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Required Launch field sizes, etc.

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Peartree

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I've been reading through the copy of "High Power Rocketry 2" that I bought at NARAM-51 and last night was particularly looking at the required field sizes for various motors and something stuck out that has been bothering me.

How do many of our launches comply with this regulation (since its basis is in the NFPA code it *is* a regulation and not an organizational guideline)? According to the charts, a half mile square field would just be large enough to fly H and maybe I motors while I know of many launches on fields that size that have allowed much larger motors. The field for NARAM-51 by size alone would barely have been big enough for B and C motors based on its width but H's and I's were flown. Even the well known sod farm used at Southern Thunder at one mile square would only allow an L or maybe a small M. The code seems to indicate an area free of trees but are we basing our usage on fields beyond the launch field?

If we go purely "by the book," it would seem that many of our launches are significantly over-powered for the field size.

What am I missing?
 

H_Rocket

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One - Why do you need such a big place for "Lunch"

Two - If we went "by the absolute letter of the book and did not allow any trees in our recovery area, you are correct. In fact Given that, you would not be able to fly a J motor at MDRA - a place where an O is considered hum-drum...

The rules are there to promote safety, however common sense must also apply.

I do believe we are hamstrung by range rules written when an E motor was big and rewritten when a G motor was huge (With the same "E motor is big" mindset. I do wish the folks that lead our organizations would consider the fact that urban sprawl is slowly choking off our hobby in a manner that the BATFE could only aspire to. Then take a true leadership position and carefully look at all the rules with an eye towrds re-designing them for the current day.
 

JRThro

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The field for NARAM-51 by size alone would barely have been big enough for B and C motors based on its width but H's and I's were flown.
I sure hope someone can clarify that one.
 

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I thought the launch field was 5000 X 2400 ft at the Windber location, at least that's what it said on the website. Or were those the dimensions for the orginal site? It seemed about that size to me. Though the sport pads were set up probably 1000 ft from the power lines, and the wind was blowing across the skinny side of the field towards the power lines when I was there. If the winds were blowing in the lengthwise direction things would have been better.
 

Peartree

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I thought the launch field was 5000 X 2400 ft at the Windber location, at least that's what it said on the website. Or were those the dimensions for the orginal site? It seemed about that size to me. Though the sport pads were set up probably 1000 ft from the power lines, and the wind was blowing across the skinny side of the field towards the power lines when I was there. If the winds were blowing in the lengthwise direction things would have been better.
Okay, I didn't get measurements, but other than really slow and heavy stuff, I wouldn't fly anything bigger than a B motor most of the time. Not after seeing all the bigger rockets decorating trees or worse. At the sport range, the pads were no more than 100 ft from the trees/over the hill and I doubt that they were much more than a few hundred feet from the telephone wires/trees on the other side. The competition range had a bit more room.

[edit] Okay, I took a look at Google Earth and the field look a LOT bigger than I remembered... At least until I realized that the photos were from 2005. When I zoomed in enough to recognize features from the launch, most of what looked huge on Google was overgrown with brush and the narrow dimension of the field was more like 350 ft. on the sport range.

I'm not saying Pittsburgh didn't do a great job (they did) or that we didn't have an awesome time (we did), just that I seem to be a little unclear on the rules or something.
 
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MarkII

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I thought that the Windber site was HUGE; easily the biggest field that I have ever launched in. (Almost double the size of the next largest field.) Hey it was big enough to host TWO separate ranges (three, if you count the RC range, which I didn't see being used when I was there). In some ways it might have not seemed like good site setup to put the sport range was at the narrow end of the field, but I could see the rationale for locating it there. It was the furthest point from the cluster of houses in Paint (I think that's what we drove though to get onto the field) and in that location, the high flying sport rockets had the entire field to drift over (if necessary) for recovery. The sustainer in my two-stager needed absolutely ALL of the site to come down in. I found it just about as far out in that wildflower field that you could get. And it made sense to put the competition and RC ranges in the wider part of the site, because both of them really needed the elbow room even though their rockets didn't go as high. (And the competition is NARAM's raison d'être.) Given the expected direction of the prevailing winds, it made sense to put the sport range down at the most windward end of the field. I am very glad the PSC did that, because it worked out for me.

