Sunday, September 30, 2012

Thermal Test

To ensure my the reliability of my flight hardware, I conducted a test where the conditions at 100,000 feet were simulated.  To do this, I used a cooler, a 12 pound block of dry ice, a mounting system, and a temperature sensor.

Here you can see the big block of dry ice I used to get down to the desired temperature.

Here you can see the flight hardware packed inside the polystyrene foam container.  The Geiger Counter, DAQ system, and camera were all placed inside and turned on.  I placed a couple pieces of Uranium glass inside so the Geiger Counter had something to record during the test.

This is the setup inside of the cooler.  The best way to get really low temperatures around the box was to place the block of dry ice above it.  I used some more pieces of polystyrene foam to mount the dry ice above the box.  You can also see the temperature sensor that I used to derive the temperature inside the cooler.

 This is a picture of the box before placing the dry ice on top.

Now the piece of dry ice is placed and ready to go.

I put the cooler lid back on with the temperature sensor wires connected.  The equilibrium temperature inside of the cooler and outside of the flight hardware box was found to be -36 degrees Celsius, right around what I expect the temperature at 100,000 feet to be.  After two hours, a thermal equilibrium was established with a temperature of -5 degrees Celsius inside the flight module.  The heat generated from the electronics and excellent insulation properties of polystyrene foam aided in establishing this equilibrium.  At the conclusion of the test, all of the electronics were still functioning perfectly.

Overall I was pleased with the performance of the electronics under the conditions.  The next task will be to perform the same experiment with hand-warmers placed inside the flight module.  In doing so I hope to establish a factor of safety by running closer to the middle of the operating temperatures of all the electronics.  Further, temperatures will actually be lower than -40 degrees Celsius on the journey up to 100,000 feet, so having some active heat source other than the electronics themselves will be critical.

Thursday, September 27, 2012

Geiger Counter

Here you can see me testing out the Geiger Counter we just got in.  It shipped with some naturally radioactive material that you can test with, namely uranium glass.  It's a little hard to see, but when a beta particle is detected, a little red LED lights up on the probe assembly.  This sensor is capable of detecting both beta and gamma radiation.

Monday, September 17, 2012

Raspberry Pi

Today I received my Raspberry Pi, which is basically a computer that will go up with the real flight hardware. Personal computers are now the size of credit cards- it's pretty amazing!

Sunday, September 16, 2012

Progress Update

All of the internals for the first launch of the balloon have been ordered.  When they arrive, I will assemble them and find out the final weight of the flight hardware.  This is important for a number of reasons:

  1. If the final weight is less than 4 pounds, some regulations seize to apply- to see more information about the regulations that apply to unmanned balloons see
  2. The weight will be an important factor in determining the size of the balloon and parachute needed to reach the desired altitude and land safely
  3. The lighter the flight module, the more potential I have to add ballast that will stabilize the module during flight
There are some complications here- the whole point of doing a test flight is to learn something for the real launch where there will be hardware used to measure gamma radiation.  So I may end up adding weight just to better simulate what the next launch will be like. 

Stay tuned for impact and thermal testing this week.

Sunday, September 9, 2012

Machining the Dummy Balloon Housing

In the picture above you can see how the dummy balloon housing is manufactured.  I first cut at piece of high density Styrofoam to a shape that was close to my model.  I then machined it down to specifications by hand.  It's not perfect, but it should function adequately.  This version will be used first to do a thermal test and then an impact test.  Posts detailing the procedures of those tests will follow.

Thursday, September 6, 2012

Flight Module for Dummy Balloon

Here is an image from CAD of the flight module coming together- a work in progress.  I plan on toying with the idea of making the casing in the shape of a raindrop.  If I add some ballast (can't afford to add too much), this should make the module always point in the direction the wind is coming from and minimize the extent to which the module gets knocked around.  Just a Styrofoam box for now though- it will be much easier to manufacture for testing purposes.  The rain drop design would probably require some time with a lathe to really get a good shape going.  Stay tuned.


Stage 1

The first step is to prove that we can successfully launch and retrieve a balloon that has achieved our desired altitude.  Therefore the first launch will be a "dummy balloon," where only a camera and GPS recovery hardware will be sent up, and perhaps a couple other sensors to get a better idea of the conditions the inside of our module will see.  On the journey to the stratosphere, we anticipate seeing temperatures as low as -70 degrees Fahrenheit and atmospheric pressure about 1% of what you see at sea level (almost a vacuum).  The location transmitting devices then, must be able to survive these conditions in order for us to retrieve the module.

Once we prove that we can successfully launch and retrieve a module, the experimental flight hardware will be launched.  Manufacturing of the dummy balloon has already begun, stay tuned!

So it begins!

My name is Matt Pleatman, and I'm a senior undergraduate student at Duke University.  This blog will detail my journey to send a weather balloon to "near space" that will hopefully capture scientifically valuable information about high energy particle radiation during thunderstorms.  This project is being completed as an independent study.

None of this would be possible without my adviser, Dr. Steven Cummer, the Jeffrey N. Vinik Associate Professor in the Electrical and Computer Engineering Department at the Pratt School of Engineering.

Let's get started!