Opinion on LPR vs MPR

[Kruegon]

I know where we officially draw the line between low power and mid power. What I'm curious about is where you, as individuals, draw the line.

Flatly stated, E, F, & G motors are mid power. A, B, C, & D motors are low power. Since I flew Estes exclusively for the first roughly 24 years of my flying, a BP 'E' just feels low power. Even the BP 29mm E & F feel kinda low power to me.

So strictly speaking from my gut feeling, BP motors are low power. Anything composite E thru G is mid power. Makes no sense right? It just how it feels to me when I fly them.

What about you?

 

[dhbarr]

A d21 is definitely mid, IMO. The feel for me is probably peak thrust vs. frontal surface area, not necessarily avg. or total.

 

[Gary Byrum]

I can't really draw a line, sotospeak. I've been building mid power rockets out of low powered parts for a few years now. And realizing that some of the LPR models I already have, perform quite well on MPR motors.

 

[Kruegon]

A d21 is definitely mid, IMO. The feel for me is probably peak thrust vs. frontal surface area, not necessarily avg. or total.

That's a good point. I haven't flown the 18mm composites yet so I don't have a point of reference. I'm hoping to resolve that issue shortly.

I need 2 18/20 cases in my stash. One for me, one for the wife. I've got to add another 24/40 and 24/60 to the stash for the same reason. Love that my wife is into rocketry with me. I hate when she bogarts my RMS cases.

 

[DavidMcCann]

Strictly speaking, MPR does not exist.

 

[EXPjawa]

They do exist...

I know that the sanctioning bodies don't officially recognize them Dave, but we all know that there are practical differences between the traditional low power stuff that we fly off of the A-pads and the mid-range stuff that has F or G motors, especially in terms of how close we want them to the LCO table when the button is pushed. That's why I've been setting up my tri-pad in between the A & B racks. So, from a practical viewpoint, we might as well acknowledge the middle ground that exists above the small rockets that Jackson flies and the stuff that's big enough to move out farther but not as large as L1-sized. And we should plan accordingly.

Regarding the original question, I'm kind of in the same boat as the OP. BP motors are, in general LP. Except, maybe, when you cluster three E16s together or something. But even smaller composite motors are on the fence, and probably should be considered Mid, depending on the size and potential of the rocket they're in...

 

[ThirstyBarbarian]

MPR is actually not defined by any law or rule, so it's perfectly fine to make your own definition. Until just a couple years ago, all my rocketry experience was with A through C motors, so I really felt like I had moved into a new class of rocketry when I flew my first E. And then shortly after that, I had that same feeling again when I flew my first composite E20. And then I had it again when I built my first rocket with heavier tubes, plywood parts, TTW construction, and a nylon chute. All of these steps were before flying an HPR motor which actually has a legal definition, so they were steps within the world of MPR. I guess now I sort of mentally draw the line at rockets that use some HPR building techniques that fly on F and G composites, maybe an E composite. I do mentally lump the E and F black powder motors in with the other smaller black powder motors in the world of LPR.

 

[neil_w]

When I fly a composite E in a Solar Warrior, it sure doesn't feel like mid power to me; that's the same rocket I flew a C in.

On the other hand, a larger rocket flying on an E might be more MPRish.

To me, it's easy to say an F is always mid power, but Es and even composite Ds are context dependent.

In other words: MPR is a state of mind. If it *feels* like mid power, then go with it.

 

[DavidMcCann]

They do exist...

I know that the sanctioning bodies don't officially recognize them Dave, but we all know that there are practical differences between the traditional low power stuff

strictly speaking . A-G have the same official min safe distance (https://www.tripoli.org/Portals/1/Documents/Safety Code/SLP - May 2016.pdf)

And strictly, low power doesn't exist either. Just mod-rocs and high power until you get larger.


For the unofficial breakdown, I'd lean more towards weight/build style than strict motor designations.

I'd break LP/MP around a pound, and MP/HP around 3.3 pounds. Of course taking the motors into consideration, bot not the sole basis.

 

[Tonimus]

I'd break LP/MP around a pound, and MP/HP around 3.3 pounds.

^This.

 

[fyrwrxz]

Everything I fly looks like LPR compared to Wayco (and Hardline)!

 

[DavidMcCann]

Rick- rereading my post I want to make sure it's not dismissive. I do like having mid pads out there, it gets the F/G in closer and I like that.

 

[SCrocketfan]

I kind of like the weight definition, but IMO:
A through G is LPR (assuming you also meet weight restrictions of <1500g)
H and above is HPR (a bit of which can still be class 1, with propellent <125G and mass <1500g)

Still, Thirsty's definition of "a rocket that uses some HPR techniques" is a great way of categorizing builds. Super Big Bertha/Maxi Alpha? Pretty much a big LPR. Wildman Mini? Not quite the same.

