Neutral buoyancy pool
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A neutral buoyancy pool or neutral buoyancy tank is a pool of water in which
neutral buoyancy Neutral buoyancy occurs when an object's average density is equal to the density of the fluid in which it is immersed, resulting in the buoyant force balancing the force of gravity that would otherwise cause the object to sink (if the body's de ...
is used to train astronauts for
extravehicular activity Extravehicular activity (EVA) is any activity done by an astronaut in outer space outside a spacecraft. In the absence of a breathable atmosphere of Earth, Earthlike atmosphere, the astronaut is completely reliant on a space suit for environme ...
and the development of procedures. These pools began to be used in the 1960s and were initially just recreational
swimming pools A swimming pool, swimming bath, wading pool, paddling pool, or simply pool, is a structure designed to hold water to enable Human swimming, swimming and associated activities. Pools can be built into the ground (in-ground pools) or built abo ...
; dedicated facilities would later be built.


Space agencies


NASA

Prior to May 1960, NASA recognized the possibility of underwater neutral buoyancy simulations, and began testing their efficacy. NASA engaged Environmental Research Associates, a company based in
Baltimore Baltimore is the most populous city in the U.S. state of Maryland. With a population of 585,708 at the 2020 census and estimated at 568,271 in 2024, it is the 30th-most populous U.S. city. The Baltimore metropolitan area is the 20th-large ...
, to try neutral buoyancy simulations first in a pool near
Langley Research Center The Langley Research Center (LaRC or NASA Langley), located in Hampton, Virginia, near the Chesapeake Bay front of Langley Air Force Base, is the oldest of NASA's field centers. LaRC has focused primarily on aeronautical research but has also ...
. Visitors and other issues disturbed those efforts, so they moved the operation to a swimming pool at the
McDonogh School McDonogh School is a private, coeducational, PK-12, non-denominational school situated on an 800-acre campus in Owings Mills, Maryland, United States. McDonogh enrolls 1,460 students, approximately 75 of whom participate in the Upper School's ...
in Maryland, where
Scott Carpenter Malcolm Scott Carpenter (May 1, 1925 – October 10, 2013) was an American naval officer and aviator, test pilot, aeronautical engineer, astronaut, and aquanaut. He was one of the Mercury Seven astronauts selected for NASA's Project Mercury ...
was the first astronaut to participate
suited "Suited" is a single (music), single by South African singer-songwriter Shekhinah (singer), Shekhinah. It was released on 14 July 2017 by Columbia Records and Sony Music Entertainment, SME Africa as the first single from her debut studio album ' ...
. Then, after difficult EVAs through
Gemini 11 Gemini 11 (officially Gemini XI) With Gemini IV, NASA changed to Roman numerals for Gemini mission designations. was the ninth crewed spaceflight mission of NASA's Project Gemini, which flew from September 12 to 15, 1966. It was the 17th crewed ...
in mid-September 1966, the Manned Spacecraft Center (later renamed the
Johnson Space Center The Lyndon B. Johnson Space Center (JSC) is NASA's center for human spaceflight in Houston, Texas (originally named the Manned Spacecraft Center), where human spaceflight training, research, and flight controller, flight control are conducted. ...
) fully understood the importance of testing procedures underwater, and sent the
Gemini 12 Gemini 12 (officially Gemini XII) With Gemini IV, NASA changed to Roman numerals for Gemini mission designations. was a 1966 crewed spaceflight in NASA's Project Gemini. It was the 10th and final crewed Gemini flight (Gemini 1 and Gemini 2 were ...
crew to train at McDonogh.Otto F. Trout, Jr., Harry L. Loats, Jr., and G. Samuel Mattingly "NASA Contract NAS1-4059 with supplemental agreements" January 1966


Neutral Buoyancy Simulator (NBS)

The Neutral Buoyancy Simulator, located at the
Marshall Spaceflight Center Marshall Space Flight Center (officially the George C. Marshall Space Flight Center; MSFC), located in Redstone Arsenal, Alabama (Huntsville, Alabama, Huntsville postal address), is the Federal government of the United States, U.S. government's ...
in Alabama, operated from 1967 through 1997. The facility had three tanks. The first had a diameter of and a depth of . The second tank was built in 1966 and had a diameter of and a depth of . A third tank was added around 1968 for Skylab and other planned projects; it had a diameter of and was deep. Training in the NBS decreased when the Johnson Space Center opened its own neutral buoyancy pool in 1980, it eventually was closed in 1997.


Water Immersion Facility (WIF)

WIF was used for the Gemini and Apollo programs and was located in Building 5 at the Johnson Space Center in Houston, Texas. The pool had a diameter of and a depth of .


