What are the small triangular fins on the lowest part of the boosters of the Soyuz 2.1 rocket? What function do they have?
I circled one of them in the upper image here. They are not visible in the lower image, which is a Soyuz launcher in transport almost a year later. Are these fins somehow attached or extended only after the rocket reaches the launch pad?
A frame I stole from this youtube clip A very beautiful filming of a Soyuz launch 28 April 2016!
A January 2017 photo I found on spaceflightnow.com. The "fins" are not visible there.