Another fun bit of data from our flight: We thought the stack might have drag-separated before the separation piston actually fired. This is actually fine and desirable, but we want to know when it happens. This is the first time we've had gyroscope data available on both airframes, so I just plotted and overlaid them looking for discontinuity:
https://docs.google.com/spreadsheets/d/1-ndBOg8UC9s2sIuud0pJeCVwaxRGb4DW5BR8iEubUyc/edit#gid=1476261848 Our stack definitely drag-separated around 9.5-10 seconds, long before the piston fired at 14 seconds. Neat! Casey On Sun, Jun 28, 2015 at 5:58 PM Casey Barker <[email protected]> wrote: > We launched a two-stage flight last weekend attempting to break 100K > again. The sustainer ignitor failed (incomplete pyrogen burn), but the > recovery was mostly successful, and we'll try again next month. > > In the updated design, we've got one TeleMega and one EasyMega each, for > both booster and sustainer. All four units worked great. Having a common > programming interface and terminal block across everything has really > simplified our lives! > > We had a couple of questions arise out of the flight. They're all about > sustainer ignition. To be clear, the TeleMega clearly fired it because the > igniter was partly burnt. I'm just trying to understand the data a bit > better. Here's the .eeprom file: > > > https://drive.google.com/file/d/0Bw8Fmi_7rzqMVnBLN2pjZFloUDA/view?usp=sharing > > 1) We used the tilt angle lockout on the sustainer ignition. I can see > this is the tilt relative to the pad orientation immediately before liftoff > (ao_ground_roll/pitch/yaw). I see the derived ao_sample_orient goes in the > OTA telemetry, but not the eeprom log, which instead gets the ground values > stored in the header along with raw r/p/y. Presumably, that's enough data > to reproduce the same math. Unfortunately, I'm not good enough at java to > discern how these get plotted in the UI. When looking at the .eeprom graph, > is the "tilt angle" still the angle vs. pad orientation? (Or is that a > silly question, because the gyros only give rates not absolutes?) > > I'm interested because the tilt angle graph seems to start at a flat, > non-zero value, roughly 3.7. We did launch at about 2 degrees off vertical > to compensate for wind, but I wouldn't expect that to show up in the plot > if it were relative to pad. > > 2) We also set a time window of >17 seconds and <19 seconds on the > sustainer ignition. (Really, we want it to fire at 17 seconds, but we > learned last year that we needed to close the window in the event the > sustainer was off-angle to prevent a misfire during recovery.) In the > eeprom file, the "Ignitor A" event shows up at ~17.2 seconds. However the > "Ignitor A Voltage" shows a brief drop around 15.5 seconds, and no sign of > a drop at the actual event. The other ignitor voltage drops line up with > their events, or immediately after. It seems strange that this one was over > a second early. I can't explain that... We know it burned. Did our wiring > briefly glitch right before? > > Also, possibly a minor bug: I don't see the ground r/p/y and aux ignitor > voltages in the csv export. (I should learn java...) > > Casey > > PS: I made the new avionics bays on a 3D printer. The bay models > themselves probably aren't useful to others, but I do have basic solid-body > STL models of both computers for evaluating fit and screw posts. I'll share > those when I get a chance. > >
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