Report presenting aerodynamic and icing investigations conducted in the icing research tunnel on a model of a turbojet-engine nacelle with a long straight air inlet in order to provide basic design criteria for hot-gas blowback systems. The most uniform temperature distribution was obtained with a bleedback of 4.4 percent at a gas temperature of 1000 degrees Fahrenheit and resulted in an average dry-air-temperature rise of 46 degrees Fahrenheit.

Report presenting the results of several investigations of the performance of different types of clamshell variable-area exhaust nozzle far turbojet engines to determine the efficiency of that type of exhaust nozzle as compared with conventional fixed-area conical exhaust nozzles. The investigations were conducted at zero-ram sea level conditions on three different full-scale turbojet engines and using five different nozzles.

Report presenting an investigation to determine the longitudinal stability characteristics of a complete model equipped with a variable-sweep wing at four different angles of sweepback. The primary objective was to study various wing modifications and an external-flap arrangement designed to minimize the shift in neutral point accompanying the change in sweep angle.

A report on high voltage pulse transformer designs at the University of California Radiation Laboratory.

Report presenting an investigation to evaluate the effects of split flaps, elevons, sharp leading edges, drooped-nose flaps, and extended-nose flaps on the lift, drag, and pitching-moment characteristics at low speed of a wing-fuselage combination with a wing with the leading edge swept back 63 degrees and an aspect ratio of 3.5. Results regarding the plain wing and wing-fuselage combinations, Reynolds number, split flaps, elevons, leading-edge devices, and highest lift coefficient attained before longitudinal instability are provided.

The operation of the 184" synchro-cyclotron is reviewed in terms of the theory as developed by the authors. Certain relevant data on the properties of the magnet and rotating condenser are also presented.

Report presenting the results of an analytical investigation, which demonstrated that the inlet of a turbojet engine can be protected from ice accretions by bleeding hot gases from other locations within the engine to the inlet without undue loss in thrust. Results regarding the bleedback requirements, engine performance, effect of nozzle area, mixing efficiency, and seriousness of thrust losses are provided.

Report discussing the progress made on a research project for the preparation of ductile zirconium during April 1949.

Report presenting an investigation of the damping-in-roll characteristics of a 35 degree sweptback wing, with and without vertical fins, through a range of Mach numbers in the high speed 7- by 10-foot tunnel utilizing a free-to-roll technique. The damping-in-roll coefficient increased in magnitude with Mach number in the manner indicated by theory and generally was found to increase in magnitude with angle of attack over the range tested.

A lightweight instrument that utilizes resistance-wire electric strain gases to measure propeller-shaft thrust has been developed. A wind-tunnel investigation on a propeller installed, on a single-engine pursuit airplane showed that the instrument gave a reliable indication of propeller-shaft thrust to an accuracy of +/-2 percent within its calibrated range. No attempt was made to determine the relation of indicated shaft thrust to net propeller thrust.

Report presenting the specific impulse of liquid diborane and liquid oxygen over a range of mixture ratios in a 100-pound-thrust rocket engine operating at a combustion-chamber pressure of 300 pounds per square inch absolute. A faired curve through the experimental data had approximately the same shape as the theoretical curve.

This report analyzes Parian and Teflon that were exposed to solutions of 1AX, 1AS, and 1AF, ANL June 1, 1948 Flowsheet, under conditions described in the following report.

Testing was performed at Mach number 1.53 with a wing-fuselage combination with a wing with 63 degrees leading-edge sweep, an aspect ratio of 3.46, and a taper ratio of 0.25. The wing had an NACA 64A005 thickness distribution parallel to the plane of symmetry and was cambered and twisted. Results regarding the comparison of lift, drag, and pitching-moment characteristics of WF-63c and WF-63, effects of sweep, and effects of Reynolds number are provided.

"Pressure-distribution data of the NACA 64(sub 1)-012 and 64(sub 1)A012 airfoils have been analyzed to determine the effects of increasing the trailing-edge angle from 9 to 14 degrees. The primary effect of increasing the trailing-edge angle was to decrease the loading over the rear portion of the airfoil under lifting conditions. The differences in trailing-edge load increased with Mach number and lift coefficient" (p. 1).

