Launch for rendez vous from Woomerang launchpad

[kermand]

On my current campaign I decided to spice up things by restraining myself to launch only from Woomerang launch pad.

The main difficulty so far has been to rendez vous stuff in orbit. While it is trivial to do so from KSC on an equatorial orbit, the minimum inclination you can get from Woomerang is about 45 degrees, and if you don't time your launches carefully you can end up with up to 90 deg of relative inclination between the first and the second part of a station!

So my question is how to compute the optimal launch window to match a specific longitude of ascending node from Woomerang?

I tried launching always at the same hour of the day, but because sidereal day and solar day don't match, it works for quick succession of launches over a few days, but when trying to add a module to a station after a few months a I am out of luck. Noting the date and hour of the first launch and computing the new launch time from it works, but is too much bookkeeping.

Of course, I could eyeball it and correct inclination with a normal burn, but my shuttle replica's OMS does not have much delta V budget, and I'd rather launch on the correct orbit from the starters.

Edited May 29, 2019 by kermand

[bewing]

4 hours ago, kermand said:

Noting the date and hour of the first launch and computing the new launch time from it works, but is too much bookkeeping.

Of course, I could eyeball it

Those are your only two real choices.

[Adenosine Triphospate]

6 hours ago, kermand said:

I tried launching always at the same hour of the day, but because sidereal day and solar day don't match

True, Kerbin's orbit around Kerbol means that the launch time shifts slightly as the position around the sun changes, but the maths to figure it out isn't too hard, although, as you said, its still more than enough to put most people off (myself included) running the numbers.

Personally, I would just eyeball the exact moment it passes beneath the orbit (preferably in the day, not always possible) and launch, even if the target is in the completely wrong place. Once in orbit, I'd fiddle with /  and / if necessary, and rendezvous normally. The inaccuracies with eyeballing is pretty slim in this case (compared to interplanetary manoeuvres) and changing the inclination only really costs in the tens of m/s. My bad ascent profile wastes a lot more than that 

 

[SRB]

If you don’t mind mods, I’m pretty sure Mechjeb can launch to rendezvous with another craft

[cantab]

The launch time is easy. Launch when your launch site is underneath your target orbit. It's that simple. You can see this in the tracking station by angling the camera so your target orbit looks like a straight line through Kerbin.

The launch direction is a little trickier. If the target orbit is the minimum inclination for the launch site latitude - that's 45 degree inclined for Woomerang - then you launch due east. (Or due west if the target is retrograde). If the target orbit is a higher inclination you'll need to launch somewhat north or south. This may take some trial and error.