xlr11

This appears to be a Reaction Motors XLR-11 rocket motor. See: en.wikipedia.org/wiki/Reaction_Motors_XLR11

Obviously a great publicity shot of some of the team involved with breaking the sound barrier over Muroc AAF in Oct 1947 in front of Bell X-1 No. 2 (46-063) and the B-29 mother ship. Think then-Captain Chuck Yeager is second from right (kneeling). Wow.

The Bell X-1, designated originally as XS-1, was a joint National Advisory Committee for Aeronautics-U.S. Army Air Forces-U.S. Air Force supersonic research project built by the Bell Aircraft Company. Conceived during 1944 and designed and built during 1945, it achieved a speed of nearly 1,000 miles per hour (1,600 km/h; 870 kn) during 1948. A derivative of this same design, the Bell X-1A, having greater fuel capacity and hence longer rocket burning time, exceeded 1,600 miles per hour (2,600 km/h; 1,400 kn) during 1954. The X-1 was the first manned airplane to exceed the speed of sound in level flight and was the first of the so-called X-planes, a series of American experimental rocket planes designated for testing of new technologies and often kept secret