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REALLY need help understanding AeroTech nomenclature...

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soopirV

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This is seriously embarrassing to have to ask, but I'm at a loss, and I'm sure it's because I'm thick. I'm posting here because the example I'm going to use is MPR, but I am a successful L2, yet maybe a good education on this question will help other MPR folks who are not yet across that threshold. Enough pussyfooting: WHY IS IT SO HARD FOR ME TO UNDERSTAND AeroTech NAMING CONVENTIONS?
If this has been posted before, I apologize, I couldn't find a cohesive answer- just bits and pieces here and there...if there's a sticky, then I'll eat a reload, but maybe there should be?

Case in point- doing an inventory on my current reloads: I have a few F12s, a few F39, a couple G64 and a G76, so...a few 24/40, a few 29/40-120. I begin to sim out some of my rockets to see which motors I should order to fill gaps and have fun. I see that the AT F39 (24/40) and the AT F40 (29/40-120) are REALLY close on average impulse, yet produce wildly different results. I look at the datasheets and see that the F39 is 50N Total impulse, versus the F40's 80N total impulse (making it a full-F). This COMPLETELY makes sense to me, after looking at the datasheet.

Now a digression, albeit brief: I was a chem major in college for exactly 2 semesters, until Calc 3 kicked my butt, so math is NOT my strong suit. That said, I'm somehow intelligent enough to diagnose cancerous cells using their appearance under the microscope and protein and genomic tests...so I don't think I'm actually dumb, just...thick...but I went with Cessaroni for my high power exploits because it made sense to me
Using almost the same example from CTI: they have two 29mm reloads, both F36 if you look at it the way AT does. CTI, however, includes the total impulse in the name of the reload, so a flyer can simply calculate the burn time without datasheets or personal experience. This, in turn, can give a sense of maximum impulse, and to a degree for us noob fliers, flight profile.

I'm not saying that one is better than the other, or that datasheets are not needed- I am asking because I want to be sure I'm not missing any tricks with Aerotech, little hints or shortcuts that get me to the same level of comfort.
Aside from knowing Burn Time off the bat, I struggle with predetermining which case I would need to fly a particular AT reload. This is mitigated on the CTI front because I know I have a full set of 29mm, 38mm, and half a set of 54mm (up to 3g) by using their simple spacer system, which AT has adopted...but if I ask to borrow an AT case from a friend, I do not know how to reliably tell which case I need for my given load. By way of example, if I had an I154 reload, and looked only at the curve of the motor, it would show a total impulse of 360N, but apparently I'd need a 480 case. Dissimilarly, and still within the range of the L2 rocketeer, is the 54mm J415- it's total newtons is 1280, which must mean it needs the 1706 (really?) case! But no, it's fine in the 1280. So it's not a "greater than or equal to" scenario each time".

I'll freely admit, CTI is not without it's nomenclature faults, and that is why I'm not here to pick on AT, just want to learn how to enjoy AT as much as I do CTI. I find peace (and maybe this is because of my thickness) that I can look at a CTI datasheet and say, "hmmm...38mm 3G, I can fly that!" I want to do the same with Aerotech...earnestly.
 

CzTeacherMan

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I'm a CTI guy myself...
I think of the hardware in terms of grains constantly. And I'm slowly building a vocabulary for the number of grains to Newton designation on the hardware...
Basically, I just look at the 29/40-120 as grains. 1 grain is an E, 1 long grain is an F, two grains is a G. 40-120 meaning the case is made for loads of total Newtons from 40 to 120. Same basic idea on the HPR stuff... The 29/180 has loads near the 180 total Newtons range. Using that, you can approximate burn time from avg Newtons
EDIT: I think my explanation below makes much more sense... maybe?
 