I also found what appeared to be the nose cone to Russ Cummings' Rubicon out in that same field while I was searching for my rocket and I brought it back to the Lost and Found box. Apparently the layout worked out for him, too.

I did see the Level 2 cert flight on the J on 8/9 that ended up on the power lines. Given the very gusty conditions that day, I thought that it was kind of risky making that flight. But you know what they say, no guts, no glory. He gambled and lost. (I don't know what the eventual result was or if he ever got his rocket down.)

The field seemed to me to be shaped like a long triangle, with the Away pads of the sport range located at the peak and at the most windward end of the field, right where you would want them to be. Considering that it was a backup site and not the originally planned location, I thought that PSC did an incredible job of making it work. I think that the experience they had from having previously hosted a NARAM really showed.

MarkII
 

bobkrech

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There are two requirements for high power fields.

1.) Launch Site. An open area where trees, power lines, buildings, and persons not involved in the launch do not present a hazard, and that is at least as large on its smallest dimension as one-half of the maximum altitude to which rockets are allowed to be flown at that site or 1500 feet, whichever is greater.

2.) Launcher Location. a.) The launcher shall be located at least 1500 feet from any inhabited building or from any public highway on which traffic flow exceeds 10 vehicles per hour, not including traffic flow related to the launch, and b.) also shall be no closer than the appropriate Minimum Personnel Distance from the table in the NAR High Power Safety Code from any boundary of the launch site.

http://www.nar.org/NARhpsc.html

Issues and interpretations

1.) Since you need at least 1500' clearance all around the launch pad, the default field diameter is 3000' which becomes the minimum dimension so the maximum allowable altitude is 6000'.

2.) If the actual field diameter is not 3000' in diameter, but condition 2.a.) is met, the minimum dimension must be at least 1500' by condition 1.) and therefore the maximum allowable altitude would be 3000', or twice the minimum dimension.

3.) Your FAA waiver altitude may be less than the maximum allowable altitude due to ATC requirements.

4.) When the wind velocity exceeds 5 mph, you must lower the maximum allowable altitude to insure infield recovery. http://www.nar.org/pdf/launchsafe.pdf

5.) Field dimension examples. http://www.nar.org/pdf/Safety_in_Sport_Rocketry_Tutorial.pdf
 

JRThro

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So... based on what bobkrech posted, was the NARAM-51 field big enough to fly the rockets that were being flown?
 

billspad

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The code seems to indicate an area free of trees but are we basing our usage on fields beyond the launch field?

I assume you mean this:

Launch Site. I will launch my rocket outdoors, in an open area where trees, power lines, buildings, and persons not involved in the launch do not present a hazard, and that is at least as large on its smallest dimension as one-half of the maximum altitude to which rockets are allowed to be flown at that site or 1500 feet, whichever is greater.



I think that's vague enough to give you a lot of latitude. I'd argue that the only thing the trees present a hazard to is the recovery of my rockets. I did that successfully at NARAM three times with my rockets and couple of times with other people's with little damage to the rockets, trees or me.
 

billspad

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So... based on what bobkrech posted, was the NARAM-51 field big enough to fly the rockets that were being flown?

It was big enough to cover the safety aspect. However, I saw a few flights that fell short of sanity. When you're flying on a field surrounded by trees some simple math will tell you that if you fly to a x feet, your rocket is falling at 15 fps and there's a Y mph wind you are guaranteed to have a tree landing. Of course even after you've done that and have calculated that if you fly out over the trees the wind will bring you back to the open space you're still out of luck when the chute opens late, one motor in the cluster lights late or the wind changes direction. Any fool can recover a rocket in the desert. Flying from a treed field is an art.
 

billspad

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That's news to me. Where exactly in the current or proposed safety code does it state this? I can't find it. I looked, what page?

It doesn't say it exactly but if you take the minimum field size and maximum altitude for that field and assume the rocket is dropping at 15 fps you'll see that at anything over 5 MPH you're out of the field and the Flight Safety part of the High Power Safety Code says "I will not launch my rocket at targets, into clouds, near airplanes, nor on trajectories that take it directly over the heads of spectators or beyond the boundaries of the launch site". I suppose you could say that if you launch it straight up to 3000' on a day with 19 MPH winds that the rocket isn't on a trajectory that would take it out of the launch site and that it just drifted out on the way down but, at least were we fly, you're never going to see the rocket again.

