Alright, back on this. This time, an old pain. So, rewinding to mid September, the launch of Soyuz MS-24 planted an idea which I've been avoiding thinking about too much until now so I didn't fall down the well, because the potential implications are interesting. Specifically, it was
this burn schedule:
Thing is, I think I had somewhat misunderstood the sequence of events, or never given it much thought, since what is documented is Kurs and what isn't Kurs is mostly lost in time, but looking at the 1999 -TM manual, it's all there. And it might have been dumb to overlook.
I had this idea that the Hohmann would put the Soyuz immediately in the vicinity of the station. In fact, SB1 and SB2 are the Hohmann transfer, first to raise to the ISS's orbit, second to circularise, Delta-V and timing make that clear. But then the docking isn't for over an hour later, with the ISS 96 km away at SB2. So the Hohmann puts Soyuz at roughly 100 km, and then it coasts for roughly half an orbit until it enters the vicinity of the station and starts the final approach with SB3.
Why am I rambling about this? Key thing is the starting point for the final approach has a low relative velocity (compared to the 55 m/s of SB2, or in Salyut's case, 30ish m/s), with the circularisation taking place much earlier and being the burn that actually puts it on an intercept course. Would it be reasonable to assume that Igla approaches used this kind of profile too? I haven't been able to find much data one way or the other, but also haven't had the time to really look yet.
But essentially,
the implication is: it might make my Igla implementation actually viable again. Because I was working on the potentially wrong assumption of a "straight in" approach with Igla handling 30+ m/s relative speeds, there was just too much energy for it to cancel while also controlling the approach and orientation. With a longer, slower, "shallower" approach, these are the conditions I was getting good results with in the beginning, before I started testing with Salyut at 350 km, or if one cancels the relative velocity manually a few km away, adds some speed towards the target, and activates Igla then.
So there are then two things need taken care of:
1 - need to scavenge for any historical rendezvous data that might exist. I know Chertok has some vague breadcrumbs, also wonder if Sven Grahn might have been able to get something. It feels too convenient regarding Igla, so I want to be as sure as I can. From what I've read at least, I've gotten the impression Igla was pretty sensitive to the starting conditions.
2 - if this is the way, well, there is a trade-off in flight complexity. Truth is I never got that technical with my Orbiter flying. So I'd have to figure out a proper procedure with the existing addon MFDs to set up such a trajectory, of which I only have limited experience with TransX (that was my attempt at a more professional version of the SyncMFD approach). Setting up a Hohmann transfer the end of which sets up the actual intercept, half an orbit later, in a reliable way, doesn't sound particularly out of reach, but I would be thankful for some starting pointers here, on which tool might be the best to accomplish this.