Sunday, February 21, 2010

Dual Deployment

So I've been doing some more designing lately on the Sudden Mach, which is my 29mm Machbuster design, which I have designed to drag race the Wildman Blackhawk*. I don't have a final design yet, but after running a few basic simulations I have come to the unremarkable and inescapable conclusion that it's going to go very high.

On the order of 800 feet on a D, 1800 on an E, 2300 on an F, 3500 on a G, up to 4500 on an H motor, and as high as 6500 feet on an I motor. 6500 feet is one and a quarter miles. 2 kilometers. If I launched it from sea level, it would top out at roughly the same elevation as Mount Washington. Only about 2200 times faster than me climbing it.

At those altitudes, it'll be next to impossible to recover it. Even with a 3:1 ratio of drift to fall, as would be for a 12" parachute, it'll end up nearly half a mile away, more if it's windy. An 18" chute, better to avoid damage, would make the chance of getting my casing back very low.

So, I've decided to go the dual-deploy route. It's tricky, because you have to coordinate multiple reocvery devices, but it'll be worth it. The way it works is that you separate the rocket into two parts - the nose section which contains the primary parachute, and the fin can (with motor) that contains a streamer or smaller chute. In between, usually inside a coupler, goes an avionics bay (av-bay) with a dual-deployment altimeter.

You program it to deploy the streamer at apogee, and the main chute at a lower altitude; it does so by firing blackpowder charges. From apogee to the lower alittude (500-1000 ft), it falls quickly but controlled. After the main deploys, it falls slowly, but with less total drift than main deployment at high altitude. The system lets you land more easily in smaller fields, with less drift.


DTH Rocket said...

The problem with that is if it goes out of sight (which it easily could do) you've lost a pretty penny on those electronics. My mach-rocket a couple summers ago went clear out of sight and was never seen again, thankfully I didn't put any expensive payloads in it.

The EGE said...

Well, that's the whole point of dual-deploy. Even though it goes out of sight, the rocket will land pretty close to the pad. Which not only saves the electronics, but the expensive motor case as well.

Plus, I'll be launching this at NERRF, which has dozens of people watching the rockets and roaming around. Someone is either going to spot it in the sky, or find it on the ground.

DTH Rocket said...

I guess you're right, but I'm still too afraid to put electronics in rockets like that.