hopefully blended wing body aircraft take off (so to speak) and make all movies featuring tube and wing aircraft look obsolete, although it's taken over a century to get this relatively modest shift in form factor; a good test for beliefs about the AI singularity is to imagine what it might do to air travel.
Call me a pessimist, but if the robots don’t take over I have this nagging feeling that blended wing bodies and open turbofans are going to become commercial aviation’s “eternally 10 years away” tech.
Of the two I have more faith in open fans becoming a reality even though the technical challenges are (aiui) harder, just because the potential efficiency gains are so significant. In contrast, although there’s no single dealbreaking engineering obstruction to blended wings, it’s going to require a complete ground-up rework of basically every aspect of how planes are designed, constructed, and handled on the ground for a comparatively modest reward. I feel like people are underestimating the costs involved there.
I don't really understand why these propellers look so funky and marine like but the technical challenges do seem significant.
The blades are moving faster near the tip so the apparent direction of the air (which is the sum of the plane’s linear velocity and the blade’s tangential velocity) changes, meaning the blade actually has to twist to maintain a constant angle of attack. The same thing is true for normal turbofans, the blades are just smaller and enclosed so it’s harder to see.
so do they look different to a regular propeller, like on a Cessna or something, because they have to spin faster?
Pretty much. Conceptually, a propfan is just a turboprop designed to operate in the same performance envelope as a traditional turbofan (30,000 ft, >0.8 Mach). Even regular propellers have a bit of this twist too, but since they spin much slower it’s way less pronounced. One of the big qualitative differences is that traditional props are subsonic whereas to reach the aforementioned performance figures propfans have to be designed for the majority of the blade to be supersonic, and aiui that’s responsible for most of the obvious differences between the designs (more, thinner, bendier blades). Regular turbofans partially get around this by using the cowling inlet to slow the incoming air, so the majority of the blade sees a subsonic airstream. The tips are still supersonic, but being right up against the cowling helps suppress a lot of the noise and inefficiency that would otherwise produce. The fact that propfans are exposed to the full unmitigated airstream and have nothing to help suppress the tip shocks is most of what makes them challenging, I believe.
I see, lots of tiny little sonic booms, sounds like the cavitation difficulties that afflict fast water props.
I gotta say, without the cowling these engines do look a little ungainly, they lack the elegance of the classic turbofan, even the huge ones.
Ok am I the one who has to be juvenile and note the positioning of the two planes in the preview image and the phrase "it's really coming"
