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Roots of the Voskhod-2 mission

A plan to send a Soviet cosmonaut to walk outside the spacecraft was conceived as part of the original Voskhod program formally approved by the Soviet government in March 1964. Obviously, the mission would have a tremendous political and historic significance but it would also be critical from the engineering standpoint.


Several alternative configurations of the Voskhod-2 spacecraft had been debated, before the architecture with a flexible airlock was chosen.

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Like many other early firsts of the Soviet space, the idea of a spacewalk is attributed to the de-facto father of the program Sergei Korolev. (466) He saw the ability to exit a spacecraft as a natural aspect of space exploration and envisioned cosmonauts performing routine assembly and repair work outside, including welding operations. (18) According to Leonov's account, when Korolev first invited cosmonauts to the bureau to discuss the spacewalking mission, he said that a sailor on an ocean-going ship should be able to swim, so a cosmonaut should be able to walk in space.

Obviously, Korolev was also aware of spacewalks being prepared in the US and, as before, realized the political importance of pioneering this feat.

Following the successful introduction of the Voskhod spacecraft in 1964, the OKB-1 design bureau led by Korolev immediately switched to adapting it for a spacewalk mission, which was alternatively known as 3KD, Voskhod-2 or Vykhod (Egress) (742). As it happened during the transition from the Vostok project to Voskhod, a number of major design changes had to be made to adapt Voskhod for a spacewalking mission: the crew was reduced from three to two people, new spacesuits capable of functioning outside the spacecraft had to be introduced and the ship's seats were to be modified to accommodate space-suited cosmonauts. But, most importantly, a system for providing the egress and ingress of cosmonaut in orbit had to be developed. Multiple technical solutions to the problem had been considered.


A Soviet-period graphics illustrating the transition from Voskhod (right) to Voskhod-2 spacecraft.

From the engineering standpoint, the easiest method for an exit in orbit would be equipping the main entrance hatch No. 1 of the Descent Module with a sub-hatch, which could open either outwards or inside the spacecraft. Another option under consideration was adding a sub-hatch into the "technical hatch" No. 3 on the opposite side of the Descent Module. In both cases, the inward opening of the hatch would require to removing a cosmonaut chair next to it, but, on the plus side, the internal pressure of the capsule would help keeping the hatch shut after the spacewalk.

According to the official documentary about the Voskhod-2 mission, the method of direct exit from the spacecraft was problematic because it would lead to a considerable loss of air supplies during the depressurization of the Descent Module. The film did not mention any issues with avionics of the Descent Module being exposed to vacuum in case of its depressurization, which was cited by some sources as a reason prohibiting the depressurization of the crew capsule. (52)


Exit hatch design configuration considered in the early stage of the Voskhod-2 development.

In any case, to avoid depressurization of the entire cabin, the spacecraft's hatch would have to be equipped with an airlock. This feature was deemed necessary in all future spacewalking missions anyway. At least two possible locations for the airlock were evaluated. The integration of the airlock into Hatch No. 1 would complicate the boarding of the crew on the launch pad and would adversely affect the ship's center of gravity. As a result, hatch No. 3 was chosen as a place for the accommodation of the airlock. The same hatch could still accommodate a window with a Vzor optical instrument, which was used by pilots for navigation purposes during manual control of the spacecraft.

The exact architecture of the deployable and jettisonable airlock was also a subject of debate: a hard-body telescopic structure initially competed with a flexible design. One available sketch, dated May 19, 1964, shows a concept of an airlock made of three telescopic segments. Also, various hatch arrangements for crew boarding and those for a spacewalk were under consideration at the time and OKB-1 engineers were apparently directed to glean exact details of the exit hatch from aviation or submarine designs. The proposed diameter of the spacewalk hatch was initially estimated between 700 and 800 millimeters.

