Can an S-duct fit a turbofan exhaust instead of the intake? The idea here is to merge 2 exhausts into one at the exact center of the tail. This would be for twin-engine aircraft that have both engines at the tail, like the Boeing 717.
There are of course S-ducts for intakes, like on the Tu-154. I have never seen them for exhausts, however, probably because it's much harder due to the heat.
I know it is engineeringly possible somehow, because I've seen vectored thrust devices with variable geometry, like the iris types and swivel types. For a large commercial jet, it would be easier because the geometry would be static--no moving parts.
But I want to know if it is economically feasible. To take the heat, I think it just needs some super-pure graphite, which does not sound so expensive to me. But I am not an expert.