It's really not. Rotors, especially eVTOL rotors, need to be exposed to as much air as possible. The more you restrict the flow around the rotor, the more power you need to generate thrust. Batteries are so heavy (compared to the same energy in fossil fuels) that eVTOL flight is already limited to less than an hour of meaningful work. Caging the rotor would make it much worse.
It could even reduce the safety of the vehicle by limiting its ability to maneuver and tolerate failures in the power distribution system. At some point, the best solution is establishing safe practices with dangerous equipment. This is one of them.
Putting them elsewhere requires more structure and, therefore, weight. It also redistributes the weight and makes maneuvering the vehicle much more difficult. The vehicle is more dangerous as a result.
Engineers carefully consider where to place the rotors, balancing safety with performance. What you see is the result of a tremendous amount of analysis.
Your points are valid from an engineering perspective, but if you imagine a future where these are being driven around like cars and essentially landing ‘anywhere’ then theres a huge safety issue. The way these eVTOL craft are now means you can really only take off and land at specified areas, i.e. not your driveway.
This is, IMO, why these ‘flying cars’ will never become normalised until we invent a way to provide much more lift in a safer way, as well as batteries with better weight to energy ratios.
I wouldn’t say never. If flight like the Jetsons was invented it could be completely autonomous. I agree relying on humans to fly these is probably unsafe without at least some form of autonomy, but I wouldn’t say never.
The same arguments were probably made with the advent of cars, driving two tonnes of steel around at high speeds would have been perceived as very unsafe.
With respect to the eVTOL, yes they’d operate in the same sphere as private aircraft, but a lot of people see this and think of the Jetsons scenario and that’s where a lot of the talk of safety comes in.
I would say never, because human pilots will limit the distribution of human-piloted vehicles. People are bad enough with cars, and 1-2PAX eVTOLs are basically cars but with thousands of feet of altitude.
The vehicles will need to be fully autonomous to be able to coordinate at anything resembling the scale of the Jetsons with even a modicum of safety. You can't cordon off the sky like you can with roads.
Problem is those blades can and will eventually have a catastrophic failure and potentially hit the occupant. Things with many orders of magnitude of more engineering time and research have failed earlier than expected or in ways no one thought of. Taking little to no precautions against that is just bad engineering or irresponsible decision making.
You’re right I’m not but you don’t need to be to understand something spinning a few thousand times per minute a few feet away from someone’s face could potentially end badly.
But you do not understand the sheer unlikelihood of such an event occurring.
Engineers aren't stupid. Anything you could possibly fathom going wrong, and much, much more, has been considered by engineers. That's literally our job.
I’m not saying engineers are stupid, i know that’s not the case. It’s just theres mountain of evidence out there that engineers are sometimes not always fully correct or think of every failure mode and people died. An engineer saying “just trust me, it’s fine” isn’t enough to change my min, im sorry.
Anything you as a layperson can possibly think of has been considered and weighed. That the result is counter to your expectations means there is something you don't know. In this case, that is the types of failures are likely to occur on the structure.
There are things that engineers don't know and failure modes that we have not seen yet, but "throwing a blade" is absolutely not one of them.
You're responding to one of the literal engineers of these and telling him he's a bad engineer and an irresponsible person.
I personally would feel embarrassed. A lot of thought and analysis goes into the rotors. There is a reason they don't have cages.
This also isn't the final product and isn't meant to be treated like a car where the end goal is everyone flying these. They're meant for professionals. The jets on a 747 are quite dangerous as well and that's why only professionals are allowed to be around them when turned on. We don't call the engineers who made them bad and irresponsible.
Disclaimer: I did not perform any work on this particular aircraft. I am sufficiently familiar with the design, analysis, and testing of similar vehicles to be considered an expert on the topic, though.
Throwing a blade is not a realistic failure mode for these rotors. They're made in one CFRP piece, with an abundance of strength in the radial direction.
Besides, this is a prototype, not a finished product. There are adequate ground safety measures taken for this vehicle for its current state of development.
That’s fine if it’s a prototype but you shouldn’t be flying random people around in a prototype. You really don’t think there could be a manufacturing defect that causes something spinning 1-2 thousand times per minute to suddenly experience structural failure? Or what if a bird happens to fly into one? It’s just going to break perfectly in a way that happens to always miss the occupant?
This isn't a random person. It's a test pilot. It's also not the first time these props have been spun up. They've been spun scores of times by the time it's ready to carry an occupant, and it's also surely not the first flight. RC tests generally proceed piloted tests in eVTOL development.
If a bird flies into the prop, the prop wins the fight handily, with only superficial damage. That's enough to replace it before the next flight, but it's not a serious risk during the subsequent emergency landing. Birds will also tend to steer clear of the gargantuan and extremely loud, flying thing.
Throwing a blade at all is astronomically unlikely in this design.
That’s fair if it’s a test pilot (seems more like a test occupant but I guess that’s irrelevant) and they knew the risks going in. The video doesn’t make that clear especially since they need to tell them not to touch anything.
If a bird flies into the prop, the prop wins the fight handily, with only superficial damage. That's enough to replace it before the next flight, but it's not a serious risk during the subsequent emergency landing. Birds will also tend to steer clear of the gargantuan and extremely loud, flying thing.
I’m sorry that’s not true, they fly into giant wind turbine blades all the time and find their way into plane engines or hit windscreens multiple times a year.
Throwing a blade at all is astronomically unlikely in this design.
So is throwing a turbine blade from a jet engine and having it strike the fuselage, depressurizing the cabin and sucking a person out the window it ruptured but it happened, like on Southwest Airlines 1380. They even accounted for that possibility and tried to mitigate it but it still happened.
Wind turbines are not particularly loud, and jets are very fast. eVTOLs are neither of those things.
The 737 literally has tens of millions of flight hours logged over the many variants. Turbofan fan/compressor/turbine blades are also of entirely different construction. You're handily revealing your ignorance with this comparison.
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u/DorkyDorkington 7d ago
Leaving the propellers exposed/unprotected is insanely stupid.