Capsules

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A capsule is a sealed, pressurized cabin that contains a controlled environment for humans, animals, or equipment during high-altitude flight or spaceflight. Capsules have been used on dozens of historically important missions from the earliest days of the U.S. and Soviet space programs.

The first space capsule orbited was the Soviet Sputnik 2. Launched November 3, 1957, it was only the second human-made object to orbit Earth. The capsule weighed 114 kilograms (250 pounds) and carried the dog Laika into space, but it was not designed to be recovered. Laika died in orbit four days later. Most capsules, however, are re-entry vehicles made to bring their occupants back safely to Earth.

The earliest human-piloted capsules were the Soviet Vostok and U.S. Mercury spacecraft. Vostok had a spherical compartment 2.5 meters (98 inches) in diameter with room for a single cosmonaut. It was attached to a coneshaped equipment module that carried supplies, giving the craft the appearance of a stubby ice cream cone. A Vostok capsule carried Yuri Gagarin, the first human in space, aloft on April 12, 1961. After leaving orbit, the spherical compartment separated from the equipment module and descended through the atmosphere, but it was not designed for a soft landing. The cosmonaut parachuted to safety after ejecting at an altitude of about 6,100 meters (20,000 feet). Five other Vostok missions followed, the last of which carried Valentina Tereshkova, the first woman space traveler.

Mercury capsules also carried a single passenger. They traveled atop either Redstone rockets (for suborbital flights) or the larger Atlas rockets, which were powerful enough to lift the 1,350-kilogram (3,000-pound) capsules into orbit. A Mercury capsule, like subsequent Gemini and Apollo craft, was designed to "splash down" in the ocean after descending by parachute.

The Soviet Voskhod capsule was the first designed to carry multiple passengers. It was a modified version of the Vostok spacecraft, with the ejection seat removed to make room for up to three cosmonauts and with an added airlock so that space walks could be performed. Voskhod capsules also had larger parachutes to permit ground landings. Three cosmonauts orbited Earth aboard Voskhod 1 on October 12, 1964. The Voskhod 2 capsule carried Alexei Leonov and Pavel Belyayev into orbit on March 18, 1965; Leonov performed history's first space walk that day, remaining outside of the capsule for twenty minutes.

Conditions were cramped aboard the Voskhod—the three Voskhod 1 cosmonauts were packed into the same volume of space Gagarin had, but without pressure suits or ejection seats for safety—but space aboard Gemini was at a premium as well. The Gemini capsule was made to carry two astronauts but had only 50 percent more interior space than Mercury did. Astronaut John Young compared being inside Gemini to "sitting in a phone booth that was lying on its side." Nevertheless, Gemini provided its crews with valuable space experience. While Mercury could remain in orbit for only a day or so at most, Gemini could sustain two astronauts for up to two weeks. Gemini astronauts had complete control over the motion of their capsules, which they would need to practice the docking maneuvers necessary for later Apollo missions. On December 15, 1965, Gemini 6 and 7 became the first human-piloted spacecraft ever to rendezvous with one another. Five Gemini astronauts also performed space walks; the last, by Buzz Aldrin during Gemini 12, spanned a record-setting five hours, thirty minutes.

Like Vostok, Gemini was a two-section spacecraft. The astronauts rode in the re-entry module, which was attached to an adapter module containing propellant, water, oxygen, and other supplies. The adapter module was jettisoned shortly before re-entry.

The success of the Gemini program gave the United States the experience it needed to pursue human exploration of the Moon. The Apollo lunar program was the last major U.S. space initiative in which astronauts rode in nonreusable capsules. Three astronauts sat abreast inside the Apollo capsule, referred to as the Command Module (CM). The CM, which was about 3.4 meters (11 feet) high and 4 meters (13 feet) wide, had a more regular conic shape and a larger interior (about 6 cubic meters [8 cubic yards]) than Mercury or Gemini capsules; this allowed the crew to remove their bulky space suits after liftoff. Supplies for the journey to lunar orbit and back were kept in the Service Module (SM) behind the CM. The SM was jettisoned before the 5,300-kilogram (11,700-pound) CM returned to Earth.

Engineers dubbed the Mercury spacecraft a "capsule" because there was barely enough room to fit the astronaut, 120 controls, fifty-five switches, and thirty-five control levers inside the spacecraft, which was only 2.9 meters (9.5 feet) long and 1.8 meters (6 feet) wide. The name stuck.

Apollo (Volume 3);; Cosmonauts (Volume 3);; Gemini (Volume 3);; Rendezvous (Volume 3).

Angelo, Joseph J., Jr. The Dictionary of Space Technology, 2nd ed. New York: Facts on File, 1999.

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Murphy, Sarah M. "Vostok Spacecraft, Crews, and Launch Vehicles." The Astronaut Connection. <http://www.nauts.com/vehicles/6 0s/vostok.html>.

Zak, Anatoly. "The True Story of Laika the Dog." Space.com. <http://www.space.com/news/laika _anniversary_991103.html>.

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