Abstract. The diffusion length of thermal neutrons in water as a function of the water temperature has been measured. The results are expressed as a linear relation: L = 2.644 + 0.0061T where L is the diffusion length in centimeters and T is the temperature in degrees centigrade.

Abstract. Given the maximum intrinsic curvature of a rod, the maximum force required to confine it between parallel rigid walls is computed.

Maximum curvatures and forces set up in taking a rod in a tube are considered.

Technical report. The extent of the Wigner effect in graphite at any point in a pile is sensitive to the local structural situation. It is greater near a slug. These control experiments give information on changes in graphite to be expected in selected places in the pile.

Report on stability and control tests of the Bell P-63 series airplanes. Information about the spin characteristics, lateral control characteristics, longitudinal stability and control characteristics and directional stability and control characteristics is provided. A chronology of testing and detailed description of the airplane and its modifications are also provided.

This technical report discusses a method proposed to measure neutron energies by accurately determining the momenta of recoil protons in a magnetic spectrometer specially designed for this purpose. The main consideration in the design of the spectrometer is the shielding of the detector from the high radiation background associated with intense neutron beams.

"Detail calculations are presented of the shifts in stick-fixed neutral point of the Republic XF-12 airplane due to the windmilling propellers and to the fuselage. The results of these calculations differ somewhat from those previously made for this airplane by Republic Aviation Corporation personnel under the direction of Langley flight division personnel. Due to these differences the neutral point for the airplane is predicted to be 37.8 percent mean aerodynamic chord, instead of 40.8 percent mean aerodynamic chord as previously reported" (p. 1).

"The importance of the stick force per unit normal acceleration as a criterion of longitudinal stability and the critical dependence of this gradient on elevator hinge-moment parameters have been shown in previous reports. The present report continues the investigation with special reference to transient effects for maneuvers of short duration" (p. 449).

"Simple and exact expressions are given for the efficiency of single and dual rotating propellers with ideal circulation distribution as given by the Goldstein functions for single-rotating propellers and by the new functions for dual-rotating propellers from part I of the present series. The efficiency is shown to depend primarily on a defined load factor and, to a very small extent, on an axial loss factor. Tables and charts are included for practical use of the results. The present paper is the fourth in a series on the theory of propellers" (p. 99).

Abstract. Slow neutron transmission measurements as a function of the time of flight of the incident neutron have been made for three different thicknesses of Beryllium. The energy region from 0.004 eV to 50 eV was investigated using the Columbia neutron beam spectrometer system. Particular emphasis was placed on the very low energy region (from 0.004 eV tp 0/2 eV or from 0.6 to 5 [length]) where pronounced crystal interference effects were observed. The effective slow neutron cross section (in the unity of X 10(-24)ce(2)atom) for several different energy values were: 6.1 at 0.2 [length], 3.5 at 1.5 [length], 2.3 at 2.5 [length] and 0.6 at 4.6 [length]. The positions of the discontinuities in the cross section agree fairly well with the values obtained from the X-ray measurements.

From introduction: "The measurement of the thermal conductivity of liquid TF6 presented unusual difficulties because of two of its properties which necessitated working with a closed system. The properties were (1) the liquid can exist as such only above 64.05°C. at which temperature its saturated vapor pressure is 1140 mm. of mercury, and (2) the compound reacts rapidly with moist air. Also because of the liquid's extremely corrosive nature, it was necessary to design a cell of special corrosion resistant materials."

The problem of lining a hollow aluminum sphere, 10 inches i.d., with lunes of heavy metal foil, was assigned to this group by Dr. E. Creutz. The work was carried out under the direct supervision of Dr. D.H. Gurinsky. the problem was divided naturally into tow parts: first, forming fitting the lunes, and second, cementing hem to the inside of the sphere.

Abstract. Temperatures are measured at two points in an internally heated jacketed slug which is cooled by water flowing in an off-center annulus around the slug. The variations of these temperatures with water velocity, water temperature, power, and the amount the annulus is off center are measured. The temperature near the slug surface which approaches and comes in contact with the water jacket does not increase as much as anticipated. The temperature near the slug surface on the side which is moved away from the water jacket increases nearly as much as on the side approaching the slug. An explanation for this unexpected increase of temperature as on side moving away from the jacket is given.

The following report describes and foretells the situation in medium in which neutrons are being (a)produced as fast neutrons, (b) slowed down to thermal speeds by impacts with nuclei, and (c) absorbed by nuclei in such a manner that sometimes fresh fast neutrons appear at the place where a thermal neutron has just appeared.

Report presenting equations for calculating the stick-force characteristics obtained with a spring-tab type of elevator control. The main problems encountered in the design of the satisfactory elevator spring tab are to provide stick forces in the desired range, to maintain the force per g sufficiently constant throughout the speed range, to avoid undesirable "feel" of the control in ground handling, and to prevent flutter.

Report presenting a survey of the technical information contained in the literature on the subject of lubrication, friction, and wear of aircraft engine piston rings.

"An analysis is made to simplify pressure-drop calculations for nonadiabatic and adiabatic friction flow of air in smooth cylindrical tubes when the density changes due to heat transfer and pressure drop are appreciable. Solutions of the equation of motion are obtained by the use of Reynolds' analogy between heat transfer and skin friction. Charts of the solutions are presented for making pressure-drop calculations" (p. 1).

From Summary: "Local-instability tests of 24S-T aluminum-alloy formed Z- and channel-section columns were made in order to determine a length of test specimen that would avoid the increased strength associated with short lengths and also permit the occurrence of a convenient buckling pattern. The effect of column length on the critical compressive stress, on the average stress at maximum load, and on the number of half-waves of the buckling pattern is shown."

Report presenting testing to determine the best way to land the B-25 airplane in calm and rough water and to determine its probable ditching performance. By landing with flaps down in a tail-down attitude at as slow a speed as possible, smooth straight landing runs will probably result in calm water. Results regarding the effect of attitude, effect of flap setting, effect of simulated damage, effect of propellers, and effect of seaway are provided.

Report presenting the application of transient theory to the rational determination of dynamic loads on airplane structures during initial landing impact. Simplified procedures are described by which the distribution of the maximum attainable value of the dynamic stresses in the structure may be obtained.

Report discussing the knock-limited performance of blends of triptane and 28-R fuel in an F-4 engine at three sets of conditions and three compression ratios. The knock limits of the triptane blends were more sensitive to compression ratio than the 28-R fuel, and the sensitivities of the blends increased as the severity of other engine conditions increased.

Report presenting an investigation made on a supercharged CFR engine to determine a method for estimating lead susceptibilities of pure or blended paraffinic fuels. As a result of these studies, a chart consisting of a series of straight lines passing through the origin was developed to represent the lead susceptibilities of pure and blended paraffinic fuels in terms of knock-limited indicated mean effective pressures and octane numbers.

Report presenting an investigation of the relation between the knock limit and the blend composition of aviation fuels when tested under supercharged conditions in an air-cooled aircraft-engine cylinder. Results regarding the blending characteristics of two gasolines, paraffinic fuels, olefinic fuel, naphthenic fuel, aromatic fuels, when xylidines are present in the fuel components, and fuel components containing unequal concentrations of tetraethyl lead are provided.

Report presenting flight tests to determine the longitudinal stability characteristics of a pursuit airplane when flown with and without an experimental bellows-type bob weight. When the weight was installed, the stick-free static stability remained approximately constant irrespective of the shift in center of gravity resulting from a change in fuel quantity in the auxiliary fuselage fuel tank. Although the weight functioned satisfactorily, the performance could have been enhanced by the reduction of the friction in the mechanism.