A reproduction of the technical papers presented by staff members of the NACA Laboratories at the NACA Conference on High-Speed Aerodynamics at the Ames Aeronautical Laboratory during March 18-20, 1958. The primary purpose of the conference was to convey to military services and contractors the results of recent research and to provide an opportunity to discuss the results.

"This document contains reproductions of technical papers on some of the most recent research results on aircraft loads, flutter, and structures from the NACA laboratories. These papers were presented by members of the staff of the NACA laboratories at the Conference held at the Langley Aeronautical Laboratory March 5, 6, and 7, 1957. The primary purpose of this Conference was to convey to contractors of the military services and others concerned with the design of aircraft these recent research results and to provide those attending an opportunity to discuss the results" (p. 6).

Report presenting the results of an investigation to determine the static longitudinal and lateral stability and control characteristics of a model of the Republic MX-1554 airplane at a specified Mach and Reynolds number. No analysis was provided in the paper in order to expedite publication.

Report presenting an investigation of problems related to helicopters. Also included are the history of the evolution of the helicopter and a series of propeller experiments.

Memorandum presenting the application of the nuclear-reactor simulator to an investigation of the validity of the customary assumption of uniform distributions of fuel burnup and fission-product poisoning in a reactor core. The two-group calculation results show the effects of the approximation on the reactivity, power distribution, and xenon-135 distribution for a specific power reactor in which the initial power density varied by a factor of approximately 4 over the core volume.

Memorandum presenting a supersonic wind-tunnel investigation of the origin and distribution of store interference in the 4- by 4-foot supersonic pressure tunnel at Mach number 1.6 in which separate forces on a store, a fuselage, a swept wing, and a swept-wing-fuselage combination were measured. The store was separately sting-mounted on its own six-component internal balance and was traversed through a wide systematic range of spanwise, chordwise, and vertical positions.

Performance of experimental annular turbojet combustors at simulated high altitude supersonic flight conditions.

Memorandum presenting a supersonic wind-tunnel investigation of the origin and distribution of store interference performed in the 4- by 4-foot supersonic pressure tunnel at Mach number 1.61 in which separate forces on a store, a fuselage, a swept wing, and a swept-wing-fuselage combination were measured. The report presents data on a configuration which simulated a heavy-bomber airplane with stores of several shapes and sizes.

"Comparisons are made of experimental and theoretical zero-lift wave drag for several nose shapes, wing-body combinations, and models of current airplanes at Mach numbers up to 1.0. The experimental data were obtained from tests in the Ames 6- by 6-foot supersonic wind tunnel and at the NACA Wallops Island facility. The theoretical drag was found by use of linear theory utilizing model area distributions" (p. 1).

"The thermal conductivity of low-density ice has been computed from data obtained in an experimental investigation of the heat transfer and mass transfer by sublimation for an iced surface on a flat plate in a high-velocity tangential air stream. The results are compared with data from several sources on the thermal conductivity of packed snow and solid glaze ice. The results show good agreement with the equations for the thermal conductivity of packed snow as a function of snow density. The agreement of the curves for packed snow near the solid ice regime with the values of thermal conductivity, of ice indicates that the curves are applicable over the entire-ice-density range" (p. 1).

From Summary: "An investigation has been conducted in the NACA Cleveland icing research tunnel to determine the aerodynamic and icing characteristics of several recessed fuel-vent configurations. The vents were investigated aerodynamically to obtain vent-tube pressures and pressure distributions on the ramp surface as functions of tunnel-air velocity and angle of attack. Icing investigations were made to determine the vent-tube pressure losses for several icing conditions at tunnel-air velocities ranging from 220 to 440 feet per second. In general, under nonicing conditions, the configurations with diverging ramp walls maintained, vent-tube pressures greater than the required marginal value of 2 inches of water positive pressure differential between the fuel cell and the compartment containing the fuel cell for a range of angles of attack from 0 to 14deg at a tunnel-air velocity of approximately 240 feet per second."

Memorandum presenting a preliminary evaluation of three types of combustor configuration in a 48-inch-diameter ramjet engine in order to select the one with the greatest promise of efficient and stable combustion at low fuel-air ratios and low combustor-inlet pressures. Results regarding the inlet conditions, performance, and a comparison of the configurations are provided.

Report presenting a full-scale, free-jet investigation to determine the performance of a side-inlet supersonic diffuser designed for a flight Mach number of 2.75. Several internal modifications made to improve diffuser-outlet flow uniformity were also evaluated. Results regarding the general characteristics of the diffuser and effect of diffuser modifications on flow distribution are provided.

Report presenting a flight investigation made at high speeds to determine the profile drag of a P-47D airplane wing with production surfaces covered with camouflage paint. The results indicated that a minimum profile-drag coefficient of 0.0097 was attained for lift coefficients from 0.16 to 0.25 at Mach numbers less than 0.67.

