Date: Beginning October 4, 1957
Definition: The first man-made satellite to orbit Earth.
Significance: The launching of Sputnik 1 demonstrated that artificial satellites could be placed into orbit and transmit radio signals to Earth, opening the era of space exploration.
Early History of the Sputnik Program
The launching of the first man-made, Earth-orbiting satellite traces its history back to 1946, when Premier Joseph Stalin ordered the beginning of the Soviet Union’s postwar rocket program. Soviet aeronautical engineer Sergei Korolev, later known as the father of the Soviet space program in the 1950′s and 1960′s, was appointed chief designer. Initially Korolev’s group flew captured German V-2 rockets from Kapustin Yar, near Volgograd. Korolev, like many of his contemporaries, envisioned huge rockets that could be used for the exploration of space. However, political leaders could justify the large expense of a rocket development program only as part of a military system. The development of the atomic bomb required the construction of a long-range delivery system, either a long-range bomber or an intercontinental ballistic missile (ICBM). The first Soviet Earth-orbiting satellite came about as a result of both the interest of Korolev in exploring space and the interest of the Soviet premiers, Stalin and later Nikita Khrushchev, in having a rocket to deliver atomic bombs to the United States.
Sputnik’s R-7 Rocket
Korolev’s group developed the Soviet ICBM, a missile called the R-7. The design of the R-7 rocket remained secret until 1967, when the Soviet Union displayed the rocket at the Paris Air Show.
The R-7 is a one-and-one-half-stage ballistic rocket, measuring about 68 feet tall and about 34 feet across at its base. It consists of a central core surrounded by four strap-on booster rockets. The core of each of the strap-on booster rockets is a cluster of four rocket engines. At liftoff, the R-7 rocket employs twenty rocket engines, each generating 55,000 pounds of thrust, firing simultaneously. The liftoff thrust is more than 1 million pounds. When the four strap-on booster rockets exhaust their fuel, they drop off, leaving the four engines of the central core to provide the final thrust to deliver a warhead to its target or a satellite to orbit. The basic R-7 rocket can place about 3,000 pounds into a low orbit around the earth.
The R-7 rocket was successfully tested as an ICBM for the first time on August 27, 1957. It was used in unmodified form to launch the first three Sputnik satellites. As it became necessary to launch heavier satellites, a second stage was added to the R-7 to improve its performance.
The First Sputnik Satellite
Even before the R-7 rocket was test flown, Korolev suggested, in a secret memo to the Soviet government in 1954, the possibility of launching a satellite. Later, Korolev’s group proposed to the Soviet National Academy of Sciences the possibility of launching an Earth-orbiting satellite using the new rocket. The International Geophysical Year, an eighteen-month period in 1957 and 1958 dedicated to the scientific study of the earth, provided the opportunity. Scientists recognized that many geophysical questions couldbe investigated only through the use of satellites. A satellite couldbe used to determine the density of the atmosphere high above the earth and could serve as a sensitive probe of the mass distribution in the earth, and satellite-borne instruments could monitorboth radiation in space and the strength of the earth’s magnetic field.
After Korolev was given the go-ahead to launch an Earth-orbiting satellite, a team to build the satellite was established. The satellite team set to work designing and building an ambitious, 3,000-pound satellite carrying an array of scientific instruments. This complex scientific satellite project fell behind schedule, and it appeared to Korolev that the R-7 rocket would be ready to loft the first satellite before there was a satellite ready to launch. Because the United States had announced its own plans to launch a satellite, it became imperative for the Soviets to launch their satellite as soon as possible.
Korolev’s rocket design group decided to design and build a simple satellite in their own facility, in order to have something to launch when the R-7 was ready. In just two months, Korolev’s group assembled what became the world’s first artificial satellite, named “Sputnik,” the Russian word for “traveler.” This first Sputnik was simply an engineering test satellite that carried no scientific research instruments.
The R-7 rocket carrying Sputnik 1 lifted off from the Tyuratum Launch Facility on October 4,1957. During the launch, Sputnik 1 was housed inside a protective nose cone on top of the R-7 rocket. After the core rocket had reached an altitude of 142 miles and a speed of 26,249 miles per hour, the rocket shut down, and Sputnik 1 was in orbit. The orbit was highly elliptical, with a low point of 142 miles and a high point of 588 miles above the earth’s surface. Sputnik 1 circled the earth once every 96.2 minutes. Because its orbit was inclined about 65 degrees from the equator, Sputnik 1 traced out a path over the globe that took it over most of the populated regions of the world once every day.
Sputnik 1 was spherical in shape with a diameter of 22.8 inches and a weight of 184 pounds. The spherical shell was made of an aluminum alloy, and the interior was filled with nitrogen, a gas that would not condense even at the cold temperatures in space. At launch, four communications antennae, each about 9 feet in length, were folded to allow the satellite to fit into the nose cone of the R-7 launch vehicle. After Sputnik 1 was placed in orbit, the nose cone was jettisoned, the antenna were deployed, and the satellite separated from the core rocket. Sputnik 1 had two radio transmitters, working on frequencies of about 20 megahertz and 40 megahertz.
The temperature inside the aluminum shell of Sputnik 1 was monitored using sensors that produced small changes in the transmitter frequency with temperature. It was not known how much the temperature inside the satellite would vary as the Sputnik traveled from the sunlit to the dark side of the earth in a cycle that repeated every 96 minutes. These temperature measurements provided information on the design changes that might be needed on future satellites to maintain a uniform interior temperature.
