As 1960 unfolded, the United States and Soviet Union were racing to develop their own crewed spacecraft to loft the first human into space. One of the significant unknowns at this point was what a space traveler’s response would be to extended periods of microgravity while orbiting the Earth. Although both countries had launched dozens of animals and biological specimens on board ballistic missiles and sounding rockets for over a decade to assess the effects of brief periods of weightlessness, data were desperately needed on the effects of more prolonged exposure.
Laika shown in the cabin of Sputnik 2 before launch.
The Soviet Union was the first to send an animal into orbit on their second satellite, Sputnik 2, launched on November 3, 1957. Unfortunately, problems with thermal control and an error in programming the telemetry timer on the satellite prevented much useful data from being returned before the canine passenger, named Laika, died of heat exhaustion during the hours after launch. Besides learning that an animal could survive weightlessness for a few hours, more information was needed including the recovery of the biological specimen – something the simple Sputnik 2 was incapable of doing (see “Sputnik 2: The First Animal in Orbit”).
A scientist holding the “life cell” (with an SRV in the background) which would hold four back mice for the Discoverer 3 mission. (USAF)
The US attempted to launch into orbit a biological payload of four lab mice onboard Discoverer 3 on June 4, 1959 as part of a test flight of the secret Corona reconnaissance satellite program. The plan had been to recover the mice inside the SRV (Satellite Reentry Vehicle) after 26 hours in orbit but the launch vehicle failed to place the payload into orbit (see “The First Discoverer Missions: America’s Original (Secret) Satellite Program”). The next attempt to send animals into orbit and recover them would be made by the Soviet Union during a test flight of their crewed spacecraft being developed called Vostok.
Vostok
The Vostok spacecraft, also known as Object K (the “K” standing for “korabl” which is Russian for “ship”), was developed by OKB-1 (Experimental Design Bureau No. 1) under the direction of the famed Soviet aerospace engineer, Chief Designer Sergei Korolev. By the spring of 1960, there were three variants of Object K under development. Object 3K or Vostok-3 was the version which would carry a cosmonaut into orbit. Vostok-2 (which would eventually be renamed “Zenit-2”) was a photographic reconnaissance variant which would return its camera and load of exposed film instead of a cosmonaut. The Vostok-1 or Object 1K was an engineering prototype which would flight test the systems needed for the subsequent versions (for a full discussion of the early development of Object K, see “Korabl-Sputnik & The Origin of the Soviet Vostok Program”).
A Soviet cutaway diagram of the Object 3K spacecraft. Click on image to enlarge. (RKK Energia)
The generic Object K design consisted of two modules. The descent module was a sphere 2.3 meters in diameter with a mass of about 2,400 kilograms. It was covered with an ablative heat shield and contained all the equipment needed for returning from orbit. It was designed to carry a single space suit-clad cosmonaut in a semi reclined ejection seat which served a dual purpose: During the early phases of ascent, this seat could eject the cosmonaut away from the craft in case of a problem. Because of mass restrictions, the capsule could not carry a large enough parachute to guarantee a soft enough landing for the pilot at the end of a normal mission. Instead a forced landing procedure was developed where, after reentry was done, the cosmonaut ejected from the descent module at an altitude of about 7 kilometers. He then used his own parachute to make a soft landing separate from the more quickly falling descent module.
Soviet diagram illustrating the “forced landing” procedure. Click on image to enlarge. (RKK Energia)
During the flight, the cabin interior maintained an oxygen-nitrogen atmosphere at a pressure of one bar like on the ground. Since the effects of weightlessness were unknown, the spacecraft was completely automated with the “pilot” only taking control using rudimentary instruments in an emergency. One of the portholes was equipped with a Vzor optical sight built by TsKB-558 (Central Design Bureau No. 558) that allowed the cosmonaut to visually check the spacecraft’s attitude. While small, the cabin was roomy enough for the cosmonaut to float out of his seat.
The instrument module, mounted at the base of the spacecraft, carried all the equipment not needed for the return to Earth. It was a double cone shape about 2.4 meters in diameter and about as tall with a mass of 2,300 kilograms. It was connected to the descent module by straps and an umbilical arm designed to burn away in case they failed to separate before reentry. This module carried various consumables for life support, the attitude control system, batteries, telemetry systems and a liquid propellant TDU-1 retrorocket at its base. Producing 16 kilonewtons of thrust for 45 seconds, the TDU-1 was built by OKB-2 under Alexei M. Isayev. Spacecraft attitude was controlled automatically by gas jets using inputs from solar and infrared sensors as well as a “gyrohorizon”. This system had to orient the spacecraft precisely when the TDU-1 fired in order to make a survivable ballistic reentry. As a backup, the cosmonaut could control the spacecraft’s orientation and fire the TDU-1 manually. The descent module had no active attitude control and used aerodynamic forces in conjunction with an offset center of gravity to maintain orientation during reentry.
