Best Way To Match Plane From Pole

[Conbadicus]

Hello everyone, I landed at a pole by my orbiting fuel ship is orbiting on the equator, whats the best way of linking back up with it? I launched like, directly perpendicular then matched the plan when the orbits crossed path. But that took a lot of delta V.

Edited January 3, 2017 by Conbadicus

[klesh]

I am not a mathematics player, so there is probably a more efficient answer.  It sounds to me lkike you have the concept of what to do correct.  I would ask your altitude and speed that you performed the planechange at?  Do not try to planechange while trying to match orbits, rather perform your expensive planechange at a higher and slower altitude.  From there, a few small adjustment burns to circularize and or raise or lower your orbit to catch the fuel station.  If you're doing this at Kerbin, you can aerobrake to bring your newly raised AP back down, free of charge.

 

A planechange at the AP of a very eccentric suborbital trajectory is going to be alot cheaper than trying to do it at the altitude of the (presumably low)orbital station.

 

Make sense?

Edited January 3, 2017 by klesh
adding bit about aerobraking for free.

[something]

Well when going straight south (or north) and matching planes at the equator you have to kill all your southbound momentum and create eastbound momentum in order to orbit again. So for Kerbin at around 70-80km height that's about 4.4km/s dV plus 3.2km/s to get to orbit in the first place.

Not calculated this, but I would assume that if you continously changed your inclination while ascending that might save you some dV.

Alternatively,  go to a very eccentric orbit with Ap at the equator. Once there your momentum is minimal and you need way less dV to change the inclination (as your velocity is way lower as kinetic energy is converted to potential energy as you go 'up'). Thereafter you simply rendez vous. However, this needs additional dV to get into an eccentric orbit (and back again).

I am pretty sure this has been discussed before, somewhere on the board...

[klesh]

If my post wasn't clear, I'm talking about something's option #2.

[Conbadicus]

So basically you're saying to burn my AP way out above what my fuel ship is located at, because the speed there is much lower so i can change planes for less delta V? This is more fuel efficient that changing the plane at the target height? Hmmm  This around the mun btw at about 15-20km

[Dman979]

5 minutes ago, Conbadicus said:

So basically you're saying to burn my AP way out above what my fuel ship is located at, because the speed there is much lower so i can change planes for less delta V? This is more fuel efficient that changing the plane at the target height? Hmmm  This around the mun btw at about 15-20km

Yes, that's what they're saying. Your AP should be at least 13 times higher (IIRC) than your final AP for this to be most efficient. Then, after you plane change, you lower the AP at your PE.

[Conbadicus]

Just now, Dman979 said:

Yes, that's what they're saying. Your AP should be at least 13 times higher (IIRC) than your final AP for this to be most efficient. Then, after you plane change, you lower the AP at your PE.

Ok, Thanks!

[Dman979]

@Conbadicus- this guide explains the math for you.

 

Also, if you feel confident enough in your flying skills, try doing the plane change on a suborbital trajectory. But quicksave first!

[Sharpy]

If you're doing this around Mun, yes, that's your only really viable option. Other than driving to the equator on wheels

With bodies that have moons, the right gravity assist around given moon can allow you to change the plane practically arbitrarily - at cost of reaching that moon.

And with atmospheric bodies, if you have wings, you may be able to use them to change your plane by dipping into the atmosphere and turning like an airplane.

[klesh]

13 hours ago, Conbadicus said:

So basically you're saying to burn my AP way out above what my fuel ship is located at, because the speed there is much lower so i can change planes for less delta V? This is more fuel efficient that changing the plane at the target height? Hmmm  This around the mun btw at about 15-20km

 

 

Yup.  It's wild isn't it?  You'll see and get a feel for it when you do it.  Going so slow at such a high AP, you'll see your trajectory rotate sooo much faster when you planechange than back down low going fast.  It's an essential "ah hah!" lightbulb moment that will serve you will in your future advanced spacetravels.  Good luck!

[Kryxal]

Also, there's no need to lift your PE beyond the minimum safe altitude for your initial orbit.  The lower your starting orbit, the cheaper it is overall to get out to where you need to be to change planes cheaply.  It's the orbit after the plane change that should have a PE close to the target's, then a burn at PE to adjust the time of the next PE, and you're there!