How direction of satellite changes

[lalu]

how the direction of artifical satellites are changing in outer space by controlling from earth? how the reaction force is created at space without any medium .

 

[Bandersnatch]

Hi lalu,

Do you mean changing orientation(aka attitude control)?
It's mostly either by tiny rockets(RCS, or Reaction Control System), which use the principle of conservation of momentum, or by flywheels - a solar-powered electric engine spins a whell in one direction, and the spacecraft rotates in the othe, according to the conservation of angular momentum.

http://en.wikipedia.org/wiki/Reaction_control_system
http://en.wikipedia.org/wiki/Reaction_wheel
http://en.wikipedia.org/wiki/Attitude_control

 

[D H]

We've had this question arise a number of times here. It springs from a mistaken concept that rockets need something to push against. In this view, rockets launch because the exhaust pushes against the ground and thus forces the rocket to accelerate upward. This is a mistaken concept of how rockets work.

Rockets don't need something to push against. In fact, ground effects make rockets less efficient. Rockets work better when they are far away from the ground, and better yet when they are completely out of the atmosphere.

Rockets work because of conservation of linear momentum and angular momentum. The rocket exhaust going away from the rocket has some amount of linear momentum and angular momentum. The conservation laws dictate that the rocket's linear and angular momentum must change to match whatever is carried away.

 

[cenzi]

Hi lalu,

Do you mean changing orientation(aka attitude control)?
It's mostly either by tiny rockets(RCS, or Reaction Control System), which use the principle of conservation of momentum, or by flywheels - a solar-powered electric engine spins a whell in one direction, and the spacecraft rotates in the othe, according to the conservation of angular momentum.

http://en.wikipedia.org/wiki/Reaction_control_system
http://en.wikipedia.org/wiki/Reaction_wheel
http://en.wikipedia.org/wiki/Attitude_control

I personally prefer mini rokets. Interesting to know. Actually there are lots of propultion techs.