This progression in technology has been accompanied by increasing amounts of fossil fuel burnt en route. The engines of the Saturn V rocket used for Apollo 11 produced a power of 34 meganewtons, and they burnt about 2,000 tonnes of fuel in just under three minutes.
In today's climate of environmental concern, it is reassuring to discover that future horizons of powered flight may be more eco-friendly. Solar Impulse is a solar-powered plane that could conceivably fly indefinitely, because the power generated by its solar panels is sufficient to store enough energy to keep the craft aloft during the night.
But perhaps the future dimension of powered personal flight is best expressed by Manfred Ruhmer and his work at the company Icaro 2000, famous for its world-leading hang gliders. Ruhmer has utilized the massive advances in accumulator technology to create an electric motor capable of powering a microlight.
Batteries have in fact long been the stumbling block for the pioneers of electric flight. The heavy lead batteries that we use in cars just don't produce enough current to get a plane airborne.
The technology for Ruhmer's electric aircraft was actually initially developed for aeromodellers. Manfred worked on a brushless, external rotor motor, with a high efficiency due to the fact that the only source of friction consists of the two ball-races bearing the shaft. A regulator is used to control engine speed, and the large-diameter propeller was designed for use at relatively low revs to decrease noise and increase efficiency.
Manfred Ruhmer has applied this technology to several aircraft, such as the Swift, the most advanced foot-launched glider in existence, and paragliders, using a motorized harness. But it is the Trike that has really brought electric flight to a dimension of fun, simplicity and safety. Manfred designed a light and simple three-wheeled frame that carries pilot, engine and control equipment, and added a hang-glider wing and control bar. The result is a machine that can be transported to a take-off field by car, assembled and flown with maximum simplicity. Its low speed makes take-off and landing comparitively easy, and in flight it is docile and supremely manoeuvrable. Manfred regularly takes off, climbs for a few minutes, reaches a thermal, switches off the motor, and uses the upcurrents to carry on flying. When the thermals run out, he can glide back down to land, or switch on the motor again. After landing, a rapid charger recharges his lithium-ion polymer batteries, and in just fifteen minutes he is ready to go again, ready for another trip into the dimension of silence, wind in his hair, sharing the sky with swallows and eagles in the golden light of the early evening.
Manfred is constantly engaged in demonstrating the potential of electric flight at airshows in Italy, his native Austria, and elsewhere in Europe. He is also one of the most successful hang glider pilots of all time (he holds the record for the longest flight ever made in a hang glider, 701 km), and so he makes flying the Electro-Trike look very simple. He turns up the revs regulator, takes off smoothly, and then circles the field, wheels and wingtips skimming the grass, skipping over the trees before pushing out on the control bar and climbing into the deep blue. But in terms of technique, electric flying is accessible to everyone.
As Manfred himself points out, the development of electric flight has repeated the progress of the Wright brothers and their contemporaries. People had been trying to fly for years using the power plants available to them, but it was only when steam power had been supplanted by a light and reliable petrol engine that flying became feasible. In the same way, electric flight has at last become possible with the development of light, powerful, quick-charging batteries. Petrol engines still win the day when it comes to range and duration. But the cleanness and silence of the Electro-Trike suggests that it could be the future of personal flight. Like a bicycle of the skies.