Son of a Buzz Bomb
An engine with a checkered past is the power of the future.
- By Jim Mathews
- Air & Space magazine, September 2007
GE Propulsion Systems Lab
(Page 3 of 5)
GE had a lot of catching up to do. Its answer to Pratt & Whitney’s advanced Seattle unit sits peacefully overlooking the Mohawk River in the bucolic upstate New York town of Niskayuna, between Schenectady and Albany. The campus luxuriates across 525 acres of rolling land, and, tucked in among comfortable homes and suburban cul-de-sacs, you can be forgiven for wondering whether the future really is taking shape anywhere near here. But it is.
“We are turbine-oriented, trying to go for the big prize, and doing it with liquid fuels,” says Anthony Dean, who heads the Propulsion Systems Laboratory at GE’s Global Research Center. An avid cross-country skier, Dean is the picture of a modern scientist who has left the pocket-protector stereotype behind.
Dean, like his company, came to the PDE party a bit late, but has worked hard to make up for lost time. GE, with financial interests in dozens of businesses ranging from appliances to locomotives and credit cards, has designated the pulse detonation engine as one of only six long-term technology areas meriting continued corporate research and development funding; it’s on a par with such hot areas as biotechnology and nanotechnology. With U.S. government money drying up for pulse detonation, that’s a good thing.
A lot of research programs in the field have occurred during the early part of this decade, Dean says, but “those government programs were four or five years, and they’re ending now.” The Navy’s Office of Naval Research, for example, had a multi-university research initiative which ended last year. Though there’s a lull in U.S. government funding, he says, “there’s still funding going on in Japan and a little bit in Russia.”
And there’s also funding at GE. “We’ve actually grown the program a little bit this year,” Dean says. He’s reluctant to give his competitors at Pratt & Whitney any hints of what that means in researchers and resources—“They might write that down and figure out what we’re doing”—but he’ll allow that GE’s PDE program is up “almost 50 percent” from 2006.
Those resources won’t be spent trying to plow the same ground already turned over in Seattle. “GE started eight years ago,” Dean explains, but “really actively started an advanced pulse detonation technology program” —the effort he now leads—“about five years ago. Most of our competition was focused on systems that use oxygen to begin detonation.” But because “you don’t want to carry extra oxygen,” he says, his team is focusing on avoiding that.
“In addition, there was no work around what happens when you try to combine this type of combustion with a turbine engine,” he adds. “At GE, we felt the real end goal was engines that were more efficient than today’s,” a concept in which pulse detonation technology inserted into an airplane’s turbine engine might make more sense.
When GE started looking seriously at pulse detonation engines, there was a lot of good theoretical work, particularly from Caltech, but it was of the single-shot variety: Fill a chamber, detonate it, and see what happens. Dean readily credits those engineers with doing “good science, but it didn’t give you a sense of the engineering challenges.”
Working with NASA, GE combined its PDE test rig with a large axial turbine pulled from a locomotive. Why not an aircraft turbine? The train engine “had the size we wanted, the flow we wanted, and for cost reasons,” Dean says. He and his team ran several configurations, and operated the machine with a test sequence of more than five minutes rather than just a few seconds. The long runs enabled the engine to reach a steady state of operation, “and to my knowledge, certainly with a turbine connected, that’s the first time that’s been done,” Dean says. GE’s rig had eight tubes for pulse detonation, each of which ran at about 20 to 25 cycles per second. “We got a million pressure cycles,” he adds.
It’s a bit of a journey, however, from a PDE rig bolted to a railroad engine to a flyable propulsion system.
“In five years, you could have a flight-weight demonstrator,” Dean says, noting that if the government signaled its commitment with additional funding, “I think GE would pony up its resources, and the other guys would too.” At the beginning of the decade, some scientists said there could be a flying demonstrator by 2010, but “no way are we going to make 2010 at the current level of investment,” he says. “This type of stuff requires a lot of effort, a lot of money. Even GE, a big company, will only go just so far ahead of its customers. We’ll only go so far ahead of where the government is… In fact, [the government] is pulling back on its own internal effort at NASA labs.”
But is it? It’s not a stretch to believe that PDE technology is ready enough to submerge itself into the murky world of what the Pentagon calls “black programs.” These are programs that don’t exist—at least not publicly—and yet they do. The bat-wing B-2 stealth bomber, for example, was a black program, as was the stealthy F-117 Nighthawk. The closest near-term application for a pulse detonation engine was a proposed high-speed missile, and the missile remains the most likely place for a PDE to emerge first, military officials and researchers agree. The U.S. military budget shows money earmarked for such umbrella programs as “Propulsion Technology Initiatives,” and in-house funding continues for propulsion research led by the Office of Naval Research and the Air Force Research Laboratory. And the big players like GE and Pratt & Whitney still continue to put as much of their own money in as they can, without “getting ahead” of their government customers. That suggests that what the companies are spending on PDE research is in line with what their government sponsors expect it to be.