Rockets History & Theory
Sometime during the 11th century the Chinese discovered how to make a simple rocket using gunpowder for fuel. It didn't take the military leaders long to realize that the rocket could be used in defense of the great China wall. They strapped the rockets to their arrows and greatly extended the range of the bow and arrow.
Centuries later at White Sands Missile Range rockets are used to push guided missiles to their targets. Rocket engines are also used to propel test instruments and experiments into the upper atmosphere over Southern New Mexico. These rocket engines used today work on the same principles that made the Chinese fire arrows so effective.
In the 20th century the term "rocket" has become a household word. Huge rockets carried man to the moon and back. Because of rockets, Americans enjoy instantaneous world-wide communication via satellite. We even get a daily cloud-cover picture of our area taken from a satellite which was launched into space by a rocket. Soon people may be riding in rockets on a regular basis to get to work in a space station. In short, the rocket is the key to the exploration of the other worlds in the universe.
Early Rocket Development
From that time until the 20th century, the rocket had its ups and downs. It was quickly introduced in Europe in the 13th century as a firework and as a weapon. During the Renaissance every army had a rocket corps. But artillery improvements eventually made the cannon more effective because of increased range and accuracy. Occasional improvements in the rocket would bring it back into popularity, but usually not for long.
During this time one Chinese official hit on the idea of using rockets to propel a man through the air. It was around 1500 that Wan Hu rigged a pair of kites together with a chair attached in between. He then tied a series of military rockets to the kites and drafted a group of coolies to light the rockets. Not wanting to miss out on the chance for fame, Wan Hu decided to be his own test pilot. According to reports, he sat in the chair and gave the order to light the rockets. There was a lot of noise and a great burst of flame and smoke which blocked everyone's vision. When the smoke cleared, Wan Hu was gone. The story ends there and the reader is left to his own conclusions.
Used as a barrage weapon the rocket often proved effective for military purposes. In the late 1700's, Haider Ali, Prince of Mysore, India, used iron rockets to defeat a top British unit in battle. The British, in turn, used the rocket against the United States.
"O Say, Can You See...."
Congreve and an American, William Hale, did a lot during the l9th century to force armies to reactivate their rocket corps. Congreve's success came in his ability to extend the range of his military rockets to as much as 3,000 yards. Hale attempted to solve the problem of low accuracy by spin stabilization, a technique still used today. As the century progressed, artillery technology again by-passed the rocket and in the beginning of the 20th century, rockets were more a matter of speculation than reality.
Authors Jules Verne and H. G. Wells wrote about the use of rockets and space travel and serious scientists soon turned their attention to rocket theory. Knostantin Tsiolkovsky, a Russian, worked on rocket design and theory in the early 20th century. In his numerous writings he proposed space exploration by rocket, liquid propellants, the multistage rocket and space stations.
Hermann Oberth, a German scientist, also contributed to the theory and design of rockets. In 1923 he published a work in which he proved flight beyond the atmosphere is possible. In a 1929 book called "The Road to Space Travel" Oberth proposed liquid-propelled rockets, multistage rockets, space navigation, and guided and re-entry systems. He also advanced the idea of a transatlantic postal rocket for quick mail delivery. It was taken seriously at the time but never attempted.
From 1939 to 1945 he worked on German war rocket programs with such notables as Wernher von Braun. After the war he came to the United States where he again worked with von Braun. During the war one of the weapons the scientists were designing was reminiscent of Oberth's postal rocket. The German's wanted to build a rocket which would carry a bomb from Europe to strike New York City.
Most historians call Oberth and Tsiolkovsky the fathers of modern rocket theory. If that is so, an American, Dr. Robert H. Goddard, can be called the father of the practical rocket. His designs and working models eventually led to the German big rockets such as the V-2 used against the Allies in World War II. All three men are enshrined in the International Space Hall of Fame in Alamogordo, N.M.
Goddard started working with rockets in 1915 when he tested solid fueled models. In 1917 when the U.S. entered World War I, he worked on perfecting rockets as weapons. One of his designs turned out to be the forerunner of the bazooka, a tube launched, recoilless missile, 18 inches long and one inch in diameter. It was actually tested in 1918 but the war ended before it could be used against German tanks.
Space Flight Possible:
The press scoffed at his ideas and public reaction was poor. Goddard went on experimenting and on March 16, 1926 he flew the first liquid fueled rocket. After the initial success, he flew other rockets in rural Massachusetts until they started crashing in his neighbor's pastures. The local fire marshal declared his rockets were a fire hazard and ended his tests. Charles Lindbergh came to Goddard's rescue by helping him get a grant from the Guggenheim Foundation. With it Goddard moved to Roswell, New Mexico, where he could experiment without endangering anyone. There he developed the first gyro-controlled rocket guidance system and was eventually flying rockets faster than the speed of sound and at altitudes up to 7,500 feet. It was a huge improvement over the first liquid-fueled rocket which went 220 feet and was in the air only 2.5 seconds.
During World War II, the U.S. military saw little use for rockets. The Army did use bazookas but it was the Germans who took Goddard's ideas and turned them into real weapons. Goddard died in 1945 just as he started to receive some recognition for his work. One of his biographers said, "It is virtually impossible to design, construct or launch a rocket today without utilizing same idea or device originated by Goddard."
