Who remembers the "Transformer TX" flying-car project, intended to equip the US Marines with a small four-seat vehicle able to drive about on the ground like a jeep, hover like a helicopter, or fly like a plane? The first team to publicly offer a contending design has now stepped forward.
Is it a car? Is it a plane? Is it a helicopter? I think we all know the answer
That design is the "Tyrannos" from Logi Aerospace, allied with other companies and organisations including the South West Research Institute and Californian electric-vehicle firm ZAP.
The Tyrannos is nominally intended to provide Marines with the ability to leapfrog over troublesome roadside bombs, mines, and ambushes while remaining able to drive on the ground as they normally might. However, it promises to be much quieter than ordinary helicopters in use and far easier to fly and maintain.
If the Tyrannos can do all its makers claim, it really does have the potential to become the flying car for everyman.
By now, regular readers of Reg sky-car coverage — familiar as you are with the limits of ducted fans, wings, batteries, and other relevant technologies — will be wondering how all this can be done.
Is there, perhaps, a miraculous new power source or energy-storage method? No: the Tyrannos' prime mover will be a 185-horsepower supercharged racecar engine, not even a gas turbine (which would offer more poke for weight but also shorter life, more cost, added maintenance burden, and a lot of noise). There is a hybrid-electric transmission, but nothing outrageous in the way of batteries, as required in some all-electric designs.
Despite this limited amount of power, the Tyrannos design — as you can see in the pictures — includes quite limited amounts of thrust-disc area. Normally such small lift discs would require vast, brutal amounts of power to lift an aircraft vertically into the sky. But somehow, in the Tyrannos, they don't. Why?
Here we come to the vehicle's main special sauce. The Tyrannos doesn't have ordinary ducted fans, but special "shrouded propellers" developed by engineer Rob Bulaga at his firm Trek Aerospace, also part of the design alliance.
The idea of a shrouded prop is that the duct wrapped around it is not merely an inactive doughnut. Rather, as air is sucked in at the top for a vertical takeoff, a stream flow develops both on the inside and the outside of the duct, which then acts as though it were a wing cutting through stationary air to develop lift — even though it is for the moment stationary with respect to the ground. This acts to supplement the thrust produced by the downward-pointing fans.
According to Bulaga, his ring-wings actually deliver half the lift during takeoff, rather than 10 per cent at most as is common among ducted-fan systems. Thus you only need half as much thrust disc area as a helicopter does to lift the same weight. Smaller props are lighter, which in turn means that the electric motors need less juice to spin them and thus are themselves lighter. This means in turn that the craft's whole structure can be lighter, as well.