Rockets are projectiles that are propelled by the expulsion of gases generated in a combustion chamber. The first solid-fuel rockets, invented by the Chinese in the 13th century, used a mixture similar to gunpowder for fuel. Although rockets were used in warfare to set fire to buildings and the sails of ships for nearly 500 years, it wasn't until the early 19th century that the first crude explosive rockets were used in battle. Research and design efforts by scientists such as Robert Goddard in the 20th century refined rocket design to produce faster, better controlled rockets. During World War II, this new technology was used to create the German V-2 "buzz bomb", the first true guided missile. Scientific developments since World War II have been applied to adapt the rocket for use in even more powerful and accurate weapons with incredible range. The rocket is also used in peaceful application such as the launch of satellites and the exploration of space.