Early visions of human space flight spanned centuries and continents. In 1929, Austrian Army officer Hermann Noordung envisioned and designed a multi-component space station in orbit around Earth. Its three parts consisted of a disk-shaped habitat with a large solar mirror, a dish-like machine room suspended some distance away, and a smaller can-shaped astronomical observatory.

"Space Travel is Utter Bilge"

So said astronomer Sir Richard Wooley in 1956. In 2002, a JPL scientist pays tribute to the visionaries who, in the face of skepticism and gravity, opened the way to interplanetary flight

By Donald Yeomans

Until a few decades ago, interplanetary travel was the stuff of dreams and fantasy. But it was a fantasy in which the dreamers often turned out to be uncannily farsighted and correct, while the predictions of some eminent scientists proved to be far too conservative. Successful space travel would actually come about, in large part, through the efforts of engineers and scientists who were also dreamers. In the end, it would be a handful of these individuals, existing on the fringe of contemporary science, largely ignored and sometimes derided by the “experts” of their day, who carried forward the torch of interplanetary travel and manned space flight. For centuries, they predicted that an era would come when mankind would venture into space. That fortunate era is now.

While the conquest of the skies via heavier-than-air vehicles did not arrive until the Wright brothers’ historic flights in 1903, earlier dreamers needed only to point to the birds to demonstrate that the air would one day support human flight. But travel to the space beyond Earth was only accessible through their flights of imagination.

Johannes Kepler

Early in the 17th century, the noted astronomer, Johannes Kepler, penned a treatise entitled “The Dream” (Somnium), in which the central character, Duracotus, takes a voyage to the moon. The story is based loosely upon Kepler’s own life, and the lunar voyage is facilitated by Duracotus’s mother. She is in league with lunar demons that can, on occasion, provide the necessary transportation to the moon. Once in space, Duracotus protects himself from the rarefied air by applying damp sponges to his nostrils, while noting that the pushing supplied by the lunar demons is no longer necessary once he has ascended beyond Earth’s orb. Kepler, who would be remembered for his laws of planetary motion, did not dare publish the book during his lifetime. However it was read in manuscript form and was partially responsible for his mother’s being tried as a witch. Fortunately, she was freed in October 1621 after spending 14 months in custody.

The English bishop Francis Godwin published another lunar fantasy entitled The Man in the Moone in 1638. Its hero, a shipwrecked mariner named Domingo Gonzales, wishes only to escape the uninhabited island on which he is stranded. He trains a flock of 30 wild swans to fly him back to civilization but the birds’ migration season has begun, and their home turns out to be . . . on the moon. After a 12-day voyage, our hero arrives at the moon to find the inhabitants there to be much larger than those on Earth. The lunarians are an average of 28 feet tall. Despite his puny stature, Domingo is well-treated by the lunarians and after enjoying their company, he returns to Earth safely, although two of his 30 swans have died and the rest “began to droope.”

In 1827, in an early example of American science fiction, George Tucker, writing under the pen name Joseph Atterlay, wrote “A Voyage to the Moon.” The spacecraft was a copper vessel loaded with scientific equipment and powered by lunarium, an anti-gravity metal with no more validity than wild swans.

Konstantin Tsiolkovsky

It was a Russian schoolteacher, Konstantin Tsiolkovsky, who would be the first to seriously consider realistic means for achieving space flight. Born on September 17, 1857, 100 years and 17 days before his countrymen launched Sputnik, Tsiolkovsky contracted scarlet fever as a child and became nearly deaf. Unable to attend the local schools, he began an intensive course of self-study into the natural sciences. In 1879, he passed his teaching examinations without having attended any of the lectures and began teaching outside Moscow in Kaluga province. What spare time he had was devoted to research into aeronautics.

At age 26, he published a short treatise entitled “Free Space” and stated that the path to space was through rocket propulsion. Rockets were certainly not a new concept, having been invented by the Chinese by the thirteenth century, but Tsiolkovsky was the first to note that only rockets could serve the needs of space travel. He is also credited with a variety of forward-thinking ideas on space flight, including a theory of rocket travel that took into account the rocket’s changing mass; the use of liquid hydrogen and oxygen for rocket fuel; multistage launch vehicles; the effects of atmospheric drag and solar light pressure on space vehicles; the nature of weightlessness in space; and geosynchronous orbits, whereby a satellite could always remain above a single location on the Earth’s surface.

