The mission of the Neutral Buoyancy Lab (NBL) is to prepare for space missions involving space walks (or EVA, extravehicular activity). NASA team members utilize the NBL to develop flight procedures, verify hardware compatibility, train EVA astronauts, and refine EVA procedures during flight that are necessary to ensure mission success. The ability to successfully and predictably perform on-orbit assembly and maintenance operations is critical to future space endeavors. EVA is a cornerstone for current and future space initiatives and the NBL is the foundation for successful EVA mission preparation.
Neutral Buoyancy
What is neutral buoyancy and how is it like zero-gravity? Neutral buoyancy is the term used to describe something that has an equal tendency to float as it does to sink. Articles that are configured to be neutrally buoyant (which is accomplished with a combination of weights and flotation devices) seem to "hover" under water and large, neutrally buoyant items can be easily manipulated much like on orbit. However, there are two important differences. First, a suited astronaut in the NBL is not truly weightless; while it is true the astronauts feel their weight while in the suit (they are lying or standing in the suit depending on its orientation; that is one reason why suit fit is so critical). Second, water drag acts to hinder motion; this makes some things easier to do in the NBL than on orbit and some things more difficult. Both effects are unlike the conditions of space and must be recognized during EVA training. However, even with these limitations, neutral buoyancy is currently the best available method for long-duration EVA training.
NBL Size
The NBL was sized to perform two activities simultaneously; each uses mockups sufficiently large to produce meaningful training content and duration. It is 202 ft in length, 102 ft in width, and 40 ft in depth (20 ft above ground level and 20 ft below) and holds 6.5 million gallons of water. Even at this size, the International Space Station, at 350' x 240' when complete, will not fit inside the NBL.
Remote Manipulator Systems
Full-scale working models of the shuttle and station robotic arms are critical NBL components. Both models are hydraulically operated to improve durability and minimize safety concerns. The flight articles, which are electrically operated, are not strong enough to lift themselves on Earth (though they can manipulate tens of thousands of pounds in zero-gravity).
Extravehicular Mobility Unit
The Extravehicular Mobility Unit (EMU) is an integrated spacesuit and life support system with additional items necessary for astronauts to conduct activity outside the Space Shuttle Orbiter. Astronauts use the EMU to conduct external inspections of and repairs to the orbiter, to take photographs and for use during deployment, retrieval and servicing of payloads. The EMU is like a personal spacecraft, in that it provides a self-contained pressurized enclosure that includes fresh oxygen, the removal of carbon dioxide, temperature control and protection from micro-meteoroids. The following pictures were taken while astronauts were training for a mission to modify the Hubble Space Telescope. They are shown working in a full scale mock-up of the Shuttle bay with working models of the Hubble parts which will be needed for the mission.
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