Report in two parts: one examines the boundary conditions for an open wind tunnel with special references to the effects of the closed entrance and exit sections, while the other derives solutions of four types of two-dimensional open tunnels, including one in which the pressures on the two free surfaces are not equal.

From Summary: "By the use of a form of the Prandtl-Glauert method that is valid for three-dimensional flow problems, the value of the maximum incremental velocity for compressible flow about thin ellipsoids at zero angle of attack is calculated as a function of the Mach number for various aspect ratios and thickness ratios. The critical Mach numbers (within the accuracy of the Prandtl-Glauert method) of the various ellipsoids are also determined. The results indicate an increase in critical Mach number with decrease in aspect ratio which is large enough to explain experimental results on low-aspect-ratio wings at zero lift."

Report presenting an analysis of the effects of compressibility on the pressure coefficients of several bodies of revolution by comparing experimentally determined pressure coefficients with corresponding pressure coefficients calculated by the use of linearized equations of compressible flow. The results indicated that the theoretical methods predict the subsonic pressure-coefficient changes over the central portion of the body but do not predict the pressure-coefficient changes near the nose.

Report issued by the Bureau of Mines over a large chromite deposit on Casper Mountain. Description of the deposit is listed. This report includes tables, maps, and illustrations.

Report issued by the Argonne National Laboratory discussing the progress and work completed between February and April, 1949. Descriptions of the studies conducted and progress made are presented. This report includes tables, illustrations, and photographs.

"A study of the subsonic flow past an infinitely long corrugated circular cylinder is presented to show the relation between two-dimensional and axisymmetrical flow. In fact, a solution is obtained which contains as limiting cases both the Prandtl-Glauert correction for two-dimensional flow and the Göthert correction for flow past slender bodies of revolution. Included in the paper are velocity-correction formulas for a cylinder with a single bump and for a corrugated cylinder in the presence of walls" (p. 1).

"A flight test of the Aero jet Engineering Corporation's 7KS-6000 T-27 Jato rocket motor was conducted at the Langley Pilotless Aircraft Research Station at Wallops Island, Va, to determine the flight performance characteristics of the motor. The flight test imposed an absolute longitudinal acceleration of 9.8 g upon the rocket motor at 2.8 seconds after launching. The total impulse developed by the motor was 43,400 pound-seconds, and the thrusting time was 7.58 seconds" (p. 1).

Report presenting the results of flight tests showing lateral oscillation in the Bell X-1 and calculations created to determine the effects of changes in several mass and aerodynamic parameters on the lateral oscillations. Calculations indicate that lateral stability should be improved by a more positive inclination of the principal axis of inertia or a reduction of the value of yawing moment of inertia.

"Methods are presented that use general correlative time-response input and output data for a linear system to determine the frequency-response function of that system. These methods give an exact description of any linear system for which such transient data are available. Examples are shown of application of a method to both an underdamped and a critically damped exact second-order system, and to an exact first-order system with and without dead time. Experimental data for a turbine-propeller engine showing the response of engine speed to change in propeller-blade angle are presented and analyzed" (p. 547).

Report presenting testing of low-aspect-ratio triangular-plan-form lifting surfaces located on conical and cylindrical portions of a body have been determined at Mach number 1.2 and several subsonic speeds to determine if the aerodynamic characteristics of these surfaces at supersonic speeds could be improved by locating them in the subsonic conical-flow field. Results regarding lift and drag coefficients and lift-curve slopes are provided.

"A general algebraic method of attack on the problem of controlling gas-turbine engines having any number of independent variables was utilized employing operational functions to describe the assumed linear characteristics for the engine, the control, and the other units in the system. Matrices were used to describe the various units of the system, to form a combined system showing all effects, and to form a single condensed matrix showing the principal effects. This method directly led to the conditions on the control system for noninteraction so that any setting disturbance would affect only its corresponding controlled variable" (p. 581).

Report presenting an investigation of the characteristics of a low-aspect-ratio wing at high subsonic Mach numbers in the high-speed tunnel. The wing model had an NACA 65-108 airfoil section, an aspect ratio of 4.01, a taper ratio of 0.498, and no twist or dihedral. Results regarding normal-force characteristics, pitching-moment characteristics, and drag characteristics are provided.

Memorandum presenting an investigation to determine the automatic lateral stability characteristics of a model equipped with a gyro stabilizing unit that gave response to bank and yaw. Stable flights were obtained with the flicker-type automatic control, and the amplitude of the oscillations was decreased by adding the attachment which provided hunting control.

"Flight tests were conducted at the NACA Pilotless Aircraft Research Station, Wallops Island, to determine the characteristics of the Allegany Ballistics Laboratory's 6.2inch-diameter Deacon and 10-inch-scale model solid-propellant rocket motors. The tests were performed to assist in the development of these rockets which were designed for, and urgently needed to propel supersonic research models and pilotless aircraft. The tests showed that the rocket motors functioned properly under various flight- acceleration loads over a range of pre-ignition grain temperatures" (p. 1).