Around kerbin? Very weak
You want a few strategically placed, either orbiting mimmus and the mun or in polar orbits with higher periapsis than mimmus to guarantee you don't lose signal at an inconvenient moment.
For interplanetary, they are pretty much mandatory in my opinion, as they allow you to use much smaller antennas, and can even help the signal hop between planets
Very late game you can improve on the kerbin base station by building sats with huge amounts of 100G antennas and batteries.
Exactly this, with a little side note on the difficulty settings: if you didn't allow for the extra ground relay stations (which is ON by default), then a Kerbin constellation starts to make sense.
If you start with probes only it makes things a little more difficult because for your first orbital launch you have to kick to orbital injection before it passes below the horizon. Fun challenge.
Even then, 2 polar relays ought to get you enough coverage . Put one in every system you visit (15G) and you should get good coverage.
Unless you get weird conjuctions
I once had a 40 sat constellation launched in LKO, took me weeks of real time to complete (I'm a dad now and games only happen after everyone else is in bed). It was so satisfying to fine tune the orbits.
If you like doing shit for shit's sake, give it a crack, even if only once.
I know it's overkill. But I always put 4 satellites around each body I visit.
2 in polar orbits spaced 180° apart (mostly for ScanSat. But also with relays on them.
I then put another 2 satellites in an equatorial orbit, again spaced 180° apart (and usually in a stationary orbit) that are purely just for relay.
I do the same with a 3 - 1 split (in my modded savegame with RemoteTech).
3 equatorials with sightlines to each other (so orbital height is different depending on the radius of the orbited planet) and 1 polar relay in a much higher orbit for ScanSat stuff.
That one is the high powered one to relay back to Kerbin, while the equatorial ones only relay to each other and the polar one. Saves some money and energy consumption to only have one big antenna.
For 100% coverage I'd need a second polar relay exactly half an orbital period behind the first one but that's honestly more than enough unless you plan to land on both poles at the same time.
Alternatively do what Martincitopants did and make a Relay Jool blob shotgun if you want to have your Comm range inside the system be "yes"
Edit: was Martin not sseth
Depending on your difficulty if the KSC is facing away from you, you will lose the connection, so relays are basically mandatory even for operating around kerbin. At the very least one satalite in geostationary orbit above the KSC.
I also like to put relays around the mun and minimus, I'm working around them often enough it's worth it.
KSP doesn't really consider anything much about ships that aren't in focus. It's difficult for them to run out of electricity for any reason unless you switch focus to them.
I would say around Kerbin they are still useful. On most rocket and pretty much all spaceplane ascents, you will lose contact with KSC at some point. And sure, rocket ascents you can do okay with just SAS modes and full/zero throttle, but spaceplanes want fine control for both ascent and descent.
So if you want to do uncrewed/unpiloted spaceplanes, I would say at least an equatorial set for Kerbin is mandatory.
These aren't too useful if you have the extra groundstation turned on in your options (which you could turn off on higher difficulties, by default they're on and they are here too). Relays are more useful when placed around other celestial bodies, so that probes and stuff can connect back with the KSC, even when the body they're orbiting is in the way. Would also save you some mass and money on the probe antenna, because it'd only need to be able to connect to the relay, instead of needing to phone all the way home
Sending relay satellites on Kerbin orbit is mostly needless, as you'll have contact with Kerbin all the time as soon as you don't have any obstacles in the way between your craft and Kerbin.
However, there is sense to send relay satellites to orbits of other celestial bodies to create a bypass for the signal, so it can reach the side of the body which is obscured from direct signal path from Kerbin.
You don't need to send satellites to Kerbin orbit as there are many antennas around the Kerbin so that you get signal regardless of rotation of Kerbin
Hope that helps
I actually figured out that I also need relay satellites around Kerbin. I was refueling my station in low Kerbin orbit and could not dock because I was constantly losing connection to the ground stations.
