Just like X-box in 3D

Close shave

Missed by that much.

Interesting Foam Performance

One thing that stood out on the day were flights #4 and #6 and their significantly higher altitudes of 466' and 541' compared to the first 3 flights though the only difference was the addition of bubble bath into the water. All other parameters were the same. At first we thought that perhaps the AltimeterOne may have been giving the wrong readings or adding a bias each flight, but flight #5 showed a lower altitude of 310 feet which looked about right. For each flight we always zero the altimeter just before launch.

The flight time for flight #4 was 35.9s and for #6 it was 49.4s compared to an average of 25.5 seconds for the first three flights without foam further supporting the evidence for the higher altitudes. Lastly the video from onboard the camera also visibly showed that the rocket was higher on those two flights.

The only unconfirmed parameter that may have made a difference is the pressure in that we may have set the pressure regulator to a higher pressure on those two flights. The following day I measured the last pressure setting on the adjustable regulator and it read 130psi when filling a single bottle. The top bottle was also a little more deformed than normal, so it is possible that the last flight was at a higher pressure (hence the higher altitude than #4). Dad though believes the pressure was reading 120psi when he closed the valve, the extra volume of the rocket on the end of the long hose may have had something to do with the reading if air was still flowing into the rocket. We always wind the pressure back to 0 before filling the rocket, so it is very unlikely that both #4 and #6 were at 130psi.

Our current assumption is that flight #4 was at 120psi and flight #6 was at 130psi or close to it. For the next verification launches again comparing water and foam we will set the pressure regulator to one setting and leave it there for all flights to make sure we always have the same pressure.

Simulations

Running two different simulators for this rocket with parameters:

Capacity: 5.35L (measured)
Nozzle: 9mm
Weight: 544g (includes camera, altimeter, and parachute).
Diameter: 91mm
Water: 1500mL

@120psi gives us an approximate altitude of 354 feet (108m) for Clifford Heath's simulator and 365 feet (111m) for Dean Wheeler's simulator.

These are relatively close to the measured altitude on flight #3 (365') and are also in close agreement to flights from 2 weeks ago of 376' and 363'.

@130psi  we get an estimate of 396' (121m) for Clifford's simulator and 400' (122m) for Dean's.

Flights 4 and 6 significantly deviate from these predictions. They are roughly 20-25% higher!

The rocket's configuration is a spliced-pair on the bottom with a 18mm hole in the tornado tube to a second splice-pair in the middle. This then joins via another tornado tube with a 15mm hole to a 1.25L bottle at the top.

Other observations

• Just before launch #4 you can see that the foam level reaches up to the top coupling. For the #6 launch you can see that the foam level was half way up the top bottle. There had been some residual foam left in the rocket from the previous flights.

• The same rocket was used in Doonside two weeks earlier and launched at the same pressure with 1500mL of water only. It gave altitudes of 376' and 363' which is consistent with the first three flights without foam.

• When we filled the rocket, a lot of the water drained into the top bottle, when we set the rocket up on the pad we had to squeeze the bottle several times to get the water to drain to the lower levels. This likely produced more foam in the rocket.

• Quite a few years ago there was 1 flight we did (day45) that also showed a significant altitude boost over a previous flight when we added foam.

Sound analysis

Launch	Details
1	Rocket   Axion II Pressure   120psi Nozzle   9mm Water   1500mL Flight Computer   ST II - 5 seconds Payload   HD Cam #16, Altitude / Time   ' / 22.8 seconds Notes   Good flight with and good landing. No Roll. Very good video.
2	Rocket   Axion II Pressure   120psi Nozzle   9 mm Water   1500mL Flight Computer   ST II - 5 seconds Payload   HD Cam #16 Altitude / Time   ' / 29.3 seconds Notes   Good flight with very little roll. Good landing.
3	Rocket   Axion II Pressure   120psi Nozzle   9 mm Water   1500mL Flight Computer   ST II - 5 seconds Payload   HD Cam #16, AltimeterOne Altitude / Time   365' / 24.4 seconds Notes   Good flight with very little roll. Good landing.
4	Rocket   Axion II Pressure   120psi Nozzle   9 mm Water   1500mL + foam (no jet foaming spacer) Flight Computer   ST II - 5 seconds Payload   HD Cam #16, AltimeterOne Altitude / Time   466' / 35.9 seconds Notes   Good flight with very little roll. Good landing.
5	Rocket   Axion II Pressure   120psi Nozzle   9 mm Water   1500mL + foam, jet foaming spacer Flight Computer   ST II - 5 seconds Payload   HD Cam #16, AltimeterOne Altitude / Time   310' / 22.3 seconds Notes   Good flight with rocket arcing over. Good landing.
6	Rocket   Axion II Pressure   120psi (130psi?) Nozzle   9 mm Water   1500mL Flight Computer   ST II - 5 seconds Payload   HD Cam #16, AltimeterOne Altitude / Time   541' / 49.4 seconds Notes   Very good flight with very little roll. Excellent altitude. Good landing although it just missed the tree.