Berkut spacesuit
베르쿠트 우주복
A soft-type EVA spacesuit developed by NPP Zvezda in 1964–1965 for the Voskhod 2 mission. It was a modified SK-1 (Sokol) suit with additional thermal layers, a metal helmet, and a 45-minute KP-55 oxygen backpack, worn by Alexei Leonov on March 18, 1965, during the world's first spacewalk. In vacuum, the suit ballooned so severely that Leonov could not fit back into the airlock; he had to bleed oxygen through a pressure valve to regain flexibility and narrowly survived reentry.
In depth
Development Background
Voskhod 2 was the mission tasked with the world's first spacewalk. Since the existing SK-1 (Sokol) suit for Vostok was designed only for intra-vehicular activity, NPP Zvezda began modifying it in 1964, producing the Berkut in just over a year.
Technical Features
The Berkut was a soft-type suit with no rigid frame, featuring a three-layer shell (outer load-bearing layer plus primary and backup hermetic layers) and a multi-layer vacuum-insulated protective coverall. The helmet was a non-rotating aluminum-alloy unit with an aircraft-style light filter inside. The KP-55 backpack carried three oxygen cylinders and operated an open-cycle life-support system providing both breathing and cooling; oxygen flowed into the helmet, circulated through the suit, and vented into space. It had two pressure settings: 0.40 atm (nominal) and 0.27 atm.
Operational Crisis
On March 18, 1965, Leonov exited Voskhod 2 through the inflatable Volga airlock, tethered by a 7-meter safety line, and floated in space for 12 minutes and 9 seconds. In the vacuum, however, the Berkut ballooned dramatically: his fingers pulled back from the glove tips and the entire suit stiffened, making movement extremely difficult. The airlock was only 1.2 meters in diameter, and Leonov compounded the problem by entering headfirst. He ultimately opened the backup pressure valve, dropping internal pressure to 0.27 atm, and, drenched in sweat, forced himself back inside the airlock.
Legacy
The Berkut was worn only once, on Voskhod 2. The lessons learned, particularly the suit's inadequate joint flexibility and cooling, led directly to the development of the improved Yastreb (Ястреб, Hawk) EVA suit, and influenced spacesuit design on both sides of the space race.
Related people
Related historical events
Sources
- Russian Wikipedia (Беркут (скафандр)) — technical specifications, three-layer shell design, KP-55 backpack, two pressure settings, mass, 45-minute EVA duration, soft-type classification, NPP Zvezda development
- English Wikipedia (Berkut spacesuit) — derived from SK-1 suit, Voskhod 2 mission, two pressurization settings, helmet and protective clothing specs, 7-meter safety harness
- Astronautix (Berkut) — open-cycle environmental control system, ballooning and stiffness problems during Leonov's EVA, pressure valve bleed to 0.27 atm to re-enter airlock, only used on Voskhod 2
- Smithsonian Air & Space (Cathleen Lewis) — suit ballooning in vacuum, pressure settings 5.8 psi → 3.9 psi, heat buildup from body energy, Leonov entering airlock headfirst, cooling inadequacy as key lesson