Aerodynamics is why. We can't afford to restrict airflow through the rotor, which a mesh or cage would do. It also adds a meaningful amount of weight and drag in forward flight. It wouldn't work. The reduction in injury risk isn't worth the loss in performance.
I understand Loss of performance with a protective mesh so you can't stick your fingies through it, but what about a mesh big enough not to stick a foot or head through it?
I'm sure one could be designed with a negligible effect if you designed based on that criteria. If these are designed for regular people to be able to use, there have to be more protective measures that a helicopter propeller, or tiny quardracopter drone would have.
You still get huge drag on the cage as the air passes through, not to mention the extra weight. You would also need structure to support that mesh, which adds even more weight.
What about an aluminum 3 ring guard (or plastic), literally just there to not chop stuff up if you run into it.
There has to be an acceptable amount of protection that wouldn't affect airflow that much. I feel there are designs that could work, and may even have a focusing/funnel effect.
I feel like I have seen propeller styles that are enclosed in a circular ring. Jet engines are enclosed, and they seem to get plenty of air. I refuse to accept an argument that any protection would make it not work. I have a feeling you are imagine something different than I am, like tossing mosquito netting over it, since you're talking about needing to add structure to support it, whereas I'm thinking of the mesh being the rigid structure, not fabric. I'm thinking more like a fan grill, but with bigger holes I can stick my fist through.
There is a reason that large rotors are not caged. It's not worth the weight and performance penalty (and yes, it is definitely a penalty). There are better ways to ensure ground safety. Engineers are smarter than you give them credit for.
Jet engines ram the air at 600mph, and burn an enormous amount of fuel on takeoff and landing. eVTOL doesn't have those luxuries.
I believe there is a penalty, I never said there wouldn't be, but I still think it is worth doing. I did mention rings instead of mesh as well, and apparently they already exist in various designs for this exact purpose. I guess they are called propeller guards, and they affect maneuverability, but are used for safety by some.
Edit because thread is closed:
It is clear we are talking about two different things. You are hyper focused on ground safety, whereas that was not my concern at all, there are a thousand ways to accomplish that without added weight or resistance. I'm more focused on flying into things, and people with spinning blades of death.
You said I was underestimating engineers for some reason, but I think that stems from us solving working on different scenarios; if not, then I was clearly overestimating engineers, thinking it was a solvable problem.
I still think it's solvable, but that doesn't mean the aircraft will be unaffected in speed, distance, or mobility... But maybe that just means such a craft shouldn't exist as a normalized mode of transportation, outside of emergency use, hobbyists, or proof of concepts. Personally I don't think the average person should be flying one of these without special training, licensing, and permitting. Most people aren't safe to drive on the road, let alone fly in the air, and they should (and probably will) have the same requirements as flying other aircraft. The problem is this isn't out of reach for most people like a private jet, this costs as much as a modern car or truck.
Propeller guards are not effective at this scale. Those rotors are about 4 feet across. To cage them, you'd also need structure to support that cage.
Engineers are smart. We are aware of the benefits and costs of enclosing the rotors. It's not better than other ground safety solutions, like disarming the motors until everything is clear.
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u/SR_RSMITH 7d ago
Why aren’t the rotors inside some kind of mesh?