"Coyote" SSST VFDR
A VFDR (Variable Flow Ducted Rocket produced by Aerojet Rocketdyne) is a Ramjet using fuel which is the effluent of a solid propellant gas generator. The fuel flow is metered by a hot gas valve prior to injection in the Ramjet Combustor.
The "Coyote" Supersonic Sea Skimming Target (SSST) is the only Ramjet Propulsion System in the U.S. currently operational and in production. Particularly, the SSST uses the VFDR Propulsion System.
The next generation SSST VFDR systems use an advanced VFDR fuel. Both the current State-of-the-Art and Next-Generational Fuel models feature 7" dual inlets and can achieve Mach 3.25 at 30,000 feet.