Intercept when inclination is off

[TanDeeJay]

I took off from the Mun in my ascent stage and by the time I reached orbit, the inclination of my ascent stage was 5 degrees off my orbitor. I've found there are 2 ways you can intercept in this scenario, you can do a burn to adjust your inclination to match what your trying to dock with and then do an intercept burn, or you can wait several orbits until you can get an intercept directly at the AN/DN, which was the way I did it this time. The distance at Intercept was just under 5k so not the closest I've ever done, but I successfully intercepted and docked.

But it got me thinking, which method (apart from launching directly into the correct orbit) is more fuel efficient? Adjusting the inclination to match the target vessel 1st or the direct intercept? Assuming your inclination is off by no more than 5 degrees.

Cheers

John

[bewing]

Well, theoretically you always end up having to do both. That is, by the time you dock vessel 2 to vessel 1 -- vessel 2 has to be in exactly the same orbit as vessel 1, and they have to be at the same location. Which means you had to do both an inclination change, and a rendezvous maneuver. But often, combining two maneuvers so that you do them both at the same time can save you a little bit. On the other hand, the way most people do inclination changes is slightly inefficient -- so to some extent it depends on your piloting skills. But my guess is that most pilots would save at least 0.7 m/s of dV by doing a careful high-speed direct intercept.

[TanDeeJay]

The ship I was flying was my fuel transporter, transporting fuel to a science ship waiting to transfer to minimus. After refueling, and returning the fuel transporter back to the surface of the mun,  I landed with 11m/s dv to spare. So my direct intercept might have (but not necessarily) saved my bacon

 

cheers,

John