If you have heard of Richard Lugg, you probably know him as the man behind the HyperMach SonicStar supersonic business jet concept. And as if Mach 4 cruise, supersonic laminar flow, plasma drag and boom reduction, and superconducting electric propulsion were not enough, Lugg’s name appears on a new US patent (8,636,241, filed in 2006) for a hybrid jet/electric VTOL aircraft. Graphics: USPTO
The design uses electric-powered lifting fans in the wing roots and canard foreplanes for vertical flight. The fans are powered by electricity generated by turbofans, which provide propulsion in forward flight. In vertical flight, residual thrust from the turbofans is vectored downwards to supplement lift from the fans. In forward flight, all engine power goes to thrust and louver doors close over the fans.
How much engine thrust needs to be vectored depends on the power of the lifting fans, which can range from 25% to 100% of the lift needed for VTOL, the patent says. The advantage of the fans is their exhaust flow is at ambient temperate and low velocity. The power extracted from the turbofans to generate electricity also reduces the temperature and velocity of the vectored engine thrust, allowing the aircraft to operate from unprepared surfaces, the patent claims.
Not surprisingly, there are echoes of the SonicStar and its SonicBlue H-Magjet (Hypersonic-Magnetic Advanced Generation Jet Electric Turbine) engine in the VTOL concept. In the H-Magjet, the fan and compressor stages are driven electrically from a superconducting generator embedded in the turbine, which is driven by burning fuel. This eliminates the shafts within a conventional turbofan and allows each individual stage to run at its optimum speed.
In the hybrid jet/electric VTOL concept, the turbofan drives a generator, “preferably superconducting”, attached to the turbine shaft via an electric clutch, producing megawatts of electrical power. Each fan is magnetically centered within a superconducting magnetic coil that drives it at speeds of 3,600-8,500rpm. Each has its own speed controller and, in a 10-fan aircraft, six are used for lift while four (in the canard) are also used for attitude control in vertical flight, the patent says.
SonicStar (Concept: HyperMach)
HyperMach raised more than eyebrows when it unveiled the SonicStar concept in 2008 – its hybrid-electric jet propulsion and plasma-aerospike flow control seeming more science fiction than feasible technology. The company says it continues to refine the design, and look for a manufacturer to develop and build the aircraft. It hopes to fly by 2024, but no-one is holding their breath.The hybrid jet/electric VTOL design looks a bit more practical and, if not Lugg’s design, then some similar form of distributed-thrust, electric-propulsion VTOL is going to fly sooner rather than later, I am sure.