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Another discussion about how best to use field space led me to look at my across-the-street field on Google Earth and then to contemplate the NAR safety code launch site dimensions requirements. It occurs to me that it is yet another example of an error in denominator selection, of which I have encountered several notable ones in this hobby. The basic problem is that the site dimensions are tied to motor size, not apogee height.
Consider, for example, a Citation Patriot and a Wizard. Both are well-liked, popular models with long production history from the industry giant. Both have essentially the same recommended motors. The Citation Patriot is advertised to fly to about 600 ft (presuming the largest motor, a C6-5). The Wizard is advertised to fly to about 1600 ft on a C6-7, the exact same impulse. The NAR safety code requires minimum site dimensions of 400 ft for any rocket flying on a C. Likely reasonable with the CP, obviously a foolish decision with the Wizard.
This set of guidelines, because it's published by the NAR as part of its fundamental safety practices, in various locations and circumstances may actually carry the weight of law. And yet, it's laughable as an actual guide, as is obvious immediately to anyone with a lick of common sense who thinks things through. In reality, every rocketeer is burdened to apply reasonable judgement to the circumstances present at launch and conduct themselves accordingly, and the NAR site size guidelines are frankly of so little help as to be useless. Maybe they're intended for middle of the road rockets like Alpha, Der Red Max, or the range of ARF stuff that's available. Fine, but it doesn't say that, and there's nothing to prevent a kid and her parents who pick up a Hi-Flier, 220 Swift, or similar kit for their first try at model rocketry from following the rules as written, and to their detriment. Essentially, if a rocketeer follows these guidelines without overriding them completely with their own judgement and flies a random selection of commercially available kits built according to the instructions on recommended motors, said rocketeer will inevitably run into trouble.
The most basic question in deciding whether an otherwise reasonable site is appropriately matched to a flight is, "How high will it go?" Wind is a factor, descent rate, etc. But if you were to put together a chart of launch site dimensions vs. one variable, making some assumptions about the other factors all being within typical ranges, that one variable would have to be apogee. Using motor impulse instead of apogee turns the guideline into a clear example of garbage-in-garbage-out.
If a guideline is wildly inadequate and fundamentally misconceived, what's the point of even publishing it, let alone embedding it as part of the most fundamental document directing the overall safety of the hobby?
Consider, for example, a Citation Patriot and a Wizard. Both are well-liked, popular models with long production history from the industry giant. Both have essentially the same recommended motors. The Citation Patriot is advertised to fly to about 600 ft (presuming the largest motor, a C6-5). The Wizard is advertised to fly to about 1600 ft on a C6-7, the exact same impulse. The NAR safety code requires minimum site dimensions of 400 ft for any rocket flying on a C. Likely reasonable with the CP, obviously a foolish decision with the Wizard.
This set of guidelines, because it's published by the NAR as part of its fundamental safety practices, in various locations and circumstances may actually carry the weight of law. And yet, it's laughable as an actual guide, as is obvious immediately to anyone with a lick of common sense who thinks things through. In reality, every rocketeer is burdened to apply reasonable judgement to the circumstances present at launch and conduct themselves accordingly, and the NAR site size guidelines are frankly of so little help as to be useless. Maybe they're intended for middle of the road rockets like Alpha, Der Red Max, or the range of ARF stuff that's available. Fine, but it doesn't say that, and there's nothing to prevent a kid and her parents who pick up a Hi-Flier, 220 Swift, or similar kit for their first try at model rocketry from following the rules as written, and to their detriment. Essentially, if a rocketeer follows these guidelines without overriding them completely with their own judgement and flies a random selection of commercially available kits built according to the instructions on recommended motors, said rocketeer will inevitably run into trouble.
The most basic question in deciding whether an otherwise reasonable site is appropriately matched to a flight is, "How high will it go?" Wind is a factor, descent rate, etc. But if you were to put together a chart of launch site dimensions vs. one variable, making some assumptions about the other factors all being within typical ranges, that one variable would have to be apogee. Using motor impulse instead of apogee turns the guideline into a clear example of garbage-in-garbage-out.
If a guideline is wildly inadequate and fundamentally misconceived, what's the point of even publishing it, let alone embedding it as part of the most fundamental document directing the overall safety of the hobby?