That document that Bob referred to has a lot of good stuff in it. To be honest, we didn't pay that much attention to those things in the past but we have in the last few years and I've found our launches to be much more enjoyable.
 

bobkrech

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That's news to me. Where exactly in the current or proposed safety code does it state this? I can't find it. I looked, what page?
From the NAR High Power Safety Code http://www.nar.org/NARhpsc.html

Flight Safety. I will not launch my rocket at targets, into clouds, near airplanes, nor on trajectories that take it directly over the heads of spectators or beyond the boundaries of the launch site, and will not put any flammable or explosive payload in my rocket. I will not launch my rockets if wind speeds exceed 20 miles per hour. I will comply with Federal Aviation Administration airspace regulations when flying, and will ensure that my rocket will not exceed any applicable altitude limit in effect at that launch site.

Interpretation: All recoveries must be made within with launch field. The nominal descent rate under parachute of a high power rocket is 15 fps or 10 mph. You are allowed to launch a high power rocket to an altitude not to exceed twice the minimum field dimension or 1500 feet, whichever is greater which means the minimum field dimension allows for a maximum altitude of 3000 ft. In a 10 mph wind a rocket will drift sideway 1 ft for every ft of altitude if the recovery system employs apogee deployment, so to insure an infield recovery, the maximum allowable atitude for an apogee deployment is reduced to 1500' when the wind exceeds 5 mph and remains below 10 mph. Above 10 mph, the maximum allowable altitude must be further reduced to as low as 750' when the wind is above 15 mph to the maximum allowable launch wind speed of 20 mph. This is explained in detail in http://www.nar.org/pdf/launchsafe.pdf

This is the best reason to employ a two stage deployment system in a high power rocket as the initial descent after apogee is typically 60 fps and the main can be deployed at 300' to minimize drift.

Bob
 
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Peartree

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I assume you mean this:

Launch Site. I will launch my rocket outdoors, in an open area where trees, power lines, buildings, and persons not involved in the launch do not present a hazard, and that is at least as large on its smallest dimension as one-half of the maximum altitude to which rockets are allowed to be flown at that site or 1500 feet, whichever is greater.



I think that's vague enough to give you a lot of latitude. I'd argue that the only thing the trees present a hazard to is the recovery of my rockets. I did that successfully at NARAM three times with my rockets and couple of times with other people's with little damage to the rockets, trees or me.

That's probably close. My question was actually prompted by reading "Modern High Power Rocketry 2" p. 121 where it says, "For example, NFPA 1127 requires that all spectators at a high-power launch remain behind the RSO and the person launching the rocket. A high-power rocket shall be launched only in an outdoor area where tall trees, power lines and buildings do not present a hazard."
 

Peartree

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While I wonder at how some of our launches comply, what I'm getting at is this: I'm looking for a field nearer to home where we can have HPR launches. Cleveland and Columbus have large fields but their proximity to major airports limits the altitude waiver they can get. I have some fields in mind up to 4/10 of a mile square (and one or two with a long side and a short side) but "by the book" these still wouldn't be big enough even though beyond the trees on their boundaries are still more open fields.

Would these qualify or not?

If they are ONLY 4/10 of a mile, what moors could be flown?
 

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Interpretation: All recoveries must be made within with launch field. ....

This is the best reason to employ a two stage deployment system in a high power rocket as the initial descent after apogee is typically 60 fps and the main can be deployed at 300' to minimize drift.

Bob
Ok I got it. Now here's an interesting question. Do you get dispensation on the maximum altitude with a dual deployment flight or is the maximum altitude determined by assuming an apogee main?
 

billspad

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While I wonder at how some of our launches comply, what I'm getting at is this: I'm looking for a field nearer to home where we can have HPR launches. Cleveland and Columbus have large fields but their proximity to major airports limits the altitude waiver they can get. I have some fields in mind up to 4/10 of a mile square (and one or two with a long side and a short side) but "by the book" these still wouldn't be big enough even though beyond the trees on their boundaries are still more open fields.