Did Tsiolkovsky’s advanced ideas find easy acceptance or support? They did not. Up to the time of the Russian Revolution in 1917, he was either ignored or considered a crazy inventor and rootless dreamer by the recognized scientific community of tsarist Russia. However, his ideas for using technology to overcome gravity meshed with the Marxist philosophy that machines are indispensable to the construction of Communist society. Thus in 1919, the now-ruling Communist Party yanked Tsiolkovsky from obscurity and appointed him to the Socialist Academy, which later became the Soviet Academy of Sciences. In 1921, at the age of 64, he was given a personal pension, which allowed him to devote himself entirely to his scientific research. While he still worked alone, he now had government assistance to publish his works and to republish some that had appeared earlier as very limited issues published at his own expense. In the 1920s his work on space flight began to receive international recognition.

There are many similarities between Tsiolkovsky’s life and that of the American rocket pioneer, Robert Hutchings Goddard. Goddard also worked in relative obscurity, and he did not receive the credit due him until after his death in 1945. Like Tsiolkovsky, Goddard taught school—he was a professor at Clark University in Massachusetts. But whereas Tsiolkovsky never attempted to actually build a rocket, Goddard developed and flew various rockets, as well as conceiving many new ideas in the theory of rocket flight.

Goddard published the first of two important monographs in the January 1920 Smithsonian Miscellaneous Collections. In a slim paper entitled “A Method of Reaching Extreme Altitudes,” he discussed his theories and experiments concerning the efficiency of the ordinary rocket. He provided calculations on the minimum rocket mass needed to raise one pound to various altitudes in the atmosphere and calculations on the minimum mass required to raise one pound to escape the earth. In an effort to demonstrate that a rocket could escape Earth and reach the moon, Goddard had worked out how much flash powder an observer on Earth would see through a one-foot aperture telescope when the rocket crashed into a dark region of the lunar surface. But he was completely unprepared for the publicity that greeted this scenario. The press termed him the “moon man,” and made him the butt of jokes. Never an outgoing person to begin with, Goddard responded by withdrawing further into professional and private seclusion, so that his work was generally not well known during his lifetime.

Goddard demonstrated the first flight of a liquid fuel rocket in Auburn, Massachusetts in March 1926. The rocket reached an altitude of 41 feet and covered a mostly horizontal distance of 184 feet, roughly comparable with the distance covered by the second flight of the Wright brothers’ airplane in 1903. Like Tsiolkovsky before him, Goddard realized the liquid-fuel rockets were more efficient than those powered with dry, or solid, fuels. The 1926 rocket flight was documented ten years later as part of Goddard’s second significant publication entitled “Liquid-Propellant Rocket Development.”

Goddard’s extraordinary achievements did not go entirely unnoticed. The aviator Charles Lindbergh and the secretary of the Smithsonian Institution, Charles Abbot, were influential in helping him secure a $50,000 grant from the Guggenheim Fund for the promotion of aeronautics. Using this substantial award, Goddard, his wife, and four assistants established a research area near Roswell, New Mexico. There in the desert, between 1930 and 1941, they undertook one of the most amazing lone-wolf efforts in the history of technology. In tests conducted at this site, Goddard’s liquid-fuel rockets reached speeds of 700 mph and altitudes above 8,000 feet. His innovations included the use of fuel- injection systems, regenerative cooling of combustion chambers, gyroscopic stabilization and control, instrumented payloads and recovery systems, guidance vanes in the exhaust plume, gimbaled and clustered engines, and aluminum fuel and oxidizer pumps.

American rocket pioneer Robert
Goddard in 1915, standing beside
one of his early liquid-fueled rockets.

By the early 20th century, the works of Tsiolkovsky and Goddard had clearly shown that space flights were theoretically possible. Assuming that a sufficiently powerful rocket-thruster could be developed, Isaac Newton’s 17th-century formulation that for every action there is an equal and opposite reaction provided the basis for rocket flight. Nevertheless, there continued to be a commonly held belief in the impossibility of flying a rocket in space, where “there was nothing for the rocket to push against.” Many who did understand that rockets need not push on anything simply denied that rocket technology would ever advance to a point where enough power could be generated to achieve the 11.2 km/s velocity required to escape the earth’s gravity.

Fortunately, none of these objections was enough to deter a new generation of dreamers, many of them in Germany, who, like Goddard, combined technical training and expertise with a commitment to furthering the possibilities of space flight.

