Is there no ability to send a Hail Mary from the ground? Or does that fall under things that should no be done for legal reasons...?
W On Wed, Jun 18, 2014 at 10:16 AM, Keith Packard <[email protected]> wrote: > Steven Saner <[email protected]> writes: > > > It would, therefore, be cool if the altimeter could in some way detect > > the apogee failure and trigger the main ejection early. Obviously, this > > defeats the intention of the dual deployment, but I would much rather > > have to hike after the rocket than for it to be destroyed and/or come in > > hot and unsafe. > > I've thought about this a bunch, and in fact all of the Altus Metrum > flight computers have some idea of their descent rate on the way down > already; computed as a part of the Kalman filter outputs. > > The big issue is that with only a barometric sensor in a tumbling > airframe, you've got a *lot* of noise in the data, so computing anything > like an accurate speed turns out to be a bit tricky. You can see what > the output of the Kalman filter looks like by plotting a .telem file -- > the telemetry data includes the output of the Kalman filter while the > .eeprom file does not. We typically see a range of 50-100 m/s in speed > reported this way; that's what AltosUI or AltosDroid report for descent > rates, and you may have seen the crazy numbers from that... > > What we don't have today is a bunch of high-precision descent data. We > reduce the data recording rate during descent from 100 samples/sec down > to 10 samples/sec to save flash space. This means that most of the data > used for the Kalman filter on the rocket during descent is not stored > anywhere. This makes doing development pretty hard; without any real > data, it's impossible to test a filter on the ground. > > So, in order to make this work, we'd first need to hack the firmware to > capture high-rate descent data from a variety of flights. Then tweak the > Kalman filter parameters to generate reasonably smooth speed > data. *then* we could adjust the flight software to include a 'hail > mary' mode. > > -keith > > _______________________________________________ > altusmetrum mailing list > [email protected] > http://lists.gag.com/mailman/listinfo/altusmetrum > >
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