Proton rocket
The Proton rocket (formal designation: UR-500) is a Russian unmanned space vehicle design first launched in 1965 and still in use as of 2003.
Proton initially started life as a "super ICBM." It was designed to throw a >10-MT nuclear warhead over a distance of 12,000km. It was, of course, hugely oversized for an ICBM and was never used in such a capacity. Its real purpose was as a launch vehicle.
Proton is fueled by Unsymmetrical dimethyl Hydrazine and Nitrogen tetroxide. These are hypergolic fuels which burn on contact, voiding the need for an ignition system. They are stored at ambient temperatures avoiding the need for low temperature tolerant components and also allowing the rocket to sit on the pad indefinitely without need for continuous topping up of boiling off cryogenic fuels. They are, however, very toxic fuels that require special handling care.
Between the first flight in 1965 and the early 1970's, the Proton was a very unreliable launcher causing the loss of many space vehicles. By the mid 1970's the flaws were worked out and it became a very reliable rocket which it remains to this day.
Proton launched the unmanned Soviet circumlunar flights and would very likely have launched the first humans to circle the moon had the flight of Apollo 8 gone as originally planned. Proton launched the Salyut space stations, Mir core segment, and both Zarya and Zevezda of the ISS. It also launched many probes to the Moon, Mars, and Venus.
Launch capacity to low Earth orbit is about 20 tons. Interplanetary transfer capacity is about 5–6 tons.