April 4, 2012: March 30th marked the end of an era, as the last Russian Proton K launch vehicle successfully put a military surveillance satellite into orbit. This was the 311th launch of a Proton rocket. One of the most widely used space rockets in history, the Russian Proton, made its 300th launch nine years ago. In the last two decades Protons have earned over $6 billion putting foreign satellites into orbit, especially high orbits.

Originally designed as an ICBM in the 1960s, but never used that way, the Proton proved better at launching satellites. Proton K is actually a launcher system that can be configured with three or four stages and different types of booster rockets to put different types (and weights) of satellites into orbit. Proton K could put 20 tons into low orbit and 5 tons into the highest (stationary) orbits. Current Protons cost nearly $70 million to build and launch. These use a lot of 1960s technology. A new model, the Proton M, replaces all the 1960s stuff and is basically a new rocket design. The Proton M has been in service 11 years and made 61 launches so far.

Overall, nearly 90 percent of Proton launches have been successful, although the success rate has been higher in the past few years. One of the most notorious failures occurred last year because of an error by the crew loading fuel. Too much liquid oxygen was loaded into one tank, making the rocket too heavy to follow the flight path its guidance system was programmed for. Since this was a human, not a mechanical or design error, senior members of the Russian Space Administration were fired and launch procedures reviewed and revised.

Proton's owner, Khrunichev State Research and Production Space Center, is developing a new, and cheaper, heavyweight rocket, the Angara. This rocket was supposed to enter service by 2006, but first flight won't take place until next year. Meanwhile Proton M has taken over the work of putting satellites into high orbit until Angara is finally ready.

The most used launcher is the Russian R-7 (Soyuz), which has launched over 1,600 times. The Soyuz is a much smaller rocket, which can only put 6.4 tons into low orbit.