Typical BP Engine Thrust Curve

jqavins

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I had decided to cease pedantry for this thread, and then...
Those impulse ratings are defined by the letter designation system for each letter grade of motors G motors are only in the range of 80.01 to 160.00 total Ns, irrelevant of the amount of giddy-up (thrust) they produce.
Damn my OC tendencies!

The impulse isn't defined by the letter system. The letter system is defined by the impulse, and the impulse is indicated by the letter system.
 
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mh9162013

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Sure, right. No worries.

My point (other than the one on my head) is why the use of the word "Power"? Why not LIR - MIR - HIR? I guess because, arguably, the word "Power" rolls off the tongue and sounds better.

View attachment 532040 View attachment 532041
I think power in this context is being used loosely. Just like the terms "low," "mid" and "high."

So if we're going to use an imprecise word for part of the term, there's no harm in adding another "imprecise" word.

It's like sigfigs: there's no point in using higher levels of precision for a calculation for one value when the other values have lower levels of precsion.
 

BEC

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Hmmm, that's a good question.

Generally speaking, HPR > MPR > LPR in terms of both thrust and total impulse, right? Sure, there might be an "MPR" motor that has more thrust than a "HPR" motor (even if it's just for a split second). But in that case, the MPR motor would certainly have lower total impulse than the HPR motor.
Of course there are examples of this. For instance, I like to fly CTI G83 Blue Streaks and G88 Smoky Sams in some of my models. Since the average thrust is over 80 Newtons, technically I have to have a level 1 high power (there’s that word again!) certification to buy them and fly them…..
 

rharshberger

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Of course there are examples of this. For instance, I like to fly CTI G83 Blue Streaks and G88 Smoky Sams in some of my models. Since the average thrust is over 80 Newtons, technically I have to have a level 1 high power (there’s that word again!) certification to buy them and fly them…..
Now we are getting out of generalities and back into specifics. LPR, MPR and HPR are generalities, whether a specific G motor is MPR or HPR is specifically called out in regulations based on its total propellant weight and thrust, not its total Ns which are still between 80.01 and 160 Ns. There F motors that fall under L1 cert requirements too but they are still F's, my favorite example is the CTI F240 Vmax.
 

smstachwick

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Regarding the MPR designation, I believe this was once significant in the regulatory sense, but no longer. Specifically, my brief dig indicates that MPR was Class 2 under FAA rules, Class 3 was equivalent to today’s Class 2 High-Power rockets, and Class 4 was equivalent to today’s Class 3 rockets.

Personally I think categorizing rockets by Class makes more sense than by “power” or “level”. But alas, the regulatory powers that be don’t coordinate.
 

Alan15578

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Regarding the MPR designation, I believe this was once significant in the regulatory sense, but no longer. Specifically, my brief dig indicates that MPR was Class 2 under FAA rules, Class 3 was equivalent to today’s Class 2 High-Power rockets, and Class 4 was equivalent to today’s Class 3 rockets.

Personally I think categorizing rockets by Class makes more sense than by “power” or “level”. But alas, the regulatory powers that be don’t coordinate.
You might be on to something. Please elaborate.

Meanwhile, as far as TRF is concerned. Why does TRF separate MR into three areas: Micro, Low, and Mid? These are all the same administratively, unless you want to make the case for LMR: G motors or heavy model rockets over 16 Oz./500 g. On the other hand HPR has three real distinct levels and TRF lumps them all together in one area. Furthermore, the amount of traffic in the HPR area exceeds the combined amount in the three MR areas.
 

jqavins

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The categories here, as I see and understand it, are by interest and the broad strokes of construction methods, rather than by any regulatory distinction. "How do I build my MMX rocket super light?", "What do folks use for a good finish on a balsa nose cone?" and "Do I need to use plywood fins for F engines?" are all questions that pertain to the same regulatory class but very different building and flying types. "I'm looking for a better tool for epoxy fillets" could apply to any level of High Oomph Rocketry (HOR).
 

smstachwick

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You might be on to something. Please elaborate.
I don’t think I truly am, I think that statement speaks for itself, but I will try.

