Setting Raven for landing detection

[AlphaHybrids]

Is there a way to set the Raven for landing detection? I want to cut the parachutes so my rockets don't get prairie rash

Edward

[Adrian A]

Yes. The manual talks about this too, but the basic idea is to trigger on the combination of a low altitude that is below your main chute opening altitude, plus acceleration above a threshold (if your av-bay hangs from the chute right-side up). You can add a delay between the detection and the deployment, also.

[AlphaHybrids]

So the best way would be less than a certain altitude plus a time. So, say when it passes through 300' and then add a 30 second delay so that you know you should be on the ground.

[Adrian A]

That way would work, but it wouldn't eliminate the initial dragging. Using the low altitude plus a G trigger would disconnect the chute right at touchdown. If it takes a couple of seconds for the av-bay to land because of the length of the recovery harness, then put a couple of seconds of post-detection delay. If the highest area it might land is 300 feet above the pad, and the main is set for 1000 feet, I would set it to trigger on altitude < 400 feet, acceleration > 4 Gs, delay of 2 seconds.

Take a look at some example data. The landing acceleration signal is almost always nice and clear, and well over 10 Gs. The attached file has a typical dual-deploy landing signature, but is by no means cherry-picked. Sometimes the fin can touchdown causes enough unloading of the chute to trigger a 4 G threshold, but when the av-bay itself lands, it pretty much always does.

[AlphaHybrids]

I calculated the descent rate after the main chute and it was coming in at ~32 feet/second. That is quite high. Would a landing in the 10 feet/second produce the same impact?

[Adrian A]

I calculated the descent rate after the main chute and it was coming in at ~32 feet/second. That is quite high. Would a landing in the 10 feet/second produce the same impact?

It would be around 1/3 the magnitude. I'm not sure if I have data handy for an example flight with a descent rate quite that low.

[bobkrech]

Edward

You could also change your chute to one that collapses on landing.

Bob

[AlphaHybrids]

I use a highly modified toroidal parachute because it offers me the best drag for the diameter. The problem is that they do like to inflate again when on the ground. I'd rather be able to cut either the center line on my parachutes (which reduces drag by about 1/3) or cut have the lines free and that disables the parachute altogether.

Edward