Suborbital spaceflight

A spaceflight that reaches space or near-space altitude but follows a trajectory that does not complete an orbit around a celestial body.

Suborbital trajectory: A path that reaches space or near-space altitude without completing an orbit around a celestial body. It distinguishes the flight path from an orbital trajectory.
V-2 rocket: A German ballistic missile developed during World War II and used in combat from 1944. Some V-2 launches crossed the conventional boundary of space without orbiting Earth.
Suborbital space tourism: Commercial passenger flights that provide brief experiences of space and weightlessness without entering orbit. Tourism is a prominent commercial use of crewed suborbital vehicles.
Orbital spaceflight: Spaceflight that places a vehicle on a trajectory completing repeated revolutions around a celestial body. Unlike suborbital flight, it requires enough sideways speed to keep missing the body as it falls.
Orbital mechanics: The study of motion under gravity, especially the paths of spacecraft and other celestial bodies. It explains why reaching altitude alone does not place a vehicle in orbit.
Alan Shepard: The American astronaut who became the first U.S. citizen in space in 1961. His Freedom 7 flight was the first crewed American suborbital spaceflight.
Microgravity research: Scientific investigation conducted in conditions where gravity's effects are greatly reduced. Brief free-fall periods let experiments study phenomena under microgravity.
Ballistic missile: A missile that follows a largely ballistic trajectory after powered ascent, often reaching beyond the atmosphere. Its flight can resemble a suborbital arc, but its purpose is weapon delivery.
Escape velocity: The minimum speed needed for an object to escape a celestial body's gravitational field without further propulsion. Suborbital vehicles remain gravitationally bound rather than reaching escape trajectories.
X-15 Flight 90: A 1963 flight of the North American X-15 that reached 107.96 kilometers altitude. It is a landmark example of a piloted, rocket-powered suborbital flight.

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