Multiple comm sat sets?

[Cabadam]

I've been experimenting with a sandbox game with the communication requirements all enabled (no probe control, only KSC, etc).  When reading up on the topic, I found:
https://wiki.kerbalspaceprogram.com/wiki/Tutorial:Setting_up_a_CommNet_system#Constellations

This suggests that multiple rings of communication satellites are needed.  Is this accurate?

If 6 relays work at 4,000km, why would I need 24 at 50,000km (also, I'm assuming the article lists incorrect units - it says 50,000,000km)?
And couldn't I just put the more powerful RA-100 relays as the 6 innermost ones and JUST have that?

I'm wondering if there is a mechanic / need I am missing here.

Thanks!

[HvP]

Hello @Cabadam and welcome to the KSP forums!

I can see how those numbers wouldn't seem to make sense. The confusion lies in the use of the term "Kerbol" in the section you were reading. "Kerbol" is the unofficial term for the central Sun in the game. Thus, the six rings of satellites in orbits out to 50,000,000km really does mean to put them in orbit around the game's sun at those distances, not the planet of Kerbin. This way you get deep space communication coverage across the entire solar system, including planets such as Moho and Eeloo.

For the Kerbin system itself a much more modest set of satellites is recommended.

Quote

Kerbin system

Kerbin

Equatorial triangle orbit above 600km. Polar triangle orbit above 600km. A second equatorial triangle orbit at around 60,000km. Use RA-2 relays.

Mun

Polar triangle orbit above 200km. Use RA-2 relays.

Minmus

Polar triangle orbit above 60km. Use RA-2 relays

 

Edited January 14, 2020 by HvP

[AHHans]

8 hours ago, Cabadam said:

This suggests that multiple rings of communication satellites are needed.  Is this accurate?

Well, I think the important part of this constellation is at the very bottom of the page: it allows you connections to 2G antennas (DTS-M1 / RA-2) nearly everywhere in the solar system. If you are willing to put larger antennas onto your deep space probes, then you can make do with a lot less.

My strategy for commsats is the following (I play without the extra ground-stations):

• In the early game when I have only the HG-5 available:
  • I put a few satellites with 4 HG-5 antennas willy-nilly into orbits around Kerbin. (Usually I just fulfill a couple of "place satellite here" contracts.)
  • I make sure that one of them is in polar orbit around Kerbin
  • This is also usually the time when I place my "arrays" around the Mun and Minmus: one (4 x HG-5) satellite in a polar orbit and two on opposite sides in an equatorial-ish orbit each. (I eyeball the "opposite side" part of the orbits and then make sure that the period of the orbits is as identical as I can make it.)
• When I unlock the RA-2 I use that for any new satellite, but I don't do anything special, same for the RA-15. Natural evolution (just putting relay antennas on everything that stays in space longer) fleshes out my network in the Kerbin system.
• When I unlock the sentinel telescope I usually also have the RA-15 available, so I put two sentinels in orbit to monitor Kerbin (two in well spaced orbits between Eve and Kerbin are(were) enough to fulfill all the "find asteroids" contracts (before they became broken: bug #24282)) with four RA-15 each. These are my main relays for the inner system up to Duna.
• When I unlock the RA-100 I place my main relay: three satellites in a triangle in stationary orbit around Kerbin with four RA-100 each. Four RA-100 have about the same power as a fully upgraded tracking station, so these guarantee line-of-sight in all directions from Kerbin even without the additional ground-stations. It also gives 100% coverage for the antennas in probe-cores in LKO.
• Whenever I explore a new planet I usually start with uncrewed probes that will do the first exploration (= gather all available science from space) and then remain in orbit as relays. So the M700 Survey Scanner probes become the relays on polar orbits and other probes go on equatorial-ish orbits. I also usually put a space-station in orbit, which - of course - also has relay antennas. The antennas I choose depend on the planet: RA-15 for everything up to Duna and RA-100 for Dres and beyond. (The RA-15 doesn't use much more space than the RA-2, so I don't use the RA-2 often after unlocking the RA-15.)
• For Jool I plan to re-use the scanner probe, so I sent a carrier with one RA-100 satellite and 12 RA-15 satellites to Jool to cover the moons. (In addition to the station, asteroid-tug, and probes that are already or will be in or around the Joolian system.)

This doesn't give me guaranteed 100% coverage everywhere, but with the appropriate antenna I will have a connection as long as nothing blocks the line-of-sight to Kerbin (or the three long-range relays there), which is good enough for me. Most (all?) no connection incidents I had were either before I set up the initial HG-5 array or when I forgot to add an appropriate  antenna (e.g. forgetting to add any antenna at all for LKO before the long-range relays are up).

