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Help! UNIVERSITY DRONE CATCHER PROJECT

#1
I’m currently studying mechanical engineering at The University of Birmingham. For my final year project, I have been assigned with designing and making a drone catcher. I have been subscribed to your channel for many years and have seen your video on the Excipio that has inspired an idea of my own. I am hoping that you may be able to provide some help. I intend to use an FPV fixed wing aircraft to suspend a catching net, with weighted bottom, that will entangle a rogue drone by flying above it. On entanglement with the drone the force will detach the net from the fixed wing and pull a parasail from a capsule. The netted drone will now be supported by the parasail which in turn will be towed by the fixed wing much like the way a boat would tow a person attached to a parasail. The tow line will then be released by a servo in a safe place for the rogue drone to float to earth. I would be happy to provide sketches to help understanding. It would be very much appreciated if you could help me answer the following…
  • Which fixed wing aircraft would be suitable to carry the described system (net, drone, parasail, FPV capabilities, extra release servo)? I’m thinking the Eflite Apprentice but can I add another servo?
  • Thus, what transmitter combo should I use?
  • If not incorporated into the aircraft, what FPV system would be suitable?
Budget is not a big concern as it will be funded by the university but ideally the whole system wouldn’t be above $500, any help and advice would be much appreciated.
 

clolsonus

Active member
#3
Just a couple thoughts ... Here at the U of MN we did a project where we suspended sticky insect traps below our wings. We used a full sized X-UAV talon. Our insect traps were the diameter of a petri dish (being that we built them from petri dishes.) These traps created a fair bit of drag and we ended up only flying with 4 of them. The airplane could have handled more traps, but as it was the motor had to run quite a bit harder to overcome the extra drag and we were starting to encounter overheating issues with our ESC. We moved the ESC to be completely external and that helped increase cooling. We thought about dragging a net (much as you describe) but decided that we already were putting as much extra cross section out into the wind as we felt comfortable with. Also, the talon we currently fly with is a pusher prop so probably not the best for towing.




I would be interested in hearing more details about your project as you move forward. How big of a net can you drag on your aircraft of choice? Where did you attach it to the airframe? What measures were required for stable towing? I wonder if you might have better luck towing a bunch of lengths of string (with weights at the end) instead of a net. The string could tangle up a quad copter prop and bring it down ... but maybe not as gently as you had in mind.
 

cranialrectosis

Well-Known Member
Mentor
#4
I'm with @clolsonus. Nets and chutes are complicated and too much drag. I would go the KISS route. IMO, it will be cheaper, faster, have longer range and be more reliable.

I would build a small but FAST and powerful Bloody Baron with FPV ability and tow a few long streamers to tangle the copter props. Release on snare so you don't tank your plane and just let the copter fall.
 

quorneng

Well-known member
#5
harrys
You would be well advised to devise some experiments to establish how much drag a weighted net creates at the likely flying speed of a fixed wing aircraft. Compared to the drag of the planes air frame the drag of a suspended net is likely to be many times greater and its effect on the manoeuvrability of the plane is likely to be just as serious. You still have to position the net to 'catch' the drone in the first place. Then flying with the drone entangled in the net would make the whole thing even worse.
You may well have to think of alternatives.
As planes can be designed to carry weight effectively It might be more effective to release a 'shower' of weighted streamers in the path of the drone. It would only take one to snag its rotors to bring it down.
 
#7
I’m currently studying mechanical engineering at The University of Birmingham. For my final year project, I have been assigned with designing and making a drone catcher. I have been subscribed to your channel for many years and have seen your video on the Excipio that has inspired an idea of my own. I am hoping that you may be able to provide some help. I intend to use an FPV fixed wing aircraft to suspend a catching net, with weighted bottom, that will entangle a rogue drone by flying above it. On entanglement with the drone the force will detach the net from the fixed wing and pull a parasail from a capsule. The netted drone will now be supported by the parasail which in turn will be towed by the fixed wing much like the way a boat would tow a person attached to a parasail. The tow line will then be released by a servo in a safe place for the rogue drone to float to earth. I would be happy to provide sketches to help understanding. It would be very much appreciated if you could help me answer the following…
  • Which fixed wing aircraft would be suitable to carry the described system (net, drone, parasail, FPV capabilities, extra release servo)? I’m thinking the Eflite Apprentice but can I add another servo?
  • Thus, what transmitter combo should I use?
  • If not incorporated into the aircraft, what FPV system would be suitable?
Budget is not a big concern as it will be funded by the university but ideally the whole system wouldn’t be above $500, any help and advice would be much appreciated.
So you are building a rogue drone catcher to catch a rogue drone? They both follow the same rules?
 

