When you see "T-minus" followed by a time, the T stands for "Test" or "Time." It counts backward to zero, which is the moment of liftoff. Each milestone in the countdown triggers specific procedures.
The rocket is assembled, tested, and rolled out to the launch pad. Propellant is loaded, and all systems undergo final checks. Weather conditions are evaluated to ensure safe flight.
Engines ignite and the rocket climbs through the atmosphere. During the first few minutes, it experiences maximum aerodynamic pressure (called Max-Q). The rocket pitches over to begin its trajectory toward orbit.
Most rockets have multiple stages. The first stage burns out and separates, falling away (or landing for reuse on SpaceX rockets). The upper stage engine ignites to continue the journey to orbit.
The upper stage performs precise burns to achieve the correct orbit. This could be Low Earth Orbit (LEO) at ~400km, Medium Earth Orbit (MEO), Geostationary Transfer Orbit (GTO), or beyond.
Satellites are released from the rocket's payload fairing, or a spacecraft separates to continue its mission. For crewed flights, the capsule enters a free-flight phase.
Altitude: 160-2,000 km
Used for: ISS, Earth observation, Starlink satellites
Altitude: 2,000-35,786 km
Used for: GPS and navigation satellites
Altitude: 35,786 km
Used for: Communications satellites, weather monitoring
Altitude: ~600-800 km
Used for: Earth imaging satellites that pass over areas at the same local time
Altitude: Varies widely
Used for: Communications coverage of polar regions
Altitude: Beyond Earth
Used for: Missions to the Moon, Mars, and beyond