Raven programming for backup chute?

I am getting ready to fly the first test flight of the mechanics of my active reefing system, using remote control. For the ejection I will be using a Raven altimeter which will fire the primary reefed chute at apogee. I will then attempt to unreef the chute. In case this fails I have a backup chute in the rocket that I want to program to fire if the downward velocity is faster than 20fps. Since the ravens velocity variable is in the upward direction I think this means that I want to program the backup to fire if the velocity is less than -20 so Velocity < Vel1 where Vel1 = -20. Is this correct?

Ravenex said:

I am getting ready to fly the first test flight of the mechanics of my active reefing system, using remote control. For the ejection I will be using a Raven altimeter which will fire the primary reefed chute at apogee. I will then attempt to unreef the chute. In case this fails I have a backup chute in the rocket that I want to program to fire if the downward velocity is faster than 20fps. Since the ravens velocity variable is in the upward direction I think this means that I want to program the backup to fire if the velocity is less than -20 so Velocity < Vel1 where Vel1 = -20. Is this correct?

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I don't believe this will work. The Raven calculates the upward velocity based on the acceleration readings. The acceleration readings coming down are meaningless for calculating velocity.

You might be able to use a different approach though. I don't know exactly what you're trying to accomplish for a flight profile, so you might need to modify this approach, but in theory, you could select an altitude during the descent and then calculate the time it will take to get there. So, if you're falling too fast, you get to that altitude sooner. So, you could program the Raven for Altitude < x, Time < y, descending, and it might provide the backup that you want.

Edit, just to beat this to death, it's essentially using the normal main deployment approach but with a time criteria added.

Jim

Problem with that approach is that if your flight is lower than expected it may trip the backup. You will need to carefully choose an altitude and time that are outside of the normal performance range with some margin, but not too late as to allow the rocket to pick up too much speed before the backup can be deployed.

My other option is to fire the backup remotely, but I don't like that to much.