Each flight log entry usually
represents a launch or test day, and describes the
events that took place.
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Day 20 - Cluster
Air Command team members present on day 20,
sporting their new uniform.
Getting the camera rolling on Frankovka III.
Retrieving the rocket. This picture reminds
me of another that I have seen before.
Great shot of the water column and the start
of the air pulse from Frankovka III.
J4 powering up to ~130 meters before lawn
darting at 160km/h.
The lathe has now produced quite a number of
components, for rockets, launchers and necessary
Cluster rocket and launcher under
development. Note the spear gun trigger release
Cutting out the cluster support frame.
Components of the support frame.
Support frame fitted to test cluster. Note
the colour coded lids so that we know which way
round it goes.
Launcher base with slot cut out for the
Test launcher setup to test release and
Launching with air only ~15psi.
The cluster is attached by a string so it does't
leave the backyard.
This is a newer rocket made out of
three 1.25L bottles. Parachute
deployment is achieved using the
Rocket is typically filled with 1.1
liters of water. The nosecone was
slightly modified from the last day
where it was deploying too early.
Team Members at
PK, GK, Paul K and John K.
of launches: 5
With all the busy Christmas and holiday
rush over we were ready to go fly again.
Although the day was short it was still fun.
Crashing rockets are always fun to see. We
also continued further development on the
next still unnamed big cluster rocket (see
Design and Development below).
Flight Day Events
We flew Frankovka III three times on
the day once with a video camera and twice
without. We only fly the camera once since
we don't usually bring a laptop to the
park to download the movie. We have to do
that back at home. There is only enough
memory on the camera for one flight. The
in-flight video was very good and shows a
nice panorama of the area.
On the first flight the parachute
deployed as expected, however, the canopy
didn't open and the for a couple of
seconds it looked like we were going to
need a broom and dust pan to pick up the
pieces. But then the canopy opened and the
rocket landed well. Perhaps the chute
lines were somewhat tangled. On the video
you can hear the wind rushing past as the
rocket starts accelerating towards the
The last flight for the day of
Frankovka III was the FC's 16th flight and
so far a 100% deployment success.
We then launched J4 (renamed from
J4Y). On the launch pad we noticed that
when the rocket was pressurised the
nosecone was a little sticky and didn't
want to come off quite as easily as we
liked. We tried loosening it by cutting
a number of slots around the edges, but
it still didn't feel quite right. I
managed to convince dad, that when the
pressure drops on launch the bottle will
shrink and the nose cone will be looser.
So we launched it at 130 psi. The rocket
went straight up and straight down. I
might have mentioned the odd four letter
word on the way down. The rocket
suffered heavy damage, and it did not
fly again on the day.
One good thing did come out of it
though. Since the parachute didn't open,
and with the rocket landing close to the
launch pad, it allowed us to calculate the
approximate maximum altitude. With a
flight time of 10.88 seconds [measured
using video frame by frame analysis], and
entering all the rocket parameters into
the simulator, we get an apogee of around
130 meters (~425 feet). The simulator
estimates that the rocket hit with a speed
of around 160km/hour (100mph).
This week we did not see the sort of
pitching over of the rockets like we did
last week. We are trying to identify why
some of our rockets pitch over
significantly just after takeoff.
Since J4 was damaged, we flew an older
rocket "Clifford". One of the most notable
differences with the smaller rockets is
how much faster they accelerate off the
launch pad compared to the bigger rockets.
They also descend a lot slower.
Flown with a camera,
and the computer was set for 4.75
second deploy. Chute tangled on the
way down, but opened well above
ground. Rocket landed well.
Very good straight
flight, with deploy set to 4.75
seconds. Good deploy and safe
Very straight flight
up, but nosecone failed to separate,
and as a result the rocket crashed
heavily. Flight time of 10.88
The nozzle seal
leaked at around 100psi, so it was
launched. The rocket went fairly
well, but the parachute opened a
little early and the weighted
nosecone was ripped off.
This was another
great flight, with good deploy and
Design and Development
As we develop our higher performance
single stage rockets, in the background
we are experimenting with the next phase
of development - multi stage rockets. We
are currently designing and building the
booster of a two stage rocket.
The booster consists of a cluster of
3 segments. A segment is a number of
bottles joined together end to end to
form a part of the booster. The reason
we refer to it as a cluster is because
each segment has its own nozzle.
The booster release mechanism
consists of a single central rod with a
slot cut in it that fits into a spear
gun release mechanism. The trigger will
be remotely activated by a string. We
went with a single release point as it
simplifies the design and also ensures
that all the segments of the booster
Each nozzle of the booster is simply
a thin walled aluminium pipe with a
flange on the end that holds the seal.
The launcher ports have an o-ring in
them to seal the nozzle. There is one
central port that has air input and two
outputs for air to flow to the other
Our first test of the setup didn't
go quite to plan as the segments are only
single bottles and there is no way to
equalize the pressure inside them except
through the launcher. What ended up
happening was as we turned the air on,
because the hoses between the ports were
all filled with water, as air came to
the central port, it started
pressurising the bottle, and then a
second or so later, the air finally made
it to the other bottles. When we turned
the air off, we noticed that the central
bottle having a slightly higher pressure
started emptying all the water by itself
into the other bottles. We half expected
that that might happen, but it was good
to see it in practice.
We are now modifying the design to
allow only the air to equalize the
pressure without transferring the water
in each segment. We chose to have the
launcher handle the equalising, as it
makes booster construction simpler.