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Alternative Methods of Recovery for Model Rockets

Hunter Whyte

Technological Problem Solving:

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The Problem

Classical model rocket recovery

Bigger parachute = slower descent and less chance of breaking rocket but also farther drift

Smaller parachute = less drift but also faster descent and greater chance of breaking something

[2] So first off what is the problem that we are trying to solve.

what I’d call “the classical system” for model rocket recovery is the parachute attached to the nose cone attached to the shock cord attached to the rocket. which you guys know what that looks like since that’s what we did in class when we launched our rockets.

This method does work but it has its flaws especially once you start looking at higher power rockets that reach higher altitudes. You encounter a trade off that you have to make between the speed at which your rocket will hit the ground and how far you are going to have to go to retrieve it.

Bigger parachute means slower descent and less chance of breaking something but also farther drift�Smaller parachute means less drift but also faster descent and greater chance of breaking something�

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Existing Solutions

METHOD	PROS	CONS
Low opening	-Limits rocket drift -Only needs one parachute	-Complicated timing and deployment techniques -Can be unreliable -has small margin for error -$$$
Dual Deployment: drogue chute and main chute	-Effective way of eliminating drift -More reliable than single parachute low opening method	-complicated and expensive electronic timing or unreliable analog timing -Requires two parachutes -$$$
GPS tracking devices	Makes rocket easier to find. Small form factor.	-Does not limit rocket drift. -expensive. -$$$$$

[3] Okay so here are some popular existing solutions that people have to this problem

First we have low opening which usually involves some kind of altimeter device that releases the parachute at a set altitude. The good thing about this is you only have to pack one parachute and it does a pretty good job at eliminating drift. The bad thing about this is the price of an altimeter and that if it doesn't deploy or deploys too late your rocket is going to hit the ground going full speed and break.

Next is something like a dual deployment which deploys a smaller parachute at first then once the rocket reaches a certain altitude the main chute deploys. This is good because the first chute slows the rocket down and is more reliable than the single parachute low opening method. And it does a pretty good job of eliminating drift. But it is also pretty complicated and expensive to set up

The last way that helps recover your model rocket is a gps device with some kind of live telemetry which is just wireless communication to help you find it after. Which doesn't help you in flight but you can find the rocket after with the GPS location. These devices are also really really expensive

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My Problem With Existing Solutions - Money

$1226CAD

$516CAD

$942CAD

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Our Solution

Live GPS telemetry

onboard camera

Propellers mounted to payload section

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Guided Recovery

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Parachute Calculations

D = sqrt( (8 m g) / (pi r Cd v2) )��Where��D is the chute diameter in meters�m is the rocket mass in kilograms = 0.1�g is the acceleration of gravity = 9.8 m/s2�r is the density of air = 1.22 kg/m3�Cd is the drag coefficient of the chute, v is the speed at impact with the ground

source: http://www.rocketmime.com/rockets/descent.html

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The Real Parachute Calculations

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The Rocket Design

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The Electronics In the Rocket

GPS

9DOF IMU

2.4ghz radio

3 LiPo batteries

Camera + Camera DVR

Camera Servo

4 Brushed motors + PDB

[11] Okay next is the harder part which took up like 80% of my time on this project. the electronics. just a quick overview of what everything is and then we can get into what it all does. So in the rocket we have a couple of instruments which are the gps module which gives the position of the rocket and the altitude and then there is an inertial measurement unit that has a gyroscope accelerometer and magnetometer built into it which I just have setup to give the compass direction of the rocket on descent. Then we have the radio which transmits those things back to earth. Next is the camera which stays tucked in during launch because it would be really not aerodynamic and then deploys during descent with a button on my laptop. and also there is the propellers that are controlled by the joystick on the ground like you can see here

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The Electronics On The Ground

2.4ghz radio

joystick

Connected to Laptop

Interfacing with a python program via serial communication to give live data of the rocket and save it to a csv

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What the radio communication looks like

Ground sends joystick position, camera deploy command

Rocket receives those and acts accordingly

Rocket sends latitude, longitude, altitude, temperature, compass heading, delay

Ground parses those pieces of data into a string and sends it to laptop >

Laptop displays these values on a live user interface

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Did it work???

?

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What happened

We got data!

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Altitude

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GPS data

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What didn't happen

Guided recovery

[19]Unfortunately not everything went exactly to plan. What didn't work Was the initial idea of a guided recovery. I still think that it could definitely work but there were a few factors that made it not work. First is the weight of the electronics stage which i talked about earlier. It just ended up being way too heavy to come down slow enough to be controlled and since it was so heavy that also meant it didn't go very high either which means less time for control I was also pretty surprised that the rocket was working I kind of forgot to try and control it.

The weather is another thing. It was really windy all weekend and we only got one chance to launch it when the wind was low enough. Still as you probably noticed in the video it didn't go even close to straight up this is partly due to the wind but also the payload probably wasn't that well balanced. So it didn't go high enough to control it coming back down.

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Conclusion

success! (mostly)

$1226CAD

$516CAD

$942CAD

32.4 grams

[21] in conclusion it was mostly a success! like despite the whole guided recovery think not working overall I think that my project went pretty well. We were able to make a live GPS telemetry system for under $23 in parts if you don't count the stuff that had nothing to do with the gps which is almost 40 times less expensive than devices that you can buy which are up to $1200. So I think it's a pretty good affordable alternative especially for people who maybe aren’t launching high power rockets that are really expensive and just think it would be cool to be able to get all of this data and maybe track their rocket down on a windy day. The remote camera deployment is also something that I haven’t seen anyone else do which is kind of cool. So in conclusion I would say that although I didn’t achieve everything I originally planned, the project was a success.

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Questions?

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