lin Wright moved to General Electric. Kovach and Wright joined the company’s axial compressor aerodynamic design group, headed by Richard Novak, where they shifted their primary focus from research on airfoil shapes and parameters to design.

In some respects this timing was opportune. NACA research had produced the compressor design bible and had achieved sufficient success with transonic stages to turn the future over to the engine companies. The decade of research on supersonic compressors, the promising results in the last years notwithstanding, had yet to yield flight-worthy designs, making it hard to argue for continued funding. General Electric proved the beneficiary of the NACA’s change in focus, for GE offered the NACA engineers the chance to apply their experience with advanced, experimental designs to real engines. The knowledge Kovach and Wright brought from the government research establishment into the industry immediately began having an impact on the advanced designs GE was then developing. Wright’s knowledge, in particular, proved crucial to GE’s development of a radically advanced fan that formed the basis of their first flight-worthy turbofan engine, to which we now turn.47