The US Air Force has just issued a rather innocuous-looking notice for a new technology called “active combustion control.” But this is quite a momentous development, and here’s why.
Today, the Air Force has two kinds of warplanes that can survive in combat in which fighters and bombers have to compete with integrated air defenses as well as increasingly sophisticated enemy fighters.
One is the Northrop Grumman B-2A bomber. It’s relatively slow, but super-stealthy. It can fly for a long time and drop a lot of weapons.
The other is the Lockheed Martin F-22A. It’s extremely fast and also super-stealthy. But it doesn’t fly for very long without refueling and can carry only a couple of strike weapons (okay, eight if your talking about the Small Diameter Bomb).
The missing link is a single aircraft as nimble as the F-22, as long-range as the B-2 and as at least as stealthy as both. In short, it’s the dream warplane for every gadget-hearting Air Force general.
This melding is the basic concept for what the Air Force now calls the “Next Generation Long Range Strike Aircraft.” It’s supposed to be ready to enter service by 2018 to 2020.
The trick to meeting this schedule is for some company to come up with the next breakthrough in aircraft engine technology. The breakthrough is called “active combustion control,” which is just a fancy name for integrating a fuel injector into an aircraft’s propulsion system.
Aircraft engines using active combustion controls should be able to fly longer distances at a lower rate of fuel consumption.
With today’s engine technology, the flow of gas into the combustion chamber is fairly unrestricted, which is not very efficient. Many years ago, the automotive industry fixed this problem with fuel injectors, and now the aerospace industry wants to make a similar leap — although at a far greater level of sophistication, of course.
It’s a new spin on an old concept. In the past, aircraft designers used variable-geometry wings (think: F-111, F-14, and B-1) to be more efficient in high-speed and cruise-speed. With active combustion controls, the goal is to reconfigure the engine instead of the airframe to be optimal in both states.
I wonder, why has it taken this long to be able to try enabling this advance? I would think, real fuel injection for jets and not just the same afterburner stuff we’ve had for decades, would be already in the bag.
Why has it taken this long? Speaking as an IT guy who supports aircraft engine designers, I’d say, “Because it’s effing hard!” Add to that the fact that until now, the government hasn’t either funded the basic research, or indicated a willingness to buy the end product. Most of the combustor design on the commercial side has been focused on using less fuel and producing fewer pollutants at one set of conditions — the conditions our airline customers spend most of their time at
Hi Neil, that’s a very good question. But it requires a long answer. I’ve posted a response on my own blog, thedewline.typepad.com/stephen_trimble. Let me know if it helps.