Black powderless dual deployment.

[Aksrockets]

This idea came to while lying in bed a few moments ago. I was thinking about how great it would be if I could use dual deployment (im under 18 so i cant handle black powder, making conventional DD impossible). While there are products like the tender desender on the market, i want to create my own BP-less dual deployment systems.
Here is the basic idea:
Motor ejection will occur at apogee.
The main chute will come out but will "squibb".
The Squibbing will occur because one or more of the parachutes shroud lines will be held down by a seperate nylon cord attached to a seperate eyebolt.
The rocket will decend quickly to the altimeter's programmed altitude.
At altitude (lets say 500') an igniter and sliver of blue thunder propellant will ignite.
The igniter and propellant package are secured to the nylon cord by a soda straw.
The propellant burns through the wire, releasing the nylon cord and the parachute fully opens, resulting in a gentle landing.
If this isnt very clear, i'll upload pics of the sketch i drew tomorrow AM.
The tricky thing will be to get the nylon cord strong enough to hold the shroud lines down, yet weak enough to be cut easily by the igniter and propellant mix.
This will require a lot of testing but the reward of dual deployment to me is to great to pass up.

Thoughts? Is this worth a shot?

Alex

[WillMarchant]

Look at the Defy Gravity "tether" manual (http://www.defyg.com/tether.html) at the "burrito" and instead of a tether use a piece of nylon fishing line to keep the parachute closed and cut it for main deployment with a Quest Q2G2 igniter inside a piece of brass tubing. Basically you'd be home brewing a http://www.chutetamer.com/introduction.shtml

[cwbullet]

The Chute Tamer works. I have used it once.

[CarVac]

You may want to look at chute reefing, which is puts less load on the line you would have to cut. The reefing line dies not need to directly resist the opening force of the canopy, and by holding the chute closed, it prevents the inversions I can imagine occurring with the system you have in mind.

However, it would probably need a custom made chute with loops around the base, and it seems like it would work better with larger parachutes.

[bjphoenix]

I've had the same idea- cut some monofilament line with an igniter and use springs to separate the parts and eject the laundry.

My current club's launch site limit is a G so this is all academic of course.

[grouch]

Why would a G limit relegate you to academics? You can get plenty of altitude on a G to test it out.