Ask Hackaday: Long Endurance Quadcopter

Quadcopters are useful little flying machines. They can be used in all sorts of applications, from mapping, to inspecting long pipelines, to border surveillance, or simply for fun. They all have one thing in common, however – a relatively short battery life. Because quadcopters use brute force to churn through the air, they require a lot of energy. More energy for longer flights means more batteries. More batteries means more weight to carry, which requires even more energy. If you want longer flight times, something has to change. Or does it?

A small start-up company called Horizon Unmanned Systems based out of Singapore claims their quadcopter can fly for up to four hours on a single charge, or up to two and a half hours carrying a 2.2 pound load. They claim to be able to pull this off with a novel approach. First, they fill the hollow frame of the quadcopter with hydrogen gas. They use that gas to power a cute little miniaturized fuel cell LiPo battery hybrid gizmo. And that’s about it. The rest is just standard quadcopter stuff.

The secret to all of this is the miniaturized fuel cell, and how it works. Unfortunately, this is as close as we’re going to get (pdf) for a datasheet. Fuel cells are nifty devices that take hydrogen and oxygen and convert them into water, along with electricity. While that sounds simple, making one is not. And making a miniature one light enough for a quadcopter is down right hard.

How would you increase the flight time of quadcopters? Fuel cells are a great idea, but is this technology within the reach of the modern hacker? We’ve seen people make them from scraps out of a junkyard, but how would you miniaturize it and make it light enough to be used as a practical power supply for a quadcopter?

Thanks to [Joseph Rautenbach] for the tip!

111 thoughts on “Ask Hackaday: Long Endurance Quadcopter

  1. Why not have a fuel/ICE/genset charging the battery that runs the quadcopter. For that matter, why not have the ICE engine power variable pitch blades? LiPo’s and fancy software has enabled quiet, smokeless machines that run inside / close to sensitive neighbours. But if you’re outside and endurance is the key design goal, can any current OTS tech beat a traditional fuel/ICE setup?

    1. A while back fuel based quads piqued my interest. To my disappointment there was very few people trying it and even fewer getting it of the ground. Why do you think they failed and how do you think one could design something light-weight enough for prolonged flight? It seems to me that the ICE route will result in quite a heavy quad.

      1. I’m no engineer, but scaling up / down appears to do weird things. A single tech doesn’t seem to be able to cover the full spectrum of requirements, and so compromises have to be made.

        Scaling down we see a rapid disappearance of ICE engines. Getting ICE engines to work at sub-backpack sized flying things appears to be really tricky (raise your badly bruised fingers if you remember trying to start .049’s???). On the flip side, scaling up we don’t see too many battery powered heavy/long range haulers.

        1. I used to fly RC aircraft with 25cc engines. you used an electric start if you did not want your fingers severely cut or severed when starting.

          The biggest problem is with ICE engines is that they do not react to throttle as rapidly as electric. so the on board control can not react fast enough. What is needed is a 20Amp ICE generator that can power 4 to 8 very high power electric motors.

          But even then, you have rotational mass in a large electric motor that refuses to change speed as fast as the tiny little motors on the smaller stuff.

          1. Chip Youngblood of R/C heli fame has created a quad that uses only a single brushless motor running a belt drive system. Control is handled with pitch changes of the props. If you replace the motor with an ICE you should be able to pull it off. Set the throttle to a constant power level and let the variable differential pitch handle the control. Kind of like how they do it for R/C helis now.

          2. Replying to Longshot above ^^^ (HaD’s site seems to forget to add reply buttons to nested comments now)

            I’ve often thought of doing exactly what you just described, the whole quadcopter thing has seemed a bit inelegant to me, one decent powerful ICE running the rotors by belt/shaft drive and then movable ducts/control surfaces or variable pitch props would seem a nicer way to go, after all RC planes and copters have been using ICEs for years, and RC helis have all the necessary control.

            That said, quads seem to be like 3D printers, the answer to any problem even when something else has been the real answer for years…

    2. I agree. A gasoline engine is the only solution that seems practical to me for high endurance quadcopters. These would have a dramatically different price point than the current crop of quadrotors out there, however, and that might limit the number of people who are willing to invest time and energy developing solutions.

