I continue my quest to study the rotation behavior of the FunCube, and frankly that study generates more questions and theories than answers; and that's a good thing. I have tried to generate a visual image that helps to explain the behavior that is illustrated in the graph of the data (note the rotation rate on the Y-axis is a log scale to help deal with the range of rotation rates to date).
Previous I had developed a turn-table thingy that can be used to demonstrate the range of rotation rates expected for the Fox constellation of satellites. The turn-table is basically a geared DC motor with a controller and GUI. The motor rotation rate is controlled with PWM and an H-bridge, it has a maximum RPM of 2, the minimum depends on the stall characteristics, but is slow enough for this application.
So what I did was divide the life span of the FunCube into 25 day sections and picked a representative rotation rate for each 25 day interval. For the video, I set 10 seconds to scale the 25 days, and programmed the turn-table to rotate at the representative rotation rate for that segment of the life span. In the video, you see a portion of the GUI with the day in orbit and the rotation rate in RPM during that 25 day segment, and the FunCube model on the turn-table. The video can be downloaded from here: https://www.dropbox.com/l/9Wo0by0lYW4knaxkSNrIqu
Admittedly it is sort of like watching grass grow, but perhaps it might be useful for some students to visualize the orders of magnitude of the rotation rate, and just what is being attempted by monitoring that rotation rate. I think some "bird walk" questions for discussion might be: why rotate the satellite?, what rotation rate is too fast or too slow?, what happens if it rotates too fast, too slow, or not at all?, what are the forces involved with slowing it down and speeding it up?, are there any connections or interaction between these forces?, just to mention a few.
I still maintain that the FunCube is a resource that just keeps on giving. I know I have expended a bunch of the few remaining brain cells I have left contemplating the wonders of the FunCube and I am in the early stages of developing follow-on experiments for possible time on orbit, and certainly for on-the-bench work in the classroom. There are probably better ways to expend those brain cells, but then again, those ways are probably illegal someplace.
Mark, WA8SME, firstname.lastname@example.org
, [The Connecticut Yankee in the FunCube Court...sorry, gotta try and lighten this thing up a bit.]