How long does it take a rocket to reach space?

The most widely used definition of where space begins is the Kármán line, at 100 km altitude, which the Fédération Aéronautique Internationale uses for its records; the US Air Force and NASA use 50 miles, about 80 km. A typical orbital launcher passes that mark two to three minutes into flight, roughly when the first stage separates. A Falcon 9 shuts down its first-stage engines around 2 min 30 s, at about 70-80 km, and crosses 100 km shortly after. A much lighter suborbital rocket like New Shepard reaches it in a little under four minutes and comes back down in just over ten.

Being at 100 km isn't enough to stay in space: without horizontal velocity the vehicle falls back down. Sustaining a low orbit requires reaching about 7.8 km/s, and gaining that speed is what takes up most of the ascent. The space shuttle reached main engine cutoff at 8 min 30 s; a Falcon 9 shuts down its second stage at about 8 min 50 s on a typical low-orbit mission; a Saturn V needed about 11 min 40 s. For higher destinations, such as geostationary orbit, the second stage reignites after a 20-30 minute coast phase.

For other destinations the clock stretches out considerably. Capsules headed to the International Space Station reach orbit in nine minutes but dock between six hours and two days later, depending on the mission profile. Apollo missions took about three days to reach the Moon, and a probe to Mars travels for six to nine months. Launch, then, is the shortest part of the journey: space is only minutes away, but the destination, almost always, is much farther.