Geostationary Orbit?

[mattcooperkay]

So I recently downloaded Remote Tech, previously logged hundreds of hours, but I admit I'm not the most skilled (Haven't travelled past Minmus yet).

Maybe I'm jumping ahead of myself but I'm wondering how I'd get a satellite into a geostationary orbit to start my satellite network around Kerbin?

Here's where the orbit's at...

Any advice on how I'd go about making that a stable geostationary orbit? Would appreciate any tips...

Cheers

[RainDreamer]

Your orbital period must be exactly the same as the rotational speed of kerbin. So 6 hours. Bring it up to that, then you got yourself a geostationary orbit. I believe that is somewhere about 2800km? Can't remember at the moment. Remember that if you go higher than that mark, then you would be slower than the rotation of kerbin, and move west, while if you go lower than that, you are moving faster than the rotation of kerbin, and you would go east (assuming that you launched eastward in the beginning). Fiddle with it till you get where you want relative to the surface.

That said, maybe you would prefer to make a set of closer relay satellites just so that the signal can travel all around kerbin first, before sending more stuff further away. Flying that far away means you would lose control to the satellite for quite a while before connection is re-established.

[Streetwind]

Any orbit with 6:00:00 hours orbital period is geosynchronous; if it has that period and is also circular and equatorial, it's geostationary. To achieve that, circularize at 2868.75 km altitude. Because you'll never be 100% precise with this, you may have to perform stationkeeping every so often to keep your constellation in shape and position. Just like real commsats

And yeah, getting unmanned satellites there without LKO relays can be tricky. But it can be done. Just four geostationary sats using a single Communotron-32 each. The first one launched was the top one, which I pushed to sit just over the horizon with respect to KSC, in the direction of takeoff. It involved launching a steeper than usual ascent, a hasty circularization burn to push the periapsis out of the atmosphere, and then waiting for it to come around in its orbit so I could regain control. The higher you raise your orbit - especially above KSC, which can be assisted with radial burns - the longer you have control and the more easily you can keep raising the orbit further. It helps that if your orbit is highly elliptical and goes out all the way to geostationary, your satellite will be moving much slower than Kerbin at its apoapsis and therefore KSC "catches up" with you. Because of this I think I only needed two orbits (three at most, but I think it was two) to get to geostationary altitude and circularize. And after that one was in place, the increased downrange communication distance made launching the other three a breeze.

There are of course other constellation shapes you can do; for example, some people prefer a triangle with dish antennas. But I only had OX-STAT panels at the time and wanted to minimize power usage, so I went with a solution that only uses a single antenna per craft. Even if the Communotron-32 isn't exactly frugal, it's still only a quarter as much as three dishes. And now that I have this geostationary network, I can just randomly throw future commsats into whatever orbit I wish, because any point in Kerbin orbit below (and a little above) geostationary is in range of a Communotron-32 at all times.

Edited December 3, 2014 by Streetwind
Typos

[HoY]

2 868.75 km

or, in meters, 2,868,750m

when your AP and PE are both at this altitude, switch your navball over to Surface and it will read 0.0m/s

[MarvinKitFox]

2 868.75 km

or, in meters, 2,868,750m

when your AP and PE are both at this altitude, switch your navball over to Surface and it will read 0.0m/s

If your orbit inclination is also exactly zero.

Even the smallest deviation causes a significant drift north-south, without in any way disqualifying your synchronous orbit.

Realistically... Just tweak your orbit until the period exactly matches one day, and the eccentricity and inclination aren't *too* wild. Period is all that really matters.

[WuphonsReach]

I'm starting a new game with Remote Tech + FAR + Deadly Reentry + Stage Recovery.

My method for Remote Tech is that I don't even consider starting my orbital constellation of communication relay satellites until I have 100k in the bank (and 150k would be better for tackling geosynchronous orbit).

Step #1 - LKO mesh network (700km altitude orbits)

Lightweight Stayputnik payloads with just the Comm-16 (2.5Mm range, omnidirectional) and DTS-10 (500km range) sats. A pair of Z-100 batteries mounted radially towards the bottom of the Stayputnik sphere provide plenty of reserve power for the dark period of the orbit. I put one inline reaction wheel, a T100 fuel tank and a LV-909 engine.

Around the top of the Stayputnik sphere I put three or four OX-STAT PV panels, tilted inward until they just barely touch at the top. That handles gathering power from the front. I also put 3-4 OX-STAT PV panels mounted on the LV-909 and angled to gather power from the rear. Another 2 or three OX-STAT PV panels can be put around the middle section to gather power from the sides.

Power demands with just the Comm-16 and DTS-10 is only 0.14/s. Very lightweight power draw.

