Accidentally Blurring the MPR/HPR Line

[thecapotc]

Based on the discussion over here ( https://www.rocketryforum.com/threads/do-you-consider-mpr-a-pre-requisite-for-hpr.160426/ ) I went back and did some checking on just how close did my 4H club come to the HPR line and did I accidentally lead them over it.

The club members didn't do any building without supervision, and all rockets were assembled with either JB weld or BSI 15 minute epoxy. I wasn't an experienced HPR builder, but I am a Mech. Engineer who's worked in manufacturing on equipment for 20 years, what I would consider handy (grew up in the country fixing all sorts of things, working on cars, etc.) and have used epoxy for all sorts of things.

Our goal was low and slow display launches with one launch per model (a 4H sponsor received the rocket for permanent display after the flights).

My question, and where I may have led the group into HPR accidentally, is on NAR Level 1 and the requirement for rocket weight.
Per NAR's website a Level 1 certification is required if a person wants to "3. Launch rockets that weight more than 53 ounces".
Does this mean empty or loaded for flight?

What was built and launched:

LOC IV on a G74
Based on what I can find online this would have weighed 35.1 oz plus paint and dog barf. I don't think we hit 53 oz.

LOC T-LOC 4" on a F26
Based on what I can find online this would have weighed 39.6 oz plus paint and dog barf. I don't think we hit 53 oz.

Apogee Zephyr on a G78
Based on what I can find online this would have weighed 48.4 oz plus paint and dog barf. I think we probably hit 53 oz with this one.

We were launching away from the spectators on a closed site, but I think we may have pushed through the rules a little if the weight limit is based on a fully flight ready rocket.

Either way if the club continues this fundraiser I'll be keeping a closer eye on the weight requirement moving forward.

 

[dhbarr]

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.

 

[astronwolf]

The Apogee Zephyr is sold as a high power rocket. For good reason.

 

[ljwilley]

Yes, just make sure you pay attention to weight next time.

 

[rcktnut]

Good for you for bringing up your concerns. It isn't to hard to blur the line between LPR/HPR when the safety codes/ regulations are blurry. It happens when you have 2 different agencies NFPA, FAA regulating the hobby. They don't make total sense but need to be followed if we wish to enjoy the hobby as is now. Under class one you can put a H motor in a 15 oz. minimum dia. metal tipped nose cone all fiberglass rocket and fly it to ump-teen altitude, but can't fly a MPR motor in a 54 oz. rocket to 800ft. Needing to cert level one for flying any MPR class motor is BS. They can't trust us I guess to look for aircraft before pushing the launch button.

 

[SecondRow]

Needing to cert level one for flying any MPR class motor is BS.

You don’t ever need to cert L1 for a motor that is not an HPR motor. If your rocket weighs more than 1500 grams fully loaded, but you’re using a low power motor, then you need a waiver - not an L1.

Nah. I’m wrong. Over 1500g requires HPR certification. My bad.

 

[thecapotc]

Luckily all the launches went as smoothly as possible and everything recovered perfectly, the longest walk we had was maybe 100 yards. The only damage was a plywood fin that landed on concrete and split the fin tip.

Being more knowledgeable has killed the next idea though, which was a 4" Phoenix, but alas the kit alone is over the weight limit. So I'll just have to research more before the club is presented with choices for the rocket.

Thanks @dhbarr for the clarification on the weight. I had a sneaking suspicion it included everything for flight but wasn't sure.

Now back to lurking and figuring out the next slightly ridiculous model rocket to help the club raise money. Maybe the club members all build an Alpha and the fundraiser is a 3" or 4" Alpha ...

 

[Back_at_it]

Luckily all the launches went as smoothly as possible and everything recovered perfectly, the longest walk we had was maybe 100 yards. The only damage was a plywood fin that landed on concrete and split the fin tip.

Being more knowledgeable has killed the next idea though, which was a 4" Phoenix, but alas the kit alone is over the weight limit. So I'll just have to research more before the club is presented with choices for the rocket.

Thanks @dhbarr for the clarification on the weight. I had a sneaking suspicion it included everything for flight but wasn't sure.

