Crop Dusting Copter

I have this crazy idea of building a crop dusting copter. It could be multi purpose vehicle but spraying all kinds of crops on those huge fields drives me crazy :) It could also pretty nicely fall into the concept of precision agriculture when first you do NDVI mapping and immediately you start spraying with variable rate thus saving some input costs. To save time and do faster spraying of large fields there could be several of these copters flying simultaneously. I know this is not new so far but there are few planned improvements :

- Pixhawk with 4G/LTE telemetry running control from cloud SW - fully automatic control

- electric propulsion system saving operational costs to minimum

- continual refuelling of pesticide tanks based on preprogrammed sequence (1 copter per minute etc.)

- use sonar or radar to automatically control 2m flying height above vegetation

One may continue to optimize, be creative here but enough for now. It's just an idea anyway. The disadvantage of this concept is obviously the low battery endurance due to high payload (min. 20kg). But batteries can be changed quickly. Now use multlikopter or helicopter ? If multicopter, which one ? 6 or 8 motors ? Which frame ?

The only multicopter with such payload I could find :

All other options include helicopters with gas engine :

Yamaha has 20 years of experience with this. But you cannot buy that copter and they fly manually..

So what do you say ?

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    • are there any updates on pixhawk for spray drones?

    • Thanks, keep me updated. It is not available outside US so I cannot test it. I wonder if there is some delay in communication as it was common for 3G.

  • This is our mini sprayer

    it wont replace a RMax or big heli

    but does quit well for a small unit

    • Beautifull, what do you use as a pump?

  • Oh and you can build electricity yourself today. So you are not dependant on anyone. The price of oil is high here and will be always higher in coming years.
  • Electric power is future. Zero emission, just duration needs more research. It's a matter of time until LiOn is replaced with something better. Batteries can be replaced easily in field too. To me electric multirotor with cca 20kg payload seems ok. It's not so big to become too scary and you can scale the number of them up or down based on the field scale. It should be fully automatic and secure so that even farmers can use them. And price as low as possible..
    • You don't think a multirotor capable of lifting 20kg is scary?

      As for price of oil... I think you'll lose that argument, at least in the forseeable future.  The cost advantage at this point is massively in favour of gas.

      An 800-size heli gas motor is $2-300.  A gallon of gas should fly for at least an hour, and costs $4.  I can build the entire heli for about $3000.  

      Just the motors and props for a multi that size are going to be, I dunno, about $2-4000.  The batteries are, I dunno, $500/set?  Typical system cost on something like this is above $10,000.  Maybe you can get it down to about $5000 is you're really sharp.

      And, I could easily put 4 800 helis in the back of a pickup truck (ie: sprayer fleet).  You probably only get a single multi that big in the back of a truck.

    • Ok in short term gas wins but in long term.. Unless you know how to create fully synthetic oil.. Also the gas price in US is cca 3x cheaper then EU.. So what are your expenses to spray 10000 hectare each year ? I doubt you have any argument.. Electricity can be built yourself, there are many options now. Investition will come back one day.. Then you have pure profit..

    • Any machine you build now will be worn out or crashed long before the world runs out of oil reserves. ;)  It's just not a consideration at this point.

      So lets do an economic analysis based on today's situation, these are really rough numbers.

      Gas Heli: $3000

      Fuel usage: 2L/Hour (rough guess)

      Fuel cost (Europe): 1.80 Euro/L

      Cost/hour: $5/hour

      Large Electric Quad: $8000

      500W solar array: $1000

      Battery Set: $400

      Charger: $200

      Number of battery/charger/panel sets to ensure semi-continuous operation, based on 10 minutes per flight, and 1 hour charge time: 6 sets.

      Total cost of power systems: $9600

      Payoff time: 1920 flight hours.  Based on 4 hours/day, that's over 1 year of flying.

      None of this takes into account machine wear.  I don't think you'll get 320 flights out of each of those batteries.  Obviously the gas motor won't either, but it's only $250.

      I'm all for saving the planet.  But I don't see the economic justification at this point.  And that is based on European fuel prices.  Based on American prices, it looks much much worse.

  • I am currently working on a project to install a Pixhawk on an 800-size gas-powered helicopter.  This is a stepping stone towards installing a Pixhawk on an even larger helicopter.  I see comments that suggest this is basically a "done deal", but it's not.  The devil is in the details.

    I'm really really anxious to get some real-world performance figures for one of these electric multi-rotor sprayers.

    IMO, a gas-powered multirotor is a solution looking for a problem.  They are more mechanically complex than a gas powered helicopter.  They won't fly better, and probably will be less efficient. So why bother?

    So this contest really comes down to the performance of an electric multirotor (=simplicity) vs. a gas powered helicopter (duration, portability, quick re-fueling).  Charging the large battery banks on a large multirotor in the field would be a fun logistical problem.

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