Distance to launcher for mid-power

[RimfireJim]

I'm not sure if this is the right forum for this question, as it is about interpretation of the safety codes, but it applies to mid-power motor impulse range, so here goes:

The NAR Model Rocketry Saftey Code states, "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."

The NAE High Power Rocket Saftey Code states, "I will use a 5-second countdown before launch, and will ensure that everyone in the launch site is paying attention and that no person is closer to the launch pad than allowed by the accompanying Minimum Distance Table." The table shows a minimum personnel distance of 100 ft. for impulse range of 0-320 N-s, H or smaller.

So one code says I need 30 ft. for an E, F or G, and the other one says I need 100 ft. ??? Since G and under doesn't fall under High Power if the propellant mass is 62.5g or less, one can argue, reasonbly I believe, that the High Power code doesn't apply, in which case why does it bother to reference impulses lower than 'H'? (For the >62.5g G motors, maybe?) On the other hand, is 30 ft. really enough for G motors like the G64W?

I made the leads on my relay launcher something like 50 ft., so I'm pretty sure they are long enough for the E and F RMS motors I'm getting into, but I'm just a bit puzzled by the apparent discrepancy between the two codes.
-Jim

 

[cjl]

I would say that the HPR code does not apply in this case. 30 feet is a little close for a G though...

 

[dwmzmm]

Actually, the further back from the launch pad, the better view of
the rocket's liftoff (plus, the chances of getting good pics are increased). Especially if you're still using the "old" 35 mm film
cameras like me...

 

[RimfireJim]

Originally posted by dwmzmm
Actually, the further back from the launch pad, the better view of
the rocket's liftoff (plus, the chances of getting good pics are increased). Especially if you're still using the "old" 35 mm film
cameras like me...

I agree, which is one reason I built my launch system with a long cord even though I was doing only LP BP motors at the time. Still, curious about what seems like a disparity between the two codes.

 

[shreadvector]

Motors can be High Power motors even if they are not an H.
All they have to do is exceed any of the legal limits for a Model Rocket Motor.

https://home.flash.net/~samily/stuff/HPR_metric8.pdf

Originally posted by RimfireJim
I'm not sure if this is the right forum for this question, as it is about interpretation of the safety codes, but it applies to mid-power motor impulse range, so here goes:

The NAR Model Rocketry Saftey Code states, "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."

The NAE High Power Rocket Saftey Code states, "I will use a 5-second countdown before launch, and will ensure that everyone in the launch site is paying attention and that no person is closer to the launch pad than allowed by the accompanying Minimum Distance Table." The table shows a minimum personnel distance of 100 ft. for impulse range of 0-320 N-s, H or smaller.

So one code says I need 30 ft. for an E, F or G, and the other one says I need 100 ft. ??? Since G and under doesn't fall under High Power if the propellant mass is 62.5g or less, one can argue, reasonbly I believe, that the High Power code doesn't apply, in which case why does it bother to reference impulses lower than 'H'? (For the >62.5g G motors, maybe?) On the other hand, is 30 ft. really enough for G motors like the G64W?

I made the leads on my relay launcher something like 50 ft., so I'm pretty sure they are long enough for the E and F RMS motors I'm getting into, but I'm just a bit puzzled by the apparent discrepancy between the two codes.
-Jim

 

[jflis]

A couple of things.

1) First, how *I* would interpret it: For *all* "Model Rockets" (model rockets by definition) that are above a D motor the distance is 30 feet. For *all* "high power in the lower range (by definition) the distance is 100 feet. There is no part of the HPR code that applies to "model rocketry". Likewise, there is no part of the model rocket safety code that applies to HPR.

2) "Mid-Power" is an interesting term that many/most people have adopted for that category of rocket where you start to get into some different building and launching techniques because of the higher power of the motor. While it is a *recognized* term, I do not beleive it is an "official" term in any capacity. I know of no "mid-power safety code" nor of any rule that uses that term. It's just a differentiator that we (the rocketry community) have adopted. In fact, my joining TRF was the first I had ever heard the term...

fwiw
jim

 

[gstarraider]

Not to mention, if you are using a E,F, and G motor like a aerotech blackjack propellant motor, and your only standing 15 feet away, i would want to see my rocket launch, not stand in the middle of a black cloud and see nothing. My own personal preferance is anywhere between 30 and 50 feet for my mid power pads, putting the the distance about half way between the low power and the high power pads.

 

[RimfireJim]

Originally posted by shreadvector
Motors can be High Power motors even if they are not an H.
All they have to do is exceed any of the legal limits for a Model Rocket Motor.

https://home.flash.net/~samily/stuff/HPR_metric8.pdf

Yes, I'm well aware of that (I have your referenced chart saved on my computer and referred to it when I wrote the first message in this thread), which is why I included the phrase "if the propellant mass is 62.5g or less". I guess I should have also included "single motor average thrust 80N or less". I was hoping that, without getting into all the details of whether a motor is a "model rocket motor" or a "HP motor", the general intent of my query was clear.

