High Altitude Ballooning - Looking for Projects

It has been an exciting few months.  Don't let the lack of blog posts fool you.  I have honestly just been too busy to write anything.

Earlier this year, the City Colleges of Chicago received a grant from NASA to do some high-altitude ballooning (HAB).  The vast majority of the money we receive will support undergraduates with stipends so they can build and design experiments that will be conducted 30,000 to 90,000 feet above the earth.  We have our first crop of students, and they are ready to get moving!

Prior to any of our materials arriving, I dug out some Raspberry Pis and walked them through the construction of a temperature sensor. I thought this was a good place to begin, and it seemed relevant.  No matter what kind of experiments they want to do, they will most likely collect information on temperature and pressure.  We used the DS18B20 sensors, and the gspread library to keep track of our temperatures.  The big 'ah-ha' for the students and faculty was that the small device here was taking measurements and reporting them to another computer.  It was very exciting.

I am now looking for some experiments that we can do in a weather balloon.  Here are the limitations:

• Total weight, including balloon, parachute, and tracking equipment, must be under 12 pounds.
• The balloon will be exposed to temperatures as low as -70 C.
• The balloon will be exposed to pressures as low as 0.02 atm (basically 1/50 of the pressure we feel on the surface of earth).
• The entire balloon flight is typically around 3-5 hours depending on weather and other conditions.

Things that we will require are:

• Sensors that can record to some kind of permanent memory (like an SD card or external drive).
• Sensors that can withstand the conditions described above.
• Experiments that can survive a 17 mile fall back to earth (it should be robust).  We have a parachute, and that slows it down nicely.
• Inexpensive
• Light-weight

I am very familiar with things like the Raspberry Pi and Arduino, and I feel pretty confident that I could find a way to make something work.  My students show a lot of aptitude as well, so they will most likely lead in this area.  We like the open source electronics because they are inexpensive and light weight.  It also seems like any kind of sensor we could be interested in would be able to work with Pis or Arduinos. 

I am interested in doing some radio spectrum work and doing some speed of sound measurements as the balloon goes up.

If any of the engineers on this forum would like to weigh in, point us towards resources, or flat out give some help, I would be most appreciative.  Scanning the internet shows me that there is a lot of information out there.  I think this community and this forum does a good job of cultivating that information and distilling it into something that is really useful.

Our first launch will be April 24th.  More news to follow!