Raptor NG Discussion

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jedi

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My point was the only practical reasons for the ducts on high speed airliners is to contain the supersonic noise and also passengers don't want visible props.
You would have thought Airbus would know that. And now Embraer is "experimenting" with inducted fans. :rolleyes:
An even more practical reason for the duct is to contain the miscellaneous pieces that fly off the high speed rotating components on occasion.

That is not a problem with the very popular tractor light plane configuration or the extreme aft fan.

It is a potential problem with wing mounted engines such as the Raptor NG.
 

Jet787

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I will just post this as an opposing view. It is from post # 28 of the reference given in HBA post #73 above intended to support the supersonic theory. The posting person, "BD5JDave" appears to know more than many on the thread. Having said that, I do think I spy an error or two in the posting. I do not know what GEAP is in this case.
Geap is a typo, it should be Leap. The CFM Leap engine was the follow on to the CFM-56 engines.
 

5761RF

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I don’t think there is a single turbofan Ever made that doesn’t have supersonic blade tips.

Here is the sound of blade tips going supersonic.
I've always enjoyed the howling of a Rolls-Royce RB211 at takeoff thrust. There's something satisfying about that healthy buzzsaw sound.

 

Malish

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I've always enjoyed the howling of a Rolls-Royce RB211 at takeoff thrust. There's something satisfying about that healthy buzzsaw sound.
And look at these sophisticated fan blades on this turbofan engine to deal with supersonic speed they must to work with.
CFM-blades.png
400467213973b6131942188e96b93380.jpg
It's no surprise, that ducted fan very difficult and expensive to build!
 

nschmandt

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MODERATOR NOTE: Moved the following posts (up to #136) here from another nascent "Raptor" thread. We really don't need another thread on that one airplane. We have two going at the moment. Since nschmandt's questions seem closest to the topic of this thread, I've moved them here and closed off that other one.

______________________________________________________________________________________________________________________


I know there's already been a lot of discussion around the developments of Raptor aircraft lately, but after reading the thread, a few questions remain unanswered:
1) What did we learn from the prototype?
Did the aircraft, as Peter Moller designed it, meet specs? How badly, and in what aspects, did it miss? I've heard people mention that it fell well short of what was promised, but can anyone link the source on those numbers? Also, was the airframe ultimately similar to the velocity, and did it perform similarly? If not, why not?
2) Is the original goal of Raptor achievable?
Personally, I was really impressed he made a working prototype in a relatively short period of time, I don't understand why he's throwing all that away. The original goal of Raptor, as far as I understood, was to stick a Diesel engine in a Velocity and get a pretty nice and cheap cross-country machine. What changed that he doesn't want to pursue that anymore?
3) Why is Peter Moller suddenly pivoting more into the realm of science fiction?
While this is obviously a setback, he's still not in a bad position to rebuild the prototype, possibly with improvements, and continue on the original raptor concept, which had a lot of interest (deposits). Did something change that caused him to think he needed to do something so much more radical? I guess this ties in with question #2, but I don't see why he suddenly needs to change direction and pursue something so different, especially after he made so much progress towards the original goal.
Apologies if the answers to these questions are obvious to those with more experience in aviation. I would really appreciate any insights!
 
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TarDevil

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Did you follow the two prior Raptor threads?
There are myriad reasons why Peter SHOULD have abandoned the original Raptor, especially the diesel engine. Making a diesel work in an airplane isn't a backyard project.
He was never going to make his performance goals, and those reasons are lengthy.
However, he certainly took a huge step back with his new design.
 

bmcj

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It doesn’t matter what we learned… it matters what Peter did (or did not) learn.
 
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nschmandt

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@TarDevil I did follow the Raptor threads, but I'm not technical enough to understand most of what he talks about.
But OK, I think you are saying it was just more complicated than he made it out to be and he shouldn't have tried it on his own.

@bmcj I know...but I'm still personally curious to learn from what happened.
 

nschmandt

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So...if he had done it with one of Continental's diesel engines instead of homebuilding his own, would that have made the project viable?
 

Martin W

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nschmandt .... it is like you are asking us to read all the Raptor posts and watch all the Raptor videos.

Well guess what .... we already have .... and the only way for you to gain the knowledge and get your questions answered is to read and watch them yourself.

That's the nicest way I can say it . Best wishes.
 

Topaz

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Gently, please. He's asking legitimate questions, and ones that can be summarized fairly quickly. I don't think he's looking for the nuance that reading hundreds of forum pages would enable.

These questions also get this particular thread back on-topic. 🍻
 

nschmandt

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To clarify, I've watched most everything he's posted and written, but again I've no experience with engines or building aircraft, so the answers to the questions above are not clear to me. If he gave specs on the prototype other than climb-out speeds I missed that, and I'm not finding the answer from any search engine.
 

TFF

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He would have had less headwind, with a more standard engine, and the engine system, underdeveloped, is what took it out, but if the airframe was still the same, the same bodge fixes and overbuilding would still be there. I don’t know how fast you can get a Continental diesel in your hands. I think preferred customer applies right now.
 
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