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A couple of thoughts (Bobk99 and I have also been corresponding via email, which is always the best way to reach me, since there are many threads on here I miss seeing like this until now).
1. Yeah, don't differentiate barometric data during the boost phase. That is such a noisy environment for pressure data, especially in terms of rate change. At high speed, the dynamics of air leaving the fuselage and the flow over and around the rocket are quite noisy. I have seen many setups where the altitude DIPS during boost (from ram effects) or peaks (from Bernoulli suction). Imagine differentiating that kind of data and coming up with a negative number when you expected a positive one. At slow speeds and apogee, all of that calms down.
2. I think it's very reasonable from an engineering standpoint to integrate accelerometer data at the end of boost phase to derive Cd, and I think any altimeter (including Ravens) can do a fine job of measuring that straight line acceleration. As I mentioned to Bobk99, if you want to be more rigorous you can always launch vertically and throw out obviously arcing flights. It would also help to launch on calm days and/or avoid overly-stable rocket designs to avoid cosine(flight angle) errors.
By the way, the Jolly Logic AltimeterThree in rocket mode samples at 200 S/s, and then losslessly bins it down to 20 S/s to save storage and display resources. So if you integrate the 20 S/s data, it's numerically equivalent to integrating the original 200 S/s samples (although you did lose the frequency info, but who cares about that).
1. Yeah, don't differentiate barometric data during the boost phase. That is such a noisy environment for pressure data, especially in terms of rate change. At high speed, the dynamics of air leaving the fuselage and the flow over and around the rocket are quite noisy. I have seen many setups where the altitude DIPS during boost (from ram effects) or peaks (from Bernoulli suction). Imagine differentiating that kind of data and coming up with a negative number when you expected a positive one. At slow speeds and apogee, all of that calms down.
2. I think it's very reasonable from an engineering standpoint to integrate accelerometer data at the end of boost phase to derive Cd, and I think any altimeter (including Ravens) can do a fine job of measuring that straight line acceleration. As I mentioned to Bobk99, if you want to be more rigorous you can always launch vertically and throw out obviously arcing flights. It would also help to launch on calm days and/or avoid overly-stable rocket designs to avoid cosine(flight angle) errors.
By the way, the Jolly Logic AltimeterThree in rocket mode samples at 200 S/s, and then losslessly bins it down to 20 S/s to save storage and display resources. So if you integrate the 20 S/s data, it's numerically equivalent to integrating the original 200 S/s samples (although you did lose the frequency info, but who cares about that).