I built a 3 umbrellas. They could not do anything to bring down. They are a very long shot by hovering over my base orbital planes, and do not break any of them.
Yes I believe there are some flawed mechanics there. I have seen it shoot stuff down but not very often and only sats and solar and one of my lasers
Umbrella is essential, last night I had most of a planet under my control when a damn laser floats over and takes out all of my planned umbrella sites, my orbital launcher and then it focused on my energy production. The worst thing about it was that some creep on the internet was getting a kick out of it
Right now umbrellas are gliyhcy and or broken. They aren't very reliable. Catapults on the other hand have an exploit where they can hit orbital above them. I suggest using this untill umbrellas are fixed.