On June 30, 1908, the remote Siberian region of Tunguska made headline news when an explosion knocked down 80 million trees in an area of only 770 square miles. The mystery was that there was no crater, which led to the assumption that the space bomb responsible for the catastrophe detonated in midair--a behavior scientists call an "air burst". The explosion must have happened four to six miles above the actual lands of Tunguska. We know that the space bombs that visit Earth, be they comets or asteroids, comprise of any of three materials--rock, metal or ice, and each reacts differently to the rising pressure associated with descending to the Earth's atmosphere at high speed. Let's say that we have a scenario where a space bomb is due to explode four to six miles above the earth and duplicated it three times so that we have one scenario where the space bomb is made of rock, another of metal and one more of ice. At an altitude of four to six miles, what is the largest space bomb from each scenario that would fall down before being detonated in midair?