Please consider what the atmospheric density is when the speeds are occurring. On ascent, speeds are increasing as air density decreases. On decent, the shuttle is getting heavier as the air thickens and still needs to bleed off kinetic energy (in the form of heat).

No doubt NASA is lying their asses off about a great many things, but this phenomena fits with established, repeatable physics.

It doesn't matter anyways.

NASA is fake and doesn't send rockets, or any other type of aircraft, into outer space.

The whole Space Shuttle Challenger "disaster" is one of the biggest hoaxes ever.