Would these qualify or not?

If they are ONLY 4/10 of a mile, what moors could be flown?
For what it's worth, I'd say you can fly to 8/10 of a mile as long as you can maintain the 1500' setback to occupied houses or roads and you can get a waiver for that altitude. Motor size is irrelevant except for personnel setback distances.

I think the confusing part of the safety code is that some of it is based on altitude, some is based on motor size, and the rest is based on something else.
 

Handeman

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From the NAR High Power Safety Code http://www.nar.org/NARhpsc.html

Flight Safety. I will not launch my rocket at targets, into clouds, near airplanes, nor on trajectories that take it directly over the heads of spectators or beyond the boundaries of the launch site, and will not put any flammable or explosive payload in my rocket. I will not launch my rockets if wind speeds exceed 20 miles per hour. I will comply with Federal Aviation Administration airspace regulations when flying, and will ensure that my rocket will not exceed any applicable altitude limit in effect at that launch site.

Interpretation: All recoveries must be made within with launch field. The nominal descent rate under parachute of a high power rocket is 15 fps or 10 mph. You are allowed to launch a high power rocket to an altitude not to exceed twice the minimum field dimension or 1500 feet, whichever is greater which means the minimum field dimension allows for a maximum altitude of 3000 ft. In a 10 mph wind a rocket will drift sideway 1 ft for every ft of altitude if the recovery system employs apogee deployment, so to insure an infield recovery, the maximum allowable atitude for an apogee deployment is reduced to 1500' when the wind exceeds 5 mph and remains below 10 mph. Above 10 mph, the maximum allowable altitude must be further reduced to as low as 750' when the wind is above 15 mph to the maximum allowable launch wind speed of 20 mph. This is explained in detail in http://www.nar.org/pdf/launchsafe.pdf

This is the best reason to employ a two stage deployment system in a high power rocket as the initial descent after apogee is typically 60 fps and the main can be deployed at 300' to minimize drift.

Bob
Bob, I would have to disagree with the interpretation that all recoveries must be in the launch site. The reason is, I don't interpret trajectory to include the portion of the flight when the recovery system is deployed. I read this as: you can not launch in a direction that goes over peoples heads and the trajectory, if completed without interruption of the recovery system, can not take the rocket out of the launch site (no lawn darts outside the launch site). I would say a flight that stays under the waiver and is straight up, would be within the safety rule even if the apogee deployment of the chute will cause it to drift off the launch site.

With that said, I completely agree with limiting flights to an altitude that will be recovered on the launch site. I think that is an excellent rule. I just don't think the source of that rule should be stated as coming from the safety requirements.
 

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I think the placement of the launch area inside of the required 'boundary' area sometimes becomes a problem. We were doing the FAI duration events at NARM on the far east side of the field and had a west wind. The rockets were outside of the boundary of the field within maybe 15-20 seconds. Didn't matter how large the entire site was because we weren't taking advantage of it.

NARAM 49 had the flyoffs where there was an unusual east wind and we were at the far west side of the field. Nearly 100% of the rockets drifted over and into a field of corn.

I realize the difficulty of moving the range head at the last minute due to a wind change but at least with N51 they had already decided to set it up on the east side of the field where the winds are presumably out of the west for the most part.
 

billspad

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I think the placement of the launch area inside of the required 'boundary' area sometimes becomes a problem. We were doing the FAI duration events at NARM on the far east side of the field and had a west wind. The rockets were outside of the boundary of the field within maybe 15-20 seconds. Didn't matter how large the entire site was because we weren't taking advantage of it.

NARAM 49 had the flyoffs where there was an unusual east wind and we were at the far west side of the field. Nearly 100% of the rockets drifted over and into a field of corn.

I realize the difficulty of moving the range head at the last minute due to a wind change but at least with N51 they had already decided to set it up on the east side of the field where the winds are presumably out of the west for the most part.
Those were all model rockets. Unlike the High Power Safety Code the Model Rocket Safety Code doesn't mention staying in the field.

