Bepicolombo ESA Mission - Moho Direct

[ryannathans]

Hey guys

Been trying for a few days to play the bepicolombo mission direct to Moho (no Eve flyby) and just can't seem to pull it off.

Has anyone managed to do this? A video of this mission would be awesome but all the youtubers seem to be going the Eve route.

I get stuck trying to get into the MMO deploy orbit, the little xenon engines take too long to burn retrograde and stabilize my orbit (did they remove physics warp? can't get that working anymore either).

[Lewie]

I feel your pain. I too have never attempted an Eve gravity assist. I’d recommend watching Scott Manley’s BepiColunbo mission, and try to replicate what he does. 

[ryannathans]

15 hours ago, Lewie said:

I feel your pain. I too have never attempted an Eve gravity assist. I’d recommend watching Scott Manley’s BepiColunbo mission, and try to replicate what he does. 

I found his video informative but unfortunately he does the Eve gravity assist. The mission provides the option to perform a direct transfer but I feel like it's not really possible at this point 

[theJesuit]

Sounds like a great challenge.

[Prof.hu]

I just discovered these missions, been trying to do the direct transfer for 2 days now. I only managed to get an orbit once, but when I tried to fix the inclination I screwed up, not aligned with the maneuver marker. By the time I noticed what's wrong, it was wasted again... Never got into orbit ever again. :( I can get a decent encounter, set up a maneuver at Pe to a seemingly fine orbit within the remaining deltaV of the transfer stages (5 to 3), but can't seem to find the correct time to start fireing, as it would be a 35 min burn, which always ends up wrong, running out in the end. DeltaV of the maneuver starts to increase after a while, since it takes so long, and the orbit changes slowly and gradually. It doesn't match with the planned maneuver anymore, I guess...

 

[Snark]

Moving to Gameplay Questions.

[Prof.hu]

After 3 days, I think I kind of have it. Making to LKO most efficiently is key, to preserve as much deltaV as possible. (My best attempt was 1837m/s remaining in stage 5.) After that a direct encounter at the AN needs to be set up, I did it in 2 steps. First roughly aimed as close and aligned below Moho as possible, then I did a fine tuning not much before leaving Kerbin's sphere of influence. Whit this I aimed to arrive exactly straight below MOHO with a PE of 300kms, so that no planar change would be required after arrival and a direct retrograde braking will not lead me closer than 190km (where the PE of MMO orbiter needs to be.) Once at Moho, I set up a maneuver for an AP of just around 9'000 km for reference, but just to see a rough estimate of deltaV and burn time. Initially it shows 35 mins. But instead of using the maneuver orientation, I do a full retrograde burn, starting early with at least 2-3 mins, so around 20 mins to PE. Stage 5 will burn out in seconds, and a second staging will be required somewhere along the way. Don't forget to open all the solar arrays, as the ion engine needs electric power to run. During the burn I constantly monitor the changing time to the new PE, and when it starts to match up with the remaining burn time, I decrease throttle to keep it just above. This needs to be adjusted from here on to the moment of getting an orbit. The goal is to get an orbit right at PE when the burn is done. Which will eventually happen only in the last moments of the burn and with very little deltaV in stage 3 remaining. Barely enough to bring down the craft to the MMO deployment orbit, but once that is detached, with the lower mass it will jump up so should still be enough to adjust for MPO orbit. Before staging to MSE, pay attention to solar array alignment of the MPO. First I managed to leave it blocked and when it run out of juice, communication to Kerbin stopped, leaving both MSE and MPO uncontrollable.