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CzTeacherMan

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I've been wanting to make this chart for myself for some time... Thanks for giving me the excuse to do so!...
Basically, When thinking of CTI's "Grains", you can kind of think of it as a number of propellant grains in the case. It's not necessarily the actual propellant configuration within the propellant package (think of the 54-6XL K300, it's just one large grain), but that gives you a sense of Total Newtons. Add another grain of propellant, add another grain's worth of total thrust. When considering the numbers on the Aerotech hardware, it's basically a statement of the total Newtons that can fit in the casing. Again, that's not an exact translation, but it can give you a sense of Total Newtons of the motor. So, for example, a motor filling the 38/720 casing has somewhere in the ballpark of 720 Total Newtons. Sometimes, it's far short of that, depending on the load (I600 is only 600 Newtons, but the J500 fits in the same casing and has 723 Total Newtons). So, if you're trying to compare CTI hardward to Aerotech hardware designations, and you're a CTI-minded flyer, you can translate Aerotech numbers to "grains." If you're an Aerotech person trying to grasp CTI's designations, think of each "grain" as an approixmate chunk of Newtons.
CTI-AT.jpg


EDIT: This one is more accurate...
CTI-AT 02.jpg
 
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noffie79

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This is something I've been trying to learn as well. I absolutely love my AT 29/ 40-120 case. It gets used probably more than any other case I have. But for high power, I've found myself going with CTI, because I understand it better. But, I'm venturing a little farther with AT, and now with this chart, it all makes a lot more sense. Thanks Erik!
 

Banzai88

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Took me a year to wrap my head around this from the CTI flyer wanting to branch out into AT loads. Thanks for the chart, it should be a sticky at the top of one of these forums. The AT catalog is so out of date it's almost worthless to a newb who doesn't even know enough to know what he doesn't know.
 

eggplant

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I've been wanting to make this chart for myself for some time... Thanks for giving me the excuse to do so!...
Basically, When thinking of CTI's "Grains", you can kind of think of it as a number of propellant grains in the case. It's not necessarily the actual propellant configuration within the propellant package (think of the 54-6XL K300, it's just one large grain), but that gives you a sense of Total Newtons. Add another grain of propellant, add another grain's worth of total thrust. When considering the numbers on the Aerotech hardware, it's basically a statement of the total Newtons that can fit in the casing. Again, that's not an exact translation, but it can give you a sense of Total Newtons of the motor. So, for example, a motor filling the 38/720 casing has somewhere in the ballpark of 720 Total Newtons. Sometimes, it's far short of that, depending on the load (I600 is only 600 Newtons, but the J500 fits in the same casing and has 723 Total Newtons). So, if you're trying to compare CTI hardward to Aerotech hardware designations, and you're a CTI-minded flyer, you can translate Aerotech numbers to "grains." If you're an Aerotech person trying to grasp CTI's designations, think of each "grain" as an approixmate chunk of Newtons.
View attachment 300398
That chart is a great resource! There are a few minor changes that I would like to propose, though. The 98/15360 is fully interchangeable with the Pro98-6G, not the 5 grain. The 29/360 is 6 grains and has motors comparable to the Pro29-6G. Lastly, 38mm is probably the hardest diameter to compare. I regularly see people compare the 38/720 to the Pro38-6G, most likely because they both have 6 grains. The Aerotech grains are shorter, though, so the 38/720 is much closer to the Pro38-5G.
 

CzTeacherMan

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That chart is a great resource! There are a few minor changes that I would like to propose, though. The 98/15360 is fully interchangeable with the Pro98-6G, not the 5 grain. The 29/360 is 6 grains and has motors comparable to the Pro29-6G. Lastly, 38mm is probably the hardest diameter to compare. I regularly see people compare the 38/720 to the Pro38-6G, most likely because they both have 6 grains. The Aerotech grains are shorter, though, so the 38/720 is much closer to the Pro38-5G.
Yeah, as I was slapping it together, I thought of the same thing, especially regarding the 38s... I always think of the 720 as a kind of 5.5G... LoL. I'll make some adjustments tonight and see what y'all think.
 