    3. I’ve looked into hydrogen fuel cells since generating the low pressure hydrogen can be a simple (if inefficient) task. I couldn’t find any cells that had a reasonable price/performance. Last September I remember a forum post reporting the price of the unit mentioned above was $12,000…..

      I came to the conclusion miniaturizing a small gas motor/generator + LiPo pack would be the most cost effective solution if you wanted the stay electric components after scaling up the size.

    4. It’s also because of how the damn thing flies by manipulating motor speeds. Each propeller needs a gearbox and all that support shit that goes into a combustion engine and then it’s heavy and speeds of each motor can’t be changed suddenly because of all the inertia of moving parts it goes on and on.

  2. I guess the key bit of information here is how heavy the whole system is, including the hydrogen storage bit. The data in the link specifies a MTOW of 5kg (does this mean 4kg for the Quad and 1kg for payload?) The fuel cell maths looks reasonable (I’m guessing 20-30cm2 active membrane area per cell, of which there are x35) although I wonder if the peak power mentioned includes the LiPo battery as 600W off a stack like that seems a bit much. I’d like to see an overall energy density for the system, which can then be compared directly to batteries or even a petrol generator (for example). Given a mass of 0.55kg for the stack and controller (excluding battery, pipework and valves, cabling as well as the hydrogen storage) it’s not going to be for small quads.
    The cost will be a key one too – noted as $5/kWh or $7.50 per flight – but this is for the industrial hydrogen not the cost to the consumer. And compared to electricity at $0.10/kWh (or thereabouts, I’m guessing) it doesn’t look so good.
    The question is, could you build the same capability quadcopter (weight, flight time, etc) using existing lithium battery packs. My guess is yes.

    1. Having a battery isn’t going to help increase the available current. That would only be the case if the thing ever stopped drawing power, giving the battery time to recharge somewhat. A copter is going to be drawing full load nearly all the time.

      1. They don’t draw full load. Electric motors scale their load based off what it’s doing. In hover, it might only be using 40-60% of load. In climb, it might jump to 100%.

        Things like wind and altitude (air pressure) will also change the performance.

    1. 242g (of which 96g is the fuel cartrige) gives 22,5Wh of energy at 2W power output…the power density almost exactly matches a real-world, RC-grade Li-pol battery, which however can easily crank over 1hp…

      1. So, needs a bigger fuel cell reactor. They talked about using them in cars. What’s the power to weight ratio on those? And the size, of something that could power a quadcopter that could lift itself?

  3. hmm… Always trust evidence over claims. Not saying its not plausible.. but on the surface, smells fishy.
    According the spec sheet given:
    * Requires a 6S 1350mA battery to operate the controller and power the cell. That is about 260 grams.
    So, battery plus quoted system weight: 810 grams

    * Spec sheet says 200W, 20-32V, 0-10A, Peak 600W sustainable for no more than 2 minutes.
    Typical small to medium brushless DC motors used in quads/hex peak out at 20A EACH. At a more conservative 5A, we still are WAY over the current spec. This would work in a “toy scale” model… but with not much room to spare. 2A peak motors x 4, plus electronics, plus consumption of the fuel cell controller..

    *Spec sheet says that at rated (pushing 200W), it consumes 2.8L of hydrogen per minute. To fly for 4 hours, you would need to be carrying around 670 Liters of compressed hydrogen. I am not about to do volume and pressure calculations on carbon fiber tubing, but even assuming you can some how safely cap them off, its still going to be WAAAAY below 600 liters. Am I reading the spec sheet wrong?
    Worse, inlet pressure is half a bar. So, you’ll need the added weight of regulator / gauge.

    This is a SERIOUS misapplication of an otherwise exciting technology.

    And lets not forget the origin story of this quote: Oh the humanity.

    1. and let us not forget all the Boyles Law related performance degrades.. such as poor performance at altitude, temperature, the constantly changing weight of the drone as fuel is consumed…
      The way I see it, it will do not much more than ASSIST batteries to extend flying time a little bit.

    2. companies own website indicates that the drone’s hover consumption is 375W and climb is 800W.
      So, even at hover, the system can only provide about half the power the drone needs.

    3. Indeed, there is simply no way the frame can hold a substantial amount of hydrogen (which must be under high pressure; it does not liquify from pressure alone).

