Lagrange points in Mars-Phobos system?

[Belisarius]

Hi fellow Spacers,

I'm looking for help in finding the L4 and L5 points in relation to the Mars-Phobos system, if they exist (and I suppose they do).
I'm assuming that Deimos is too tiny and too distant to exert any effect, so the key players are Mars, Phobos and Sol.

I've tried drifting out from Phobos until the gravity effect starts to turn to zero - apparently about 80km - and then seeing if I could drift into the L5 "valley", but it doesn't work and the orbit starts wobbling all over. This is with non-spherical off to simplify everything.

What I would really like to do is position my home-built station (parts shipped from Phobos) there (at L4 or 5), but I'm having real trouble finding it.

Any suggestions?

 

[pattersoncr]

I figured out a way to get to the Earth-moon L4 & L5 points using IMFD offset targeting. I haven't tried it with Mars-Phobos but I don't know why it wouldn't work.

Search M6 for Lagrange point (L4 or L5) with IMFD or see the link for details.

 

[sputnik]

L4 and L5 aren't where Phobos' gravitational effect approaches zero. L4 and L5 are the Trojan points; they are always in the same orbit (as Phobos, in this case), but 60 degrees ahead or behind.

Given the relatively VERY small mass of Phobos and Deimos, I doubt there's any measurable effect on orbit stability (read: an orbit almost anywhere will be stable enough). If anything, I'd expect Deimos' to be more stable, as it's further out and Phobos is beneath it, rather than above it.

 

[Quick_Nick]

L4 and L5 aren't where Phobos' gravitational effect approaches zero. L4 and L5 are the Trojan points; they are always in the same orbit (as Phobos, in this case), but 60 degrees ahead or behind.

That's what I was thinking. But also, as I think you were saying, you could put yourself in the same orbit not too far away and not be affected by Phobos. It's not exactly an L-point, but in this case it's probably better as you don't have to go so far.
I wouldn't post this if I were sure what you meant. I'm just not sure if in the second part of your post you were talking about what I'm saying or if you were talking about going to the L-points anyways.

 

[Belisarius]

Thanks, I also had the idea of using IMFD Map to show me the SOI boundary.

I'm going to check patterson's suggestion now.

Happy flights

 

[tony]

Use this Calculator to find the L points:
http://orbitsimulator.com/formulas/LagrangePointFinder.html

 

[sputnik]

Becking off outside of Phobos' SOI will certainly be good enough for Orbiter purposes, but it's not truly stable over the very long-term; only the L4 and L5 points will give you that.