In a previous Instructable, we wen't over how to build an Avionics Module using a FreescaleFRDM-K64F dev board, an FRDM-STBC-AGM01 9-axis IMU board and an MPL3115A2 Pressure/Temperature sensor. In this Instructables we are going to go over how to prepare the module for launch, and what we can do with the data after launch.
Please note that this is Not an Instructable on how to launch a High-Powered Rocket, We would really recommend that you launch at-least one High-powered rocket at a Tripoli or NAR launch site without any avionics and get your Level 1 Certification before adding any electronics to your rocket. We might make an Instructable on that later, but in this one we are going to concentrate specifically on loading the payload bay and processing the data afterwords
Step 1: What You'll Need Before Launch
Before heading to the launch site, please ensure you have the following components
- Freescale Avionics Module, you can find instructions for building it Here
- A High Powered Rocket with at-least a 3 Inch Diameter Payload bay such as the LOC Precision CALIBER ISP Kit from Discount Rocketry (Special thanks to the HCC (Hillsborough Community College) Physics Club for providing the rocket).
- Whatever you normally bring to a rocket launch (as we set in the introduction, please attend a launch event and launch At-least one high-powered rocket before trying this)
- 2 Foam Packing blocks(Or one cut in half, ours came from the box that my Leap Motion came in)
- Este's Altimeter can be handy in confirming that the information from the avionics module is valid, though this is optional.
- Packing Tape
Step 2: Load the Payload
This step is what your going to want to do just before you take your rocket out to the pad. Please note that this step may need to be done differently depending on your payload area, but the basics are pretty straight forward, first add the first foam block to the bottom of the Payload Bay as seen in the first image.
Once the padding is all the way at the bottom, drop the power supply connected to a USB to Micro-USB cord as far down as it can go, preferably fit it inside the padding as seen in the second image. Next plug the MicroUSB side of the cord into the avionics module as seen in the third image. The module should power on, if the status led is a solid Cyan make sure you have a MicroSD Card attached to it and hit the reset button once to reinitialize everything, it should start blinking blue in 1/4 second intervals indicating its ready to begin recording. Don't start recording yet, for now coil the rest of the USB cord into the payload area by rotating the module and finally fit the module in as seen in the fourth image. Bring a roll of packing tape the second foam block along with the rest of the rocket to the launch pad.
Step 3: Prepare for Liftoff
This step should be taken after you have loaded your rocket onto the launch pad. Remove the Avionics Module from your payload area, make sure it stays connected to the power supply and hold down SW2 until the status LED blinks green twice. After the led turns off place the module back in the payload area. push it as far down as you can without forcing it, then fold the second foam block into the payload area as seen in the third image. make sure the MicroSD Card is clear of the foam, if folded as seen in the fourth image you should be able to see the MicroSD Card untouched by the foam.
Finally insert the nosecone and Be sure to tape your payload bay closed. Otherwise your avionics module may be ejected from the payload bay when the parachute deploys (we are speaking from experience here).
your rocket is ready to launch! Proceed to liftoff as you would any other High-Powered rocket launch.
Step 4: Recovery
there's only a couple of things that should be noted about recovering the rocket, as soon as possible, remove the Avionics module and check the status LED, if its off, hold down the button labeled SW3 until the status LED starts blinking Blue in one second intervals this means the module is finished recording and has stopped accessing the SD Card which means its safe to power down and disconnect. If it does not start blinking blue after a few seconds of holding down the button that means the power may have been disconnected during flight. If the status LED is a solid Cyan color, then that means the module may have been reset during flight or the MicroSD Card has been physically disconnected. In any of these cases your data is probably still OK. we can proceed to the next step to read the data and see what happened during flight.
Step 5: Analyze the Data
Now that you've built your avionics module, launched your rocket, and hopefully safely recovered your rocket intact, Its time to put the data to good use.
Insert the MicroSD Card from the avionics module into your Computer, you should see something like the first image inside the card. Each time you hit the start button on the Avionics Module it has created a new csv file. Each csv file will contain a series of rows, the last row is a timestamp, the rest of the rows represent 3-axis accelerometer, 3-axis gyro, 3-axis magnetometer data and pressure/temperature data adding up to a total of 12 rows of raw data describing what was happening at 50 millisecond intervals.
The easiest way to make sense of all this data is to open the data in Excel or import it into a Google Spreadsheet. After importing the data feel free to use our spreadsheet as a template. the spreadsheet extrapolates altitude and pressure into seperate columns, normalizes the timeline and graphs as much data as we could. allowing us to better understand what happened during the flight.
During our two flights, this is what we discovered using the Freescale Avionics module:
Our first launch made it to a maximum altitude of 2700ft. during the initial acceleration from the motor, the rocket began spinning very rapidly as seen in the Magnetometer graph (about 90 RPM) and accelerated to a maximum speed of about 489MPH (that is a pretty rough estimate, but probably not far off). The data stops just before the chute charge is fired at apogee which leads us to believe that the chute-charge is what damaged the disconnected the microsd card in the first launch. on landing we discovered the card got jammed too far into the holder. we concluded the that foam block on top of the card caused this and adjusted the foam for the second launch.
The second launch used a slightly more powerful motor which accelerated the rocket to a maximum speed of approximately 557MPH (about 70% the speed of sound) like the previous launch the rocket started to spin (about 94RPM). This time the chute charge did not disconnected the MicroSD card this time unfortunately the parachute deploying after the chute charge not only disconnect the card but ripped the holder almost completely off the board! we explained a bit about this in our Previous Instructable, but its worth noting in here that the G's that the board experienced at that moment are completely unknown to us. and far stronger than we expected.