      Other than that, the numbers simply don’t add up.

      1 mole of hydrogen is approximately 22.4 standard liters (273K, 100kPa). Each mole contains about 6 * 10^23 atoms, which will give you, at best, the same number of electrons. One Coulomb (meaning 1A for 1s) equals 6.241 * 10^18 electrons, so each mole of hydrogen will give you roughly 100.000 C ~= 26.7Ah. A PEM fuel cell has a typical voltage (under heavy load) of about 0.5V, so this one mole of gas would produce about 13.4Wh of energy.

      To produce 200W for a full hour you would need about 336 standard liters of hydrogen, while the spec sheet claims 2.8L/min = 168L/h, which is exactly half what I calculated.

      Either I’ve screwed something up in the calculations, of they actually expect to get the no-load voltage (about 1V) from a cell while it is delivering it’s maximum current.

      Even without this discrepancy, I cannot see a way to store any significant amount of hydrogen in such a frame without a huge cryogenic system.

      I see only three possibilities: either they are horribly incompetent, it’s just another scam, or both.

      1. Even discounting that 2x discrepancy, their claimed 168 liters of gas is a lot of compression for those little plastic tubes.
        They look to me to be approximately equal to a yard glass, holding about 2 liters each.

    4. On the origin of the quote… may as well give up on cars since they nearly all carry large volumes of a highly flammable liquid. Also never use rockets again for the same reason.

      Hindenburg was the victim of bad design choices. Large surface areas build up static electricity. They knew that then and somewhat designed against it. We know it even better now, and have better ways of handling it and isolating the sensitive hydrogen. With that, small loads like these quadcopters arent carrying humans, and dont have large surface areas. …a completely different animal.

    1. balloon drones were around before quads got off the ground. :)
      But what you gain in loitering time, you loose on mobility and speed.

      As with all things, it is a balancing act. Drones are the least favorable in terms of flight time, payload and power consumption. But they are the only option that lets you fly as nimbly as a hummingbird.. which, for its tiny size, consumes more energy per minute than any other bird out there.

      1. consumes more energy per minute than any other bird out there

        I suspect you mean “per mass per minute” as a condor’s heart probably consumes more energy resting that an entire humming bird consumes at full speed…

        1. Nice correction. Thank you.
          Yes. In flight, consumes more energy per mass per minute.
          From what I understand, if not sucking a certain amount of sugar per minute of flight, they can actually die.

          1. No reply button on the comment below so Ill answer here. …what they do when its not summer? Move to where it is summer is the most common solution. Hibernation is the other.

      2. How about a variable balloon ballast, like a swim bladder. You compress a lighter-than-air gas into a tank for high speed travel, then release it into a bladder for “loitering” mode. Perhaps while you wait for your batteries to charge via solar?

        Even better, you make the ballast balloon out of flexible photo voltaic cells. A hybrid balloon quadcopter.

        Too bad patents are now first to file, I’ve just given the idea away :)

      3. single rotor collective pitch RC helicopters can outmaneuver, out accellerate and still out-loiter a quad. Check out some of the 3D electric heli competition action on youtube.

        1. Yes helis have certain advantages over quads. Especially in loiter. But not terribly easy to fly or affordable. For work some work applications the platform and payload are not ideal.

          1. Modern PCM controls and solid state gyros have made it much easier to fly radio controlled helicopters.

            60 years ago in Argentina, Augusto Cicaré, with only 6 years formal education, designed and built his own helicopter and learned to fly it on his own. Now his company is a large manufacturer of helicopters.

            A very interesting product they make is the SVH-4 helicopter trainer. It’s a full size helicopter connected to a mobile pad. It can move up and down, pitch, yaw and roll exactly the same as a free flying one. The instructor can lock and unlock any combination of controls and motions. That enables a student pilot to experience what every control does in isolation and in combinations to learn their effects on each other. Regular helicopter training can be a pretty hairy deal, with the student having to fly with an instructor who must be always ready to take control if the student screws up – and hope the student will release the controls when told to do so.

            https://www.youtube.com/watch?v=u5KBYHnMat4

            Now why hasn’t anyone made such a setup for radio controlled helicopters?

