CommNet without base antenna

[Warzouz]

I've restarted a game with only KSC antenna.

I'll start firing some CommNet sats. I think 4 in polar a quite large orbit (500km).  Am I right ?

[Tex_NL]

500km orbit isn't a 'large orbit'. In fact it is quite low for a commnet. Personally I would go at least two to four times that high. (Synchronous orbit is at 2 863.33km)

Properly set-up four would get you a pretty decent coverage although it might leave a few blind spots from time to time.
Three, equally spaced equatorially could guarantee full coverage for the entire planet except the very poles. (Another set of three polar would give full coverage at any time of day.)
Another option for near perfect coverage would be two equatorially, but exactly opposite each other, and a similar set of two in a polar orbit. But in contrast to just three equatorially this time the blind spots won't be static and only last a short time.

Edited March 12, 2017 by Tex_NL

[Streetwind]

Since you have one single ground station, your goal is having a ring of satellites which can all talk to each other, while at any given time at least one is in range of the ground station. And "in range" can of course mean different things, because there's this concept of range-based signal strength, and bonuses associated with having lots of it.

The minimum size for a ring of satellites that fulfills these criteria is three, in a triangle configuration. But that configuration also results in the maximum distance between the satellites themselves, so in order to keep that distance within the range of your antennas, you will have to put them in quite a close orbit. When you increase the number of satellites, then the distance between any given two satellites gets smaller, which means the constellation can inhabit a higher orbit while still staying in range of each other.

So the answer to the question of "how many satellites should I launch into an orbit of which altitude?" is based on the distance you can support between any two satellites. This distance in turn is based on your antenna technology, and the difficulty settings for the commnet feature that you chose at game start. Better antennas have more range, so you need fewer satellites in the same orbit. But, you can also stack antennas on the same satellite to boost the satellite's total range. So you need fewer satellites with two antennas each than you need satellites with one antenna each, even if the antenna is the same in all cases.

You can find formulas for antenna range calculation as well as antenna stacking here on the wiki. Unfortunately, I've never found a reliable documentation for the combinability exponent that you need to calculate the latter, but I've been led to believe that it is 0.75 for most antennas, and 1.0 for a select few. Your best bet is probably to assume 0.75 in every case; the worst result that can give you is that you accidentally build margin into your system.

 

As for polar orbits: that is inadvisable, because it doesn't fulfill the condition of at least one satellite being in range of the ground station at all times. KSC will rotate away from the plane of your polar ring of satellites. You will need multiple polar rings with multiple satellites each. How many rings and how many satellites once again depends on how much distance you can support between satellites, but it very quickly gets very complicated because you now need to have the interleaving and orbital phasing between the different satellites factor into your calculation. This can get arbitrarily complex; for an extreme example, refer to the European Galileo navigation system's three interleaved polar rings of nine satellites each, which seek to fulfill the goal of having a minimum number of nine satellites visible from any point on the surface of the Earth at all times.

Edited March 12, 2017 by Streetwind

[Tex_NL]

If it is just for an initial LKO commnet you won't really have to worry about antenna range. Even the early relays have more than enough power to talk to each other in LKO (with stock antenna range settings).
Slap two HG-5's on an QBE, OKTO or HECS probe with a couple of OX-STAT's and a battery and you're done. Simple, cheap and effective.

Once you're ready to go into deep space you can easily supplement your network with better tech.

Edited March 12, 2017 by Tex_NL

[bewing]

You can't really make an effective network out of HG-5 antennas, which is what I assume you have (unless the point of the network is for airplanes on Kerbin to communicate with KSC).

Yes, you can put them up and arrange them nicely. And they can talk to each other.

But it is difficult to set it up so that you can communicate with that network, even from the Mun (you need a second relay halfway to the Mun -- plus extra antennas on every ship, to do it). And it's completely impractical to communicate with that relay network from anywhere beyond the Mun. So there's really no point until you get the RA-2, and then they should be spaced out much further.

 

 

 

[Warzouz]

For now, I've only the basic HG5 relay and my tracking station is level 2. I only need basic com net to stat firing satellites to get better cash income. to be allowed to unlock more science stuff...

I'll deal with a proper network later

[Tex_NL]

If you want a commnet just for control HG-5's are more than capable. I just tested it; in synchronous orbit two probes each with two HG-5's have a signal strength of roughly 20%. Poor for science transmission but more than enough for control.

Edit: I just realized I forgot an important piece of information.
The two relays I talked about were part of an equally spaced three constellation putting them roughly 3460 km apart.

Edited March 12, 2017 by Tex_NL

[CSE]

1 hour ago, Tex_NL said:

If you want a commnet just for control HG-5's are more than capable. I just tested it; in synchronous orbit two probes each with two HG-5's have a signal strength of roughly 20%. Poor for science transmission but more than enough for control.

In early career, just one HG-5 relay may be enough, located around 60 degrees east of KSC to give you control for just long enough to establish a stable orbit. Use this relay for control only; store any science for transmission as you pass over the KSC ground station.

Then keep an eye out for satellite contracts with usable orbits that can pay you to increase your relay coverage. I don't usually build my ideal Kerbin network until I have top-tier relay dishes available.

[Spricigo]

I'd say if your concern it's satellite contracts you don't need to worry about proper setup at all. Each satellite you launch will add some coverage, at the time you have a dozen or so blind spots will practically be gone.

The inconvenience is to use inefficient launch profiles in the first launches since otherwise you may lose control before reaching orbit.

[Snark]

14 hours ago, Streetwind said:

Unfortunately, I've never found a reliable documentation for the combinability exponent that you need to calculate the latter, but I've been led to believe that it is 0.75 for most antennas, and 1.0 for a select few.

It is, in fact, 0.75 by default.  So, any antenna that doesn't explicitly specify antennaCombinableExponent in its config will have that value.

I believe that the Communotron-16 is the only antenna in the stock game that overrides the 0.75 default (its exponent is 1).  I say "believe" because I'm not in front of my KSP computer at the moment and therefore can't trivially grep all the configs to find it. 

14 hours ago, bewing said:

You can't really make an effective network out of HG-5 antennas

Depends what you want.  HG-5's will cover near-Kerbin space just fine, so you've got control of all your ships from LKO out to a few thousand kilometers.

Also, you can get to the Mun with them, if you're willing to stack 'em.  For example, two ships with 4 HG-5's each will be able to communicate over a distance of up to 14,000 km, if I'm doing my math right.  Agreed that it's not ideal, and really what you want is the RA-2 once you get away from Kerbin.

 

[Streetwind]

6 hours ago, Snark said:

It is, in fact, 0.75 by default.  So, any antenna that doesn't explicitly specify antennaCombinableExponent in its config will have that value.

Awesome. Went ahead and made a note on the community API documentation