A landing planned before the shuttle reached the runway
A space shuttle returned from orbit with enormous speed, but by the time it approached a landing site, its main engines were no longer an option. They were designed to fire in space, not to lift the orbiter off a runway. The shuttle therefore had to convert the energy of its return into a controlled descent and arrive in position for one landing attempt.
Unlike an airliner, the orbiter was a poor glider: it lost speed and altitude quickly. Its approach was deliberately steep, bringing it down toward the runway at a much sharper angle than a conventional aircraft. The crew had to manage that descent precisely, using the orbiter’s control surfaces and speed-brake to adjust its path and speed.
No go-around if the approach went wrong
An airliner can add power, climb away, and try again. The shuttle could not. There was no powered climb available, so the crew had to commit to the selected runway and hit the planned approach path. Aiming too high or too fast could leave too little runway; arriving too low or slow could put the orbiter short.
Near the runway, the commander raised the nose to reduce the descent rate, then lowered the landing gear for touchdown. That final flare turned a steep, fast glide into a runway landing. The key constraint was not simply that the shuttle had no engine thrust at touchdown: every correction had to fit within the energy and altitude it had left.
