Hacker News Reader

Comment by fooker | Hacker News Reader

AKA helicopters?

... without pilots, and presumably also without many of the safety features that go with aircraft that carry humans. I wonder what will happen the first time one of these falls out of the air on to something.

And who will be liable? The drone manufacturer or the shipping company? Or no one?

In most places the operator will be liable.

Not "operator" in the sense of the person giving it commands, but the entity that ultimately decides where and why it flies.

and there will always be "insurance" for such cases :)

unmanned choppers existed, iirc. http://www.washingtontimes.com/news/2015/oct/30/black-hawk-d...

I think the answer is, lots of news coverage. Probably would have been the same amount if it were a manned one.

Except that's for military applications. If that thing crashes in a field in a war zone no one cares. If it crashes into a high rise and kills hundreds of office workers, then people will care.

Unmanned heavy flight in populated civilian areas isn't a solved problem and probably one that will never be solved. People won't want the risk. Saving $1 on shipping isn't worth it.

What about longer but still quicker routes than a typical delivery truck? Having a drone means it could do the same pre-programmed route every time. Instead of as-the-crow-flies, have it take a route that's mostly over unpopulated areas but ultimately saves time and money by avoiding traffic, intersections, bridges, etc.

Time is only one of the aspects. UAV can do the same task over and over, and wouldn't have the legislations that limit per-driver throughput (like continuous amount of driving one is allowed). So even if you take longer distances, there will be other benefits.

as a person who developed UAVs in a smaller scale, I agree with your sentiment on crashing.

But i guess this is similar to how crashes from traffic went down over time. We can take all the precautions, do hundreds of thousands of simulations, and it will get better over time.

Well, if your craft is unmanned then it can be very small, which makes the idea appealing for the last mile and less appealing as you start moving cargos the size of a human anyway.

I suspect you'd still need a lot of safety/reliability/redundancy/failsafe type features, because if it crashes it could still kill people.

The routes could be planned so that they could always crash on some place where they wouldn't hurt a human. You don't need the same kind of safety features in an unmanaged cargo drone as you do in something that transport humans.

You can certainly save some money on cargo-only risks. Sure, the thing can't be allowed to crash onto a village, but you can take some controlled risks like flying in worse weather or using worse takeoff/landing strips than you'd chance with human pilots.

There are no such routes around the places where people are willing to routinely pay a lot for fast delivery. Just look at any map.

That assumes that you have zero glide ability.

Multi-rotor powered lift aircraft have effectively zero glide ability. Helicopters and fixed wing aircraft have some glide availability depending on altitude, but you can't count on gliding anywhere when you're experiencing some sort of serious systems failure. And there are generally no safe places to crash in densely populated areas.

Helicopters can autorotate under full engine failure.

https://en.wikipedia.org/wiki/Autorotation

But can multirotors do that too? N-copters seem to have pretty small propellers; will they be able to store enough kinetic energy for autorotation?

Also, AFAIK electric motors directly connected to propellers don't exactly have "idle" mode - they either use power or generate power.

If the terminals of the motor are open, it will rotate freely.

Autorotation uses the energy stored in mass x height to spin the rotor for most of the descent, they are "charging" the kinetic storage until very close to the ground. This speed kinetic energy is only used for the final touchdown. The fixed pitch blades of a multicopter make this impossible. Autorotation is not a question of rotor mass, it's a question of pitch control. Lack of pitch control is the defining property of multicopters.

I forgot about pitch control, which is indeed the deciding factor here, but still - isn't the angular momentum used as that "kinetic energy storage"? Small, light propellers suck at that anyway.

We're talking about cargo drones, so I'm assuming the rotor would be relatively heavy duty compared to the size of the craft. And since we're talking unmanned, you can probably accept higher landing speeds than normal. You are really just interested in preventing a catastrophic landing, so navigating towards an empty area and not exploding on impact.

> Lack of pitch control is the defining property of multicopters.

It is possible to do pitch-controlled propellers on a multi-copter. I recall that someone did this once for an engine-powered multi-rotor craft in order to be able to quickly vary the thrust from each rotor (using a servo that actuated the blade pitch via a rod that extended thru the rotor axle shaft) - because such engines usually can't be varied in speed/thrust as quickly as is needed for multi-rotor control.

There certainly are Chinese makers of quads with pitch and collective for each rotor

A lot is possible, even building a helicopter ;)

While simple pitch control is certainly easier than the phase-dependent pitch control required for a helicopter, a pitch-controlled multicopter would lose a lot of the mechanics simplicity that made multicopters interesting in the first place. But autorotation control code for a pitch-multicopter would be an interesting challenge, maybe for the hobbyist who wants to dive deep doing more than just reimplementing stuff that already exists.

For whatever it's worth, one of the other comments points out that heavy-lift drones are likely to be conventional helicopters rather than multicopters, since smaller rotors are less efficient.

It says "200 miles", so it's probably closer to unmanned pipers than to giant DJIs. The description reads more like using the cargo UAVs as a solution for slow inter-city surface transport (or as a substitute for expensive bush pilots) than as a solution for the last mile.

Helicopters are not fuel efficient. Something with a wing with vertical take off capability is probably much better for such cases.

True. Vertical Take-Off and Landing (VTOL) takes about 6 times the energy as much as flying with a wing. Companies are racing to add VTOL to winged aircrafts: https://lilium.com/.

Reply on news.ycombinator.com