    2. Paper napkin calculations I did when I considered this (designed the bladder to be a disc shaped so it’d be a spiffy UFO looking quadcopter) is that the additional drag you impose can easily cause a power draw on the motors that negates the gains you achieve if your not indoors/perfectly still air. That is short of looking like a zeppelin, I mean rigid airship, no wait, blimp er.. derigible? Bah whatever! At that point you’re not a zippy little quad anymore.

      1. I used to fly a RC blimp that had a couple of different bladders – one being ufo shaped like you describe. The slightest air current would overpower any control inputs I could give it – which meant that in any air-conditioned space like the office building I worked in at the time, it would immediately head for the AC air intake and get stuck there. To me it felt like perfectly still air! Outdoors was completely out of the question.

        1. I got my sister one for xmas, it’s about 3 feet long, and looks like a fish (I think). The prop runs on a track back and forth on the fish, to alter the pitch of the thing. I think that’s quite clever. I wouldn’t want to use it outdoors, and unfortunately she doesn’t live in an aircraft hangar. She still likes it tho.

    1. Or don’t use something that is only really implementable with DC motors… You could put the same sort of flight controller on a glow engine heli and have most of the features of a quad (hovering on the spot etc) with much longer flight times.
      The farmers use radio controlled helis to do whatever it is they need to do from the sky on rice paddies here.

  4. This newer Kickstarter has an interesting stretch goal that addresses this, ultimately allowing for about an hour and a half of flight time: [url]https://www.kickstarter.com/projects/1600545869/yeair-the-quadcopter-of-the-future-from-1399[/url]

    Implementing a fixed wing in addition to rotors.

    [img]http://i.imgur.com/pHGCIaG.png[/img]

  5. The simple solution is to ditch the hydrogen and use a reforming fuel cell that runs on methane, butane, propane or even methanol.

    Running on lighter refill gas gives you 15 times the energy in the same volume, and costs cents.

    1. Another option is ultra-micro gas turbines:

      http://peswiki.com/images/c/c7/Micro_turbine.jpg

      The efficiency of such a turbine when coupled to a tiny generator is roughly half of what the fuel cell can manage, but that’s still going to give you several times the running time using the denser fuel. Even if you used twice the power to lift it all, it’s still going to stay 3-4 times longer in the air.

      1. wow, never seen one that small (the GE 3D printed one and all the models Ive seen are 4-5x that big!) what’s the operating RPM? Can it run “heavy” fuel or is it limited to propane/natural gas?

        1. As far as I know, it’s a prototype turbine developed for DARPA for personal power generation for soldiers. The power is about 100-600 Watts depending on how hot you run it.

          I found the picture from a free energy crank website, so can’t really follow the lead any further.

      2. Hydrogen: 121 MJ/kg, gasoline: 45 MJ/kg

        gasoline will take much less space and doesn’t need to be pressurized so you can use a lighter container, but it is also a lot less energy per kilo

        1. The problem as you mentioned with hydrogen is storage so much of the advantage of H2 is lost by having a 5000 psi tank. When measured volumetrically compressed H2 to loses out to gasoline 5.6 MJ/L vs 32.4 MJ/L.

          1. Hydride storage is a possibility, but they are generally pretty nasty and dangerous. LiAlH4 holds 10.6% of it’s weight as hydrogen, and can produce hydrogen on demand by reaction with water (or water vapor).
            Sodium Borohydride is less dangerous, but reacts slowly with water, although the reaction can be sped up with a metal catalyst.
            It has found use in direct borohydride fuel cells. http://en.wikipedia.org/wiki/Direct_borohydride_fuel_cell

  6. Why is that every time someone comes up with some great idea that involves multirotors(tm) like delivering pizza that they always use a quad instead of one of the other configurations that doesn’t instantly fall from the sky should a single propeller, motor or ESC fail. It’s almost as if they haven’t actually tried flying one for very long.

    1. it’s also easier to “buy and fly” an autonomous multirotor platform so no time is spent learning to fly or teaching the aircraft. That way concentration is on the “business model” or in this case the power system. It lets a concept get flight proven really quickly with very little skull-sweat or creativity/ingenuity in the actual flight hardware. Which is great when your design is not about flight hardware. But when it *is* about flight hardware, in the case of better wind penetration, longer endurance, or in your example, survivability, then it’s time to leave the well-travelled path and do a bit more work.

