Polar orbits

[crashy]

How would you reach a polar orbit using the least amount of Dv of other planets (i.g. Moho or Eve) from Kerbin to map the altimetry and biomes using SCANsat?

[KerikBalm]

by making a midcourse correction maneuver of a few m/s?

Entering a polar orbit of other bodies is just as easy as an equatorial orbit.

The only reason equatorial orbits are easier for kerbin, is that you can launch with the spin of the planet.

The ground velocity doesn't matter if you're not landing.

[Janos1986]

Change the inclination as soon as you get in the SoI of the planet you want to scan, and only then you burn retrograde (or aerobrake) to get into a stable orbit.

The farther from the body, the less dV you have to use to change the inclination.

[Snark]

Also, one little technique that I didn't discover until I'd been playing KSP for a month or two:

If you are already on an intercept course (that is, you're out in interplanetary space on your way, and you've adjusted your course so that it intercepts the target planet's SoI): Drop a maneuver node right in front of your craft, but leave it alone for now (i.e. at 0 dV). Then go to map view, click on the target planet, and choose "Focus View". It will now focus there and will render your trajectory relative to the planet, so you can see what your approach will look like.

Now, while focused on the planet, rotate the camera around so you can see the maneuver node you just dropped. You can see it an manipulate it, even though it's not in the SoI of the planet you're focused on. You can fiddle with the drag handles (very gently!) to adjust your periapsis around the planet so that it is over the N or S pole.

If you do it when you're still way out in interplanetary space, rather than waiting until you're in the target planet's SoI, you can generally accomplish what you need to do with only microscopic adjustments, like a couple of m/s.

[cicatrix]

Technically, you can adjust the interplanetary burn (or mid-course correction burn) in such a way that your injection trajectory will be close to 90 degree inclination. I did that a couple of times with MJ (maneuver node editor - conics mode 0). I doubt it is doable with stock maneuver node handlers.

Nevertheless the general rule is - the farther you are from the target body, the cheaper will be the inclination change maneuver. Generally, you can correct your trajectory as soon as you enter the target's SOI. It will usually cost only a few m/s of dV.

[Murph]

Personally, unless fuel is really tight, I wait until the target SoI to pick orbit, making the adjustment immediately after entering the SoI. Tiny burns from a very long way away can be an exercise in frustration, as they require extreme precision in both the burn vector and duration. That said, if you need 0.1 m/s precision on a very small burn, my tip of the day is to temporarily set your thrust limiter to 5% for the burn, effectively giving you 20x the precision and subtlety on your throttle (assuming that 100% thrust is a moderate to high TWR).

[Warzouz]

As others I usually use Precise Node Editor (dedicated mod of MJ's one) and focus on the body. I usually do that to get a better equatorial orbit, but polar are the same.

Of course, if you can't do that way, the farther you are from the body the lower the dV requirement of changing to polar orbit. So capture on a very elongated elipse an change inclination at apoapsis.

But mid course interplanetary tweaks are much cheaper.

[RocketPropelledGiraffe]

Personally, unless fuel is really tight, I wait until the target SoI to pick orbit, making the adjustment immediately after entering the SoI. Tiny burns from a very long way away can be an exercise in frustration, as they require extreme precision in both the burn vector and duration. That said, if you need 0.1 m/s precision on a very small burn, my tip of the day is to temporarily set your thrust limiter to 5% for the burn, effectively giving you 20x the precision and subtlety on your throttle (assuming that 100% thrust is a moderate to high TWR).

This is good advice for most small craft with relatively high TWR.

I find that making the precision adjustments with RCS thrusters comes in very handy, if your craft has RCS. You can do very precise maneuvering and if you overshoot the maneuver you can just thrust retrograde to correct the error.

That way there is no need to change the craft attitude for a correction.

[Warzouz]

I remember that I made a plane inclination change around Laythe with RCS. Not because it was effcient, but becaus I had no fuel left to go back to the refueling station.

Hopfully I had a tug to get the ship back

RCS can have quite a lot dV, even for small tank. (I had a 250 unit tank for a 15T lander)

[ratchet freak]

Technically, you can adjust the interplanetary burn (or mid-course correction burn) in such a way that your injection trajectory will be close to 90 degree inclination. I did that a couple of times with MJ (maneuver node editor - conics mode 0). I doubt it is doable with stock maneuver node handlers.

Nevertheless the general rule is - the farther you are from the target body, the cheaper will be the inclination change maneuver. Generally, you can correct your trajectory as soon as you enter the target's SOI. It will usually cost only a few m/s of dV.

You can adjust your final inclination during the first ejection burn by adjusting up/down a bit.

However it's simpler to use the mid-transfer correction burn for that, just add a bit of (anti-)normal dV until you inject above/below the target instead of in front/behind

[RocketPropelledGiraffe]

I remember that I made a plane inclination change around Laythe with RCS. Not because it was effcient, but becaus I had no fuel left to go back to the refueling station.

Well, doing inclination changes when you are already around the planet is never efficient anyway - well, I guess RCS is still a lot better than getting out to push...

If you are in the Jool system you can actually perform your inclination changes in a quite more spectacular way ( https://xkcd.com/1244/ ), if you like precision maneuvering and multiple gravity assists. Shooting around Tylo and Jool to get your inclined orbit around Laythe is really satisfying...

Edited May 18, 2015 by RocketPropelledGiraffe
inserted quote for reference