This blog covers the day to day progress of water rocket development by the Air Command Water Rockets team. It is also a facility for people to provide feedback and ask questions.

Monday, June 01, 2009

Rings, fins and other things

We had quite a busy weekend working on the rocket. The following has been completed:
  • The ring brace is now fiberglassed, sanded and painted
  • The wiring connections to the servos and pressure switches are complete
  • The parachute deployment mechanisms are complete
  • The fins are complete
  • The sustainer is finished
  • The flight computers have been attached
Still left to do:
  • Painting
  • More pressure testing of various components and bottle assemblies.
  • Simulations
  • Attaching various things like parachutes and the ring brace to the bottles.
  • Mounting a camera and altimeter in the booster
  • Bunch of little fiddly things
  • Full integration testing of the entire system at 20 psi
  • Launch abort loop and hook
One of the main problems we've had is improving the yield of the splices at the 130psi range. Dad pressure tested the 9 spliced pairs to 130psi for 2 minutes during the week. Out of the 9, five were good. Two had very minor leaks of a few drops and a couple had more significant leaks. Dad had a go at sealing them from the inside with silicone and we are waiting to re-test them on Wednesday. We have about 7 spliced pairs currently that we need to test and get 4 good ones out of those. Otherwise there are still 2 good ones we have in the Polaron rocket should we need them.

There are still minor things to finish during the week, but most of the long lead time things are done.
The new ring brace can be seen in the image below (red with white stripes). The red Velcro strips around the bottles and lower section are only temporary at this stage to hold the rocket together as we work on it. It makes it easy to remove bits as needed and put them back.

In the photo below the rocket is still unpainted, but you can see the flight computer compartment on the right, and one of the parachutes on the left.


The new sustainer is a little shorter (about 6 inches) than the photo posted earlier in the month because we decided to put a Robinson coupling in the lowest bottle to generate foam in flight for a longer and more visible burn.

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5 comments:

TDF water rockets said...

Hi George
Are you going to paint the bottles?

George Katz said...

Hi Tom,

We are only going to paint sections of them. The splices are pretty ugly so we paint them white (like that seen on the sustainer in the photos). We like to be able to see into the bottles to see what is going on. We now only use very light colours as the sun can heat up dark colours and distort the bottles.

Mat_G said...

Looking good George.

Can't wait to see it fly :o)

Daniel Veira said...

Hi George

Is good see that you are making progres on the Aceleron V, thanks for answer my cuestion too.

I got a cuestion about the gravity center. How can I do for know that the gravity center is in the right place?

The upper stage from the Aceleron rocket will leave fins?

Thanks a lot for your patient.

Good luck with your rocket!!

Daniel

George Katz said...

Hi Daniel,

To find your center of gravity tie string around the body of your rocket and then hang the rocket by the string. Move the string up and down the body until the rocket is balanced (horizontal). That is the center of gravity.

To find the center of pressure is a little more tricky. Here is a good reference:

http://www.grc.nasa.gov/WWW/K-12/rocket/rktcp.html

You need to make sure that the center of gravity is ahead by about 1.5 body diameters of the center of pressure. If it is more that's okay, if less then the rocket becomes marginally stable.

The second stage on the Acceleron V rocket does have normal fins. There is clearance along the length of the boosters for them. (That's why there is a ring at the top. )

Cheers

- George