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  • Author Author: mikedavis
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Raspberry Pi - 90,000 above the Earth

mikedavis

My college recently received a grant from NASA that allows us to pursue high altitude balloon projects.  I have written about this before, and asked about some potential ideas for experiments and sensors.

 

Today, in Lexington, IL we launched a balloon with some payloads on it.  This was our first launch, so our payload consisted of a pair of Raspberry Pi cameras, and an Arduino with the BMP Pressure/Temperature/Altitude Sensor.  Prior to the launch I tested the BMP sensor by taking it for a ride to the top of the Sears Tower. 

 

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The sensor worked.  The shape of the curve is what I would expect, though the actual altitude values surprised me.  I am going to have to look in to how that is calculated.  At any rate, the circuit worked, and one of my students built in a red light / green light system to let us know if things are working.  After one test, everything looked great.

 

A storm was brewing in Lexington, so we had to hustle to get our balloon out in front of it.  We used a 1600g balloon with about 14 pounds of lift for roughly 8 pounds of payload.  (The FAA limits us to 12 pounds overall.) 

 

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The sky behind us was getting pretty dark. 

 

Our materials were packed into a foam box, held in place with cable ties.

 

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Once we did the pre-flight check, and we were convinced everything was working, we let the balloon fly.  The pictures below are just a few of the more than 2000 that our two Pi Cameras took at 10 second intervals. 

 

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The balloon burst at an altitude of about 90,000.  In later pictures I can see the turbulence with a brief free fall before our parachute deployed.  Shortly after that, both cameras failed.  I think it might have something to do with the fact that the cameras were on the outside of the payload box, and it descended through a storm.  When it landed, both RPis were still on, but the cameras weren't taking pictures.

 

This was a tremendously fun project.  I have about six more planned over the summer, and we have more experiments to do.  We have some things to revise, but this was a great start.  Any guidance or suggestions from the community would be most welcome!

  • in reply to mikedavis

    Mike

    Thanks for the info.

    It's a project that the publisher of "The Shed" magazine here in NZ wants to do at a couple of schools.

     

    I have a lead on a minature aircraft transponder which will satisify Air Traffic Control, and will look for a tracker.

     

    I would suggest rotating the Pi 90 deg so that the card is subject to sideways forces.

    If you use the RPi2 (hint to nfusz) it features a microSD card which won't be subjected to the same force.

     

    A great project and good luck for the following ones.

     

    Mark

  • in reply to DAB

    Thanks, I forgot about that.  It was inside a foam box, but we may need to do some additional shielding.

  • in reply to mcb1

    We see a real advantage to using RPis and Arduinos as our data loggers in experiments like this.  They are inexpensive, and low power.  So every time we fly, we will probably have at least one camera as well as a number of sensors going up. 

     

    The batteries were 5V batteries that are actually meant to be cell phone chargers.  They are about the size of a lipstick container, and they have more than enough juice to power the devices during a 2-3 hour flight (which is pretty typical for us).  The flight time here was about 2.5 hours, and I have been able to make the RPi run on this for 5 hours with an active wifi connection while it takes pictures. 

     

    We tracked the balloon with a 900MHz tracking beacon.  We get coordinates on it during the entire flight.  My colleagues are more in to that portion of the work, so I will have to learn more about it.  We get a dashboard that continually updates over a live map, so we drive around getting closer and closer to the location of the balloon during its flight.  Our goal is to be there when it lands, and see it happen.  There is an antenna on our car that we power through the cigarette lighter. 

     

    When the balloon bursts there is a violent free fall before our parachute deploys.  I learned a little about securing things through that.  The RPi was snug against one of the walls, and the SD card was snug against the bottom.  Violent shaking caused it get pushed in, and come back out, ending the photos.  The arduino, survived totally intact.  With a working circuit, we are now ready to commit to a soldered prototype board.  I don't think I would use a solderless breadboard in all situations, but on a first go, I was surprise with its stability.

  • in reply to dragonstyne

    Yeah, I was thinking about how I would protect the camera without obscuring the view.  I think I might make a hole in the foam box and put a polarizing filter on the outside, flush with box.  I love the images, and while they won't be the focus of what we do, I think we are going to want to fly a camera every time.

  • Very cool post.

     

    Given the RPi sensitivity to light, I was curious if it would work at that latitude given the increase in radiation levels.

     

    If you are concerned about lightning, wrap the inside or outside with aluminum foil or copper screen so you make your own faraday cage.

     

    DAB