Playing devil's advocate for a minute:
Is there a path to getting things like this removed/modified in the NFPA? The more I've thought about this rule, the more I'm confused about how requiring electronic recovery makes the flight safer.
Working from the assumption the number one goal of the NFPA code is a safe flight:
1) Adding electronics add a potiental source of error. While our modern flight computers are really good they do fail occasionally.
2) The addition of electronics adds an opportunity for more human error. System configuration, batteries, connectors, etc all need to be correct for the system to work.
3) Since the number one goal is recovery deployment, all of the other advantages of electronics (deploy at apogee) are irrelevant.
4) The actual delay timing is mostly irrelevant as long as it doesn't happen during the motor burn; again, the goal is just recovery and the condition of the rocket doesn't matter as long as it lands under chute.
With all that in mind, and the fact motor ejection is extremely reliable, why force people to take the extra risk of using electronics?
Obviously, using redundant altimeter changes this and the redundancy should make a flight safer and there are other advantages to electronics (dual deploy, apogee deploy). There is also the issue that big rockets may need more black powder in the ejection charges than comes with the motor or fits in the forward closure but that issue in not intrinsic to motor ejection. The biggest issue I see with motor ejection of larger rockets is that it makes ground testing deployment charges more difficult.
What am I missing? What risks are we buying down by requiring the use of electronics? And do those risks actually outweigh the risks are adding? Should the rule be revised to require redundant electronics for large motors or eliminated altogether?
First of all, people talk about “the NFPA” as if it’s some government or adversarial entity. It’s not. All the rules in NFPA 1122, 1125, and 1127 are there as a result of the work of the NFPA Pyrotechnics Technical Committee, which consists of representatives from the fireworks industry, Rocketry organizations, rocket motor manufacturers, government agencies, and interested private parties. Both Tripoli and NAR have primary representatives and alternate representatives on the committee. NAR’s representative co-chairs the committee. I’m on the committee as the alternate for Tripoli; Ken Good is our Primary representative. In other words, the NFPA is us.
The committee meets every couple years. Between those meeting are periods where anyone can suggest new rules or changes to rules using the tools available on the NFPA site for each standard. The committee reviews those suggestions and votes on them.
The NFPA was formed so that the people most directly involved could get together and come up with wording which could then be adopted as Uniform Fire Code. Until these standards are adopted they have no real power. When they are adopted, they are adopted as a specific revision, so you might find that one state has adopted the 2013 revision of NFPA 1127 whereas another has adopted the 2018 revision and yet another is still back at 2009 or so.
To avoid that confusion both NAR and Tripoli simply choose to comply with the most recent revision.
The rules that exist within NFPA 1122, 1125, and 1127 are rules that have evolved. They started out as NAR and Tripoli Safety Code, were then written into NFPA, and have been evolving ever since. It’s highly unlikely a rule would be adopted within the Rocketry codes without NAR and Tripoli acceptance. It’s also highly unlikely a rule would be vacated without NAR and Tripoli approval.
The article by Alan Whitmore in the Tripoli Report that I mentioned a few pages back was specific in its recommendation: if you want accuracy in your apogee event, use electronics. Burning delay grains are just not very accurate. My experience reflects that. I have almost never witnessed the failure of a commercial rocketry altimeter. In the nearly 22 years since I first got into high power Rocketry I have witnessed probably hundreds of failures of delay grains in one way or another. As the manufacturers pointed out larger motors have even more delay variability. There’s a reason why experienced flyers often say “once you start using electronics you’ll never go back.”
So, no, we are unlikely to remove the rule requiring electronics for a rocket that has more than 2560 Ns total impulse.