Under von Braun, the Germans perfected the large liquid-fueled rocket which culminated in the V-2 long range ballistic missile. It was the largest rocket vehicle at the time, being 46 feet long, 5.5 feet in diameter and developing 56,000 pounds of thrust or push. At the close of the war the allies captured V-2 components and the German development team surrendered to the Americans. The team and components were sent to White Sands Missile Range, New Mexico.
A V-2, assembled and launched on the range, was America's first rocket to carry a heavy payload to high altitude. A V-2 set the first high altitude and velocity record for a single stage missile, and a V-2 was the first large missile to be controlled in flight.
Jointly, the American and German scientists at White Sands worked to develop missile and rocket systems. From their work came such missiles as the Corporal, Redstone, Nike, Aerobee and Atlas.
Rockets have been around for centuries but no one has really understood how they worked until just recently. It was only 70 years ago when Goddard proposed that a rocket does not need air to push against. This is now obvious with the manned flights to the moon. But how do they work then?
How Rockets Work
If the hunter was on roller skates when he pulled the trigger, the recoil might be enough to push him backwards. And if he kept up a rapid rate of firing, he might pick up speed and continue to move backwards.
The same thing happens in a rocket. The rocket is the same as the rifle and instead of firing bullets, the rocket shoots out a stream of hot gases at supersonic speeds. The gases are pushed out as a result of the burning of a fuel in the combustion chamber.
Another way to look at this is to think of a long tank, shaped like a short pencil. If the tank is filled with compressed air and sealed, nothing happens. The gas is inside pushing against the walls, but the pressure is equally distributed. If one end of the tank is opened, the air pushes through the opening very quickly. According to Newton there should be an equal action in the opposite direction. There is. The air pushes on the front inside of the tank and if it is great enough the tank will move forward.
In a rocket engine the combustion chamber is very much like a rifle barrel or an air tank with one end open. In the rocket, a fuel, which can be a liquid like kerosene or a solid like gunpowder, is burned. The burning releases gases and heat which build up pressures in the chamber. The pressure pushes the gases out the exhaust nozzle. The reaction or push in the opposite direction drives the rocket forward.
The nozzle or exit hole for the pressurized gases is not just any opening. It is specially designed to open outward like an ice cream cone. This makes the gases exit even faster, which in turn, gives more push at the other end of the combustion chamber.
Rockets do best in outer space where the gravitational forces are less and there is no air resistance to overcome. But, there is also no air to keep the rocket fuel burning. Rockets work in space because they are completely self-contained. The rocket carries a fuel and an oxidizing agent like oxygen so it needs no outside air.
This explains why Polaris missiles can be fired from submarines while they are underwater. The fuel and oxidizer can be in solid or liquid form.
The huge rockets which hurl the astronauts and satellites into space use liquid fuels like kerosene or super-cold, liquid hydrogen and oxidizers like liquid oxygen. When the two liquids are sprayed into the combustion chamber, they ignite and burn with explosive force.
Use of Rockets at White Sands: At White Sands Missile Range, most of the missile systems under test use solid fuels and oxidizers. In a solid propellant, the fuel and oxidizer are mixed together and placed right in the combustion chamber. This makes the missile smaller than one using liquid fuel because there are no storage tanks for the fuel. Some solid propellants like nitroglycerine don't even need an oxidizer mixed in with it.
The solid-fueled rocket engine has many advantages for the military. It is smaller which makes it very portable. The solid fuels are much easier to handle than the caustic and sometimes super-cold liquids. Also, solid fueled rockets are always ready to fire. They do not require the preparation which a liquid fueled rocket would need.
Today's missile systems are much more than a rocket engine with a supply of fuel and oxidizer. There is usually some sort of payload. This can be a test package or a bomb. The missile will have some sort of guidance system to get it to its target and it has an airframe to hold all the parts together.
The Missile Park at White Sands Missile Range has a wide range of missile airframes on public display. They include a V-2 along with missiles used by the U.S. Army, Navy and Air Force.
For the future scientists are looking for other types of rocket engines to replace the chemical ones now used. Any self-contained system which can push matter out an opening will produce push or thrust. Therefore, even a balloon could be considered a rocket.
One idea researchers are looking at is using a nuclear reactor to heat a gas so it expands and becomes pressurized. The gas can then be forced through a nozzle which would create the necessary opposite action to drive a vehicle forward.
Scientists also have contemplated using an ion beam to push a spacecraft. This system calls for accelerating charged molecular particles in magnetic fields and then beaming them out the nozzle end of the engine. Another plan calls for thrust to be provided by ejecting photons or light from the engine.
These devices are theoretically possible but they lack the powerful thrust necessary to escape earth's gravity pull. Since the turn of the century, the rocket motor has gone from being a firework and little used weapon to being the key to man's dreams. The rocket has made space exploration possible. Men have already walked on the moon and exploratory spacecraft have flown past the planets in the solar system, sending back valuable information. The rocket is the key to open up new worlds for Man to explore.
|Ref.: #57 - update: 3.11.01||Home|