Orbital characteristics

[lugge]

I set up two relay sats according to this nice tutorial:

Both are in high eliptical polar orbit around Kerbin. Idea is, when one sat is at its AP, the other one is at its PE.

However, if my orbits are not fully polar (thus, have a 90° inclination or if the orbital period does not match, this will not work as intended.
One sat will go faster, they will go out of sync and eventually they will be both at their PE at the same time.

How do I get a readout about my inclination and orbital period?

This also bothered me a lot when doing interplanetary missions or to Minmus.
I never know if I hit a equatorial orbit.

Except on Kerbin, where I can use the Mun's orbit as a reference.
 

[Geonovast]

Not much you can do without installing a mod.

KER will tell you everything you need.

[lugge]

33 minutes ago, Geonovast said:

Not much you can do without installing a mod.

KER will tell you everything you need.

Is this also true for relay sats?

I use KER, but only for craft assembly (dv readout).
Normally, I get no orbital readouts. Does this require an engineer?

[Geonovast]

7 minutes ago, lugge said:

Is this also true for relay sats?

I use KER, but only for craft assembly (dv readout).
Normally, I get no orbital readouts. Does this require an engineer?

If you're playing career, maybe?  I only play sandbox, so I don't even need the KER modules for the readouts.

You may simply need to enable the orbital readout display box and edit it to have the modules you want.

[Spricigo]

The easiest solution in stock is redundancy.  with enough relays you almost ensure you will get a link to some relay.

 

in KER settings you can choose between Career (default) and Partless.  Career means that you need either a engineer or a KER part (sorry forget the name) to acess the readout in flight; Partless means that is always available.You may need to setup the displayed info too to get what you need. 

Same deviation in inclination (a few degrees) is not a big deal. Orbital period is the critical parameter to mitigate the relays drifting out of phase.

 

BTW: in stock you can find out the inclination by accessing KerbNet and observing the coordinates.

[Flavio hc16]

another way to have partless readouts in ker is having a tier 3 tracking station 

[swjr-swis]

9 hours ago, lugge said:

However, if my orbits are not fully polar (thus, have a 90° inclination or if the orbital period does not match, this will not work as intended.
One sat will go faster, they will go out of sync and eventually they will be both at their PE at the same time.

I know this is not exactly what you asked, but keep in mind that in highly eccentric orbits like these, it really doesn't matter much if the two sats gets out of sync with each other: the time they spend anywhere near the planet is so small it will have very little impact on your relay coverage.

Edited February 27, 2018 by swjr-swis
speeling hard

[Dark Lion]

On 2/27/2018 at 8:50 AM, lugge said:

I use KER, but only for craft assembly (dv readout).
Normally, I get no orbital readouts. Does this require an engineer?

Yes an engineer is required if you are in career mode, and said kerbal aboard must be rank 3 or higher. Alternatively, you can just fully upgrade your Tracking Station to gain unbridled access to all the lovely customizable pop-outs from Kerbal Engineer Redux, but without any need for kerbals involved. Launch any compatible craft to the pad and look over the KER interface very thoroughly, as you may want to use some of the miscellaneous options as well. There's even a scaler for the text, if your screen is getting too "busied." I recommend customizing your own stat windows per situation as is relevant to your playstyle. I have one for rovers and jets and Kerbin-bound spaceplanes, another for testing craft. I have one purely for orbital telemetry and another for craft telemetry... I might be getting redundant, but I don't even play without KER if I can help it.

Also: I know you didn't ask me, but if you used a 3-seed/triangle network with the same deltaV, you could seed and sync them to about where your average altitudes are. The more powerful your relays, the further out I'd encourage you to park them from one another... just mind the seed resonance and deployment timing, and your network will mind you. Totally black-out free. 

[Zhetaan]

On 2/27/2018 at 7:57 AM, lugge said:

However, if my orbits are not fully polar (thus, have a 90° inclination or if the orbital period does not match, this will not work as intended.
One sat will go faster, they will go out of sync and eventually they will be both at their PE at the same time.

There's no good reason why they have to be exactly polar; the orbital synchronisation is only dependent on orbital period, and orbital period is only dependent on semi-major axis.  In other words, so long as your apsides match, the satellites will remain in sync.  (You can match SMA without necessarily matching apsides--there's a range of solutions--but matching apsides will guarantee a matched SMA, and since KSP actually gives you a readout for that, it's easier to do.)

On 2/27/2018 at 7:57 AM, lugge said:

How do I get a readout about my inclination and orbital period?

You can get a latitude readout from Kerbnet.  It won't give you inclination directly, but the maximum latitude you see will be your inclination, and the point of zero latitude will be your node.  If you're close to equatorial, you can probably get away with only paying attention to the zero point; lightly thrust normal or antinormal as needed when you cross it.

