Ramjet or Shamjet?
I recently came across news about a new type of jet engine, that, as Canadian news outlet CBC says, is an engine with ‘no moving parts’. Interesting? Yes, but… I took notice of this article in particular because the new engine is presented as an entirely new concept in jet engine technology. The article is therefore misleading, but it got me to click, so that’s a ‘win’ for bad technical journalism, I suppose.
But is this a completely new jet engine? In short, no. It’s not a completely new type of engine. At least not that I can find. But there does seem to be some type of new advancement around this existing technology (that’s the claim), and thus merits a bit more research. There are two much better articles here and here on the same technology. (Much better as in not misleading, but still light on specifics.)
The engine is apparently a ‘ramjet’ engine, originally invented in 1913 by French inventor René Lorin. The fatal flaw for general aviation ramjets is that they cannot operate at low speed. They require the forward speed of the craft to be of sufficient velocity that adequate compression can be attained in the combustion chamber, herefore allowing them to do useful work. Otherwise you’re essentially just squirting fuel into a tube and igniting it. Fun to watch perhaps, but not entirely useful. The magic number for ramjets being useful is Mach 0.5, or half the speed of sound. That is the minimum velocity required for a traditional ramjet to produce usable thrust. That would be well over 300 miles per hour depending on your starting altitude. The claim here is that this engine can operate from low speed, i.e. presumably below 300 mph.
The Canadian company Avro, a subsidiary of Atlantis Aircraft, claims to have developed a solution to the low speed ramjet problem. I went to find information on this breakthrough, but their website is, in a word, lacking. They simply have a video posted of this supposed ramjet operating on a static test bed. I admit the video is quite intriguing from appearances, but there is no technical information on this engine. The video certainly shows something is happening. But as far as I can tell for sure, they’ve basically been able to make gas explode inside a very nice looking metal tube, and make the tube glow red hot. (Also the rear view blue flame is pretty impressive… like the universe, in a can.) Unfortunately, this is all I know about this technology. Many tech websites have reported on the engine, but none can provide better detail than what I have here.
Based on what little information there is technically, I can only speculate. My theory is that this new engine is some type of hybrid pre-compressed ramjet, like an air turbo ramjet (pictured), which is essentially two engines in one. A great idea, but also not new, and not terribly efficient because, depending on the flight phase, one of the two engines is not functioning and is therefore dead weight (or worse, drag).
I will withhold judgement until more is known. Avro is a real company, and seems as if it probably has actual funding behind it. In other words, I don’t think this is some garage-invented new cold fusion device. I look forward to more details as they become available, and I will update this post as that happens. A request for further information was sent to the company, but as yet I have not had a response. If you know more about the engine or the technology, feel free to drop us a tip here.