Verify my satcom? (RemoteTech2)

[travisneids]

I plan on sending up a few communication satellites into KEO and I want to verify I have enough power capacity.

1 DP-10 = 0.01 c/s

3 DTS-M1 = 2.46 c/s (0.82)

3 KR-7 = 2.46 c/s (0.82)

Total c/s = 4.93 c/s

The total length of darkness at 2,868,750m = 1200 (1195.28) seconds.

4.93*1200 = 5916 capacity needed.

I only have a max of 200 capacity (the Z-200 Rechargeable Batteries). 5916/200 = 30 (29.58). So that would mean I would need 30 batteries?

Thanks!

[travisneids]

I guess thinking about it a little longer my math is assuming all 7 communication parts will be transmitting 100% of the time in darkness. The probability of that is properly not very likely?

[Streetwind]

Yeah, if you manually deactivate some dishes while they are not needed, your satellite is going to consume less energy. But well, you have all these dishes on board, so you're eventually going to use all of them in parallel, right? As such, you're going to have to plan with the full energy drain anyway.

The question is though, what do you need six dishes on every single satellite for - especially since all of these dishes have no use outside Kerbin's SoI? That's an excessively inefficient setup, making it no surprise that the battery requirements are very large. You're basically using a mainsail and an orange tank in order to land a single-Kerbal pod on the Mun, to make an analogy.

- A typical geostationary commsat constellation consists of between 3 and 6 satellites. At any given time, KSC sees two or three in a hexagon constellation, two in a pentagon, one or two in a square and only a single one in a triangle. So in most cases, at least two thirds of your satellites are not seeing KSC, and because they're geostationary, they in fact will never see KSC. Why carry a dedicated, energy hungry dish to connect to KSC, then?

- If every satellite connects to both of its neighbours, then each satellite will have two valid link paths to KSC, and that's one more than necessary. If more than one sat connects to KSC, that's also redundant. If a single link is enough, why pay more for two or three? Even if you play with communications delay, making a ring trip around geostationary at lightspeed is negligible (comparable to Kerbin-Mun distance). This combined with the above allows you to downsize to two inter-link dishes: sat 1 connects to KSC and sat 2, sat 2 connects to sat 1 and sat 3, sat 3 connects to sat 2 and has a free dish for spacecraft connections (or connects to sat 4 if your constellation is larger, and so on).

- An object in Kerbin orbit (and that includes Mun and Minmus) can see a minimum of half the geostationary constellation at all times. Going out to the Mun, it's going to see more than 95% of the constellation at all times - in other words, except for brief, single-sat eclipse moments every once in a while, it's going to see all satellites. As a result of this, dedicating dishes of more than two satellites to cover Mun and Minmus links is unecessary. This allows you to downsize to two service communication dishes even on the minimum size triangle constellation: sat 1 does Mun & a spacecraft, sat 2 does Minmus & a spacecraft, and sat 3 does Mun & Minmus... and since it probably has a free dish left (see above), it can also do a spacecraft! Having larger constellations adds even more free links.

So with these three points alone, you're down to 2 DTS-M1 and 2 KR-7 per sat, bringing your power use down to less than 3.3 Ec/s, and your required battery capacity to less than 4000.

However, there's a whole lot more to save, if you play with the standard size Kerbin system (no RSS) and think outside the box.

The shortest range dish covers 50 million kilometers of distance. At standard size Kerbin geostationary altitude, you're never more than 2.9 million kilometers from KSC. Why use such an oversized antenna to connect to KSC? And in fact, why use it to connect to other geostationary sats, which are not much further away? If you build at least a square, your commsats will be so close to each other that you need zero dishes for inter-sat relay work!

I have a geostationary commsat network in square configuration. Each of these satellites has one antenna. Yes, just one single antenna, a communotron-32 consuming 0.6 Ec/s. Nothing else. Even when factoring in the probe core, they need less than 800 Ec battery capacity to make it through the eclipse period. They are 4.9 million kilometers apart from each other, and the ominidirectional link ensures no signal needs to take more than one relay hop to reach a sat that has a KSC uplink. Also, the omnidirectional link allows for an unlimited number of spacecraft connections in any equatorial Kerbin orbit out to over a third of the way to the Mun; polar orbits have less coverage, but still plenty more than any SCANsat module requires to be at optimal height. Here's a picture, and a two-minute MS Paint coverage area visualization.

