So, you decided you want to launch something into near space. Awesome, but will your electronic components hold up, or will they crack under the pressure of sub zero temperatures? Build a thermal test chamber for pre-launch electronics testing.
Getting stuff *really* cold is difficult, dangerous, and lots of fun. Our group is preparing to send an autonomous glider up to about 100,000 feet, so we needed a way to chill our electronics to -70c to test their use before these edge-of-space flights.
Just using dry ice in a cooler will result in about 0c air. In order to chill air much colder, a fan is used to circulate the air to reach -42c. In order to hit -70c or colder, liquid nitrogen and a heat exchange (coil) is used.