boatgeek
Well-Known Member
- Joined
- Dec 27, 2014
- Messages
- 7,408
- Reaction score
- 7,950
FYI, the three Eggtimer devices named in this TRA rule break power to the attached device (WiFi Switch) or the deployment circuitry (Quantum, Proton) until explicitly armed, by entering a 4-digit arming code that changes every 60 seconds. You can't "pocket arm" them.
This is what I was missing in the conversation. In order to have the Egg devices blow the ejection charge, you would need three failures:
Arm altimeter
Electrical/software failures on both legs of the ejection charge
That's pretty danged unlikely (technical term), particularly with a 4-digit code entry required to arm the altimeter.
On the other side, I have personally had one failure in a couple of dozen flights on a twist and tape connection (saved by a redundant altimeter), two failures in three installations with Schurter switches, and no failures in three installations with screw switches. I can re-jigger my procedures to connect charges on the pad, but my own limited experience indicates we're trading an extremely unlikely event (altimeter accidentally firing the ejection charge) with a somewhat more likely event (failure of the switch/T&T on the ejection charge). Considering the relative hazard of an ejection charge blowing versus a rocket coming in ballistic, I don't see this as a safety improvement. Nobody wants to have an ejection charge blow in their face, but I'm having real trouble with equating a 0.2g separation charge with a lawn dart.
All of that said, most of the people on the thread opposed to the rules are just saying they don't like the rules. To counter that a bit, here's a counterproposal from Some Dude on the Internet (worth exactly what you paid for it ). In my dream world, the rules would be:
On staged flights with AP motors, don't connect the sustainer igniter before getting to the pad and don't insert igniter until the deployment altimeter is armed.
You may connect small ejection charges (<3-5g?) to a Wifi-controlled altimeter (WCA) and turn the WCA on before going to the pad, but the rocket must be carried vertical or pointed in a safe direction at all times. The WCA must require an entered code to arm (or equivalent that prevents pocket dialing).
For larger ejection charges, altimeter may not be turned on before reaching the pad.
Wifi switches OK as long as they require an entered code to arm. I like the concept of the mag switches but I haven't actually used one so I can't comment on how to use it safely.
Do not arm the altimeter or turn on non-WCA altimeters until the rocket is vertical on the pad.
I feel like this is a good balance between simplicity for smaller rockets and better procedures. I'm probably wrong in some respects. Tell me why, and what your alternative would be.