By 1964, when a specific proposal had been put forward to carry out a spacewalk outside of the Voskhod-2 spacecraft, Zvezda had already accumulated some experience in producing rescue suits, and had begun the experimental development of advanced products for long-term space flights.

However, extra-vehicular activity presented a series of completely new challenges. When work began, an acceptable technical solution allowing a cosmonaut to exit the Voskhod spacecraft had still not been found. The Voskhod cabin was not designed for continuous operation in a depressurized state, and there was no room for an additional special airlock on the ship. The Experimental Design Bureau 1 studied various options for a foldable airlock.

The specialists at Zvezda, which in January 1964 was directed by Chief Designer G. I. Severin, proposed a design for an airlock with a soft inflatable shell. The creation of a soft airlock that could be inflated in orbit allowed the designers to make use of the existing vehicle design and booster rocket fairing with only small modifications.

Development
Zvezda’s proposal was finally accepted at a meeting with S. P. Korolyov at Experimental Design Bureau 1 in April 1964, where Zvezda was represented by G. I. Severin, N. L. Umansky, and I. P. Abramov. On 13 April 1964, the government issued a resolution setting the schedule for the production of the ships Voskhod (3KV) and Vykhod (3KD).An intensified study of the designs of the spacesuit, airlock, and locking system began. On 9 July, the specifications based on these designs (fig. 1) were approved, and a governmental resolution was issued (8 July 1964) regarding the development of the airlock and the spacesuit with a backpack life-support system. The lead company put in charge of these products was the Zvezda Research and Production Enterprise.

The Volga airlock on the Voskhod-2 consisted of a rigid upper part with a hatch for access to space and a lower mounting ring, coupled to the flange of the ship. They were connected to each other with a pressure shell and a load-bearing frame.From 1964 to 1965, seven sets of airlocks were made in a short time, two of which were used in the manned and unmanned missions of Voskhod-2.

The remaining five sets were used during the tests of the airlock at Zvezda and as spares.Currently three of them are in the museums of Zvezda, the Energiya Rocket and Space Corporation, and the Memorial Museum of Cosmonautics in Moscow. The other two products are in the private museum of the Tess Fund in Denver and in another private collection outside the Russian Federation.

Given the goal of creating products for Voskhod-2 as soon as possible, as well as the limited battery life of the suit, it was decided to base the new design on the existing ventilation-type spacesuit with separate ventilation for the helmet and the shell.Before exiting from the descent module, the cosmonaut put on a backpack (code name KP-55), which was attached to the suit with a suspension system.

The oxygen was stored in the backpack in special cylinders under pressure. The cosmonaut turned on the oxygen supply by himself using a remote control. Oxygen entered the helmet, got into the suit shell, and then was released into the environment. Oxygen use was calculated to ensure pressurization of the suit, oxygen supply to the cosmonaut, and removal of СО2 for 45 minutes. In fact, Alexei Leonov’s spacewalk outside the ship lasted only 12 minutes, and he spent a total of about 23 minutes in a vacuum.

The cosmonaut’s safety in outer space was ensured by a special seven-meter tether, which included an anti-vibration device, steel cable, emergency oxygen supply hose, and electric wires, which transmitted medical and technical measurements to the spacecraft, and allowed the cosmonaut to have telephone communication with the ship's commander.

The spacesuit of the Voskhod-2 commander P. I. Belyaev had the same design as Leonov’s suit. If necessary, Belyaev could depressurize the cabin, open the hatch, and go into the airlock to assist Leonov. A wooden mock-up of the airlock was made in July 1964 in order to conduct a preliminary test of the size of the airlock and the ability of a cosmonaut in a spacesuit to pass through the hatch on the Voskhod spacecraft.

Preparation
In August 1964, a mock-up committee carried out an inspection, during which flight candidates A. Leonov, P. Belyaev, and V. Gorbatko wore the Berkut spacesuits and tested out the descent module and a mock-up of the airlock.On 24 and 25 September 1964, a functional mock-up and capsule of the Voskhod-2 spacecraft were used at Baikonur to demonstrate the systems to N. S. Khrushchev during his visit to the cosmodrome. In the presence of the cosmonauts, G. I. Severin demonstrated the airlock and the Berkut spacesuit, and S. P. Korolyov demonstrated the Soyuz spacecraft.

