Moller's Driven … To Fly - Moller Sky Car prototype

Automotive Design & Production,  Oct, 2001  by Christopher A. Sawyer

• E-mail
• Print
• Link

Given the need for a high wing loading, low overall weight, and structural strength and simplicity, it's no surprise that Sky Car's structure is made of honeycomb graphite composites. "Weight is a greater concern for Sky Car than for conventional airplanes," says Moller, "because we have to lift each pound off the ground vertically." In the case of the four-passenger version, this means a gross weight of 2,400 lb. with almost 800 lb. of payload. The composite materials contribute significantly to Sky Car's current $1.0 million/unit cost, an amount that actually has the U.S. military excited. Why? It's less expensive than most conventional combat technologies, and has greater mission flexibility.

Given the extensive technology found in this vehicle, you'd expect that Moller International had a line on powerful design software and heavy-duty computing power. "There's no design software out there that'll help us do the job," sighs Moller. "I'm a computer illiterate myself, so I rely on our independent consultants for advice. They insist we're faced with designing everything ourselves." This self-reliance also extends to the design and assembly of the electronic motherboards and flight software.

The Sky Car will rely on a proprietary, quadruple-redundant "voting" type of avionics package similar to the type found on the F-16 and Space Shuttle. "One programmer doesn't write the entire package," explains Moller. "If there is a bug in the software, it will end up in one of the four programs, and automatically switch out of that program when the voting takes place." Machine language is used for the avionics program. It's very robust," says Moller. "It uses a minimal amount of space, and has the least complexity."

Rebunbancy

The Sky Car has 26 CPUs on board so that if one circuit fails, there's a complete backup system ready to take its place. Designing, developing, and building them has taken much time and money, but Moller knows the cost has been small in comparison to what might happen were they unavailable. "I'm trying to show that this is doable," he cautions. "Another corporation can bring the capital-perhaps with government help-necessary to streamline some of these systems."

A previous concept, which looked like a 1950s-era flying saucer with eight engines nestled in the basic donut shape, had approximately 25,000 lines of software code and dual redundancy. Two independent stability systems triggered back and forth, helping the pilot- Moller-keep the aircraft under control. This was a far cry from an earlier design in which the pilot sat in the center of the craft while a giant ring rotor, supported by air bearings, rotated around the outside. That version had a single flight control system. "If a ten-cent resistor had burned out," recounts Moller, "I would have gone down with it."

NEXT STEPS

Though Moller plans to make the first powered flight of the Sky car about the time you read this, there's still more work to do before he's ready to test Sky Car's estimated 350 mph cruising speed. Expensive full-scale wind tunnel tests that put the vehicle through a complete flight profile are necessary before attempts are made to gain Federal Aviation Administration (FAA) certification of the Sky Car's forward flight characteristics. It's possible the onboard parachutes might come in handy during the testing phase, though Moller thinks they will have a more psychological than actual need once production is reached.