Winchcombe: How a Slow, Weak Carbonaceous Body Delivered Most of Its Stone to a Driveway

This paper computes a complete entry budget for the Winchcombe fall, working only from published values and stated assumptions. The nominal body has a diameter of 0.202 metres at a bulk density of 3.00e+03 kilograms per cubic metre, giving an incoming mass of 0.013 tonnes. At the published entry speed of 13.9 kilometres per second its kinetic energy is 3.00e-04 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 4.84 megapascals, the stagnation heating flux is 3.37e+04 megawatts per square metre, and the aerodynamic deceleration is 1.22e+03 times terrestrial gravity. The ram pressure first reaches representative material strengths at computed altitudes of 55.9, 39.4 and 27.8 kilometres for the weakest, intermediate and strongest cases examined. The recovered material, the main stone found on a residential driveway, amounts to 0.602 kilograms, which is 4.63 percent of the computed incoming mass. The largest recovered piece, at 0.319 kilograms, has a characteristic diameter of 5.64 centimetres, a terminal velocity of 66 metres per second, a fall time of 273 seconds from the end of the luminous path at 18 kilometres, and a wind drift of 2.73e+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.