Accidentally Blurring the MPR/HPR Line

[rcktnut]

Why are we posting SO MUCH about what WERE the rules? All these history dissertations, scanned flyers, PDF files, descriptions, etc. etc. etc. are just going to muddy the water even more for someone CURRENTLY getting into (or back into) the hobby.

If any of the above get referenced out of the context if this history lesson, they are NOT CURRENT, or VALID, REFERENCES. But that caveat can easily be lost.

It would be great if we could just leave it at a summary of what the CURRENT limits ARE, and leave it at that. This way someone who is getting ready to fly a rocket NOW, would have a clear YES/NO to work from. [ They don't need to know that 15 years ago the rules were different.] The color coded table (that shows up in all these types of threads), is a great reference.

This thread was about weight being a factor in determining what is a class 1 flight or class 2 flight. Looks like weight was a factor since the beginning of model rocketry as we know it. With the classes being the way they are now and comparing them to the past, we are in a much better situation than years ago before the latest revision. That being said it is not perfect, pretty far from perfect, but to be expected when you have the alphabet agencies regulating the hobby.

Don't worry too much about this thread "mudding the water" with newcomers etc. Soon it will be by the wayside along with the Is my cluster a HPR rocket or not and Can I fly my class 1 rocket above the waiver at a class 2 launch.

 

[John Taylor]

1500g / ~53oz comes from 14 CFR 101.22, AKA FAR101.

(a) Class 1—Model Rocket means an amateur rocket that:
(1) Uses no more than 125 grams (4.4 ounces) of propellant;
(2) Uses a slow-burning propellant;
(3) Is made of paper, wood, or breakable plastic;
(4) Contains no substantial metal parts; and
(5) Weighs no more than 1,500 grams (53 ounces), including the propellant.

So the Zephyr may or may not have been a Model Rocket, but I would recommend weighing in grams going forward and keeping the final, fully-loaded weight at 1,499 or less.

And has an average thrust of 80ns or less.

 

[Steve Shannon]

And has an average thrust of 80ns or less.

That’s where it can be confusing. FAA regulations requiring a COA don’t care about the average thrust.
NFPA and our Safety Codes do though.

 

[samb]

I'd like to suggest an alternative to venting here about "Simon" and the alphabet agencies. The NFPA has a period of public comment built into their revision cycles. As I've mentioned before, the Pyrotechnics Committee includes several well-known members of our hobby community. All it will cost you to make your voice heard is the time it takes to create a free login/password on www.nfpa.org. "Ask not what your..."

 

[-Slick-Ice]

I am in favor of removing or increasing the 1500g weight requirement.

I would agree the 1500g weight limit is really close to the practical limit of being "safe" for a G80 but keep in mind that the AeroTech G80-7T is a monster and produces over 100N of thrust for 1 second. There are a lot of LOC-IV, Zephyr, IRIS-3 and similar rockets that can be flown safely at or above this weight on this motor and stay under 1000ft.

Whether inside of a plane or on the ground, I wouldn't want to get hit by anything above or under 1500g so I am not sure why they included this for "safety" perspective.

The field I fly at has a 10000ft waiver for every club launch but not everyone has this luxury.

I think you picked great rockets for your club to fly but lesson learned, keep an eye on the weight.

 

[Alan15578]

The 80N average trust limit was entirely a creation of an NAR person who thought that higher thrust would entice model rocketeers into making and flying terrorist weapons. He got that limit codified into the NFPA codes. Originally, the NFPA codes just specified that model rocket motors not function by explosion, and had a minimum burn time of 0.05 seconds. I'd be happy raising that limit to 1000N or so.

I think the FAI raised the mass limit to 1500 grams first, so there was incentive to normalize our codes and keep up with the times. I think the FAA just looked at 3 pound bird strike data and was OK with the 1500 gram limit. However, consider a 1500 gram fiberglass model with a heavy metal motor case on on end of a 100 Ft 1,000 lb. Kevlar line and a parachute on the other end. There is higher probability of an aircraft snagging the line, winding the cord arund the propeller, jamming the bearings, or whipping the model mass around and banging into the cockpit. If you ask the FAA for a higher mass limit, they may do a more in depth analysis and conclude that 1500 grams is too high. I personally have not had the need to fly a model rocker over 500 grams, and I think trying to push it over 1500 grams may be counter productive.

 

[kjhambrick]

<<<snip>>>If you ask the FAA for a higher mass limit, they may do a more in depth analysis and conclude that 1500 grams is too high ... <<<snip>>> I think trying to push it over 1500 grams may be counter productive.

+1

 

[-Slick-Ice]

Don't want to derail this but we have birds here that weigh more than a bowling ball. I wonder what made them draw the line at 3lbs for a bird. I kind of wish they would put their justification in the rules they write.

 

[kjhambrick]

Don't want to derail this but we have birds here that weigh more than a bowling ball. I wonder what made them draw the line at 3lbs for a bird. I kind of wish they would put their justification in the rules they write.

"We don't need no steenkin' reason ... we got badges !"

With apologies to: Treasure of the Sierra Madre: No Stinking Badges

 

[Handeman]

I am in favor of removing or increasing the 1500g weight requirement.

I would agree the 1500g weight limit is really close to the practical limit of being "safe" for a G80 but keep in mind that the AeroTech G80-7T is a monster and produces over 100N of thrust for 1 second. There are a lot of LOC-IV, Zephyr, IRIS-3 and similar rockets that can be flown safely at or above this weight on this motor and stay under 1000ft.

The weight limit comes from the FAA 101 regs. It has little to do with the rocket flying safely, it's about aircraft safety and damage to manned aircraft if the rocket strikes the aircraft. It originated with the definition the FAA had for Large Model Rockets. That Large Model definition was combined with Model rockets and combined into Class 1 rockets when they changed the classifications to Class 1, 2, and 3 for rockets and dropped the requirement to notify the FAA when flying Large Model Rockets.

I don't see that weight limit ever changing, especially if the reasons for changing it is based on rocket flight safety. I believe it will only change if you can convince the FAA a change won't affect manned aircraft safety.

 

[BABAR]

. Something that size malfunctioning can bite.

good point. Likely as long as flight is nominal you can get away with “nobody knows so can’t hurt me”, but if there really is fecal-turbine interaction the costs could be astronomical, and not in a good way.

and by definition your NAR insurance will likely not be valid.