How-to: Position satellite *between* mun and kerbin

[sabrick]

I'm using the remoteTech mod and I'm trying to position a communication satellite in an orbit around Kerbin that keeps it between Kerbin and the Mun at all times. Is this possible? Any help would be appreciated!

[Xavven]

As you may know, the higher the orbit, the longer its orbital period. Mun will always complete a full sidereal orbit faster than Minmus, for example. Putting a satellite between Kerbin and Mun, therefore, will mean that the satellite will always become misaligned.

In real life it's possible to do as you describe, however, because of N-body physics. That is, the Moon's gravity counteracts Earth's, allowing a satellite to experience less spacetime curvature and orbit in synch with the Moon at a lower Earth orbit. This is called a Lagrangian Point, and in your case, specifically the L1 point. You can read more about it here: http://en.wikipedia.org/wiki/Lagrangian_point#L1

However, in KSP, N-body physics are not implemented and therefore Lagrangian Points don't exist in the game.

[HorusKol]

Option 1 - have the satellite follow the exact same orbit around Kerbin as Mun does, except outside of Mun's SoI.

Option 2 - have the satellite orbit Mun such that it's orbital period matches the time it takes for Mun to orbit Kerbin - you'd have to do the Maths on that one, though, and I'm not sure it's possible.

In either case, you won't get it perfect, but it should be close enough to work for a good while.

[KerikBalm]

Wouldn't it be easier to just use two satelites in high matching orbits (like keosynchronous) ?

[DrMonte]

Option 1 - have the satellite follow the exact same orbit around Kerbin as Mun does, except outside of Mun's SoI.

Option 2 - have the satellite orbit Mun such that it's orbital period matches the time it takes for Mun to orbit Kerbin - you'd have to do the Maths on that one, though, and I'm not sure it's possible.

In either case, you won't get it perfect, but it should be close enough to work for a good while.

Yep the first option is most likely and quite easy to do.

[Starman4308]

Option 2 - have the satellite orbit Mun such that it's orbital period matches the time it takes for Mun to orbit Kerbin - you'd have to do the Maths on that one, though, and I'm not sure it's possible.

Not possible in stock: a Mun-synchronous orbit is outside the Mun's SOI. I'm uncertain about RSS. There's a WIP mod to do N-body physics, but that might be a little much to download just for Lagrangian points.

[metaphor]

You can't put a satellite and keep it between the Mun and Kerbin. But you can do other things, like putting one to the side of the Mun along its orbit but just outside its SOI. If you give it the same orbital period as the Mun, it should stay in the same place with respect to both Kerbin and the Mun. You could put one to either side of the Mun to get almost global coverage of the Mun at all times.

[Starman4308]

You can't put a satellite and keep it between the Mun and Kerbin. But you can do other things, like putting one to the side of the Mun along its orbit but just outside its SOI. If you give it the same orbital period as the Mun, it should stay in the same place with respect to both Kerbin and the Mun. You could put one to either side of the Mun to get almost global coverage of the Mun at all times.

And to enable coverage over that blind spot, you could try using a satellite in a very eccentric polar orbit with apoapsis on the dark side of the moon: it will always have a relay to those two satellites, and will spend 95% of its time with line-of-sight to the blind spot.

[LethalDose]

And to enable coverage over that blind spot, you could try using a satellite in a very eccentric polar orbit with apoapsis on the dark side of the moon: it will always have a relay to those two satellites, and will spend 95% of its time with line-of-sight to the blind spot.

This doesn't work since the AP will be on the dark side half the time and the light side half the time (the argument of the AP of the orbit is fixed in reference to the galaxy, not Kerbin). You can use an eccentric orbit with the AP over the N pole, though, and it'll spend most of it's time above the Mun, and in visual range of Kerbin. THis is how I handle RT2 networks (I HATE maintaining constelations), and I need to make a video tutorial for it.

But if you have relays at the L5 and L4 points with DTS-M1 pointed at the Mun, they should cover satellites in orbit around the entire Mun's equator. There'll be a blind spot very low, but it should be below where you're orbiting.

[Yakky]

It is possible. Build a very tall tower on the Mun facing Kerbin and stick your satellite at the top. It will be between the Mun and Kerbin at all times.

Edited November 6, 2014 by Yakky

[AndrewBCrisp]

Admittedly I haven't used RemoteTech - only read the details about the mod - but if your goal is to maintain communication between spacecraft on/orbiting the Mun and Kerbin, why not a network of three or more satellites in KEO? You should be able to maintain communication links between the satellites and any assets around the Mun; as one satellite passes behind Kerbin, there will always be another to take up the slack. A couple of satellites in high Munar orbit could help with covering anything on the Mun's farside and link to your Kerbin-orbiting network.

[MarvinKitFox]

I'm using the remoteTech mod and I'm trying to position a communication satellite in an orbit around Kerbin that keeps it between Kerbin and the Mun at all times. Is this possible? Any help would be appreciated!

EASY

Build your comsat.

Fly to the Mun

LAND on the kerbin-facing side!

As Mun is tidally locked to Kerbin, that landing spot will ALWAYS face Kerbin.

Problem solved!