Re: Shuttlecraft - curved edges on top?
Those shapes are there in the earliest concept drawings of the shuttle - that is, once TPTB realized they could not afford a shape other than simple shoebox. Probably a sort of "we can't do wings on this budget but these are their futuristic equivalent" thing.
That's probably the basic explanation. The curved extensions of the hull sides make a simple, boxy craft a little less boxy, and they look as if they could have some sort of aerodynamic function for atmospheric flight.
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