So, would you say that 30 ft. is all that is required for any model (non-HPR) rocket motor (or combination) larger than a 'D'? Even for two G64Ws, which have a total combined impulse of 240 N-s, a single motor average thrust of 64 N, a single motor propellant mass of 62.5g, and a combined propellant mass of 125g, all of which fall below the HPR limits? Note that I said "required", not "desired".

 

[RimfireJim]

Originally posted by GSTARRAIDER
Not to mention, if you are using a E,F, and G motor like a aerotech blackjack propellant motor, and your only standing 15 feet away, . . .

That would be a violation of the Model Rocket Safety Code, which requires 30 ft. for these motors.
I agree, farther back gives a better view.

 

[shreadvector]

Originally posted by RimfireJim
Yes, I'm well aware of that (I have your referenced chart saved on my computer and referred to it when I wrote the first message in this thread), which is why I included the phrase "if the propellant mass is 62.5g or less". I guess I should have also included "single motor average thrust 80N or less". I was hoping that, without getting into all the details of whether a motor is a "model rocket motor" or a "HP motor", the general intent of my query was clear.

So, would you say that 30 ft. is all that is required for any model (non-HPR) rocket motor (or combination) larger than a 'D'? Even for two G64Ws, which have a total combined impulse of 240 N-s, a single motor average thrust of 64 N, a single motor propellant mass of 62.5g, and a combined propellant mass of 125g, all of which fall below the HPR limits? Note that I said "required", not "desired".

That is all that is required for that Model Rocket on the high end of the Model Rocket spectrum.

 

[metalwizard]

thats why i love flying g64's you can almost stand right next to them when you launch!!!

 

[11bravo]

If after you launch you smell burnt hair and have no eyebrows move a step or two further away for the next one.
You can never be too careful.

 

[rms]

I launch everything from B's to G's from 80 feet away. I prefer to view the launch from further back. Also easier on my neck than standing by the launch pad and looking straight up.

 

[by basher]

I give one of my kids a nickel to launch for me, so distance is not an issue.

 

[metalwizard]

I push the button, and pay the nickel for them to chase them..

 

[V'ger]

Originally posted by metalwizard
I push the button, and pay the nickel for them to chase them..

HAHA. I sometimes give the kids those mini Candy bars for recovery duties. On rockets that are fragile or important or both, I designate one child to recover, and the rest as spotters. Then they ALL get cany bars for their efforts, and only having one child runing after the model means that it doesn't get stepped on or torn in to in a tug of war match in the recovery zone!

If its a 'junk' rocket that I don't care about, I have fun by making htem compete and hussle for the rocket ... makes for some interesting recoveries!

 

[thejohnchapman]

There is an obvious difference between what is legal, and what is prudent. If you have a G-powered Machbuster - clone driving a 1/2 pound rocket the speed of sound, you'll want enough distance to react if you need to jump out of the way.

PS: The energy involved is MUCH greater than that in a .45 ACP projectile.

 

[RimfireJim]

I agree totally, John, and I agree with everyone who says the view is better farther away anyway. As I said earlier, my relay launcher has a 50 ft. cord just for that reason, and I'll certainly use all 50 ft. of it if and when I start doing G impulse launches.

I now have a better understanding of how the two codes don't overlap in the "mid-power" range. The NFPA codes do a better job of defining a model rocket motor than does the information on the NAR website and in the NAR Model Rocket Safety Code. So the surprising thing to me now is that the NAR MRSC requires only 30 ft. for the upper range of launches that still fall into the "model rocket" category, given the generally conservative and safe (appropriately) nature of the rest of the code. I would think that something along the lines of the requirements of the HPR code, i.e., increasing distances for increasing impulses, would be more appropriate. IMHO.

 

[Fore Check]

I own my very own blasting shelter/hut for surface mining production blasting.

I typically set it up within 5 ft of the pad for any impulse of motor. The sound is much more impressive that way.

 

[Fore Check]

Sometimes I just wrap myself in all my extra Nomex chute protectors and leave the blast shelter at home. I've successfully launched a 38mm Skidmark using this method while holding the launch pad.

 

[eugenefl]

Originally posted by Fore Check
Sometimes I just wrap myself in all my extra Nomex chute protectors and leave the blast shelter at home. I've successfully launched a 38mm Skidmark using this method while holding the launch pad.

Dude, where's your "do not try this at home" disclaimer?! LOL...that's just crazy! I'm just waiting to see the "You Tube" video.

LPR-HPR, I agree with the comments on standing further back. It's easier to watch and enjoy the flight.

 

[Hospital_Rocket]

Originally posted by Fore Check
I own my very own blasting shelter/hut for surface mining production blasting.

I typically set it up within 5 ft of the pad for any impulse of motor. The sound is much more impressive that way.

Oh my, an M Skidmark where you use an Estes controller to fire it!

Now THAT is truly a manly act.


Although you do get -10 manly points for the extra Nomex)


My only question now is when you are going to use RDX as a component in the ultimate L3 piston launcher.