Revision to Tripoli Rule Regarding Wireless Remote Switches

The Rocketry Forum

Help Support The Rocketry Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
Status
Not open for further replies.
There was a good description of it on the Tripoli Forum that we prepared from descriptions provided by the students. The summary is that they used an acceleration triggered timer for staging and then inserted a parachute using a sledgehammer and wooden block. There was no switch for the electronics so the electronics were directly connected to the battery while the rocket was horizontal, in clear violation of the Safety Codes. The timer triggered during the pounding and lit the sustainer motor (P or Q research motor). The students were all clustered around it trying to get it assembled to launch when it ignited. They reported seeing smoke jetting from various ports and some of them turned to run.
I was maybe a quarter mile away. A couple of the guys I was with were just on their way to check and see how the students were doing because it was getting late in the day for the high altitude waiver. They had just gotten into the truck when I heard a loud whump from the students’ direction. Others said they heard the motor launch, but all I remember hearing was that sickening whump sound. When I looked toward them all I could see was a cloud of smoke and dust with a cluster of students. The guys I was with took off in the truck. We all feared the worst, but fortunately the injuries were very minor.

Steve,

From your description in another thread, this sounds like the Q motor incident you referred to, earlier in this thread.

Dave F.
 
Another thing I thought about...we could still use the wifi enabled, magnetic, stuff as long as we have a simple switch.
I've already decided that I will be equipping all my rockets and respected electronics with the
Fingertech screw switches on the +bat side. Problem solved.

I do have a few rockets that are simply just the JST connector plugged into the bat then the nose cone placed over and will leave those alone but might use the Fingertech switches on those.

It is what it is guys.

ft_mini_switch3_lg.png ft_mini_switch4_lg.png ft_mini_switch_CAD_sm.png
 
that switch rating is only 1/2 amp- not adequate for rocketry. This is not an easy task and Tripoli has us scrambling to discover technology to solve their well intentioned but ultimately under researched ruling.
Not necessarily. That is a continuous current rating. You would have to ask the manufacturer what the peak rating would be for a 1sec burst. (or so).
 
Last edited:
that switch rating is only 1/2 amp- not adequate for rocketry. This is not an easy task and Tripoli has us scrambling to discover technology to solve their well intentioned but ultimately under researched ruling.
Not necessarily. That is a continuous current rating. You would have the manufacturer what the peak rating would be for a 1sec burst. (or so).
The design could also be using a pyro battery.
 
This post is not meant to be argumentative toward any poster in this thread. It is just my opinion...
In this case I believe the Tripoli BOD made a ruling based on a genuine concern for safety. I'm not going to browbeat any of the BOD for attempting to mitigate at least a perceived safety issue. My latest project is an air-start that was redesigned for Eggtimer wifi switches and a Quantum to handle the air-start. I had not intended to use mechanical switches to isolate power to the devices, but now I will... not a big deal.
If that makes an RSO at some launch more at ease, I'm good with it. Plus.....now you know that it is SAFE
 
The design could also be using a pyro battery.
In several altimeter designs a separate pyro battery puts the battery voltage + voltage directly on one leg of ALL the attached ematches. In that case a switch to the altimeter power does not meet the intent of the rule. You must put a break in the pyro battery leg.
 
Well, I'm certainly one of the flyers screwed-over by this, I'm grounded until I re-design everything. I've worked in consumer electronics for the past 21 years, on the border of electrical and mechanical design (consumer electronics, not military or aerospace). And nobody in the groups I work with would ever recommend moving to a mechanical solution over a solid-state one, we're always trying to figure out how to move to solid state since it's so much more reliable and predictable than mechanical solutions. Every rocket I've ever flown with electronics has either used Featherweight Magnetic Switches to inhibit the power to altimeters such as StratoLoggers, EasyMinis, RRC3 or Eggtimer TRS's (since they don't have the redundant safety of the later Eggtimer devices), or the Eggtimer Quantum or Proton based on the previous approval of these devices as being safe on their own.