ECayemberg

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Yeah, as I was slapping it together, I thought of the same thing, especially regarding the 38s... I always think of the 720 as a kind of 5.5G... LoL. I'll make some adjustments tonight and see what y'all think.
Cool chart!

AT 29/360 = 6G. AT 54/2560 = 6G, 2800 = 6XL. AT 75/7680 = 6XL. AT 98/15360 = 6G. Using comparative propellant lengths; grain geometry occasionally differs slightly (ie: 6 "long" grains as opposed to 7 "standard length" grains in longer motors)

-Eric-
 

Reinhard

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Yeah, as I was slapping it together, I thought of the same thing, especially regarding the 38s... I always think of the 720 as a kind of 5.5G... LoL. I'll make some adjustments tonight and see what y'all think.
The 54mm casings are another case where AT doesn't offer a 5G casing. The 54/2560 typically contains 6 grains. On ATs homepage, the grain configuration of every motor can be looked up.

Reinhard
 

CzTeacherMan

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Cool chart!

AT 29/360 = 6G. AT 54/2560 = 6G, 2800 = 6XL. AT 75/7680 = 6XL. AT 98/15360 = 6G. Using comparative propellant lengths; grain geometry occasionally differs slightly (ie: 6 "long" grains as opposed to 7 "standard length" grains in longer motors)

-Eric-
So what is the AT comparison for a 29/5G, 54/5G, 75/6G, 98/5G?
As a CTI guy... My ignorance is showing...
When I update the chart should I relate the 5&6G with the larger or leave one blank? It seems like it's more of a spectrum they doesn't align exactly...
 

Banzai88

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Represent it as a cross over bridging in between the two.
 

Wayco

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I have gone back and re-read soopirV's original post and his last paragraph really is the key to this problem.

I'll freely admit, CTI is not without it's nomenclature faults, and that is why I'm not here to pick on AT, just want to learn how to enjoy AT as much as I do CTI. I find peace (and maybe this is because of my thickness) that I can look at a CTI datasheet and say, "hmmm...38mm 3G, I can fly that!" I want to do the same with Aerotech...earnestly.
I want to know what motor I can fly with what rocket. I don't really care how many grains it has or how many newtons it produces. I also have a problem with math, so I let Thrustcurve.com do it for me. All my rockets (except clusters) are input there and I use it exclusively to pick motors that work. Once you pick a motor that works, just click on it and Thrustcurve will tell you what casing it fits in. No need to fuzz up your brain with data that is easy to find.
Elton John said it best, "I'm a Rocketman, some of the science I don't understand"
 

CzTeacherMan

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I have gone back and re-read soopirV's original post and his last paragraph really is the key to this problem.



I want to know what motor I can fly with what rocket. I don't really care how many grains it has or how many newtons it produces. I also have a problem with math, so I let Thrustcurve.com do it for me. All my rockets (except clusters) are input there and I use it exclusively to pick motors that work. Once you pick a motor that works, just click on it and Thrustcurve will tell you what casing it fits in. No need to fuzz up your brain with data that is easy to find.
Elton John said it best, "I'm a Rocketman, some of the science I don't understand"
True... If one is looking for more than simply "Is this safe to fly?", using the 5:1 ratio with Average Ns to rocket weight is good enough, as well. Thrustcurve is a great tool and all, but I'm a proponent of "mindsim" as much as possible. Of course, as my mind withers in my old age, I may turn to other sources of information.
If one is looking for "approximate altitude", total Newtons is much more helpful, especially when comparing motors to motors. CTI prints the total Newtons right on the label wheras AT must be inferred from the size case that the motor goes into...
 

CzTeacherMan

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EDIT: my computer fizzled and posted twice
 
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woferry

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[I started a response when the thread was new but never managed to hit post. The chart that showed up since is a nice way of trying to equate the two systems, but I figured it's still worth saying...]

