I'll add a few questions:
- Can you ensure safe failure modes for your in-flight drones?
- Who assumes liability when your drones crash?
- What is the blade tip speed during operation? What precautions do you take when flying in populated areas?
- Can you ensure safe failure modes for your in-flight drones?
- Who assumes liability when your drones crash?
- What is the blade tip speed during operation? What precautions do you take when flying in populated areas?
- Add rotors. The demo video showed an 8-rotor drone, I can imagine that building it as a pair of parallel quad rotors from the power supply point of view would give you quite a bit of control even at a 50% loss. A single-engine loss is obviously fairly small beans. I'm emphatically not an expert so this is armchair engineering.
- I don't know why anyone would ask this question. The answer is trivially obvious (the operator of the drone, whichever legal entity that ends up being modulo whatever insurance they certainly have). Obviously "it could crash" is hardly novel in other delivery services and yet they seem to survive the liability question without issue.
- Probably quite dangerous. I imagine you want to fly quite high for cruising for obstacle-avoidance and noise anyway so 90% of your distance this isn't a problem. I think the answer here is "don't hit people" just like with existing forms of transportation (or more realistically "be as careful about not hitting people as your liability insurance continues to reward you for").
And with regards to the blade speed, you can make it largely a non-issue by using shrouds/wire mesh. People don't worry about the blade speed of a floor standing fan even as they brush up against it.
Well, the thing about a multirotor is that a motor failure is going to drastically throw off the stability of the aircraft. The controller would have to be able to recognize the failure, kill the faulty rotor hub, and compensate on the remaining motors in very short order to keep the airframe from getting so far off balance that it tumbles out of the sky.
Though, honestly, I'd think the controller or battery failing is a more likely mode of failure than one of the brushless motors suddenly dying.
Like an earlier poster acknowledged, the current hobby grade gear is not really engineered with industrial use in mind, but that's a fairly simple engineering problem which has already been solved by the groups who are using drones commercially (i.e. the military)
I have no doubt what so ever that Amazon, Google etc have the engineering chops to bring the software and hardware being used in drones up to an industrial grade.
Don't assume that because the first thing that you thought of upon hearing "delivery drones" is infeasible that the whole idea is unworkable. It just needs an engineer with a little more imagination
Edit: a couple of obvious solutions to your battery/controller failure mode would be a) use redundant controllers. They're small enough that you could easily have two or more running in tandem and checking eachothers integrity, and b) if you lose main battery you can autorotate down and land somewhere reasonably safe. If you use EDFs/shrouded blades they aren't a safety issue, and building a map of safe landing zones for a city is not a huge ask for somebody like Google.
Now for somebody else willing to use their imagination: what do you do about cheeky individuals interfering with your drone during delivery?
You really don't see how there's a huge difference between balancing thrust between relatively equal power sources and losing so much thrust that the aircraft is inherently unstable?
Because that's kind of a huge issue - multirotors fundamentally rely on having power at each corner for aerodynamic stability. Even brief loss of power to one is going to put you into a tumbling state with no way to compensate for it.
>that's a fairly simple engineering problem which has already been solved by the groups who are using drones commercially (i.e. the military)
What multirotor UAS systems does the military have in service for reliable flight over moderate distances?
I'd also take issue with the suggestion that controlling an aircraft which has become unstable over an axis that you no longer have control over is "a simple engineering problem."
>They're small enough that you could easily have two or more running in tandem and checking eachothers integrity
I was referring to the speed controllers that convert the battery power to AC for the brushless motors. I'd expect commercial grade ESCs to be overbuilt, but they put out a good bit of heat that has to be engineered around. They're also one of the more common modes of failure for the brushless motor systems used in mutlirotors.
>It just needs an engineer with a little more imagination
This is the equivalent to saying "we're going to magic away any problems with this idea."
EDIT:
I missed this.
> If you use EDFs
Seriously? Do you even realize how terrible a suggestion that is? EDFs are even worse in terms of energy efficiency and they'd compound stability issues since they have relatively poor throttle response.
But I suppose we can imagine those problems away too.
I've been thinking that a SawStop-type of technology might be a possible solution there.
Additionally, if you're going to allow the blades to hit anything you more or less need to accept that it will result in a crash, even if you stop them immediately. Better to just guard them from contact in the first place.