Help with a KEO Satellite Constellation

[RangerDanger75]

I have a question about satellite constellations, particularly a KEO constellation like this one (starts at 3:44)

How do you go about setting up a constellation like this, specifically in KSP? Waiting any amount of time between launches is useless because it doesn\'t matter when you launch into KEO, your satellite will always end up in the same place. This is because once the satellite reaches KEO, it stays in the same spot in the sky relative to Kerbin.

The best ideas I can come up with are to send up all my satellites into a KEO where they all hang out in the same general location. Then send one high, one low and wait while they slowly move to the location in KEO that I want.

My other idea was to put three into a LKO, all evenly space apart, and then send them up into KEO one at a time and hope the spacing keeps on the way up. The only problem with this is that I would need all the satellites to do their trans-KEO injection burns all at the same time.

Any ideas on how best to do this?

[BillWiskins]

I do not have any idea how to help you. However, there is a user on these here boards who might - I think his name is Cezary, and I\'ve seen some very impressive satellitery from him.

[Kosmo-not]

You could send them up into KEO, and then adjust them from there by calculating the time difference between its current position and the position you want it at, and then put it into an elliptical orbit that will accomplish the time difference.

[Cezary]

Ok, tough question. You want 3 satellites in geosynchronous orbit, 120 degrees apart, on one orbital plane. Sounds simple enough. You make a good point in that the satellites would end up in the same place, since they would launch from the same place and end up geosynchronous (assuming 3 IDENTICAL launches).

First things first, I need to watch that part about the Iridium Satellite Network @ 3:11 again. Whew, that\'s gonna be my next project. Now, back to your question. I crunched the numbers, compared using Hohmann and Bi-elliptic transfers, and came up with a few solutions you could use.

1. Use lower orbits first, then calculate the transfer time to line up your satellites

Example:

• 
  [li]LEO @ 150 km (orbital period 00:36:12)[/li]
  [li]Transfer 150 km -> 2,868.4 km (transfer time 01:25:22)[/li]
  [li]KEO @ 2,868.4 km (orbital period 06:00:00)[/li]
  

You begin your burn on the opposite side of Kerbin (180 degrees from the target point) @ 150km at the exact moment that your destination is 85.37 degrees away from the target point. Both you and your destination will arrive at the target point at the same time and @ 2,868.4 km. You only need to burn again to circularize your orbit. You can find your target point when your first geosynchronous satellite is 120 + 85.37 - 180 = 25.37 degrees behind you. This may sound impossible to do by eye or without mods and plugins, but the stock game has something that can help you time this perfectly. The Mission Elapsed Time (MET) visible in the Tracking Station can help you calculate the angle of the satellite it belongs to. 360 degrees around takes exactly 360 minutes when in geosynchronous orbit.

2. Line up all 3 satellites in LEO, 120 degrees apart, and send them all to KEO at the same time*

^{(*) technically impossible**}

^{(**) nothing is impossible}

Setup:

• 
  [li]Launch Satellite One to 150 km orbit, time warp until MET is 00:12:04[/li]
  [li]Launch Satellite Two to 150 km orbit, time warp until MET is 00:12:04[/li]
  [li]Launch Satellite Three to 150 km orbit, check the Tracking Station to verify timing and position[/li]
  

Now the perfect solution would be to do a Hohmann transfer with all three satellites AT THE SAME TIME to 2,868.4 km and they would remain at exactly 120 degrees apart. Then do a second burn, again simultaneously, to circularize all three orbits. So how do you do it? Could you burn REALLY quickly, one satellite after another (trading accuracy for speed) and hope they end up close enough? Perhaps. Could you do minor burns with each satellite, cycling through all of them numerous times, pushing the apoapsis further and further until all three are at 2,868.4 km? More precise, for sure. Technically if you do it slowly enough, the time it takes to switch between ships becomes less and less of an issue. The only downside is that it\'s tedious and will take time***. Oh yeah, and you have to do it again once near apoapsis to bring the periapsis to 2,868.4 km just as accurately.