One of them was Hermann Oberth, who from boyhood was fascinated by the possibility of space travel. By 1920, he had derived the formulas for calculating the impulse necessary to achieve escape velocity. Born in Transylvania Hungary, in 1894, Oberth produced a treatise on rockets and interplanetary travel as his doctoral dissertation at the University of Heidelberg. But since neither his advisor, the well-known astronomer Max Wolf, nor anyone else on the faculty would declare themselves competent in this subject, he was unable to submit it for a degree. His thesis was also rejected 20 times by various publishers before the firm of Oldenburg agreed to issue it, with the proviso that Oberth pay for the printing costs himself. Today The Rocket into Interplanetary Space is recognized as a classic in the early theory of space flight. In it Oberth established that a rocket could operate in a void and could travel faster than the velocity of its own exhaust. He also discussed the merits of alcohol and hydrogen as rocket fuels and outlined a type of rocket that he felt could be used to explore the upper atmosphere.

In the only section that was relatively free of complex equations, Oberth dealt with the physiological and psychological problems of manned flight, including acceleration, weightlessness, loneliness, and claustrophobia. He also discussed the possibilities for satellites, space stations, and space mirrors that could beam sunlight to the dark side of the earth.

Like Tsiolkovsky and Goddard before him, Oberth had been inspired as a youth by the rich stories of Jules Verne, particularly by Verne’s 1865 work From the Earth to the Moon. Unlike them, he worked hard to publicize rocketry in general and his own work in particular. In 1930, he became a technical advisor to the Fritz Lang movie Girl in the Moon. As a publicity stunt for the film, Oberth and his assistants were asked to design, build, and launch a rocket. For all his theoretical genius, Oberth was not a rocket engineer and, like the movie itself (a silent film in an era of talkies), the rocket was unsuccessful. It never left the ground.

In the 1920s, while the work of Oberth in Europe was being discussed within a small circle of followers, and the work of Goddard was closely followed by an even smaller group of American dreamers, the general public remained mostly unaware of the work being done to free the human race of the earth’s grasp. In Germany, however, the spark of interplanetary travel continued to be fanned by two other dreamers—Walter Hohmann and Hermann Noordung.

Hermann Oberth

Born in 1880, Hohmann became the city architect in Essen, near the German-Dutch border, in 1912. While his day job was that of a civil engineer, he spent all his free time investigating the possibilities of space travel. His The Attainability of the Heavenly Bodies, published in 1925, was prescient for the ideas it advanced, and many of them seem remarkably modern even today. Among them are the variable-pitch wing for dynamical control of the spacecraft during landing, the use of nose cones and parachutes for successful landings, the manufacture of rocket fuel from planetary resources to save weight, and the use of a surface lander that would detach from a planetary orbiter. However, Hohmann is best-remembered for what is known today as the Hohmann trajectory—the formulation that the optimal energy transfer orbit between planets is an ellipse that is just tangent to the orbits of both planets.

Ironically, Hohmann, who did not participate in the intensive rocket development projects in Germany during World War II, was killed in an allied bombing raid on Essen in 1945, just two months before the war ended.

Hermann Noordung, whose real name was Herman Potocnik, was an Austrian army officer. Although his life was cut short by tuberculosis in 1929 (he was 38), the year of his death saw the publication of his classic The Problem of Space Travel. Though much of the book was based upon Oberth’s 1923 work, Noordung proposed an impressive number of innovative ideas, particularly with regard to space stations. He suggested placing a space station in geosynchronous orbit and using air locks and space suits for walks in space. He also envisioned radio communication between Earth and space stations, and suggested that momentum wheels could be used to maintain control of a spacecraft’s orientation in space. Finally, Noordung proposed several possible uses for a space nation: as a site for doing physical and chemical experiments in the absence of gravity and heat; as an astronomical observatory above Earth’s atmosphere; and as a platform for a parabolic space mirror for weather control and military advantage.

In 1927, Oberth, Hohmann, Wernher von Braun, Willy Ley and other German space enthusiasts formed the Society for Space Travel (Verein für Raumschiffahrt, or VfR). Among the research efforts they discussed were those of Robert Goddard, and their goal was to work toward the day when their rocket technology could be used to send spacecraft to explore the solar system. However, this club of rocket enthusiasts was operating at the margins: their research was largely self-funded and their rocket experiments did not initially attract the kind of governmental support needed to get past the hobbyist stage.

Three years later, across the Atlantic, a group of journalists founded the American Interplanetary Society. Partly as a result of the ridicule aroused by the mention of interplanetary travel, the group soon changed its name to the American Rocket Society; it eventually evolved into today’s Institute of Aeronautics and Astronautics. As with its German counterpart, funds were shorts, accidents in the course of experiments frequent, and the group struggled for a time to survive. The reclusive Professor Goddard was not even an active member.

