I like the idea of pad crew actuated safeties, but in the end the crew is
still standing next to the rocket when the safety is armed just before they
leave the pad. So you still need to be fully confident that the vehicle is
not going to operate itself uncommanded when in armed state, and that
procedures and communication between the operator and pad crew are known
and rehearsed.
You should absolutely have at least two people for your launch operation,
one on the pad and one keeping an eye on the telemetry while reading off
the checklist ('test conductor'). If you plan to be the pad crew, you can
go from 'red crew' to 'command' when you finish pad ops, with TC continuing
to read the checklist.
For your specific situation I'd just have a power disconnect for the
ignition system at least fifty feet from the rocket, with turning that
power on as the last thing the pad crew does as they retreat. Have a clear
line of escape for the pad crew so that if the valves operate uncommanded
that they can simply run away.
Do a dry run of the entire operation, including hooking up lines but not
flowing propellants. Your transition to launch is going to need to go
smoothly because you don't have a lot of time margin on the LOX after you
disconnect.
Ben
On Sunday, November 8, 2015, Robert Watzlavick <rocket@xxxxxxxxxxxxxx>
wrote:
I'm working on the power electronics for my liquid rocket and I'm trying
to decide the best way to handle safing of the vehicle during pad
activities. The absolutely safest way is to just turn off all power to the
vehicle during propellant loading and troubleshooting but I'd like to keep
the avionics (IMU, pressure sensors, etc.) powered and warmed up for best
stability. The valves are controlled via RS-232 servos (AX-12) so there's
little chance they would get an uncommanded actuation. I thought about
having a SAFE/ARM switch that controls power to the igniter CDI, igniter
valves, recovery system, and maybe also the servo valves (main, vent,
helium). However, I'd want to make sure that switch is appropriately
vibration and shock rated so I don't get intermittent power interruptions
when the vehicle is operating. What has been done in the past? Here's a
good question - if you were helping me out on the pad, what level of safing
would you want to see for your personal safety?
Thanks,
-Bob
