Gravity gradient torque

[Sword7]

Folks,

That is very new to me when I research some. I now learned that NASA launched rockets into the parking orbit. I noticed that rockets do not follow orbital path so that its orientation is fixed around orbit. Rockets were slowly flipped back. When they are ready to leave earth, they reorient back to orbital path (direction vector) before it started engine.

However, I noticed that space shuttle and some satellites follow orbital path and always look down to earth ground. How do they keep orientation along orbital path?

Thanks,
Tim

 

[Urwumpe]

Like the name suggests: The stabilization comes from the difference in gravity force, the parts that are closer to Earth and pulled stronger towards it than the parts that are further away, which makes the spacecraft behave like a pendulum. After a while, it rotates about as fast as the spacecraft orbits Earth, any small differences due to moon, sun or planets just make it swing back and forth a bit.

For that to work, the spacecraft must have ideally have a dumbbell like mass distribution: Long and narrow, with the heavy parts at the ends (like for the shuttle: Engine section and pressurized cockpit at opposing ends, with only light stuff between). But gravity gradient exists for all spacecraft, even the ISS.