Why do we hear 2 sonic booms when the shuttle flies overhead during landing?

Question

Why do we hear 2 sonic booms when the shuttle flies overhead during landing?

Answer 1

The nose and tail both create sonic booms but on most shorter aircraft, the human ear combines the two sounds into one.  Because the shuttle is longer, the human ear is able to distinguish the two as they occur approximately 1/2 second apart.

Answer 2

There are two shock waves generated by a supersonic object...one at the nose and one at the trailing edge (tail). Most aircraft that fly supersonic are short enough that the two shock waves pass a ground observer too fast to be distinguishable, so they sound like one boom.

The Space Shuttle is large enough that the shock waves are separated enough by time that you can hear two disinct booms.