An astronaut training in the NBL

The Neutral Buoyancy Laboratory or NBL is a training facility for astronauts maintained by NASA's Johnson Space Center in Houston, Texas. The NBL consists of a large pool of water in which astronauts may perform simulated EVA tasks in preparation for upcoming missions, for example, construction activities related to the International Space Station. NASA logo Listen to this article · (info) This audio file was created from an article revision dated 2005-09-01, and does not reflect subsequent edits to the article. ... An aerial view of the complete Johnson Space Center facility in Houston, Texas in 1989. ... Houston redirects here. ... This article does not cite its references or sources. ... Astronaut Bruce McCandless on an untethered EVA Extra-vehicular activity (EVA) is work done by an astronaut away from the Earth and outside of his or her spacecraft. ... International Space Station insignia ISS Statistics Crew: 3 As of July 6, 2006 Perigee: 352. ...

The principle of neutral buoyancy is used to simulate the weightless environment of space. Suited astronauts are weighted in the water by support divers so that they experience no buoyant force and no rotational moment about their center of mass. The suits worn in the NBL are down-rated from fully flight-rated EMU suits like those in use on the space shuttle and International Space Station. In physics, buoyancy is an upward force on an object immersed in a fluid (i. ... In physics, the moment of force (often just moment, though there are other quantities of that name such as moment of inertia) is a quantity that represents the magnitude of force applied to a rotational system at a distance from the axis of rotation. ... In physics, the center of mass (or centre of mass) of a system of particles is a specific point at which, for many purposes, the systems mass behaves as if it were concentrated. ... NASA portrait of American Astronaut Thomas Akers, wearing a Shuttle EMU. The Space Shuttle/International Space Station Extravehicular Mobility Unit (EMU) is an independent anthropomorphic system that provides environmental protection, mobility, life support, and communications for a Shuttle or ISS crew member to perform extra-vehicular activity (EVA) in earth... The Space Shuttle Columbia seconds after engine ignition, 1981 (NASA). ... ISS is an abbreviation, acronym, or initialism that may refer to: The International Space Station is a joint international project to build and maintain an orbiting space station. ...

The NBL tank itself is 202 ft. in length, 102 ft. wide, and 40 ft. deep, and contains 6.2 million gallons of water.^[1]

One downside of using neutral bouyancy to simulate EVA is the presence of drag. Generally, this is overcome by doing tasks slowly in the water, to minimize the effect of drag on the exertion required to complete a task. Another downside is that astronauts are not weightless within the suit, and thus suit sizing is critical. An object falling through a gas or liquid experiences a force in direction opposite to its motion. ...

The other primary method used by NASA to simulate microgravity is the so-called "Vomit Comet", an aircraft which performs a number of parabolic climbs and descents to give its occupants the sensation of zero gravity. The vomit comet reduces the problem of drag in weightless simulation. The main shortcoming of this method is its time limitations - periods of weightlessness are limited to around 25 seconds, interspersed with periods of acceleration of around 2 g's as the aircraft pulls out of its dive and readies for the next run. This is obviously not suitable for practicing EVAs, which usually last several hours. NASA logo Listen to this article · (info) This audio file was created from an article revision dated 2005-09-01, and does not reflect subsequent edits to the article. ... Astronauts on the International Space Station display an example of weightlessness Weightlessness is the experience (by people and objects) during freefall, of having no weight. ... Weightlessness inside the Vomit Comet The Vomit Comet was the nickname given to the aircraft used by NASAs Reduced Gravity Research Program. ...

The Neutral Buoyancy Research Facility at the University of Maryland's Space Systems Laboratory performs research into EVA techniques and robotic interaction using neutral buoyancy as a basis for weightless simulation. The University of Maryland, College Park (also known as UM, UMD, or UMCP) is a public university located in College Park, Maryland, just outside Washington, D.C., USA. As the flagship institution of the University System of Maryland, the university is most often referred to as the University of Maryland...

References

^[1] NASA Neutral Buoyancy Lab website