Dual Deploy Nose Cone – Part 1

The last week we have been busy building a PPNC nosecone that will deploy 2 parachutes using tomy timers. The idea is to have a smaller drogue chute deploy at apogee and the main chute when its closer to the ground.

Drogue Chutes
We have used some simulators to try to work out how big to make the drogue chute, but ended up with mixed results. So we decided to make 2 drogue chutes and see how they test. These were 10cm in diameter and 15cm in diameter respectively. We used the same procedure as we did when making the main chute except reduced the number of chute lines to 4 and 6.

Drogue Chutes

Drogue Chutes

On initial testing, the 10cm chute is just too small and doesn’t get enough air into it . The 15cm chute might be ok, but the hole in the middle is too big. We can just sew a patch over it and give it a further test. Worse case a 20cm one may be called for.

Longer PPNC Nosecone
The two chutes and release systems wont quite fit in a standard 1.25L body section we make the PPNC nosecones out of, so we have made a super sized PPNC (SSPPNC) by adding an additional 1.25L body section.

Super Sized PPNC Nosecone

Super Sized PPNC Nosecone

The bottom section was from a different 1.25L bottle manufacturer and is just used for the mockup, we will use a P&N bottle for the final nosecone.

There join is not perfect and the nosecone structure gets stuck a little. We will need to be more careful when fitting the final bottom bottle as we need to be able to get the nosecone structure in and out for servicing.

Nosecone Structure
The nosecone structure needs to have 2 elastic band powered pressure plates to push out the chutes. To accommodate this we have built another smaller structure as well as a section to join the two chute deployment sections. We needed this to have enough space between the two so they was less chance of lines being caught up.

Here is the drogue deployment structure (pressure plate not fitted yet)

Drogue chute deployment structure

Drogue chute deployment structure

You can see we use wire to join the sections together, this makes it very strong which allows for tighter elastic bands which help throw the chute away from the rocket body better, as well as having a better chance of survival during a crash.

Here is the structure how it will fit inside the super sized PPNC.

PPNC Dual Deploy Structure

PPNC Dual Deploy Structure

From the top down the pieces are

  • Pilot capsule – its main use is to ensure the main parachute deployment structure is below the curved section of the top of the nosecone. This helps the door close better if its flush against the side.
  • Main Parachute deployment section and pressure plate
  • Extension section – This is to position the drogue chute deployment structure down below the join of the two bottles in the nosecone. Having the door across the join is not a good idea
  • Drogue Chute deployment section (note the pressure plate is not fitted yet)

The two doors will be on opposite sides of the SSPPNC. The idea for putting the drogue lower than the main chute is so that when the drogue deploys it will be connected to a lower part of the rocket nearer the CP than the CG, the rocket will orient itself with the nosecone down position and drogue trailing behind. This gives a lot of room for the main to deploy and open being furthest away from the deployed drogue. The main chute will be connected close to the CG so that the main and drogue dont tangle .. well thats the theory anyway :)

Tomy Timers
We received our order of 5 tomy timers yesterday which is good. We also managed to destroy the one we had when glueing it to the structure, too much glue and we managed to glue up the gears … Lucky we ordered a couple of extras

The work for the rest of the week will be assembling the nosecone, testing the dual timer and getting some calibration numbers on the timers.

We will report part 2 later in the week

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This entry was posted on Wednesday, October 1st, 2008 at 1:16 am 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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