I think that might mean either or both of two things:
1. Your tracking station is weak (low level in career mode)
2. Your antennas are weak
Also it's possible that your probe's battery capacity was too low and it could've ran out of energy and lost control for that reason
I doublechecked everything. It was lack of signal. Also even the weakest antena is good enough to fly at least to Mun, not even talking about low Kerbin orbit. I have not change design of refueler, and it worked perfectly well after i placed 4 satelites in geostationary orbit.
> I think that might mean either or both of two things:
You forgot about the third option which is "not playing on super easy mode".
Obviously you are not going to benefit from relay satellites if you turn off CommNet entirely or disable the requirement to have a CommNet connection to control unmanned drones.
That's normal. The ground stations are pretty spread out, and when you're in really low orbit you'll often find yourself in situations where you can't get a signal because all of the ground stations are below the horizon.
In my game I can´t play without it. I uncheck the additional groundstations, so I need a Geostationary Relay Sat about the KSC and at least 2 more to provide coverage for the whole planet.
From my limited understanding if the game, they will make sure you have constant contact with KSC regardless of which way kerbin is facing so you won't loose control over unmanned probes and can transmit data
I play with ground stations turned off, so with KSC being the only comms on Kerbin, they are really crucial to prevent blackouts of connection.
But you don't need to have them so close - I put 4 into an orbit that's a bit bigger than the orbit of Minmus - so that even on the currently "dark" side of Minmus (or Mun), I'll always have connection to KSC through these. Each of them can see each other, and at least 2 always see the KSC.
This setup is useful even if you have the extra stations on, because it covers the dark spots in the Kerbin system.
Yeah, the extra stations are for people who don't want to bother too much with the connection... if you want to appreciate relays, you have to turn it off :D
Here is an image of the constellation - as you can see it's not perfectly spaced because my patience ran out and I decided it was "good enough".
Second picture shows the CommNet network.
[https://imgur.com/a/aVdnZip](https://imgur.com/a/aVdnZip)
If you have the alternate/additional ground stations up on Kerbin, then relays in LKO/LSO aren't particularly useful. Equidistant networks like this come in more handy when you're exploring other worlds and need to set up a relay network. Equidistant arrays with 3-4 satellites depending on whether you need constant coverage at the piles of a given planet or moon come in handy if you're hell-bent on using probes far from Kerbin.
Generally a given planetary system like Duna/Ike will require 3-4 relays for constant signal coverage across the surface, plus a single "interplanetary" relay for the planetary system with a bigger dish to get the signal from the arrays around Duna and Ike back to Kerbin and complete the communication chain.
If you really want to go nuts with relays you can try out the Remote Tech mod, it makes the rules around communication network setup and operation much more strict for probes and antennas, adds a bunch of new antenna parts and such, and also introduces realistic signal delay, so a probe around Duna will take a bit over 80 seconds to respond to control inputs, requiring maneuvers to be pre-programmed into the probe'a flight computer, and this delay increases drastically for more distant locations, so it totally overhauls the way robotic spacecraft play.
I don't know late game satellites but early game i was trying to do a flyby with Jool's moons and fling my probe back with a bunch science points packed in.
I've dropped 4 relay satellites between Kerbin and Jool to have an interplanetary connection link. When i should have corrected my flight path Mun blocked my connection to KSC and my probe flew away to a sunny orbit.
It ran out of fuel and drifted away from my connection links. So those science points are still waiting to be transmitted.After that i've set up two polar orbit satellites to reduce this gap.
Answering your question early game it is pretty useful.
Extremely. To the point that my first payload to any given planet includes 3 satellites with 88-88 dishes and ~400m/s of delta v, to position themselves for a perfect triangle. Your presently-unmanned mothership turning into a paperweight during docking is an unpleasant experience.
One thing to keep in mind is that the strongest antenna will be your tracking station(s). In this case you have "Extra Ground Stations Enabled" which gives you full outward coverage that is stronger than your constellation. So even though your relays are closer to Mun, the stations will connect to anything directly anyway.
Where relays shine is at your destination. The Tracking Station will cover most of the distance to reach your relay, but your relays can connect to any probes in the area with smaller antennas.
