Neutral buoyancy simulation with astronauts immersed in a neutral buoyancy pool, in pressure suits, can help to prepare astronauts for the difficult task of working while outside a spacecraft in an apparently weightless environment.
History
Extra-vehicular activity (EVA), working outside the space vehicle, was one of the goals of the Gemini Program during the 1960s. The astronauts were trained in the “zero gravity” condition by flying a parabolic trajectory in an aircraft that caused reduced gravity for thirty second intervals.
Pioneers without sufficient training The Russian cosmonaut Alexei Leonov was the first to egress his vehicle while travelling in orbit above the Earth. Shortly after, Ed White, Gemini IV, was the first American astronaut to egress a vehicle while in space. These were demonstrations of a capability to get out of and back into the vehicle but included no EVA tasks. The next three flights to demonstrate an EVA capability were Gemini IX-A, X, and XI. Each of these flights exposed problems with performance of EVA tasks. Working in pressure suits while in the constant weightlessness of orbital spaceflight was more complex and difficult than had been anticipated. NASA determined that training for EVA tasks required further development.
Origins of neutral buoyancy training In July 1966 the Gemini Program joined in a NASA Langley Research Center contract to include an evaluation of Gemini EVA tasks. The contractor, Environmental Research Associates of Randallstown, MD had already begun developing a neutral buoyancy simulation capability in 1964. This capability for pressure suited subjects was initially developed in 1964 by utilizing an indoor swimming pool at a private school (McDonogh School near Baltimore). Initially, these early underwater simulations were simply designed to test the ability of subjects to move about mock-up airlocks and weights were not attached to the subjects. Quickly, Environmental Research Associates' submerged testing evolved into proper neutral buoyancy simulation, featuring weighted subjects and numerous safety divers on hand during given sessions.
First evaluation by astronauts Scott Carpenter was the first astronaut to evaluate the contractor's operation, in a "wet workshop" simulation. The task was to remove bolts while in a submerged simulated airlock. The bolt removal task was designed to create access to a spent S-IVB dome. Carpenter's evaluation of the simulation was favorable and NASA quickly provided mockups of Gemini vehicles and docking components to facilitate further development of EVA capabilities via neutral buoyancy training. Astronaut Gene Cernan first visited the McDonogh School indoor pool facility for post-mission evaluation of problems that he encountered during his Gemini IX-A EVA. NASA then modified the contract to include pre-mission training of Gemini XII astronaut, Buzz Aldrin. Astronaut Cernan also participated in this pre-mission training, as he was in a backup role to Aldrin as pilot of Gemini XII.
Gemini XII EVA training Aldrin trained for the original Gemini XII EVA version which was then revised to eliminate the task of using a Manned Maneuvering Unit. Aldrin returned to the McDonogh facility and trained for the final version of his EVA. NASA considered the flight EVA to be a total success, and Aldrin again returned to McDonogh to perform a post-mission evaluation of the EVA. The post-mission evaluation verified the value of using neutral buoyancy simulation training before attempting all of the EVA tasks while wearing a pressure suit and working in the hostile environment of space. Aldrin himself recognized some minor flaws of neutral buoyancy training, but described the method to have a "considerable advantage" over Keplerian trajectory aircraft.
Beyond Gemini After the successful EVAs in the Gemini XII mission, NASA constructed tanks for neutral buoyancy simulation: The Water Immersion Facility at the Manned Spacecraft Center and the Neutral Buoyancy Simulator at Marshall Space Flight Center. Following use of those facilities during the Apollo and Skylab programs, NASA eventually constructed the Weightless Environment Training Facility at the Manned Spacecraft Center in Houston and later the Neutral Buoyancy Laboratory, where Shuttle and Space Station astronauts are trained in neutral buoyancy. Astronauts and cosmonauts also train at the Yuri Gagarin Cosmonaut Training Center near Moscow. These accomplishments were summarized in a feature article published by the Baltimore Sun newspaper in 2009. In September 2011, the Gemini XLV Symposium included a review of these accomplishments by G. Samuel Mattingly and featured remarks by astronauts Richard Gordon, Tom Jones, and Buzz Aldrin.
Rescuing Skylab During the Skylab 2 mission, astronauts Conrad and Kerwin successfully opened a solar panel that had not automatically deployed after launch. To perform this task, the astronauts trained underwater in the Neutral Buoyancy Simulator at the Marshall Space Flight Center. However, due to differences between the design of the mock-up used for training and what they found at Skylab, the astronauts used makeshift tools and redesigned how they would accomplish the task while they were in outer space.
Characteristics
Need for simulation Astronauts rehearse extra-vehicular activity tasks in underwater neutral buoyancy before attempting those tasks in space to gain an understanding that they cannot use their weight to provide a force and that they may move or reposition themselves if they provide a propulsive force in any vector, either planned or inadvertent. Articles describing neutral buoyancy simulation generally point out that the astronaut's spacesuit is made neutrally buoyant but that the astronaut still feels gravity inside the spacesuit so the fit of the suit is very important, and that moving around in water, a viscous fluid, creates drag that is not present in EVA.
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