"An investigation has been conducted in the Langley 20-foot free-spinning tunnel of a 1/29-scale model of the Republic XF-91 airplane with a.conventional-tail arrangement installed. Previously, tests were made on the model with a vee tail installed. The erect spin and recovery characteristics of the model were determined for the normal loading with the wing installed at various amounts of incidence. The spin investigation also included inverted-spin tests, spin-recovery-parachute tests, tests with the center of gravity moved rearward, and tests with external fuel tanks added to the model" (p. 1).

An altitude-wind-tunnel investigation of the performance of AN-F-58 and AN-F-32 fuels in an experimental turbojet engine was conducted over a range of simulated altitudes and flight Mach numbers. Combustion efficiencies obtained with AN-F-58 and AN-F-32 fuels were approximately equal. The minimum-speed altitude operational limit was essentially the same with either AN-F-58 or AN-F-32 fuel. Starting characteristics of the two fuels were approximately the same at low wind milling speeds. Visual observation showed no apparent differences in the carbon-deposition rates of AN-F-58 and AN-F-32 fuels.

Memorandum presenting an approximate method for the estimation of the properties of the incompressible laminar boundary layer on a flat plate in the slip-flow region using Karman's momentum method. At equivalent stations, the total thickness and the skin friction of a slipping boundary layer are less than that of the normal boundary layer at the same Reynolds number.

Note presenting an investigation to determine the fatigue-strength values for 24S-T aluminum alloy when subjected to various ratios of biaxial stresses. The stresses considered were both tensile. The results indicated that uniaxial fatigue-strength values in the longitudinal direction cannot be used to predict the fatigue strength, and that biaxial fatigue strength may be as low as 50 percent of the uniaxial fatigue strength.

Report presenting an investigation of pitching moments and center-of-pressure locations obtained from a landing investigation in smooth water of a conventional flying boat as compared to values predicted by general hydrodynamic impact theory. Landings were generally moderate and covered as wide a range of trim and velocities as practical. Results regarding the center of pressure and pitching moments are provided.

Note presenting a theoretical solution for the problem of the compressive buckling of flat rectangular Metalite type sandwich plates with simply supported loaded edges and clamped unloaded edges. The solution is based on the general small-deflection theory for flat sandwich plates developed in a previous report. Results regarding stability orientation and buckling curves, comparison with approximate solution, correction for plasticity, and comparison of theory and experiment are provided.

"A theoretical solution is presented for the critical axial-compressive stress of a simply supported curved rectangular panel having a central longitudinal stiffener offering no torsional restraint. The results are presented in the form of computed curves and tables. Because a panel of moderate or large curvature buckles in compression at a stress lower than the theoretical value, a method is suggested to aid in determining the critical stress for use in design" (p. 1).

Report presenting a study of the factors involved in the design of total-temperature probes for use at supersonic speeds as applied to the design of an instrument to be used in wind-tunnel calibrations. Tests of the probe showed that the calibration factor required in the conversion of the measured temperature to the true total temperature was 0.992 for a range of Mach numbers.

The problem of the motion of an elongated body of revolution in an incompressible fluid may, as is known, be solved approximately with the aid of the distribution of sources along the axis of the body. In determining the velocity field, the question of whether the body moves uniformly or with an acceleration is no factor in the problem. The presence of acceleration must be taken into account in determining the pressures acting on the body. The resistance of the body arising from the accelerated motion may be computed either directly on the basis of these pressures or with the aid of the so-called associated masses (inertia coefficients). A different condition holds in the case of the motion of bodies in a compressible gas. In this case the finite velocity of sound must be taken into account.

"For a certain Mach number of the oncoming flow, the local velocity first reaches the value of the local velocity of sound (M = 1) at some point on the surface of the body located within the flow. This Mach number is designated the critical Mach number M(sub cr). By increasing the flow velocity, a supersonic local region is formed bounded by the body contour and the line of transition from subsonic to supersonic velocity. As is shown by observations with the Toepler apparatus, at a certain flow Mach number M > M(sub cr) a shock wave is formed near the body that closes the local supersonic region from behind" (p. 1).