^{***Tediousness and large time requirements are EXACTLY why I play KSP}

3. Do a crap-load of math and use your imagination to find other ways

There are countless ways to do this. You can use orbits that are slightly too high or too low and wait until the positions align. You could build ONE ship, with 3 satellites, and decouple them at each place after changing orbits and positions 3 times. It\'s up to you. All I ask is that you take screen shots and post your adventures for all to see.

[RangerDanger75]

Thanks for the quick reply Cezary, informative and witty. I like your style 8)

I digress,

I figured out a relatively simply way to get this KEO satellite constellation to work, provided you have the MechJeb plugin.

Here\'s my plan:

[list type=decimal]

[li] Send 3 Kerbs up into LKO and achieve a stable orbit [/li]

[li] Burn into a KEO, record the longitude of the craft at the start of the burn[/li]

[li] Record the longitude once the craft reaches apoapsis and begins the circularization burn[/li]

[li] Find the change in longitude using Delta-longitude = Longitude_Final - Longitude_Initial[/li]

[li] Send the boys back home and begin launching satellites into the 80km LKO[/li]

[li] Using Delta-Longitude as a guide, sharp shoot satellites into desired KSO positions[/li]

I\'ll post pics if the operation is successful

[Cezary]

I\'ll post pics if the operation is successful

You mean like this...?

[Kryten]

...how long did that take you to do?

[RangerDanger75]

Lol precisely like that, I am but a lowly noob

[Cezary]

I was tempted to use AR202 or another plugin, but those babies are manual control. Not super hard either;

[list type=decimal]

[li]LEO @ 2,300 km[/li]

[li]Wait until lined up[/li]

[li]Bump up to 2,868.4 km[/li]

Oh, and Kryten... if you\'re interested in how to make complex satellite networks, my blog link is in my signature. Toodles

[Cezary]

...and I even designed the Geo-Sat ships to drop spent stages with parachutes and into the ocean. I love this game ;P

[RangerDanger75]

Do the spent stages explode when they hit the ground? My experience has always been that one parachute isn\'t enough to keep them from having a rough landing.

Well even though Cezary upstage me (darn you!), I\'ll still post my constellation of four KSO satellites. I went with four because I wanted a spare, redundant satellite and it also provides overlapping coverage which is bueno.

Slideshow time!

Here\'s the tracking station view. The naming convention I used was

• 
  [li]comsat - for the

satellite plugin)[/li]
[li]KSO - KerboStationary Orbit[/li]
[li] 27 - approximate longitude of KSC, which is what I based much of my 4 flight plans off of[/li]
[li] + or - 0/90/180 - this was the position of the satellite in KSO with respect to KSC\'s longitude[/li]

The craft that brought the satellite\'s into orbit. It carries just enough fuel to deorbit once it reaches a stable KSO. You can see MechJeb on the capsule as well as AR202 on the side. Automating most of the flight was much more manageable. (I don\'t know how you do it Cezary ???)

comsat_KSO_27+0; Longitude 27.473320 directly over KSC

comsat_KSO_27+90; Longitude 117.654174 90 degrees positive from KSC

comsat_KSO_27-180; Longitude -152.420671 180 degrees from KSC

comsat_KSO_27-90; Longitude 60.669580 90 degrees negative from KSC, also the on that is furthest away from where I wanted it by a whole 2 degrees

[Cezary]

Do the spent stages explode when they hit the ground? My experience has always been that one parachute isn\'t enough to keep them from having a rough landing.

Fantastic job!!! That looks amazing, congrats.

In regard to the spent stages, they do explode upon terrain impact as the parachute only slows them to about 20m/s, which is way too fast. I plot my course and design my ship so that the spent stages will end up over water. This gives me a more real-life feel to managing spent stages, even though they still splash-down too hard. I don\'t want to use mods for now, and the stock parts don\'t allow enough parachute placement to do the job.