I’ve been doing a little bit of model rocketry with the kids and started to think about 3d printing my own custom rockets. They seemed cheap and easy to make so I figured we could even fire them out of over the woods and not even bother worrying about parachuting them down because they would just get stuck in the trees anyhow. As a matter of whimsy I started to consider if I could design some sort of integral / alternative parachute approach and had a funny vision. What if it popped out helicopter blades at apogee and just whirly-birded back to earth like a maple tree seed!
I kicked that around a bit and then considered, what if the body of the rocket itself somehow “unfolded” to become the blades! And eschewing spring loading them in to pop out, I could have the rocket spin and open them under centrifugal force, but how to trigger them? After some more complex approaches, I considered a simple one, the ejection charge that is intended to push out a parachute at the end of a rocket burn could be repurposed to eject a container that otherwise retained the blades.
A rocket motor burns our the back for several seconds, pauses for some amount of time, and then puffs out a charge from the front to push out the nose cone and parachute. There is often a long delay between the rocket finishing and the parachute firing, this is to allow the rocket to get closer to the ground before the parachute comes out which make it easier to recover; if it goes off too early then it can be carried in the wind a very far distance.
Here is a design of the rocket. As you can see the body is comprised of folded blades that are hinged at the base of the nose cone. What you will see better in the second picture is how there is a canister within that hold the rocked motor and slides over a lip of the blade at the base.
Here you can see the canister (and the cap that screws onto it to hold the rocket motor in place) slid out from the base of the rocket and two blades opened out. The canister is suspended by a rod (not pictured) that extends up through the nose cone and attached under the nose code cap at the top:
Here you can see the blades fully extended:
Here are some pictures of it in real life:
Here is a sloppy one-handed attempt to try and show how the canister will eject when the parachute charge fires and release the blades:
And so does it work?!
Well, no… as you can see it buried in the neighbor’s yard (yikes!). BUT, this was with a rocket motor that had a considerable delay to fire the parachute. In that time the rocket turned and started coming down at which point the helicopter can’t function; it MUST deploy while still facing up!
When I retest with rocket motors that have NO delay, I will post back what happened!
