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#51
06-24-2020, 06:37 PM
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Thanks, that’s interesting, I find Q-jets light easily and quickly. I always wondered about the elevation difference, if I recall, the G138 might have been an H at 5600 feet. 
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#52
06-24-2020, 08:36 PM
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I think the S&T folks thought these were end burners, at least at first. That caused problems.
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__________________
For warranty questions & issues please contact Karl at warranty@aerotech-rocketry.com For customer service questions & issues please contact Jenn at customerservice@aerotech-rocketry.com AeroTech Consumer Aerospace Division of RCS Rocket Motor Components, Inc. 2113 W 850 N Cedar City, UT 84721 435-865-7100 (Ph) 435-865-7120 (Fax) http://www.aerotech-quest.com http://www.rocketmotorparts.com.com http://www.specificimpulse.com
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#54
06-25-2020, 01:54 PM
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Can't they apply a correction for altitude? That should be very easy to do.
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#55
06-25-2020, 03:36 PM
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Yes, but again there are differences in thrust stand calibration and accuracy, and the performance would also be slightly affected by local barometric pressure variations. A cumulative one or two percent error can easily kick you into the next motor class if you're trying to produce a full-impulse motor in a particular size.
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__________________
For warranty questions & issues please contact Karl at warranty@aerotech-rocketry.com For customer service questions & issues please contact Jenn at customerservice@aerotech-rocketry.com AeroTech Consumer Aerospace Division of RCS Rocket Motor Components, Inc. 2113 W 850 N Cedar City, UT 84721 435-865-7100 (Ph) 435-865-7120 (Fax) http://www.aerotech-quest.com http://www.rocketmotorparts.com.com http://www.specificimpulse.com
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#56
06-25-2020, 03:59 PM
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Gary- Thanks for taking the time to post here about Aerotech products; much appreciated. On motors tested with NAR S&T (well, TRA too, I guess), what +/- on total impulse are you allowed for a given motor within an impulse class before it is ‘rejected’ as being out of spec? I assume it is some percentage level. Just curious.... Earl
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Earl L. Cagle, Jr. NAR# 29523 TRA# 962 SAM# 73 Owner/Producer Point 39 Productions Rocket-Brained Since 1970
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#58
06-25-2020, 09:36 PM
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No, I am asking what percent error a manufacturer has to fall within either high or low on motor tests for it to pass motor testing. For example, if a ‘C’ motor is being tested and it is supposed to test out to 10ns total power, how many percent +/- from 10ns is the tested motor allowed to deviate and still be ‘accepted’ as a successfully tested motor. I know there are other parameters that are tested, such as delay burn time, etc., but to meet the motor impulse class it is supposed to be in, just how accurate (and I guess ‘repeatable’, because they don’t just test a single motor per motor type I don’t guess) does the burn have to be. He says above that certain testing conditions can throw things off by just a percent or two and cause a motor to fall outside it’s supposed motor class. I’m just wondering how ‘tight’ that performance window is. Earl
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Earl L. Cagle, Jr. NAR# 29523 TRA# 962 SAM# 73 Owner/Producer Point 39 Productions Rocket-Brained Since 1970
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#59
06-25-2020, 10:11 PM
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Ah I think I understand, sorry. Acceptable standard deviation.
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#60
06-25-2020, 10:15 PM
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You'd have to check NFPA 1125, IIRC. it seems to me that it was +/- 10% impulse and +/- 20% on time delay. Surprisingly, the NAR website does not have this info readily available. When I was on S&T decades ago, the manufacturers kept the impulse low as not to exceed the maximum.
Chas
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Charles Russell, MSgt,USAF (ret.) NAR 9790, Lvl 1 SAM "Balls Three"
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