Post your Raven FIPa files here

Discussion in 'Rocketry Electronics and Software' started by cvanc, Oct 8, 2012.

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  1. Oct 22, 2012 #61

    Rocketjunkie

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    The rocket was supposed to take off on the 2 J500's, then airstart all the rest at about the same time (Thermalite fuses). Only 1 J lit initially, thrust was too off center for stability. The rocket never became stable, travelled less than 100 feet, and landed flat, completely undamaged. The Raven never fired any deployment charges nor beeped out an altitude.
     
  2. Oct 22, 2012 #62

    maxvelocity

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    I used J tek e matches for both charges.
     
  3. Oct 23, 2012 #63

    AHansom

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    Well here's my latest flight. Shredding a 6" King Kraken on a M-2020. One thing I'm kind of worried about is the ejection charges didn't go off. Oh well, good thing they weren't needed

    View attachment os.FIPa

    Ekraken1.jpg
     
    Last edited: Oct 23, 2012
  4. Oct 23, 2012 #64

    AHansom

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    This was a exciting flight also. I sure like when its just a regular old boring flight :wink:

    A pair of I-284's airstarting a pair of H-112's

    View attachment da.FIPa

    krakenroc1.jpg
     
    Last edited: Oct 23, 2012
  5. Oct 23, 2012 #65

    GRIFFIN

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    Last edited: Oct 24, 2012
  6. Oct 24, 2012 #66

    cvanc

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    Brutal shred and very sad to see such a nice rocket damaged.

    I totally don't get the velocity data in your file. It says you went 900+ miles an hour for more than two continuous minutes. Which obviously did not happen. I have no idea what might have caused this.
     
  7. Oct 24, 2012 #67

    cvanc

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    Another gorgeous rocket! I'm gettin' a little jealous LOL. Is that Black Rock?

    Is this the same Raven as the Kraken flight? Again the velocity data seems very odd. It reports you were going NEGATIVE mach 2.2 at the same time your baro data says you were still headed uphill. I don't get it.

    Calibrate the accelerometer, maybe? (have you ever done that?)
     
  8. Oct 24, 2012 #68

    cvanc

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    Oh wow. Fifty-six gees at thirty feet off the ground! Damn. And it was unscathed? I think I wanna know what glue you use :surprised:
     
  9. Oct 24, 2012 #69

    AHansom

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    OOOPS!!!

    :bangpan:I posted the wrong file:bangpan: That was a test run on FIP. before the flight. Heres the real file.


    I have calibrated it before but it cant hurt to do it again. After the last couple of flights its been upside down more than rightside up!!!

    This was during a ROC launch a couple of years ago at Lucerne Dry Lake

    http://www.youtube.com/watch?v=248ZLdN4Gis

    View attachment nsl.FIPa
     
    Last edited: Oct 24, 2012
  10. Oct 24, 2012 #70

    AHansom

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    I don't get it either. Maybe that's why the fins came off!!!!
     
  11. Oct 24, 2012 #71

    cvanc

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    OK, that seems much more like you'd think it should be. Looks like a nice clean flight. 2 things are noteworthy...

    1- Your battery dropped to just below three volts when Pyro #3 lit the airstarts. The current did not seem bad (just under six amps). Not sure what kind of battery or wiring you have, but it implies some internal resistance in the battery or in the battery wiring harness. If it had dropped just a little lower it might have been marginal? Don't know.

    2- Again there is this roughness to the baro data on descent. But take a look at lateral G's & baro data overlaid. They track each other. Does this show the rocket was spinning or maybe swinging side-to-side during descent? Really interesting stuff there.

    Thanks for posting (thanks to everybody for posting).
     
  12. Oct 24, 2012 #72

    GRIFFIN

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    Proline 4500 high temp epoxy. Surface mounted fins. Pic's added to original post.

    Next flight KBA L2300 Thunderstruck 4
     
    Last edited: Oct 24, 2012
  13. Oct 24, 2012 #73

    rocketboy16

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    "Since there wasn't anything visible in the lateral axis before the disintegration, that indicates that it wasn't the usual shred cause of coupler failure, instability, or fins. That plus the consistent positive-G impulse during the burn suggests to me that it was a CATO. "
    --Adrian A.