ThrustCurve is your friend. Bookmark it if you haven't already. :) You can search any load by name, and it tells you total impulse, what case it goes into, etc. No need to memorize or anything, just keep the website handy or use his phone app. It can even tell you which motors are good for your rockets if you set up an account and add your rockets. And he's got some great improvements on that stuff coming down the pike. I also personally prefer CTI's naming that includes the total impulse (one less thing to look up, though it still doesn't tell you the case size without needing to look that up), but I enjoy flying both vendor's loads. And like CTI, you can buy a few cases and the RAS (spacer system) and basically be covered for anything (noting that AT has a few rather out-there loads, like those for the 38/1320, though I think CTI might also since I've heard of things like a 5.3 grain motor or something like that). There are two versions of the RAS for the 54mm cases, the newer one lets you fly all of the loads with just two cases (54/1280 and 54/2800, you can buy the pair of cases with the RAS from AT as a complete set) while the original version only got you up to the 54/2560 case and didn't cover the 2800 loads.

What I find more confusing with AT personally is that some loads require extra or different hardware (there was a recent thread about it). Like when the FSD is required vs. when it isn't (mostly based on case size), and endburners often have a different forward closure, some motors have different aft closure requirements for a big nozzle vs. a smaller one, etc. Not as easy as CTI's system where the forward closure comes with the motor and I think there's only one aft closure per diameter(?). Unfortunately ThrustCurve doesn't provide this detail I guess since it's an AeroTech-specific issue. There is a price guide on AT's website that is kept up-to-date (compared to their rather outdated catalog), and it calls out the FSD and forward closure requirements, though it didn't seem to say anything about the aft closures. As far as I can tell you have to download the instructions for a specific motor to be sure what aft closure it needs.
 

dhbarr

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Some of the CTI sizes have a conical tail closure option in addition to the regular style.
 

soopirV

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I've been wanting to make this chart for myself for some time... Thanks for giving me the excuse to do so!...
Basically, When thinking of CTI's "Grains", you can kind of think of it as a number of propellant grains in the case. It's not necessarily the actual propellant configuration within the propellant package (think of the 54-6XL K300, it's just one large grain), but that gives you a sense of Total Newtons. Add another grain of propellant, add another grain's worth of total thrust. When considering the numbers on the Aerotech hardware, it's basically a statement of the total Newtons that can fit in the casing. Again, that's not an exact translation, but it can give you a sense of Total Newtons of the motor. So, for example, a motor filling the 38/720 casing has somewhere in the ballpark of 720 Total Newtons. Sometimes, it's far short of that, depending on the load (I600 is only 600 Newtons, but the J500 fits in the same casing and has 723 Total Newtons). So, if you're trying to compare CTI hardward to Aerotech hardware designations, and you're a CTI-minded flyer, you can translate Aerotech numbers to "grains." If you're an Aerotech person trying to grasp CTI's designations, think of each "grain" as an approixmate chunk of Newtons.
View attachment 300398
THAT is getting printed up and stuck to my flight case, awesome! Thank you!!
 

soopirV

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[I started a response when the thread was new but never managed to hit post. The chart that showed up since is a nice way of trying to equate the two systems, but I figured it's still worth saying...]

ThrustCurve is your friend. Bookmark it if you haven't already. :) You can search any load by name, and it tells you total impulse, what case it goes into, etc. No need to memorize or anything, just keep the website handy or use his phone app. It can even tell you which motors are good for your rockets if you set up an account and add your rockets. And he's got some great improvements on that stuff coming down the pike. I also personally prefer CTI's naming that includes the total impulse (one less thing to look up, though it still doesn't tell you the case size without needing to look that up), but I enjoy flying both vendor's loads. And like CTI, you can buy a few cases and the RAS (spacer system) and basically be covered for anything (noting that AT has a few rather out-there loads, like those for the 38/1320, though I think CTI might also since I've heard of things like a 5.3 grain motor or something like that). There are two versions of the RAS for the 54mm cases, the newer one lets you fly all of the loads with just two cases (54/1280 and 54/2800, you can buy the pair of cases with the RAS from AT as a complete set) while the original version only got you up to the 54/2560 case and didn't cover the 2800 loads.

