Taking Flight: The Long Challenges of Product Development

It’s one of those classic stories of product development. As Rob Bulaga, president, Trek Aerospace, Inc. (trekaero.com), recalls, there’s Mike Moshier. He was running a shop in the Silicon Valley area. Stuck in traffic around San Jose. The year is 1996. It was the year when Java was introduced. The year that Deep Blue beat chess grand master Garry Kasparov at his own game. It was Independence Day and Mission: Impossible at the movies. It was “Wannabe” by the Spice Girls on the radio.

It’s no wonder, then, that Moshier started thinking that sitting in traffic jams on a regular basis was a bit too much. There had to be a better way . . .

Since at least 1965, when James Bond was piloting a jet pack in Thunderball, that mode of transportation has certainly caught the imagination of many people. According to Bulaga, Moshier had been among them. But he determined that the rocket belt wouldn’t work for the simple reason that there isn’t a whole lot of sustained energy in them. As Bulaga puts it, “They’re not practical for much other than flying in and out of sports stadiums.”

So Moshier hit on another approach: ducted fans. That could be the better way of getting vertical lift and sustained travel. So Moshier called on Bulaga, an engineer whom he’d worked with, who happened to have experience with ducted fans. That experience was, coincidentally, car-related. During college Bulaga was part of a team that worked on a high-mileage car that would use ducted fans as part of the propulsion system. (Any use of ducted fans for cars today? we ask. Not directly, Bulaga answers: the wind coming out of the back of it is on the order of 100 mph, which certainly wouldn’t be good for anyone driving behind you.)

So Trek Aerospace was born in 1996, with a goal to create a ducted-fan based way to fly.

Ducted fans?

They are what they sound like: a fan surrounded by a shroud, or duct. Which is a good thing in applications like what are known as “exoskelator aircraft,” which is what the Trek personnel were trying to create: the duct provides protection from the spinning blades, and as someone is wearing the aircraft, arms and legs are good things to protect. Bulaga says that while they do have applicability in somewhat more conventional aircraft, they’re not particularly good at speeds in excess of 150 mph because the drag created by the duct is a penalty. However, the duct isn’t there simply for safety reasons. During operation, the propellers move air over the inside of the duct so that additional thrust is generated. “In our designs, about 45% of the thrust is coming from the on-moving duct,” he explains.

When they started, it was fairly fundamental: “I started out with a lot of sketches,” Bulaga recalls. “Sketches on quad pads—the engineer’s solution to everything. Then I started working in AutoCAD.”

All the while Bulaga was doing research to find out everything that he could about the use of ducted fans in aircraft applications, such as the Hiller flying platform, which used ducted fans and which took flight in January 1955 (see: hiller.org/flying-platform.shtml). (Another coincidence: one of the four manned flying exoskelator proprieties that Trek Aero originally made is now in the Hiller Aviation Museum. One is in the hands of a private collector. The other two suffered mishaps and became spare parts.) Bulaga says that he discovered that good work was done by the National Advisory Committee for Aeronautics (NACA), the precursor to the National Aeronautics and Space Administration (NASA; NACA existed from 1915 to 1958).

But in the early days, NASA helped Trek Aero develop their ducted aircraft, as the small California-based company had the opportunity to team with the NASA Ames Research Center and to utilize the wind tunnels at Moffett Field. At the time, NASA was working with Iowa State University on developing code to predict ducted fan performance. And the Trek Aero engineers were doing the same.

In fact, during this early development, Bulaga says, they went to Ilan Kroo, a professor in the department of Aeronautics and Astronautics at Stanford University (who had been, coincidentally, research scientist, Advanced Aerodynamic Concepts Branch, NASA Ames Research Center, Moffett Field). Kroo, in addition to his aero background, has knowledge of software. And so they set about to develop their own computational fluid dynamics (CFD) program, which is now known as TASPA (Trek Aerospace Shrouded Propeller Analysis).

That’s right: Not only were they working on developing a manned ducted fan aircraft, but they wrote their own CFD program. Why not go with a commercial version? “We didn’t know there were a whole lot of programs out there at the time,” he answers, and adds that the results they obtain with TASPA are better than those achieved using CFD programs based on code that has its roots at MIT (“Come to us, and we’ll design you a better duct,” he quips, commercially).

They spent six weeks at the Moffett Field wind tunnels. When they started, they had a static efficiency of about 50%. “Through tweaking our code and playing with the hardware, we found out how to get our static efficiency above 80%,” Bulaga says.

After working on the project for four years, they got a $5-million award from Defense Advanced Research Projects Agency (DARPA); it was no longer a self-funded program. DARPA was—and is—interested in having a craft that has vertical take-off, hovering, and forward-motion capabilities—like a ducted fan exoskelator.

The first manned flight of the Trek Aero craft, the SoloTrek, occurred in December 2001. They used tethers, two ropes from the side and one from the top. Eventually, they reduced the number of tethers to one, the top rope, which used a retracting mechanism. During one test, when Bulaga was the pilot, the retraction system failed to operate, the rope was sucked into the fan, and down he went. “It wasn’t high enough to hurt me”—about 4 feet—“but it caused $80,000 of damage to the machine, and we missed a deadline for a milestone for DARPA, so they froze our funding.”

In 2003, Moshier lost interest in the project. Bulaga and his colleagues continued on. They rebuilt the aircraft and got back on track with DARPA. They finished the project in 2004.

At that point, they essentially fell into funding limbo. Bulaga explains that DARPA has a “readiness scale.” “They like to work on the 2 to 4 range. The military won’t take something until it is 8 or above,” Bulaga says. “They judged us to be a 5 or a 6.”

Still, the development of ducted aircraft continues at Trek Aerospace, with the development of small, unmanned vehicles, like the OVIWUN, which runs on two 450-W motors and has the ability to lift a 4.5-lb payload. And there are others, like the Dragonfly, which uses a 118-hp rotary engine and can be manned or unmanned.

Bulaga says that they’ve been joining with other companies in pursuit of further development funding, like competing for the DARPA Transformer (TX) program along with partners including the Southwest Research Institute (swri.org), logi AeroSpace (logiaerospace.com), and ZAP Motors (zapworld.com). TX called for a flying car—one that has vertical take-off and landing (VTOL) capability, can carry 1,000 lb., and travel 250 miles, either on land or in the air. They didn’t win. (It went to AAI Corp., Lockheed Martin, Carnegie Mellon University, Pratt & Whitney Rocketdyne, Aurora Flight Services, ThinGap, and Metis Design.)

They’ve been working on light aircraft, windmill design, and a variety of other applications for their technology and know-how.

And while there is no relief from the traffic jams in and around San Jose, Robert Bulaga and colleagues some 145 miles northeast in Folsom keep developing the ducted fan technology.