ArchangelGabriel

I didn't have time to take screenshots, but it appeared that the BACC boosters were "overlapping" the central booster physically. I put some Modular Girder Segments in the same radial patter, and put the decouplers on those, then attached the BACCs to the decouplers in the same fashion. (I have had trouble in the past with alignment, so I knew it wasn't a matter of "missing the decouplers". I was super careful, and put a lot of slow effort into making sure the staging and alignment of the decouplers was right. It turns out the Girders put enough distance between the BACCs and the main booster that the decouplers worked. I got a big Career mode boost from testing the S1 SRB-KD25k at altitude. Thanks for the suggestions!

I'm sure there's an interface issue I don't understand, but I have tried a number of times to put several BACC boosters in a radially symmetrical configuration around my lift vehicle with radial decouplers intended to set them loose when they're used. So far I have found no way to make this work reliably. It appears to be random whether the decouplers shove the BACC away at all, and about 10% of the time. I've even had symmetrical boosters let go of one but not the other. Is there some construction interface trick I need to be aware of?

I can't find a reference that explains this (though that's likely because I don't know where to look). When attempting my first orbital launch I cannot select my Periapsis or Apoapsis points, and my orbit is gray in the map view. I'm unable to create Maneuver Nodes as a result. Is it because I have not yet unlocked relevant technology in Career mode, or because my Kerbal pilot has not yet reached level 1? Or is it some other arcane sorcery I have yet to suss out?