DAISY: The international space station...
It’s the satellite of science, paving the way for
future exploration, and habitation on worlds beyond our own...
But all that doesn’t come without challenges...
NASA has to work hard to keep ISS in orbit.
Thanks to math, the space agency can provide a boost to keep it going...
We’ll show you how they do it... next on real world...
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Construction of the International Space Station
got underway in 1998, thanks to NASA and space agencies
from several other nations of the world.
Since then they have been working to complete the project...
Lot’s of work is going on right now to enable ISS to
double its crew size from 3 to 6.
And the work that’s done on the station is helping
scientists understand how space conditions effect
people, plants, microorganisms, just about all of life.
This work will help pave the way as we move beyond ISS,
to lunar habitation, and human exploration of Mars and beyond.
But life in space doesn’t isn’t always easy...
Recently, astronauts in the space station had to hunker
down in the Soyez escape module, waiting to see if a
chunk of space debris, would hit the station.
The debris is a chunk of an upper stage rocket, used to
launch a GPS satellite, more than 15 years ago.
Fortunately, the debris passed harmlessly.
That was a pretty extreme situation. Usually the
station has enough advanced warning to fire its engines
and adjust its orbit, thus avoiding any space debris.
The Station also needs to adjust its orbit to compensate for gravity.
Gravity is the force of attraction between all masses in the universe.
RICHARD BYLES: Gravity is what holds us on earth.
DAISY: Richard Byles is the director of education at the
Virginia Air and Space Center.
RICHARD: Everything that has mass, has gravity.
DAISY: The weight of an object equals mass times gravity.
The mass of an object doesn’t change, but weight does,
depending on the force of gravity on that object.
Weight is directly proportional to the force of gravity on an object.
That’s why things weigh more on earth, than on the moon.
The earth has more mass, thus a stronger gravitational pull.
RICHARD: More mass equals more gravity.
That’s why all the planets, even the ones demoted to
dwarf planets like Pluto, way, way, way, way, way out
there, are held in the gravitational field of our sun.
DAISY: Each day, the station is pulled a little closer to earth,
losing about 90 meters of altitude. That’s about the
distance from goal line to goal line on a football field.
This is due to drag, as the space station collides with air molecules.
Drag slows the space station down, making it more
susceptible to the force of gravity.
This orbital decay is counteracted in several ways.
The stations main rockets can provide a small bump.
Resupply vessels that visit the ISS can push it up more.
And the space shuttle has the power to provide big boosts.
The orbital decay of the international space station can be charted on a graph...
But the rate of decay is not constant. The rate is
affected by several variables.
By plotting points showing the station’s altitude over
its lifetime, engineers can see trends and develop
strategies for keeping the station in orbit.
NASA needs to keep it above this point, 200 kilometers.
Below that, Earth’s atmosphere is too thick and
will cause too much drag on the ISS.
There is a pretty significant dip between 2000 and 2001.
This is because of a period of intense sunspots,
which warmed the Earth’s atmosphere causing it to
expand out to a higher altitude creating more drag
on the station, making it drop even faster.
Fortunately, the space shuttle was able to provide a big boost,
sending it back into a higher orbit... and you can see that on the graph.
Sunspot activity also follows patterns.
So the trends can be predicted.
Similar sunspot activity is predicted beginning in 2012,
by which time the space shuttle program is expected to be retired.
Adjustments will come from the thrust of the stations
two main engines and from resupply vessels that visit ISS.
NASA scientists and engineers are looking into new ways to
provide extra boosts that will keep the station in
orbit through the end of its mission.
Keep track of this and all of NASA’s missions at www.NASA.gov.
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