I do really like having separate pads for heavier low/mid power though (E-G, rails, 1/4" rods). It helps a lot at launches I've been to for reducing the wait for pads (being able to fly an F/G off a rail without having to go to the HPR pads 200' away) and makes for better MPR photography

 

[mkadams001]

I asked this question a few years ago.

https://www.rocketryforum.com/showthread.php?16306-What-Do-You-Consider-quot-Mid-Power-quot

 

[watermelonman]

Mid power is simply the overlap zone. Call it low power in regulation, but it is the part of the spectrum you are still likely to find in the arsenal of high power folks.

Alternatively, it is portion of low power where you still get to play with reloadable and composite motors, and techniques start to focus on strength instead of beauty and perfection.

I do wish we could do away with more of the arcane aspects of regulation. What we have is niche and nerdy enough without measuring fractions of a gram for super specific classifications.

 

[tab28682]

I have always liked the conventional definition of A-D as low power, E-G mid power and H and above as high power. Makes sense to me.

 

[tab28682]

strictly speaking . A-G have the same official min safe distance (https://www.tripoli.org/Portals/1/Documents/Safety Code/SLP - May 2016.pdf)

And strictly, low power doesn't exist either. Just mod-rocs and high power until you get larger.


For the unofficial breakdown, I'd lean more towards weight/build style than strict motor designations.

I'd break LP/MP around a pound, and MP/HP around 3.3 pounds. Of course taking the motors into consideration, bot not the sole basis.

Worth noting that the NAR has different safe launch distances for A-D (15 feet) and for E-G (30 feet).

 

[scsager]

Worth noting that the NAR has different safe launch distances for A-D (15 feet) and for E-G (30 feet).

^^^ This.

While the Model Rocket Safety Code does NOT specifically make any designation for "Low" power or "Mid" power, Rule #5 is very specific about the minimum safe distance.

5. Launch Safety. I will use a countdown before launch, and will ensure that everyone is paying attention and is a safe distance of at least 15 feet away when I launch rockets with D motors or smaller, and 30 feet when I launch larger rockets. If I am uncertain about the safety or stability of an untested rocket, I will check the stability before flight and will fly it only after warning spectators and clearing them away to a safe distance. When conducting a simultaneous launch of more than ten rockets I will observe a safe distance of 1.5 times the maximum expected altitude of any launched rocket.

If we are talking about power, (not rocket size) then it makes sense to draw the "imaginary" line between D / E following the NAR safe distance rule.


... The actual rules were changed a few years ago. Some newer folks might not know that there used to be an actual classification for "large" model rockets. That classification has been eliminated.

 

[KenECoyote]

^^^ This.

While the Model Rocket Safety Code does NOT specifically make any designation for "Low" power or "Mid" power, Rule #5 is very specific about the minimum safe distance.

5. Launch Safety. I will use a countdown before launch, and will ensure that everyone is paying attention and is a safe distance of at least 15 feet away when I launch rockets with D motors or smaller, and 30 feet when I launch larger rockets. If I am uncertain about the safety or stability of an untested rocket, I will check the stability before flight and will fly it only after warning spectators and clearing them away to a safe distance. When conducting a simultaneous launch of more than ten rockets I will observe a safe distance of 1.5 times the maximum expected altitude of any launched rocket.

If we are talking about power, (not rocket size) then it makes sense to draw the "imaginary" line between D / E following the NAR safe distance rule.


... The actual rules were changed a few years ago. Some newer folks might not know that there used to be an actual classification for "large" model rockets. That classification has been eliminated.

I was just about to reply that Estes instructs you to use the 30' Maxi Launch controller for most of the E engine rockets (some even give you the small launch set, but tell you that you need the larger one for E motors*). Seems Estes reco's 30' for most of their E&F motor birds, so to me that is their definition of Mid-Power.

*Here's the Maxi-Alpha set that includes the LP Electron Beam Controller and Port-pad II, but notes "*Requires Estes E Launch Controller, when launching E Engines - sold separately.":

Additionally, The Launch Pad company sells and advertises their rockets as being Mid-Power and they fly up to F motors.

So IMHO I'd say that generally Mid-Power (unless you have some crazy D motor or such) is E&F.

 

[Kruegon]

I was just about to reply that Estes instructs you to use the 30' Maxi Launch controller for most of the E engine rockets (some even give you the small launch set, but tell you that you need the larger one for E motors*). Seems Estes reco's 30' for most of their E&F motor birds, so to me that is their definition of Mid-Power.

*Here's the Maxi-Alpha set that includes the LP Electron Beam Controller and Port-pad II, but notes "*Requires Estes E Launch Controller, when launching E Engines - sold separately.":

Additionally, The Launch Pad company sells and advertises their rockets as being Mid-Power and they fly up to F motors.

So IMHO I'd say that generally Mid-Power (unless you have some crazy D motor or such) is E&F.

Just as a note, The Launch Pad has at least one G powered rocket and a couple of F clusters that equal a G.

