GPS Guided Parachute Recovery System

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The goal of the project is to design a system with a size of a tube about 40cm long by 7cm in diameter, which can be released in free fall from almost anywhere, and will automatically deploy a parachute canopy and steer it to a precise GPS point.

The last prototype could be seen in action on this 3 videos :

Also on this video (with english subtitle [Français - English] ) you will already find a little bit more details about the actual state of the project :

To reach the goal of the project, we have 3 main technical challenges : 

The first technical challenge : Deploy in a safe way a parachute canopy 

In its initial state,  the whole system fit in a tube of an approximative size of 40cm by a diameter of 7cm. 

And what we want, is to, from this tube, deploy, when we want, a steerable, parachute canopy, also known as a ram-air parachute canopy. 

We also want this parachute canopy to be able to fly in a sufficient enough way, which mean with a high enough glide ratio, and flight speed. 

To solve the first challenge, I first started to use a very small paraglider canopy, it flew very well, but I quickly found an important factor for the deployment of the canopy, the aspect ratio, a paraglider or parachute canopy with an aspect ratio > 3 is very difficult to deploy. 

So I decided to start sewing my own parachute canopies to solve this problem. 

After few canopy sewed (you can count a week of work for the fabrication of a parachute canopy) the deployment of the parachute canopy even in bad conditions (bad folding, no forced deployment etc.) started to go perfectly well (see this deployment test video :

Then, once we have a parachute canopy that deploys properly we have the second technical challenge, to be able steer it

For this we have to be able to pull more or less in a coordinated way on the 2 brake lines of the parachute. 

By pulling on the left rear of the parachute and releasing the right rear, we break the left part and accelerate the right part of the parachute, this makes it turn left for example. 

Pulling both lines at the same time will break the parachute, and releasing both lines at the same time will make it fly faster.

It was therefore necessary to find a system allowing to pull more or less 2 ropes/ lines, each one on about twenty centimeters to have enough control over the parachute canopy. 

The solution chosen was to 'hack' servomotors originally designed for rc sailboats, they are sold with a drum spool, and modified inside to be able to still with a closed loop control, make up to 4 turns in each direction. You can see them in action on this video :

Few pictures of the last prototype of the system including the mechanical part with the two servomotors 

Finally the last challenge is to automatically steer the parachute canopy, and this challenge is not yet fully fully solved. 

The idea is the following :

By using a GPS device, we can know where we are in real time, and we know in principle where we want to go, so we can know the angle in which we want to move. 

But then to really move in this direction, we need to know in which direction we are actually moving in reality, so that we can then calculate an error, and a correction to get closer to the direction objective. 

And so the main hard point is, from a certain number of sensors, to deduce in the most precise way possible, the direction in which we are really moving. 

For this there are several solutions : 

  • The first one could be to consider that we are moving in the direction in which the front of the parachute is oriented, for this it is enough to use a magnetometer, however this create 2 concerns : 

- The first is that when there is a little wind, the parachute can drift with the wind, and therefore to go in a given direction, it may for example have to point in another direction. 

- The second problem is that the tube in which the magnetometer could be located moves a bit in all directions, and therefore the magnetometer can very quickly become useless. 

  • The second solution would be to also use a GPS device, as a source of orientation data, since we can draw an angle between where we are and where we want to go, we can also draw an angle between where...
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  • Test, fail, learn, RETRY!

    hadji.yohan02/19/2021 at 09:16 0 comments

    Hi there! 

    In France, every 2 months or so there are school holidays, 

    And for me holidays = parachute test. 

    But when you do a test, it's because you have something to test, so this time what did we test ? 

    The weather balloon that we want to recover usually explode at an altitude of 30km, at this altitude there is almost no air. And what we want is to open a parachute that is kind of hard to open, so we are not really in the best conditions to open a parachute at 30km of altitude directly when the balloon explode. 

    Also, to open the ram-air canopy parachute, we need what we will call an extractor parachute, which is a small round parachute already deployed in the air during the ascent, that will give us during descent, at the chosen moment, the force needed to extract the ram-air canopy from it's deployment bag in which it is folded during ascent. 

    The last point you need to get, is that it is dangerous and therefore illegal to drop an object in absolute free-fall from any altitude (at least where I am) this is why at any moment of the flight we don't want fall with a velocity >5 m/s 

    To sum up, we need to open the raim-air parachute canopy at a lower altitude than the ballon burst altitude (30km), we need a small round parachute to open the ram-air canopy, and we don't want at any moment of the flight to fall at a velocity > 5 m/s 

    And this, is the solution :  

    I call it the collapsable-dragchute  

    The idea is that, we need a big enough dragchute to fall with a velocity < 5 m/s before the opening of the ram-air canopy, but we also need it to be as small as possible once the ram-air canopy is opened, because otherwise it will make impossible the flight of the wing. 

    So to sum up : 

    After the burst of the balloon, everything come down under this drag-chute, at a velocity < 5 m/s, at the desired altitude (where there is enough air of canopy inflation) the dragchute is used to get the canopy out of it's deployment bag, at the same time, the "collapsing line" of the dragchute il released by a small mechanism, the wing is opened, and the dragchute is collapsed. And everything is perfect ! 

    Well at least in theory, because reality is really hard with concepts that seems so easy :) 

    So this objectif of this test was : 

    1. Like each time, get more data on the performance and the flight of the raim-air parachute canopy, see how it react to commands, how it fly with a bit of wind etc etc

    2. To test this new concept of collapsable-drogchute 

    (3. And also last point, get better at organisation of the test flight, with a more "streamlined process", for example with automatic flight mission for the drop drone etc etc..) 

    And if the first and the third mission have been perfectly accomplished

    An example of the data we got from one of the flights : 

    An example of automatic mission with INAV running on the drop drone  

    On the second mission, it is unfortunately not a total success, and at this point, the story continue with this video : 

    As explained in the video, what happened is that we got a tangled dragchute, but what is exactly a tangled dragchute ? 

    If you take a look closely at the "The solution" video, you will see that to get this collapsable dragchute we need to use two different line, so the dragchute before collapse is connected with two line to the system, and what happened there is that during preparation or during ascent, a part of the parachute got stuck between these 2 different lines, which once the system was released got even more stuck between the lines, because they were under tension due to the low but high enough drag of the tangled dragchute.  

    So I've tested, I've failed, but now I've learned, we need to find a way to have one and only one line on this collapsable parachute. But we need two of them to make it collapsable, so how is that possible ? 

    One idea is to get one line into another, like a wire in a tube, but this...

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freeflightlab wrote 02/18/2021 at 23:48 point

Can't wait for your update!!! Really great work Yohan!!!!

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