  7. perhaps the best solution is to abandon the multirotor platform and move on from training wheels? With autopilots and control gyros as inexpensive, as well as the processing power available in low-weight flight package size, perhaps it’s time to move onto single rotor platforms when endurance is needed? I know it’s “easier” to base some geewhiz business plan on a quad because the hard work has been done, and now they’re pretty much just “buy and fly” for quick demos to get your VC, but the second stage needs to be more efficient. Any efficiency gains created to help quads get more useful, will return even MORE efficiency in a single rotor platform.

    There’s a reason the Firescout is a single rotor design. And almost every successful production helicopter. Excepting some specialist twin rotor heavy-lift aircraft (Chinook and Kaman K-Max types-the coaxial Kamov is a rarer bird for a specialized niche role) everything is single main rotor turning slower and getting greater efficiency.

    1. I think the favouritism for quad-copters over a more standard heli may lay in the need for (or fear of?) a swashplate (and additional servos) whereas quads can get away with fixed props on motors and manage the direction and lift through rapid power control. From those aspects I guess it’s seen as easier route to control a brushless motor than an combustion engine which are slow to react and can have narrow power bands.

      Maybe someone needs to make a popular (because I assume there must be some out there already) hybrid design using a non-swashplated ICE rotor for bulk-lift and brushless motors for control/manoeuvring?
      And a moments googling later – something like this http://www.starlino.com/quadhybrid_intro.html

      1. I mentioned this on another reply. Chis Youngblood designed something called the Stingray. It is a quadrotor that uses a single brushless motor for power driving four variable pitch props through a belt drive system. If you scale that system up you should be able to replace the motor with an ICE. An interesting ability might be that you can trade control crispness for endurance by throttling back on the motor.

      2. The mechanical difference, between pitch control, or a power drive system for a second contra-rotor, or all the other complicated stuff, does start to look really hard compared to sticking a propellor on the end of an electric motor. Mechanics is something a lot of people aren’t good at. Wiring up and using microcontrollers, is much more simpler, and reliable.

    2. The Firescout is a single rotor design because it is based on an existing helicopter platform. Single main rotor designs suffer a hit in lifting efficiency because a nontrivial percentage of the power has to be used to counteract the torque of the main rotor. Tandem rotor designs do not suffer from asymetrical lift problems at higher speeds (a Chinook is actually faster than an Apache). Next generation helicopters are looking at coaxial designs for a number of performance reasons.

  8. I have to agree with many of the sentiments in the comments above. I have been tempted by quads since they first started popping up, but just couldn’t think of anything practical to do with them and the flight times are just horrible.

    The only application that I could think of would be an in-house drone system which I could navigate over the internet. It would be great to fly around the home checking on the cats, windows, doors, etc… while away from home. When done, it lands on a charging station. Since it wouldn’t take long to make the rounds around the house, the flight time isn’t much of an issue.

    Obviously a rolling bot would be better in a one story house, but useless when there are stairs.

    1. >but just couldn’t think of anything practical to do with them and the flight times are just horrible.

      5 minutes is just about right when you actually try to have fun with them instead of trying to do silly “practical” things with them;

        1. Here are some more videos showing (among other things) how stable and maneuverable the design is. (Notice that it uses a regular propeller instead of an impeller, which would, in theory, improve its efficiency. I seem to recall finding out that it works best when the center of gravity is high, but I don’t recall why.

    1. As opposed to driving around sitting on volatile flammable liquids with explosive charges at arms distance. Or setting a pile of alkali metals that catch fire when exposed to oxygen under your seat.

        1. I was speaking more to the lithium cells in hybrid cars and consumer electronics.
          A magnesium frame will burn. Old VWs had solid Mg engine blocks, many performance cars still have them, sleeved with better wearing cylinder material. Every now and again a recycler or machine shop catches fire and the fire departments just contain it and break out the marshmallows.
          Metal fires are hard to put out since they burn so hot. The only way to do it is to dissipate the heat and remove oxygen, mostly by smothering it with sand. For small scale stuff like computers it’d probably mostly be burned out by the time emergency crews get there.

