Launched from mobile units, each V2 rocket was 14 metres (46ft) high and carried a ton (900 kg) of explosives. The first attack on London, on 8 September 1944, gouged a crater 10m (32ft) across, killed three people and injured 22.
However, unlike aircraft or the V2’s predecessor the V1 flying bomb, this was a new type of weapon, crashing and exploding without warning in target cities, such as London, Norwich, Paris, Lille and Antwerp. It took just five minutes from launch to landing. V stood for ‘vergeltungswaffen', or 'retaliatory weapon', and were a last-ditch attempt by the Germans to reverse the course of the war.
Although there is no exact figure, estimates suggest that several thousand people were killed by the missile – 2,724 in Britain alone. However, a far grimmer statistic is that many more, at least 20,000, died constructing the V2s themselves.

“It’s something that’s often glossed over, but shouldn’t be,” says Doug Millard, space historian and curator of space technology at London’s Science Museum, where a V2 takes pride of place in the main exhibition hall. “The V2 programme was hugely expensive in terms of lives, with the Nazis using slave labour to manufacture these rockets.
Despite his complicity in the conditions at Mittelwerk, the engineer who designed the V2, Wernher von Braun, came to be feted as a hero of the space age. The Allies realised that the V2 was a machine, unlike anything they had developed themselves.

At the heart of the V2 was a powerful motor capable of taking the rocket more than 80km (50 miles) above the Earth in a trajectory of some 190 km (120 miles). Fuelled by liquid ethanol and oxygen, it was much more sophisticated that anything built before and effectively the world’s first space rocket.
One of the most important new technologies developed for the V2 was an automatic guidance system, which operated independently of controllers on the ground. With the destination “programmed” into the on-board analogue computer, once a rocket was in flight, its gyroscopes could continuously track the craft’s position in three dimensions. Any deviations in course and rudders fitted to the fins on the side of the rocket would automatically adjust the heading and trajectory to keep it on target.

Not surprisingly, when the war ended, the Americans, Soviets and British scrambled to get their hands on V2 technology. With no desire to work for Stalin, Von Braun made a shrewd decision to surrender to the Americans, while the Russians got their hands on the V2 factory and test range
Both the Americans and Soviets took the V2s to bits to decipher their workings,” says Millard. “The Soviets completely recreated a V2 and the Americans took them over to America to launch and carry out some of the first upper atmosphere experiments.”

However, the US knew that it wasn’t the hardware that was as important as the men behind it. And they had Von Braun. Although the military’s priority was to develop intercontinental ballistic missiles, the German engineer now had the opportunity to pursue his dreams of spaceflight.

“After a brief hiatus, he started working for the American army on their Redstone missile and that was a direct derivative of the V2,” says Millard. “America’s first astronaut, Alan Shepard, was launched [in 1961] on a version of the Redstone missile.”
“We got to the Moon using V2 technology but this was technology that was developed with massive resources, including some particularly grim ones,” says Millard.

So would man have landed on the Moon without Hitler’s weapon? Probably, but perhaps not as soon. As with so many technological innovations, war hastened the development of the modern rocket and accelerated the space age.

Even today, the fundamental technology of launchers remains the same as it did 70 years ago. The engine looks similar, rockets still use gyroscopic guidance and most are powered by liquid fuel. All pioneered in the V2.
http://www.bbc.com/future/story/20140905-the-nazis-space-age-rocket