The Hermeus jet has a projected top speed of Mach 5.5?or 6.789 kph (4,219 mph)making it the fastest reusable jet on the planet. Supersonic flight is arriving?in a hurry. In the last 18 months, Boom has successfully tested its XB-1 demonstrator aircraft and pre-sold 15 of its still-in-development 30-seat Overture models to United Airlines. Virgin Galactic and Rolls Royce rolled out a partnership to develop a 19-seater. Even the Russian Federation revealed plans to build a supersonic jet for commercial use. Then there?s the Hermeus Quarterhorse. Think supersonic or Mach 1?the speed of sound?multiply by five and you have the hypersonic Quarterhorse. Last week, the Atlanta-based company announced a $60 million award from the US Air Force to finance testing of the aircraft. Like the Greek god Hermes, this Hermeus is designed to travel seamlessly between worlds, with a projected top speed of Mach 5.5?or 6.789 kph (4,219 mph). That makes it the fastest reusable aircraft on the planet, so a New York-to-London flight will take less than an hour. Belly of the beast: The Quarterhorse?s engine is based on the GE J85 turbojet, but has been modified to reach hypersonic speeds. Courtesy Hermeus The speed will come from a unique engine set-up, a turbine-based combined cycle (TBCC) propulsion system. Such systems use a standard jet engine for launch and landing and to build enough speed in flight to feed air into a second turbine?known as a ramjet or scramjet?which produces more power,...