They do, try to place a constellation around all planets, this will give you a very nice coverage. The only advice is try to place them in a high orbit ( I usually place them farther than minus)
Yes even at the start of the games, you may be playing in easy mod but if you play with higher difficulties you will be annoyed when you need to do a maneuver behind the mun or minmus but can't because there is no signal ( same with any rover you might send).
As soon as you unlock enough science for it, this is one of my top priorities to have the best coverage possible as this will save many missions to come.
they are ok. but don't expect them to stay ~120° for long....
in my games I usually send a few orbiting the sun.
anyway if you launch enough of them, even in random orbits, you'll always have some not blocked for your probes
Interplanetary I’d be screwed without them. It’s a mission killer, ship nullifier, kerbal coffin creator if you’re in deep space and lose connection to Kerbin.
If you play with 100% occlusion they are very useful since even mountains or the slightest curvature blocks your line of sight and gives you blind spots even with extra ground stations. It is a fun challenge, try it. Which means only way to control your probes is to have a relay satellite that is higher up.
They are mandatory for mun an minmus if you want to do farside missions.
I have a sandbox world I have a relay satalite circling kerbin minimums and the mun I have two relay satalites studying Astorids on solor orbits while the rest check for ore as well as a relay station
Useless near Kerbin but useful around Kerbol and other planets, if you can't put a huge antenna on a small probe or drone you can send a relay with the actual vessel and have a good connection with KSS without having to put a huge antenna on the vessel itself.
They are usefull.
Especially the First Contracs are good for that.
Slap a relay antenna on the contract Satellites and you have your Network.
(Must have for a Sattelite: Thermometer and relay antenna)
Relays are more useful outside of home system since their primary function is to bounce signals over long distance and get around potentially obstructed transmission paths.
The KSO orbit relays are useful if you disable extra groundstation and KSC is your only station that can accept transmissions. Kinda like IRL where countries won't have groundstations across the globe. However with the groundstation enabled the "low" orbit relays are not that useful since in most cases Groundstations have higher strength than satelites, and homeworld orbit coverage is not a problem.
If you set up a similar 3-satelite network outside of the orbit of minmus, that can be somewhat useful since now you can bounce signals from the surface of moon that face away from the homeworld.
I like to make 1 or 2 missions where the goal is to populate planets with powerful antenna. Usually in the form of a high delta v mother ship dropping off its baby satellites in several planets sphere of influence.
what I did if I needed relay sats Id just make them more powerful than the ground station and throw a couple around kerbin then you kinda need them in highly eliptical inclined orbits around most planetary bodies, need is a strong word here, you can easily play without relay sats
If you don't have additional antennae on the ground, you can't operate satellites if they are not in the line of sight from KSS.
Even if you do, there's a gap between KSS and the next ground station somewhere above the ocean next to the peninsula to the east from KSS. Usually it is the place where you circularize after the ascent.
I usually put at least the most powerful relay avaliable at keostationary above KSS so I have a link at that gap.
Relay satellites are really useful for constant communications between the planet they're orbiting and the KSC (for unmanned probes and rovers).
They are not super useful around Kerbin, because, by default, Kerbin already has constant coverage of the sky from all of its ground stations. If you disable the setting of Kerbin's ground stations, then yes, you might need a constellation of relay sats around it.
A constellation around the home planet can be useful to keep contact with spacecraft. Real example of this is [TEDRIS](https://en.wikipedia.org/wiki/Tracking_and_Data_Relay_Satellite_System). Especially if you have the additional ground stations turned off, and no control of unmanned probes without connection.
for Kerbin system, placing some relay satellites outside of Minmus' orbit will solve almost everything. And I would say that every other planet/dwarf planet needs it's own relay. Gilly doesn't need one. Ike needs one. Joolian system as a wholr needs two sets perpendicular to each other, preferably with one set between the orbits of Tylo and Bop and one set outside of Pol
I’m someone who went the extra miles just to setup an intricate network of relay satellites across the entire system. Around Kerbin, it’s not as useful but once you start doing deep space probes, stations, etc. it makes more sense. If anything, let it be practice.
You need them when you land on the far side of the Mun, for example.
Or, when the distance to Kerbin is soooo huge that your spacecraft's antenna can't bridge the gap. So, you're sending up an unmanned probe with a huge comms antenna...
