We arrived at the launch site around 8am as usual and started setting up. It was overcast and there was a bit of a breeze going, but at least it was blowing in the right direction. Although not ideal the conditions were within acceptable limits. We need to pay particular attention to wind conditions because this rocket is big and can catch the wind easily. Without a launch rail things could get interesting in a strong cross breeze. It took about an hour to set up the rocket for the first launch. It's always good to have a checklist for this procedure, as there are things that need to be done in specific order.

• We pressurised both the booster and sustainer to 120psi for the first flight which is slightly on the conservative side. The launcher release head was a bit sticky and John had to put his back into it to get it to finally launch. It's good to have the kids grow with the rockets.

• The rocket went up almost vertically and separation was nice and clean. The water flow was laminar from all three nozzles during the boost phase meaning the new narrow nozzle seals were doing their job. The air-pulse was also simultaneous indicating that pressure was pretty equal within the booster segments. The booster cruised for a little while before staging. Reviewing the video, it showed staging at 1.24 seconds after launch which means the pressure switch triggered the separation as designed when there was little to no thrust from the booster. The back up staging timer was set at 1.8 seconds from launch.

• After separation the booster continued it's upward track for a little longer and deployed it's primary parachute soon after apogee. The booster reached 168' (51m). The secondary/backup parachute was also ejected well above the ground but because the rocket was slowed by the primary parachute, it took a while before it too fully inflated.

• The booster landed well on its side, but suffered a little bit of damage on the balsa/fiberglass ring brace. 3 out of the 6 birch wood attachment tabs had broken. This wasn't a critical problem as the other tabs were enough to hold the brace in place for the next flight. We added extra gaffer tape over the brace to make sure it stayed attached to the booster segments.

• The sustainer powered its way upward although it had a little bit of spin on it. We noticed this spin in last weeks qualifying flights, but did not try to fix it. The spin is useful for overcoming any off-axis thrust from the nozzle or if the rocket is not axially balanced. Although the spin is not ideal for onboard video, I think in the end it helped to make sure the rocket continued upwards rather than in an arc.

• The rocket reached 787' (239m) which was a new personal record for us. We were hoping to get over the 200m mark with these flights.

• The parachute opened just after apogee which was good, as I didn't want it to open too early. It is hard to simulate a flight with foam accurately.

• The cross breeze ensured we had a nice walk of about 350m downrange to retrieve the sustainer. The booster luckily landed within several dozen meters of the launch pad.

• The onboard video turned out quite good, but when it's cloudy the colours are a little washed out, and the auto iris also tends to misbehave a little. The horizon was quite hazy, but it was the first time we were able to see the shore of Prospect reservoir quite clearly. The booster camera also had a good view of the take off and spray from the staging.

• This was also our longest flying water rocket at 60.5 seconds to date.

• Here is a timeline of events from flight #1:

Flight #1 Timeline

• Including the repairs, it took about 20 minutes to set the rocket up again. Although we waited about an hour between launches as we downloaded the altimeter and camera data first in case we lost the rocket and would be unable to recover the data from flight 1.

• Because of the white clouds, dad suggested we colour the foam a dark blue so that the trail could be seen against the clouds. I protested because of the mess it usually makes and for some reason the blue in particular tends to stain most things permanently. Although everything on the booster ended up with a blue tinge, in the end it really made a big difference to the visibility of the foam trail. This chick still has lots to learn from mother hen. :)

• We again pressurised the booster and sustainer to 120psi and launched. This time the release head released the rocket easily.

• This flight was almost identical to the first in terms of flight and performance and timing of events.

• The sustainer again had a bit of a spin but the staging plume looked nice and blue in the on-board video.

• The booster reached 163' (49.5m)

• The sustainer reached 810' (246m)! This helped confirm that the original flight was reproducible with this setup and pressure. Our personal previous altitude record was 637' (194m) flown with the Polaron VI rocket almost 2 years ago.

• The sustainer again drifted a long way down range. When I went to retrieve it I ended up in the wrong place and spent at least 20 minutes looking for it in the tall grass. I even tried climbing a tree to get a higher view. I was trying to listen for the lost alarm on the flight computer, but it was impossible to hear with all the crickets chirping in the grass. I need to make it louder.

• The FlyCamOne in the booster had stopped recording early again (before launch), exhibiting the power issues it had last year. The camera had an external power source (4 x AAA NiMh batteries) on this flight, but obviously it wasn't working properly. I have ordered a couple of new higher capacity LiPo batteries for the FlyCams hoping that this problem goes away, but they are still on back order so I hope to get them sometime middle of next month.

• We didn't have any issues with the altimeters like we did with one of them last week. The reset seems to have worked.

• The night before launch day we discovered that one of the launcher's nozzle seats had a crack all the way around in the solder where it attaches to the base. This made the whole nozzle seat wobbly. Because of the forces involved in that section, the crack was not considered to be critical and could be fixed after the launch day. On both flights the fill tube and nozzle seat ended up being pushed to one side, but had no effect on the launch itself. See photo on left.

Flight #2 Timeline

Together at launch the booster and sustainer carried the following:

• 3 x parachutes

• 5 x RC servo motors

• 2 x Z-log altimeters

• 3 x FC 1.6 flight computers

• 1 x MD-80 camera

• 1 x FlyCamOne 2 camera + power pack

• 1 x Gardena staging mechanism

We were very happy to finally get these two flights under our belt as it's been almost a year since we started designing this particular rocket. We have learned new construction techniques along the way so it's been a worthwhile exercise. We now know that this particular cluster/2-stage arrangement works well, and we hope to use it a few more times in the near future. It's also good to know that you can reach good altitudes at regular type pressures. The new splicing technique worked well on the 2L bottles, as did the new pressure switch.

