ThrustCurve vs Aerotech Master Motor Matrix

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Dane Ronnow

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In researching motors that would work for my rocket, I'm finding discrepancies between ThrustCurve's data and Aerotech's Master Motor Matrix. I understand that both would not be exactly the same, but the differences are significant to me.

Ex: The G40 is listed in the AMMM as having a burn time of 2.38 secs. ThrustCurve lists it at 3.1 secs.

Can I accept ThrustCurve as the more reliable source for that type of data?
 

heada

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Check when the data was created as well if it falls within allowable tolerance. Thrustcurve uses the as-certified data whereas vendors, not just Aerotech, can use their data and there have been several versions of a motor (I'm looking at you G80!) so make sure you're looking at the correct version.
 

mikec

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I think that thrustcurve may or may not use the as-certified data; certainly I have entered data from vendor curves. There used to be a bunch of different files, but that was as confusing as helpful. May be some additional cleanup to do -- it would be best IMHO if thrustcurve had the data for the version of the motors currently being produced.
 

Dane Ronnow

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Check when the data was created as well if it falls within allowable tolerance.

AeroTech's MMM notes an update on 8/19/21. The G40 on ThrustCurve has no date listed (certified or otherwise) that I can find.

Interestingly, when I look at ThrustCurve's G40 page, the list at the top shows the 3.1 sec burn time. In the graph below the list, the curve stops at 2.3 secs. Is that like a compromise between the two conflicting source values? (Just kidding.)
 

heada

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Using the G40 as the example, Thrustcurve lists the last update as June 26, 2008 and has a link to the certification data from NAR which has a test date of Sept 30 2006. There has obviously been a revision to the G40 motor and Thrustcurve hasn't been updated. My question is, was the motor recertified when those changes were made? I don't know but if it was, then Thrustcurve can be updated with the new info too.

edit: looks like the summary info on the motor is wrong. The actual curve has 2.3sec burn time. There is a link to report incorrect data. I suggest clicking on that and report your findings.
 

Dane Ronnow

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Using the G40 as the example, Thrustcurve lists the last update as June 26, 2008 and has a link to the certification data from NAR which has a test date of Sept 30 2006.
I saw that date on the NAR data. I guess AeroTech's MMM, with an update of August, 2021, is probably more reliable than the ThrustCurve data [edit] on that particular engine. [/edit] That's assuming that when AeroTech updates that matrix, they revise every engine that changed.

I suppose you could always static test one yourself.
If money were no object, I might.
 

heada

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Cert data and AT data are match for burn time. Just the summary info on Thrustcurve's page is wrong. Click the link on the page to report the incorrect info
That data (NAR) is 15 years old.
And AT should be producing motors to the same spec (within tolerances) as the cert from 15 years ago. If they're out of tolerances, by design or otherwise, then the motor has to be re-certified.
 

smstachwick

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Stine had something to say about recertification rules, I’ll have to wait until I get home to consult the Handbook. I believe he said they must be recertified every three years but then again, the book is also from 2004.

Looks to me like an error on Thrustcurve. Those kinds of things tend to be pretty common that site, useful as it is.
 

Dane Ronnow

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Cert data and AT data are match for burn time. Just the summary info on Thrustcurve's page is wrong.
Looks to me like an error on Thrustcurve.
I'll use ThrustCurve's chart data (which agrees with AeroTech's motor matrix) of 2.3 secs, rather than the list data.

Thanks, everyone for your input.
 

JohnCoker

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If you find incorrect info, or a newer cert. doc, please use the link on the motor page to let me know. There are thousands of motors to keep track of, so we all have to help out when we fine issues.
 

mikec

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Newer fliers should be aware that AT has changed the design of many of their motors, especially the mid-power single-use ones (when they went from a phenolic (?) case to a molded case across much of the product line circa 2008-ish), changes to core sizes, etc. In many instances, of which the G40 is one, this changed the performance noticeably, but not so much that a recert was required.
 
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John Taylor

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If you find incorrect info, or a newer cert. doc, please use the link on the motor page to let me know. There are thousands of motors to keep track of, so we all have to help out when we fine issues.
Just wanted to say thank you John for Thrustcurve!!!
I use it every day practically. It is so easy and fun and I've found it to be accurate. Again, thank you.
 

JohnCoker

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Thanks guys, I updated the certified info and uploaded the linked cert. doc.

Sometimes the cert. docs disappear, so I've been working on collecting them and actually uploading them rather than just keeping a link. NAR is pretty good about this, but TMT and CAR keep changing their web sites so links break.
 

JohnCoker

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By the way, for reporting errors, I meant this link (which actually sends me an email):

Screen Shot 2022-01-22 at 9.29.21 AM.png

The Notes at the bottom were meant for other fliers for things like special requirements (seal disk, extended closure, etc).

If you can suggest different wording that would make it clearer, let me know.
 
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