What I find more confusing with AT personally is that some loads require extra or different hardware (there was a recent thread about it). Like when the FSD is required vs. when it isn't (mostly based on case size), and endburners often have a different forward closure, some motors have different aft closure requirements for a big nozzle vs. a smaller one, etc. Not as easy as CTI's system where the forward closure comes with the motor and I think there's only one aft closure per diameter(?). Unfortunately ThrustCurve doesn't provide this detail I guess since it's an AeroTech-specific issue. There is a price guide on AT's website that is kept up-to-date (compared to their rather outdated catalog), and it calls out the FSD and forward closure requirements, though it didn't seem to say anything about the aft closures. As far as I can tell you have to download the instructions for a specific motor to be sure what aft closure it needs.
I was a part of that thread too, so deliberately didn't bring it up here, but it's a very valid point- are the systems poka-yoke in any way, or is it possible to need an FSD, but not include it, and still get the motor together?
 

watermelonman

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WHY IS IT SO HARD FOR ME TO UNDERSTAND AeroTech NAMING CONVENTIONS?
Because they are awful.

I have yet to find a single person who can name every forward closure and what each is for.
 

CzTeacherMan

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I was a part of that thread too, so deliberately didn't bring it up here, but it's a very valid point- are the systems poka-yoke in any way, or is it possible to need an FSD, but not include it, and still get the motor together?
Ditto these questions. I also remember hearing about the various aft closures at some point, as well, but have never wrapped my head around it. Different aft closures for different nozzles. However, I think this only affects a small number of reloads, and possibly on the way out as AT updates it's reload systems.
Forward closures seem fairly easy: Open (has an ejection charge well), closed/plugged (no charge well), extended forward closure (longer for a larger smoke grain).

... What I have no idea on... RMS, DMS, EZ... wtf? If someone helps me grasp that, I'd be very appreciative.
 

Banzai88

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Ditto these questions. I also remember hearing about the various aft closures at some point, as well, but have never wrapped my head around it. Different aft closures for different nozzles. However, I think this only affects a small number of reloads, and possibly on the way out as AT updates it's reload systems.
Forward closures seem fairly easy: Open (has an ejection charge well), closed/plugged (no charge well), extended forward closure (longer for a larger smoke grain).

... What I have no idea on... RMS, DMS, EZ... wtf? If someone helps me grasp that, I'd be very appreciative.
Don't forget the threaded forward closure!
 

noffie79

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Ditto these questions. I also remember hearing about the various aft closures at some point, as well, but have never wrapped my head around it. Different aft closures for different nozzles. However, I think this only affects a small number of reloads, and possibly on the way out as AT updates it's reload systems.
Forward closures seem fairly easy: Open (has an ejection charge well), closed/plugged (no charge well), extended forward closure (longer for a larger smoke grain).

... What I have no idea on... RMS, DMS, EZ... wtf? If someone helps me grasp that, I'd be very appreciative.
RMS is "reloadable motor system", meaning you need a case. DMS is "disposable motor system", basically single use, no case needed.
 

soopirV

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Don't forget the threaded forward closure!
Isn't there also a floating forward closure? This is what drives me nuts! I love the concept of building your own reload; I would much prefer it to the unpack and screw that CTI has us doing (that sounds fun, actually), but outside of the 29/40-120 realm, there are too many odd variables that can't be reasoned through without a ton of additional resources.
 

soopirV

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I'm going to try to put my biology training to good use and try come up with a phylogenetic tree showing the family...maybe seeing it graphically will help those of us who want to join but are wary...stay tuned! Maybe.
 
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