On the Validity of the Pancake Models of the Falls of Cosmic Bodies in the Atmosphere

Semianalytical pancake models published in the literature are considered, in which it is assumed that a low-strength, fragmented body, like a liquid, expands during flight in the atmosphere and, while maintaining a certain simple shape and increasing the cross-sectional area, decelerates at much higher altitudes than a strong body. Individual models differ in the rate of increase in the transverse size of the body. For comparison with the models, hydrodynamic simulations of falls of liquid bodies with a diameter of 40 m in the Earth’s atmosphere were carried out without taking into account ablation. Such bodies, before they begin to slow down significantly, break up into fragments. Unlike simple models, while the body remains coherent, it can take on very distorted shapes. Comparison of pancake models with the results of hydrodynamic modeling allows us to determine the most suitable models for assessing the behavior of asteroids in the atmosphere and evaluate the assumptions embedded in them. In hydrodynamic modeling taking into account ablation, as shown by the results published in other works, complete evaporation of the body can first occur and, only then, the braking of the vapor jet. In pancake models, complete evaporation means the disappearance of mass and a complete stop of motion. The theoretical basis of these models needs to be revised.