OPERATION GREENHOUSE. Scientific Director's Report of Atomic Weapon Tests at Eniwetok, 1951. Annex 1.6. Blast Measurements. Part 2. Free-Air Peak-Pressure Measurements. Section 2. Telemetering from Moored Balloons,
JOHNS HOPKINS UNIV LAUREL MD APPLIED PHYSICS LAB
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The purpose of this experiment was to determine the free-air peak-pressure as a function of distance from an atomic explosion. In this report, free-air peak-pressure is defined as the pressure at the head of the blast wave in regions where it has not been reinforced by a reflected wave. Operation in the test area was more difficult than anticipated. Heavy winds made balloon handling very difficult. On the whole, the radio link performed satisfactorily on all occasions and appears to be a reliable method. For some unknown reason, blast switches closer than 1,500 feet failed to give satisfactory signals. Pressures were computed using the Rankine-Hugoniot relation, which is based on the shock wave being a definite discontinuity in pressure. Since the pressures measured on the ground showed relatively long times, there has been some speculation that a true shock wave may not exist in free air. If a true shock wave does not exist in the free-air region, pressures as computed are not correct, and the method of this experiment cannot be used.