Timeline: 1921-1930 Date Event 1923 A German mathematician and physicist, Herman Oberth published a book called ‘the rocket into interplanetary space.?/td> 1925 Walter Hohmann, a German architect published a book called ‘The possibility of reaching celestial bodies?which contained the first detailed calculations of interplanetary orbits. 1926 Robert Goddard launched the first successful liquid propelled rocket on March the 16th. His inventions were later adapted for military use. It wasn’t until the end of the second world war that the United States government started applying his theories to rockets that could escape Earth’s gravity and journey to space.