At Maker Faire, Chris said auto-land is a hard problem. While I don't have much to contribute to that yet, I did want to try deploying a ballistic parachute mid-air to bring a plane down. A few others have shared successful parachute systems before.
So obviously the parachute shock cord just ripped straight out. The lesson is you can't use that simple paper shock cord mount design you glued into little model rockets as a kid to slow down a 3 pound Bixler mid-cruise.
I am kind of surprised that the ignitor circuit worked on the first try, and that the Sugru + masking tape tube mounting held!
I was also surprised at the pitch moment; I guess I could have computed it beforehand. I didn't think the rocket's moment arm against the vertical CG would cause it to flip forward that much. Also, the parachute was slightly burnt. I should switch to that "dog barf" fiber insulation instead of using recovery wadding.
Here's the pre-fail overview.
If I get around to finishing a lighter and more reliable parachute deploy, I might try using my MaxSonar to detect an approaching object (like the ground) and deploy it automatically.
Comments
Not to spoil the fun with rocket engines and maybe making a blasting cap of some sort. But, if you don't have to use the blasting part of it, wouldn't it be better to make something with a pin and spring of some sort? I am looking at the point of if something goes wrong and the blasting cap or the rocket engine happens to malfunction and ending in burning of the airplane and electronics. or it blasts and disables the plane from landing. To me it seems as if it is a risk.
Brian, you could use elastic rope to dampen the quick deceleration if the cute is deployed at speed.
From my experience dabbling with a parachute recovery system it's easy to arrest the flight too quickly and cause damage to the air frame. I had used a method similar to one listed above where a servo triggered released a rubber band holding my parachute. I used a longer band that was wrapped around the chute in such a way that it would flip the parachute out to the side to ensure it deployed correctly. It was anchored using several larger sized rubber bands to the boom of my SkyFly Max. It worked well to stop/drop the plane but did cause the eventual failure of the platform. The stress from the arrest caused the fuse to crack where the boom was attached into the body.
It was fun but my caution would be to not anchor it too rigidly. Use some thing that can absorb the shock of the chute deploying but not too tight to cause damage like mine did... Good luck and btw... foam and fire not a good combo...
I second the traditional method. Try using a spring loaded pilot chute. Much simpler than a ballistic system. I should know, I've got a few thousand skydives. The spring loaded pilot chute is used on sport parachute reserve systems and emergency pilot rigs and are extremely reliable (I've had 8 reserve rides and witnessed countless others). The idea is the spring inside the pilot chute is compressed and packed on top of the canopy and held in place by flaps, a loop and a pin connected to a rip cord. The pin is pulled (or the loop is cut) and the spring fires out, catches clean air and drags the canopy with it. Super simple :)
Definitely 1 of the funnier parachute failure videos. Any proper Rube Goldberg machine has a toaster somewhere, to go with the rocket engine.
Ok guys, just some additional comments. I believe there are existing model rocketry regulations that prohibit the mounting and firing of rockets in horizontal position. This prevents model rockets from being used as small missiles. Also I'm not sure that bringing up of explosives, like blasting caps into the air is allowed.
If you wanted to do the same setup you had before I'd say use a nylon parachute ($12) and a stronger, fire resistant shock cord. Also cover the bottom of the plane near the motor with a layer of aluminum foil.
I think the best solution would be to use a blast cap like at the bottom of this link: https://publicmissiles.com/secure/components.asp?groupid=26
and epoxy that to a wood bulkhead that you can epoxy to your rocket body tube. I drew a picture of the setup I have in mind. It uses estes parts and that blast cap. You would need a little black powder or equivalent as a charge. This is what they do in sport rocketry and the same thing used in the estes engines.
10-4. I think it would be simpler to do. Rather than a rocket engine. How I would make it would be with a cloth small bag. Then I would make like flaps and put something in the bottom for the spring to push on. so when it was all packed nice and neat into the little bag. Then you would have to make it so that a pin would hold the two flaps together. Then hit the button and pulls the pin and pushes the chute out.
Wouldn't such a system work for a plane, if the pin was operated by a servo or solenoid?
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