For orbital period, you'll have to calculate, but it can be done with stock readouts.  Also, the apsides given in KSP are altitudes from the surface, not distances from the gravitational centre; you'll need to add the diameter of Kerbin to get the semi-major axis.  In KSP, you'll need to calculate it this way:

T = 2π * √ ( [ (Ap + Pe + r_body) / 2]³ / [G * M] )

Where:

T = orbital period,
(Ap + Pe + r_body) / 2 = semi-major axis (apoapsis plus periapsis plus body diameter, all divided by 2), and
G * M_body = gravitational parameter (different for every body, but constant for a given body:  universal gravitational constant (6.674 x 10^-11) times body mass)

I believe that both planetary radius and mass are given in the information window in either map mode or the tracking station.  It may be diameter; be certain to verify for yourself.

 

That being said, I will tell you that @Geschosskopf wrote an excellent tutorial and that the setup he recommends is absolutely my first choice when I need to have a minimum-fuel network for my far-flung probes, but for a more permanent no-blackout network, I prefer to do things a bit differently.  I keep the low-orbit equatorial satellite, but I circularise my high-orbit relays at the apoapsis with ninety degrees' difference in longitude of ascending node.  In other words, rather than have two orbits be co-planar, I set the orbits so that they 'cage' Kerbin; their orbital planes are both polar, but at right angles to one another.  (For lovely word pictures, if you were to look straight down at Kerbin's north pole from far away, these orbits would appear to be an X.)  I also set the satellites in those orbits so that when one is over a pole, the other is over the equator, and the polar satellite can always see the low-orbit satellite (so I want my 'low' orbit satellite to be quite a bit out of the atmosphere or off the ground; I don't want terrain or what-have-you to get in the way).  This completely eliminates blackouts and requires a lot less finesse, but it also requires a lot more fuel and careful timing.  It's only easy to do for Kerbin, but it gives top-notch coverage, which is what you really ought to have for Kerbin anyway.

My go-to Kerbin network doesn't work so well when sending a fleet of com relays to far-away planets because those com relays will generally enter the sphere of influence from the same direction; changes to the longitude of ascending node are thus very expensive.  On the other hand, it's trivial to adjust orbital inclination from just inside the sphere so that one satellite passes over the north pole, one over the south, and one over the equator.  After that, your main concern is closing the orbit when you reach periapsis; only the equatorial relay needs a substantial fuel budget to bring the apoapsis down to circularise.  Changing the timing to put the polar relays 180° out of phase is a matter of temporarily adjusting the apoapsis for one of the polar relays--still trivial and you get to use Oberth for extra fuel savings--so for initial communication at a new planet, it's an exceptionally slick system.

[Snark]

On 2/27/2018 at 4:57 AM, lugge said:

Both are in high eliptical polar orbit around Kerbin. Idea is, when one sat is at its AP, the other one is at its PE.

However, if my orbits are not fully polar (thus, have a 90° inclination or if the orbital period does not match, this will not work as intended.
One sat will go faster, they will go out of sync and eventually they will be both at their PE at the same time.

How do I get a readout about my inclination and orbital period?

Best way is to make it so that you don't have to.

First, the inclination isn't something you need to care about.  There is nothing in any setup where the exact inclination matters.  So just eyeball it and you're fine.

As for the period:  As folks have stated, you'd need a mod for that.  In stock, though, it's pretty simple, since you don't care about the actual period-- you only care about their period relative to each other.  So that's easy.  Two satellites will have the same period if Ap + Pe are equal.  So, just make that so.  Let's say you have satellite A and B, and you want to adjust them to have the same period.  Pick one of them to adjust-- say, A.  Let's suppose you plan to do the adjustment by modifying A's periapsis.  So, to work out what A's Pe should be:  add Ap + Pe for satellite B, then subtract A's Ap.  That number is the desired Pe for A.  Wait until A is at Ap, then do a small or burn to adjust the periapsis to exactly what you want.  There, done.  No calculations other than plus and minus on your calculator. 

But honestly?  Unless the challenge itself of setting up a synchronized satellite network is what you enjoy doing, my advice would be simply "don't bother":  specifically, don't get hung up on trying to guarantee 100% coverage.  It's much less effort to go with a "randomized" solution that gives 99%+ coverage, and honestly, does that little random under-1% window really matter, as far as gameplay is concerned?

Put up a few satellites in high orbits that are very inclined to each other, with periods that make no particular attempt to be synchronized, and you end up getting excellent coverage for very little effort.

It basically all boils down to what you're optimizing for, and what motivates you when you're playing KSP.