          1. It’s insanely difficult to get any largish block of Mg to start burning; the thermal conductivity is just too good. I’ve seen a video where they go at a large rod of magnesium with a blowtorch but the rest of the rod acts as an exceptionally good heatsink so it’s not possible to get even a small spot to ignite.

            A building fire could do it, because you’d heat the whole thing up at once. But a fire on the same scale as the block or less? No chance.

        2. Magnesium used in computers and most other consumer products is alloyed with other metals to make it very difficult to burn. http://simson.net/hacks/cubefire.html

          Mongoose, the originator of the cast aluminum BMX bicycle wheel, had some pure magnesium ones made for their factory race team. They had the foundry do the castings in secret at night because they didn’t have the permits to cast the flammable metal. Since it’s rather unlikely a bicycle will catch on fire, the pure mag wheels weren’t a hazard.

      1. The difference is that petrol/gasoline burns as a pool fire, and metal fires are also fires and are both relatively hard to ignite. Even the slightest spark (shorting a coin cell, for example) will ignite hydrogen and when mixed in the right ration with pure oxygen (as it is here) it doesn’t burn, it explodes with a LOT of force.

  9. Long duration vertical thrust aricraft? You can’t get there from here, at least until Mr Fusion is available later this year. The best solution I can think of is a lighter than air mothership, perhaps a helium filled lifting body / wing craft and daughter craft for maneuverability.

    I haven’t done any calculations but I wonder about a catalytic burner and a heat engine. Could it be made small enough and efficient enough to be suitable?

    1. I don’t think Stirling engines have ever taken off (not meant as a pun) anywhere. There’s probably a good reason for this. The only other heat engine I can think of is a steam engine, or a turbine. Not lightweight.

  10. Call me skeptical but I don see how they will be able to store enough H2 under pressure (a few hundred PSI max?) in a couple of polycarbonate tubes to provide the amps (15 to 20) needed for 2 to 4 hours.

  11. Maplin in the UK sell these

    http://www.maplin.co.uk/p/brunton-hydrogen-reactor-portable-power-bank-black-n39dt

    (probably at a much higher price than you’d get them elsewhere. Not supporting Maplin’s silly prices, just a source of this gadget). It’s a fuel-cell reactor. Comes with battery-sized H2 canisters, and there’s an electrolysing “charger” for filling them up from water. I think the fuel cell needs a heat sink, but still there seems some potential for disassembling the unit into something smaller, since there’s plenty of fans in a copter. It claims to output 2 amps with 4500mAh capacity. It might be good for a quadcopter or similar vehicle that uses a lot of power.

    I initially had the impression that the copter here used the hydrogen for lift, but now I don’t think so. I wonder if it’s compressed?

    As the guy above said, using chemical fuel might be another alternative. However engines are generally much more complicated than a battery and motor. I suppose one central engine and some belts or cogs to drive 4 propellors would do. Using motor / generators would be too much weight, compared to a battery, and that’s all part of the equation. The main problem would be that quadcopters manoeuvre by selectively throttling the motors, for attitude and direction control. That’d be very hard to do mechanically with one engine, and four engines is begging for one of them to fail regularly. I was thinking of a range between model helicopter engines, up to lawnmower engines with a pretty big vehicle, although you’d have to watch out if it dropped on you.

    Added to this, mobile phones have made high-capacity cheap batteries possible. Miniature ICE engines are really not cheap. Still, with phones and laptops, storing energy is big business, so things are only going to get better.

  12. Seeing how most quads are used for arial photography (this includes utility use such as inspecting pipe and utility lines too) the introduction of vibration loving gas engines would make it much more difficult to achieve good image stability. Fuel cell seems like a good direction to go in to achieve endurance, though I think other solutions are much more feasible and available right now at least for applications such as utility inspection, such as automated charging stations.

    1. News channels and police helicopters figured out how to gimbal a camera below a shaky platform decades ago. For a hobby scale quad some rubber grommets would probably suffice.