I guess the part I really don't get, if the concern was armed electronics at the RSO desk or on the way to the pad, why not require altimeters to make a continuous noise when they're armed. Most already do, so the impact would be pretty minimal I think. If I walk up to the RSO table with my rocket's electronics screeching away, that's pretty obvious that I'm carrying something in an unsafe state (I'd hope to get tackled before I even got to the RSO table. :p) Without this requirement, I could still have a rocket that has armed but silent electronics even with a mechanical switch, if that switch had failed for any of the previous reasons mentioned like the loose screw vibrating into place, or a pull-pin starting to come out or getting snagged on something, a switch that had failed due to previous exposure to shock, etc. At least with a WiFi-enabled switch I can be confident that it's not powered/armed, where with a mechanical switch I simply can't be as certain. I'll grant that the magnetic switch could be activated by an unexpected magnetic force, though if you've ever used one of these things you'd know that they can be difficult to activate even with the proper magnet right next to them, the chances of this failing in reality seems even less to me than a mechanical switch failure.
 
Steve - I agree there has been a bit of whack a mole regarding this topic among various threads and forums. Please let me know if the following is a correct understanding:
  • TRA has always required that ejection charges (described as 'energetics') be inhibited until the rocket is in launching position
  • The above rule has always precluded flyers from testing continuity of ejection charges in the prep area
  • There had not been a formal definition of how the charges can be inhibited, which has lead to competing interpretations of how to inhibit a circuit
  • The TRA Board has decided to formally issue a rule that defines inhibit (based on standards that exist in the professional pyrotechnics industry) as requiring a mechanical switch that creates an open circuit either:
    • between the power supply and the flight computer
      or
    • between the flight computer and the ejection charges
  • TRA does not currently provide approval or guidance on either the selection of a suitable switch or the design and implementation of any circuits, but may form a committee to do so

And a couple of clarifications:

  • Are bare e-matches considered an energetic?
  • Does the board consider the .2cc (.2 grams) powder charge required to initiate a popular CO2 based recovery system an energetic?
  • Is a CO2 recovery system that uses a method other than an e-match to initiate the release of CO2 considered an energetic?


Tony
Also one could add to Tony's list for clarification the approximate .1cc (.1 gram) used in cable cutters.

Stan
 
Steve,

Is that the one where the Students were using a sledgehammer to seat the nose cone, with the electronics armed ?

Dave F.
Honestly, I think a lot of people have had their main blow on the pad after arming the altimeter and removing the NC/payload bay for whatever reason. Virtually every altimeter would do that, although it wouldn't be hard to put in some logic to prevent it. (Now that that I thought of it, I'll look into it...) I did it myself on a LPR cardboard rocket about two years ago... I had a Quark in it, and I was so used to the Quantum (which has a remote DISARM... just as important as a remote ARM, probably moreso), that I didn't think twice. Or once. The new rule would not have prevented THAT incident because it was already armed on the pad, but the intent of the rule is to minimize the chance of injuries of OTHERS. If you do something stupid and hurt yourself, that's on you. If you do something stupid and hurt somebody else, well, that's a problem.
 
Also one could add to Tony's list for clarification the approximate .1cc (.1 gram) used in cable cutters.

Stan
Cable cutters should be exempt because of the small amount of powder in them, and the fact that there is NO chance of injury if it pops unexpectedly, because it's contained inside the airframe and nothing external is separated when it blows. How about it, Steve?
 
I'd be interested in knowing the number of inadvertent firings before this rule was implemented compared to after. As well as any safety incident involving a rocket equipped with an energetic.
 
In several altimeter designs a separate pyro battery puts the battery voltage + voltage directly on one leg of ALL the attached ematches. In that case a switch to the altimeter power does not meet the intent of the rule. You must put a break in the pyro battery leg.
Most of the altimeters that I've seen do that, except for the Eggtimer Quantum and Proton (yes, the other Eggtimer altimeters have a battery common to an ematch leg). I had to research this when I started doing the documentation for the WiFi Switch, since it has remote continuity sensing and I had to figure out how to connect them to non-Eggtimer products. I do not know about the Marsa... I've never had anyone ask me about it, but I wouldn't be surprised if the people that own Marsa's are a bit more technically adept than most altimeter users and can figure this stuff out for themselves.
 
"that switch rating is only 1/2 amp- not adequate for rocketry."

