Příbram: The First Instrumented Fall and Its One-Percent Survival

This paper computes a complete entry budget for the Příbram fall, working only from published values and stated assumptions. The nominal body has a diameter of 0.645 metres at a bulk density of 3.40e+03 kilograms per cubic metre, giving an incoming mass of 0.477 tonnes. At the published entry speed of 20.9 kilometres per second its kinetic energy is 0.0249 kilotonnes of TNT equivalent. At the characteristic altitude of 28 kilometres the exponential atmosphere has a density of 0.0251 kilograms per cubic metre, the ram pressure on the body is 11 megapascals, the stagnation heating flux is 1.14e+05 megawatts per square metre, and the aerodynamic deceleration is 764 times terrestrial gravity. The ram pressure first reaches representative material strengths at computed altitudes of 61.8, 45.2 and 33.6 kilometres for the weakest, intermediate and strongest cases examined. The recovered material, the recovered stones of the Příbram fall, amounts to 5.6 kilograms, which is 1.17 percent of the computed incoming mass. The largest recovered piece, at 4.25 kilograms, has a characteristic diameter of 13.4 centimetres, a terminal velocity of 102 metres per second, a fall time of 128 seconds from the end of the luminous path at 13 kilometres, and a wind drift of 1.28e+03 metres under a representative wind. All values are computed by the deposited program from the stated inputs; scenario calculations accompany every headline figure so that the sensitivity of each conclusion to its inputs is visible in the same record.