The Douglas El Segundo Division Project 9 was a study for a twin engine tailless bomber dating from 1938. It was likely designed (or heavily influenced) by Jack Northrop, who would leave Douglas the following year to form his own independent company. The report presented in the gallery above describes the results of wind tunnel tests on an 8% scale model of the bomber. The experiments were made in the closed working section of the 10 ft wind tunnel of the Guggenheim Aeronautics Laboratory at the California Institute of Technology (GALCIT). Most of the tests were made at a wind speed of about 176 mph, corresponding to a Reynolds Number based on mean wing chord of approximately 1,600,000. A few measurements were made at other wind speeds to investigate scale effects. The critical Reynolds Number at which a 15 cm sphere had a drag coefficient of .3 was about 325,000, indicating a wind stream with very low turbulence. The entire model was lacquered and rubbed down to a high polish.
During the course of investigations, many modifications were made, such as the addition of a large central vertical fin; evaluation of engine nacelles with two different profiles; and evaluation of three different duct shapes, among others. Photos of the model in various configurations are shown above. An artist’s impression showing such details as the glazing and armament intended for the Douglas Project 9 can be found on the Secret Projects Forum.
The Douglas Project 9 never went further than the wind tunnel stage, with the company developing more conventional types such as the A-20 and A-26 during WW II. Northrop would, of course, go on to build the XB-35/YB-49 flying wing heavy bombers, the latter being cancelled and scrapped in 1950 due to a combination of technical and political factors.
All images from NARA Archives II, College Park, MD, RG 18