There are several companies working on supersonic jets. Hermeus is looking to leapfrog them all. Dubbed the Quarterhorse, their unmanned test aircraft is designed for hypersonic flight, with a top speed of Mach 5.5, or 4,219 mph. Powering it is a turbine-based combined cycle (TBCC) engine that uses the proven GE J85 turbojet engine for launch and landing, while in-flight, it feeds air into a ramjet that ups the power to the levels required to reach such insane speeds. Already funded via a partnership with the U.S. Air Force, the company plans to have the Quarterhorse in the air and testing by 2023. It will be followed by a cargo-only version in 2025, and, if all goes well, a larger commercial passenger version in 2029 capable of traveling from New York to London in under an hour.