Hello Tom,
I am very sorry that I didn’t follow up on this last year after a couple of people responded to my input against “arming switches” at the pads. But I was just doing a search for Wilson F/X topics here on the TRF and came across this one again. I cannot leave this where it got left because I fear that you might get left with the idea that an “arming switch” at the pad is a good idea. It is not. And here are my reasons why.
First off, there is a huge difference between a switch for making a pad “safe” for attaching igniter clips to igniters and a switch at the pad that allows the flyer to “arm” the pad. Apparently, there are those who think that a switch to “safe” a pad and an “arming” switch are the same thing. They are NOT. Anybody can add a switch to “safe” a set of igniter leads. All you have to do is put an on/off switch on the positive side of the igniter leads going to the pad and one instantly has a switch to “Safe” the igniter leads. It might be difficult with some systems to tell which is the “positive” side of the igniter leads. But you could use a switch on both sides of the igniter leads if you’re not sure.
Now let’s talk about “arming” switches as they are a very different kettle of fish from a switch to “safe” a set of igniter leads. The idea of an “arming” switch is to supposedly make a pad completely safe from an accidental igniter firing by the flier, the guy next to the flier, and even from an LCO who doesn’t know what he’s doing. It seems like a great idea. “Let’s keep everybody from accidentally firing igniters when they are at the pads.” It is a great idea except for the simple fact that any analogue circuit capable of “arming” a pad is also going to be capable of firing the pad. And I believe that this is a violation of both the NAR and TRA safety codes. No pad should be armed when there is anyone who is not outside the danger zones delineated in the safe-distance tables of both organizations.
But let’s talk about “arming” switches at the pads for those who think they are allowed by the safety codes. There are the clubs out there with home-made systems with “arming” switches at the pads that just occasionally launch rockets when the flier “arms” the pad out at the pads. One such club’s system has fired M motors when the flyer armed the pad 30 feet from the rocket. Any system that has the possibility of firing a pad when it is gets “armed” is NOT a safe system. I know of a club with a home-made system that has this very problem. The members of the club were told that if they spent $1800 it would fix the problem. Well they spent the $1800 only to discover that the problem was still there.
A member of that club sent me the schematics of the club’s then current system and the schematic of the “fix” that would supposedly solve the problem. I emailed him back saying that the “fix” would not solve the problem. Why not? Because the problem was in the design of the system itself and the $1800 solution would not fix that. The member was told that I did not know what I was talking about. Well it is true that somebody didn’t know what they were talking about, but it wasn’t me. The fix failed and that club now owns a vastly more expensive than a Wilson F/X launch system, that still is not safe.
Now let’s talk about the accidental LCO firing of a pad while the flier is still at the pad. First off, there is no way to stop an LCO from doing something stupid without using a separate second “fire authorization switch” that the LCO does not control. (btw - Wilson F/X has just such a switch available for clubs that want a second person “fire” authorization) But let’s get back to the LCO with a problem. Any launch system safe enough to use ought to have some kind of WARNING at the pads that a particular bank of pads has been “armed” accidentally or on purpose. There should be at least a screeching buzzer that warns people of the “arming” of a bank of pads. That way, if they hear the screeching buzzer they know to get away from the pads A.S.A.P.
Secondly, it is true that an LCO might accidently leave a bank of pads armed and a pad “selected.” But if the precaution of the screeching buzzer for an “armed” bank of pads was already in place, the flyers would know it BEFORE they actually approached the pads that were still armed. If the “armed” bank of pads warning is not automatically in place, then it is NOT a safe system. An “armed” pad is a dangerous pad for the very reason that it is “armed.” An “armed” pad can be fired. And according to the simplest interpretation of both the NAR and TRA safety codes, no pad should be armed if there is anybody closer than the minimum safe distance table specifies. So it is my belief that any system that can be “armed” by the flier is not only unsafe, but is in violation of both the NAR and TRA Safety Codes. The solution to an unsafe LCO cannot be to add another layer of un-safe technology. Adding another layer of problems to an existing problem is not a solution to the problem.
I know that these are just my opinions, but as somebody who started building analogue club sized launch systems back in the late ’60’s and into the ‘80’s, I know a thing or two about club launch systems. As soon as I got into high power rocketry back in 1991, I started studying the then current technology of club launch systems. I went all over this country flying with dozens of high power clubs and I studied their launch systems. I repeatedly saw the same problems: sticking relays from unregulated relay activation voltage/amperage circuitry; those same sticking relays firing igniters when the igniter leads were hooked up; a pair of wires from every pad all the way back to the Launch controller on the LCO table causing massive amounts of wire on the ground; CAT5 cables used to try to fix this problem but failing in long term usage; mostly poorly designed continuity testing circuits at the pads that were not safe; rats nests of wiring inside launch controllers that made building difficult and repairs even harder; accidental firing of pads when launch controller switches were changed between different banks of pads from sparking rotary switches; and lastly, far too many clubs that had to spend countless hours repairing their club launch systems between launches just to keep them operating even at a poor level of quality. Every single one of those clubs was doing its best utilizing basic analogue technology from the 1980’s. It mostly works ok for a while, but it is simply obsolete tech.
This is exactly why back in 1994, Wilson F/X technology was first created: to fix all of those problems. And we continue to add innovative solutions to the problems and demands of today’s rocketeers and rocket clubs. I’m not here to pick on anybody, but you need to know that not everything you read, even here on the TRF, is well reasoned or a wise way of doing things.
Brad
TRA #01630 L-3 TAP
NAR #70929 L-3 L3CC