# Thread: L4/5 and Coriolis Force

1. ## L4/5 and Coriolis Force

From http://map.gsfc.nasa.gov/m_mm/ob_techorbit1.html :
In the above contour plot we see that L4 and L5 correspond to hilltops and L1, L2 and L3 correspond to saddles (i.e. points where the potential is curving up in one direction and down in the other). This suggests that satellites placed at the Lagrange points will have a tendency to wander off (try sitting a marble on top of a watermelon or on top of a real saddle and you get the idea). A detailed analysis confirms our expectations for L1, L2 and L3, but not for L4 and L5. When a satellite parked at L4 or L5 starts to roll off the hill it picks up speed. At this point the Coriolis force comes into play - the same force that causes hurricanes to spin up on the earth - and sends the satellite into a stable orbit around the Lagrange point.
I would like an explanation as to how the coriolis force plays in that, i.e. what axis the orbit would be later, or what direction that force vector is.
Also, "roll off the hill" in which direction according to the rotational plane? After all, the effect of Coriolis force depends on direction too...

If you wanted to escape that force, what would be the nicest direction? Somebody claimed we didn't have the technology yet to escape the pulling force of L4/5, anybody knows more about that? What escape vector would be most promising according to those calculations?

There's another link on that, http://donar.physik.uni-bremen.de/nl...er/node19.html , but I haven't been able to make anything out of it.

Oh yes, and I'm back. Missed me?

2. What? I thought L1, L2, L3 were unstable and L4 and L5 were stable.

3. Originally Posted by Glom
What? I thought L1, L2, L3 were unstable and L4 and L5 were stable.
Exactly that is the point. The article says they are stable because of the coriolis force in the system. I wanted a more specific explanation of why this is so.

4. Originally Posted by jokergirl
Originally Posted by Glom
What? I thought L1, L2, L3 were unstable and L4 and L5 were stable.
Glom, I thought you were gone. What brought you back? Ah, Lagrange points.
Exactly that is the point. The article says they are stable because of the coriolis force in the system. I wanted a more specific explanation of why this is so.
They appear to explain it in their detailed analysis link. It's half a megabyte, I haven't read it yet.

5. If you look at the times of my post above and my goodbye post, you'll see this one came first.

6. LOL! Welcome back anyway!

#### Posting Permissions

• You may not post new threads
• You may not post replies
• You may not post attachments
• You may not edit your posts
•