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.

Tuesday, March 27, 2007

Tips for producing water rocket videos

We have updated our site with some useful tips in helping to produce videos relating to water rockets. The update can be found here:


Sunday, March 25, 2007

Acceleron II Details

We have updated our main site with detail photos and diagrams of the Acceleron II cluster booster.

The booster is now finished awaiting launch when the weather improves.


Friday, March 23, 2007

Acceleron II Development

We continue to further develop our Acceleron II booster. We have now added another 6 L of capacity, which makes it almost 19L in total. The nozzles are now 10 mm which is almost 30% more nozzle area.

The top bottle is still the same dummy payload that carries about 600mL of water for ballast that represents the weight of the second stage. That means as it stands the booster lofts about a 750gm sustainer (including water).

The dry weight is now ~1.3 Kg (including the empty dummy payload) which is a bit on the heavy side, but simulations predict an altitude beyond 100m. The booster will, however, only need to travel around 12m before it releases the sustainer at roughly 50m/s = 180 km/h = 112 mph. The simulation is based on 120psi which is what we currently use on this booster. 15-20 more psi is easily achieved, and gain us a few more m/s.

Simulations also show that this Booster / Sustainer combination should be able to achieve altitudes beyond 200 meters (650 feet) with the 120psi - 130psi range.

In this photo the booster still does not have the parachutes fitted. We hope to have it finished this weekend and take it on a test flight weather allowing. Full details of the rocket will be posted on the website once we had a chance to fly it.

Wednesday, March 21, 2007

Continuing Development

This week we have continued development and design work for the thrust measurement rig, and have manufactured a number of parts for it. We have also bought an analog kitchen scale that will be used to measure the thrust.

More research has been done into nozzle design, and we now have a plan for what designs we will test.

More work has also been done on Acceleron II including bottle reinforcement. More details will be posted in the next web update. There were no launches this week due to other commitments.

Tuesday, March 13, 2007

Jet Foaming Test Flights

This weekend we had a chance to fly a couple of rockets using the Jet Foaming technique.

The results of those flights including video and photos are here:

We definitely need to do more testing on the foam, as it seems to be giving the rocket a bit more performance, but we won't know for sure until we can build a thrust measuring device and performs some static fire tests again.

Feedback and suggestions are always welcome.

Monday, March 12, 2007

Foam generation tests and Baffle tests

We have updated our website with the latest static fire tests showing in detail how the water behaves inside a water rocket when a baffle is fitted to the lowest Robinson coupling.

The update also shows the Jet Foaming technique we developed to generate foam inside the rocket to provide a different thrust profile to the normal water/air mix.

We intend to develop CD nozzles to help improve the rocket efficiency.

The update is here:

We have now test flown the rocket with very good results. The video and update will be posted on the website soon.

Wednesday, March 07, 2007

Updated Day 25 Flight Log

Today we updated flight log 25 with a couple of pictures from our under water tests from 2 meters. There is also underwater video showing what happens to the rocket under water.

Otherwise construction of the two new flight computers is continuing, and Polaron III is ready to be tested with the new coupling baffle. Just need to get some nice weather now.

Sunday, March 04, 2007

Coupling baffle and Burst Test

Yesterday a new aluminium coupling nut was made that incorporates a baffle to direct the air sideways onto the walls of the bottle. This should help eliminate the blow-through seen in the static fire tests. This will be tested this week to see what effect it has on performance. The holes are 6mm in diameter, with a total of 4.

We also performed some pressure tests on a reinforced bottle based on the reinforcing technique described by Richard Wayman here:

We didn't quite get up to the burst pressure of the 1.25L bottle, because we had an issue with the hose failing to hold onto the rocket. We went up to 220psi, before it flew off the test stand. We are making a new attachment that will prevent the bottle from flying off. But all the signs were encouraging for a significant improvement in strength.

We ended up using hot water instead of the heat gun to shrink the outer bottle which worked quite well and pretty evenly.

We also finally have a new proper domain name:


Friday, March 02, 2007

Progress update

Last night, I continued soldering up the new flight computers (FC) for Acceleron and J4 II. It's still will be a couple of days before they are both finished and tested. A preliminary weigh-in of the entire FC including battery and motor & gearbox was 37 grams. This may increase slightly.

We are trying to beat the version 1.2 weight. On Polaron III the entire parachute deployment system including nosecone, but not parachute weighs 133 grams. With V 1.3 we are hoping for under 100 grams.