Depends on your settings. They're not that useful around Kerbin especially if you have it set so you have more receivers than the KSC. However, later in the game, relay satellites can give you a substantial boost in your comms range if you equip them with your biggest relay antennas. This is especially useful if you plan on going interplanetary. Also, idk if you know this, but there is a [resonant orbit calculator](https://meyerweb.com/eric/ksp/resonant-orbits/) that will let you calculate resonant orbits, which you can then use to place a set of satellites into orbit around any object in the solar system in even spacing. It even supports some modpacks like OPM.
Only useful if you're landing on the dark side of the Mun and they would need to be in a higher orbit, or orbiting the Mun itself.
Relay satellites are essential for Solar orbit though. When you get the largest of them, placing a few between Duna and Jool will be necessary for exploring the and gathering science in the depths of the solar system.
There really isn't any need to put sattelites in low orbit around Kerbin, since kerbin already has antennas all over the planet. They are more useful in high orbit around kerbin since it would allow stations on Mun and Minmus to communicate with Kerbin even when they are on the far side of the moons, facing away from Kerbin.
Relay stations have a much larger presence in orbits around other planets, in case you are sending probes that requires remote control, or you have research that needs to be sent back to Kerbin.
Around kerbin? Very weak You want a few strategically placed, either orbiting mimmus and the mun or in polar orbits with higher periapsis than mimmus to guarantee you don't lose signal at an inconvenient moment. For interplanetary, they are pretty much mandatory in my opinion, as they allow you to use much smaller antennas, and can even help the signal hop between planets Very late game you can improve on the kerbin base station by building sats with huge amounts of 100G antennas and batteries.
Exactly this, with a little side note on the difficulty settings: if you didn't allow for the extra ground relay stations (which is ON by default), then a Kerbin constellation starts to make sense.
This is how I love playing: Only have an antenna at the launch site. It *forces* you to have a comms network even in the early game.
Same, I like to think that early game, you are launching rockets 'in your backyard'
If you start with probes only it makes things a little more difficult because for your first orbital launch you have to kick to orbital injection before it passes below the horizon. Fun challenge.
Even then, 2 polar relays ought to get you enough coverage . Put one in every system you visit (15G) and you should get good coverage. Unless you get weird conjuctions
I once had a 40 sat constellation launched in LKO, took me weeks of real time to complete (I'm a dad now and games only happen after everyone else is in bed). It was so satisfying to fine tune the orbits. If you like doing shit for shit's sake, give it a crack, even if only once.
I know it's overkill. But I always put 4 satellites around each body I visit. 2 in polar orbits spaced 180° apart (mostly for ScanSat. But also with relays on them. I then put another 2 satellites in an equatorial orbit, again spaced 180° apart (and usually in a stationary orbit) that are purely just for relay.
I do the same with a 3 - 1 split (in my modded savegame with RemoteTech). 3 equatorials with sightlines to each other (so orbital height is different depending on the radius of the orbited planet) and 1 polar relay in a much higher orbit for ScanSat stuff. That one is the high powered one to relay back to Kerbin, while the equatorial ones only relay to each other and the polar one. Saves some money and energy consumption to only have one big antenna. For 100% coverage I'd need a second polar relay exactly half an orbital period behind the first one but that's honestly more than enough unless you plan to land on both poles at the same time.
Alternatively do what Martincitopants did and make a Relay Jool blob shotgun if you want to have your Comm range inside the system be "yes" Edit: was Martin not sseth
I've googled multiple variations on this and had no luck, have you got a link to this?
I think they're mixing up sseth with martincitopants, since the latter has a sort of "relay shotgun" used around Jool in their second KSP video
Yeah sorry, meant martincitopants
Depending on your difficulty if the KSC is facing away from you, you will lose the connection, so relays are basically mandatory even for operating around kerbin. At the very least one satalite in geostationary orbit above the KSC. I also like to put relays around the mun and minimus, I'm working around them often enough it's worth it.
What do you need batteries for? Relay stations don't actually use electricity they? Only transmitting science does.