Basically, I think it gives a wider overview of the extent of hobby rocketry. Almost everybody starts at Class 1, many go to Class 2, a few go to Class 3. The regulatory burden in the three is distinct. Formally dividing Class 2 into levels makes sense as well, since a 2.6-inch Goblin upscale going on an H motor is going to be categorically different from an 8-inch one going on an N.

But inevitably you’re going to get more descriptive names for these classifications of rockets, especially since regulatory environments will be radically different in different places, and the hobby needs terminology that can cross borders.
 

rharshberger

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I don’t think I truly am, I think that statement speaks for itself, but I will try.

Basically, I think it gives a wider overview of the extent of hobby rocketry. Almost everybody starts at Class 1, many go to Class 2, a few go to Class 3. The regulatory burden in the three is distinct. Formally dividing Class 2 into levels makes sense as well, since a 2.6-inch Goblin upscale going on an H motor is going to be categorically different from an 8-inch one going on an N.

But inevitably you’re going to get more descriptive names for these classifications of rockets, especially since regulatory environments will be radically different in different places, and the hobby needs terminology that can cross borders.
Now we might be mixing Classes with Cert levels, there are Class 1,2, and 3 rockets (FAR 101 defines them).

Class 1 Model Rocket, no more than 125 grams of propellant and weighs no more than 1500 grams.

Class 2 High Power Rocket an amateur rocket other than a model rocket powered by a motor or motors of less than 40,960 Ns or less (O motor)

Class 3 Advanced High Power Rocket, an amateur rocket other than a model rocket or high power rocket. Motors bigger than O motors are in this category.

The joys of regulation and we have 3 different regs to deal with NFPA 1122 and 1127 (manufacturers can add 1125), and FAR 101.
 

smstachwick

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Now we might be mixing Classes with Cert levels, there are Class 1,2, and 3 rockets (FAR 101 defines them).

Class 1 Model Rocket, no more than 125 grams of propellant and weighs no more than 1500 grams.

Class 2 High Power Rocket an amateur rocket other than a model rocket powered by a motor or motors of less than 40,960 Ns or less (O motor)

Class 3 Advanced High Power Rocket, an amateur rocket other than a model rocket or high power rocket. Motors bigger than O motors are in this category.

The joys of regulation and we have 3 different regs to deal with NFPA 1122 and 1127 (manufacturers can add 1125), and FAR 101.
I’ve seen the regulations horse beaten to death, resurrected, beaten to death again, and then fed into a wood chipper in my year’s worth of activity here.

Here is the relevant reg set:

c. Amateur rocket classes:
  1. Class 1 - a model rocket that uses no more than 125 grams (4.4 ounces) of propellant; uses a slow-burning propellant; is made of paper, wood, or breakable plastic; contains no substantial metal parts; and weighs no more than 1,500 grams (53 ounces) including the propellant.
  2. Class 2 - a high power rocket, other than a model rocket, that is propelled by a motor or motors having a combined total impulse of 40,960 Newton-seconds (9,208 pound-seconds) or less.
  3. Class 3 - an advanced high power rocket, other than a model rocket or high-power rocket.

I believe NFPA regs are the ones that add additional criteria based on total impulse, define “slow-burning propellant”, place sparkles and hybrids firmly in the HPR realm, outline the motor certification process, etc. They require payment to access in full, as I understand, but they form the basis for the NAR and Tripoli Safety Codes.

Here is a summary of the intersecting regs and what that means for certification and waivers:

 

Steve Shannon

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I’ve seen the regulations horse beaten to death, resurrected, beaten to death again, and then fed into a wood chipper in my year’s worth of activity here.