[Shameless Self-Promotion] And because every self-respecting space program needs a powerful radio-telescope, I also have a Very Kerbal Array in orbit around Kerbin. [/Shameless Self-Promotion]

Edited January 14, 2020 by AHHans

[DeadJohn]

In practical terms, KSP satellite links will pass through atmosphere and even a little bit of ground. Opposing pairs of satellites can generally work as effectively as triangular constellations especially if you use RA-100.

For Kerbin, with only KSC as a ground station, I would use a triangular constellation high above the equator, so at least one is always linked to KSC, and all 3 are linked to each other. Then add an elliptical polar pair, one extremely high above the north pole and another extremely high above the south pole, to help bounce signals over moons and planets.

After Kerbin is covered, I slowly add polar pairs: Kerbin, Minmus, Duna, Ike, etc. I don't worry about synchronizing polar pairs; each satellite spends days dwelling above its assigned pole and only minutes zipping around the wrong side at periapsis. It's not mathematically perfect but works well enough.

One or both members of a polar pair include scanners from the SCANsat mod to fully map the surface.

Landing a probe is when a loss of communication is most likely to be fatal. I check comm network positions just before landing a probe on the far side (relative to Kerbin) to confirm I'll have a good link throughout the landing process. I only need to check early in the game; late game there are so many relays in line of sight at any given time that it's "impossible" to get a blackout (unless I forget an antenna!).

 

[Cabadam]

21 hours ago, HvP said:

Hello @Cabadam and welcome to the KSP forums!

I can see how those numbers wouldn't seem to make sense. The confusion lies in the use of the term "Kerbol" in the section you were reading. "Kerbol" is the unofficial term for the central Sun in the game. Thus, the six rings of satellites in orbits out to 50,000,000km really does mean to put them in orbit around the game's sun at those distances, not the planet of Kerbin. This way you get deep space communication coverage across the entire solar system, including planets such as Moho and Eeloo.

For the Kerbin system itself a much more modest set of satellites is recommended.

 

Thanks for the welcome, have had the game for a couple months now, having a blast.

On topic - oh wow.  I'm an idiot.  That was exactly it.  Thinking about it relative to the sun and everything falls into place like it should.  Doh.  You know, I was really hoping it wouldn't be something that uh... simple.

[Cabadam]

13 hours ago, AHHans said:

Well, I think the important part of this constellation is at the very bottom of the page: it allows you connections to 2G antennas (DTS-M1 / RA-2) nearly everywhere in the solar system. If you are willing to put larger antennas onto your deep space probes, then you can make do with a lot less.

My strategy for commsats is the following (I play without the extra ground-stations):

• In the early game when I have only the HG-5 available:
  • I put a few satellites with 4 HG-5 antennas willy-nilly into orbits around Kerbin. (Usually I just fulfill a couple of "place satellite here" contracts.)
  • I make sure that one of them is in polar orbit around Kerbin
  • This is also usually the time when I place my "arrays" around the Mun and Minmus: one (4 x HG-5) satellite in a polar orbit and two on opposite sides in an equatorial-ish orbit each. (I eyeball the "opposite side" part of the orbits and then make sure that the period of the orbits is as identical as I can make it.)
• When I unlock the RA-2 I use that for any new satellite, but I don't do anything special, same for the RA-15. Natural evolution (just putting relay antennas on everything that stays in space longer) fleshes out my network in the Kerbin system.
• When I unlock the sentinel telescope I usually also have the RA-15 available, so I put two sentinels in orbit to monitor Kerbin (two in well spaced orbits between Eve and Kerbin are(were) enough to fulfill all the "find asteroids" contracts (before they became broken: bug #24282)) with four RA-15 each. These are my main relays for the inner system up to Duna.
• When I unlock the RA-100 I place my main relay: three satellites in a triangle in stationary orbit around Kerbin with four RA-100 each. Four RA-100 have about the same power as a fully upgraded tracking station, so these guarantee line-of-sight in all directions from Kerbin even without the additional ground-stations. It also gives 100% coverage for the antennas in probe-cores in LKO.
• Whenever I explore a new planet I usually start with uncrewed probes that will do the first exploration (= gather all available science from space) and then remain in orbit as relays. So the M700 Survey Scanner probes become the relays on polar orbits and other probes go on equatorial-ish orbits. I also usually put a space-station in orbit, which - of course - also has relay antennas. The antennas I choose depend on the planet: RA-15 for everything up to Duna and RA-100 for Dres and beyond. (The RA-15 doesn't use much more space than the RA-2, so I don't use the RA-2 often after unlocking the RA-15.)
• For Jool I plan to re-use the scanner probe, so I sent a carrier with one RA-100 satellite and 12 RA-15 satellites to Jool to cover the moons. (In addition to the station, asteroid-tug, and probes that are already or will be in or around the Joolian system.)

