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.

Wednesday, October 22, 2008

FTC Payload

I've been quite busy this last week with non-rocket related things but have continued the steady progress on the FTC payload section in my spare time.

All the components are now fitted inside the payload section, but more work is still needed to secure things a bit better for the expected G forces of around 70G. The entire payload section shown above currently weighs 118 grams and includes the complete deployment system with servo motor, parachute, flight computer, altimeter and batteries. The flight computer is V1.5 on a 25mm wide PCB to fit into the T-8 tube.

The complete deployment system is only made from items found around the house. The full details will be given in the next main website update along with a video of how it works.

We will be picking up some kevlar line for the parachute on Saturday which should make things a little lighter and stronger.

It's been fun trying to fit everything into such a small space. For deploying the same size parachute as we have been using on our smaller rockets the entire deployment system is about 25% lighter than our existing ones and has a lot less drag.


Tuesday, October 14, 2008

FTC rocket update

Over the past couple of days we have been putting a bit of effort into getting the FTC rocket ready for its first flight. I did a test to see if the fins can be glued directly to the reinforced FTC body, but PL premium does not hold well to the the glass strapping tape. They will have to be attached a different way.

The parachute ejection system is not complete yet, but is working quite well. We can use a fairly large parachute in it.

I've started soldering together V1.5 of the flight computer in a format that fits into a T8 tube. There will be one small RC servo motor for deployment. The payload section will also include one of the altimeters. Other than that, the pressure chamber is finished.

Pictures will be posted when more of it is assembled.

Thursday, October 09, 2008

Thrust Data Available

We have spent all week collating the data from the thrust tests. Our main website has now been updated with the results here:

There were some interesting results and we want to do further follow up experiments, as well as some new ones.

It's a bit of a long write up so feel free to skip the boring sections.

Saturday, October 04, 2008

17 Tests in 3.5 hours

Today was a good day for testing. We went through quite a bit of air out of the scuba tanks, but the tests went relatively quickly and we got through most of what we wanted to get done.

We are in the process of analyzing the results at the moment and putting together a video of the tests as well. It will take a few days to write up the results.

Some of the tests included:
  • Robinson coupling choking and blow through effect,
  • Jet foaming techinque with and without foam,
  • Reduced mixing chamber for jet foaming,
  • Some tests were done with a 9mm nozzle and some with a 7mm nozzle,
  • Foaming agent concentration difference
  • We tested 2L of carbonated drink in the rocket,
After we analyze these we will have a better idea about what things we want to redesign and test further. The next set of tests will include the variable nozzle with different holes and with and without foam.

FTC Rocket

We have also done some more work on our FTC rocket. We have the fins cut out now, but more importantly come up with the way we want to do parachute deployment in a T-8 FTC tube where there isn't a whole lot of room. The best part is that all the components are common items that can be found around the house.


Thursday, October 02, 2008


After importing a lot of thrust data from the test stand into Excel it quickly became obvious that the data still needed a lot of processing before it was useful. While it is easy to do in Excel, it is quite tedious, as the data has to be trimmed, aligned in time, averaged, calibration scaling applied, total impulse calculated and then graphed. This was taking perhaps 10 minutes per data set so I decided to extend the functionality of the WDQ to CSV exporter application I wrote a few weeks ago.

The application now can do all of the above tasks. With a few mouse clicks I can get total impulse, average thrust, thrust duration etc. This allows us to quickly review the data during testing and alter our tests based on the observed data. This should help in the design process as we make changes to the design we can get instant feedback on the design.

The full software functionality will be covered in the day68 update with the calibrated test results.

We are hoping to do a full set of tests this long weekend.