Space Travel Enters the Scene

Rockets have long been associated with science fiction stories. After all, what is science fiction all about if not rocket ships zooming to other planets? But it is less known that science fiction authors associated rockets with space travel long before scientists and engineers did.

The first person to describe the use of rockets in space travel was the French author Jules Verne (1828-1905). In his 1865 novel From the Earth to the Moon, Verne describes a spaceship using rockets to change its course. Verne had realized an important fact about rockets that had escaped even most scientists: they would work in a vacuum (a space without air or gas).

Most people, including scientists and engineers, believed that rockets worked by pushing against the air behind them. This was a misconception that lasted well into the twentieth century. In fact, many of the early rocket experimenters were hampered by a lack of support from both the scientific community and the public. This is because the public didn't know that rockets don't need something to push against and that spin. Just as a spinning top will resist being pushed over, a spinning bullet or rocket will resist being turned from its path.

Meanwhile, however, improvements to guns and cannons had increased their range and accuracy. They far exceeded the effects of rockets. Most countries began disbanding their rocket corps. By the time Hale had made his improvements, there was little interest in rockets in Europe. (A few countries, such as Russia, Austria, and France, continued to use Congreve-type rockets.)

The United States, on the other hand, had just entered its Civil War (1861-1865). This was the most technologically advanced war to that time. The Northern government showed much enthusiasm for Hale rockets. The rockets came in two sizes. The one that saw the most service was the largest: 3.3 inches (8.3 cm) in diameter with a therefore can work in the vacuum of space.

Rocket propulsion is the only type of propulsion that will work in outer space. In fact, rockets work better in a vacuum than they do in an atmosphere like Earth's. This is because air actually gets in the way of the exhaust, keeping it from achieving its full velocity.

Jules Verne (1828-1905) was one of the most popular authors of the nineteenth century and is still a best-selling author more than a century after his death.

weight of 16 pounds (7.2 kg). Made of cast iron, the rocket had a range of 2,200 yards (2,012 m). Like Congreve's rockets, the Hale rockets were launched from tubes or troughs supported by portable stands. The rockets were eventually used by the North and the South during the war.

Rockets continued to be used sporadically and unenthusiastically by armies and navies around the world for the remainder of the nineteenth century. But the U.S. Civil War was essentially the last gasp for the weapon. By then the accuracy and firepower of cannons had far exceeded the capability of the unreliable rocket, which usually had to be fired in large numbers to ensure hitting anything at all. An entirely new type of rocket was needed, but that had to wait until the dawn of the following century.

^HKonstantin E. Tsiolkovsky was born in Russia in 1857, the son of a forester (and unsuccessful inventor) and a mother who came from a family

pq H

of artisans. When he was ten years old, a bout with scarlet fever left him deaf. This made it difficult for him to attend school, so he studied at home. He read books constantly, especially books about mathematics and physics.

He did so well that in spite of his handicap, he was offered a job as a teacher at the age of nineteen. He remained a teacher, working at several different schools, until he finally retired. Tsiolkovsky never lost his interest in science and research, however. Every day, after his teaching duties had been completed, he hurried home to work on his own projects. One of these involved exploring outer space.

Tsiolkovsky knew that an ordinary motor could not propel a vehicle between planets. This is because there is no atmosphere in space (and therefore no oxygen). Steam engines and internal combustion engines require a source of oxygen. And, of course, propellers would not work in a vacuum, either. Tsiolkovsky realized that the only propulsive force that could move a i\* ■ mi

The experiments of American physicist Robert Goddard (above) in the early 1900s resulted in the construction and launching of the world's first liquid-fuel rocket in 1926.

Konstantin E. Tsiolkovsky, who theorized about the building of a liquid-fueled rocket in the late 1800s, published his ideas in

1903

vehicle in space would be one that operated on the principle of recoil. And that meant rockets.

Tsiolkovsky recognized that the ordinary gunpowder rocket, which had been used for more than one thousand years, would not work. A solid-fuel rocket flies when the gases produced by burning gunpowder shoot at high speed from the rear of the rocket. Just as with anything else that burns, gunpowder requires oxygen. When you light a match, it burns because its fuel combines with oxygen in the atmosphere. Gunpowder, however, contains its own oxidizer.

