How to Change orbital inclination during launch

[GungaDin]

I've become a damn pro at rendezvous and docking but I'm still wasting lots of precious fuel by launching from my base which is about 13 latitude.  I always end up with an inclination of about 13 and then have to spill gas to get closer to 0.  is there an efficient way to get to an equatorial orbit from a higher latitude?

[bewing]

Nope.

You either fly down to the equator and turn left, or you get to orbit and then do a plane change there, or you use a gravity maneuver around the Mun.

The key to the first two, of course, is that you want to be going as slow as possible when you change planes. Which may mean being suborbital at the time, or it may mean being at your Ap in an extremely high orbit.

 

[pincushionman]

If you can do part of it during your circularization burn that can help too, but that will only work if your initial Ap is at the equator. I haven’t paid much attention to where my launch Ap are before, so I can’t comment to whether that’s easy or efficient.

[GungaDin]

Thanks to both of you.  I'm learning these maneuvers mostly by instinct and I've always been very good at visual leaning which is also important when you are math deficient like me.   These are good points.  I did not know the 'slow' principle. 

I have figured out to do my burn at descending or ascending nodes but I suppose that I may have chosen the wrong node at times if I was not in circular orbit.  Ah!  So for me - sitting in a 13  dig inclination - I wonder if it would help for me to do my inclination burn BEFORE I circularize my orbit?  In the past I would circularize first for simplicity sake and that may be a mistake.  Where's Scott manly when you need him?

[paul23]

1 hour ago, GungaDin said:

Thanks to both of you.  I'm learning these maneuvers mostly by instinct and I've always been very good at visual leaning which is also important when you are math deficient like me.   These are good points.  I did not know the 'slow' principle. 

I have figured out to do my burn at descending or ascending nodes but I suppose that I may have chosen the wrong node at times if I was not in circular orbit.  Ah!  So for me - sitting in a 13  dig inclination - I wonder if it would help for me to do my inclination burn BEFORE I circularize my orbit?  In the past I would circularize first for simplicity sake and that may be a mistake.  Where's Scott manly when you need him?

To be frank "I wouldn't bother".

 

The only thing you might wish to do is "fix inclination during circulization", only if you're near the ascending/descending node though, if you combine multiple maneuvers like this you get at most 30% saving, so if the ascending node is like 2-3 degrees off the apoapsis, you might make a maneuver node that has both circulization and a "fix" up to ~5 degrees inclination.

 

But that would require lot of tweaking of the node to see how you have to fire.

[The Aziz]

Yeah, doing inclination change during circularization burn at AP over the equator is the best solution, I've done that several times. 

You could also try slight turning on the way to AP (what I mean is, fly on a curve from the launchpad to the equator) but I doubt that's gonna save much fuel.

[Superfluous J]

13 degrees isn't that bad, but if it was much more than that I'd consider doing what we humans do: put the station on a tilted orbit and only launch when you're under that orbit.

[GungaDin]

1 hour ago, 5thHorseman said:

13 degrees isn't that bad, but if it was much more than that I'd consider doing what we humans do: put the station on a tilted orbit and only launch when you're under that orbit.

I've been doing that but my concern is that once I refuel at my depot I will have to adjust to 0 before I head off to Moon or Mars.  I guess that's still more efficient then dragging all of that fuel up from earth.

[paul23]

1 hour ago, GungaDin said:

I've been doing that but my concern is that once I refuel at my depot I will have to adjust to 0 before I head off to Moon or Mars.  I guess that's still more efficient then dragging all of that fuel up from earth.

You don't have to get to 0 degrees when doing a burn. The sphere of influence is bigger than a point, and for transfers to another planet: it really doesn't matter, and you'll just fix it "mid way" in the solar soi.