When I first saw one in a static display, they had black painted plywood sheets over the exhaust. Armed guards and roped off too.
Kind of a side note but the last year they were at Holloman I got to take a tour of the ‘test cells’ where they work on the engines. Being a gearhead it was like going to Nirvana.
Imagine ‘walls’ of Snap-On tool rack/cabnets and clean room style working conditions. I quickly understood why that little toy cost so much. But the really funny part was the drawers full of ‘modified’ tools the crew came up with to actually get work done ;)