evranch

Well-known member
#8
Fun project. Unlike the other opinions, I won't immediately discount the net - however, it's going to have to be an extremely coarse net. This is pretty much like the strings or the streamers, but cross-linked so that the catch is guaranteed.

If you're counting on the force of the collision to detach the net, though, one of two things is likely to happen:
- The net detaches itself from forces generated while maneuvering your aircraft.
- The net doesn't detach on the catch, resulting in you going down together.

You probably need to actively detach or sever the net after the catch. A pair of bomb drop type mechanisms could hold the two sides of the net and release it. Then your chute could pull out, but you likely won't have the power to tow it anywhere - I'd let the drone, net and chute float down on their own. I presume the goal is to recover the drone without wrecking it and wasting money.

Now to your actual questions. This is a university project, so it's proof of concept and presumably short range. For FPV, at minimum you could use an AIO camera and VTX, ~$20 or so. You could step up to something like a Runcam Split and a separate VTX so you can record HD video of the flight, ~$100 for the pair. OR you could spend the university's money on a beautiful, full HD digital FPV system from DJI... $1000+

If you're trying to catch something with fixed wing you will really benefit from a gimbal mount and headtracker so you can actually look at it. Otherwise you will just catch quick glimpses as you fly by. This is going to eat up 2-3 channels. You might want a second camera and video switcher to confirm the catch, that's another channel. Then there's the bomb drop. I'd say an 8 channel receiver at least.

I would build an airframe rather than purchase the Apprentice, you will get more power and carrying capacity for less money. Also it will be a lot easier to modify. How about the FT Guinea Pig - it was designed with a cargo bay with a deployable door. Store the net in the bay and deploy it when you are ready to catch. You can buy a speedbuild kit and power pack so you don't have to do all that cutting - but I'm sure the university has a laser or CNC?
 
#10
I think a plane like the MyFlyDream MFD Nimbus 1800 would be a good choice for you. they are designed for carrying payloads and have features like removable lower hatches etc.
Just a couple thoughts ... Here at the U of MN we did a project where we suspended sticky insect traps below our wings. We used a full sized X-UAV talon. Our insect traps were the diameter of a petri dish (being that we built them from petri dishes.) These traps created a fair bit of drag and we ended up only flying with 4 of them. The airplane could have handled more traps, but as it was the motor had to run quite a bit harder to overcome the extra drag and we were starting to encounter overheating issues with our ESC. We moved the ESC to be completely external and that helped increase cooling. We thought about dragging a net (much as you describe) but decided that we already were putting as much extra cross section out into the wind as we felt comfortable with. Also, the talon we currently fly with is a pusher prop so probably not the best for towing.




I would be interested in hearing more details about your project as you move forward. How big of a net can you drag on your aircraft of choice? Where did you attach it to the airframe? What measures were required for stable towing? I wonder if you might have better luck towing a bunch of lengths of string (with weights at the end) instead of a net. The string could tangle up a quad copter prop and bring it down ... but maybe not as gently as you had in mind.


Very interesting project, thank you for your reply! When I talk about suspending a net, I don't mean the type you would land a fish in with a fine mesh, I'm talking more of criss-crossed fishing line like a soccer net, maybe 1 m by 2 m that would catch the drone props. Would that still be too much drag on a plane such as the MyFlyDream MFD Nimbus 1800?
The reason I can't have impact with the drone landing is because it is for security purposes, so there is the possibility of catching drones with bombs. Thus I need to be able to release the drone in a safe zone in a controlled manner.
 
#11
I'm with @clolsonus. Nets and chutes are complicated and too much drag. I would go the KISS route. IMO, it will be cheaper, faster, have longer range and be more reliable.