Weightless Environment Training Facility (WETF)

WETF, in operation from 1980 through 1998, was located in Building 29 at the Johnson Space Center in Houston, Texas. The dimensions of the pool were by , with a depth of .


Neutral Buoyancy Laboratory (NBL)

In the late 1980s, NASA began to consider replacing the WETF, which was too small to hold useful mock-ups of many of the space station components planned for Space Station ''Freedom'', which later morphed into the
International Space Station The International Space Station (ISS) is a large space station that was Assembly of the International Space Station, assembled and is maintained in low Earth orbit by a collaboration of five space agencies and their contractors: NASA (United ...
. NASA purchased the then-processing facility from
McDonnell Douglas McDonnell Douglas Corporation was a major American Aerospace manufacturer, aerospace manufacturing corporation and defense contractor, formed by the merger of McDonnell Aircraft and the Douglas Aircraft Company in 1967. Between then and its own ...
in the early 1990s, and began refitting it as a neutral-buoyancy training center in 1994 with construction ending in December 1995. The NBL began operation in 1997. The NBL is located at the Sonny Carter Training Facility, near the
Johnson Space Center The Lyndon B. Johnson Space Center (JSC) is NASA's center for human spaceflight in Houston, Texas (originally named the Manned Spacecraft Center), where human spaceflight training, research, and flight controller, flight control are conducted. ...
in Houston. The pool's dimensions are by , with a depth of .


Roscosmos

Following the
Voskhod 2 Voskhod 2 () was a Soviet crewed space mission in March 1965. The Vostok-based Voskhod 3KD spacecraft with two crew members on board, Pavel Belyayev and Alexei Leonov, was equipped with an inflatable airlock. It established another milestone ...
mission, a group at the
Gagarin Cosmonaut Training Center The Yuri A. Gagarin State Scientific Research-and-Testing Cosmonaut Training Center (GCTC; Russian: Центр подготовки космонавтов имени Ю. А. Гагарина) is a Russian training facility responsible for trai ...
(GCTC) proposed training for EVAs in a pool. In September 1969, GCTC created a working group to further study the idea, and some experiments were performed in their swimming pool near the end of that year. In 1970, cosmonauts
Andriyan Nikolayev Andriyan Grigoryevich Nikolayev ( Chuvash and ; 5 September 1929 – 3 July 2004) was a Soviet cosmonaut. In 1962, aboard Vostok 3, he became the third Soviet cosmonaut to fly into space. Nikolayev was an ethnic Chuvash and because of it con ...
and
Vitaly Sevastyanov Vitaly Ivanovich Sevastyanov (; 8 July 1935 – 5 April 2010) was a Soviet cosmonaut and an engineer who flew on the Soyuz 9 and Soyuz 18 missions. He trained as an engineer at the Moscow Aviation Institute and after graduation in 1959, j ...
visited NASA's new -diameter pool at Marshall. Sevastyanov was even allowed to don a training suit and enter the pool. Following the visit, further interest in a similar facility began to grow within the Soviet space program. In November 1973, it was officially decided to construct a dedicated pool; until then, the center's swimming pool continued to be used.


Hydro Lab

Hydro Lab was completed in early 1980; the pool there has a diameter of and a depth of .


CNSA


Neutral Buoyancy Facility (NBF)

The Chinese NBF is located at the China Astronaut Research and Training Center in Beijing. It has a diameter of and depth of . Construction began in 2005 and was completed in November 2007. Operations began in 2008.


ESA


Neutral Buoyancy Facility (NBF)

The European NBF is located at the European Astronaut Center in Cologne, Germany. It has an
octagonal In geometry, an octagon () is an eight-sided polygon or 8-gon. A '' regular octagon'' has Schläfli symbol and can also be constructed as a quasiregular truncated square, t, which alternates two types of edges. A truncated octagon, t is a hex ...
shape and dimensions of by , with a depth of . Operations began in 2002.


JAXA


Weightlessness Environment Test System (WETS)

WETS was located at the
Tsukuba Space Center The Tsukuba Space Center (TKSC) also known by its radio Call sign, callsign Tsukuba, is the operations facility and headquarters for the Japan Aerospace Exploration Agency (JAXA) located in Tsukuba Science City in Ibaraki Prefecture. The facil ...
in Ibaraki, Japan. It opened in 1997 and closed in 2011 due to extensive earthquake damage. The pool had a diameter of , and depth of .


