How long a rocket takes to reach space?

Getting to the edge of space is a matter of a few minutes of climb. The conventional boundary, the Karman line, sits at 100 km; the United States has long used a lower threshold of 80 km for awarding astronaut status, which is why some flights count under one convention and not the other. A suborbital vehicle such as New Shepard crosses the line only a few minutes after lift-off, coasts through apogee and is back under parachutes for a total flight of about 11 minutes, of which the passengers spend a handful of moments weightless.

Orbital launches take longer because altitude alone earns nothing. Stop at 100 km with no horizontal speed and the vehicle falls straight back down. To stay in orbit a spacecraft needs around 28 000 km/h, and almost all of a launcher's burn goes into building that speed rather than into climbing. That is why a rocket pitches over early and spends most of its ascent flying nearly horizontally, shedding empty stages as it goes. Continuous thrust through those minutes is the whole trick: unlike an aircraft, a launcher cannot pause halfway to reconsider.

By the time the first stage separates, the vehicle is already above most of the atmosphere and accelerating hard, because it is burning propellant and getting lighter every second. The drama is concentrated at the start, in the dense lower air, where the structure sees its greatest aerodynamic load. After that the ascent becomes almost undramatic: a long, flat push against nothing, with the upper stage running until cut-off arrives at a precise velocity rather than at a particular height. Miss that velocity and the payload comes back down, however high it went.