Here is the relevant reg set:

c. Amateur rocket classes:
  1. Class 1 - a model rocket that uses no more than 125 grams (4.4 ounces) of propellant; uses a slow-burning propellant; is made of paper, wood, or breakable plastic; contains no substantial metal parts; and weighs no more than 1,500 grams (53 ounces) including the propellant.
  2. Class 2 - a high power rocket, other than a model rocket, that is propelled by a motor or motors having a combined total impulse of 40,960 Newton-seconds (9,208 pound-seconds) or less.
  3. Class 3 - an advanced high power rocket, other than a model rocket or high-power rocket.

I believe NFPA regs are the ones that add additional criteria based on total impulse, define “slow-burning propellant”, place sparkles and hybrids firmly in the HPR realm, outline the motor certification process, etc. They require payment to access in full, as I understand, but they form the basis for the NAR and Tripoli Safety Codes.

Here is a summary of the intersecting regs and what that means for certification and waivers:

The full versions of NFPA 1122, 1125, and 1127 are freely available on the NFPA.org website. You are required to register to access them and you cannot download, copy, or print them, unless you wish to pay a fee.
However, since May, Tripoli Unified Safety Code (TUSC) no longer requires a person to refer NFPA 1122 or 1127 as the foundation for the Safety Code. The TUSC also attempts to explain the difference between what is legally considered high power Rocketry (by those entities that have adopted NFPA 1122/1127) and the classes listed for FAA FAR 101.25.
 

smstachwick

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The full versions of NFPA 1122, 1125, and 1127 are freely available on the NFPA.org website. You are required to register to access them and you cannot download, copy, or print them, unless you wish to pay a fee.
However, since May, Tripoli Unified Safety Code (TUSC) no longer requires a person to refer NFPA 1122 or 1127 as the foundation for the Safety Code. The TUSC also attempts to explain the difference between what is legally considered high power Rocketry (by those entities that have adopted NFPA 1122/1127) and the classes listed for FAA FAR 101.25.
…and it’s once again proven that I shouldn’t be the one to explain the rules. Thanks Steve!
 

shockie

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The full versions of NFPA 1122, 1125, and 1127 are freely available on the NFPA.org website. You are required to register to access them and you cannot download, copy, or print them, unless you wish to pay a fee.
However, since May, Tripoli Unified Safety Code (TUSC) no longer requires a person to refer NFPA 1122 or 1127 as the foundation for the Safety Code. The TUSC also attempts to explain the difference between what is legally considered high power Rocketry (by those entities that have adopted NFPA 1122/1127) and the classes listed for FAA FAR 101.25.
You can screen capture
 

smstachwick

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You can screen capture
Some sites have implemented features to block screenshots. Disney+ for example is infamous for this.

Not sure if the NFPA has, but it wouldn’t surprise me if the right to share their regulations is a revenue source.
 

lakeroadster

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Some sites have implemented features to block screenshots. Disney+ for example is infamous for this.

Not sure if the NFPA has, but it wouldn’t surprise me if the right to share their regulations is a revenue source.

Off the record.... you can always do a PrtSc and copy it to Paint, unless it shows that it is copyrighted.
 

smstachwick

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Off the record.... you can always do a PrtSc and copy it to Paint, unless it shows that it is copyrighted.
D+ blocks this. Instead of your movie or show, it’s all blacked out.

I couldn’t even guess if NFPA has implemented something similar, but Tripoli’s consolidation of the relevant rules sort of makes it irrelevant.
 

lakeroadster

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D+ blocks this. Instead of your movie or show, it’s all blacked out.

I couldn’t even guess if NFPA has implemented something similar, but Tripoli’s consolidation of the relevant rules sort of makes it irrelevant.
Hmm? Must be something I've never encountered?

I've run into items that would print all black, and items that wouldn't let me save them, or if I did they were all black, but I've never encountered anything I couldn't print screen?

If you can't view it on the screen of your phone, laptop, PC... how do you even know it's the document you want?
 

GregGleason

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Here is a collection of thrust curves I made a while back. It shows the varied amount of differences between motors.

Greg
 

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