Short answers, pulled from the story.
Spaceflight is an application of astronautics to fly objects, usually spacecraft, into or through outer space, with or without humans on board. It is achieved conventionally with multistage rockets that provide thrust to overcome gravity. Once a spacecraft reaches high enough speeds in orbit, it falls around the Earth rather than back to the surface.
Spaceflight began in the 1950s with the launches of the Soviet Sputnik satellites and the American Explorer and Vanguard missions. The world's first artificial Earth satellite, Sputnik 1, launched on the 4th of October 1957. The first human spaceflight was Vostok 1 on the 12th of April 1961, carrying cosmonaut Yuri Gagarin.
Konstantin Tsiolkovsky set down the fundamental rocket equation in his 1903 work, The Exploration of Cosmic Space by Means of Reaction Devices. Known as the Tsiolkovsky rocket equation, it relates a rocket's change in velocity to its exhaust velocity and its initial and final masses. Engineers still use it as a key concept of spaceflight.
A V-2 rocket became the first human-made object to reach space during a test flight in June 1944, climbing to an altitude of 189 km. The V-2 was the first guided rocket, developed and used as a weapon by Nazi Germany during World War II.
The most commonly recognized boundary of space is the Kármán line, 100 km above the Earth's surface. The United States alternatively defines outer space as everything beyond 50 mi in altitude, and NASA defines an astronaut as someone who has flown more than 50 mi above sea level.
Kessler syndrome is the problem of continuous collisions among uncontrollable spacecraft in frequently used orbits. When large objects such as upper stages break up or collide, they create hundreds of small, hard-to-find pieces of debris, raising the risk that orbit could become inaccessible for generations.