>>1592976I was thinking it over and they probably just need 2 half rings that can be moved together around the core once the engines have descended past that point. That would also give them the option to swing the complicated expensive bits out of the way if the booster ends up having an engine failure and is coming in too hot in the last seconds. The arms the half-rings are attached to would need to be able to move the ring in the horizontal plane several meters (probably the ability to tilt a few degress as well) to keep the booster centered until it makes contact.
It will be a huge structure but that kind of tracking should be fairly straight forward.