A view of a 1K spacecraft being prepared for launch. (RKK Energia)
Since mass restriction did not allow sufficient redundancy in the TDU-1 retrorocket, the spacecraft employed an interesting backup system to return to Earth: Atmospheric drag. The spacecraft would be placed into a orbit that would naturally decay in ten days or less. The Soviet spacecraft was designed from the start with a ten day endurance so that if the TDU-1 failed, the cosmonaut still had a chance to return to Earth alive. While initial plans called for the first manned mission to last a day, this ten-day capability would allow the Soviets to attempt missions an order of magnitude longer than those planned for the much smaller Mercury capsule.
Soviet cutaway diagram of the Vostok mounted on top of the Blok E stage of its 8K72K launch vehicle. Click on image to enlarge. (RKK Energia)
The spacecraft would be launched into orbit under an aerodynamic shroud using an improved, man-rated version of the 8K72 used to launch the first Luna probes called the 8K72K (see “The First Race to the Moon: Getting Off the Ground”). Its R-7-based booster would incorporate various engine and systems improvements developed for the newer R-7A ICBM being developed at OKB-1. The Blok E upper stage would also include many upgrades including the replacement of its RO-5 engine with the more reliable and powerful RO-7 built by OKB-154 under Semyin Kosberg. Although work on the 8K72K started in January 1959 and progressed well into 1960, it was decided to use the 8K72 to launch the first unmanned Object 1K prototypes.
Drawing the the Vostok and its launch vehicle in its launch configuration. Click on image to enlarge. (RKK Energia)
Vostok Test Flights
The first Vostok prototype, named Korabl-Sputnik (Russian for “satellite ship”) but also known as Sputnik 4 in the West, was launched on May 15, 1960. This was a simplified version of the Vostok-1 known as Object 1KP which did not carry many systems including life support or a heat shield but instead concentrated on testing spacecraft systems up to the deorbit burn (where the spacecraft would burn up with no recovery planned). While the four-day mission largely met its objectives, a problem with the attitude control system relying on an infrared sensor malfunctioned during the deorbit burn placing the satellite into a higher orbit instead (see “Korabl-Sputnik & The Origin of the Soviet Vostok Program”).
Soviet cutaway diagram of Object 1K used for the first Vostok test flights. Click on image to enlarge. (RKK Energia)
After a review of the first Korabl-Sputnik mission, it was decided that a follow on test flight with a second 1KP was not required and that the program would move on to a fully functional 1K prototype with an attempt at recovery. In addition to a range of system improvements, it was decided to eliminate the troublesome infrared sensor on the crewed 3K spacecraft instead relying on solar sensors and visual sightings made by the pilot. Also to be carried on the 1K No. 1 spacecraft would be a biological payload which included a pair of dogs named Chaika (“Seagull”) and Lisichka (“Foxy”). The dogs and other specimens would be housed in a container formally known as GKZh-2 (the Russian acronym for “Pressurized Animal Cabin 2”) which would be mounted on Vostok’s ejection seat. The container included a pair of television cameras producing ten 100-line images every second so that ground controllers could monitor the dogs’ reactions to orbital flight. Following reentry after the planned 3 to 5-day mission, the ejection seat would be fired at an altitude of 7 kilometers with the GKZh-2 and its passengers descending to Earth separately from the spherical descent module.
Soviet diagram showing the GKZh-2 cabin which housed the dogs and other biological specimens during the Vostok test flights. Click on image to enlarge.
At 12:31 Moscow Time on July 28, 1960, 1K No. 1 lifted off from the Baikonur Cosmodrome in Soviet Kazakhstan atop of 8K72 No. L1-10. Unfortunately, the RD-107 engine on one of the launch vehicle’s four boosters disintegrated after 23.6 seconds of flight. The damaged booster fell off the ascending rocket 38 seconds after launch which then tumbled out of control and broke up. The descent module broke free of the stack, which spread debris 1½ to 3 kilometers downrange, and came down hard without the time needed for its parachute to fully deploy. Because remote controlled activation of the ejection seat was blocked until 50 seconds in flight to ensure that the failing rocket would clear the launch facility, the canine passengers were killed during the accident.
Here is a montage of images purportedly showing the failure of 8K72 No. L1-10 during the launch of 1K No. 1 on July 28, 1960. Click on image to enlarge.
As a result of this accident, efforts were begun to develop a launch escape system for the crewed 3K which could save the pilot’s life in case of an abort during the first minute of flight. While the failure of 1K No. 1 was keenly felt, NASA’s Mercury-Atlas 1 mission launched on July 29 to test a flight-worthy Mercury capsule in space for the first time also failed about one minute into its ascent (see “The Disappointing Flight of NASA’s Mercury-Atlas 1”). While NASA’s failure was immediately reported by the press, the failure of this Vostok test flight would remain a secret until 1986.