By the end of 1964, Zvezda had completed the adjustment of all systems and all kinds of tests: on the ground, in heat and pressure chambers, in pools, as well as strength and resource tests, both of the technology itself and with human testers (fig. 6). A corresponding concluding paper was issued.By February 1965, tests with humans in Berkut spacesuits in a heat mock-up of the descent module were carried out, as well as comprehensive interagency testing of all systems.

The Voskhod-2 flight was preceded by a flight 22 February of the unmanned spacecraft Kosmos-57, which was equipped with an airlock and a Berkut simulator suit. Its planned flight program included a full simulation of the airlock and airlock system in orbit, as well as the pressurization of the spacesuit by remote command from Earth. A few days before the flight, during inspections of the airlock of the Voskhod-2 at Baikonur, engineers discovered that in the absence of a pressure drop, the exit hatch of the airlock might not fully close, as the contacts used to monitor hatch closure remained open.

As a result, the program that controls the operation of the hatch might fail (and the hatch would fail to open). Zvezda specialists reported this to S. P. Korolyov, who immediately called a meeting of the specialists involved. To be on the safe side, they decided to send an additional command to close the hatch from one of the Far East command and measurement stations and duplicate it from the next neighboring station. This decision was made on 19 February 1965, despite the objections of some members of the flight control service, who were wary of making any changes in the program just a few days before the launch.

During a test flight of Kosmos-57, midway through the program, the link with the spacecraft was lost. Although the flight program was not fully carried out, most of the operations on the airlock and the suit performed normally, which served as a validation of the equipment. A decision was made to double-check the airlock jettison operation, which was not carried out during the flight of Kosmos-57. This was done on 7 March 1965, on the mock-up of the airlock installed on the Kosmos-59, which was already prepared for flight. After this flight, the Voskhod-2 mission was authorized.On the morning of 18 March 1965, P. Belyaev and A. Leonov were suited up and taken to the launch pad.

The extra-vehicular operation was scheduled for as early as the second full orbit after the launch of the spacecraft on 18 March 1965.The spacewalk was carried out in full accordance with the prepared program. Some journalists describing the situation have written about a swelling of the spacesuit, which is not true. A spacesuit at normal working pressure has a certain size, which is the same both in a vacuum and in ground conditions. In order to facilitate his entrance into the airlock, Leonov properly reduced the pressure in his suit, which facilitated the bending of the suit shell.

In general, the difficulties that arose can be explained by the fact that the procedure for entry into the airlock was not well tested in ground conditions. In addition, as Leonov stated after the flight, he tried to enter the airlock head first, not feet first as he had practiced on earth, which meant that he had to roll around inside the lock to enter the descent module These difficulties can be attributed to the unusual conditions of open space and weightlessness that were not present during ground tests.The next emergency situation occurred after the spacewalk, when one of the cosmonauts moving around inside the descent module accidentally turned on the air supply from the autonomous gas supply in his suit, which led to a significant increase in cabin pressure. There was some panic on Earth until they figured out what the problem was.

Finally, because of a failure in the spacecraft’s orientation system, the cosmonauts were forced to manually land the spacecraft, which fell on to the snow-covered taiga. However, the crew put their spacesuits and portable emergency supplies to good use, which ensured their survival in a deserted location for two days until they were rescued.Overall, the Voskhod-2 successfully carried out the the world’s first ever spacewalk, which was a remarkable achievement and gave impetus to further research in developing methods for extravehicular activity in outer space.

In developing and testing the systems that allowed the first spacewalk, the employees of Zvezda worked with promptness and enthusiasm. Indeed, only nine months went by from the signing of the technical specifications for the airlock and spacesuit on 9 June 1965 to A. Leonov’s spacewalk on 18 March 1965. This was noted on the celebratory meeting of the Zvezda team with the cosmonauts shortly after the flight.

The museum of the Zvezda Research Development and Production Enterprise (RD&PE)
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Curator - The museum of the Zvezda Research Development and Production Enterprise (RD&PE)

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