Walker and Bellman Discuss X-4 Test PointsIn this 1952 photograph NACA test pilot Joe Walker (on left) is seen discussing tests points to be flown on the X-4 aircraft with NACA research engineer Donald Bellman.Read More Facebook Pinterest X LinkedIn Email https://www.nasa.gov/image-detail/walker-bellman-discuss-x-4-test-points/Copy URL to clipboard> DownloadShareSize1041x766px