Others


University of Maryland Neutral Buoyancy Research Facility (NBRF)

The NBRF is located at the
University of Maryland The University of Maryland, College Park (University of Maryland, UMD, or simply Maryland) is a public land-grant research university in College Park, Maryland, United States. Founded in 1856, UMD is the flagship institution of the Univ ...
in the US. The pool has a diameter of and a depth of . It was built in 1992, and is the only neutral buoyancy facility on a university campus. The NBRF is part of the
Space Systems Laboratory Space Systems Laboratory is a name commonly used by university laboratories engaged in the research of technologies used for human activities in space. Examples include: * Drexel Space Systems Laboratory at the Drexel University in Philadelphia, ...
(SSL) which was originally located at the
Massachusetts Institute of Technology The Massachusetts Institute of Technology (MIT) is a Private university, private research university in Cambridge, Massachusetts, United States. Established in 1861, MIT has played a significant role in the development of many areas of moder ...
(MIT). It split from MIT when the SSL was awarded a grant from NASA to build a dedicated neutral buoyancy pool. Since there was not enough space at MIT for the pool, it was decided to move the SSL to the University of Maryland.


Underwater Astronaut Trainer (UAT)

The UAT is located at the United States Space and Rocket Center, home of Space Camp and Space Academy, in Huntsville, AL. 30 feet wide and 24 feet deep, it was designed by
Homer Hickam Homer Hadley Hickam Jr. (born February 19, 1943) is an American author, Vietnam War veteran, and a former NASA engineer who trained the first Japanese astronauts. His 1998 memoir '' Rocket Boys'' (also published as ''October Sky'') was a ''Ne ...
, a NASA engineer famous for writing ''Rocket Boys'', adapted into the film ''
October Sky ''October Sky'' is a 1999 American biographical drama film directed by Joe Johnston, and starring Jake Gyllenhaal, Chris Cooper, Chris Owen, and Laura Dern. The screenplay by Lewis Colick, based on the book of the same name, tells the ...
''. Opened in 1986, it is still active.


Neutral-buoyancy training

During training exercises, neutral-buoyancy diving is used to simulate the
weightlessness Weightlessness is the complete or near-complete absence of the sensation of weight, i.e., zero apparent weight. It is also termed zero g-force, or zero-g (named after the g-force) or, incorrectly, zero gravity. Weight is a measurement of the fo ...
of space travel. To achieve this effect, suited astronauts or pieces of equipment are lowered into the pool using an
overhead crane An overhead crane, commonly called a bridge crane, is a type of crane found in industrial environments. An overhead crane consists of two parallel rails seated on longitudinal I-beams attached to opposite steel columns by means of brackets. ...
and then weighted in the water by support divers so that they experience minimal
buoyant force Buoyancy (), or upthrust, is the force exerted by a fluid opposing the weight of a partially or fully immersed object (which may be also be a parcel of fluid). In a column of fluid, pressure increases with depth as a result of the weight of t ...
and minimal rotational moment about their
center of mass In physics, the center of mass of a distribution of mass in space (sometimes referred to as the barycenter or balance point) is the unique point at any given time where the weight function, weighted relative position (vector), position of the d ...
. The suits worn by trainees in the NBL are down-rated from fully flight-rated
EMU The emu (; ''Dromaius novaehollandiae'') is a species of flightless bird endemism, endemic to Australia, where it is the Tallest extant birds, tallest native bird. It is the only extant taxon, extant member of the genus ''Dromaius'' and the ...
suits like those in use on the Space Shuttle and International Space Station. Divers breathe
nitrox Nitrox refers to any gas mixture composed (excepting trace gases) of nitrogen and oxygen. It is usually used for mixtures that contain less than 78% nitrogen by volume. In the usual application, underwater diving, nitrox is normally distinguished ...
while working in the tank.


Training challenges

One disadvantage of neutral-buoyancy diving as a simulation of microgravity is the significant amount of
drag Drag or The Drag may refer to: Places * Drag, Norway, a village in Tysfjord municipality, Nordland, Norway * ''Drág'', the Hungarian name for Dragu Commune in Sălaj County, Romania * Drag (Austin, Texas), the portion of Guadalupe Street a ...
created by the water. This makes it difficult to set an object in motion, and difficult to keep it in motion. It also makes it easier to keep the object stationary. This effect is the opposite of what is experienced in space, where it is easy to set an object in motion, but very difficult to keep it still. Generally, drag effects are minimized by doing tasks slowly in the water. Another downside of neutral buoyancy simulation is that astronauts are not weightless ''within'' their suits, meaning that as divers tilt their suits they are pressed against whatever inside surface is facing down. This can be uncomfortable in certain orientations, such as heads-down. Thus, precise suit sizing is critical.


Images


See also

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References

{{Underwater diving, other Swimming pools