dual stage deployment

[rocketsonly]

Hey all. Has anyone heard of a method in which the drogue chute is connected to the main chute? Here's a diagram:

nose-------drogue---------------main-------------------body body body body

is this possible?
-Matthew

 

[Missileman]

Yes I have heard of doing this using a
Advanced Release and Retention Device (ARRD)
From Blacksky Rocketry
https://blacksky.safeshopper.com/14/53.htm?543
This holds the main in place until ready to deploy. After release the drouge pulls the main out.
I think this is what you meant?

 

[rocketsonly]

I wanted a drogue to deploy at apogee, then the main to deploy at approx 400 ft. I'm not sure if that device does that. But how does it work? $120 is quite a bit!
-Matthew

 

[Missileman]

The way it works is it holds a teather to your main and uses a BP charge to release the teather, It is fired via your altimeter.
I agree it is expensive, Too much for my taste.
I was considering this method in a design I worked on a while back.
I have not found another vendor that makes such a device.

 

[Ryan S.]

There are other Tether Methods, but I am not sure how well they work.

If I ever build a big V2 I think one of these will be needed. They are really used for short stubby rockets as it is cheaper for longer ones to just do it the normal way.

It would be cool if someone did like triple deployment with a tether and the regular style or something like that

 

[rocketsonly]

Okay, I understand it. But how reliable can a drag chute pull out a main chute? Do you know the pin style in which the device holds the pin, but still allows it to be blown out?
-Matthew

 

[Missileman]

I really don't know how exactly the device works.
I read about it in an old HPR mag.
I would imagine as long as your chute is not a tight fit in your BT the drouge should not have much trouble pulling the main out.
I would not trust deployment at 400 feet though.
I would not be comfortable under about 800 to 1,000 ft.
Using this method.
Here is another thought.

Nose....Drouge....Piston/w plastic rivots....main...body,body,body.

The piston with rivots holding it in place will keep your main in your BT until your main charge fires pushing the main and piston out.

 

[rocketsonly]

what does the piston look like? Do you know of any websites that goes in detail of them?
-Matthew

 

[loopy]

Another company that makes such a device is this one by defy gravity. Basically, your altimeter deploys the drogue, then fires the tether to deploy the main out of the same opening in the rocket as the drogue. You could also just go with a more standard dual deploy with the altimeter in a payload bay higher in the rocket, ejecting the drogue from the fin can area, and the main from the nose cone area.

Loopy

 

[loopy]

Public Missiles website will give information on the piston system.

 

[Missileman]

All the piston is, is a coupler with a bulkhead glued inside,
Put a couple eye bolts one facing in each direction to attach shock cords to.

 

[daveyfire]

Originally posted by rocketsonly
Do you know the pin style in which the device holds the pin, but still allows it to be blown out?

In the ARRD, there is a pin which goes in and has a machined groove around it. The pin is held in by ball-bearings in a small trap. When a Pyrodex or BP charge fires, it pushes a piston forwards, expanding the ball-bearings and releasing the pin. Kinda hard to describe online, you have to see it in person for it to make sense.

The Defy Gravity Tether is a great product too, and cheaper (visit https://www.defygravitynow.com for pics/etc). It's got a really simple release mechanism which is essentially a pin going through two "retention tabs". When a BP or Pyrodex charge fires in an axis perpendicular to the pin and tab setup, it releases. Simple and strong.

I own one of each unit. I use the ARRD for big projects (>7.5" diameter), and the Tether for smaller projects. I know the ARRD can take quite a force -- when GBR flew Porthos II (https://www.gbrocketry.com/porthos_ii.htm) on 6x N4800s, some of them lit late and sent the 400 lb beast off at an angle. At apogee, the rocket was still travelling around 100 mph sideways. The 20 ft ballistic drogue opened up and YANKED on the ARRD, pulling the rocket to a complete stop. It held.

Good enough for me!