Station Keeping

[aquilux]

I'd like to request a mod that automates the process of maintaining a specific orbit while consuming a small amount of ∆V over time, requiring eventual refuel or replacement of the craft.

• It would take user inputs for the target period, apoapsis, and periapsis (pick two of the three), as well as desired accuracy.
  
• It would require the user to achieve the desired orbit within a certain margin on their own (Maybe it could generate a phantom target to facilitate setup).
  
• User could knock craft's orbit out of target range, requiring reacquisition before stationkeeping becomes active again.
  

In turn:

• It would consume ∆V over time based on accuracy setting & orbit (too high or low accuracy would consume more ∆V, as well as being too close to atmo or dipping into it)
  
• It would monitor the craft's orbit whenever unloaded.
  
• It would vary the orbit within the accuracy range set over time, with the net effect of keeping it within the target orbit.
  

This mod would be most useful when used with remote tech considering proper satellite constellations require active maintenance. And while people could keep switching through dozens of satellites to correct their position and period instead of time warping to their probe's arrival, I feel as though many find this overly tedious.

Edited January 28, 2015 by aquilux

[RainDreamer]

I am interested in such a mod to be made. Though I wonder how would it be implemented. I haven't seen a lot of mod dealing with stuff on rail and track them.

[hab136]

This would be possible.

Orbit Manipulator Series lowers your orbit when in the atmosphere (even on rails).

Instead you could just slightly lower your orbit even when above the atmosphere; and if you have fuel, take the fuel instead of lowering your orbit (then when you run out of fuel, the ship would just drop).

I'm not sure creating a problem and then automatically solving it is fun. The net effect would be that sats just have a limited lifespan.

[aquilux]

I'm not sure creating a problem and then automatically solving it is fun. The net effect would be that sats just have a limited lifespan.

The primary point of this mod is solving a problem most people don't notice unless they're playing with remote tech. That is that you can never get exactly perfect, and because of that you will never be able to keep a constellation of satellites in their proper position without frequent and tedious orbital corrections.

What I propose as the core functionality in this mod is to automate the repetitive task of performing orbital corrections and simulate the average effects of those course corrections (never quite perfect, consumes ∆V over time, keeps proper position) and have the cost of those effects be based off of a few realistic conditions (lower t/w is more precise, the more accurate you try to be the more often you're burning, the further off you get the more it costs to fix, orbits too close to the planet are harder to maintain).

Edited January 30, 2015 by aquilux

[RainDreamer]

Hmm...I think we can have something like, a mod that reads current orbit of craft, compare it with user specify target orbit, then calculate the difference in dV between current orbit and target and execute it. So it is like save file editing that we tend to do with Remote Tech satellites, but with dV cost to be less cheaty.

[aquilux]

Hmm...I think we can have something like, a mod that reads current orbit of craft, compare it with user specify target orbit, then calculate the difference in dV between current orbit and target and execute it. So it is like save file editing that we tend to do with Remote Tech satellites, but with dV cost to be less cheaty.

Exactly, I wanted a solution that required me to have the requisite skill to put the satellite in the orbit I want as accurately as I want it to be without it being unrealistically perfect and lasting indefinitely, while also being able to handle the satellite being off rails and having it be nudged around by miniscule physics forces, without me having to save-quit-edit save-reboot every time.

[rynak]

I too support the idea. The player already has to:

- have the skill to bring the sat into a very stable and accurate orbit

- do all the maneuvres to give sats the right angles

The above is what requires skill and is a challenge. The tiny correction burns over time instead are just boring repetitive micromanagement of the most pointless kind, resulting from:

- Inaccuracies in the game

- Lack of extremely low powered thrusters (even thrust 1 would already be way too much)

Deficiencies of the game shouldn't be the player's burden, and like i said, station keeping is just monotonic boring work, that requires patience and masochism, not skill. Automate it, except for those who like to suffer.

[aquilux]

Is there anyone willing to assist with this concept?

[Got_milk?]

I too like the sound of this, as a fan of remote-tech and building complex systems, the maintenance does become an issue, and I don't edit my saves as a rule (unless its bugfixing)

I can get on board, I am only just learning C# and how it interacts with Unity as it stands but I enjoy problem solving and hopefully can be of more use as my skills improve.