Now back to lurking and figuring out the next slightly ridiculous model rocket to help the club raise money. Maybe the club members all build an Alpha and the fundraiser is a 3" or 4" Alpha ...

You could do a bulk buy on the BMS 3in school rocket. Those makes for nice SIMPLY builds and you can stretch them if you like.

As for the weight limit of 54oz. I'd say you need to weigh your actual rocket. Mine squeaks by at 53.8oz if I use wadding and leave out the fire blanket and that is with the 29 to 38mm adapter and mine is built with an additional centering ring at the top of the motor tube. You might have been within regulations but it's always best to check.

 

[smstachwick]

You don’t ever need to cert L1 for a motor that is not an HPR motor. If your rocket weighs more than 1500 grams fully loaded, but you’re using a low power motor, then you need a waiver - not an L1.

Nah. I’m wrong. Over 1500g requires HPR certification. My bad.

…for good reason. At November 2021’s ROCStock event there was a pretty impressive rocket flown on a cluster of 52 Estes E12 motors (equivalent to a K581!) flown by a forum member I believe. Something that size malfunctioning can bite.

 

[cbrarick]

your rocket was 48.4 ounces, and the motor was 4.4 ounces total weight 52.8 ounces.
close but no cigar, Class 1.

it's a go-no go idea, so you were good as far as can be determined. Don't loose sleep over it. Consider it a learning experience on how close you can come.

i think the other posters are correct, weigh the rocket ready to fly, but you might want to be a little farther from the limit.

 

[rcktnut]

You don’t ever need to cert L1 for a motor that is not an HPR motor. If your rocket weighs more than 1500 grams fully loaded, but you’re using a low power motor, then you need a waiver - not an L1.

Nah. I’m wrong. Over 1500g requires HPR certification. My bad.

You could do a bulk buy on the BMS 3in school rocket. Those makes for nice SIMPLY builds and you can stretch them if you like.

As for the weight limit of 54oz. I'd say you need to weigh your actual rocket. Mine squeaks by at 53.8oz if I use wadding and leave out the fire blanket and that is with the 29 to 38mm adapter and mine is built with an additional centering ring at the top of the motor tube. You might have been within regulations but it's always best to check.

Back_at_it: The weight limit is 53oz., your over the limit by .8 oz. for a class 1 launch, or without being certified. Too bad for those wishing to stay at MPR or those working their way up. They should at the very least be allowed to fly a MPR class G motor in a rocket over 53 oz. at a field that has a waiver, without need of certification.

Guys, see how the Regs./ safety codes are a little blurry, and this isn't the only subject they are blurry on.

 

[Steve Shannon]

That’s not blurry at all. It’s a clear numerical limit.

 

[SecondRow]

…for good reason. At November 2021’s ROCStock event there was a pretty impressive rocket flown on a cluster of 52 Estes E12 motors (equivalent to a K581!) flown by a forum member I believe. Something that size malfunctioning can bite.

Yeah, but the total impulse for that cluster requires HPR certification regardless of total mass.

 

[SecondRow]

Here’s a chart that will help. I forgot to look at it before I posted about the mass limit.

It sets out when a cert and/or a waiver is required. If you’re in the green for every category, then no cert or waiver is required.

 

[smstachwick]

I bet @MetricRocketeer would have an aneurysm if he saw how messy the conversions are in this thread.

 

[thecapotc]

I bet @MetricRocketeer would have an aneurysm if he saw how messy the conversions are in this thread.

I’m a manufacturing engineer by trade so back of the dirty napkin conversions are kind of my thing for starting points and SWAGS.

I don’t get worried about exactness until it’s time to haggle over the acceptance terms and/or putting my name on the equipment or process as certified.

 

[Back_at_it]

Back_at_it: The weight limit is 53oz., your over the limit by .8 oz. for a class 1 launch, or without being certified.

Oops. I honestly thought the limit was 54oz. I don't think there is anyway I can knock more weight out of that rocket than I already have. Maybe it's time to build another one

 

[sriegel]

Luckily all the launches went as smoothly as possible and everything recovered perfectly, the longest walk we had was maybe 100 yards. The only damage was a plywood fin that landed on concrete and split the fin tip.