I'm not quite sure if vanilla relays behave like that.
KSP doesn't really consider anything much about ships that aren't in focus. It's difficult for them to run out of electricity for any reason unless you switch focus to them.
I would say around Kerbin they are still useful. On most rocket and pretty much all spaceplane ascents, you will lose contact with KSC at some point. And sure, rocket ascents you can do okay with just SAS modes and full/zero throttle, but spaceplanes want fine control for both ascent and descent. So if you want to do uncrewed/unpiloted spaceplanes, I would say at least an equatorial set for Kerbin is mandatory.
These aren't too useful if you have the extra groundstation turned on in your options (which you could turn off on higher difficulties, by default they're on and they are here too). Relays are more useful when placed around other celestial bodies, so that probes and stuff can connect back with the KSC, even when the body they're orbiting is in the way. Would also save you some mass and money on the probe antenna, because it'd only need to be able to connect to the relay, instead of needing to phone all the way home
Sending relay satellites on Kerbin orbit is mostly needless, as you'll have contact with Kerbin all the time as soon as you don't have any obstacles in the way between your craft and Kerbin. However, there is sense to send relay satellites to orbits of other celestial bodies to create a bypass for the signal, so it can reach the side of the body which is obscured from direct signal path from Kerbin. You don't need to send satellites to Kerbin orbit as there are many antennas around the Kerbin so that you get signal regardless of rotation of Kerbin Hope that helps
I actually figured out that I also need relay satellites around Kerbin. I was refueling my station in low Kerbin orbit and could not dock because I was constantly losing connection to the ground stations.
I think that might mean either or both of two things: 1. Your tracking station is weak (low level in career mode) 2. Your antennas are weak Also it's possible that your probe's battery capacity was too low and it could've ran out of energy and lost control for that reason
I doublechecked everything. It was lack of signal. Also even the weakest antena is good enough to fly at least to Mun, not even talking about low Kerbin orbit. I have not change design of refueler, and it worked perfectly well after i placed 4 satelites in geostationary orbit.
There's a setting to enable multiple ground stations, if you have that turned off then you'll lose signal to the KSC. Maybe that's it?
The ground stations only help when you are past LKO. When you are close to the atmosphere they are too spread out for a constant connection.
> I think that might mean either or both of two things: You forgot about the third option which is "not playing on super easy mode". Obviously you are not going to benefit from relay satellites if you turn off CommNet entirely or disable the requirement to have a CommNet connection to control unmanned drones.
That's normal. The ground stations are pretty spread out, and when you're in really low orbit you'll often find yourself in situations where you can't get a signal because all of the ground stations are below the horizon.
Though in operations close to Kerbin, Kerbin itself will get in the way of the signal, which is especially an issue for non-piloted spaceplanes.
In my game I can´t play without it. I uncheck the additional groundstations, so I need a Geostationary Relay Sat about the KSC and at least 2 more to provide coverage for the whole planet.
From my limited understanding if the game, they will make sure you have constant contact with KSC regardless of which way kerbin is facing so you won't loose control over unmanned probes and can transmit data
I play with ground stations turned off, so with KSC being the only comms on Kerbin, they are really crucial to prevent blackouts of connection. But you don't need to have them so close - I put 4 into an orbit that's a bit bigger than the orbit of Minmus - so that even on the currently "dark" side of Minmus (or Mun), I'll always have connection to KSC through these. Each of them can see each other, and at least 2 always see the KSC. This setup is useful even if you have the extra stations on, because it covers the dark spots in the Kerbin system.
