It's me again, first time using a deployment bag and I have some questions...

[3lapfancy]

Hello everyone. I am finishing up a rocket, 6" diameter and this is the first time I will be using a deployment bag. It will house the main 120" parachute. I have been planning on using the nose cone to pull the bag from the chute stuffed inside using the force of the ejection charge.

The tether that would be used to attach to a nose cone is only about 3-4" long, which would mean that my chute in the bag will literally be right next to the nose cone, so I am curious if this is OK and just stuff all the shock cord underneath? Or should I attach a small length of shock cord to the nose cone and D-bag to pull if off when the nose cone is ejected?

Need to figure out what method I should be using to pull the bag off the chute.

Thanks in advance,
Steve

[quickburst]

Most of the time a small drogue is used. Say 24" or so.

[3lapfancy]

Interesting. I thought I have seen them used without a small parachute. DOes anyone know if this is possible or not? Otherwise I will have to get a chute to use (I don't know that I have anything that small)

As far as the strength of the small chute, is that important? The rocket weighs near 40 LBS. Would a simple PML chute or similar work OK?

Is there any way to ground test the D-bag to make sure that a 24" chute will pull the main out?

Thanks guys!

[kandsrockets]

A 24" pilot chute will be plenty to get the bag off the chute.

[ScrapDaddy]

Interesting. I thought I have seen them used without a small parachute. DOes anyone know if this is possible or not? Otherwise I will have to get a chute to use (I don't know that I have anything that small)

IIRC, there are deployment bags that ARE their own pilot chute, I forgot who makes them, although I know they do exist.

SD

[3lapfancy]

Has anyone ever seen a D-bag used without a pilot chute? I swear I have seen this method before, but I certainly could be wrong.
Thanks for all the input guys.
Steve

[cjl]

A pilot chute is definitely the way to go. You could try to use one without a pilot chute, but it would have a much better chance of failure.

[troj]

Yes, I've seen folks use deployment bags without a pilot chute, but no, I would not recommend it.

Relying on the inertia of the nosecone is begging for trouble -- what happens if the charge doesn't burn fully, or something disperses too much of the energy, preventing the nosecone from extracting the bag?

Put the pilot chute in the rocket such that when the nose comes off, the pilot chute literally falls out, and you'll have a reliable system.

That's how we set things up on all of our big projects, and it works very well.

-Kevin

[3lapfancy]

Great. Thanks for all the input. Now, is there a way to ground test this? I really would like to make sure that the pilot chute I use will pull the bag off the main. I have been thinking that I could just throw the D-bag with pilot and a small weight attached off of roof or something, but with at least a thousand bucks sitting on the pad, I would like to make sure the main is going to come out.

Thanks again everyone.

[kandsrockets]

Here is a pictorial how I do mine. http://www.kandsrockets.com/dbag.htm

[Handeman]

I'm thinking a multi-story parking garage would work well for throwing things like that off. Easy access and safer then a roof top.

Might want to talk to the local security folks, or whoever is watching the cameras. Could save some trouble later.