Of course, there is an engine in there, and there are sizable challenges inherent in situating it within the fuselage. In this four-place jet, your fifth passenger, a big turbofan, is sitting just a bit behind the rear seat. Noise and vibration are very real concerns. Moreover, even when they're hidden away, turbofan engines still run on air, so you've got to deliver some of that atmospherically abundant gas to the engine. In this case, it's done with a pair of huge inlets located on the upper leading-edge wing root. Nothing new there. It's been done for decades, starting in the 1950s with early fighter jets, including the Lockheed P.80 Shooting Star. Keeping those inlets free of ice, for obvious reasons, is also critical. Stratos says it has a special duct design that will prevent ice from building up without extensive, power-robbing use of engine bleed air.