I would build a small but FAST and powerful Bloody Baron with FPV ability and tow a few long streamers to tangle the copter props. Release on snare so you don't tank your plane and just let the copter fall.

Could you explain KISS further please? I've never heard of it. Bloody Baron with FPV is a good suggestion thank you I'll take it into account. I'm unable to just let the copter fall because my project is designed to catch drones being illegally. One possible illegal use is a flying remote IED drone that may then fall onto a crowd of people. Hence I need to gain control of the drone then release it with limited impact.
What would you think about towing a small parasail or rectangular chute that would create much less drag to a conventional parachute?
 
#12
Fun project. Unlike the other opinions, I won't immediately discount the net - however, it's going to have to be an extremely coarse net. This is pretty much like the strings or the streamers, but cross-linked so that the catch is guaranteed.

If you're counting on the force of the collision to detach the net, though, one of two things is likely to happen:
- The net detaches itself from forces generated while maneuvering your aircraft.
- The net doesn't detach on the catch, resulting in you going down together.

You probably need to actively detach or sever the net after the catch. A pair of bomb drop type mechanisms could hold the two sides of the net and release it. Then your chute could pull out, but you likely won't have the power to tow it anywhere - I'd let the drone, net and chute float down on their own. I presume the goal is to recover the drone without wrecking it and wasting money.

Now to your actual questions. This is a university project, so it's proof of concept and presumably short range. For FPV, at minimum you could use an AIO camera and VTX, ~$20 or so. You could step up to something like a Runcam Split and a separate VTX so you can record HD video of the flight, ~$100 for the pair. OR you could spend the university's money on a beautiful, full HD digital FPV system from DJI... $1000+

If you're trying to catch something with fixed wing you will really benefit from a gimbal mount and headtracker so you can actually look at it. Otherwise you will just catch quick glimpses as you fly by. This is going to eat up 2-3 channels. You might want a second camera and video switcher to confirm the catch, that's another channel. Then there's the bomb drop. I'd say an 8 channel receiver at least.

I would build an airframe rather than purchase the Apprentice, you will get more power and carrying capacity for less money. Also it will be a lot easier to modify. How about the FT Guinea Pig - it was designed with a cargo bay with a deployable door. Store the net in the bay and deploy it when you are ready to catch. You can buy a speedbuild kit and power pack so you don't have to do all that cutting - but I'm sure the university has a laser or CNC?
Thank you for a vary helpful reply!!
Yes that is what I meant by a net but I don't think I explained it well enough, I mean a net similar gauge to a soccer net that's maybe 1 m by 2 m.
Ideally yes there would be a separate channel and servos to release the the net but I was concerned about adding too many channels.
It's looking like towing is going to be unlikely. What do you think about a small parasail or rectangular parachute that would have less drag than a standard parachute?
The reason for the towing idea is yes to not wreck the drone when testing but also because the project is for security purposes. So like my previous answers, the drone, if carrying and IED, can't just fall where it is entangled in case this is above a theoretical crowd.
I'll take a look at those FPV suggestions thank you, I doubt I'll be able to get the funding for the DJI system though hahah!
A gimbal mount with headtracker is a great idea thank you. I think you're right about building my own air frame, this will allow me to add a transmitter/ receiver with the required channels. Yes the uni has a laser cutter downloading the plans would be possible.
Thank you very much for your help and advice!
 

clolsonus

Active member
#13
Very interesting project, thank you for your reply! When I talk about suspending a net, I don't mean the type you would land a fish in with a fine mesh, I'm talking more of criss-crossed fishing line like a soccer net, maybe 1 m by 2 m that would catch the drone props. Would that still be too much drag on a plane such as the MyFlyDream MFD Nimbus 1800?
I don't mean this to be smug because I don't know the answer myself and I don't know if it's fully possible ... but since you are in school, this could be a great opportunity to research drag formulas, make some estimations, and then crunch the maths to see what the numbers say. Then it would be especially interesting to build the net system, test fly, and see how well your numbers predicted the actual results. I know there is a lot already going on with your project, but as engineers, it's satisfying to come up with ways to predict the outcome, then test the result and see that your predictions were at least in the ball park. And if the result is significantly different from the prediction, then it is interesting to think on that and try to figure out what wasn't accounted for, or what parameter estimation was way off going into the formulas. Then report back here so we can learn too. :)

You could also hit this from the practical perspective and start out building something really simple (as others have suggested) that will for sure fly. Then keep track of the power required for level flight and build up experimentally. There never is a single right way to do things, but a systematic and well documented approach will always look good in a final report.
 