You could include a part like in Kerbal engineer that enables this function, and would you consider throwing some low power thrusters into the mod as well? That could be interesting as part of a package.

[lextacy]

The problem with this idea is the game has too many bugs and the rails system will do a good enough job screwing around with your orbits that will do just the same thing as a mod would do. Just my 2

[Overjay]

This would be possible.

Orbit Manipulator Series lowers your orbit when in the atmosphere (even on rails).

Does it work in 0.90?

[Van Disaster]

The problem with this idea is the game has too many bugs and the rails system will do a good enough job screwing around with your orbits that will do just the same thing as a mod would do. Just my 2

Actually I think you just want this mod to repeatedly do what hyperedit does and put the craft back into it's original orbit at the cost of some RCS or something, so whether the game has bugs or not involving on-rails orbits ( actually just precision issuesI think ) isn't really relevant. Basically has to work out the orbit - or actually the current point on the orbit - with more precision than the game does, which is fortunately not difficult.

In that case you can apply it to everything in orbit anyway and you've probably solved the original station keeping issue

[Cydonian Monk]

Well, the Timewarp Rotation Fix did some of this, namely station keeping and eating through RCS/Monoprop over time.

http://forum.kerbalspaceprogram.com/threads/67821-Timewarp-Rotation-Fix

Trouble is the new SAS system seems to have busted the method used for that, the plugin's not been updated for 0.90, and I've not had time to wrap my head around the new SAS to fix it myself. Might be a good place to start looking.

[aquilux]

Actually I think you just want this mod to repeatedly do what hyperedit does and put the craft back into it's original orbit at the cost of some RCS or something, so whether the game has bugs or not involving on-rails orbits ( actually just precision issuesI think ) isn't really relevant. Basically has to work out the orbit - or actually the current point on the orbit - with more precision than the game does, which is fortunately not difficult.

In that case you can apply it to everything in orbit anyway and you've probably solved the original station keeping issue

Kind of but not really. It'd probably have to work in the same way hyper edit works, but I don't want it to be any more accurate than the game's on-rails calculations are, those are good enough. The issue is the floating point errors when physics is applied makes it impossible to get a perfect orbit, but I don't even want to get rid of that.

My ultimate goal is to keep my satellite constellation from drifting out of position while:

1. Not using something cheaty like hyper edit.
   
2. Limiting it's performance to that of the user's ability.
   
3. Not making it an unlimited, global solution.
   

As I described in my first post, this would be accomplished by:

1. Requiring the player to achieve the desired orbit within a maximum error range.
   
2. Causing it's duration of effect to be dependent on the player's ability for accuracy.
   
3. Limiting it's effect to craft that have achieved an assigned target orbit.
   

In addition to these goals a few more I include for realism and usability, these are:

1. Effect duration dependent on available ∆V resources (LFO, RCS, Xenon, ect...) and these resources are depleted over time.
   
2. Accuracy additionally dependent on force magnitude (the smaller the thrust to weight, the more accurately you can burn) and can have an effect on how much the satellite needs to correct itself, accelerating it's resource consumption.
   
3. When a satellite runs out of it's resources it can no longer maintain its orbit as it has and begins to drift (accomplished by applying a small bump to it's orbit that is proportionate to how much it was needing to correct itself), requiring a resupply if you don't want it becoming trash.
   
4. Ignore systems & resources that have been deactivated/locked for the purpose of keeping a reserve for final disposal and diminishing it's TWR to make it's motions more accurate.
   

Edited February 22, 2015 by aquilux
Edit for readability.

[aquilux]

Well, the Timewarp Rotation Fix did some of this, namely station keeping and eating through RCS/Monoprop over time.

http://forum.kerbalspaceprogram.com/threads/67821-Timewarp-Rotation-Fix

Trouble is the new SAS system seems to have busted the method used for that, the plugin's not been updated for 0.90, and I've not had time to wrap my head around the new SAS to fix it myself. Might be a good place to start looking.

While this mod demonstrates resource consumption, this is not what I am proposing for the on-rails behavior. I do not propose that some aspect of the craft's off rails physics be stored, only that it's final effects are emulated in a simple and reliable manner. And while the timewarp rotation fix looks rather promising in it's scope, it does not appear to have any effect on the craft's orbit, nor does it appear to cover any other points in my request other than the limited resource consumption.

