Orbits, and why they seem to randomly change

[ibanix]

So as a user of RemoteTech, I often run into this issue: I put a comsat into Keosynchronous orbit (~2868km). I use some RCS to get the timing as close as possible to perfect.

Then the orbit changes, without any delta V change on the craft! The periapsis and apoapsis will slowly increase or decrease, usually by a few meters to a dozen meters per second. The effect is even more clear when one is watching the orbital period, as it will go up or down from the desired value without any changes at all.

What's going on here?

[FancyMouse]

Have seen that occasionally. My take - I often make semi-major axis near a whole number. Say my Duna network wants a 1.5Mm, then I'll first make it close to 1.5Mm, now it flucuates at 1.5Mm +- 10m, and it may or may not gradually increase/decrease as you say. Doesn't matter. I just keep pressing escape to pause the game (while letting KER show my semi-major axis). When I saw a whole 1.5Mm, I go to space station and never touch that satellite again. This can give me 1.5Mm+-0.5m semi-major axis on rail, and I don't need to worry about out-of-sync ever.

[Taki117]

The main reason for this is physics inaccuracies. As your orbit vets closer and closer to circular floating point errors add up and cause your AP and PE to jump around, often times by up to as much as several hundred meters. This is normal and you don't need to worry about your satellite getting out of synch. AP and PE values for a synchronous orbit matter much less than orbital period. As long as your orbital period is 6hrs your satellite shouldnt drift out of position.

[hendrack]

I stopped bothering with keosynchronous orbits and made a network with many kolniya orbits.

[stibbons]

I also use a mix of dedicated Molniya orbits and supplementing contract satellites with remotetech relay capabilities for my Kerbin system relays.

But yeah, achieving circular orbits is a pretty big pain. For synchronous stuff you're better off going with a slight eccentricity. As long as the orbital period is bang on six hours, you'll have a satellite that "wobbles" east-west from a surface perspective, but otherwise stays in the same place.

[ibanix]

Hendrack: What mod is it that is showing you the details of the ship at the bottom of the screen?

[hendrack]

Historian

[Snark]

I love RemoteTech and use it all the time. For the first few games I played with it, I was conscientious about making carefully-tuned constellations of keosynchronous satellites.

That can still be fun, if you take that as a challenge in itself. However, it's not really necessary, and eventually I just stopped bothering. The fact is, if you're not hung up on "build a comm network with the absolute smallest possible number of satellites", and don't worry about "100% guaranteed coverage at all times forever, it's okay if it's only 99%", then it's simple. Just put up a bunch of little relay satellites and it takes minimal time, fuss, and bother.

A minimal satellite with a 2500km omni antenna (or, slightly later in the tech tree, a 5000km omni) and a couple of solar panels is dirt cheap to launch and quick to put up. Stick a half-dozen or so in equatorial orbits at an altitude of 1000km or thereabouts, plus a couple in polar orbits (perpendicular planes) up higher around 2000km, and you'll pretty much always have connectivity to KSC from anywhere in near-Kerbin space.

When you're ready to explore Mun and Minmus, just add a satellite or two with a DTS-M1 in a high polar orbit, and you're good to go. When you venture out into the solar system, add a relay satellite with the bigger dish antennas and put it in a high polar orbit.

All of this requires minimal planning, very little cash, not much of your time, and no fidgeting with fine-tuning.