Being more knowledgeable has killed the next idea though, which was a 4" Phoenix, but alas the kit alone is over the weight limit. So I'll just have to research more before the club is presented with choices for the rocket.

Thanks @dhbarr for the clarification on the weight. I had a sneaking suspicion it included everything for flight but wasn't sure.

Now back to lurking and figuring out the next slightly ridiculous model rocket to help the club raise money. Maybe the club members all build an Alpha and the fundraiser is a 3" or 4" Alpha ...

You might talk to Frank Burke of DynaSoar. He's built a number of large MPR projects from Depron that would otherwise have required HPR.

 

[rcktnut]

Oops. I honestly thought the limit was 54oz. I don't think there is anyway I can knock more weight out of that rocket than I already have. Maybe it's time to build another one

Just tell everyone it weighs 52.99999 oz. and fly it!!

 

[SolarYellow]

Here’s a chart that will help. I forgot to look at it before I posted about the mass limit.

It sets out when a cert and/or a waiver is required. If you’re in the green for every category, then no cert or waiver is required.

Just last night, I finally dug through my hard drive to find that chart and saved it with a name I’ll actually be able to remember.

 

[Back_at_it]

Just tell everyone it weighs 52.99999 oz. and fly it!!

Honestly, I could probably put a smaller chute it in it and drop dome weight as it drifts forever on the stock chute anyways.

 

[rcktnut]

Guys, see how the Regs./ safety codes are a little blurry, and this isn't the only subject they are blurry on.

That’s not blurry at all. It’s a clear numerical limit.

Agreed I stuck with blurry to keep in line with OP's post. I'm talking about the overall discombobulation, confusion, whatever over the regs/ codes pertaining to OP's concern in this thread. Everything should be perfectly clear to most of us. But............................................
It is just my opinion that a G impulse should be a G period and be able to fly as a MPR and not be called a HPR motor also under certain circumstances. Sparky G's, G's with 80+Ns average thrust, and G's in a rocket that weighs over 53oz. are all considered HPR. = BS.

Back to OP's problem. Let's say the Zephyr weighs 48.0 oz. w/o motor. Using the G-78 (4.4 oz.) total weight comes to 52.4oz. Good to go under MPR/class1 codes. You need a minimum 1000 ft by 1000 ft launch field. Now lets put a nice reloadable G-64 (5.3 oz.) in that puppy. Now total weight is 53.7 oz. No go, can't launch that sucker without getting your L1 cert and enlarging your flying field to at least 1500 by 1500 ft. Just by adding a little weight you now have a HPR rocket. There are other MPR G's that also put this rocket over the limit. I don't care what anybody else thinks I call it BS.

Best solution though is don't break the rules, change them, or make sure your rocket is light enough to stay in a certain classification.

 

[cbrarick]

As for the weight limit of 54oz. I'd say you need to weigh your actual rocket. Mine squeaks by at 53.8oz if I use wadding and leave out the fire blanket and that is with the 29 to 38mm adapter and mine is built with an additional centering ring at the top of the motor tube. You might have been within regulations but it's always best to check.

sorry, it doesn't matter what your rocket weighs. It only matters what the OP's rocket weighs. It's obvious that you and OP build differently. That's all your weight proves. (and that he builds lighter then you) We do not care what any other rocket weighs other then the OP's. Your logic would also say that it doesn't matter what his body weigh is, just what your body weight is. Who knows, maybe you weigh 200 and he's a svelte 130, but by your logic he weighs 200 as well. See where your submarine has a screen door?

 

[thecapotc]

As a thought exercise I did some digging and determined that I believe the following would meet all the criteria to launch with no Certs or Waivers per the chart from @SecondRow

Modify an LOC IV to be a dual 29mm mount and assuming there's no extra weight needed for stability jam 2 G72 single use ATs in it.

As near as I can tell this is ok because:
1. Each single engine has an impulse below 160 N-s
2. The total engine impulse is below 320 N-s
3. Total engine propellant mass is = 125 g
4. Single engine average engine impulse is below 80 N-s
5. Total flight ready mass is <1500 g ( 823 g for kit, 256 g for engines, leaves 421 g for assembly if you fly it naked. Not sure this is possible but I imagine you could assemble this with that much epoxy.)

