Good evening all, I've a simple (I think) question. I know that if you drop down around Kerbol then your hyperbolic velocity is greater than just burning straight out with the same amount of fuel. I also know that going faster at Periap produces greater velocity, which means dropping from a higher Apoap. So the farther out you go before you drop down, the faster you will exit.
However, at a certain point the benefits of dropping down towards Kerbol must be exceeded by the time you've spent traveling out to your Apoap. In an extreme case, if my target was 1,000,000,000 km out, and I rose to an Apoap of 500,000,000 km, it feels like I may as well have invested that energy in launching directly to the target rather than a sun-skim profile.
Is there an easy way to determine how far out to egress with a sun-skimming plan before it would just make more sense to launch straight out, or am I missing something basic?