Geostationary Orbit Over KSC

[Happybone]

Geostationary Orbit Over KSC

Greetings fellow Kerbonauts!! I have been playing the game for a little over a month now, and I absolutely LOVE IT!! I have been doing my best to try to not use MechJeb as much as possible. (just to see if I can, I have one install with it and one without.)

Here is my question: Try and try as much as I have, I cannot seem to find a way to put a communications satellite in a geostationary orbit above KSC. I know that the elevation is 2868.75, from watching videos on YouTube. (Scott Manley, etc.) But I cannot find a tutorial or even figure out for myself through many many attempts how to consistently put a satellite directly above KSC in a geostationary orbit.

If anyone out there could please help me out or at least point me in the right direction, I would be very grateful. Thanks so much for all of your assistance!

Happybone

Edited August 30, 2013 by Happybone

[Mr Shifty]

How directly above it do you need to be? You can launch straight up from KSC until your apoapsis is 2868 km, then coast to that point and circularize, but you'll end up slightly west of KSC's longitude because of Kerbin's spin. You'll still be more than close enough for comm satellite coverage though.

[Amoun]

Welcome to the Space Program!!

And welcome to the forum!

Hmmm

I would say trial and error.

You can have a lower orbit and go faster that the rotation of Kerbin and one you are over the KSC you can increase it. But then you would into the problem of having to time the Pe and Ap...hmmm.

This is where the math would get involved, and I won't lie, I will not be able to help you there, but I would at least try the actual run. I am sure you will be able to get right over it no problem, but getting is perfect might be a bit annoying.

[Happybone]

I guess I should clarify: I probably don't need to be directly over KSC, just enough that my satellite will always be getting a signal from KSC. I've attempted to go into orbit at around 100km on the exact opposite side from KSC and then do a burn so that my altitude above KSC will be 2868.75, BUT, by the time I get there to circularize, KSC has already rotated ahead of me.

What I think would be great to know is,: "where", (along the orbit), if you're at a 100km orbit, and did a prograde burn to raise your altitude to 2868.75km, would you end up over KSC. (Sorry if that is confusing....I had to re-write it a couple of times to make it as less-confusing as possible to ME. )

[Stone Blue]

Yeah, I've only been playing for a week or so, and I was able to get 4 satellites into geosync manually. Takes patience, but not that hard. I got one "relatively" over KSC....I couldnt get my orbit PERFECTLY circular at 2868.75....Best I can do is get a difference of around 40m between AP & PE, and 1 or 2 secs off 6hr orbital period, so my satellite has moved away from directly over KSC, but not by much. IIRC, I got the one satellite just a few degrees east of KSC, by eyeballing it. For a functioning relay system, you dont really need one to be directly over KSC....I would try to keep it 45° either side of KSC, but as long as it has a good LOS, your system will work.

And I couldnt get MechJeb to perfectly circularize it either...I actually got it closer than MechJeb could do, by doing it manually...WITHOUT doing ANY math...

Also, the other three are not spaced at the exact angles I wanted (ie 120° apart, with a 4th spare at 45° from the one directly over KSC), BUT I got them spaced so that every satellite has a direct LOS to the other three at all times....I figured good enough for a noob to be able to do in his 1st week of playing, especially all manually.

If I were to do it again, I would have used some of those 1.00 RCS linear motors to fine tune the orbit burns....I forget which motor I had on my satellites, but I think it had a power of at least 20, and with just a split-second burst, it was too much, causing me to not get closer than the 40m between AP & PE.

So it CAN be done pretty easily...just maybe not very prettily, or perfectly accurately...lol

Edited August 26, 2013 by Stone Blue

[RoboRay]

The key to geostationary orbits isn't altitude, it's the orbital period (or the orbit's semi-major axis, depending on how you want to look at).

A perfectly circular orbit at that altitude possess the proper period. However, creating a perfectly circular orbit simply isn't possible (and before somebody posts brag-shots of having it precise to the meter, you were off by centimeters that aren't displayed by the UI). And if you do get a really close one, once you timewarp it's going to change a little due to floating-point errors. Either way, it's not going to stay over the spot where you parked it.

You'll have a lot easier time if you install Kerbal Engineer or MechJeb (or some other mod that displays your detailed orbital parameters) and adjust your Ap/Pe to have exactly a six hour period.

It's ok if your Ap/Pe are a few kilometers above/below 2868.75km... your satellite will very slowly oscillate eastward and westward over the the same spot of the surface, by too small an amount to even be visible. Real geostationary satellites do the same thing, drifting back and forth across their designated "box" in the sky.

Edited August 26, 2013 by RoboRay

[Stone Blue]

I'll add that yes, I have MechJeb and Engineer Redux installed, and used their info displays, but I did all the actual flying manually, so again, it CAN be done pretty easily by someone who is pretty new to KSP.

[halbert5150]

The key to geostationary orbits isn't altitude, it's the orbital period (or the orbit's semi-major axis, depending on how you want to look at)...However, creating a perfectly circular orbit simply isn't possible...And if you do get a really close one, once you timewarp it's going to change a little due to floating-point errors.

This is exactly correct. I have spent many hours on this, got my pe and ap exactly right on, and the satalite still drifted away. I dont use mechjeb or any of the mods RoboRay suggested but I have an alternate fix. I put 4 satalites in geo S orbit all seperated by 90 degrees. They still drift but theres always one of the sats above the KSP. I do have to do some orbital maintenance now and then (to get them back to a 90deg separation) about once every ten years of gametime.

[Happybone]

Hey guys!!

Thanks everyone for all of the advice and help. Last night after many trials and errors I finally figured out the "sweet spot" to perform the burn at right after attaining a 100km orbit after launch. Essentially, if you set up the maneuver to go to 2868.75km just a tad to the west of KSC right after you circularize a 100km orbit, your geostationary orbit will be over KSC. My problem was....(and I feel like an idiot to admit this,)....I had not discovered how to "quicksave" and "quickrestore" in the game until last night, so it allowed me to do lots of trials and errors when previously, I was hitting ESC and reverting back to launch!! (I wasted so much time, sheeeeesh)

Anyways guys, I sincerely appreciate the input, and hopefully my trial and error and little discovery last night will help someone else out in the future if they have the same question I did. I really love this game and think that it attracts a pretty intelligent audience base by it's nature. And a really nice and sharing one too. Thanks again, folks.

Peace,

Happybone

Edited August 30, 2013 by Happybone

[tbarcello]

Yesterday I was researching this issue and came up with this solution. Although it's not for everyone, because not everyone are using the SCANsat mod, but if you are and you are reading this, just achieve any circular orbit and create apoapsis changing node. You then will be able to see the new apoapsis position on the big map of SCANsat. Then drag the maneuver node until it reaches desired position on the map. I placed my station over KSC this way yesterday. Easy and no calculations at all.

[PrathamK]

On 8/24/2015 at 10:24 AM, tbarcello said:

Yesterday I was researching this issue and came up with this solution. Although it's not for everyone, because not everyone are using the SCANsat mod, but if you are and you are reading this, just achieve any circular orbit and create apoapsis changing node. You then will be able to see the new apoapsis position on the big map of SCANsat. Then drag the maneuver node until it reaches desired position on the map. I placed my station over KSC this way yesterday. Easy and no calculations at all.

Love you my Boy, You gave the easiest solution of my Month long Problem. I use both KER/Mechjeb and SCANsat too. Plz give an detailed report.