[aquilux]

Is there no interest in developing a mod such as is outlined here?

[Glyph]

I would love this also.

[John Nowak]

This does sound like a useful mod, and there might be some overlap with something I was wishing for today.

I was maneuvering a ship near a space station, got the relative speed down to 0.1 m/sec, and by the time an engineer was able to spacewalk out to it with a pipe, it had drifted completely out of position. 

Some sort of "Maintain present position relative to vessel" mod might solve both these problems, especially if it could be set to use monoprop so you still have to keep them in monoprop. 

[wasml]

This sounds interesting - There are a bunch of things that would degrade an orbit a) atmosphere doesn't stop - just slowly tappers off. b) planets are lumpy - density variations would disrupt orbits. c) satellites (ex: Mun, Minmus) would perturb orbits. d) solar wind. e) radiation. (saw something where spinning asteroids could raise/lower their orbit depending on which way they rotated - IR radiation pushing in one direction or another). f) magnetic fields. (there was a proposal to deploy a long wire and electrify it with solar panels for station keeping in earths magnetic field).

I don't know but would suspect the real life disruptions would often be more than what we get due to rounding errors. If you could find the magnitude of the assorted disruptions for a given orbit ( I have no idea what the magnitude of these would be ) and use that to apply a periodic random bump that your station keeping would need to counter....

[Charlie the Kerbal]

I am not sure how fun Remote Tech will be without station keeping. Then it will simply be setting up 5-6 com sats and the job will be done. I think whether it is floating point issues or something else, small drifts in the orbit helping to simulate more of a real time situation. I knew people who worked at real Com Sat tracking stations, and I remember it was one of their routine tasks to make small adjustments to orbit time to time. This was a few years ago, maybe satellites are now doing adjustments themselves, although I doubt it as a mis-calculation can easily deplete the satellite of fuel and turning it into a space junk. For me it is similar to an airplane is always taking off and landing manually although sophisticated autopilot technology is available, it is just something that requires human intervention.

In a real life scenario, there are so many factors impacting orbital drift, from the Earth no being perfectly spherical, to tidal forces, to solar winds.

In my KSP experience, I use four 24-77 Twitch engines on my Com Sats, for finer adjustments the two are shutdown (opposite diagonals), and active ones are set to 5.5% trust limit. With this setup I never managed to get an orbital period of 6:00:00.000, it is always a bit higher or lower. But at this precision, it takes weeks for a sat to drift. So it is more likely a bi-weekly maintenance tasks to go through all 5 com sats to see how they are doing. A simple approach I take is, if I found a sats orbital period is slightly over 6 hours, which means it was going slightly slower than required over the last two weeks, I make a very small burn to make it slightly less than 6 hours, so over the next two weeks it compensates.

Stationkeeping is one of the routine jobs I do, in addition to making sure orbital space stations have enough fuel for ships docking, kerbals on orbit or on other planets are rotated occasionally or they are fed and watered well  You don't leave your kerbals on orbit for 5 years, do you ?

[Stone Blue]

@Charlie the Kerbal I can see your point, where station keeping may add to the realism, but when you have more than just a simple network, and get into having dozens of relay sats, it DOES get kind of ridiculous... I sometimes use KerbalGPS, and I can see it being useful for those netwroks as well... Especially when my Kerbin SOI RT network alone is 17 sats, with either 12, 16, or 24 sats in a GPS constellation, I think you can see how regular station keeping could become ridiculous in a single-player game...

I didnt realise how old this thread was when I first replied...
Just an FYI for future readers, the Timewarp Rotation Fix that Cydonian Monk linked above, was replaced/forked into:

Persistent Rotation

 

Edited February 7, 2016 by Stone Blue

[Gnoyze]

I thought there was a mod for this, but I can't seem to find it. Though I do remember it had a part called "Station keeper OMS" or something like that. If I can seem to find this mod I'll post a link here.

Edit: Found it! Here it is:

 

Edited March 5, 2016 by Gnoyze
FOUND IT!

[Matt77]

I like the sound of this mod, mainly for maintaining Remotetech networks.

I've had a related idea in mind, when constructing large missions my construction fleets drift away from each other over time (even a few minutes while manoeuvring other vessels).  I was thinking about a "station-keeping" SAS mode which would hold zero velocity relative to the target, but the proposed mod here might be more appropriate.