Korabl-Sputnik 2
An investigation into the failure of the 8K72 No. L1-10 showed that the Blok G booster’s RD-107 engine experienced high-frequency pressure oscillations which led to its loss. These pressure oscillations had been observed earlier and corrected in the latest batch of engines but the RD-107 which failed was from an earlier batch. With the problem identified, plans immediately turned to launching 1K No. 2 on August 17, 1960 for a slightly more conservative one-day mission. The canine passengers for this flight were named Belka and Strelka (“Squirrel” and “Little Arrow”, respectively). Forty mice, two rats and a variety of plants accompanied the dogs for their flight. The spacecraft also carried other instruments to study cosmic rays as well as high energy ultraviolet and X-ray emissions.
The canine passengers on 1K No. 2, Strelka and Belka. (Roscosmos)
The 8K72 No. L1-12 rocket with 1K No. 2 attached was rolled out to the launch pad on August 16. But during prelaunch testing, a problem was found in an oxygen valve on the 8K72 forcing a two-day postponement for a replacement to be flown in and installed. With all now ready for launch, the GKZh-2 cabin with Belka and Strelka inside was installed in the Vostok descent module at about 03:30 Moscow Time on August 19. The 8K72 rocket successfully lifted off at 11:44:07 Moscow Time and placed what was now called Korabl-Sputnik 2 (or popularly known in the West as “Sputnik 5”) into a 306 by 339 kilometer orbit with an inclination of 64.96°.
Doctors on the ground carefully watched the stream of bio-medical telemetry being returned by Korabl-Sputnik 2 to determine how the dogs were adapting to weightlessness. Initial television images of the dogs raised some concerns when they did not seem to move. The dogs became more animated over time although their motions seemed convulsive. Finally during the fourth orbit, Belka began squirming and then vomited for the first documented case of space sickness. Because of this and other concerns, the decision was eventually made to limit the first crewed flight of the Vostok to a single orbit to minimize the risks. Other spacecraft systems largely performed as expected with the exception of the troublesome infrared attitude sensor. It was eventually decided to switch to the solar-based sensor system for attitude control.
A montage of TV images showing Belka while in orbit on board Korabl-Sputnik 2. Click on image to enlarge.
As the Korabl-Sputnik 2 began its 18th orbit, the NIP-4 ground station in Yeniseisk in the Soviet Far East sent a command starting the programming timer for the landing sequence. At 10:38 Moscow Time on August 20, the spacecraft fired its TDU-1 engine while out of communication range over the Gulf of Guinea near the coast of Africa to begin its descent. At 10:50 ground stations detected a beacon indicating that the engine firing had worked as planned. The descent module of Korabl-Sputnik 2 landed at 11:07 Moscow Time in the Orsk region of Kazakhstan only ten kilometers from the target point. Search teams quickly located the descent module and the GKZh-2 containing Belka and Strelka who were found to be in good condition after their flight lasting 26 hours and 23 minutes. While the American Discoverer 13 had beaten the Soviets by nine days with the first successful recovery of a payload from orbit, Korabl-Sputnik 2 held the distinction of being the first spacecraft to return animals safely from orbit.
The recovery of the GKZh-2 container with Belka and Strelka on board at the end of the Korabl-Sputnik 2 flight.
As public celebrations of this feat began, Belka and Strelka were examined and found to be in good condition after their flight. Belka and Strelka reportedly lived happily afterwards at the aviation medicine institute and both had healthy puppies in the months following the flight. One of Strelka’s puppies, named Pushinka, was given to First Lady Jacqueline Kennedy as a gift from Soviet Premier Nikita Khrushchev in June 1961. With this successful flight completed, Soviet space planners pushed forward with preparations for more Vostok test flights before the first piloted mission was expected in several months.
A picture of one of Strelka’s puppies, Pushinka, given to First Lady Jackie Kennedy in June 1961. (Robert Knudsen/JFK Library)
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Related Reading
“Korabl-Sputnik and the Origin of the Vostok Program”, Drew Ex Machina, May 15, 2020 [Post]
“Vostok’s Legacy”, Drew Ex Machina, April 12, 2015 [Post]
General References
Boris Chertok, Rockets and People Volume III: Hot Day of the Cold War, SP-2009-4110, NASA, 2009
James Harford, Korolev: How One Man Masterminded the Soviet Drive to Beat America to the Moon, Wiley, 1997
Nicholas L. Johnson, Handbook of Soviet Manned Space Flight, Univelt, 1980
John Rhea (editor), Roads to Space: An Oral History of the Soviet Space Program, Aviation Week Group, 1995
Yuri P. Semenov (editor), Racketno-Kosmicheskaya Korporatsiya ‘Energia’ Imeni S P Koroleva (in Russian), RKK Energia, 1996
Asif A. Siddiqi, Sputnik and the Soviet Challenge, University Press of Florida, 2000
Timothy Varfolomeyev, “Soviet Rocketry That Conquered Space Part 3: Lunar Launchings for Impact and Photography”, Spaceflight, Vol. 38, No. 6, pp. 206-208, June 1996