Today was a weights & measures day – finding out how long batteries last, and how much parts weigh.
Stills Camera
Installed the CHDK firmware on the Canon IXUS camera, modified it to use less power, and tested that with a cat as the (very still) target! This confirmed that the tiny internal battery won’t be enough, so I ordered a 3xAA holder to mount external batteries. Tried different sizes of SD card and settled on a 2GB card which will be enough for the 2.5-3 hours in the air. Found some gotchas and completed this part of the launch procedure.
Video Camera
Tested the Kodak video camera with alkaline batteries (useless!) so that just confirmed that I’ll need to use Lithium cells. Calculated how much time the 16GB SD card will give (again, enough for the expected flight time).
Weights
Created a spreadsheet with the component weights. Total (a bit of a guess till the case is made and some other parts are in) is 900g. I have no doubt that will increase so I’m assuming 1kg total. With 3.3 cubic metres of helium in a 1000g balloon that will give us a burst altitude of about 31km reached in about 2 hours. With the return journey taking 30-40 minutes, this fits in nicely with the camera and video limits of about 3.5 hours.
Purchasing
Today I ordered the Lithium AA cells, the radio downlink transmitter, polystyrene sheet/glue/cutter for the capsule, and the balloon itself! The main item remaining is the helium gas, but that can wait till much closer to the launch date.