Universal Rocket

Intended to allow the same technology to be used in all Soviet rockets, the UR is produced by the Khrunichev State Research and Production Space Center.

Nine test flights were made between 4 November 1963, and 20 October 1964, before the program was cancelled in favor of Mikhail Yangel's R-36 missile and Tsyklon carrier rocket derivative.

But one distinguishing feature was that the engines of the first stage were cross-fed with fuel and oxidizer from the tanks of the strap-on boosters during the initial flight phase.

This meant that when the boosters were spent and jettisoned, the central stack still flew with full tanks, thus reducing dead weight and increasing a possible payload.

The UR-900 would have stood 90 metres (295 ft) tall, had a liftoff thrust of 94,000 kN (21,132,000 lbf), and be able to place 240 tons into low Earth orbit.