Science Forums 2

[UncleAl]

/_\P/_\V = energy, 101.325 joules/liter-atm. A supersonic object without streamlining moves too fast for air to get out of its way. The leading face gets serious sturm und drang from the compression. There generally isn't enough time between entry and impact for things to get interesting back of the leading face of a mechanically strong object.

An object in orbit about the sun cannot impact the Earth faster than about 40 miles second. If it augured straight in through 50 miles of atmosphere the rear of the asteroid would hardly know anything was amiss before the front impacted dirt or ocean. Obviously we can go for much slower intersections (e.g., a slow body approaching from Earth's orbital rear tangent to the direction of earth's rotation) and more glancing intersections.

A large well-consolidated iron or stone object impacting the Earth is pretty much going to arrive as the original lump, either as a bullet or as a tight shotgun blast from Roche instability and mechanical stress breakup. Small stuff will mostly shatter from atmospheric shock or vaporize outright. Comets, rich with mechanically weak volatiles, will traverse their mass of atmosphere and bloom into a hypersonic shockwave (e.g., Tunguska).

There is an intermediate class of intersections for objects of modest size and glancing direction where calculations are interesting, e.g., a Space Scuttle burning up during re-entry.