Synchronizing Satellite Orbits

[glibber]

Hello fellow Kerbals!

I'm currently trying to set up satellites for my communication network. I'm aiming for triangular orbits (3 satellites equally spaced on a single orbit).
To avoid getting messed up distances, the orbits of all three satellites have to be almost exactly the same obviously. That works just fine until I decouple the satellite from my rocket, which creates an additional push, messing up the orbit.

I have tried to time the decoupling correctly, e.g. decoupling prograde at the apoapsis, doesn't really seem to work though. Is there any way to achieve identical orbits without having the ion engine unlocked? Or is there any way to determine the amount of Δv the decoupling is going to produce?

Side note: Not using any mods

Thank you all.

[Aranador]

Well, so, the obvious answer, but, give the satellites a probe core, a small amount of mono-propellant, and some RCS thrust units.

[[IFC]Mjollnir]

How do you decouple them? Docking port? Decoupler? Stack seperator? Different push from these... also, but not sure about this being stock, you should be able to define how much force is used when decoupling...
Next thing would be to add a small fuel tank, the smallest engine you have a (and, optional, a small reaction wheel) tank to your satelite, even monopropellant should do the trick.. it doesn't need much to push the satelite into the correct orbit...

Edit:

After rereading OP's question, it sounds like you're releasing the satelites while being on the orbit they need to be on?
That might also be your problem, if it is like that, since it's hard to equally space out the satelites that way...
You would have to be on a orbit that is 2/3 of the orbit time you want the satelites to be/have to achive a geokerbol orbit and than release them everytime you pass apoapsis...

Good thing is, there are many tutorial videos out there about how to do that, a really good one (although being old) is as usual one from Scott:
https://www.youtube.com/watch?v=Z3FHOQFVV0k

Edit#2: if you follow that tutorial, you satelites have to have some sort of propulsion system, otherwise it doesn't work...

[glibber]

That's what I thought...

I just wondered if it was possible to set up satellites that don't carry around any engines/fuel. But apparently there's no way to avoid that.

Regarding your questions: I usually launched three separate rockets, aligned their orbits and set up the distances between them. Afterwards, I decoupled the satellites using decouplers, which destroyed my orbits. I believe it would work with a docking port, since they shouldn't create any push, but carrying around a docking port isn't really better than having a small engine I guess.

Launching all three satellites on a single rocket would make spacing easier for sure, thanks for that idea. I'd need to have a mod to display the orbital period, or is there any way to display it in the vanilla game?

[[IFC]Mjollnir]

Mod is way easier, I would recommend using Kerbal engineer redux, ( https://forum.kerbalspaceprogram.com/index.php?/topic/17833-130-kerbal-engineer-redux-1130-2017-05-28/&tab=comments#comment-245084 ) that gives you the small info windows to the left and right of your altimeter (as you can see them in the vid on the page I linked) but also shows you more information directly onscreen, without having to hop out to "map-mode"... the window you can see on the left in Scott's video I linked is also part of the mod, and of course can be switched off...

Edit:
For mod installing using CKAN is recommended....

Edit#2: and of course is launching satelites using just one rocket way more effective than using three... it also costs less ;-)

[MechBFP]

Your orbits really don’t need to be perfect. If they are really far out, like 1 million+ kilometres above the surface, a tiny difference will take decades of in game time to become a problem.

[glibber]

Well at Kerbin for example, I'm at 700-800 km, so it should be more or less close to identical orbits

[[IFC]Mjollnir]

700 to 800 km? Well, that would mean you're not aiming for Keostationary orbits but Keosyncronous orbits, which is still fine for communication/relay satelites...

[glibber]

Exactly, not aiming for geostationary, just building my CommNet

[alienfx]

For decoupelrs, you can reduce the thrust force when assembling a rocket.

For the low orbit of Kerbin (less than 900 km), I use 4 satellites, which gives greater coverage in latitudes.
You need to be sure that the repeater will have enough power for the selected height.

I try to launch all communication satellites with one rocket, then their orbital planes will be the same at once.
The entire group is output to LEO (Low Equatorial Orbit), and then each satellite itself goes into the calculated orbit with its own course.

I use "Kerbal Engineer Redux" to get accurate orbit data, and "MechJeb2 - Maneuver Planner" to accurately perform a given maneuver.