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The prime motivation for doing scientific research in space rather than on Earth

is its unique microgravity environment, where researchers can study the unique

behavior of organisms and the physics of fluids and materials. The

Microgravity Analysis Software System (MASS)developed byNASA Glenn

Research CenterandZIN Technologies,both of Cleveland, Ohio,

characterizes the microgravity environment for such space-based science

experiments.

The Principal Investigator Microgravity Service (PIMS) Project uses MASS

technology to collect and analyze microgravity acceleration data, which it

receives from the International Space Station. The real-time display and off-line

analysis perform all of the data analysis, while the other components involved

acquire, route, and archive data. Previous versions of microgravity analysissoftware were customized for each shuttle flight with an operation length of

about 10 days; MASS was designed to collect and analyze data continuously for

10 years.

Beyond space, MASS may bring a better understanding to lowering vehicle

exhaust emissions, increasing fire safety, and improving fuel economy for

automobiles and aircraft.

It is common for astronauts to experience sever disorientation when they firstencounter micro-gravity. Often this sensory ``confusion'' leads to space sickness

or space adaptation syndrome. Since sound localization is a critical skill that

people use to regain their bearings, careful study of sound localization in a

micro-gravity environment would be useful for future space flights. A better

understanding of directional hearing may yield new insights into space sickness

and aid in the design of spacecraft, space communication systems, and earth-

bound space simulators.

Your true weight is caused by gravity--it is the force exerted on you by gravity;

usually the earth's gravity. Your apparent weight is the sum of your true weight

and a fictitious force associated with your acceleration.

there aremany advantages to performing scientificexperiments under conditions

where the apparentweight of the experiment system is reduced. Thename given

to such a research environment ismicrogravity. The prefix micro- (m) derives

fromthe original Greek mikros meaning small. By thisdefinition, a

microgravity environment is one inwhich the apparent weight of a systemis smallcompared to its actual weight due to gravity.

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Thisexample attempts to provide insight into whatmight be expected if the local

accelerationenvironment would be reduced by six orders ofmagnitude from 1 g

to 10-6 g,If you dropped a rock from a roof that was fivemeters high, it would

take just one second toreach the ground. In a reduced gravityenvironment with

one percent of Earthsgravitational pull, the same drop would take 10seconds.

In a microgravity environment equal toone-millionth of Earths gravitational

pull, thesame drop would take 1,000 seconds or about 17minutes!

Researchers can create microgravity conditions intwo ways. Because

gravitational pull diminisheswith distance, one way to create a

microgravityenvironment (following the quantitative definition)is to travel away

from Earth. To reach a pointwhere Earths gravitational pull is reduced

toonemillionth cf that at the surface, you wouldhave to travel into space adistance of 6.37million kilometers from Earth (almost 17 timesfarther away

than the Moon, 1400 times thehighway distance between New York City and

LosAngeles, or about 70 million football fields). Thisapproach is impractical,

except for automatedspacecraft, because humans have yet to travelfarther away

from Earth than the distance to theMoon. However, freefall can be used to

create amicrogravity environment consistent with ourprimary definition of

microgravity

Your true weight is caused by gravity--it is the force exerted on you by gravity;

usually the earth's gravity. Your apparent weight is the sum of your true weight

and a fictitious force

Free fall is motion with no acceleration other than that provided by gravity.

Since this definition does not specify velocity, it also applies to objects initially

moving upward. Although the definition specifically excludes all other forces

such as aerodynamic drag, in nontechnical usage falling through an atmosphereis also referred to as free fall.

Examples of objects in free fall include:

* A spacecraft (in space) with its rockets off (e.g. in a continuous orbit, or going

up for some minutes, and then down)

* The Moon orbiting around the Earth.

* An object dropped in a drop tower for a physics demonstration at NASA's

Zero-G Research Facility

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Initially, the aircraft climbs with a pitch angle of 45 degrees using engine thrust

and elevator controls. The sensation of weightlessness is achieved by reducing

thrust and lowering the nose to maintain a neutral, or "straight and level"

configuration (0 degree angle of attack). Weightlessness begins while ascending

and lasts all the way "up-and-over the hump", until the craft reaches a

downward pitch angle of 30 degrees. At this point, the craft is pointed

downward at high speed, and must begin to pull back into the nose-up attitude

to repeat the maneuver. The forces are then roughly twice that of gravity on the

way down, at the bottom, and up again. This lasts all the way until the aircraft is

again halfway up its upward trajectory, and the pilot again reduces the thrust

and lowers the nose

This is how the Space Shuttle stays in orbit. Itlaunches on a path that arcs aboveEarth so thatthe Orbiter travels at the right speed to keep itfalling while

maintaining a constant altitude abovethe surface. For example, if the Shuttle

climbs toa 320 kilometer high orbit, it must travel at aspeed of about 27,740

kilometers per hour toachieve a stable orbit. At that speed and altitude,the

Shuttle executes a falling path parallel to thecurvature of Earth. Because the

Space Shuttle isin a state of freefall around Earth and due to theextremely low

friction of the upper atmosphere,the Shuttle and its contents are in a high-

qualitymicrogravity environment.

Because of gravity, the cooler, more densewater sinks to the bottom of the

container and theheated water rises to the top due to buoyancy. Acirculation

pattern is produced that mixes the hotwater with the colder water. This is an

example ofbuoyancy driven (or gravity driven) convection

The different scientific research areas that are studied in microgravity include

biotechnology, combustion science, fluid physics, fundamental physics, and

materials science.