Machine Design

Burt Rutan designs his last aircraft for Scaled Composites: The Bipod

Scaled Composites

The last aircraft designed by Burt Rutan, founder and CTO of Scaled Composites, Mojave, Calif., appears to be the Bipod, a hybrid gas-electric plane that can also be driven on roads and highways like a car. Rutan has since retired from the company, but not before designing almost two dozen aircraft. Among those aircraft were the Voyager, the first plane to circle the world on a single tank of gas, and SpaceShipOne, the suborbital spaceplane which earned the Ansari X-Prize in 2004 for being the first privately funded spacecraft to reach space twice within a two-week period.

The 1,430-lb Bipod consists of two fuselages, each with a cockpit, connected by 31-ft 10-in. wing and tail surfaces, some of which detach and store in the fuselages for ground travel.

Each fuselage has a forward and aft wheel, giving the ground version a stable four-wheeled platform with low drag. Each fuselage also carries a 450-cc, four-cycle internal-combustion engine that powers either the rear wheels or the propellers on the tail’s horizontal stabilizer and wings. Additionally, the engines power a generator. For extra power on takeoffs and in emergency situations, the craft has 0.6-kW-hr of lithium batteries in the nose of each fuselage as well. They are recharged when the Bipod is cruising.

The vehicle’s center of gravity was optimized for stability during ground operations. So to make it easier for the plane to rotate and go airborne, air is blown over the horizontal stabilizer. The plane also uses an electrical transmission so either engine can power either propeller without using mechanical shafts and gearboxes.

The plane has undergone preliminary testing, but has yet to be outfitted with propellers or the motors for them. When completed, the Bipod should cruise at 100 mph and have an airborne range of 760 miles. It can also fly at 200 mph, but that cuts the range to 530 miles. On the road, Bipod should be able to travel 820 miles on both a full tank of gas (18 gallons) and fully charged batteries, or 35 miles on batteries alone.

© 2011 Penton Media, Inc.

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