High power test question.......

[Handeman]

Although NFPA 1122 & 1127 and FAR 101 may not have any rules involving the 62.5g propellant amounts, I believe DOT still does. So even it flying rockets doesn't actually involve anything with a 62.5g threshold, buying the motors and paying hazmat fees still involves that arbitrary number.

I'm also not sure how much that 62.5g number is embedded in international shipping/hazmat regulations that in turn tend to affect US DOT policies and rules.

That isn't really a rabbit hole I want to dive into. If a vendor tells me I have to pay hazmat on a motor order, I deal with that. They can figure out the whys and whatfors.

 

[OzHybrid]

Norm,
I don’t know if it was broadcast by Tripoli at the time, but NFPA has an entire process of publishing changes and soliciting comments so it’s very likely that it was discussed. It was four years before i joined the board and six years before I joined the NFPA technical committee. I can’t possibly go back and retroactively announce decade old changes and I don’t think you want me to.
To your point I think ATF still has a dead exception for rocket motors that includes 62.5 g of propellant as an upper limit. Of course since the lawsuit APCP is completely unregulated by ATF, but the exception is still there causing confusion. That might even be where Australian authorities got their pyrotechnics rule.

Hi Steve,
I agree the past cannot be practically fixed.
But this does not seem to be that far in the past.
After a bit of digging, the 62.5g limit was a definition in NFPA1122 as the upper limit for a single model rocket motor. If it is not classified as a model rocket motor, it becomes an HPR motor by default regardless of what the HPR definition may say. As @Handeman says, it was and seems to still be used as a DOT classification for transporting explosives(including non explosive propellant)
The definition is not there in the 2013 version of 1122 or later 2018 version, however, I can find it referenced in a 2015 Tripoli document. And referenced in a link to a Tripoli document as detailed above in 2021.
In 2008 version of NFPA 1122 it's there.

So I honestly do not think that it's as clean as it should be. And while it occurred in 2012/13, Tripoli does not seem to have purged its documentation of references to it, certainly in 2015 and possibly up to 2021 although I have no visibility of that referenced document as it has now been removed from the Tripoli site. I do have a copy of the 2015 document.

Norm

 

[Steve Shannon]

Hi Steve,
I agree the past cannot be practically fixed.
But this does not seem to be that far in the past.
After a bit of digging, the 62.5g limit was a definition in NFPA1122 as the upper limit for a single model rocket motor. If it is not classified as a model rocket motor, it becomes an HPR motor by default regardless of what the HPR definition may say. As @Handeman says, it was and seems to still be used as a DOT classification for transporting explosives(including non explosive propellant)
The definition is not there in the 2013 version of 1122 or later 2018 version, however, I can find it referenced in a 2015 Tripoli document. And referenced in a link to a Tripoli document as detailed above in 2021.
In 2008 version of NFPA 1122 it's there.
View attachment 585831
So I honestly do not think that it's as clean as it should be. And while it occurred in 2012/13, Tripoli does not seem to have purged its documentation of references to it, certainly in 2015 and possibly up to 2021 although I have no visibility of that referenced document as it has now been removed from the Tripoli site. I do have a copy of the 2015 document.

Norm

Then it seems like we purged it.

 

[OzHybrid]

Then it seems like we purged it.

Time to get the lawnmower out then. Moving on....

 

[Steve Shannon]

There seems to be a mention of the limit being in the Range Safety guidelines as late as 2021. The link to them no longer works. https://www.rocketryforum.com/threads/hybrids-2021.165685/post-2130407

One of the reasons we adopted the Tripoli Unified Safety Code was because we had multiple different documents with sometimes contradictory and confusing rules. The TUSC replaces all of those for Tripoli. If you find something that is contradictory, please let us know.

 

[OzHybrid]

One of the reasons we adopted the Tripoli Unified Safety Code was because we had multiple different documents with sometimes contradictory and confusing rules. The TUSC replaces all of those for Tripoli. If you find something that is contradictory, please let us know.

The problem is that with no changelog, or historical references, it's difficult to check without completely going through every bit of legislation every time and comparing it against the unified safety code. Can we have a public changelog?

