English to Portuguese Tech/Engineering Astronomy & Space NASA

https://www.reddit.com/r/space/comments/50xgo0/apollo_11_at_...


You can also see that the S-II's interstage skirt is still attached (it's the black and white striped bit at the very very bottom of the S-II). The skirt is a structural component that transmitted the thrust from the S-IC up to the rest of the rocket, and it gets dropped in a separate operation a few seconds after the S-II's J-2 engines start firing. You can see the skirt separation in this video from the unmanned Apollo 4 launch.
That skirt separation video shows the famous "blowtorch" effect as the skirt falls away. This used to always really confuse the hell out of me, since I could never figure out why the skirt seemed to be "burning" as it tumbled. The reason for the "burning" effect, of course, is that the J-2 engines' thrust is mostly invisible, since the engines burn liquid hydrogen and liquid oxygen (the S-IC's F-1 engines burned RP-1—kerosene—and LOX, leading to a much more visible sooty orange thrust cone). The skirt flares with fire when it impinges the J-2s' invisible thrust cones.