I put my first (4) up at 700km altitude orbits. The goal is to get them spread evenly around the planet. Orbital period for these should be 1h20m. If they are spread properly, one or two will always be within range of KSC and they can relay to the others in the 700km orbit.

Payload cost should be around 5000-6000 per satellite. Launch cost is around 12-14k (and you get 2-5k back with the Stage Recovery mod). Figure 45-70k in funds to get those 3-5 satellites up and running in the 700km orbit.

If I have funds to waste then I might put 2-3 in polar orbits, also on a 1h20m orbital period. That gives a bit of redundancy in case the orbits drift out of alignment over time.

Step #2 - Geosync orbit (at 2868.75 km with a period of exactly 6h).

Satellites with the Comm-16 in the 700km orbit can reach Geosync orbit through about 30% of their orbit path. That means with 4 Comm-16 sats in 700km orbits that your KEO satellite over KSC will be controllable most of the time even if the DTS-M1 or KR-7 directionals are not yet connected or KSC is below the horizon.

My first two KEO satellite only have (2) DTS-M1 or KR-7 directional links. One for connecting back to KSC and one for connecting to the "active vessel". Because they can always see KSC once their orbits are stable, they do not need to link to each other via directionals.

I try to park them in KEO at about 30 degrees ahead of KSC and 30 degrees behind KSC on the equatorial orbit plane. They should be about 2.2Mm away from each other in a straight line so that the Comm-16 links them (as a backup plan).

Power requirements for the KEO sats is much higher. You need 1.78/s and the dark period of the orbit lasts for up to 20 minutes. That requires 2200 battery reserve power (which is a lot of Z-100 batteries). You will also need about 12-18 OX-STAT PV panels. Figure 1/4 of the panels facing forward, 1/4 facing towards the rear and the rest around the middle.

I'll have to play with this tonight to fine down the numbers on the KEO angles. You want them far enough apart that it is extremely rare that both will be eclipsed by Kerbin for any probe out past 2800km altitude above Kerbin. Probes inside of the 2800km boundary can be handled by the LKO mesh network using Comm-16s.

[Streetwind]

Regarding funds to pay for satellite constellations, there's a trick you can do right now with the Fine Print addon... meaning come 0.90, which looks to be hitting before the Christmas holidays, this trick will be stock:

Sometimes you get contracts to put satellites into specific orbits. The contract requires you to launch a new satellite for each contract, you can't just move an existing one to the requested orbit. The contract also stipulates the satellite must have a probe core and at least one antenna. If you now said "that sounds a lot like a commsat", then you would be right!

I launch almost all my commsats as part of a contract, meaning instead of spending money, I basically get paid to build the RemoteTech commsat network that I need anyway. The downside is that I need to wait for a contract that requests an orbit similar to the one I need (I have forbidden myself from declining contract offers to generate new ones because doing that results in multiple game-breaking exploits). It's part of the reason why I have zero LKO relays and just four geostationary commsats. I could launch more than that, but they would be on my own wallet, and I found it an interesting challenge to see how much I could do with just a small number anyway.

Just yesterday I launched a new commsat for a contract that requested a circular, equatorial orbit of the Mun. And in the screenshot in my previous post, you can already see the projected future orbit for the satellite that links said Munar satellite back to the geostationary network, in purple. I'll probably bring it back in a little closer again if I have dV left after completing the contract, though.

Edited December 4, 2014 by Streetwind

[WuphonsReach]

Yeah, the Fine Print contracts for sat-launches are extremely lucrative. That's how I manage to fund the experimental stuff in Career mode. Once every 2-3 kerbin days I will check for new orbit contracts.

From what I've seen, if you have multiple outstanding orbit contracts -- you can use a single satellite to service multiple contracts. Which makes it even more lucrative! (Probably a bit of an exploit -- and maybe it should be patched so that once you finalize an orbit contract you give up rights to controlling the satellite.)

I've settled on (4) equatorials at 700km and (2) polar orbits at 700km around Kerbin to form my "low-ish" network mesh with the Comm-16s (1h20m orbit period). Then I park (2) at geo-sync about 30 degrees ahead/behind of KSC's latitude. The geo-sync sats have (1) link back to KSC and (1) link to "active vessel".

And now I have (2) at the Mun in identical orbits but 180 degrees opposed to each other - they link back to the (2) geo-sync sats and provide omnidirectional control in the local Mun area. I had two orbit contracts to put sats around Mun.

Future probes to Mun will depend on linking back to my GEO-A and GEO-B sats over Kerbin, the (2) local relays around Mun will handle comms on the dark side of the Mun. It seems to be pretty efficient and effective.

The other trick that I'm using is that once a sat is in position, with the proper orbit inclination, eccentricity and orbital period - I rename it and classify it as "debris". That lets me hide it from map view.