Engines are the key to successful rockets. Ever since Robert Goddard flew the first liquid-fuelled rocket in 1926, scientists and engineers have been striving to make more powerful and more efficient rocket engines. The US approach was to deal with design issues on the drawing board, and test only when they thought the design was the best they could get. The Russians had a much more experimental, hands-on philosophy, building rockets and using full test flights to find out how to improve their designs. Surprisingly, it's the hands-on Russian technology that will power a new generation of US rockets into space.