COLORADO SPRINGS—Hypersonic aircraft developer Hermeus expects to receive Pratt & Whitney’s F100-229 military turbofan for tests later this year as part of plans to integrate the engine into its upscaled Chimera II turbine-based combined cycle (TBCC) propulsion system. Commenting on the selection of the F100, Mike Smayda, co-founder and chief product officer at Hermeus, says “if you look at the missions that the larger longer-range aircraft are designed for, it’s clear that the entire propulsion system needs to be scaled up. Going back to the six-decade-old J58 engine developed for the Mach 3-plus Lockheed SR-71, this experience includes Hermeus-like designs that achieved sustained flight above the Mach cutoff point of a normal turbojet by diverting inlet air from the compressor directly into the afterburner