Multirotor Emergency Parachute?

[rcspaceflight]

Just a random thought that I got when reading a different thread. I know a lot of people talk about how one of the problems with a multirotor is that once the battery is gone, the craft just drops like a rock.

What if you used a separate battery to power a parachute that would automatically deploy with a relay that is hooked up to the main battery?

I know the system would add weight to the multirotor, but parachutes don't weigh that much, a relay doesn't weigh that much, and you only need a small battery that could power a single servo or whatever mechanism you use to eject the parachute. You could probably even add an alarm to the system to make it easier to locate the failed craft. Both would be powered from the same battery and relay.

It could be a neat, useful Flite Test episode. If I flew multirotors I would probably do it myself. Except I wouldn't have the heart to try it out... What if it fails? Remember the Flite Test episode with the parachute in a plane? That ended well....

 

[chaos23]

well as i just dropped $700 AUD on a quad build this is an idea ive thrown around as well, in theory its a good idea, but lets do some science.

speed gravity acc. is .987 ms/s

so at 10m up your MR will be doing 4m/s when it hit the ground
at 20m 6m/s

small numbers but just take a moment to think how fast 4 meters a second actually is, even the crazy swede cant say i landed it after a drop like that lol. so lets talk about slowing that down a bit. parachutes, well they have a record of not doing the job when needed, but there are other options. for the same weight as the setup mentioned, a reserve lipo can be set up to save your quad from a nasty end. a small battery that can run your quad for whats called a "suicide retro-burn" in the space industry, a last ditch high output deceleration to avert disaster. now you dont need to care if this battery over discharges past the PNR its only task in life is to save your expensive rotor.

now as for how this would be set up im not 100% on. but i will post updates here for others as i find out and insure my MR from the grips of gravity.

 

[xuzme720]

The only issue with that is if the multi is inverted during the "retro burn"! You could actually accelerate the impact and increase the crater size. Thrust would only work in one direction where drag would work in any.

 

[rcspaceflight]

I'm no multirotor expert, but what if something else, besides just the battery, fails? A parachute would be kind of a "cure all" and wouldn't rely on any other system of the quad.

Maybe a secondary Rx with it's own battery to deploy the parachute would be better than anything automatic. Since it's a secondary, complete system, then if you encounter any issue, you can just deploy the parachute.

I think it would be nice if it doesn't rely on a servo and air flow. I don't want to use the word "explosive", but there has to be some other way to really force the parachute out so it deploys instantly. Like a CO2 cartridge or something.

 

[xuzme720]

A spring is probably better as it's simpler.

 

[William A]

Air bags.

Like the Mars rover landing.

 

[rcspaceflight]

Air bags.

Like the Mars rover landing.

I was starting to think that too. Maybe even a single air bag on the bottom and a chute on top. It'll force the craft to land on the bag.

But just a spring to eject the chute would certainly be simpler.

I'm unsure if the best idea would be to have guards on the props so the wire/string of the chute doesn't get tangled, or use some sort of stiff wire to keep the strings up and out of the way.

Not that I would ever actual do any of this. It's just fun to throw ideas around.

 

[chaos23]

Excellent points. I did some digging and my retro rotor idea hasn't been done for exactly the same points you mentioned. The parachute idea still even with a flawless deployment system won't guarantee the chute will open. Airbags now that's a good idea that needs more investigation, Co2 deployment but what would be a good trigger system. Manual isnt full proof if the tr fails. The other option is a springy crash cage that jack knifes open. Like prongs that extend out at lose of control which still alow the rotors to work if you regain signal for instance, unlike the Airbags.

 

[rlaska]

Someone posted a video a while ago of a bixler converted into a vaguely Osprey-like quad-rotor setup. Something like that could be flown down safely if there was insufficient power to drive the props.

So… the best emergency countermeasure would be to have a fixed wing?
[DUCK!]

^--- fixed-wing snob

 

[andybenton]

There is a serious consideration to be made here...
depending on the orientation of the multirotor, you'll have to contend with wildly unpredictable spinning props. much the way an autorotation works in an rc heli, the multirotor falling under gravity will cause the props to spin at considerable rpm... it poses the question of how to get the chute out around the rotors.

it is possible to consider propelling the chute away from the craft itself, as suggested under spring pressure, or possibly co2, however the problem lies in the chutes rigging getting entangled in the props.

the only viable fix for this issue I can think of would be to mount the chute so it ejects directly out the side of the craft, and locate it on the end of the boom... I believe this would allow the chute time to open and begin to slow the craft, orienting it up on its side that the spinning props are well away from the main chute line...

the only other idea I've got would be to mount a mast centrally on the craft and eject the chute from the mast straight up, although that poses an issue for falling inverted.... as do all of these ideas.

attaching a chute to a multirotor is a fun problem to consider, but its almost as hard to do as attaching one to a tradition heli... there's just not a really good spot to mount it, allowing for optimal operation.

but, then again, lots of things are complex, and were merely speculating on the considerations of tackling this issue.

keep thinking, build some prototypes and try to develop a safe way to control the crashes. your idea may be the next big thing, or something thatll make fpv "drones" "safer"

 

[rcspaceflight]

I was thinking about how to set up a system to ensure that, no matter what, the parachute would be ejected. If your Tx fails, then even a back up Rx wouldn't work. If it's hooked up to the battery, then if you get a Rx lock out, then the chute wouldn't open.