      1. Depends on the scale of the shaking compared to the scale of the gimbal. Steadicam was invented a while ago, which is gimballed and weighted. The weight’s important. Unless the drone only makes very slight vibrations, a gimbal setup would be impractical. Rubber grommets would again depend on the camera having a large enough mass. All this mass is exactly what you don’t want to fly with. Maybe an active system using solenoids or a fast linear actuator would do, perhaps even a loudspeaker mechanism, fed from a very quick motion sensor.

  13. Wouldn’t it make more sense to make a hybrid unit that has the qualities of a quad and fixed wing? Use mechanically deployed fixed wing to turn it into a glider for forward flight and vertical props for hover and other modes.

    This would solve the maneuverability problem while allowing for controllable forward flight. While quad technology is nice, a hybrid approach solves the problem of constant power drain.

  14. Hydrogen? Really? There is almost nothing more dangerous to work with.

    Why not build a tilt-rotor like the Opsrey? The economy and speed of a fixed wing with the VTOL of a helicopter. Not as meneuverable as a quad, but much more efficient. The incredible computing power available in small packages should allow the complexity to work.

    I like the generator set idea. Couple an R/C aircraft motor like a .15, with a generator and a battery to allow quicker power transitions, to the electric motor powerplants. I can assure you that the Nitro fuel has excellent power density, as does the motor.

    1. I forgot the most important aspect. The Osprey design will fly in 30 minutes, the same distance covered by the quad copter in 4 hours. Add a stabilized camera mount and you will have an unbeatable design.
      Just my 2 cents worth….

  15. Just some brainstorming ideas come to mind (please excuse any non sequiturs);

    1.) Power tethering with very small gauge 2-wire wire cable. The wire could be used to provide recharging power to battery rather than power sourcing. Distance and height would be sacrificed only to the extent the controller could move with it on the ground or air. Only heat from over-use may be a problem. The temptation to just keep going for hours on end is overwhelming but should be limited due to thermal runaway on the motors.

    2.) Like in SkyLifter you could reduce weight via neutral buoyancy with Helium in a hard enclosure under or over the QC (quadcopter). You need no actual lift so the Helium would not have to levitate the QC only reduce it’s weight. You need not fool with ballast nor Helium release. The enclosure may interfere with flight dynamics but if you pay attention to the overall enclosure shape you may overcome that. I believe the ellipse or saucer shape is indicated here. Carbon composite materials could be used for the enclosure and the QC frame. Putting it on the underside removes QC rotor interference. However, the gondola (above) configuration does afford more stability. But R&D experimentation is indicated here.

    3.) A proprietary material allows thin film (CIGS cell) solar cells to be painted on any surface with very little weight. It uses nano technology. This could be used to recharge batteries with sunlight, even on cloudy days too. At night you could even supply light to it for recharging battery with a high intensity Q-Beam spotlight. However the inventor decided to cave into special interest pressure and cheap photovoltaics from China. Truth be told the USG took over his patent and is using it for their DARPA projects. I believe it was Martin Roscheisen and Brian Sager from now defunct Nanosolar.I know the official Wikipedia propaganda so no need to repeat it here.

    4.) Using stepper motors and a piece of fruit (code word for Arduino, Rasberry, etc.), you could send fast high-power pulses to each motor versus battery consuming continuous power. Some where I read that an early hand-held satellite data transceiver in the 1980’s used this technique to pulse high power to the on-board RF transmitter but saved on battery power. The pulses are too fast for a human to see or hear but the QC battery doesn’t expire as quickly as it did before. R&D experimentation is indicated.

    5.) If you can talk K. R. Sridhar to share his great idea for solid oxide fuel cell (SOFC), called BLOOM BOX, you could get a very small fuel cell but you would need some expensive materials – scandium oxide (Sc2O3) and some sort of gas. Hydrogen is not required. Scandia is available from Russia from old nuclear stockpiles. Also these boxes run very hot and could stress the QC’s components.

    I personally am thinking about experimenting with #1.

    1. Are nitro engines actually able to take that RPM long term? When I was a kid I had nitro RC cars, but the engines were pretty unreliable and the car usually isn’t at max RPM that long. They would sometimes just die, which isn’t a problem on the ground. I have a Phantom2 quad and for flying, brushless DC’s seem more reliable to me, although there is a higher chance of mechanical failure considering 4 vs. 1 engine.
      I have no idea how reliable/trustworthy RC nitro engines are, thus my question.

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