Report on the Bombing of Our Own Troops during Operation “Tractable”: 14 August 1944

Editor’s Note: Operation “Tractable“ was the second major Canadian operation in Normandy designed to break through the German defensive perimeter to reach Falaise. Like its predecessor, Operation “Totalize,“ “Tractable“ was to employ heavy bombers to augment the firepower available to the troops. The use of heavy bombers in a tactical role was a relatively new tasking for the strategic force and required precise targetting to destroy and disrupt enemy positions. The strategic bomber force, British and American, had made significant contributions to the land battle in Normandy, but there had been mistakes, most notably during Operation “Cobra” when the American 8th Air Force had twice bombed their own troops on 24–25 July causing 136 deaths and an additional 621 casualties. For Operation “Tractable,” the medium bombers of 2 Group, 2nd Tactical Air Force were to bomb German gun, mortar and tank positions along the startline immediately prior to H-Hour. This was to be followed by a large attack by Bomber Command hours after the start of the advance. This bombing was intended “to destroy or neutralize enemy guns, harbours, and defended lacalities on the right flank and to prevent any enemy movement from this area to the area of attack.” (First Canadian Army Op Instruction No. 14, August 1944). Though the air support was largely a success, a number of aircraft mistakenly bombed short hitting units of First Canadian Army. In total, over 150 Allied soldiers were killed and 241 wounded by the short bombing. Though it had little impact on the outcome of “Tractable,” there were a number of investigations launched to understand why the short bombing occurred. The report which follows, dated 25 August 1944 and written by Air Chief Marshal Arthur Harris, Air Officer Commanding-in-Chief of Bomber Command, contains the official RAF post–mortem on the reasons for the accidental bombing of First Canadian Army

Narrative of Chain cruise #17, phase I : St. George, Bermuda, to Freetown, Sierra Leone, 19 February - 22 March 1961

The journal of a cruise of R/V CHAIN from Bermuda to Freetown, Sierra Leone during February and March, 1961, is the basis of this report. Location of observations are given. The portion of the Mid- Atlantic Ridge lying along the equator was surveyed from 10° to 19°W, and new information concerning the slope and orientation of rift zones was obtained. A detailed bathymetric survey of the Romanche Trench was made. A continuous temperature-depth profile, from the surface to 100 meters, was made along the ship 's track with a thermistor chain. Surface shear was measured with pitotmeters mounted on the chain (surface water velocity relative to the water velocity at the depth of the pitotmeter), to determine the strength and direction of the equatorial undercurrent.The Office of Naval Research under Contract Nonr-, 2196 (00

Noise Correlation in Cosmic Microwave Background Experiments

Many analyses of microwave background experiments neglect the correlation of noise in different frequency or polarization channels. We show that these correlations, should they be present, can lead to severe misinterpretation of an experiment. In particular, correlated noise arising from either electronics or atmosphere may mimic a cosmic signal. We quantify how the likelihood function for a given experiment varies with noise correlation, using both simple analytic models and actual data. For a typical microwave background anisotropy experiment, noise correlations at the level of 1\% of the overall noise can seriously {\it reduce} the significance of a given detection.Comment: Analysis generalized; conclusions unaltere

Theory of optimum shapes in free-surface flows. Part 1. Optimum profile of sprayless planing surface

This paper attempts to determine the optimum profile of a two-dimensional plate that produces the maximum hydrodynamic lift while planing on a water surface, under the condition of no spray formation and no gravitational effect, the latter assumption serving as a good approximation for operations at large Froude numbers. The lift of the sprayless planing surface is maximized under the isoperimetric constraints of fixed chord length and fixed wetted arc-length of the plate. Consideration of the extremization yields, as the Euler equation, a pair of coupled nonlinear singular integral equations of the Cauchy type. These equations are subsequently linearized to facilitate further analysis. The analytical solution of the linearized problem has a branch-type singularity, in both pressure and flow angle, at the two ends of plate. In a special limit, this singularity changes its type, emerging into a logarithmic one, which is the weakest type possible. Guided by this analytic solution of the linearized problem, approximate solutions have been calculated for the nonlinear problem using the Rayleigh-Ritz method and the numerical results compared with the linearized theory

D7-Brane Chaotic Inflation

We analyze string-theoretic large-field inflation in the regime of spontaneously-broken supergravity with conventional moduli stabilization by fluxes and non-perturbative effects. The main ingredient is a shift-symmetric Kahler potential, supplemented by flux-induced shift symmetry breaking in the superpotential. The central technical observation is that all these features are present for D7-brane position moduli in Type IIB orientifolds, allowing for a realization of the axion monodromy proposal in a controlled string theory compactification. On the one hand, in the large complex structure regime the D7-brane position moduli inherit a shift symmetry from their mirror-dual Type IIA Wilson lines. On the other hand, the Type IIB flux superpotential generically breaks this shift symmetry and allows, by appealing to the large flux discretuum, to tune the relevant coefficients to be small. The shift-symmetric direction in D7-brane moduli space can then play the role of the inflaton: While the D7-brane circles a certain trajectory on the Calabi-Yau many times, the corresponding F-term energy density grows only very slowly, thanks to the above-mentioned tuning of the flux. Thus, the large-field inflationary trajectory can be realized in a regime where Kahler, complex structure and other brane moduli are stabilized in a conventional manner, as we demonstrate using the example of the Large Volume Scenario.Comment: 8 pages, 2 figures; v2: references adde

Turbomachinery technology for high-speed civil flight

NASA Lewis' research and technology efforts applicable to turbomachinery for high-speed flight are discussed. The potential benefits and cycle requirements for advanced variable cycle engines and the supersonic throughflow fan engine for a high-speed civil transport application are presented. The supersonic throughflow fan technology program is discussed. Technology efforts in the basic discipline areas addressing the severe operating conditions associated with high-speed flight turbomachinery are reviewed. Included are examples of work in internal fluid mechanics, high-temperature materials, structural analysis, instrumentation and controls