    Adrian I had talked to you fairly extensively about this flight. What we came up with was, secondary altimeter fired apogee charge at mach ~1.3 still during the burn. This was determined because of the BP residue in the bay; this is the first main spike in axial acl. The booster still motor cooking away then reached the end of the 50(ft) of shock cord and proceeded to sheer the 4000(lbf) kevlar; this is the second large spike of axial/lateral acl. This high G load shook the main chute out and rippped it to shred, the GPS was removed from the nose cone and taken off of its sled.
     
  14. Oct 24, 2012 #74

    AHansom

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    Thanks for the input

    I downloaded the other Raven from the shred. one Raven s #36 and the other is #1414. They both seem to have a similar straright line velocity reading after the shred. Niether raven fired any charges during the flight but they both simulated fine on the desktop before the flight. Havn't done any sims yet to see if they still workl

    look forward to some feedback on whats happning

    View attachment 1414OSkraken.FIPa
     

    Attached Files:

    Last edited: Oct 24, 2012
  15. Oct 24, 2012 #75

    cvanc

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    Yeah, I'm not undertstanding this at all. #1414 shows your rocket going faster and faster after breakup, until it finally hits over 4,000 miles an hour 2 minutes into the flight (remember it shredded about 3 seconds in). That makes no sense.
     
  16. Oct 24, 2012 #76

    Adrian A

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    An accelerometer doesn't know which way it's pointing, so it couldn't tell that it swapped ends after the breakup. After that it interpreted a bunch of drag deceleration as if it were more thrust that was making the rocket go faster, and so it never met the Mach lockout condition.
     
  17. Oct 24, 2012 #77

    Adrian A

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    Wow, that data is so clean it's as if it were a simulated flight! :rolleyes:
     
  18. Oct 24, 2012 #78

    Adrian A

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    It looks like a 9V battery from the battery voltage plot. A 9V battery has a lot of internal resistance, so when the igniter is shorted out as the motor ignites, you'll see the battery voltage drop near zero. The Raven has a hold-up capacitor so that if the battery voltage had dropped to zero for the whole ignition pulse (and several more in a row) then the altimeter would have stayed running and turned off the switch a the end of the 1-second pulse.
     
  19. Oct 24, 2012 #79

    AHansom

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    Thanks for the great information Adrain.

    Would that account for the charges not firing?
     
  20. Oct 24, 2012 #80

    cvanc

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    I'll chime in on that; I think the answer is yes.

    At factory defaults, Mach lockout is active above 400 feet per second velocity. And if the Raven was in a state where it thought it was continuing to go faster & faster it obviously would never drop below that threshold. So any output channel that had the "Vel1" parameter active would be suppressed. (right, Adrian?)
     
  21. Oct 24, 2012 #81

    Larry Curcio

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    Am I doing something wrong? I'm seeing maximum integrated acceleration altitude of zero, and minimum of -17738 feet.
     
  22. Oct 24, 2012 #82

    cvanc

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    The thread is gettin' a little confusing. What is the name of the file you're looking at? I'll double check it here...
     
  23. Oct 24, 2012 #83

    AHansom

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    Sorry about that. Go back to post #69 and it will make sense
     
  24. Oct 24, 2012 #84

    Larry Curcio

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    OK. Much better. 4928 feet integrated v 3857 barometric. That's big, but reconcilable. Significant interstage delay. Did it arc over much?
     
  25. Oct 25, 2012 #85

    Cpig

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    Excellent idea cvanc. Here is one that I'm still confused about. The log shows my apogee charge going off at 13.7 secs just at/shortly after apogee. The video shows the same charge going off at the same time (if you time the video out from lift off to charge going off around 13.7 secs +/-). The problem is that you can clearly see that actual apogee occured at least 5 secs before the apogee charge blew. You can see the rocket in a high speed dive for at least 5 secs after reaching apogee (seemed a lot longer when I was watching the actual flight). I have a 1/4 inch hole drilled for my barometer readings but I'm wondering if apogee was misread causing a late ejection?