Since taking that picture, I have added a pair of sats with one comm-32 and two DTS-M1 each. They both do Mun and Minmus cone mode connections. Thanks to the omnidirectional links on the comm-32, it is almost completely irrelevant where I put them. They don't have to be geostationary, or or part of a constellation, or even have to be lined up on opposite sides of Kerbin. I could be really sloppy and have them as close as a fifth of an orbit to each other at 2 million km height with some eccentricity. They always hook up to the geostationary relays, and as long as they share the same orbital period to avoid drifting, anything in Mun and Minmus SoI will always see at least one of the two. And that's the theme for future commsats with interplanetary antennas as well: I can just half-assedly fling one up there whenever I need a new one. As long as it carries a comm-32, it always connects to at least two members of the geostationary quartett, and since the number of sats in Kerbin orbit with comm-32's on them will only be going up over time, it's likely that it can find even faster, more direct links via lower orbiting sats. Omnidirectional links, baby!

The close shave of 4.9 million km inter-sat distance makes setting this up require some fiddlyness and satellite babysitting, but you could got for a pentagon instead of a square and get away with being much less precise.

[RainDreamer]

Well, yes. If you are going to load up all those antennas, of course it will take a ton of energy. However, a good way to relieve you of the energy problem are the RTGs. Slap some PB-NUK on. They generate 0.75 EC/s. So if you are using 4.93 EC/s, 4 PB-NUK would give you 3 EC/s to counter that, effectively lower your energy consumption down to 1.93 EC/s, which would be more managable with less batteries count. The drawback, is of course the price. Those RTG aren't cheap.

Also reccomend you to take near future electrical - it has a more powerful, larger RTG that generate 3EC/s along with many more batteries in different form factors, allowing you to add more EC but less part count.

[Streetwind]

It's a bit of a stretch to assume that he has access to PB-NUKs, when he doesn't even have access to batteries bigger than Z-200's... they're in the same branch

[RainDreamer]

I was under the impression that the OP was trying to keep the form factor of the sat small for easy launch from a cargo bay. I supposed I missed that bit...

[travisneids]

This community rules. Back to the drawing board! Thank you RainDreamer and Streetwind. Really appreciate your time.

I'll be sure to follow up with my new results!

[bandi94]

For the start you can place 4 satellites somewhere at 1,000km.

Construction : - Reflectron DP-10 ( attached to the main body for launch , after the satellite is in position deatach it , there is no more need for it and it will only waste the energy)

: - 1 x Communtron 16 ( for satellite- satellite communication ( aka relay the signal between them ) , and satellite - Kerbin )

Now you have a stable 2,700km circular coverage.

: for a small trip to the Mun or so you can add 1x ( or 2x ) of DTS-M1 ( you can point one to Mun and one to any Active vessel ).

With this setup you will have a stable ( no black-out) coverage anywhere between Kerbin and Mun ( beyond Mun at some point Mun may block the signal so you will have to cover Mun with extra 3 satellite)

If i remember well my satellites had 4x 200 charge batteries with both of the DTS-M1's activated the satellite remained without power for a short period of time , so 5x batteries will be needed if you want to activate both of the DTS-M1's

For simple calculations : http://ryohpops.github.io/kspRemoteTechPlanner/

And a small tutorial :

Edited December 11, 2014 by bandi94

[travisneids]

For the start you can place 4 satellites somewhere at 1,000km.

Construction : - Reflectron DP-10 ( attached to the main body for launch , after the satellite is in position deatach it , there is no more need for it and it will only waste the energy)

: - 1 x Communtron 16 ( for satellite- satellite communication ( aka relay the signal between them ) , and satellite - Kerbin )

Now you have a stable 2,700km circular coverage.

: for a small trip to the Mun or so you can add 1x ( or 2x ) of DTS-M1 ( you can point one to Mun and one to any Active vessel ).

With this setup you will have a stable ( no black-out) coverage anywhere between Kerbin and Mun ( beyond Mun at some point Mun may block the signal so you will have to cover Mun with extra 3 satellite)

If i remember well my satellites had 4x 200 charge batteries with both of the DTS-M1's activated the satellite remained without power for a short period of time , so 5x batteries will be needed if you want to activate both of the DTS-M1's

For simple calculations : http://ryohpops.github.io/kspRemoteTechPlanner/

And a small tutorial :

Awesome. Thanks for the additional information.

I believe I was using an outdated tutorial or a tutorial that shouldn't necessarily be a tutorial haha.

[bandi94]

Good Luck with them. Make sure you match the orbital period's ( with an error of 0.01s - 0.05s ) if not after couple of day's they will 'drift' away from the current formation and you will end up with big black-out spots.

If you do it right you will have something like this: