throughout the flight. Other events, like time > user timer value, can have no more than
one transition during the flight.
The “time delay” option will delay the start of the output by the specified time delay after
all other conditions are met. Note that once the deployment conditions are met, the
deployment will happen after the time delay regardless of any changes in the deployment
conditions after the delay timer has started.
Each output will be activated for 1 second, unless the “Hold the switch closed
continuously” option is selected for that output. The continuous output option is
designed to turn on a non-deployment load, like a transmitter. This option is not
recommended for use with deployment charges because charges can have residual shorts
that could drain the pyro battery for future use and/or damage the FET switch.
Deployment triggers details and examples:
Pressure Increasing (used for the default apogee, main, and main backup deployment
channels):
This condition is true whenever the filtered baro pressure measurements are increasing.
Since pressure decreases with altitude, this trigger corresponds to when the rocket is
falling. This trigger is used for the default main deployment channel so that the ascent is
ignored for the main chute deployment. Transitions to and from supersonic flight can
cause this condition to become true temporarily during ascent. That’s why the main
deployment channel looks for an additional condition, the velocity check.
Velocity < 0 feet/second (used for the backup apogee deployment channel)
This trigger is true when the upward velocity has stopped and the rocket is starting to fall.
The Raven senses the acceleration and subtracts off what it was reading when it was
sitting on the pad (about 1 G). Then it adds up the accelerations continuously throughout
the flight to calculate the velocity. This method provides an apogee detection that is
immune to pressure anomalies, but off-vertical flights or mis-aligned altimeter can affect
the apogee detection accuracy.
Height above pad < AGL1: (used for the default main deployment channel)
This condition is true when the measured altitude above the pad is below the AGL1
setting. AGL1 can be set between 0 and 32736 feet, in increments of 32 feet. For the rest
of the main deployment settings, other conditions need to be checked, since this condition
will be true from liftoff until the rocket gets above the main deployment altitude.
Velocity < Vel1: (used for the default main deployment channel and backup channels):
This condition is true when the accelerometer-based estimate of upward velocity is lower
than Vel1. This trigger is useful in combination with the pressure increasing trigger, to
ensure that the rocket is out of the transonic region before using the pressure increasing
check. The velocity check is also a useful trigger for 2
nd
stage ignition. Optimal altitude
can be achieved by allowing the rocket to slow down before 2
nd
stage ignition, while
maintaining enough speed so that the flight path stays nearly vertical. This trigger can be
used to ignite a 2
nd
stage at the desired velocity, even in the event of unexpected drag or
motor performance.