#14
How about a bolo-style net snare rig? A lightweight net with weighted ends actively launched (think stadium t shirt launcher)
I did initially think about this idea, do you mean from ground or from an airframe?
If from ground then it hasn't got the range.
If from an airframe I dismissed it because it's a 'one shot wonder' system which is to risky when dealing with security.
Thank you anyway though!
 
#16
I don't mean this to be smug because I don't know the answer myself and I don't know if it's fully possible ... but since you are in school, this could be a great opportunity to research drag formulas, make some estimations, and then crunch the maths to see what the numbers say. Then it would be especially interesting to build the net system, test fly, and see how well your numbers predicted the actual results. I know there is a lot already going on with your project, but as engineers, it's satisfying to come up with ways to predict the outcome, then test the result and see that your predictions were at least in the ball park. And if the result is significantly different from the prediction, then it is interesting to think on that and try to figure out what wasn't accounted for, or what parameter estimation was way off going into the formulas. Then report back here so we can learn too. :)

You could also hit this from the practical perspective and start out building something really simple (as others have suggested) that will for sure fly. Then keep track of the power required for level flight and build up experimentally. There never is a single right way to do things, but a systematic and well documented approach will always look good in a final report.
Yes you're absolutely right, there is plenty of kinematics etc to go into the methodology section of my report. The report is also, like you say, in an experimental format that will require predictions/hypothesis and comparisons to real results and calculated percentage errors. I will report back here when I get further down the line with my findings.
Thank you for your interesting comments
 
#17
harrys
You would be well advised to devise some experiments to establish how much drag a weighted net creates at the likely flying speed of a fixed wing aircraft. Compared to the drag of the planes air frame the drag of a suspended net is likely to be many times greater and its effect on the manoeuvrability of the plane is likely to be just as serious. You still have to position the net to 'catch' the drone in the first place. Then flying with the drone entangled in the net would make the whole thing even worse.
You may well have to think of alternatives.
As planes can be designed to carry weight effectively It might be more effective to release a 'shower' of weighted streamers in the path of the drone. It would only take one to snag its rotors to bring it down.
I appreciate that it currently seems like an unrealistic system, but there are reasons why I've come to it as apposed to others. I've now discussed these reasons if other answers, but the net is more like a soccer net with small dimensions as apposed to a fishing net which would create a lot of drag. I do plan to carry out some calculations so you're absolutely right.
The reason I can't do the streamer idea is because I need to gain control of the drone in case it is carrying an IED for example in a terrorist attack, all theoretical of course. Then once gaining control, release it in a safe area, ideally without significant impact.
 

Hondo76251

Well-known member
#18
I did initially think about this idea, do you mean from ground or from an airframe?
If from ground then it hasn't got the range.
If from an airframe I dismissed it because it's a 'one shot wonder' system which is to risky when dealing with security.
Thank you anyway though!
I was thinking from the airframe. With drag saved vs dragging a net around you could probably have several launchers but if you have to retain the target that is less feasible. Are you committed to fixed wing?
 
#19
could go with another approach entirety...

good idea that I did consider, but it wouldn't work very well against a rogue drone carrying an IED over a crowd. My project is intended to disable and gain control of drones flying illegally around airports/ prisons/ military bases/ government buildings/ public events etc, therefore it can't simply fall from where it is. Thankyou for your suggestions though!
 
#20
So you are building a rogue drone catcher to catch a rogue drone? They both follow the same rules?
If by rules you mean laws then my concept would be used, in theory, by groups such as the military, HMPS etc etc who would be allowed to disobey these rules to prevent serious consequences such as a terrorist attack. Apologies for not making this clear in my initial post