Thanks also goes to Darren from Suburban Rocketry for helping to film the booster in flight.

What's next for Acceleron V?

There is good potential for further improvement in the Acceleron V design. We are considering a number of options for flying it again:

Shorter term:

• Increase the launch pressure to 130psi either for both sustainer and booster, or sustainer only.

• Reduce the weight of the sustainer by using smaller fins, replacing the 9V battery with small LiPo cells, replacing MD-80 with MD80 clone. These measures should reduce the weight by around 100 grams (~15%).

• Reduce the spin on the rocket.

• Add dual parachute deployment to the sustainer to limit drift.

• Extend each of the booster segments by another spliced pair of bottles.

• Extend the sustainer by another spliced pair of bottles.

Longer term:

• Reinforce the sustainer and launch it at higher pressures - 160psi+.

• Eliminate some tornado couplings and make longer spliced sections to gain more volume in the same length.

• Full booster segment length launch tubes on the launcher.

Here is a highlights video from the day:

Flight computer settings:

Miscellaneous

Charging LiPo batteries

While researching chargers for the little LiPo batteries, I found out that USB powered chargers typically deliver 100mA for the charge current. While LiPo batteries should be charged at 1C, I figured a 70mA battery could still be charged at 1.3C. The spec says maximum charge current for these is 2C. SparkFun electronics has a simple little 1 cell charger http://www.sparkfun.com/commerce/product_info.php?products_id=726 which looked quite good and affordable. I then realized that I already had one of these chargers in the form of the smashed FlyCamOne V2. The camera could be plugged into the PC and it seemed to work, but I could never get it powered up by itself again. I had to resolder one of the tiny SMD resistors which had broken on impact as well. After desoldering the old battery I connected one of these little ones. And to my surprise the FlyCamOne powered up again and I was even able to record a video using the little cell. WoooHooo... the good news is I now have a working camera again, but the bad news is that I don't have a charger anymore. I'll now buy a couple of new 350mAh cells for both FlyCamOne cameras since they were both a little under powered using their built in cells.

These 70mAh batteries came from HobbyKing: http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=7566

Acceleron V transportation cradle

One of the slightly annoying things has always been transporting the rockets in the car. You want to keep them as straight as possible during transport but have to raise them up enough to not rest on their fins. They can bounce around in the car as well. They are basically just awkward to pack. The Acceleron V rocket is even worse so we decided to build a dedicated cradle for it out of an old cupboard door. It locks the rocket in using an old Gardena quick connector and is further tied down with Velcro straps. This also makes it easy to work on the rocket on the table. See photo on left of the cradle.

Tornado Tubes

We finally decided to try out some commercial tornado tubes from http://www.coolthings.com.au/vortex-valve-tornado-tube.html to see how well they perform in rockets. The tornado couplings we have been using (re-threaded 3/4" BSP sockets) took about 15 minutes to make each on the lathe and cost about $4 in materials. These tornado tubes are ready made and only cost $2.50. These have been used for a few years in water rockets. Here is one Mat G. used them on his water rockets.

They have an internal baffle with a 9.5mm hole which isn't too bad, but you can easily widen the hole to about 18mm. This can be done with a round file or on the lathe. 18mm is plenty for a 15mm launch tube to fit through. The 9.5mm hole should be suitable for jet foaming. They each weigh 16 grams.

These tornado tubes are not specifically designed for pressure, and the plastic seems a little brittle. We hydro tested one to 130psi during the week to see how well it seals. There is a very fine ridge internally to the tubes that forms the seal when you tighten it. The tornado tube we tested held up well to the pressure without leaks. We are not sure what the upper pressure limit is for these tubes is yet.

If we get any leaks in the future, it is possible to fit an o-ring to the bottle to seal them up. We need to test fly a rocket with a pair of these couplings to see how they perform under real world conditions.

Launch	Details
1	Rocket   Acceleron Vc (Ac) and Axion IVb (Ax) Pressure   120 psi Nozzle   15.6 mm x 3 (Ac), 9mm (Ax) Water   7.5 L (Ac), 1.3L + foam (Ax) Flight Computer   V1.6 x 2 (Ac) and V1.6 (Ax) See settings above Payload   Zlog Altimeter x 2, FlycamOne2 x 1, MD-80 camera x 1 Altitude / Time   168' (51 m) Ac., 787' (239 m) Ax. / 12.6secs(Ac), 60.5secs(Ax) Notes   Very good straight flight. Sustainer had quite a bit of spin. Good parachute deploys on both sustainer and booster. Good altimeter data and video from both. Booster sustained minor damage to ring brace.
2	Rocket   Acceleron Vc (Ac) and Axion IVb (Ax) Pressure   120 psi Nozzle   15.6 mm x 3 (Ac), 9mm (Ax) Water   7.5 L (Ac), 1.3L + foam (Ax) Flight Computer   V1.6 x 2 (Ac) and V1.6 (Ax) See settings above. Sustainer set to 8.9 seconds for deploy for this flight. Payload   Zlog Altimeter x 2, FlycamOne2 x 1, MD-80 camera x 1 Altitude / Time   163' (49.5 m) Ac., 810' (246m) Ax. / 14.3secs(Ac), 58.7secs(Ax) Notes   Very good straight flight. Our highest altitude to date. Sustainer had quite a bit of spin. Good parachute deploys on both sustainer and booster. Good altimeter data and video. Booster camera failed (power issues) prior to takeoff.