List the three great pioneers of rocket science and their contributions.

Here are the three great pioneers of rocket science and some of their contributions:
1. Konstantin Tsiolkovsky - a Russian teacher who realized that liquid fuel instead of solid fuel is needed for rockets to fly outside of Earth's gravity
2. Robert Goddard - an American scientist who created a new system for rockets that cooled that gases that were leaving them which improved the way rockets work significantly
3. Hermann Oberth - a German scientist who created the rocket V-2 which was used in the WWII as a missile bomb

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