I think the only way to for sure have the system work, no matter what, is to have a "dead man's pedal" like they have on modern freight trains. You would have a button that your press every 5 seconds and if you fail to press it then the parachute is ejected. Which is a horrible way to fly. A lot can happen in even 5 seconds, so if you changed it to a longer time then odds are it wouldn't work.

I just don't think any sensors on the craft would work. Unless it was a proximity set up that went off if the craft got too low. Which would actually work fine if you went with an air bag system. So even if the craft falls from 1000feet and the system didn't automatically deploy until 15feet, it would still save the craft. But not necessarily anyone that it lands on.

Maybe the best would be the second Rx, but also have a signal loss alarm that would activate the chute. If the second Rx has a separate power source, then even if you get locked out you could still use your Tx on that second Rx.

 

[rcspaceflight]

About where to mount the parachute: I think it may be best to make a bottom heavy multirotor. Have the props up high with all of the weight below them. That would help to ensure that the craft would fall bottom first. The drag created by the props would, hopefully, cause the craft to automatically level. Then have a single long string go straight up before the strings divide apart to support the ends of the chute. You don't necessarily need to eject the chute instantly. If you let the craft fall a foot or two, then hopefully the craft would right it's self before then.

I know that a bottom heavy multirotor isn't the best to fly, but I think this system is for expensive camera rigs. Not your everyday use tricopter. If you're going to do loops and stunts and such, you better be planning on crashing and making repairs.

But maybe with a thick enough and long enough string/cord it wouldn't matter if it got tangled in a prop. If the cord is strong enough, the prop would break and the cord would hold. A broken prop, and possibly a burnt out motor or bent shaft, is better than breaking a camera and flight controller.

 

[andybenton]

most spectrum brand receivers have an indicator light, brown out indicators, and other such provisions that operate on 3v logic. also there are some receivers with built in RSSI. an arduino program could be written that would check for signal strength at a given interval of time. the same program could have a condition written in that would deploy the chute if the signal were to be lost.

if someone could get it to work, then it wouldn't be too hard to build a dedicated circuit board with the components and processor... the whole pcb would only cost a few bucks...


didn't chad mention he would like to incorporate some arduino based projects into the flights???? the same program could be written to contain data logging parameters, used along with the chute, basic fpv equipment flown by the apm 2.5, gps logs could be obtained, along with temp, humidity, barometric pressure, air speed, ground speed, altitude, pack voltage, signal strength, and any number of other sensors could be added and flown for data collection.... the sensors could also help to offset the weight of the parachute and correct for CG.
I already considered the issue of lofting all of that equipment, but with multirotors flying with full blown dslr cameras and gimbals...
I don't see the couple of ounces being a huge issue for a decent sized quad.

 

[xuzme720]

A chute like this might be less prone to tangling in the rotors maybe...
They also seem to deploy pretty quickly.

 

[andybenton]

I love Ed's channel. lots of good ideas. I was thinking about his chutes also... one single line to worry about, easy to pack, and relatively light, I think he discusses the proper sizing considering weight when using those chutes.


by the way, I'm LOVING this discussion.

 

[Crady]

Yes! I'm looking at building my first heavy-lift quad and the idea of a catastrophic failure causing the loss of thousands in gear is sickening. A ballistic chute for heavy quads would be awesome.

 

[chaos23]

I personally wouldn't trust the chute idea as a failure at 10m would not be high enough for a chute to work. The airbags idea is the way I would go, as for hitting someone you should never fly over anything you dont want getting hit. That its there own fault for not getting out the way.

tbh only someone with a sick setup with gps and every sensor under the sun with hundreds if not thousands of dollars worth of camera gear would realistically need that level of insurance. Face it we build quads because they are tough and cheap to fix

 

[xuzme720]

If you are lofting a big bucks DSLR, maybe something like an ejection seat could save the camera. Eject the gimbal and inflate airbags around it...The camera has less mass and is more compact. No rotors to deal with as well.
The trick is still how to trigger the release to fire.

 

[chaos23]

Well I think the Chad or the swede will need to be locked in a basement to find that answer

 

[andybenton]

I agree, theres a lot that could be learned here...