World's First Variable Density Wind Tunnel¹ (1923)
The historic NACA² Langley Laboratory's VDT was a 77.3 t pressure tank rated at 20 atmospheres, 10.5 m long, 4.6 m in diameter, and 54 mm thick. It had a closed-circuit design with an annular return flow powered by a fan attached to a 184 kW motor producing air speeds up to 82 km/h. Before 1923, atmospheric pressure wind tunnels³ only gave valid results for full scale models of aircraft parts, experimental results obtained using scale models in these tunnels were open to question because a special parameter called the Reynolds number⁴ did not match those encountered in the actual flights. The Reynolds number of a 1/20-scale model would be too low by a factor of 20 as shown by Osborne Reynolds in his classic 1883 experiment and since this number is used to predict the transition from laminar flow⁵ to turbulent flow⁶, radically different airflow conditions will occur between model and full-sized aircraft. Since the Reynolds number is proportional to air density, a wind tunnel has to be pressurized to 20 atmospheres when using a 1/20-scale model for more accurate testing. Simulating higher altitudes is then a simple matter of pressurizing at less than 20 atmospheres. The VDT at the National Advisory Committee for Aeronautics had a unique high-Reynolds number capability and was used to design the Douglas DC-3, the Boeing B-17 Flying Fortress, and even the 713 km/h Lockheed P-38 Lightning!
The Orthomat was a solid-state numerically controlled engineering drafting machine made by Universal Drafting Machine Company from Cleveland Ohio (1963). It automatically translated complex mathematical formulas defined on punched or magnetic tape into accurate engineering drawings at speeds up to 85 mm/s, designed to operate as a part of a total computer engineering system, correlating with other numerically controlled data, production and inspection machines or standalone. The device is a coordinate, continuous-line contouring plotter, capable of drawing straight lines, angles, curves, circles or ellipses on paper up to 152×366 cm. It has an automatic indexing hex turret for mounting a variety of stylii. Controls permit scaling of drawings (¼, ½, full, 2×) and "mirror image". The numerical control director supplies command pulses and may be any manual or tape (punched or magnetic) input device which can supply incremental X & Y pulses of 0.0254 mm (1 mil) value at a controlled rate, plus auxiliary signals to control the stylii. The drafting machine controls all motions of a variety of scribing devices and consists of an aluminum table with desktop linoleum surface, a vacuum chuck, and a large scale digital X-Y plotter using a a precision rack and pinion drive. Controls govern X, Y and Z motion, jogging, stepping in 0.0254 mm increments, feedrate override of speed, stylus indexing, an dash-line generation. Actual position is readout for any two of X,Y and Z axes to the nearest 0.0254 mm. Zero positioning is automatic, and readouts may be reset to zero anywhere on the board to accommodate dimensioning of drawings in which the 0-0 position is off the table. A maintenance feature includes a built-in customer engineer's test panel for quick pinpointing of any malfunction.
Apollo 11. Space
Date: July 1969
Photos ID: AS11-36-5389, AS11-36-5391 and AS11-36-5392
Color Film Scan. Balanced.
Pilot Edwin E. Aldrin is inside the Lunar Module during the Moon Trip.
Photo Credit: NASA. JSC.
Panorama, illumination adjustment, and compensation balance for red and green: