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max8166
2006-Jul-24, 10:34 AM
On the International Space Station (ISS) they have some very large solar arrays to collect sunlight to convert into electricity to power the station.

http://antwrp.gsfc.nasa.gov/apod/image/0607/iss_sts121_big.jpg

In a recent news article by space.com, managers are talking about the next payload destined for Atlantis to be launched at the end of August. Thay state
Perhaps one of the most impressive parts of the linked segments is the 10-foot-wide Solar Alpha Rotary Joint in the middle, which keeps the solar panels aimed at the sun.

"The entire space station outboard of that joint will be rotating 360 degrees every orbit," Hardison said. "It'll be quite something to see, that's for sure."
http://www.space.com/missionlaunches/ft_060721_sts115_trusses.html


My question is why don't they just set the entire space station rotating once every orbit? Surely once a rotation is started it would continue.

My only idea is it is because they want to be able to point the communication antenna directly at the ground, however I would have thought it would be alot easier to rotate the communication antenna than those massive solar arrays.

Anyone think of another good reason?

Tog
2006-Jul-24, 10:47 AM
On the International Space Station (ISS) they have some very large solar arrays to collect sunlight to convert into electricity to power the station.

http://antwrp.gsfc.nasa.gov/apod/image/0607/iss_sts121_big.jpg

In a recent news article by space.com, managers are talking about the next payload destined for Atlantis to be launched at the end of August. Thay state

My question is why don't they just set the entire space station rotating once every orbit? Surely once a rotation is started it would continue.

My only idea is it is because they want to be able to point the communication antenna directly at the ground, however I would have thought it would be alot easier to rotate the communication antenna than those massive solar arrays.

Anyone think of another good reason?

Docking. If the station is rotating even only once per day, that rotation may still be enough to screw up a docking procedure when the next batch of supplies arrives.

Would the ISS have anything like tidal locking to slow it if were rotating?

max8166
2006-Jul-24, 10:58 AM
Rotating a shuttle to the same degree would not be a problem and I'm sure it wouldn't even be noticable to the commander of the shuttle especially if you had the docking port on a rotational axis. Having said that perhaps it would create a micro gravity which the station is just not built to withstand.

gwiz
2006-Jul-24, 11:03 AM
Maybe they want to keep scientific instruments pointed towards earth.

Jeff Root
2006-Jul-24, 01:09 PM
The International Space Station is gravity-gradient stabilized.
Earth's gravity pulls it into a stable position with one end down
and the other end up. Lots of things on the station are designed
for that orientation.

ISS is nowhere near rotationally symmetrical, unlike the big
wheel-shaped space station in 2001: A Space Odyssey. It would
be almost impossible for it to rotate and have anything dock with it.
The docking port would be moving sideways in front of you. Very
not good.

-- Jeff, in Minneapolis

papageno
2006-Jul-24, 01:34 PM
Rotating the station helps distributing the heat from the Sun in a more uniform manner.