Goddard

    Another was a young American, Robert Hutchins Goddard (1882-1945). A native of Worcester, Massachusetts, Goddard's family was staying at the suburban home of friends in Worcester when, on October 19, 1899, he climbed into an old cherry tree to prune its dead branches. Instead, he began daydreaming:

Order: complete patent application if necessary of nozzle and plurality; take out application on reloading feature; also complete application for electric pump; repeat calculation carefully, for smaller intervals; look up Darwin's theory of the lunar motion; and look up meteors. Also try a jet.

De Laval's Nozzle

De Laval's turbine:   4 nozzles, one in  cross section.

    Goddard experimented on his ballistic pendulum with various nozzle designs, using a small metal combustion chamber filled with a type of gunpowder, ignited by electricity. The end of the chamber was threaded, so that nozzles of various designs could be screwed onto it and tested. Using a De Laval nozzle, he obtained jet velocities between 7000 and 8000 ft/sec and efficiencies of up to 63%. Later he replaced the ballistic pendulum with a more compact device, in which the thrust of the rockets did not lift a pendulum against gravity but compressed a calibrated spring. With that device he showed that (contrary to some popular claims) rockets worked just as well in a vacuum.

    As Goddard himself noted, that made the rocket the most efficient of all heat engines, better than piston-driven steam engines (21%) and Diesel engines (40%). No wonder: from the second law of thermodynamics, the theoretically attainable efficiency of a heat engine increases with its operating temperature, and no other heat engine runs as hot as a rocket.

A rocket engine at the   Smithsonian, cut open to  show convergent-diver-  gent DeLaval nozzle.

    After the US entered World War I, Goddard also worked for a while on military rockets, but none of his designs were implemented, though rockets somewhat similar to his design were turned in World War II into an effective weapon against tanks, known as the bazooka (a variant of this is now the "rocket propelled grenade" or RPG).

Note: The autobiographical book by Homer Hickam "October Sky" (anagram of its original title "Rocket Boys"; later made into a film) tells of a group of high-school students in a poor Appalachian coal-mining town who, taken by the idea of space flight, design and fly home-built rockets of greater and still greater range. Their break-through comes when they discover in a book the design of the De-Laval Nozzle.

    The idea of feeding the rocket with a continuous stream of solid charges also proved unfeasible, and in 1922 Goddard went back to his alternative idea, proposed independently by Hermann Oberth in Germany and also noted by Tsiolkovsky: a liquid-fuel rocket. It would have two lines running into its combustion chamber, one feeding fuel, the other oxygen, similar to the way a steel-cutting blowtorch operated, except here both lines carried liquids, not gases--in Goddard's design, gasoline and liquid oxygen.

    Such a rocket promised very high efficiency, but also posed serious technological challenges. Both fluids had to be pumped at a steady rate, and one of them, liquid oxygen, was extremely cold. The high temperature of combustion in pure oxygen required heat-resistant materials, and to help overcome this, Goddard developed the technique of having the liquid oxygen cool the combustion chamber on its way from the fuel tank. This method is still use: in the picture above, the nozzle and the "bell" guiding the expanding jet are lined with a large number of metal pipes, through which the cold fuel flows on its way to the combustion chamber.

Robert H. Goddard besides   1926 liquid- fueled rocket.   The rocket is on top, recei-   ving its fuel by two lines   from the tank at the bottom.

   Another completely novel problem which faced Goddard was the guidance and control of the rocket in flight. On March 16, 1926, Goddard flight-tested his first liquid-fuel rocket. He thought stable flight could be obtained by mounting the rocket ahead of the fuel tank, with the tank shielded from the flame by a metal cone and the lines for fuel and oxygen pulling it behind the rocket: the design worked, but did not produce the hoped-for stability. The rocket burned about 20 seconds before reaching sufficient thrust (or sufficiently lightening the fuel tank) for taking off. During that time it melted part of the nozzle, while the camera with which Mrs. Esther Goddard was trying to record the flight ran out of film, so that no photographic record of that flight remains. Then it took off to a height of 41 feet, leveled off and later hit the ground, all within 2. 5 seconds, averaging about 60 mph.

    Goddard's concept seemed validated, but he was still far from a practical design. Unfortunately, he worked in isolation, without the engineering resources of a major institution. In the years that followed he continued developing his rockets--controlling their motion by gyroscopes, steering them with small vanes thrust into their exhaust jet, and building larger and faster rockets. For testing the rocket engines were tied to frames on the ground, and some were also tested in free flight, mostly at a rocket lab he established in Roswell, New Mexico.

But the actual realization of his dream fell to others who enjoyed military or national support. Goddard, unfortunately, never lived to see the age of spaceflight. He died of cancer on August 10, 1945, in Baltimore.