Defy Gravity Tether...

[pr_rocket04]

Can someone explain the concept behind Defy's Tether release? I realize it can achieve dual deployment with a single compartment, but I am unsure exactly how this is possible. I guess my concern is possible entanglement risks that may be increased.

 

[Hospital_Rocket]

One way I have heard it used is to deploy the main in a reefed condition and have th tether go off at the mains altitude and unreef the main.

A

 

[hokkyokusei]

Another configuaration is where a regular ejection charge deploys the drogue, which is rigged to pull out the main from a deployment bag. The drogue is also attached to the Tether ( ARRD, PRM, etc) so that the main is not deployed until the tether is fired. The deployment bag prevents the drogue and main from tangling in the bay.

 

[aksarben10]

The basic way that it works is that your drouge is popped be an ejection charge at apogee and the main is restrained by the tether. How it is restrained can take serveral forms, but at the right hight the alt pops the tether and the drouge pulls out the main.

Defy has a nice PDF on the site listing a number of ways to use the device.

https://www.macson.com/_pass5/dg/tm_large.pdf

Yes, you could get a tangle but if you design the system around the tether it works great. We have a fellow in our club who has used it with great success.


Scott

 

[pr_rocket04]

I just couldn't picture it at first. Totally clear now.

I would like to seperate the rocket into 3 sections on it's way down. I believe I will have the drouge pull the bag off of a medium chute at around 1000ft, while it and the nose separate. Very shortly after that the motor section will separate from the electronics and be slowed by two larger chutes. I believe I will separate the two main sections at main deploy so there is no chance of chute entanglement. I may use another gps unit in the motor section just for added recovery safety due to their seperation (wouldn't want to lose four 54mm's and a 75mm). Although I don't know if it is logical yet because of the size of the chutes and I'm sure I will probably see them if all goes well. Wish these things were a little cheaper.

 

[aksarben10]

Yeah, I know I would like to buy one as well. Funny thing is that the Tether is the cheaper one. The only other one I know of on the market is the BlackSky ARRD.

The ARRDs benifits are that it is a second or third generation device, there was a PRM I and PRM II before the ARRD, so you would think that they bugs were worked out, however I have heard that it breaks after a really heavy load and is not reliable after that. I think that I heard that as a post mortum after one of the Gates Brothers rockets crashed. ALso it cost $150 another down side.

Scott

 

[pr_rocket04]

It seems like such a simple device you wouldn't have any problems. I guess that's just how things typically go. Anyways the only forces acting on the Tether will be the drag from the drogue which shouldn't be too much.

 

[KermieD]

If you're separating into 3 sections, why would you need a tether? Just curious.

 

[pr_rocket04]

I have two available compartments for chutes. What I wanted to do was have a drogue deploy at apogee, then release the tether at 1000ft to pull a bag off the chute already out. Then Co2 pops the other section out which pulls two more chute bags off for the final mains. I have thought about various techniques without total separation of the components, and my conclusion is that this is the safest way to deploy the chutes. If anyone has any other suggestions I would be glad to hear them.