Pyrotechnic ("Pyro") node requirements

For the pyrotechnic node (PYRO) and the avionics power system (APS).

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Requirements

Parts cost <150$ in small quantities
Board size (,39,45)cm^2
Board height (,,12)mm
Time to prep the pyro node when setting up for launch (,10,30) min
Accelerometer saturation minimum positive saturation level (20,25,)gee
Accelerometer saturation maximum negative saturation level -(10,25,)gee
Capacitive discharge energy storage (20,50,100)mJ
Battery capacity of HAP sufficient for (2,,)hr operation in active state.
No single point failures which compromise safety.
Eliminate single point failures which compromise vehicle recovery consistent with design constraints.
The safe and reliable procedures should be the natural, and obvious ones. Deviation from safe and reliable procedure should require work one the part of the idiots.
The critical system state should be as plain as possible. (mode LED, beeper?)--low level
Capacitive discharge energy storage must be well below the lethal energy threshold. This is typically 10J, but one reference: http://members.misty.com/don/xesafe.html suggests 1/8J as the upper limit for a safe system. For the pyro node limit energy storage to under 100mJ.
Accelerometer at least as good as the best noise figure on the sensor comparison table that is also capable of (20,25,)gee uni-axial unsaturated performance consistent with pyro node power requirements.
Safety factor approaching million-to-one for events with the potential for serious injury.
Comparable reliability factor for pyro actuation. Net reliability 10000:1 ok.
No mechanical switches in primary ignition path
Rechargeable no-fuss battery
Shorting method for pyro circuit during system assembly & handling
Redundant pyrotechnic circuits
Automated safety check / safe mode
Automatic self check for pre-launch functions
- Detect igniter open/short
- Detect HV present, capacitor charged
- Battery status check
- Switch operation
Independent timer on board
Independent launch and apogee detect systems
Independent power supply for pyro systems
Pressure sensor requirements
- NOT the same requirements as the inertial navigation suite pressure sensor.
- MUST have pressure range of 0 - 1 ATM (0 kPa - ~115 kPa, 0 - ~15 PSI) or more
- Absolute pressure (needs onboard reference)
- SHOULD use (,3.3,5) V power supply
- SHOULD use (,10,50) mA current
- SHOULD have single ended analog output OR digital output
- MAY have quick response time < 1 ms (~ KHz of bandwidth)
- MUST have a small package size (0,1,10) cm^3