According to the early plans, the first human spacewalk was to be proceeded by a spacewalk of an animal, probably a dog, during a pilotless mission, aimed to test the influence of weightlessness and space radiation on a space-suited creature. However, the idea of a pilotless test launch was eventually limited to an automated deployment of the airlock with a dummy spacesuit. (84)

Political approval and development

On March 25, 1964, a group of industry officials led by Leonid Smirnov wrote to the Central Committee that the High Commission of the Soviet for Military and Industrial Issues had evaluated and endorsed the plan calling for the launch of the three-member crew on a day-long mission in an 180 by 240-kilometer orbit in the 3rd quarter of 1964. The same document also approved five additional Vostok-based spacecraft to be manufactured in 1964 and 1965 with the goal of "testing the capability of a human being in direct involvement in assembly in orbit." (This was a clear reference to a spacewalk.) Simultaneously, the same missions would test the military usefulness of piloted spacecraft, the letter said.

The Soviet government formally endorsed the Voskhod project with an official decree on April 13, 1964. According to the document, four Vostok spacecraft (refurbished into Voskhods) were allocated for achieving a three-member flight in the 2nd or 3rd quarter of 1964 and five new vehicles would be built in 1964 and 1965 to achieve the first spacewalk. (509)

On June 13, 1964, Korolev signed a formal technical assignment for the transfer hatch and its opening mechanism to be installed aboard the 3KD (Voskhod-2) spacecraft.

On Dec. 10, 1964, two months after the original Voskhod mission, top industry officials reported to the Central Committee of the Communist Party that the two new Voskhod-based ships were being prepared as two seaters for a space-walking experiment. The goal of the spacewalk was characterized as testing the direct participation of cosmonauts in the assembly of spacecraft in orbit. The document quoted the following launch schedule for the mission:

  • From December 1964 to January 1965: The launch of an unmanned spacecraft with a mannequin onboard for testing all systems, including those for the spacewalk. It would be announced as Kosmos;
  • First quarter of 1965: The launch of a piloted spacecraft with a crew of two.

The mission would include a spacewalk with the use of an airlock. The spacewalk was planned during the second orbit, when the spacecraft would be overflying the Soviet territory. The cosmonaut was expected to remain outside the spacecraft from 10 to 15 minutes, floating up to a distance of 10 to 15 meters from his ship. (509) A tether would carry an electric cable providing telephone connection of the spacewalking cosmonaut with his commander. An external TV camera and a moving film camera would be used to document the exercise.

The spacecraft was expected to enter a 180 by 400-kilometer orbit with an inclination 65 degrees toward the Equator. The mission was to last one day with a maximum duration of three days.

In the Soviet tradition of secrecy, the officials recommended that the flight be announced only after the successful orbital insertion of the spacecraft into orbit and after the spacewalk was completed, which would be at the end of the second or beginning of the third orbit.

The Chairman of the Soviet of Ministers USSR Aleksei Kosygin endorsed the plan on December 24, 1964. (509)


The article by Anatoly Zak; Last update: March 27, 2020

Page editor: Alain Chabot; Edits: March 18, March 26, 2020

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The descent module of the Voskhod-2 spacecraft with an attached copy of the airlock and a mannequin illustrating the spacewalk by Aleksei Leonov. All three hatches of the descent module are visible on the photo. Copyright © 2001 Anatoly Zak


A May 19, 1964, sketch of an airlock shows a three-segment telescopic structure. Click to enlarge. Credit: RKK Energia


A proposal for a outward-opening EVA hatch aboard the Voskhod-2 spacecraft. Click to enlarge. Credit: RKK Energia


Click to enlarge. Credit: RKK Energia


A proposal for an airlock on the entrance hatch No. 1 was rejected because it complicated the boarding of the crew and shifted the ship's center of gravity. Click to enlarge. Credit: RKK Energia


Click to enlarge. Credit: RKK Energia


Winning position for the airlock was on hatch No. 3. Click to enlarge. Credit: RKK Energia