Black powder had a very low specific impulse. The way rockets were made got more advanced, but only on paper. People had not really built a much better rocket yet. They only had ideas and sketches of better models. In 1591 a Belgian, Jean Beavie, wrote about and drew the important idea of rockets that had more than one stage. This is called Multistaging. This means that the fuel is burned through in more than one step. This is the answer to escaping earth’s gravity and going into space.