From introduction: During 1948, the Isotope Research and Production Division undertook to obtain small quantities of nearly pure mercury isotopes by electromagnetic isotope separation. The possible use of a mercury isotope of even-numbered mass to establish an international standard of length required an isotopic purity greater than 99 per cent. It, became apparent that this degree of separation could only be achieved by preventing random diffusion of un-ionized mercury which otherwise would contaminate the isotope collectors.

Report discussing an experiment to reinvestigate the spontaneous fission of 48 (Pu-238) in an effort to determine a more accurate value for the spontaneous fission constant that was found in a previous experiment.

This monthly report details 100 Area technical activities of the Physics Group for the month of August 1949.

Report presenting measured pressure over airfoils at Mach number 1, with subsonic velocities at the nose and supersonic velocities throughout the rear portion, are analyzed by comparison with calculations for similar cases. Results regarding the theoretical basis of approximation, comparison of Prandtl-Meyer flow with measurements, comparison of linear-velocity extrapolation with measurements, and effect of boundary layer upon airfoil pressures are provided.

Report presenting an investigation conducted to determine the effects of increased gas temperatures on the performance of cast Vitallium blades in a turbojet engine. Results regarding the experimental investigation and metallurgical investigation are provided.

In order to provide engineers interested in rotating-wing aircraft, but with no specialized training in stability theory, some understanding of the factors that influence the flying qualities of the helicopter, an explanation is made of both the static stability and the stick-fixed oscillation in hovering and forward flight in terms of fundamental physical quantities. Three significant stability factors -- static stability with angle of attack, static stability with speed, and damping due to a pitching or rolling velocity -- are explained in detail.

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"The recent experiments by Jakob and Erk, on the resistance of flowing water in smooth pipes, which are in good agreement with earlier measurements by Stenton and Pannell, have caused me to change my opinion that the empirical Blasius law (resistance proportional to the 7/4 power of the mean velocity) was applicable up to arbitrarily high Reynolds numbers. According to the new tests the exponent approaches 2 with increasing Reynolds number, where it remains an open question whether or not a specific finite limiting value of the resistance factor lambda is obtained at R = infinity. With the collapse of Blasius' law the requirements which produced the relation that the velocity in the proximity of the wall varied in proportion to the 7th root of the wall distance must also become void" (p. 1).

Report presenting an investigation at a Reynolds number of 6,800,000 to determine the low-speed lateral control characteristics of a 20-percent-chord half-span outboard aileron on a wing with 42 degrees of sweepback at the leading edge. The lateral control, aileron hinge-moment, aileron load, and balance-chamber-pressure characteristics were determined for the wing with and without high-lift and stall-control devices for an angle-of-attack range from -4 degrees through the stall.

Report discussing change in absorptivity of some rare earth elements over time.

A program was initiated to determine the thermal rupture characteristics of KS graphite under steady-state operating conditions simulating the thermal conditions of an uninhibited rocket reactor. The maximum thermal stress calculated using room-temperature properties was 3090 psi. The maximum net specific power obtained was 5.2 Btu/cu in.-sec. (B.O.G.)

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.

This report discussed cadmium coated splines which have been developed to supplement the regular control rod systems under emergency shutdown conditions from higher power levels. The objective of this test was to determine the effectiveness of one such spline placed in a tube in the central zone of a pile, and of two splines in the same tube. In addition, the process control group of the P Division asked that probable spline requirements for safe operation at various power levels be estimated, and the details included in this report. The results of the test indicated a reactivity value of 10.5 {plus_minus} 1.0 ih for a single spline, and 19.0 ih {plus_minus} 1.0 ihfor two splines in tube 1674-B under the loading conditions of 4-27-49, the date of the test. The temperature rise of the cooling water for this tube under these conditions was found to be 37.2{degrees}C for 275 MW operation.

