The date and the facts
Sputnik 1 was launched by the Soviet Union on October 4, 1957, from a site in Kazakhstan now known as the Baikonur Cosmodrome. It was the first artificial object to orbit the Earth. That is well documented and not seriously disputed. The launch took place late on October 4 in Universal Time, which meant it was already early on October 5 in Moscow, so you will see both dates in different sources.
The name means “traveling companion” or “satellite” in Russian. The satellite itself was a polished metal sphere about 58 centimeters (23 inches) in diameter, weighing about 83.6 kilograms (184 pounds). Four long antennas extended backward from it. Inside was little more than batteries, a radio transmitter and some instruments for measuring temperature and pressure; its radio signal is the subject of our separate article on the Sputnik radio signal.
Why a sphere
The shape was a practical choice. A sphere is simple to build, easy to make airtight, and presents the same profile from any direction, which helped scientists follow it. The surface was polished and the interior pressurized with nitrogen so the temperature readings could be compared. It was designed to be tracked from the ground, both by radio and, in the first days, by eye, as the rocket’s core stage was also in orbit and was bright enough to be seen in the sky.
The rocket
The launch vehicle was the R-7, designed under Sergei Korolev’s leadership as an intercontinental ballistic missile. The R-7 had been flown in test only a few weeks before, in August 1957, with mixed results. When the engineers realized it could lift a satellite, they proposed using it for that purpose. The original plan was for a more complex scientific satellite, but it was running late, so the team switched to a simple one that could be built quickly. The decision is generally credited to Korolev and approved by Soviet leadership. The story that it was entirely improvised is probably exaggerated, but the simplified satellite was a quick substitute for the more ambitious one.
The satellite was part of the Soviet contribution to the International Geophysical Year, a period of coordinated global research from July 1957 to December 1958. The United States had also announced a satellite plan for that period, and both governments had made public statements about satellites in advance, which is one reason the Soviet success was not entirely unforeseen.
What it did in orbit
Sputnik 1 completed an orbit in roughly 96 minutes. Its orbit was elliptical, ranging from a few hundred kilometers above the Earth at its lowest point to something over 900 kilometers at its highest. Its transmitter ran on battery power and kept sending for about three weeks, until the batteries were drained. After that, the satellite went silent but remained in orbit. Atmospheric drag slowly pulled it down, and it burned up on re-entering the atmosphere on January 4, 1958, after roughly three months in space.
The scientific results were modest. Tracking the orbit gave information about the density of the upper atmosphere, because drag affects the satellite’s path, and the radio signals gave some data on how radio waves travel through the ionosphere. The achievement was less in the data than in the proof that it could be done.
The political reaction
The effect on public opinion was out of proportion to the object’s size. In the United States, the launch was widely reported as a technological surprise, and many people felt that the Soviet Union had pulled ahead. The concern was not only about a satellite beeping overhead. Observers understood that a rocket that could place a satellite in orbit could also, in principle, carry a warhead across continents. Within weeks, the Soviet Union launched Sputnik 2 with the dog Laika aboard, adding to the impression of a lead.
Responses followed in the next year or so, though historians debate how much each was caused by Sputnik alone. In the United States:
- A Vanguard rocket carrying a small satellite failed spectacularly on the launch pad in December 1957.
- The Army’s Explorer 1 reached orbit on January 31, 1958.
- NASA was created in 1958.
- The National Defense Education Act of 1958 increased federal support for science and language education.
President Dwight Eisenhower is often described as having been publicly calm, as the U.S. government had already been privately aware that the Soviet rocket program was advanced. The broader contest this opened is the subject of our article on space age beginnings.
What Sputnik started
Sputnik 1 showed that artificial satellites were possible and set off a wave of development. Within a few years satellites were being used for weather observation, communication and, eventually, navigation. A direct line connects Sputnik to global positioning: scientists at Johns Hopkins used its radio signal to work out how a satellite could be used to find a position on Earth, an idea that led to the Navy’s Transit system. Later chapters of that story are in our look at the Navstar constellation.
Sputnik 1 was not intended to change world politics, but it did. A small, simple machine, built quickly from limited components, became one of the most influential technological events of the twentieth century.