Early second stage release



two stage rocket ready for water fill and pressurization

September 5 2004.
A beautiful and warm sunday morning. This was going to be the second test flight of the two stage rocket.
Installed the rocket on the launcher and filled it with around 2 L of water. The PVC pipe on the left is to give a little extra support and to keep the rocket straight up. Camera almost flat on the ground looking up in the sky and started to pump. Around 70 psi or 5 bar the second stage first tilted a little then released its self. Hey!, that wasn't supposed to happen, what went wrong?. Don't know yet.
Have to find out, .....was the friction between the garden hose and second stage to low?, or maybe was the second stage pulling on the hose, causing it to stretch and thus decreasing the pressure on the walls off the second stage exhaust?. Well guess I have to do some calculations and tests at home.
. But surely I will be back with the results, just hang on.







Bottom view, 5 bar launch of the 9L rocket


It was far to nice and early to go home so I decided to put the chute container on the 9L again and make a video with the same camera position, on the ground pointing up.
Launched with a modest 5 bar. Play the movie at low speed, notice the first part of the water jet is more like a pillar of water, indicating laminar flow. Then a bit further on the track you see a cloud of water, indicating turbulent flow, during the end of the water thrust phase. When almost all the water is expelled the remaining pressurized air breaks through the water layer. The result is the cloud of droplets, when water and air are forced out together.
On its way back to earth, the chute opens just in time to prevent a crash.