Most powerful rocket stage

The most powerful rocket stage ever constructed was the Block A first stage of the Soviet N1 moon rocket, designed by the OKB-1 design bureau (today known as RSC Energia) and first fired on 21 Feb 1969. The N1's first stage generated 45,250 kN (around 10,172,000 lbf) of thrust at sea level. By comparison, the American Saturn V rocket generated 7,891,000 lbf (31,100 kN) at sea level. The N1 rocket was only launched four times, and none of the attempts reached orbit. As a result, the program was shut down in 1974.

The N1 project was initially overseen by Soviet rocket engineer and father of the Soviet space program, Sergei Korolev. It was intended to carry the planned Soviet crewed Moon mission, which it was hoped would reach the Moon before the US Apollo program. Starved of funds by comparison to the no-expense-spared US program, the Soviet moon program was plagued by technical delays and political squabbles, and was terminated without ever putting a cosmonaut beyond Earth orbit.

Four N1 rockets were launched between 1969 and 1972, none of which had a crew onboard. Each time, the sheer complexity of the design – which used 30 Kuznetsov NK-33 engines – caused the rocket to effectively shake itself apart. The first launch flew for 66 seconds before leaking oxidizer lines caused a fire to break out inside the engine bay, destroying the rocket.

The second attempt, on 21 July 1969, rose just 200 m off the launchpad before multiple engine failures saw it tumble back down and explode, doing so much damage to the launch complex that the no further launches could be attempted for almost two years.

Launch number three – attempted after the US had already successfully beaten the Soviet Union to the Moon – took place on 27 June 1971. On this occasion an uncommanded and sudden rotation caused the rocket to break apart just 250 m off the launchpad.

The final launch of the N1 took place on 23 Nov 1972. On this launch the rocket almost worked. The first stage burned nominally for 90 seconds before another propellant leak caused the first stage engines to start exploding. The first stage shut down at 107 seconds – just six seconds short of the planned first stage cut-off.