Sure is -- will be perfectly fine.
Understand what the ratings mean and how they apply to the application.

This is the rating for constant current.

The short, few-second firing pulse of ~4A from a 9V battery won't harm the lightest of switch contacts.
The constant drain from most altimeters is very small.

BTW - I should have added above:
  • I use 4PDT switches everywhere unless fit is problem (like 38mm).
  • With 4PTD, I use two for a 4-channel altimeter and one for a 2-channel. In the 2-channel instance, there are TWO poles used to switch power. In the 4-channel instance, all four poles of the second switch are used to switch altimeter power.
  • For 38mm mini-bays, as they are also usually only 2-channel, I use two 2PDT switches that are tiny. One for the pyro's and one [with dual poles] switching power.
 
In several altimeter designs a separate pyro battery puts the battery voltage + voltage directly on one leg of ALL the attached ematches. In that case a switch to the altimeter power does not meet the intent of the rule. You must put a break in the pyro battery leg.
I get that. I was referring to the switch in question in the original post and speculating that maybe the application was just for the flight computer (but now seeing the above post, it isn't, either way OK).
 
Last edited:
I do have a few rockets that are simply just the JST connector plugged into the bat then the nose cone placed over and will leave those alone but might use the Fingertech switches on those.

It is what it is guys.

View attachment 406092 View attachment 406093 View attachment 406094

I have been using the FingerTech mini-screw switches since 2017 and I haven't had an issue. Although, to be safe, you need to unscrew them quite a bit. Based on this new rule, I will be using them to replace my magnetic switches for my altimeters, and use the magnetic switches for my nosecone trackers.

https://www.rocketryforum.com/threads/mac-performance-rainmaker-54-build.142963/page-3#post-1824191
 
I guess the part I really don't get, if the concern was armed electronics at the RSO desk or on the way to the pad, why not require altimeters to make a continuous noise when they're armed.

This a very good point. In FMEA practice a good fault detection method is just as important as prevention. You could implement your idea by simply tying a piezo buzzer across the power output of your switch, mechanical or solid state.

But then if the 'alarm' goes off you will still need a method to quickly safe the system.
 
Following a careful re-read of the original announcement, it appears that "unapproved" wireless altimeter switches MAY still be acceptable for use, just never wired up to pyro OR batteries anywhere else but at the pads downrange. I can live with that, so long as there's a table set up down there to accomplish the final preparations (connect batteries, close up avionics bay, connect pyro, install recovery system, and close up rocket) prior to rack-up, rather than nutzing around with it in the mud.

Is that an accurate interpretation of the new rule for those of us using unapproved magnetic switches as the sole means of arming/disarming their altimeters?
 
Cable cutters should be exempt because of the small amount of powder in them, and the fact that there is NO chance of injury if it pops unexpectedly, because it's contained inside the airframe and nothing external is separated when it blows. How about it, Steve?

[emoji106] That’s what I was trying to say in my response *** to Tony above.
 
Following a careful re-read of the original announcement, it appears that "unapproved" wireless altimeter switches MAY still be acceptable for use, just never wired up to pyro OR batteries anywhere else but at the pads downrange. I can live with that, so long as there's a table set up down there to accomplish the final preparations (connect batteries, close up avionics bay, connect pyro, install recovery system, and close up rocket) prior to rack-up, rather than nutzing around with it in the mud.

Is that an accurate interpretation of the new rule for those of us using unapproved magnetic switches as the sole means of arming/disarming their altimeters?

Ja, daß stimmt.
 
Anticipating the questions, I'm going to put together a document telling users how to "safe" the various Eggtimer altimeters and the WiFi Switch. It should be done in a day or two... I'll link to it at the top of the Eggtimer home page.
 
My reply is to a new rocketeer or somebody thinking about getting into this fascinating hobby. However any of these questions are posed or responded to they are generally an effort to do whats best. Someday when your doing your job such as, in space satellite repair technician, inter planetary commercial pilot, asteroid mining, weightless cancer researcher, or just on vacation for a trip around the moon. I hope you remember these words were only ideas we could discuss. And now your living our dreams.
 
Status
Not open for further replies.
Back
Top