Crewed suborbital space flight has been uncommon over the years, but with the advent of space tourism may soon become a frequent occurrence. The first manned suborbital flights were the two Mercury-Redstone missions in May and July of 1961. The X-15 research aircraft made two flights above 100 km in July and August of 1963, becoming the first craft to fly into space twice and its pilot, Joseph A. Walker, the first person to fly twice into space.
The next manned suborbital space flight would not be until April 5, 1975, and it wasn’t supposed to be one. Soyuz 18 was to launch two Soviet cosmonauts to the Salyut 4 space station, but the third stage of the launcher failed to separate from the second stage and the Soyuz spacecraft performed an abort from the failed booster. Velocity was already 4 km/sec at the abort, well below orbital velocity, so the spacecraft proceeded on a steep trajectory which carried it to an altitude of 192 km before a crushingly steep entry into the Earth’s atmosphere where the crew endured an almost unthinkable peak deceleration of 21.3 gravities.
The descent capsule landed in mountainous terrain near the Chinese border and was only saved from tumbling off a cliff when its parachutes became tangled in vegetation. Both crewmen sustained injuries from the acceleration and commander Vasily Lazarev, while remaining in the cosmonaut corps, was never to fly again. Flight engineer Oleg Makarov went on to fly on three subsequent Soyuz missions.
There would not be another manned suborbital flight until the three flights of SpaceShipOne in 2004, and another long gap until Blue Origin began to fly crews in July 2021.
Puzzle: who was the first woman to make a suborbital space flight?
(In this article, I use the international definition of space flight as 100 km or more above sea level. Several X-15 flights exceeded the U.S. Air Force definition of space of 50 statute miles [80.5 km] but did not reach 100 km.)