High Altitude Balloon–Requirements

I’ve been toying with sending a balloon to near space. This idea has passed through my two youngest sons (neither really got interested), and now I’m looking at doing this with a NOVE group (NOVA is Scouting’s STEM program). I’m an assistant scoutmaster now and I think there are a few kids who might be interested. It’ll be winter before we can get the NOVA stuff off the ground, but meanwhile I’m planning.

I want the instrument package to do the following:

Experiments

• Temp sensors combine with altitude measurements to record the adiabatic lapse rate. As altitude increases the temperature should drop 5 degrees per 1000 feet.
• Audio sensors combined with altitude to demonstrate that in space, no one can hear you scream. As the altitude increases, air density decreases and sounds travel less effectively so the amplitude of an audio signal on a constant frequency should reduce.

Sensors

• GPS (working; proven in my TrunkTrackerino project)
• Temperature (working, both digital and analog)
• Audio (working somewhat—need to learn to eliminate all but the test frequency, so the sensor only grabs that freq and determines its volume)

Package

I have the option of building on Raspberry Pi or Arduino. I’ve chosen to build on Arduino simply because that’s what I started with—the Pi being a full-fledged operating system is a bit more complex, but will be used for version 2. Pi offers a variety of great stuff, from a very small camera capable of video to a more powerful CPU. For now, I’d like to keep it simple. NOTE: I have three Pi version B’s, one of which could become the base package. The B+ was recently released, though, and seriously offers a better platform: more USB ports (4), lower power drain, etc. I may end up purchasing one of those.

Since the Arduino can’t do video, we’ll be sending up a GoPro camera. I have an older camera, purchased specifically for the balloon project.

So the total package will be:

• Arduino Uno or Due (I have one of each)
• Shield stack of GPS shield w/SD card + radio shield
• {maybe} small hand-held to be used as a beacon
• Temp sensors
• Audio sensor (as yet unidentified)
• Go-pro camera
• Battery power for Arduino shield

Communications

As a licensed ham, I can use RF to transmit data back to earth. I want to transmit everything, in the worst-case chance that we don’t recover the instrument package. This means:

• GPS coordinates: lat, long, altitude, trajectory, speed, rate of ascent/descent.
• Temp/altitude pair
• Temp/amplitude pair

I’d also like the package to switch to beacon mode, or to include a beacon, once the package descends to within 1000 feet of land, so we can more easily recover the package upon arrival.

There are the specs. Next step is to close on the communications package.