[1.11.1] Move three relays from Eve to form CommNet

[Kinniken]

Hi,

I currently have three satellites in Eve orbit which I would like to move so that they form a 4-body constellation in solar orbit, Eve itself being one of the four bodies, in order to make a deep space comm relay (I already have three of them in low Eve orbit, hence Eve counting as a "satellite" for this purpose). My three satellites have around 1700 dv and a 100G relay antenna. Small graph of the final state I'm looking for:

Any tips on how to move them to destination? I saw an online calculator for resonant orbits but it works if you are launching from the body you'll be orbiting around. The general principle I'm assuming will be to move the satellites to elliptical orbits with Eve's orbit as either the Pe or the Ap, then recircularise when they are at the right position compared to Eve. Presumably the satellite that would be ahead of Eve (P1 in the graph) would have a transfer orbit with a lower Pe in order to move ahead of Eve, the satellite that would be behind (P3) an orbit with a higher Ap, and the one going to the other side (P2) could use either method. But is there any reasonably simple way of calculating all that?

Thanks !

Edited February 12, 2021 by Kinniken

[paul_c]

Very muddled, you mean Solar orbit not Eve orbit for the satellites I think? But you wrote Eve. And then you said its actually at Gilly.

I still don't know what you mean after reading it several times, sorry. If I knew what you meant, I would try and help.

[bewing]

Well, if you look up "keplerian orbital parameters" on wikipedia, for example, it gives the formulas on how to calculate period based on things like your orbit's SMA (semi-major axis). Then you choose a number for how many orbits (years) you want it to take for you to get there. Then you decide whether you want to raise your Ap to slow your orbit down, or lower your Pe to speed your orbit up (generally, raising your Ap for a slower orbit works better).

Or, you can just do it the really easy way. You want to circularize the P3 satellite in 1.25 Eve years, the P2 satellite in 1.5 Eve years, and the P1 satellite in 1.75 years -- all at your current location. So you send them a bit outside of Eve's SOI, turn prograde, and burn until the Pe marker shows you returning to your Pe in the proper number of days. Then circularize when you get there.

Edited February 15, 2021 by bewing

[Kinniken]

37 minutes ago, paul_c said:

Very muddled, you mean Solar orbit not Eve orbit for the satellites I think? But you wrote Eve. And then you said its actually at Gilly.

I still don't know what you mean after reading it several times, sorry. If I knew what you meant, I would try and help.

Indeed... I messed up my terms. I meant "solar orbit at Eve's altitude". I fixed the post. And indeed my satellites are actually orbiting Gilly not Eve itself but that was not relevant. I fixed my OP.

[Kinniken]

2 minutes ago, bewing said:

Well, if you look up "keplerian orbital parameters" on wikipedia, for example, it gives the formulas on how to calculate period based on things like your orbit's SMA (semi-major axis). Then you choose a number for how many orbits (years) you want it to take for you to get there. Then you decide whether you want to raise your Ap to slow your orbit down, or lower your Pe to raise your orbit up (generally, raising works better).

Or, you can just do it the really easy way. You want to circularize the P3 satellite in 1.25 Eve years, the P2 satellite in 1.5 Eve years, and the P1 satellite in 1.75 years -- all at your current location. So you send them a bit outside of Eve's SOI, turn prograde, and burn until the Pe marker shows you returning to your Pe in the proper number of days. Then circularize when you get there.

Thanks! That last part is the kind of solution I was looking for. Makes perfect sense to do it this way.

[paul_c]

43 minutes ago, bewing said:

Well, if you look up "keplerian orbital parameters" on wikipedia, for example, it gives the formulas on how to calculate period based on things like your orbit's SMA (semi-major axis). Then you choose a number for how many orbits (years) you want it to take for you to get there. Then you decide whether you want to raise your Ap to slow your orbit down, or lower your Pe to raise your orbit up (generally, raising works better).

Or, you can just do it the really easy way. You want to circularize the P3 satellite in 1.25 Eve years, the P2 satellite in 1.5 Eve years, and the P1 satellite in 1.75 years -- all at your current location. So you send them a bit outside of Eve's SOI, turn prograde, and burn until the Pe marker shows you returning to your Pe in the proper number of days. Then circularize when you get there.

Agree, that's the best way - just burn and watch the "orbital period" parameter, get it to the relevant figures and they'll be in the right place in one(-of-their) orbit.

[Spricigo]

Since the Resonant Orbit Calculator was mentioned I'd like to point out that just needed to select Kerbol as parent body and Eve orbital height.

In any case, as already explained, you just send the satellites in a higher orbit so when they come back they will be behind Eve the required angle and then circularize. If deltaV is a concern(don't seems to be the case to me), you may save some going for several 'falling behind' orbits before circularization.

On 2/12/2021 at 7:21 PM, bewing said:

Or, you can just do it the really easy way. You want to circularize the P3 satellite in 1.25 Eve years, the P2 satellite in 1.5 Eve years, and the P1 satellite in 1.75 years -- all at your current location. So you send them a bit outside of Eve's SOI, turn prograde, and burn until the Pe marker shows you returning to your Pe in the proper number of days. Then circularize when you get there.

Alternatively, send a satellite now, another in 0.25 Eve years and the last one in 0.50 Eve year.

 

[Kinniken]

Thanks all, I've launched my relays (two of them, the third had an "accident"). Turns out that with 1700 dv I had to use the same orbit for both, a 3:4 resonant orbit, so the second satellite will take 2.66 eve years to get in position. Positioning it by putting it on a faster orbit required an insane amount of dv.  I also could have speed things a little by launching it 0.66 eve year later, but I wanted this done with to move to other things.

[Spricigo]

If you don't mind, I'm curious about something: why Eve? Doing that Kerbin orbital height seems like a more natural idea for me.

 

On 2/14/2021 at 10:50 AM, Kinniken said:

Positioning it by putting it on a faster orbit required an insane amount of dv.

It seems you already managed to solve your problem, so that is probably not important anymore in your case but for the sake of completeness(someone else may stumble in that thread with a similar problem):

If time is not an issue, you can just put the satellite in a orbit slight higher than Eve's orbit,  let the satellite stay in that orbit as long as necessary (can be several years) for the satellite get in position and then lower your orbit. The important point is that the final orbit need to have the same orbital period of Eve.

What @bewing describes above is the particular case where one have plenty of deltaV and want to get it done in the least amount of time. If you can, go for it, otherwise just trade time for the deltaV.

[Kinniken]

@Spricigo this was not the original plan. I had sent a mission to Eve with six detachable relays, thinking I'd put three around Eve and three around Gilly. Ultimately the Gilly ones were not really needed, so I repurposed them as deep space relays. Otherwise at Kerbin level I have two relays on 60M polar orbits around Kerbin, with 120 100G antennas each, to ensure good-quality connections to pretty much anywhere.

I know I could have done what you suggested for the relay, but I wanted it done fast. And two orbits at 3:4 was faster than any "faster" orbit I could afford.