According to NASA, approximately how many hours is the re-entry descent of a space shuttle after Mission Control gives the “go” for deorbit burn?
As it aligns with the runway, the orbiter begins a steep descent with the nose angled as much as 19 degrees down from horizontal. This glide slope is seven times steeper than the average commercial airliner landing. During the final approach, the vehicle drops toward the runway 20 times faster than a commercial airliner as its rate of descent and airspeed increase. At less than 2,000 feet above the ground, the commander raises the nose and slows the rate of descent in preparation for touchdown.
Landing the STS120 Space Shuttle: one hour before touchdown