Yetti

Clamped Mooney wing and really fast quad copter

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There will be a proper physicist along shortly, but I believe the impact goes up exponentially with speed. There are Mooneys that will go 206 knots/hr but probably not at an altitude reachable by a drone. I would like to see what the damage would have been at 160 knots or so. I'd bet it's significantly less.

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Would have been better with airflow over and under the wing

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Without going into too much detail...

impact dynamics are a bit different than ordinary stress strain relationships...

With that much energy, stuff shatters instead of yielding and breaking...

If the test is true to real life...  the Mooney flys home with some expensive sheet metal repairs needed... in a similar fashion of having the speed brakes on one side deployed...

Rule #1... avoid hitting any hard objects...

What was the damage to the spar, anything?

The mass of the battery is pretty dense the rest of the drone didn’t get away unharmed...

why did these fine researchers select the Mooney wing?

They probably did a brand C wing and P wing too...  looks like stirring the pot to me...

they could have gone gruesome and showed hard objects penetrating windshields....

For real spooky things to worry about... ask a motorcycle rider about stuff getting kicked up on the road...

Similar to Mooney speeds, watch Indy cars trying to avoid car parts flying around the track...

 

PP thoughts only, not a physicist...

Best regards,

-a-

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A simple approximation is to us the kinetic energy term, so J/kg is u^2/2; where u is the differential velocity of the two objects. Multiple by the mass of the drone and you get the total energy spread across the impact area.

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2 hours ago, gsxrpilot said:

There will be a proper physicist along shortly, but I believe the impact goes up exponentially with speed. There are Mooneys that will go 206 knots/hr but probably not at an altitude reachable by a drone. I would like to see what the damage would have been at 160 knots or so. I'd bet it's significantly less.

Quadcopters and hex copter can easily make it to altitudes that mooneys fly at. I was big into RC before I got into the real thing, and a lot of that time I spend flying FPV quads and hex copters. I knew a ton of people that took them from 5 to 10 thousand feet. range with the radio control is about 10 miles with a normal Spektrum DX series radio controllers and about 25 miles with a range extender. 10 miles range for a remote control that costs about 200 bucks. 25 miles for a 5 or 6 hundred buck remote control.

this guy made it to 3300 ft. the second vid the guy made it to 16,000ft. that is not a typo. FL160

 

 

Edited by Niko182

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Also note that if you hit a quad copter inboard you’re likely not going to have roll control in either direction as that pushrod travels in the leading edge.  

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My concern would also be ignition of fuel from the volatile battery. 

If I made it back, this would be me. 

6.jpg?w=720

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Still don't think its that much worse than a bird strike.  Lots of birds the size of a drone, and there are a lot more of them than drones.  And birds are heavy wet things made of meat, not light things made of fiberglass.

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They also sent a bird like mass at the wing.  If you ever tried to pick up a hat from a boat, you will find that the hat keep moving away from the boat because of fluid stuff.   Notice they did not hit the leading edge because there would be more strength due to the curve of the leading edge

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400 people or so die in GA accidents every year. No one has yet been killed by a drone strike. Call me back when this issue makes the list.

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No but I already had two close calls with drones. One in chapel hill and another near Trenton NJ.  Both above 2000 AGL and when I was booking it.  At least the bride mostly dive away.  I’m sure it’s a matter of time.  

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I have had about 20 interactions with turkey vulture over 5 years of flying.  No drones yet, cept I saw one on final on commercial going into IAH once.  The buzzards are climb, dip a wing, do whatever you need to not smack one.  see and avoid.

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17 hours ago, gsxrpilot said:

There will be a proper physicist along shortly, but I believe the impact goes up exponentially with speed. There are Mooneys that will go 206 knots/hr but probably not at an altitude reachable by a drone. I would like to see what the damage would have been at 160 knots or so. I'd bet it's significantly less.

Energy goes up as the square of the speed.  They address this in the video and mention closing speeds, assuming some velocity of the drone.  The DJI they used is capable of 30+ mph so take that into account.  238 mph is maybe a bit fast, but (also addressed in the video) these things have the capability of doing more damage than an equivalent-mass bird.  

 

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4 hours ago, steingar said:

Still don't think its that much worse than a bird strike.  Lots of birds the size of a drone, and there are a lot more of them than drones.  And birds are heavy wet things made of meat, not light things made of fiberglass.

This was covered in the video (the longer one, not the 0:43 second clip).  An equivalent mass bird deformed more and did less damage.  The density of the drone, particularly the heavy battery, is something to consider.

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4 hours ago, Antares said:

My concern would also be ignition of fuel from the volatile battery. 

If I made it back, this would be me. 

6.jpg?w=720

Except a lipo takes seconds to short, create the needed heat to combust - it's not an instantaneous reaction. The cell had to be damaged in a way that it shorts internally, then the temperature has to reach a level to support combustion - on a surface that's travelling at presumably 206kts. 

If it somehow managed to perforate and get within your fuel tank - the risk would be near 0 as even 2 cups of water is enough to cool a 2000mAh battery that's trying to blow (personal experience, pack started to go on a charge cycle, tossed in coffee cup, to cool and limit damage, pretty much immediately ended the combustion by ∆t change.)

Likelyhood of a lipo combusting and setting alite your fuel tank = nil. 

