Are any of these able to fly a preset, waypoint path for two or more hours? I don't want to be thinking about the landing just as soon as it gets up in the air.
Of course, there are other designs like fixed wing planes which can be a bit more efficient though more complicated to navigate in confined spaces and without the ability to hover, and you can use internal combustion engines which can get you much longer flight times due to the higher energy density of their power source. But I don't think you're going to find any of the affordable, battery powered multicopters that get you anything over an hour (and even then, I would set my expectations at more like a half-hour for anything affordable in realistic conditions).
> Stalker is a small, silent UAS used by Special Operations Forces since 2006 to perform intelligence, surveillance and reconnaissance missions. In a recent wind tunnel test, the UAS demonstrated 48 hours of continuous flight powered by this innovative laser system.
> Demonstrated net positive power to Stalker in flight, at ranges up to 600 meters.
> The beam director tracked the receiver for long periods, with centimeter accuracy at 500 meters, despite turbulence and aircraft maneuvers.
http://lasermotive.com/products/uav-power-links/
Note they first successfully demonstrated this outdoors 3 years ago: http://www.lockheedmartin.com/us/news/press-releases/2012/au...
HOWEVER: I don't think it's ready for 'consumer grade' things just yet. It's one thing to have it in a controlled wind-tunnel for 48 hours, it's completely different than having it outside and in variable wind, dirt, dust, other objects, etc.
Honestly, I can't imagine my luddite brother or father wrapping their minds around this just yet: "So, I point the laser at this? Why can't I just use a flashlight? Can I use the laser to charge my phone?"
That's actually really interesting.
I have this vision of a large mother UAV with long loiter times that can laser target micro UAVs at much lower altitudes.
A few hobbyists have built gas quads with variable-pitch rotors, but the amount of mechanical complexity and hassle involved makes a similar nitro-powered single-rotor helicopter more appealing for most hobby applications (stunt flying etc).
As more novel designs that don't rely on precise motor speed control (for example, this one) come into play, I think gas motors will make a minor resurgence as people rediscover the energy density (and therefore flight time) they can achieve.
However, for most hobbyists, electric just makes more sense. It's usually quieter, works indoors, is generally a lot less of a pain in the ass to deal with (no need for starters, glow plugs, choke, adjusting mixture, engine maintenance, etc.), and is usually less heavily regulated.
In terms of fixed wing drones, the benefit of electric over gas is mainly ease of use I believe. It's a lot simpler for someone to charge a battery and just plug it in than it is for them to fill up canisters, refuel the engine and cope with the complexities of tweaking and starting an engine. That extra effort and learning curve isn't worth it for the slightly longer slight time.
For aerial mapping the go-to option is normally fixed wing drones, they can easily achieve 30-40 minutes of flight time and this is normally enough for those kind of applications.
PWM motors can control their rotation very precisely unlike IC motors. That is one reason you see multicopter designs nowadays. You can quickly alter the torque. I didn't see how this design alters pitch or roll, but I know there were some coaxial experimental designs that can alter the torque in a single rotation to affect those axis. That is simply not possible with something powered by burning fuel. It might be possible to have a mixed system, using an internal combustion engine for primary lift and electronically controlled steering, but that would be a more complex system and the benefit isn't abundantly clear.
There might be a market for large endurance multirotors, but apparently it's not obviously attractive.
Potentially, if autonomous drones really take off, there could be a countrywide system of solar-powered charging stations that would supply drones with standardized batteries. Such infrastructure would be almost completely self-sufficient and allow drones to fly any distance.
In fact, this model also works for electric cars, manned or unmanned. There's no reason why Tesla Supercharger stations cannot provide a fully charged battery to swap into your car. Of course you'd have to deposit your own battery first so that you cannot get a battery for free.
From least to most maneuverable:
Weather balloon -> Fixed Wing -> Single rotor -> Multirotor
Cheating the calcs a bit and using the table here: http://www.chem.hawaii.edu/uham/lift.html A 3.5oz (~99gram) Go pro needs at least a 22in diameter spherical ballon filled with Helium. And unless you're ok with tethered use, you need to dedicate some power & mass to pointing & station keeping which increases the volume even more. For every gram of other capability you add, you're adding another liter of gas.
Do you know if a hybrid has been done where you have a multi-rotor assisted by TLA ballast?
Some sort of miniaturized hot-air system might work as well.
[0] http://foreignpolicy.com/2013/04/29/epiphanies-from-chris-an...
Let's say you have a 1000mAh battery at 10V that weighs 100g (these numbers have all been made round for purposes of easier arithmetic). Everything else on your drone is weightless, and your motors have perfect efficiency. To keep this aloft, you need to overcome 9.8 m/s^2 that is applied by Earth's gravity; but since we're simplifying things, let's just round that to 10 m/s^2. 10 m/s^2 * 100g is 1 N, which means it requires 1 W of power to keep that battery aloft (resist the force of gravity). 1Ah * 10 V = 10 Wh, so that means you could stay aloft for 10 h (remember, these numbers are unrealistic, we have ignored any kind of efficiency, or the weight of the rest of the drone, etc).
So, lets use two batteries. Now we have 20 Wh of energy available, but we're holding up 200g of battery, which requires 2 W of power to stay aloft, so again, we can stay aloft for just 10 h.
And remember, all of this was ignoring any notion of efficiency or the weight of any other part of the craft to support this. As you increase the weight, motors will need to get more powerful to be able to actually keep it aloft, which means they need to get bigger, which is extra weight that you need to support that isn't giving you any extra energy. So the real world is actually even worse than our idealized model; as you add on more battery, only a fraction of the increase in weight adds more energy, so you will actually see shorter flight times.
Now, of course, there are designs for which increasing the amount of battery can lead to increased flight times. If the power supplied by the motors is sufficient to sustain the extra weight, so they don't need to be scaled up, then increasing the amount of battery relative to the rest of the weight of the craft can lead to higher efficiency as there is less relative "dead weight" (weight besides the batteries, that is not carrying energy). But that can only take you so far, which is why the flight times of drones plateau at a certain point and you can't fix it by just adding more battery.
This is why you don't see electric helicopters carrying people. The energy to weight ratio for batteries is too low; only fossil fuels have a sufficient energy density.
> let's just round that to 10 m/s^2. 10 m/s^2 100g is 1 N, which means it requires 1 W of power to keep that battery aloft*
To transform some force into power, you need to multiply it by a speed (m/s). My favorite example is that a brick resting on a table can "hover" without spending any power (for a weird definition of "hovering").
I think the correct calculation involves the density of the air, to estimate the speed of the air that must be pushed down.
Adding that factor in will mean adding in even more fake, hand-wavy numbers, but doesn't really change the end result; whatever value you end up with, if you double the weight of the batteries, you will need to displace twice as much air (or move it twice as fast) to compensate, which means you'll need to use up twice as much energy, leaving you with the same flight time in the end.
I suppose if it gets too light then wind becomes more of a problem.