I realize there's probably not a club that would allow this to launch <edit> without a safety inspection and checking the rules </edit>, and most likely somebody modifying a $100 kit to be a cluster would know what they are doing but it seems this scenario would/could be more dangerous than the Zephyr that probably broke the 1500 g weight limit <edit> by a couple grams. </edit>

Obviously I understand regulations exist for a reason and they should be followed, but it does seem like there's some room for a motivated individual or group to clarify and simplify the regulations.

For my part I'll be making sure I keep the 4H club safely below HPR moving forward, but it still surprises me how easily you could march right up to and over the line without even realizing it.

 

[Titan II]

...but it does seem like there's some room for a motivated individual or group to clarify and simplify the regulations.

They are perfectly fine the way they are.

 

[rcktnut]

thecapotc said:
...but it does seem like there's some room for a motivated individual or group to clarify and simplify the regulations.

They are perfectly fine the way they are.

They could use a few amendments especially the one that you need to be certified to fly a MPR motor in a 53+ oz. rocket. Even if that rocket needs to be flying under HPR rules no need to have a HPR cert when using a MPR motor in it. What is now considered a G MPR motor is not going to be able to safely fly much more weight than that anyway. G motors above 80Ns average thrust could be sold to members of NAR, Tripoli only to keep them out of the hands of ordinary citizens eliminating the need to have a HPR cert. to purchase or use. A D20 in an Estes Wizard or G125 in a minimum Dia. 29mm rocket same thing, both can injure or kill you.
Mixing up the weight of a rocket with motor total impulse and motor average impulse, means sometimes they are MPR and other times they turn into HPR all what makes it confusing. Again, a G is a G 80.01-160 Ns and any motors with these total impulses should all be MPR period and not require certification in order to fly.
These changes are not going to make it any less safe. The rules are the way they are now because Simon said so. Lines do have to be drawn somewhere but under certain circumstances another line has to be drawn under the first one like this example:

My model rocket will not weigh more than 1,500 grams (53 ounces) at liftoff and will not contain more than 125 grams (4.4 ounces) of propellant or 320 N-sec (71.9 pound-seconds)
A model rocket weighing more than 53oz. has to be flown under HPR rules but does not require HPR certification when flown with a MPR G impulse motor.

See real easy to do!! The hard part is getting Simon to go along with it. Better yet be nice to have no weight restrictions (other than the motors limitations) with rockets flown on G impulse motors, keeping them in the MPR classification. Keep the Geeeeeeeeeeeee where it's supposed to beeeeeeeeee: MPR.

 

[dhbarr]

Different aspects of our hobby are governed by the CPSC, FAA, FCC, ATF, USPS, DOT, NHTSA, etc. etc. I don't try to make them all make sense, but am grateful to all the hobbyists who have fought for decades to keep room for me in the sky.

 

[thecapotc]

I would say the hobby could use some more marketing/amplification/spreading the good word of where the lines are. I would appreciate a line as simple as @rcktnut proposed because while the little flyer that comes with Estes kits lists the size, total propellant, and impulse limits, on the back side it also shows that 2 G motors max out at the impulse limit.

I wouldn't have even thought twice about any of this if I didn't stumble into the other thread, because until then in my mind I wouldn't have considered that a rocket that flies on the motors listed on the flyer with every LPR kit I've ever gotten would violate the rules listed with all those kits.

All the rockets I bought for the club said "Great for your L1!" and "Flies Low and Slow!" and listed G motors. I didn't consider that I was brushing that line.

Maybe that's naive on my part, but I've always been a middle of nowhere lone-wolf flyer. I've never joined a club, or even a forum until recently when @hcmbanjo ended his blog and I needed something to fill the blog shaped hole in my rocket reading. I really blundered into big rockets when I thought it would help raise money for the 4H club, and then the kits were pretty much the same as I was used to only bigger, and they took the motors listed on the flyer I'd seen in every kit.

Now I know, and will be sure to pass it on. Maybe some day I'll go ahead and get my L1, but right now even if I had time to build all the rockets I want the "big" rockets on my list are BT-80 models I fell in love with in the '96 Estes catalog.

