Inverting orbit direction to rescue Karen

[Nookos]

Hi,

I m having some issues to rescue Karen. She got herself in a clockwise orbit around Duna. And I didn t realise her direction until I was parked in low orbit around Duna. In the right direction of course. On that subject I think it would be unbelievably helpful to get the direction of an orbit like we get with satellite mission. I had a quick look and couldn t find a mod that does that. Is there one? The only way I know to find out the direction of an object is to time warp..

So here is the situation:

As you can see brutally inverting my orbit will cost me more than 1758m/s.

And the best I could do so far is this:

This adds up to 792m/s if it goes according to plan.. which is unlikely. Then I ll spend some more DeltaV to rendezvous and the way back. With only 1459m/s on that ship I don't think I can come back to dock in low duna orbit after rescue.

Is there a more efficient way to turn around?

Is there something to transform all orbits in map view into satellite mission orbit display ( simply showing those little dots travelling in the direction of the object).

Thanks for the help.

Edited May 27, 2015 by Nookos

[Mighty1]

Well, you could try to get out and push. You have an unlimited amount of delta-v if you do that. Other than that you could send a rescue for the two of them

[mhoram]

One other way would be the following:

- Rise your Apoapsis to nearly Dunas SOI

- At apoapsis change your direction so that it matches Karen's

- Rise your Periapsis to match Karen's orbit

- Fiddle around to get an encounter with Karen.

Can't tell you the exact amount of dV needed, but changing your plane is always more efficient the farther away from the Planet you are. And Using Ike for a gravity assist to rise your apoapsis is also an idea to reduce the total amount of dV needed.

Also your red maneuver node is located very inefficient. Try to burn only at periapsis or apoapsis.

Edited May 27, 2015 by mhoram

[cybersol]

Karen is pretty far out, so she should be going relatively slow (check with mouse hover). Once out there, it will only cost you twice her velocity in dV to completely flip orbits by burning straight through retrograde. Alternatively, because she is going so slow, you can set up the rendezvous while still in opposite orbits and potentially use the awesome power of her EVA jet pack to switch directions instead.

[monophonic]

Is refueling before rescue an option?

Could you manage multiple Ike gravity assits? At least one on the way up and one on the way down should be possible.

Best place to reverse direction is as high as possible, as there your orbital speed is at the minimum. Place your reverse burn at the apoapsis after Ike gravity assist, not as soon as you leave its SOI. Does Ike reverse your orbital direction on that plan? If not, you are passing it on the wrong side. Use Ike to get your apoapsis as high as possible and reverse there with the lesser cost. Using Ike for raising Ap might cost less even if Ike could reverse you if you can get much higher than you would get after an Ike reversal.

[Nookos]

Well, you could try to get out and push. You have an unlimited amount of delta-v if you do that. Other than that you could send a rescue for the two of them

I like the get out and push solution

One other way would be the following:

- Rise your Apoapsis to nearly Dunas SOI

- At apoapsis change your direction so that it matches Karen's

- Rise your Periapsis to match Karen's orbit

- Fiddle around to get an encounter with Karen.

Can't tell you the exact amount of dV needed, but changing your plane is always more efficient the farther away from the Planet you are. And Using Ike for a gravity assist to rise your apoapsis is also an idea to reduce the total amount of dV needed.

Also your red maneuver node is located very inefficient. Try to burn only at periapsis or apoapsis.

Wow. Much much better.

This should be only 474m/s one way and the way back will be cheaper I guess. So thanks a lot you just saved Karen's life.

By optimizing my previous maneuver I didn t get much further. From 792 to 718m/s. Thanks again.

Karen is pretty far out, so she should be going relatively slow (check with mouse hover). Once out there, it will only cost you twice her velocity in dV to completely flip orbits by burning straight through retrograde. Alternatively, because she is going so slow, you can set up the rendezvous while still in opposite orbits and potentially use the awesome power of her EVA jet pack to switch directions instead.

Indeed I could probably afford to the invertion at her altitude seeing how much it got cheaper upthere. No clue why I didn t think of that. Thanks

Is refueling before rescue an option?

Could you manage multiple Ike gravity assits? At least one on the way up and one on the way down should be possible.

Best place to reverse direction is as high as possible, as there your orbital speed is at the minimum. Place your reverse burn at the apoapsis after Ike gravity assist, not as soon as you leave its SOI. Does Ike reverse your orbital direction on that plan? If not, you are passing it on the wrong side. Use Ike to get your apoapsis as high as possible and reverse there with the lesser cost. Using Ike for raising Ap might cost less even if Ike could reverse you if you can get much higher than you would get after an Ike reversal.

My ship is already full. It just undocked from the station. I could probably detach a tank from the station and attach it to the rescue ship thanks to KIS but no need now. I m gonna try and see if I can use Ike to raise Ap as you suggest. I didn t think of that either. Thanks

Thanks everybody

Edited May 27, 2015 by Nookos

[Murph]

You could also possibly take some of Ike's free supply of dV to reduce the cost of braking to 0 before accelerating in the opposite direction.

http://wiki.kerbalspaceprogram.com/wiki/Tutorial:_Gravity_Assist

Not sure that would really be worth it; raising Ap to quite high and reversing orbit there is simpler, and you can actually use the high Ap as part of your orbit phase matching for the rendezvous.

[heng]

Grats for saving her!

Could you in theory use Ike to do the inclination reversal for even less?

i.e. coming in from Duna orbit to encounter Ike just barely (AP just touching into Ike's SOI), would give you a free polar direction for Ike. Doing a tiny change to flip the inclination shouldn't cost much, and then leaving Ike you would basically have reverted your orbit? maybe not a full 180° but at least 120°?

Just speculating here... any people who know if that works? can't try right now...