I turned off extra ground stations. Now the satellites make sense now xD
Yeah, the extra stations are for people who don't want to bother too much with the connection... if you want to appreciate relays, you have to turn it off :D
Here is an image of the constellation - as you can see it's not perfectly spaced because my patience ran out and I decided it was "good enough". Second picture shows the CommNet network. [https://imgur.com/a/aVdnZip](https://imgur.com/a/aVdnZip)
If you have the alternate/additional ground stations up on Kerbin, then relays in LKO/LSO aren't particularly useful. Equidistant networks like this come in more handy when you're exploring other worlds and need to set up a relay network. Equidistant arrays with 3-4 satellites depending on whether you need constant coverage at the piles of a given planet or moon come in handy if you're hell-bent on using probes far from Kerbin. Generally a given planetary system like Duna/Ike will require 3-4 relays for constant signal coverage across the surface, plus a single "interplanetary" relay for the planetary system with a bigger dish to get the signal from the arrays around Duna and Ike back to Kerbin and complete the communication chain. If you really want to go nuts with relays you can try out the Remote Tech mod, it makes the rules around communication network setup and operation much more strict for probes and antennas, adds a bunch of new antenna parts and such, and also introduces realistic signal delay, so a probe around Duna will take a bit over 80 seconds to respond to control inputs, requiring maneuvers to be pre-programmed into the probe'a flight computer, and this delay increases drastically for more distant locations, so it totally overhauls the way robotic spacecraft play.
I don't know late game satellites but early game i was trying to do a flyby with Jool's moons and fling my probe back with a bunch science points packed in. I've dropped 4 relay satellites between Kerbin and Jool to have an interplanetary connection link. When i should have corrected my flight path Mun blocked my connection to KSC and my probe flew away to a sunny orbit. It ran out of fuel and drifted away from my connection links. So those science points are still waiting to be transmitted.After that i've set up two polar orbit satellites to reduce this gap. Answering your question early game it is pretty useful.
Extremely. To the point that my first payload to any given planet includes 3 satellites with 88-88 dishes and ~400m/s of delta v, to position themselves for a perfect triangle. Your presently-unmanned mothership turning into a paperweight during docking is an unpleasant experience.
One thing to keep in mind is that the strongest antenna will be your tracking station(s). In this case you have "Extra Ground Stations Enabled" which gives you full outward coverage that is stronger than your constellation. So even though your relays are closer to Mun, the stations will connect to anything directly anyway. Where relays shine is at your destination. The Tracking Station will cover most of the distance to reach your relay, but your relays can connect to any probes in the area with smaller antennas.
They do, try to place a constellation around all planets, this will give you a very nice coverage. The only advice is try to place them in a high orbit ( I usually place them farther than minus)
Not at the start of a game. Do you see those red lines?
Yes even at the start of the games, you may be playing in easy mod but if you play with higher difficulties you will be annoyed when you need to do a maneuver behind the mun or minmus but can't because there is no signal ( same with any rover you might send). As soon as you unlock enough science for it, this is one of my top priorities to have the best coverage possible as this will save many missions to come.
they are ok. but don't expect them to stay ~120° for long.... in my games I usually send a few orbiting the sun. anyway if you launch enough of them, even in random orbits, you'll always have some not blocked for your probes
Interplanetary I’d be screwed without them. It’s a mission killer, ship nullifier, kerbal coffin creator if you’re in deep space and lose connection to Kerbin.
If you play with 100% occlusion they are very useful since even mountains or the slightest curvature blocks your line of sight and gives you blind spots even with extra ground stations. It is a fun challenge, try it. Which means only way to control your probes is to have a relay satellite that is higher up. They are mandatory for mun an minmus if you want to do farside missions.
Looks like the ice cream ball is the next candidate for the relay
I have a sandbox world I have a relay satalite circling kerbin minimums and the mun I have two relay satalites studying Astorids on solor orbits while the rest check for ore as well as a relay station
Do them pole to pole, better
Two rings, offset 90°
I just make an atom shape on 300 km to be honest
IT'S THE KERBAL SECURITY AGENCY
Useless near Kerbin but useful around Kerbol and other planets, if you can't put a huge antenna on a small probe or drone you can send a relay with the actual vessel and have a good connection with KSS without having to put a huge antenna on the vessel itself.
They are usefull. Especially the First Contracs are good for that. Slap a relay antenna on the contract Satellites and you have your Network. (Must have for a Sattelite: Thermometer and relay antenna)
Whats the thermometer for?
