Almahata Sitta: A Recovery Fraction of a Predicted Impact, from Orbit to Desert Floor

This paper computes a complete entry budget for the Almahata Sitta fall, working only from published values and stated assumptions. The nominal body has a diameter of 4.1 metres at a bulk density of 2.30e+03 kilograms per cubic metre, giving an incoming mass of 83 tonnes. At the published entry speed of 12.4 kilometres per second its kinetic energy is 1.53 kilotonnes of TNT equivalent. At the characteristic altitude of 37 kilometres the exponential atmosphere has a density of 7.18e-03 kilograms per cubic metre, the ram pressure on the body is 1.1 megapascals, the stagnation heating flux is 6.85e+03 megawatts per square metre, and the aerodynamic deceleration is 17.9 times terrestrial gravity. The ram pressure first reaches representative material strengths at computed altitudes of 54.3, 37.7 and 26.1 kilometres for the weakest, intermediate and strongest cases examined. The recovered material, the recovered fragments collected in the Nubian Desert, amounts to 10.5 kilograms, which is 0.0127 percent of the computed incoming mass. For scale, a single spherical fragment carrying that recovered mass would have a diameter of 18.1 centimetres, a terminal velocity of 118 metres per second, a fall time of 169 seconds from the end of the luminous path at 20 kilometres, and a wind drift of 1.69e+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.