Robert Goddard and His Rockets

Reading about Robert H. Goddard and his rockets sent me off on a science jag as a kid. My brothers also caught the rocket bug - they used to build them and launch them and then the big trick was trying to find them after they landed. It was great fun (especially if I could find the rocket before they did). Perhaps I should note that these were decidedly toy rockets, relatively small, and usually the parachutes worked, so we weren't really posing that much threat to the community.

The title-linked article takes a look at the history of rockets, with an emphasis on Goddard's work. It also explains what a ballistic pendulum is and what it does, and takes a look at Gustav De Laval's turbine, more specifically at the nozzle design he came up with that bears his name and has been rather useful:

...Luckily for Goddard, this problem had been solved by Gustav De Laval, a Swedish engineer of French descent. In trying to develop a more efficient steam engine, De Laval designed a turbine whose wheel was turned by jets of steam.

The critical component, the one in which heat energy of the hot high-pressure steam from the boiler was converted into kinetic energy, was the nozzle from which the jet blew onto the wheel. De Laval found that the most efficient conversion occured when the nozzle first narrowed, increasing the speed of the jet to the speed of sound, and then expanded again. Above the speed of sound (but not below it! ) this expansion caused a further increase in the speed of the jet and led to a very efficient conversion of heat energy to motion. Nowadays steam turbines are the preferred power source of electric power stations and large ships, although they usually have a different design--to make best use of the fast steam jet, De Laval's turbine had to run at an impractically high speed. But for rockets the De Laval nozzle was just what was needed...

This article is from the From Stargazers to Starships 'book-on-the-web' by David P. Stern. See here for the home page.