This doesn't give me guaranteed 100% coverage everywhere, but with the appropriate antenna I will have a connection as long as nothing blocks the line-of-sight to Kerbin (or the three long-range relays there), which is good enough for me. Most (all?) no connection incidents I had were either before I set up the initial HG-5 array or when I forgot to add an appropriate  antenna (e.g. forgetting to add any antenna at all for LKO before the long-range relays are up).

[Shameless Self-Promotion] And because every self-respecting space program needs a powerful radio-telescope, I also have a Very Kerbal Array in orbit around Kerbin. [/Shameless Self-Promotion]

Thanks for the write-up.  I at some point want to get back to a Career mode, or at least Science mode game to do like you are describing and really have to "build up" to things.  I tried those modes at first but I struggled to keep track of what science I had gathered and what I still needed to.  The end result was that I kind of got stuck, having essentially done all I can with current technology, but not knowing what I should do in order to get more science.  When I get back to those modes, I'll keep your info handy as I advance through things.

[Cabadam]

8 hours ago, DeadJohn said:

Landing a probe is when a loss of communication is most likely to be fatal. I check comm network positions just before landing a probe on the far side (relative to Kerbin) to confirm I'll have a good link throughout the landing process.

Heh, yeah I've been bit by this more than a few times.  That's one of the things I like about this mode.  Launch an unmanned probe, have everything planned out to a T... and all of a sudden I can't figure out why I lost control the craft.  Oops.

Edited January 15, 2020 by Cabadam

[AHHans]

6 hours ago, Cabadam said:

Thanks for the write-up.

You're welcome.

Some more ore less off-topic comments:

6 hours ago, Cabadam said:

The end result was that I kind of got stuck, having essentially done all I can with current technology, but not knowing what I should do in order to get more science.  When I get back to those modes, I'll keep your info handy as I advance through things.

Well, you don't need much of the tech tree to go interplanetary, and I also enjoy the challenge to get something done with limited resources. But everybody plays KSP differently. And if there's one thing that I hope you "take home" from my write-up then it's to not worry too much about getting the relay network right.

15 hours ago, DeadJohn said:

In practical terms, KSP satellite links will pass through atmosphere and even a little bit of ground. Opposing pairs of satellites can generally work as effectively as triangular constellations especially if you use RA-100.

There are two sliders in the difficulty section that define a modifier to the effective size of bodies with and without an atmosphere. And the default for them changes with difficulty setting, for easier difficulties the bodies are effectively smaller but on hard they have their actual size. (And btw. bending of radio waves around hard objects (diffraction) and in atmosphere (refraction) is a real thing, but diffraction around planets is insignificant for communication with satellites or space probes.)

15 hours ago, DeadJohn said:

Landing a probe is when a loss of communication is most likely to be fatal.

If you are playing without additional ground stations, then there is also the late launch problem: when you did a nice, flat, efficient gravity turn, are coasting to your circularization burn, and notice that you loose control because you lost line-of-sight to the KSC, don't have a relay that you can reach with the tiny antenna in the probe core, and forgot to unfold your main antenna. Luckily no Kerbals were harmed figuring this out.

[HvP]

Well, @Cabadam the name of the sun as Kerbol isn't officially in the game, so there's no reason know unless you've already been clued in by the community. And now you have!

Keep in mind that there's no one right way to play. Even with a comm-sat network people have all sorts of strategies, and I'm sure you'll find one that works for you.

Glad to hear that you've been having fun with the game. Good luck!

[Cabadam]

20 hours ago, AHHans said:

Well, you don't need much of the tech tree to go interplanetary, and I also enjoy the challenge to get something done with limited resources

Hah, well, at my skill level I do   Apparently I need more practice with early-ish rockets.  Playing sandbox probably isn't helping that much.  Although, for me, I mean it's more about "wait, do I need to go scan this? What do I scan next?"  I know there's kind of an in-game log of what you've done, but I haven't found it that easy to use.  That's what I really meant by not knowing how to get more science.  But that is probably a whole different post from this one...

Edited January 16, 2020 by Cabadam

[AHHans]

3 hours ago, Cabadam said:

Apparently I need more practice with early-ish rockets. 

Only if you want to. KSP really is a game where you set your own goals. So there's as many ways to play it as there are people playing it.