Lagrange Points - how to reach

[ruiluth]

First off: I know that KSP does not model Lagrange points. That is not my question.

What I want to do is put communication satellites in the same orbit as the various planets, so that I can have reliable coverage of both sides of the planet from opposite sides of the sun. Question is, how to get there. For Kerbin I figured out I could just eject them, one prograde and one retrograde, and tune their orbital periods to 5/6 and 7/6 of a year and then circularize at the correct apsis to be back in kerbin's orbit. For Duna and Eve I guess I can do the same thing, slingshot around them and eject prograde and retrograde and get into resonant orbits, but is that really the best way? How much dV should I pack? I have two potential vehicles, one with 6 km/s and one with 8.3 km/s, and I'd like to use the cheaper one but I can spare the funds if I need the bigger one. Has anyone ever done this before? Can KSPTOT be used to calculate this? If so how? Does MechJeb have any useful maneuver planners for this?

EDIT: Come to think of it, the contracts for Duna and Eve are both generous enough that I could just launch the big ones and use that trajectory... I'll probably end up doing that, but I'm curious to see how others would do this.

EDIT 2: For the Moho network I would like to find a more optimized trajectory.

Edited August 7, 2016 by ruiluth

[Reactordrone]

For other planets I'd probably do a Hohmann transfer just before, or just after the optimum to arrive just outside the planet's sphere of influence and then circularize to match the planet's orbit around the Sun. For planets with more eccentric orbits like Moho you might want to time it so that you arrive near apoapsis of periapsis to avoid large radial burns.

[LN400]

Not sure if I understand the question but if you want coverage everywhere all the time, couldn't you just launch 2 long range comm satelites  both with antennas for base and any planet you want to cover? Have them something like 120* apart in an orbit around Kerbol and at an altitude so that Moho never gets in the shadow, alternatively 3 sats 120* apart to make sure Moho always gets coverage? Of course, you will stil need local networks for each planet but to link them all, you would only need 3 long range ones around Kerbol. Any planet getting in between them would have local networks to relay the signal anyway.

If I'm way off target, feel free to disregard.

[ruiluth]

28 minutes ago, Reactordrone said:

For other planets I'd probably do a Hohmann transfer just before, or just after the optimum to arrive just outside the planet's sphere of influence and then circularize to match the planet's orbit around the Sun. For planets with more eccentric orbits like Moho you might want to time it so that you arrive near apoapsis of periapsis to avoid large radial burns.

Is there any way to calculate the precise angles and times for burns? Do you know if this would be more efficient?

 

25 minutes ago, LN400 said:

Not sure if I understand the question but if you want coverage everywhere all the time, couldn't you just launch 2 long range comm satelites  both with antennas for base and any planet you want to cover? Have them something like 120* apart in an orbit around Kerbol and at an altitude so that Moho never gets in the shadow, alternatively 3 sats 120* apart to make sure Moho always gets coverage? Of course, you will still need local networks for each planet but to link them all, you would only need 3 long range ones around Kerbol. Any planet getting in between them would have local networks to relay the signal anyway.

If I'm way off target, feel free to disregard.

That's probably accurate... I'll have to look into that and do some calculations. Polar Kolniya orbits might work too as long range relays. Maybe my original plan was a bit inefficient...

[cubinator]

On 8/7/2016 at 6:08 PM, ruiluth said:

Is there any way to calculate the precise angles and times for burns?

1. Find out what ejection angle is needed for a Hohmann transfer to the desired planet
2. Add/subtract how far away (in degrees) you want the comms link from the planet
3. Perform your ejection burn at the angle from step 2 relative to the target planet.

Example: Two sats at +120* and -120* from Duna

1. A Hohmann transfer from Kerbin to Duna has a phase angle of 44*.
2. 44 - 120 = -76, 44 + 120 = 164
3. The sats should be ejected when Duna is at -76* and +164* relative to Kerbin, then perform circularization burns at apoapsis.