    The video page may take a minute to load.
    http://www.cosrocs.org/all other videos/2012videos/chiliblaster/dualdeptalon.mov

    View attachment T3 I287SS 29JUL12 2100ft.FIPa
     
  26. Oct 25, 2012 #86

    Adrian A

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    I looked at the video, and I think that a lot of the apparent lateness is from the optical illusion you get when the rocket is overhead and flying upward and away from you with a decent horizontal apogee speed, and it looks like it's descending. As it arcs over, the curvature of the flight even makes it look like it's speeding up when really its just that you're getting a more side-on view. 1/4" is a pretty huge vent hole, so I doubt that the internal pressure was lagging much. The accel-based apogee detection agreed with the baro data as well.
     
  27. Oct 25, 2012 #87

    cvanc

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    Well, I dunno. I'm no expert. I started this thread because I wanted to learn a lot more about mining this data to get to the facts. Here's what I see in your file:

    Your launch site is about 5,000 feet above sea level? (Colorado?)

    Accell velocity data got to zero about 12.6 seconds

    Baro says apogee was between 12.6 & 13.2 seconds - so it matches the accelerometer well
    (if the vent holes were not right wouldn't it force accel & baro data to disagree?)

    Apogee channel event went off at 13.7 seconds as you say, so ~1 second after both sensors sensed apogee

    How was your Raven programmed for apogee trigger?

    What ematch did you use for apogee? Powder type? Amount? Enclosure?

    Here's a far out idea: Were you the one making the video? Maybe your position relative to the flight gave a bit of an illusion that it was on the way down when it was still more-or-less horizontal at apogee? Again, I dunno. But I have seen something like that. What do you think?
     
  28. Oct 25, 2012 #88

    cvanc

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    I did not time the sound of the charge going off in the video, but he reported it lined up with the Raven data pretty good. The apogee (baro) was almost exactly 2100 feet. I looked at how long he spent within 50 feet of that just to get an arbitrary sense of how long it was going more horizontal than vertical. It got to ~2050 feet at about 11 seconds and fell back to 2050 feet at almost 15 seconds. So it spent a long time near apogee. Maybe this 'hang time' explains it?
     
  29. Oct 25, 2012 #89

    Adrian A

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    Summary: 1. Don't read too much into the physics of a simulated flight. 2. The accel-based altitude normally stops being more accurate than the baro-based altitude early in the flight. 3. The displayed measurements in the brackets were calculated in post-processing the recorded data, rather than on-board, and so were spoofed by a condition that's specific to performing the simulated flight with the altimeter upside-down.

    For the gory details of 1&3: There are a few things going on here. The effect of the test mode in this case is complicated by the fact that the Raven was upside down when the simulated flight took place. That made a constant reading of -5Gs, so the Raven figured it was upside down and changed the sign of its acceleration. It also adjusted its offset to compensate for what looked like an offset error. Then when the test mode was turned off, that made an apparent 4 Gs, and it interpreted that as a liftoff type of acceleration, but it took awhile for the velocity to catch up to where it was positive, and in the meantime the original G reading was not recorded. Thus the post-processing sees the initial G reading of about 4 Gs and assumes that's an offset to be subtracted from the rest of the measurements. That threw off the post-processed velocity and altitude. The on-board velocity estimate "Velocity (Accel-Ft/sec)" a long averaging period before liftoff detection to get a better estimate of the prelaunch accelerometer readings, and you can see that it performed fine.

    The discussion behind summary point #2 is probably more interesting:
    The accel-based apogee altitude is very sensitive to nonlinearity and resolution errors in the accelerometer and the microcontroller A/D converter. Not to mention flight angles and coning that can also contribute to errors in the accel-based altitude error. So the accel-based altitude really should be ignored after the first part of the flight. So why display it at all? It's actually pretty good early in the flight, particularly during the initial boost when shifting parachutes, accelerating air columns, high angles of attack and Mach transients can make the initial baro readings pretty useless. In fact, you can often measure the length of your launch guide rail or tower by zooming in and looking at the lateral accelerometer to see when the launch rail stops bouncing the rocket around, and comparing that to the accel-based altitude at that time. For example, look at the NSL kraken accel data in post #69, and you can see that the rail was about 6 feet long. The Oh-S-Kraken accel data in post #74 shows the rail was about 10 feet long. If you want to tell people at what altitude your rocket broke the speed of sound, the accel-based altitude is the one to look at.
     
  30. Oct 25, 2012 #90

    AHansom

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    He's Good!!!

    Amazing how much info is there.
     
    Last edited: Oct 25, 2012

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