A Soviet space rocket introduced in 1965, used to launch heavy satellites, space probes, and the Salyut and Mir space stations.
Proton is a three-stage rocket that can lift 22 tonnes into low Earth orbit; a fourth stage is added for higher orbits.
Six Proton rockets launched Soviet missions to Mars from 1971 to 1973, and a Proton-K (with a Pizza Hut logo on its side) launched the Zvezda module to the International Space Station in July 2000. The more powerful Proton-M was first launched in April 2001. The Proton series has never been used to launch humans into space.
Subjects: Astronomy and Astrophysics.