 

 

Edited by Hephaestus
Punctuation

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Can't tell which panel they hit, but if it was one with a fuel tank and that tank had fuel in it there would be some resistance of the drone making it back to the spar and "damaging the spar"     Shooting, breaking stuff, running into things over the years has given me pretty good insight to breaking things.  Also there is a control rod supposed to be up front there.

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2 hours ago, rahill said:

Energy goes up as the square of the speed.  They address this in the video and mention closing speeds, assuming some velocity of the drone.  The DJI they used is capable of 30+ mph so take that into account.  238 mph is maybe a bit fast, but (also addressed in the video) these things have the capability of doing more damage than an equivalent-mass bird.  

 

Kinetic energy goes up with the square of speed, but at normal impact velocities momentum determines penetration and damage.  Ke only becomes significant at truly absurd impact velocites (like, 120mm sabot velocity).

 

This article provides a nice primer on the subject: https://www.revolvy.com/page/Impact-depth

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The other thing that is bothering me is the wing is clamped down.   In flight there would be some give.

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37 minutes ago, ShuRugal said:

Kinetic energy goes up with the square of speed, but at normal impact velocities momentum determines penetration and damage.  Ke only becomes significant at truly absurd impact velocites (like, 120mm sabot velocity).

 

This article provides a nice primer on the subject: https://www.revolvy.com/page/Impact-depth

But that reference states "This approach only holds for a blunt impactor (no aerodynamical shape) and a target material with no fibres (no cohesion), at least not at the impactor's speed. This is usually true if the impactor's speed is much higher than the speed of sound within the target material. At such high velocities, most materials start to behave like a fluid."  (note: speed of sound in aluminum is ~6000m/s) It then goes on to discuss very high density projectiles, shaped charges, and the like. That's not the case here.

Perhaps you meant to include the reference about impacts (from the same site) https://www.revolvy.com/page/Impact-(mechanics). "When vehicles collide, the damage is proportionate to the relative velocity of the vehicles, the damage increasing as the square of the velocity since it is the impact kinetic energy (1/2 mv2) which is the variable of importance."

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1 hour ago, rahill said:

But that reference states "This approach only holds for a blunt impactor (no aerodynamical shape) and a target material with no fibres (no cohesion), at least not at the impactor's speed. This is usually true if the impactor's speed is much higher than the speed of sound within the target material. At such high velocities, most materials start to behave like a fluid."  (note: speed of sound in aluminum is ~6000m/s) It then goes on to discuss very high density projectiles, shaped charges, and the like. That's not the case here.

Perhaps you meant to include the reference about impacts (from the same site) https://www.revolvy.com/page/Impact-(mechanics). "When vehicles collide, the damage is proportionate to the relative velocity of the vehicles, the damage increasing as the square of the velocity since it is the impact kinetic energy (1/2 mv2) which is the variable of importance."

Thinking about this, my original post does oversimplify things a bit:  There are really two velocity ranges where Ke is the primary determinator of penetration:

1: Low velocity impacts, where there is not enough energy involved to cause plastic deformation in the target

2: Hyper-velocity impacts, where there is enough energy involved to melt or vaporize a portion of the target and cause secondary damage effects

An example of the lower bound would be something like a baseball pitch:  even though the baseball has enough momentum to penetrate a relatively thin sheet of aluminum, at the speeds most people can throw one, it does not possess enough Ke to cause plastic deformation, and so the metal will instead deform elastically, absorbing the impact, and "spring" back, returning a large portion of energy to the baseball.  At the upper end of that range, it might have enough Ke to cause a permanent deformation in some portion of the metal, but not a large enough portion for it to pas through, and so it leaves a dent, or even a split.

 

So yeah, I oversimplified things a bit, assuming that the context would only be striking things like a hovering drone at cruise speeds.  In retrospect, collisions with a much lower relative velocity are worth considering as well, at which point the Ke involved would be the difference between "I need a ferry permit for this dent" and "shit shit shit, my aileron is jammed by some asshole's drone!"

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7 hours ago, Hephaestus said:

Except a lipo takes seconds to short, create the needed heat to combust - it's not an instantaneous reaction. The cell had to be damaged in a way that it shorts internally, then the temperature has to reach a level to support combustion - on a surface that's travelling at presumably 206kts. 

If it somehow managed to perforate and get within your fuel tank - the risk would be near 0 as even 2 cups of water is enough to cool a 2000mAh battery that's trying to blow (personal experience, pack started to go on a charge cycle, tossed in coffee cup, to cool and limit damage, pretty much immediately ended the combustion by ∆t change.)

Likelyhood of a lipo combusting and setting alite your fuel tank = nil. 

+1.  I'd also point out that lithium polymer batteries most drones use are not entirely rigid structures, so while they constitute a significant fraction of the drone's weight, they are probably not what will penetrate the wing.  That is likely to be the motors.  Those suckers are surprisingly heavy, and of course rigid and made of metal.

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5 hours ago, ShuRugal said:

Kinetic energy goes up with the square of speed, but at normal impact velocities momentum determines penetration and damage.  Ke only becomes significant at truly absurd impact velocites (like, 120mm sabot velocity).

 

This article provides a nice primer on the subject: https://www.revolvy.com/page/Impact-depth

Both KE and momentum matter, but are only part of the story.  The other significant factor is energy loss through elastic deformation (such as crumple zones or bubble wrap), or the "squishiness" of the impact.  If the impact is "completely squishy," only momentum matters.  If the impact is completely "non-squishy", it is KE that matters.  Most impacts, of course, are somewhere in between, although fast impacts tend to be more non-squishy.

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