Oxygen forms a large part of potassium nitrate, which readily releases some of the oxygen when heated. This oxygen is then free to combine with other materials, such as a fuel. But this system could not achieve the velocities required for space travel. A more efficient fuel was needed.

Tsiolkovsky suggested using two liquids, kerosene and liquid oxygen, for example, or liquid hydrogen and liquid oxygen. This would require an entirely new type of rocket, one that carried its fuel and oxidizer separately. The two liquids would then be forced into a small, enclosed space—a combustion chamber—and ignited. If one end of the chamber opened into a nozzle, the resulting blast of hot

Early

Improved

solid-fuel

solid-fuel

rockets

rockets

were

have a

solidly

hollow

packed

core that

with fuel.

allows the fueito

Tills

bum more

resulted

evenly.

in uneven

burning

and

erratic

flights.

gases would propel the rocket.

One of the advantages of the liquid-fuel rocket is that it is not only more powerful than the old solid-fuel gunpowder rocket but it can be controlled. Because the fuel and oxidizer are separated and fed into the motor, the thrust of the rocket can be adjusted by allowing more or less fuel to flow into the combustion chamber. This is similar to the way a driver adjusts the speed of an automobile by changing the amount of fuel and air reaching the engine. A liquid-fuel rocket can even be turned off and restarted. A gunpowder rocket cannot.

Tsiolkovsky finished his first paper containing his ideas regarding rockets in 1898. He submitted it to a scientific journal, and it was finally published in 1903. Unfortunately, the journal was published in Russian, a language that virtually no one outside Russia was then familiar with. Few scientists outside the country ever read Tsiolkovsky's theories. This lack of attention did not deter Tsiolkovsky, however. He persevered in his studies, producing an entire series of articles—and even a science fiction novel—outlining his thoughts about rockets and space travel. Still, all of these were published in Russian and

The first rockets used a solid propellant that combined fuel and oxygen. In the earliest rockets, this was gunpowder. To keep the propellant from burning irregularly (left), most solid-fuel rockets have a hollow core (right) for more even burning.

were little known to the outside world.

Fortunately, several important events occurred in the meantime. Two other teachers—one in the United States and one in Europe—also became interested in rockets and space travel. Neither knew about Tsiolkovsky or each other. One of the teachers was Robert Hutchings Goddard, a physics professor at Clark College in Worcester, Massachusetts. The other was a quiet mathematics teacher named Hermann Julius Oberth, who lived in the mountains of Transylvania, part of modern Romania.

To the Moon with Professor Goddard

Robert Goddard sent a short thesis he had written about rockets to the Smithsonian Institution in Washington, D.C. The sixty-nine-page booklet, A Method of Reaching Extreme Altitudes, was published in 1919. In his first sentence, Goddard explained that he had been led to write the booklet as a result of his search for a method of sending scientific recording instruments to heights beyond those of balloons—or higher than 20 miles (32 km). This search, the booklet said, "led the writer to develop a theory of rocket action."

Most of the booklet discussed ways in which rockets could carry instruments into the upper atmosphere. At the end, Goddard mentioned that it would be possible for a rocket to actually carry a payload to the Moon. He speculated that a rocket could perhaps carry a quantity of flash powder (a powder containing magnesium that

photographers once used to take flash pictures). This could be seen by astronomers on Earth when it exploded on impact.

Goddard came to regret that he made this prediction. While Tsiolkovsky's remarkable theories were largely overlooked, Goddard's little booklet immediately made headlines from coast to coast. His final statement about sending a rocket to the Moon was especially newsworthy.

The shy physics professor made headlines in newspapers around the country. "Modern Jules Verne Invents Rocket to Reach the Moon" shouted the Boston American. "Claim Moon Will Soon Be Reached," blazoned the Milwaukee Sentinel. "Savant Invents Rocket Which Will Reach Moon" declared Popular Science magazine. Of course, Goddard had not done so. He had only suggested that a rocket might someday reach the Moon. Goddard even received an offer from Hollywood asking if he would include a message from a popular film star in his rocket.

The worst blow came from the venerable New York Times. Following the headline, "Believes Rocket Can Reach the Moon," was an editorial that claimed that Goddard was simply ignorant of the basic laws of physics. Goddard's rocket, the writer asserted, simply would not work. "That Professor Goddard ... does not know the relation of action to reaction, and of the need to have something better than a vacuum against which to react—to say that would be absurd. Of course, he only seems to lack the knowledge ladled out daily in high schools."

