Suborbital trajectory

In the early days of manned space flight both the Soviets and the Americans planned for a series of suborbital flights before committing their crew members to the more challenging orbital space flight trajectories. A suborbital flight path is similar to a ballistic trajectory to the upper reaches of the atmosphere and then falls back due to insufficient velocity to attain orbital flight. This type of space­flight was flown during the first American manned (Mercury) space shots in 1961. Launched from a carrier aircraft, the 13 X-15 rocket research aircraft flights which were similar but termed “astro-flights” rather than suborbital as they reached lower peak altitudes. It was this type of trajectory that was achieved by the three SpaceShipOne flights in 2004 to claim the “X-Prize”. The failed Soyuz launch in 1975 was also high enough to follow a suborbital trajectory.