Report presenting pressure distributions of three triangular wing models: a wing-alone model, the same wing combined with a body, and a mock-up of a triangular-wing airplane. Results regarding the separation-vortex air flow over triangular wings, general comments regarding the applicability of the study, chordwise pressure distribution, section lift characteristics, center of pressure, and span load distribution are provided.

This is a progress report of the production reactors on the Hanford Reservation for the month of March 1949. This report takes each division (e.g. manufacturing, medical, accounting, occupational safety, security, reactor operations, etc.) of the site and summarizes its accomplishments and employee relations for that month. (MB)

A low-scale wind-tunnel investigation was conducted in rolling flow to determine the effects of aspect ratio and sweep (when varied independently) on the rolling stability derivatives for a series of untapered wings. The rolling-flow equipment of the Langley stability tunnel was used for the tests. The data of the investigation have been used to develop a method of accounting for the effects of the drag on the yawing moment due to rolling throughout the lift range.

N{sup 12} is shown to have a half life of 12.5 {+-} 1 milliseconds, and a positron upper limit of 16.6 {+-} 0.2 Mev. It is produced by the reaction C{sup 12}(p,n)N{sup 12}, and has a threshold proton energy of 20.0 Mev. This indicates that N{sup 12} is within about 200 Kev of being unstable against proton emission. The mass of N{sup 12} is 12.0228 {+-} 0.00015, and the beta transition is allowed.

Report presenting an investigation of two NACA 6-series airfoils, the NACA 64(sub)1-212 and NACA 65A109 with leading edge slats and split flaps deflected 60 degrees. Information about optimum slat positions, airfoil section lift characteristics, pitching-moment characteristics, and effect of roughness on the lift characteristics was obtained.

From Summary: "This report presents the results of a wind-tunnel investigation conducted to determine the effects of Mach number on the aerodynamic characteristics of a wing of triangular plan form."

Report presenting drag measurements made on a 10-percent-thick wing and 8-percent-thick tail and a 8-percent-thick wing, 6-percent-thick tail version of the X-1 airplane at a variety of Mach numbers. The drag of the thicker wing was found to be much higher than that of the thinner wing. The fuselage was found to cause interference with the wing of both models, making the separation of wing and fuselage drag difficult to determine.

Report presenting a wind-tunnel investigation at a range of Mach numbers with a constant Reynolds number of a semispan model of a thin, unswept wing of aspect ratio 4 and taper ratio 0.5 with a constant-chord aileron and a modified diamond profile. Results regarding lift and rolling-moment characteristics and aileron effectiveness are provided.

"An investigation has been conducted in the Langley 300 MPH 7- by 10-foot tunnel to determine the static stability characteristics at low speeds of complete models with various swept wings so that comparisons might be made with available theoretical and empirical methods of predicting the stability characteristics. Longitudinal and lateral stability characteristics, flaps up and down, were obtained for models having 0 degree, 15 degrees, 30 degrees, and 45 degrees sweptforward and sweptback wings. The results of the investigation indicate that static stability characteristics can be estimated with reasonable accuracy in the low-lift range by means of existing theories" (p. 1).

The results of tests at a Mach number of 1.94 of an ogives-nose cylindrical pitot-static tube and similar tests at Mach numbers of 1.93 and 1.62 of a service pitot-static tube to determine body static pressures and indicated Mach numbers are presented and discussed. The radial pressure distribution on the cylindrical bodies is compared with that calculated by an approximate theory.

"A Westinghouse 24C-2 combustor was investigated at conditions simulating operation of the 24C Jet engine at zero ram over ranges of altitude and engine speed. The investigation was conducted to determine the altitude operational limits, that is, the maximum altitude for various engine speeds at which an average combustor-outlet gas temperature sufficient for operation of the jet engine could be obtained. Information was also obtained regarding the character of the flames, the combustion efficiency, the combustor-outlet gas temperature and velocity distributions, the extent of afterburning, the flow characteristics of the fuel manifolds, the combustor inlet-to-outlet total-pressure drop, and the durability of the combustor basket" (p. 1).