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Testing Altitude Proof of Concept

A project log for Water Bottle Rocket Science Kit

A modular STEM kit (for youth and adults) built around Water Bottle Rockets

Darian JohnsonDarian Johnson 05/07/2019 at 21:120 Comments

Last weekend, I decided to build a simple proof of concept that:

The Build

Altitude Monitor

I decided to use an Adafruit nRF52 Bluefruit LE Feather as the BLE and MCU for the PoC. My rationale was that it expect to use a similar System on Chip device for the final product.

 All of the components used for the PoC test are Adafruit products (wishlist here->http://www.adafruit.com/wishlists/486595). 

Rocket

I used a 3D printed nose code and wings from the US Water Rockets website. I used a 73 mm diameter 1 liter bottle for the body of my rocket.

Launcher

Finally, I built a makeshift launcher using:

Instructions to assemble the cork, needle, and pump can be found here: https://www.instructables.com/lesson/Pump-Rocket/

Note: This is not an optimal launching solution, as the rocket will launch before adequate pressure is built. For this flight, I was only testing recording altitude, so I didn't care about getting a lot of "air"

The Flights

Going in, I knew there were going to be a few problems:

Given all that, I was able to get 5 test runs in before I destroyed all my nose cones. This was enough to validate the proof of concept. Each flight was about 2 seconds, and I was able to record altitude every 300 ms. In addition, I was able to send the peak altitude to by phone via BLE.

Time (ms)Altitude (m)
00
<3001.99
6008.33
90010.91
120010.54
15007.56
18001.6

Results/Concerns

The current PoC can accurately indicate top altitude, but the data increments (300 ms) is wider that I would like. 

The SD card did eject on landing, so either we have to make the landing more stable or move to SPI flash (and sync data via BLE).

I also have a problem in that I am not able to start the test at launch (primarily because I start recording data, then I start pumping, and the rocket launches whenever the pressure imbalance forces the cork out).  To fix this, I need to hold the rocket in place, achieve the designated pressure, then start the measurements at the same time of the launch, with smaller data increments.

Next Steps

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