Old K1100 Motor Data??

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Sandy H.

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I just wanted to check and see if there was any wrasp data (or similar) for an AT K1100 from 2005. I see the data on Thrustcurve.org is from 2006, which is pretty similar, but I also see that the original summary data listed on thrustcurve calls it a 14%K while the data files are closer to a 25%K.

We had a flight this weekend that was about 25% low in altitude (1350 vs 1700ft) and I wanted to try and find the source for the error in simulation vs actual. The motor lit instantly, so I believe it was in good shape and we re-weighed the components to make sure we didn't mess that up, but so far, things look OK. The flight profile was pretty vertical and to lose that much altitude would have been obviously non-vertical (40 deg approx).

I do have data from my Raven, but I've never figured out how to generate motor parameters from the flight data. If that will be helpful, I can attach that. The rocket weight without motor was 27.7#.

Any help on locating an older thrust curve or other suggestions would be appreciated.

Thanks!

Sandy.
 
You get the motor thrust curve by taking the acceleration in the rocket axis, subtracting or adding gravity if necessary (depends on the calibration, I'm blanking right now for which the raven records), multiplying the curve by the mass of the rocket, and then subtracting drag (which is a function of velocity, which is a function of time). To be more accurate you should also take into account the changing mass as a function of time. While the best approach might be to do this in matlab or similar data-handling software, it can probably be done just fine in excel.
 
; Converted by CONVALT4 Version 4 on Mon Dec 26 15:29:46 1994
; Input data courtesy Rogers Aeroscience.
K1100T 54 410 6-10-14-18 0.791400 1.426100 AEROT
0.000 1627.568
0.100 1244.550
0.400 1196.645
0.800 1124.899
1.000 1077.039
1.100 1053.064
1.200 1029.089
1.400 660.528
1.500 119.651
1.600 0.000


-->MCS

.
 
Thanks for the information, guys.

CCotner: I'll try to work out the motor thrust, but the kicker for me, I guess will be estimating drag. Would looking at velocity after burnout be the best clue as to drag?

MCS: Those values are pretty similar to those available on thrustcurve.org, so I guess no major changes were documented. After I posted, I remembered the thrust curve was printed on the instructions (DUH!?!?!?!) and it is also similar. I mainly wasn't sure if there had been a major change like has occurred with some other motors in the past. I guess the answer is basically 'no.'

Rocketjunkie: Thanks for the data point. I'll scaled the curve 86% to get to 1350 NS and now the altitude in the sim is 1260ft, much more in line with what we saw.

Thanks for the help!

Sandy.
 
Rocketjunkie: Thanks for the data point. I'll scaled the curve 86% to get to 1350 NS and now the altitude in the sim is 1260ft, much more in line with what we saw.

You can also tweak the motor file, until the acceleration curve from your simulation matches your Raven data. This should give you a rough approximation of actual motor performance.

Reinhard
 
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