Report presenting an investigation of three cone-cylinder bodies to obtain boundary-layer-transition data at very low ratios of wall to local stream temperature. Surface finishes at several levels of roughness height were tested. Results regarding the smooth body and rough bodies are provided.

From Summary: "The effects of primary and runback ice formations on the section drag of a 36 deg swept NACA 63A-009 airfoil section with a partial-span leading-edge slat were studied over a range of angles of attack from 2 to 8 deg and airspeeds up to 260 miles per hour for icing conditions with liquid-water contents ranging from 0.39 to 1.23 grams per cubic meter and datum air temperatures from 10 to 25 F. The results with slat retracted showed that glaze-ice formations caused large and rapid increases in section drag coefficient and that the rate of change in section drag coefficient for the swept 63A-009 airfoil was about 2-1 times that for an unswept 651-212 airfoil. Removal of the primary ice formations by cyclic de-icing caused the drag to return almost to the bare-airfoil drag value. A comprehensive study of the slat icing and de-icing characteristics was prevented by limitations of the heating system and wake interference caused by the slat tracks and hot-gas supply duct to the slat. In general, the studies showed that icing on a thin swept airfoil will result in more detrimental aerodynamic characteristics than on a thick unswept airfoil."

Report discussing an investigation to determine the effect of spin on the aerodynamic characteristics of the Army Ordnance Corps 60-millimeter T-24 mortar shell with several tail-fin configurations. Tests were performed at several airspeeds, speeds of rotation, and angles of attack. Under all test conditions, the models were statistically stable and the yawing moment increased with speed of rotation at higher angles of attack.

Note presenting an evaluation of the rotating method for the measurement of droplet-size distribution, volume-median droplet size, and liquid-water content in clouds, which showed that small uncertainties in basic data eliminate the distinction between cloud droplet-size distributions and are a source of large errors in the determination of the droplet size. Matching curves for obtaining droplet-size distribution, volume-median droplet size, and liquid-water content from flight data were computed from the results of the droplet-trajectory calculations.

Note presenting the computation of the trajectories of water droplets in a compressible-air flow field around a cylinder using a mechanical analog. The results of the calculations at approximately the flight critical Mach number were compared with calculations of trajectories in an incompressible flow field. Results regarding the extension of cylinder results to airfoils are provided.

"The presence of radomes and instruments that are sensitive to water films or ice formations in the nose section of all-weather aircraft and missiles necessitates a knowledge of the droplet impingement characteristics of bodies of revolution. Because it is possible to approximate many of these bodies with an ellipsoid of revolution, droplet trajectories about an ellipsoid of revolution with a fineness ratio of 5 were computed for incompressible axisymmetric air flow. From the computed droplet trajectories, the following impingement characteristics of the ellipsoid surface were obtained and are presented in terms of dimensionless parameters: (1) total rate of water impingement, (2) extent of droplet impingement zone, (3) distribution of impinging water, and (4) local rate of water impingement" (p. 1).

"An experimental investigation was conducted in a 3.84- by 10-inch tunnel to determine the mass transfer by sublimation, heat transfer, and skin friction for an iced surface on a flat plate for Mach numbers of 0.4, 0.6, and 0.8 and pressure altitudes to 30,000 feet. Measurements of rates of sublimation were also made for a Mach number of 1.3 at a pressure altitude of 30,000 feet. The results show that the parameters of sublimation and heat transfer were 40 to 50 percent greater for an iced surface than was the bare-plate heat-transfer parameter" (p. 1).

"A principle formerly used in an instrument for cloud detection was further investigated to provide a simple and rapid means for measuring the liquid-water content of clouds at temperatures above and below freezing. The instrument consists of a small cylindrical element so operated at high surface temperatures that the impingement of cloud droplets creates a significant drop in the surface temperature. The instrument is sensitive to a wide range of liquid-water content and was calibrated at one set of fixed conditions against rotating multicylinder measurements. The limited conditions of the calibration Included an air temperature of 20 F, an air velocity of 175 miles per hour, and a surface temperature in clear air of 475 F" (p. 1).

"The effects of existing frictional heating were analyzed to determine the conditions under which ice formations on aircraft surfaces can be prevented. A method is presented for rapidly determining by means of charts the combination of-Mach number, altitude, and stream temperature which will maintain an ice-free surface in an icing cloud. The method can be applied to both subsonic and supersonic flow. The charts presented are for Mach numbers up to 1.8 and pressure altitudes from sea level to 45,000 feet" (p. 1).

"Liquid-water content, droplet size, and temperature data measured during 22 flights in predominately stratiform clouds through the 1948-49 and the 1949-50 winters are presented. Several icing encounters were of greater severity than those previously measured over the same geographical area, but were within the limits of similar measurements obtained over different terrain within the United States. An analysis of meteorological conditions existing during the 74 flights conducted for four winters indicated an inverse relation of liquid-water concentration to maximum horizontal extent of icing clouds" (p. 1).