Dual Deploy Nose Cone – Part 2

After building the SSPPNC and thinking about the servicing problems I was facing, I came to the realization that this SSPPNC didnt really fit with our philosophy of a modular approach to water rocket construction. Rather than building a SSPPNC that could deploy both chutes we decided to leave the PPNC as it was and build a drogue chute module. The idea being that this module could be added or removed from the rocket based on the requirement of the launch.

Bottle Shrinking
One problem we have found when fitting and aligning the parts of the rocket was the fact that the diameter of the PPNC is smaller than the bottom section of the PET bottle, not by much but enough to have it not fit on straight and sometimes having to be realigned after taping.

We decided to use George’s method (http://www.aircommand.com) of shrinking the bottom of the bottle. This ensured the PPNC slides over the bottom of the bottle underneath it in the rocket. See Georges video about the 4:00 minute mark for how to shrink a bottle. We didnt quite have the water boiling but Im guessing around 80 degrees C. We immersed the bottom of the bottle a few times until we had it the size we wanted.

Here is a pic of 2 x 1.25L bottles. The bottle on the left is a standard bottle, the bottle on the right has had the bottom shrunk slightly.

Shrunken bottom of 1.25L bottle (right)

Shrunken bottom of 1.25L bottle (right)

Although they look very similar there is a big difference when connecting the modules together. This is best shown with a video. So here one is. In this video I am connecting the new drogue parachute module to one of the rockets pressure bottles. First connecting to one I have shrunk, then to an untouched bottle. You can see the difference.

Drogue Parachute Module
In part one of this article we showed the nosecone structure for the drogue deployment module. As we have now decided to make a drogue module that can be added or removed from a rocket, we needed an enclosure that would allow this. The obvious choice was to use the bottom section of a shrunken bottle.  This will allow the PPNC module to fit over the top of it, it also allows this module to fit over another module (a future payload module) or the bottom of the pressure bottles.

Drogue Chute Module

Drogue Chute Module

We have used bubble wrap as fill in the top section (its lighter than sponge), the size of the structure and door opening is smaller, to take smaller chutes, but the tomy timer configuration and air flap is the same as the PPNC module

Putting The Modules Together

The modular method we have used to shrink the bottom section of the bottles allows the modules to be easily put together to form the rocket combination we desire. Here is a video of the PPNC module, drogue module and out pressure bottle being assembled. For liftoff they are taped together. This method makes module alignment much easier.

I have weighed the modules and shown it here for those interested. You can always get to this from the Menu section of the site then under categories then weights.

Dual Deployment
Here is a test run of both chutes deploying, the modules are connected to H2. We will do a bit more testing prior to launching this configuration, however so far so good. The air flaps detect launch and will sit closer to the rocket body during acceleration

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This entry was posted on Tuesday, October 7th, 2008 at 11:06 pm and is filed under Development. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.


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