$10 Multicopter Safety System

The project isn't moving on as fast as I wanted to, others things got in the way...

I finished the print of the first casing for the parachute, based on rough dimensions I took from the parachute, and I made it waaaay too big... Lesson learned.

It took 18 hours to print, but it allows me to make sure my system works correctly before making the definitive casing.

I just came back from my testing facility (ok, I just tossed the parachute from the highest window of my house), and the results seem pretty interesting: with a 500g load, the parachute slows down to about 2.5m/s, and with a kilogram, the speed is still decreased to 6-7m/s, which is slow enough to avoid major damage.

Now that I know how big the parachute needs to be, I'll fold it up correctly and size the compartment. 

I also made a small presentation video to hit the requirements for the Hackaday Prize. Gosh, listening to myself makes me realise how terrible my english actually is...

After sizing the parachute I needed, I took some plastic sheet I had lying around and cut it into a circle of 45cm in diameter.

I then attached 4 strings, making them into eight parachute lines:

The mock-up is ready for some testing. It will allow me to check whether I have enough suface to slow it down, and size up the compartment that will hold it when folded.

I want a system that has the following requirements:

-Be able to install easily on a any kind of multicopter (sub-750g)

-Be lightweight (Under 50g would be great, I still need to figure out how light this actually needs to be)

-Be cheap (If not under $10, at least under 30 bucks)

-Be totally independent from the main system: I want something that deploys the chute when it detects an abnormal drop in altitude (or a g-variation, I have both sensors)

The first thing I have to figure out, is how big the chute needs to be. If I follow a matching table (on page 17 of this PDF: http://www.planete-sciences.org/espace/publications/techniques/parachutes.pdf ), I need a spherical parachute of 43.8cm in diameter to slow down a 1kg body at 10m/s. Now, we will be braking only 750g, but I want it to be slowed down a bit more, so I'll round  this diameter up to 45cm.

With this in mind, I'll first make a mock-up of the chute using simple trash bags, to get a feeling of how big the compartment needs to be.