On Wed, 20 Nov 2002, Randall Clague wrote: > Last night at the KISS III redux BBQ, we rejected the idea of testing > devices made for HPR use, since they're black boxes.
I see. I thought the baro gave an output something like a voltage proportional to sensed pressure, which is then used to determine altitude. If it's a black box that pops the chute at some preset altitude without giving some measurable signal you can monitor to see if it's affected by vibration then the story's completely different. If I understand correctly what the baro is doing, it measures pressure at some sample rate, and detects apogee when the measurements stop going down and start going back up again. If this is the way it works, then it might get spoofed at MECO if the location where the baro samples pressure has high speed air flowing past it[1]. This creates a low pressure zone so the baro reads lower than ambient - not a problem until MECO, at which point the rocket suddenly slows and the pressure jumps up a little. With KISS II the blowdown reduces thrust as MECO is approached, so the change in pressure would be less, perhaps zero. The flat thrust curve of KISS III makes MECO a more dramatic event, so this may explain why the baro that was fine on II suddenly started acting up on III. Even if the baro does not work as outlined above, it seems to me that the large change in forces at MECO between II and III should be the lead suspect for the baro misbehavior. ......Andrew [1] Since the whole rocket has high speed air flowing past it I wouldn't be surprised if the pressure inside the aeroshell was lower than outside. -- Andrew Case | [EMAIL PROTECTED] | _______________________________________________ ERPS-list mailing list [EMAIL PROTECTED] http://lists.erps.org/mailman/listinfo/erps-list