Criticisms such as this stung Goddard deeply. He was especially bothered by the accusation that he was capable of making a fundamental error in physics. The idea that a rocket flew by pushing against the air behind it was a common one that even many scientists believed. In fact, a rocket moves by the reaction occurring within it. It travels forward because its exhaust is traveling in the opposite direction. The faster the exhaust is ejected—the "exhaust velocity"—the faster the rocket will go.

Rather than helping make a rocket go, the presence of air actually slows it down. The air gets in the way of the exhaust. A rocket will not only work in a vacuum—as Goddard knew perfectly well—it works better in a vacuum. This public humiliation caused Goddard to retreat behind a wall of secrecy. Few people after that learned about the work he was doing.

Goddard was a skilled engineer and machinist who actually built the rockets he proposed. (Tsiolkovsky and Oberth were pure theoreticians and never actually built any of the rockets they wrote about.) Although Goddard had been talking about solid-fuel rockets in his Smithsonian booklet, he began considering the potential of liquid fuels. He wanted to design, build, and fly these rockets. But he realized perhaps more than either of the other scientists how difficult this would be.

The primary problem was how to get the oxidizer and fuel into the motor. A solid-fuel rocket, such as a skyrocket, is basically one piece—the fuel and nozzle is directly connected. The liquid-fuel rocket requires that the fuel and oxidizer be kept in separate tanks. These tanks are kept separate from the combustion chamber where the liquids are to be burned. When combustion takes place, Goddard realized, it creates tremendous pressures inside the combustion chamber. How would he be able to force liquid fuel and oxidizer into the motor against this pressure? Liquid fuels would also require plumbing, valves, and other equipment, in addition to their tanks. All would add weight to the rocket.

Goddard chose liquid oxygen for his oxidizer. After a little experimentation, he settled on gasoline for his fuel because it was igniter igniter rocket motor valves gasoline line liquid oxygen tank liquid oxygen line support for launch exhaust shield support for launch liquid oxygen tank

exhaust shield

Goddard's first liquid-fuel rocket (1922) was a very simple device, hardly recognizable as a rocket. The motor was at the top, supported by the pipes carrying fuel and oxygen from the tanks below.

cheap and easy to obtain. The pressure created inside the combustion chamber by the burning fuel would be at least several hundred pounds per square inch (kg/cm). Therefore, he would have to force his oxidizer and fuel into the motor at a higher pressure.

The obvious solution would be to use pumps. At first he devised a small, high-pressure pump. But his later experiments used pressure. Goddard added an inert gas—a gas that didn't combine with the fuel or oxidizer—under high pressure to his tanks. The pressure of this gas forced the liquids into the motor.

Goddard tested his first liquid-fuel rocket motor in 1922. He was not happy with the results and began making improvements. His second motor was not ready until 1925. This motor, too, proved disappointing in its tests, so he made yet another one. Finally, in 1926, he believed that he had a motor good enough for a test flight.

On March 16, 1926, Goddard took his rocket and its launching

frame to a snowy, open field on a farm owned by one of his relatives. He was accompanied by his wife and two men from his college. The "rocket" Goddard constructed would scarcely be recognizable in modern times. It was little more than a fragile-looking framework of thin pipes connecting the fuel and oxidizer tanks to the motor.

Launching the rocket was simple. The fuel and oxidizer valves were opened while Goddard's assistant, holding a blowtorch attached to a short pole, held the flame under the rocket's nozzle. The motor erupted with a shrill roar, and the rocket lifted from its frame. After only two and a half seconds, its fuel exhausted, the rocket dropped backto the ground. It had traveled a distance of 184 feet (56 m) and achieved a speed of about 60 miles (97 km) per hour. This is unimpressive even by the standards of a small gunpowder skyrocket. But still, it was the flight of the world's first liquid-fuel rocket.

Unfortunately, Goddard had been badly stung by the publicity surrounding his original paper. He did not announce the successful flight of his rocket until about ten years later. Meanwhile, experimenters in Europe—unaware of what Goddard had accomplished— were making progress too.

Facing page: Henry Sacks, Goddard's assistant, ignites the motor of the first liquid-fuel rocket in 1926.

Was this article helpful?

0 0

Post a comment