While it would be nice to outline a scenario whereby the fledgling German and American rocket enthusiasts succeeded in convincing their governments to support research toward space flight, the reality was far different. The sponsor who ultimately stepped up to push and pay for the serious development of rocket flight was the German army. In 1932, the Army hired a number of VfR members, including Von Braun, and put them to work in the military’s rocket artillery unit. Von Braun was soon put in charge of an expanding rocket-building program, and when Hitler and the Nazi Party took over the government in 1933, he was assigned the task of overseeing long-range missile system development. Over the next dozen years, he would become the leading technical engineer for the Nazi rocket program at Peenemunde, Germany.

Back in the United States, as nervous observers watched these developments, Robert Goddard accepted some military contracts to continue his work on rocketry. It was within Germany, however, that the most rapid strides were taken to develop a long-range and reliable liquid fuel rocket, culminating in the V-2 (Vengeance) rockets that Hitler fired into England in the waning months of the war. It has been pointed out that the 25,000 slave laborers, forcibly transported to Germany from all over occupied Europe, who perished in hellish conditions while building the V-2s at the underground Mittelwerk (Dora) concentration camp were ten times greater in number than the British civilians killed during the V-2 attacks. Von Braun’s role in this program has been called into question on more than one occasion. A high-ranking Nazi party member, he also held the rank of major in the SS. Nevertheless, with an allied victory assured in May 1945, he and his brother Magnus surrendered to the American military with the expectation that their expertise would be considered extremely valuable to the United States. And indeed, the United States made extraordinary efforts to ensure that the cream of the Nazi rocket scientists would remain in American rather than Soviet hands once the war was over. To many, the Cold War already seemed imminent, and the American military was counting on its captured German rocket scientists to develop the next generation of weapons delivery systems.

Whatever his principles, von Braun had unquestioned leadership abilities and an unparalleled grasp of the art of rocket building. The U.S. army put him to work developing rocket-launch vehicles, but his dream of using rockets for space flight was to be shelved until the American public and Congress demanded a response to the Soviet Union’s launch of Sputnik in October 1957. Working in relative obscurity, the Soviet chief rocket designer Sergei Korolev had helped develop an impressive missile program. He and his colleagues too were aided by some expert Germans engineers from Peenemunde.

The USSR would successfully put yet another satellite into Earth orbit on November 3, 1957 (this time carrying a dog named Laika) before the United States successfully launched its own Earth-orbiting satellite, Explorer 1, on January 31, 1958. In a harbinger of things to come, Explorer’s key components were a launch vehicle developed by von Braun’s team and a satellite built under the direction of William Pickering ’32, PhD ’36, the director of Caltech’s Jet Propulsion Laboratory. The satellite carried a charged-particle detector developed by James van Allen. This instrument detected charged particles ensnared in the earth’s magnetic field, a region now known as the Van Allen radiation belts.

Von Braun’s contemporary Hermann Oberth had not played an active role in the development of the V-2 rocket during the Second World War, but he was hired by von Braun in 1955 and worked for the U.S. Army for a time, before returning to Germany in 1959. He died in 1979, having lived long enough to see his dream of space travel become a reality.

The great rocket pioneer Robert Goddard had died four days before the end of World War II, but with the dawn of the space age, he was at last accorded the recognition he deserved. NASA’s Goddard Space Flight Center was dedicated on May 1, 1959. The following year, the United States government awarded Goddard’s widow, Esther, $1 million in settlement for the government’s use of more than 200 of Goddard’s patents for rocket hardware.

The race to outer space was on. In 1961, President Kennedy committed the United States to landing a man on the moon “and returning him safely to Earth” by the end of the decade. The successful Apollo program was the result, an effort initiated primarily for political posturing but nevertheless achieving superb scientific goals.

With the close of the 20th century, our generation has been privileged to witness several lunar landings and the continued opening of the solar system frontiers, with the exploration of eight of the nine planets and dozens of natural satellites, comets, and asteroids.

“Centuries hence,” the scientist and science writer Carl Sagan once wrote, “when current social and political problems may seem as remote as the problems of the Thirty Years War are to us, our age may be remembered chiefly for one fact: It was the time when the inhabitants of the Earth first made contact with the vast cosmos in which their small planet is embedded.”

Indeed, we are living in that privileged era that Tsiolkovsky, Oberth, Hohmann, Noordung, Goddard, and other visionaries hoped would one day come.

Donald Yeomans is a JPL senior research scientist and supervisor of the Lab's Solar Systems Dynamics Group. He's also manager of NASA's Near-Earth Object Program office, and, as such, his is often the voice that the public hears reassuring them (thus far) that the latest Earth-crossing asteroid to be spotted is not on a collision course with our planet. A writer and rare-book collector as well as a scientist, he combined these roles in his 1991 book Comets: A Chronological History of Observation, Science, Myth, and Folklore, and he has written and lectured frequently about the history of space science.