Pyrotechnic ("Pyro") node requirements
For the pyrotechnic node (PYRO) and the avionics power system (APS).
Useful local links:
- 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