A quasi-simple ablation model for large meteorite entry: theory vs observations

Abstract

An approximate, analytic, single-body, one-dimensional ablation model has been developed to predict the entry behavior of large meteorites during their hypersonic drag interaction with the Earth's atmosphere. The entry predictions are compared against multistation photographic data from Pribram, Lost City and the recent Innisfree Meteorite. Typical results indicate that the ablation parameter, σ, is ~0.02 to 0.03 s 2/km 2, in the vicinity of the peak ablation altitude, in good agreement with the intersection method of McIntosh which has also been applied separately to each fragment of Innisfree. The altitude associated with the peak ablation in these cases, ranges from ~25 to 40 km. Initial preatmospheric masses are also estimated, ~20 kg for Innisfree, ~60 kg for Lost City and ~250–3200kg for Pribram. Gas cap radiation is found to play a dominant role in the heat transfer predictions for such objects. This is especially so in the more general case, for velocities ≳ 16 km/s. In addition, it was determined that for bronzite type chondrites, preferential survival occurred for initial radii ~2–8 cm, where a relative minimum in the percent mass loss is predicted. This minimum occurs precisely in the region where turbulent convective heat transfer and gas cap radiation are of comparable importance. Finally, for velocities >30 km/s, percent mass loss is predicted to be near 100% for initial radii between 1 cm and 10 m for bronzite type meteorites.