The principal blast effects are crushing due to overpressure and the change in steady state aerodynamic conditions due to the material velocity. The latter ia similar in nature to the sharp-edged gusts enountered in the normal atmosphere. These changes are in- fluenced by bending of the structure and displacement of the entire aircraft. For Castle, analytical and experimental investigation established the critical overpressure of the B-36 as 0.8 psi, and of the B-47 as 1.0 psi. The analysis of gust loading established the B~36 horizontal stabilizer as the critical component. Since the B-47 experiment was primarily designed to investigate thermal effects, the gust~load investigation was performed only to establish the safety of the aircraft for the thermal input to be obtained. Two basic problems were involved in the operation of the aircraft: the flying of the aircraft to a point in space at a given time, and the accurate determination of the actual TABLE 6.1 DESIRED AND ACTUAL POSITIONS AT TIME ZERO AND TIME OF SHOCK ARRIVAL Shot 3 data unusable because of iow yield. All B-36 data calculated from radar soope photos except for Shot 6, which ia Raydist data. B-47 data obtained from ship's instrumentation for Shota 4 and 6 and from Raydist data for Shots 1 and 2. Shot 1: Ranges in thousands o* feet. Hortzonta) Ranges At Time-zero At Shock-arrival Desired Actual Desired Actual Shock-Arrival Position Slant Actual Range Altitude B-36 50.0 50.8 76.7 71.5 73.8 $3.0 B-47 48.0 50.9 1210 137.5 141.9 38.0 2: 3-386 B-47 50.0 50.0 51.7 7&8 18.8 132.0 17.9 192.6 86.2 198.7 37.0 35.0 4: B-36 B-47 50.0 42 2 50.5 842 78.6 119.4 81.6 140.0 89.6 144.3 87.1 35.0 6. B-36 396 40.6 65.5 69.7 80.4 40.0 6: B-36 B-47 121.4 32.8 122.0 29.5 90.3 84.6 86.0 84.0 62.1 91.0 33.0 35.0 B-~47* — _ . — ~ _ —_ * B-4° aborted Shot 5 because of fue] leak. flight path during the thermal and blast phases of the detonation. Positioning was in general performed by aircraft instrumentation, and tracking by a combination of aircraft instrumentation and a Raydist Radio Navigation System. For safety reasons, positioning was based on the predicted maximum-possible yield of the device. For both experiments, danger-region diagrams were plotted in terms of horizontal range and altitude, upon which the effects parameters discussed previously were plotted simultaneously in order to show the boundaries of regions within which aircraft damage would result. These diagrams were used on each shot under a given set of conditions of yield, aircraft velocity, and aircraft configuration, to establish a position in space which would give the desired input without endangering the aircraft. Positioning data is sum-~ marized in Table 6.1. Thermal instrumentation was installed to define radiant exposure, irradiance, and the temperature rise on wing, fuselage, stablizer, and elevator. In addition, strain- gage bridges were installed in the left wing and stablizer of the B-47 to obtain informa- tion on the mechanical effects of the thermal input. Free-stream overpressure and pressures on the underside of various surfaces were measured. Blast-response data were in terms of strain-gage measurementa of the wing, fuselage, and stabilizer; linear 78