In 1992, Scaled Composites built a radio-controlled UAV intended for 48-hour flights at 65,000 feet. Called Quiver (it was later changed to Raptor, for “Responsive Aircraft Program for Theater Operations”), it had a wingspan of 66 feet and an 80 hp Rotax engine. Scaled also home-brewed the autopilot, and there was some uncertainty about how it might behave before its rates and gains had been properly adjusted. In order to avoid losing the prototype on its first flight, Burt Rutan came up with the idea of providing it with a human safety pilot who could take over in case something went wrong.
Now, the Quiver was designed to carry a 150-pound payload, including a couple of underwing anti-missile missiles, but its skinny fuselage did not have a cockpit, or even room for one. Rutan solved the problem with his customary ingenuity and sublime indifference to human comfort. A backrest and safety belts — but no windshield — were added on top of the fuselage, along with makeshift links to the primary flight controls. Test pilots Mike Melvill and Doug Shane, the latter now Scaled’s CEO, climbed into the makeshift saddle for the first flights.
Shane later described flying in the open air, astride the airplane and behind the beating propeller, as “a new and unwelcome experience.” Landings were particularly harrowing. Melvill recalled “how hard it was to let [the remote pilot] land and not grab the controls.”
On a seemingly unrelated topic, I remember watching in awe, as a small boy inside New York skyscrapers, as a liveried elevator man made a series of subtle adjustments with an ornate brass lever to bring the floor of the elevator to rest in perfect alignment with the floor outside. It seemed like a beautiful example of human skill and adaptability; how cruel to discover that elevators could be made to mind themselves!
Did the first riders in automatic elevators, invited to believe that the touch of a button would carry them up that terrible dark shaft and deposit them safely at their destination, feel the same qualm as Shane and Melvill surely did as their fingers first followed the tremors of a stick controlled from afar?
Or as our children will, when they first board an airplane without a pilot or a cockpit?
The idea of passenger-carrying airplanes without pilots usually comes up in relation to the increasing automation of airliners and — it is rumored — the withering away of basic flying skills in their pilots. But the designers of our future, when they are figuring out how (but not why) to put people on Mars, are meditating a different kind of autonomous flight. The concept is something we have seen in movies and illustrations depicting cities 100 years hence: aerial taxis whizzing among the towers, delivering their occupants to destinations they would have reached, in the olden days, by taxi or light rail.
These are PAVs — personal aerial vehicles — and in their taxi-like commercial form, NASA Langley’s Mark Moore calls them Zip Aircraft, after the Zipcar model of distributed car rental. In the Zip model, locked cars are left by their drivers at their destinations; a person needing a car finds one nearby and makes a reservation through an online service, then opens and drives the car with a smart membership card.
The assumption underlying Zipcars is that most people know how to drive. The obvious difficulty, when considering an aerial version, is that most people do not know how to fly. The solution would be an airplane that flies itself — you tell it where you want to go, and it takes you there.
Although Moore is careful to describe his studies to date as merely exploratory, he is optimistic about the future of PAVs and particularly about the potential of electric power. Electric motors open up possibilities for structural and aerodynamic advances, increased reliability, reduced noise and pollution, and reduced acquisition and operating costs, but they suffer today from the inadequacy of even the best current batteries. For a given powerplant weight, an airplane cannot go nearly as far on battery power as it can on a like mass of liquid fuel. Moore argues, however, that experimental batteries now in development, which should be commercially available by the end of the decade, could provide a four-seat airplane with a range of 200 miles, and that would be sufficient for most PAV trips. Hybridizing the powerplant with a small, range-extending internal-combustion engine would take care of longer trips, at least until still-better batteries arrive.