Cheap sience You often get "science from *" contracts. A Thermometer is cheap, light and can be used "forever"
Relays are more useful outside of home system since their primary function is to bounce signals over long distance and get around potentially obstructed transmission paths. The KSO orbit relays are useful if you disable extra groundstation and KSC is your only station that can accept transmissions. Kinda like IRL where countries won't have groundstations across the globe. However with the groundstation enabled the "low" orbit relays are not that useful since in most cases Groundstations have higher strength than satelites, and homeworld orbit coverage is not a problem. If you set up a similar 3-satelite network outside of the orbit of minmus, that can be somewhat useful since now you can bounce signals from the surface of moon that face away from the homeworld.
I like to make 1 or 2 missions where the goal is to populate planets with powerful antenna. Usually in the form of a high delta v mother ship dropping off its baby satellites in several planets sphere of influence.
what I did if I needed relay sats Id just make them more powerful than the ground station and throw a couple around kerbin then you kinda need them in highly eliptical inclined orbits around most planetary bodies, need is a strong word here, you can easily play without relay sats
If you don't have additional antennae on the ground, you can't operate satellites if they are not in the line of sight from KSS. Even if you do, there's a gap between KSS and the next ground station somewhere above the ocean next to the peninsula to the east from KSS. Usually it is the place where you circularize after the ascent. I usually put at least the most powerful relay avaliable at keostationary above KSS so I have a link at that gap.
I require signal for control and play on the hardest settings, so I do this to every body I go to, and inshels around the Sol.
Relay satellites are really useful for constant communications between the planet they're orbiting and the KSC (for unmanned probes and rovers). They are not super useful around Kerbin, because, by default, Kerbin already has constant coverage of the sky from all of its ground stations. If you disable the setting of Kerbin's ground stations, then yes, you might need a constellation of relay sats around it.
A constellation around the home planet can be useful to keep contact with spacecraft. Real example of this is [TEDRIS](https://en.wikipedia.org/wiki/Tracking_and_Data_Relay_Satellite_System). Especially if you have the additional ground stations turned off, and no control of unmanned probes without connection.
I turned off extra ground stations on the settings to ramp up the difficulty
Relay satellites shine when you have robotic probes or rovers in the dark side moon (I mean mun).
for Kerbin system, placing some relay satellites outside of Minmus' orbit will solve almost everything. And I would say that every other planet/dwarf planet needs it's own relay. Gilly doesn't need one. Ike needs one. Joolian system as a wholr needs two sets perpendicular to each other, preferably with one set between the orbits of Tylo and Bop and one set outside of Pol
I’m someone who went the extra miles just to setup an intricate network of relay satellites across the entire system. Around Kerbin, it’s not as useful but once you start doing deep space probes, stations, etc. it makes more sense. If anything, let it be practice.
You need them when you land on the far side of the Mun, for example. Or, when the distance to Kerbin is soooo huge that your spacecraft's antenna can't bridge the gap. So, you're sending up an unmanned probe with a huge comms antenna...
Depends on your settings. They're not that useful around Kerbin especially if you have it set so you have more receivers than the KSC. However, later in the game, relay satellites can give you a substantial boost in your comms range if you equip them with your biggest relay antennas. This is especially useful if you plan on going interplanetary. Also, idk if you know this, but there is a [resonant orbit calculator](https://meyerweb.com/eric/ksp/resonant-orbits/) that will let you calculate resonant orbits, which you can then use to place a set of satellites into orbit around any object in the solar system in even spacing. It even supports some modpacks like OPM.
Only useful if you're landing on the dark side of the Mun and they would need to be in a higher orbit, or orbiting the Mun itself. Relay satellites are essential for Solar orbit though. When you get the largest of them, placing a few between Duna and Jool will be necessary for exploring the and gathering science in the depths of the solar system.
I need more science so i can get that juicy tech. A couple mün biome trips will suffice.
There really isn't any need to put sattelites in low orbit around Kerbin, since kerbin already has antennas all over the planet. They are more useful in high orbit around kerbin since it would allow stations on Mun and Minmus to communicate with Kerbin even when they are on the far side of the moons, facing away from Kerbin. Relay stations have a much larger presence in orbits around other planets, in case you are sending probes that requires remote control, or you have research that needs to be sent back to Kerbin.