It does say "I will not attempt to recover my rocket from power lines, tall trees, or other dangerous places. " So evidently I was violating the safety code when I used the 50' pole to get my rocket out of a tree.
 

Pat_B

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I wasn't thinking so much about the safety code as compared to the common sense of at least setting the range up so that the duration model rockets can at least have a chance to be seen and recovered downwind-- at least for a reasonable distance.

In the case of N51, it turned the duration contests more into a matter of visibility because of the slope of the area and tree lines. It was especially bad with the high winds that were at that location. That's unfortunate because the launch site location really negated a lot of the skill needed for these events because it was more just a visibility issue. All of that could have been prevented by moving to the far west edge of the field. At least if the rockets went out of site below the tree line then those would have been the higher performing rockets to begin with because they would have had to peform pretty well in a thermal to get that far.
 

bobkrech

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Ok I got it. Now here's an interesting question. Do you get dispensation on the maximum altitude with a dual deployment flight or is the maximum altitude determined by assuming an apogee main?
The job of the safety check/RSO is to determine if a rocket can make a safe flight. If the answer is no, the rocket doesn't make it to the pad.

If the answer is yes, it can be launched provided the safety check/RSO is convinced the rocket has a high probability of operating as planned, and that if a flight anomoly occurs, no people will be injured and no property will be damaged.

There's 4 possible anomolies in a dual deployment recovery.

A cato during powered flight. This is handled by maintaining launch separation distances.

A ballistic impact due to total deployment failure. This is handled by field layout and angling the launch rod/rail to control the flight trajectory, and by keeping people out of the balllistic recovery zone.

A high speed recovery due to a main parachute deployment failure. This is handled field layout and by angling the launch rod/rail to control the flight trajectory, and by keeping people out of the high speed recovery zone.

Main deployment at apogee. The probability of this occuring can be minimized by employing shear pins on the main compartment, and preflight check to insure that the charges have been properly wired. While an accidental apogee deployment of the main is an undesirable anomoly, it is not necessary unsafe, but may result in an out of field landing on windy days. IMO it's a judgement call by the RSO after an assessment of the wind conditions, and consquences of an apogee deployment whether or not the filght should be allowed.

Bob
 

jderimig

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Main deployment at apogee. The probability of this occuring can be minimized by employing shear pins on the main compartment, and preflight check to insure that the charges have been properly wired. While an accidental apogee deployment of the main is an undesirable anomoly, it is not necessary unsafe, but may result in an out of field landing on windy days. IMO it's a judgement call by the RSO after an assessment of the wind conditions, and consquences of an apogee deployment whether or not the filght should be allowed.

Bob
So a hypothetical. A dual deploy flight is OK'd by an RSO. An inadvertent apogee main causes an out of field recovery which causes damages. Is that an insurance voiding safety code violation?

Out of field recoveries is not a rare occurrence.
 

bobkrech

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So a hypothetical. A dual deploy flight is OK'd by an RSO. An inadvertent apogee main causes an out of field recovery which causes damages. Is that an insurance voiding safety code violation?
IMO No.

Out of field recoveries is not a rare occurrence.
It all depends how your club runs its' launches. If everyone understands what the rules are and the safety check/RSO do a reasonable job of checking the rockets before launching and isn't afraid to say no when there's a high probability that a rocket will not recover in-field, you won't have many out of field recoveries.

We used to have several high power flights land out of the field on any given launch until four years ago when we had more than a handful leave the field during a launch that included the electric company shutting down a power line to get a low hanging rocket of a residential street, and a visit from the local police.

Since our field is the only high power field in eastern MA and we wanted to insure that we would continue to be able to launch from it, we instituted new field rules (This was a few months before Launch Safe was published.). We made it clear to everyone that in-field recoveries are mandatory, and that if you have an out of field recovery, your high power launching is done for the day.

It was very effective. Each year we'll have several dozen high power rockets land in a swamp or the woods that are part of the launch field, some of which are not recoverable, but the high power out of field recoveries at CMASS launches over the past 3 years has been about 1 per year, or ~<1% of the hgh power flights.

Folks may complain, but it can be done. In-field recoveries mean fewer lost rockets and with high power rocket costing several hundred dollars or more, folks save money.

Bob
 
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