 

[EXPjawa]

Rick- rereading my post I want to make sure it's not dismissive. I do like having mid pads out there, it gets the F/G in closer and I like that.

I didn't take it as such, Dave. But I always assume that your posts have a certain degree of tongue-in-cheek, for lack of a better description. I suppose others may not read it the same.

But we're in general agreement regarding pad placement here. I'm sure you know, I'm a big advocate for having dedicated mid-pads, especially to make use of the smaller rail sizes, that's pulled in closer for better viewing. Probably for the same reason as you - for better photography. Except in my case, the stupid small 18-55mm lens on my Cannon is the only lens I have, and a lot of my rockets are smaller. So its harder to see them in the frame if they're out with the high power pads. Most of the pics I upload are incredibly cropped just to see anything. But that's a different issue... I would've liked to have had the mini rail pads at URRF3 in closer than 100' for that reason. I was launching 18mm rockets on B6 motors out at 100', because that's were the micro rail got placed, so it was hard to see.

 

[DavidMcCann]

I didn't take it as such, Dave. But I always assume that your posts have a certain degree of tongue-in-cheek, for lack of a better description. I suppose others may not read it the same.

A safe assumption

I've had good luck with canon referb's- https://www.adorama.com/ca75300afr.html
Sigma's are also legit- https://www.adorama.com/sg70300daeos.html?RRref=productPage

(crap now I'm lens shopping >< )

 

[EXPjawa]

(crap now I'm lens shopping >< )

Sorry... Maybe I'll bug you about at the next launch. :grin:

 

[DavidMcCann]

Sorry... Maybe I'll bug you about at the next launch. :grin:

lol, no problem.I've actually been looking at the 24 and 40mm pancake primes. The idea of being able to toss my 7D in a pocket and hike/bike/etc is pretty appealing. I do it with the 50mm sometimes, and while it limits you to doing landscapes and other large view shots, it gets my camera places I certainly wouldn't lug any other lenses.

For rocketry, I'd use either a 55-250, a 75-300 (or 100-300 if you can find one used), or a 70-200 L f/4 (no IS)

 

[Kruegon]

Tangent…

 

[DavidMcCann]

Tangent&#8230;

resolved OP, so why not?

 

[samb]

Never really a question for me, E to G is midpower.

 

[Nick@JET]

This is a great discussion as I may have this argument on Wednesday with the 4H judge. I had my third and fifth grader build a mini AGM fiberglass through the wall fin for 4-H which can fly on an E. Although I cannot find an official ruling on what a third through fifth grader should build it should be as suggested a low-power. But since my kids of been building since they were five I'm getting kind of tired of balsa fin fin cardboard Rockets being destroyed after all that work. I rather like the thought of them being able to keep this rocket for years and years to come as long as I can find it

 

[DavidMcCann]

This is a great discussion as I may have this argument on Wednesday with the 4H judge. I had my third and fifth grader build a mini AGM fiberglass through the wall fin for 4-H which can fly on an E. Although I cannot find an official ruling on what a third through fifth grader should build it should be as suggested a low-power. But since my kids of been building since they were five I'm getting kind of tired of balsa fin fin cardboard Rockets being destroyed after all that work. I rather like the thought of them being able to keep this rocket for years and years to come as long as I can find it

From code of federal regulations- https://www.ecfr.gov/cgi-bin/text-idx?rgn=div5&node=14:2.0.1.3.15
§101.22 Definitions.

The following definitions apply to this subpart:
(a) Class 1&#8212;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.
(b) Class 2&#8212;High-Power Rocket means an amateur 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.
(c) Class 3&#8212;Advanced High-Power Rocket means an amateur rocket other than a model rocket or high-power rocket.
[Doc. No. FAA-2007-27390, 73 FR 73781, Dec. 4, 2008]



From NFPA 1122-

3.3.6* Model Rocket. A rocket that (1) weighs no more than 1500 g (53 oz)with motorsinstalled; and (2) is propelled by one or more model rocket motors having an installed totalimpulse of no more than 320 N*sec (71.9 lb*sec); and (3) contains no more than a total of125 g (4.4 oz) of propellant weight.



From a technical standpoint, the AGM is a mod-roc with the right motor. The only sticky point would be the construction material, but within rocketry FG is generally accepted as a 'breakable plastic"

 

[shreadvector]

N.F.P.A. 1122 2013 edition says:

4.14 Spectator Distances.
4.14.1 All persons shall remain at least 4.6 m (15 ft) from the
model rocket during ignition of a model rocket motor with an
installed total impulse of 30 N-sec (6.7 lb-sec) or less.
4.14.2 All persons shall remain at least 9 m (30 ft) from the
model rocket during ignition of a model rocket motor with an
installed total impulse of more than 30 N-sec (6.7 lb-sec).

So, 30 N-sec is effectively the dividing line within "Model Rocket" between low power and mid power Model Rockets.