 

[Steve Shannon]

I was a 4H member more than a little while ago. I really liked it.

It sounds like you and your 4H club are already a rocket club. You might want to consider simply getting a waiver. Then you’re covered as far as FAA goes.
L1 is also super easy for someone with your apparent level of experience (by intent). Show up at a Tripoli or NAR launch. Walk around a little to get a feel for it. Find someone in charge and ask if you can certify. Pop an H in one of the rockets you brought and fly it successfully. We’d love to have you!

If it helps, here’s a link to the Tripoli Unified Safety Code.
https://s3.amazonaws.com/ClubExpres....2.pdf&Signature=x3szmvqubFxSp2zrem5Ei6Tdgik=
The word “Unified” means that we tried to put the most relevant rules into a single document to make it easier for our members. If you’re a student (attend school and between 18 to 24) then you can join Tripoli for $20 (it’s actually still just $10 until September 1st when it goes to $20). One advantage of belonging to a club like Tripoli or NAR is insurance.

No matter what, welcome to the forum!

 

[jqavins]

Back to OP's problem. Let's say the Zephyr weighs 48.0 oz. w/o motor. Using the G-78 (4.4 oz.) total weight comes to 52.4oz.

Based on the original wording:

Apogee Zephyr on a G78
Based on what I can find online this would have weighed 48.4 oz plus paint and dog barf. I think we probably hit 53 oz with this one.

it seems like the 48.4 oz weight included the motor; is that right? With a limit of 52.9 oz, you'd have needed 4.5 oz of paint and dog barf to go over the line. I'd bet you squeaked under, but I sure wouldn't bet much.

Anyway, if you did go over, it was an honest mistake and water under the bridge. Don't sweat it.

Obviously I understand regulations exist for a reason and they should be followed, but it does seem like there's some room for a motivated individual or group to clarify and simplify the regulations.

I doubt that. There are HPR motors and there are HPR flights. Well, no, actually it's all about HPR flights, and one criterion for that is the use of motors with certain characteristics, which we call HPR motors for convenience. "HPR motors" are defined by four clear lines: total impulse, propellant mass, average thrust, and sparks. HPR flights are defined by greater impulse, thrust, and propellant mass limits that only come into play when clusters or staging are involved; the presence of an "HPR motor"; and lift-off weight. Assuming that there is a good reason for each of those requirements, I don't think there's any room to state the rules more simply than the clear and unambiguous way they are already stated. Any attempt to cover every edge case would make the rules more complicate, not less.

An attempt to eliminate the edge cases would have to make the rules too restrictive, since they would have to one limit or another value very low in order to assure that other unsafe stuff can't occur. You could, for example, reduce it to "An HPR is any rocket launching with total impulse higher than 120 Ns or any sparky motor." That would, by force, also eliminate single motor impulse, total propellant mass, and average thrust greater than what's currently allowed, since you really can't exceed any of those without going over 120 Ns. But it would also eliminate many cases that are and should be MPR today.

Even if that rocket needs to be flying under HPR rules no need to have a HPR cert when using a MPR motor in it.

What does that mean, it flies "under HPR rules" but you don't need a cert. "You need a cert" is the essence of HPR rules.

G motors above 80Ns average thrust could be sold to members of NAR, Tripoli...

NAR or Tripoli membership is proof of nothing except having paid NAR or Tripoli dues.

Mixing up the weight of a rocket with motor total impulse and motor average impulse, means sometimes they are MPR and other times they turn into HPR all what makes it confusing.

All it means is that in some edge cases, what's typically and conveniently called an "MPR motor" can power an HPR flight. Again, there are parties that ought to do a better job of communicating that, but I don't see why it's basically confusing.

It is just my opinion that a G impulse should be a G period and be able to fly as a MPR and not be called a HPR motor also under certain circumstances. Sparky G's, G's with 80+Ns average thrust, and G's in a rocket that weighs over 53oz. are all considered HPR. = BS.

It only looks like BS if you think it's all about the motor, and all about the letter. But it's really all about the flight. H motors and up are called "HPR motors" because if you use one it's certain that you're doing an HPR flight; not using one doesn't mean you're not doing an HPR flight.