The core rocket that carried Sputnik 1 remained in orbit for sixty days. The Sputnik 1 satellite remained in orbit for ninety-four days, although its batteries had drained and the transmitter had ceased to function after twenty-one days.
Although Sputnik 1 was designed only as an engineering test satellite, it did produce useful scientific results. The aerodynamics of spherical objects were well understood, so the rate at which the orbit of Sputnik 1 decayed as a result of air drag provided the first measurement of the air density at the orbital altitude. These measurements indicated that the air was ten times more dense than some scientists had previously modeled. In addition, the properties of the ionosphere, the upper region of the earth’s atmosphere, were examined by monitoring how the 20- and 40-megahertz radio signals from the transmitters on Sputnik 1 were altered during passage through the upper atmosphere.
Sputnik, launched by the Soviet Union on October 4, 1957, was the first artificial satellite to orbit Earth.
The First Scientific Sputniks
Sputnik 2, launched on November 3,1957, was the first Earth-orbiting satellite to carry a full complement of scientific instruments. Sputnik 2, which weighed 1,118 pounds, was conical in shape, measuring about 12 feet long and about 6 feet in diameter, to maximize the use of the space available inside the R-7′s conical nose cone. Sputnik 2 was placed into a highly elliptical orbit, coming within 140 miles of the earth’s surface at closest approach and going out to 1,038 miles from the earth’s surface, circling the earth once every 104 minutes.
The major purpose of Sputnik 2 was to study the effects of space travel, particularly weightlessness, on animals. The Soviet Union had previously launched animals, including dogs, on high-altitude rocket flights, providing extensive information on the response of animals to the liftoff acceleration. On previous rocket flights, however, weightlessness had lasted for only brief periods of time.
Sputnik 2 carried an 11-pound dog, named Laika, into orbit. The monitors on Sputnik 1 had already demonstrated that the interior temperature could be maintained in a range suitable for survival. However, the nitrogen atmosphere of Sputnik 1 was unsuitable to support life. To provide a suitable atmosphere, Soviet scientists used a system of reactive chemicals to give off oxygen for Laika to inhale and another chemical system to absorb the carbon dioxide that Laika exhaled. Information on Laika’s physical condition was radioed to Earth, and Soviet scientists concluded that animals could withstand weightlessness during orbital flight. Because the technology did not exist in 1957 to return Sputnik 2 and its passenger, Laika, to Earth, the dog was put to death by an injection of poison after providing seven days of biomedical data. Sputnik 2 fell from orbit on April 14, 1958.
Sputnik 2 also contained instruments to monitor the amount of solar and cosmic radiation penetrating the spacecraft’s walls. The intensity of this radiation in orbit had not been known before Sputnik 2. This flight demonstrated that sufficient shielding could be provided by spacecraft walls in order to allow the short-term survival of animals in space.
Sputnik 2 demonstrated that animals, and presumably humans, could survive weightlessness and the radiation of the space environment and demonstrated techniques to provide oxygen, to clear the air of carbon dioxide, and to maintain a livable temperature in an orbiting spacecraft. Instruments on Sputnik 2 showed that the radiation intensity increased as the spacecraft’s altitude and latitude increased. Later spacecraft showed that this was due to Sputnik 2 entering the edge of the Van Allen radiation belts, bands of high-energy-charged particles circling the earth beginning at an altitude of about 600 miles.
Sputnik 3, launched on May 15, 1958, made use of the full 3,000-pound lofting capability of the R-7 rocket. The satellite weighed 3,018 pounds, carrying 2,130 pounds of scientific and communications equipment. Unlike the biological mission of Sputnik 2, Sputnik 3 was designed to conduct a geophysical study of the space environment. It carried instruments to measure the solar and cosmic radiation outside the spacecraft, the earth’s magnetic field, the rate of impact of micrometeorites, and the properties of the ionosphere. Sputnik 3 was placed in a very similar orbit to that of Sputnik 2, coming within 141 miles of the earth’s surface at closest approach and going out to 1,168 miles from the earth’s surface. Sputnik 3 took 106 minutes to circle the earth. Its instruments continued to function for almost two years, until Sputnik 3 reentered the earth’s atmosphere on April 6, 1960.
Sputnik 3 performed a series of geophysical measurements. It began to map the belts of radiation that surround the earth. Sputnik 3 detected a sharp increase in the drag on the satellite in the same regions where the intensity of high-energy electrons hitting the satellite increased. The magnetometer on Sputnik 3 produced the first map of the earth’s magnetic field.
Impact of the Sputnik Launches
The news that the Soviet Union had launched the world’s first artificial satellite shocked much of the world. Although many people in Europe and North America had regarded Soviet science and engineering as inferior to that of the West, Sputnik 1 demonstrated Soviet capability in space technology. Within hours of the launching of Sputnik 1,U.S. senator Lyndon B. Johnson initiated a complete investigation into the state of the United States satellite and missile programs. Boris Chertok, the deputy director of the Soviet ICBM project, was surprised by the effect of the news of the launching of Sputnik 1. “We thought the satellite was just a simple thing: What mattered to us was to test the rocket again to gather statistics on how its systems were functioning. And suddenly the whole world was abuzz. It was only later that we understood what we had done.” In response to Sputnik 1, the United States undertook a massive reform of education, with a new emphasis on science and mathematics courses.
Historically, most nations have claimed sovereignty over the airspace above their territories and have regulated flights of aircraft in their airspace. The launching of Sputnik 1 resulted in the development of new principles of international law, because Sputnik 1 passed over many nations, including the United States. Because these other countries did not protest when Sputnik flew over their territories, the principle was established that any nation can orbit a satellite over the territory of another nation.