I remember reading in HPR, a few years back when the small flight computers started using altimeters, that many flights were experiencing premature chute deployment. The problem apparently was as the rocket went transonic the shock wave would travel down the body of the rocket, when it pasted the altimeter port the flight saw a pressure fluctuation that it registered as passing apogee triggering the ejection charge. The flight computer manufactures played
with their algorithms to try to overcome this problem. I know of at least one RRS rocket that flew with one of the improved flight computers that also experienced premature ejection. I always thought if you used a static pressure tube (closed end tube with holes drilled radially around the circumference near the tip) extending forward of the nose cone instead of using a static pressure port on the side of the rocket most of these problems would disappear. You still have to account for the initial shock wave to pass the ports of the static pressure tube but the improved flight computers should be able to handle this easily. I think they have problems due to several shock waves developing along the rocket body. References: see pdf page 15 which is report page 12 http://naca.larc.nasa.gov/reports/1958/naca-tn-4184 http://naca.larc.nasa.gov/reports/1958/naca-tn-4184/naca-tn-4184.pdf David Weinshenker wrote: > [EMAIL PROTECTED] wrote: > > > > Assuming we don't find a clear cause of the baro failure, would it be > > possible to have one timer 'enable' the baro sensor, with the electronic > > provision that if the baro sensor already says 'fire' at that time, we > > ignore it and fire a second or two later? I know we can do this with > > some electronic modifications, but unsure if our stock system could. > > > > So, assuming the simulations show a max altitude at 25 seconds, we > > set the first timer (baro enabler) at 23 seconds, and the backup timer > > at 27 seconds. > > > > Dan > > > > In a message dated 11/13/2 10:22:37 AM, [EMAIL PROTECTED] writes: > > > > << Actually, there was just the one timer (the RDAS in timed > > recovery mode) - the baro altimeter was simply disabled > > (didn't connect an ejection charge or install a battery). >> > > > > _______________________________________________ > > ERPS-list mailing list > > [EMAIL PROTECTED] > > http://lists.erps.org/mailman/listinfo/erps-list > > The current system doesn't have that functionality. > (There is the possibility to set a few seconds > of "lockout" delay on the altimeter, but not to > set up that kind of cross-coupled conditional logic > between the two units.) > > -dave w > _______________________________________________ > ERPS-list mailing list > [EMAIL PROTECTED] > http://lists.erps.org/mailman/listinfo/erps-list _______________________________________________ ERPS-list mailing list [EMAIL PROTECTED] http://lists.erps.org/mailman/listinfo/erps-list
