I've been thinking about a possible feature to add to a dual deployment
altimeter for some time. I'm wondering if it has ever been considered
(at least by you guys) or if there are some technical difficulties that
I'm not thinking of.
The problem that this feature would be attempting to solve is as
follows. In a dual deployment setup there is a possibility that the
apogee separation could fail. This could be due to the charge not
firing. Not a strong enough charge to cause the separation. Or maybe it
separates, but the drogue chute gets tangled up or fails in some way. If
this happens, the rocket is likely going to begin a ballistic
trajectory, or at least start descending at a higher than ideal rate.
Now the main ejection and separation may happen when it has been
configured to happen, but at this point the rocket is going to be going
so fast that you are probably going to have extensive damage. Despite
the damage, maybe things hang together well enough to slow the rocket
down to a relatively safe landing, or maybe not.
It would, therefore, be cool if the altimeter could in some way detect
the apogee failure and trigger the main ejection early. Obviously, this
defeats the intention of the dual deployment, but I would much rather
have to hike after the rocket than for it to be destroyed and/or come in
hot and unsafe.
The way I would envision this being implemented is for the user to
optionally be able to specify a maximum decent rate. After apogee the
altimeter would continuously calculate the decent rate, which I believe
it is doing anyway, and if that rate goes above the set threshold, the
main ejection is triggered, regardless of the current altitude. Setting
this parameter would require a bit of calculation and/or simulation by
the user to determine what the expected decent rate under drogue would
be and then you would want to leave some buffer. Some experimentation
would perhaps be necessary to provide some good guidelines.
Do any altimeters on the market do this kind of thing that anyone knows
about? I haven't seen it, but I haven't studied every one extensively
either. Do others think this would be a useful feature, or am I alone on
that? Are there some implementation issues that I'm not thinking about?
Anyway, I am offering this up for consideration and comment.
Steve
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Steven Saner <[email protected]> KD0IJP
Andover, Kansas USA
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Steven Saner <[email protected]> KD0IJP
Andover, Kansas USA
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