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, November 27, 2007
We have been working on Polaron IV and its launcher in the background while doing the foam experiments. We have further refined plans now on how the boosters will be attached and how they will separate. The photo above shows three newly machined 13mm aluminium nozzles for the boosters.
Each booster is 90mm wide, 2.3L capacity weighs ~150grams dry including recovery system, has a 13mm nozzle and uses a 450mm launch tube.
The simulator predicts that individually each booster should reach about 130m (430') @ 120psi, however, each of the boosters is intended to lift an additional 900 gram weight. This additional weight being a third of the total weight of the main stage fully loaded with water. Under these conditions the predicted altitude of each booster is around 35m (120'). Giving the main stage a release velocity of ~ 25 m/s.
The calculation gets a little trickier because the main stage also fires at the same time when boosters are launched. Though the main stage only uses a 7mm nozzle and foam so that the overall thrust from the main stage will be much smaller compared to the boosters. The consequence of this additional thrust from the main stage means that each booster has less to lift and therefore will be released at a higher altitude and higher velocity. We will do these additional
calculations when we finish building the main stage and know its parameters in detail.
At 120psi, each booster will produce around 90N of thrust at release and about 190N at the end of the launch tube. That is a combined booster thrust of around 570N as the rocket clears the launch pad. Compare that to the Main stage that will produce around 55N thrust with water only and likely around 35N with foam. From static experiments we found that the main stage should thrust for about 6-7 seconds. Rough estimates for main stage altitude are around 230m (750') at the 120psi level. Actual flight though may vary from this figure if the rocket does not go vertically.
The launcher under construction will have two separate air supply lines allowing us to use different pressures in the boosters compared to the main stage. This should allow us to experiment with a wider variety of rocket configurations. Full plans will be published once the design is finalised and the rocket is tested.
Posted by George Katz at 9:42 PM