Sputnik 2

Sputnik 2, formally designated PS-2 (Prosteyshiy Sputnik-2, “Simplest Satellite-2”), was the second artificial satellite placed into geocentric orbit and the first spacecraft to carry a living organism into space. Launched by the Soviet Union on 3 November 1957, less than a month after the historic launch of Sputnik 1, it transported the space dog Laika, marking a pivotal milestone in the early Space Race. Although Laika survived only for a few hours after reaching orbit, the mission nonetheless provided unprecedented biological and scientific data from beyond Earth’s atmosphere. Sputnik 2 remained in orbit until 14 April 1958, completing 2,370 revolutions before re-entering over the North Atlantic.

Background

In 1955 Mikhail Tikhonravov proposed Object D, an ambitious satellite project intended to carry substantial scientific instrumentation. The spacecraft was expected to weigh several hundred kilograms, dwarfing the mass of the planned American satellite. Nikita Khrushchev strongly supported the concept, which was formally approved in January 1956. However, technical delays meant that neither Object D nor its dedicated launch vehicle could be completed by the target date of late 1957.
In response, Sergei Korolev, Chief Designer of OKB-1, proposed two simpler satellites known as PS-1 and PS-2, each spherical and far less complex. Their purpose was to ensure a Soviet satellite launch before the United States. PS-1 became Sputnik 1, successfully launched on 4 October 1957.
Immediately after this triumph Khrushchev requested a second spectacular achievement timed to coincide with the 40th anniversary of the October Revolution in early November. With barely three weeks available, Korolev and his team repurposed a payload container from the R-5 Pobeda sounding-rocket programme, which had been used previously in suborbital dog-carrying missions. This container was integrated beneath the spherical PS-2 section of the R-7 launch vehicle. As on earlier missions, no recovery system was provided.

Spacecraft Design

Sputnik 2 was a conical capsule with a broad base that together with its attached Blok A booster stage created a substantial mass in orbit. Although precise dimensions varied among sources, the capsule was designed to house both scientific equipment and a sealed biological cabin. Its compartments included:

• Radio transmitters and a telemetry system
• A programming unit for timed operations
• Temperature regulation and air-regeneration systems
• Spectrophotometers and cosmic-ray instruments

The spacecraft was not designed to separate from the final rocket stage, leaving the combined structure orbiting as a single body.

Passenger: Laika

Laika—originally named Kudryavka (“Little Curly”)—was a small mixed-breed dog of part-Samoyed heritage selected for her calm temperament and previous training in suborbital flights. A second dog, Albina, served as backup. Prior surgical attachment of telemetry leads allowed monitoring of heart rate, respiratory frequency and blood pressure throughout the mission.
Laika’s compartment was padded and pressurised, with sufficient room for standing or lying down. The cabin incorporated harness restraints, a waste-collection system, oxygen regeneration equipment and gelatinised rations. A television camera supplied visual monitoring.

Scientific Experiments

Sputnik 2 was the first satellite capable of making continuous scientific measurements in orbit. Earth’s atmosphere prevents direct observation of the Sun’s ultraviolet and X-ray output, and short-duration sounding rockets could not provide sustained observations. To address this, the satellite carried:

• A solar ultraviolet spectrophotometer
• A solar X-ray spectrophotometerBoth instruments were supplied by Sergei Mandelstam of the Lebedev Institute.

In addition, a cosmic-ray detector designed by Sergei Vernov and colleagues at Moscow University was included, mounted externally on the Blok A stage due to lack of space in the main capsule. Engineering and biological telemetry were transmitted using the Tral-D system for up to fifteen minutes during each orbit.

Launch Preparations

The launch vehicle was a modified R-7 ICBM, designated 8K71PS for the PS-2 mission. The rocket arrived at the Baikonur test range on 18 October 1957. Laika was placed in her cabin on 31 October, and the assembled payload was mounted on the rocket later that night. External heating was applied to counteract sub-zero conditions at the Kazakh launch site.

Mission and Fate of Laika

Sputnik 2 lifted off at 02:30:42 UTC on 3 November 1957 from Launch Complex 1 at Baikonur. After reaching orbit, the nose cone separated successfully, but the satellite failed to detach from the Blok A stage. Loss of insulation and unexpected heating caused cabin temperatures to rise sharply.
Telemetry showed that Laika’s heart rate jumped from 103 beats per minute pre-launch to around 240 during ascent. After three hours her heart rate returned toward baseline but remained elevated compared with ground tests, indicating persistent stress. Although early data confirmed she was eating normally, her vital signs ceased approximately five to seven hours into the mission.
The Soviet authorities for many years claimed she had died from battery failure or humane euthanasia. Later disclosures revealed that Laika died from overheating during the spacecraft’s fourth orbit, long before the originally intended timeframe.
Despite the biological loss, Sputnik 2 remained a visible object in the sky. Its tumbling motion created flashing patterns easily observed from Earth until re-entry in April 1958.