 

[John Taylor]

Please forgive me if this seems like a stupid question....... But A High Power rocket motor starts at total impulse of 160.01 - 320.00 Newtons (an H motor)
and doubles with each subsequent class of motor. For example.... 360.01- 640.00 Newtons (an I Motor) .........All the way to 20,480.01 - 40,960.00 Newtons (an O motor)
A Model Rocket Motor must have a total propellant weight less than 125 Grams to be classified as NOT High Power.

I know there are members on here WAY smarter at Rocket Science than I, so I am not afraid to ask and further my knowledge !!


An F90 motor with 40 Grams of propellant does NOT seem to meet the classification of High Power Rocket Motor, & yes, I know the F Class is 40.01 - 80.00 Newtons
but it does state "hypothetically"

Given JUST the info, below why is the only correct answer "C" ? Seems to me it should be "A" & "C"

​

Question A17 Which of the following (hypothetical) rocket motors is NOT a High Power Rocket motor? A. An F90 with 40 grams of propellant B. An H60 with 62 grams of propellant C. A G35 with 66 grams of propellant D. All of the above are High Power Rocket motors

Any motor with an average thrust of 80ns is high power.

 

[OzHybrid]

Any motor with an average thrust of 80ns is high power.

It's an old question that's been rewritten....
F90 has average thrust >80N so HP
H60 has been designated as H so is HP
G35 66g of prop is under 80N and lower than 125g so is the only one that is NOT HP

The answer is C

However, it's important to keep up with the moving goalposts. The old answer was D. There was previously an NFPA1122(manufacture of rocket motors) limit of 62.5g for a single motor that is within low power category. This was changed to 125g as the limit some time ago.` (But still exists in the DOT rules for the transportation of"explosives") So is not applicable for personal transportation or launching of.

See historical references here.

https://www.rocketryforum.com/threads/high-power-test-question.180388/post-2445664

 

[Glasspack]

It's an old question that's been rewritten....
F90 has average thrust >80N so HP
H60 has been designated as H so is HP
G35 66g of prop is under 80N and lower than 125g so is the only one that is NOT HP

The answer is C

However, it's important to keep up with the moving goalposts. The old answer was D. There was previously an NFPA1122(manufacture of rocket motors) limit of 62.5g for a single motor that is within low power category. This was changed to 125g as the limit some time ago.` (But still exists in the DOT rules for the transportation of"explosives") So is not applicable for personal transportation or launching of.

See historical references here.

https://www.rocketryforum.com/threads/high-power-test-question.180388/post-2445664

Thank You !

 

[Art Upton]

I was NOT aware of the Average Thrust Limit with the Rule .............. And I can't find it in the LPR or HPR Safety Code posted on NAR Web site.
But I will keep looking
Thank You !!

It was because of Consumer Protection. Same reason you need to be 18 to buy a G motor.

 

[Glasspack]

It was because of Consumer Protection. Same reason you need to be 18 to buy a G motor.

Thank You Art

 

[OzHybrid]

Thank You Art

To understand the rules, you need to read all of the legal documentation. The NFPA documentation forms the basis of the Tripoli and NAR rules.
The 80N limit is in NFPA 1125, Motor Manufacturing rules.
Specifically section 7.7.4

You need to read ALL the rules and understand them.
NFPA 1122 Code for Model Rocketry
NFPA 1125 Code for the Manufacture of Model Rocket and High-Power Rocket Motors( which includes the specific definitions for motors)
NFPA1127 Code for High Power Rocketry
You also need to know the Tripoli and/or NAR rules, guidelines, and any local rules for AHJ(authorities having jurisdiction) such as but not limited to Fire, Police, Councils owning the land you are launching from. The FAA or CASA if you're in Australia.... Or both if you have to be compliant with Tripoli rules based on FAA and local CASA rules.

In the rules there are 3 things.

Things that are prohibited.
Things that are required.
Things that are not mentioned and are therefore not prohibited. ( but may still not be allowed or may be allowed........they're not not allowed.......)

This is why it's easier to join a club that will have gone through this legal minefield for you.