Getting to space
Space conventionally begins at the Kármán line, 100 km up. Reaching that height is easy compared with staying there: an orbit requires a horizontal speed of about 7.8 km/s. That is why orbital rockets are so much larger than sub-orbital ones.
Kinds of missions
Flyby missions such as Voyager pass a world once. Orbiters such as Cassini circle a planet for years. Landers and rovers such as Perseverance study surfaces up close. Sample-return missions bring material back to Earth's laboratories. Space telescopes such as Hubble and Webb look outward from above the atmosphere.
Humans in space
The International Space Station has hosted crews continuously since 2000, studying how the body adapts to microgravity. In April 2026 Artemis II carried four astronauts around the Moon, the first crewed lunar flight since 1972, as a step towards future landings.