Each flight log entry usually
represents a launch or test day, and describes the
events that took place.
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Day 23 -
Coloured water ready for filling Acceleron.
Filling the dummy payload with about 600ml
of water. The water empties through the same
holes it is filled with.
Packing the 900mm parachute.
You can clearly see the coloured streams
from each nozzle.
This launch made a nice rainbow. A small
camera was attached about 3/4 way up the right
Video frame showing the water columns just
before the air pulse...
...and just after the first segment emptied.
You can see the air vapour as well as the water
column from the other nozzle.
Some launches were very close to vertical.
Slightly tangled parachute on descent.
Good lighting on the coloured columns.
Sometimes the older kids get to recover the
A newer cluster rocket with 3
segments and 3 nozzles.
A newer rocket built by our new
Team Members at
PK, GK, DK, TK, Paul K and John K.
of launches: 6
This day was all about test flying the
Acceleron rocket again. We wanted to get
more test flights under our belt to better
characterise the performance of a cluster.
We were quite pleased with the days results, and
especially with the fact that the parachute
opened on all flights.
Flight Day Events
Acceleron takes a lot longer to set up
and launch compared to our smaller
rockets. We average about 10-15 minutes
now between launches. After each launch we
have to reseat the o-rings in the
launcher, remove the segment nosecones,
remove the filler caps, fill each segment
through a special filling funnel, close
each segment again, re-attach the segment
nosecones, pack the parachute under the
top nosecone, fill the dummy payload with
water, pressurise, get the team into
position, roll video and launch.
We had Acceleron covered from a number
of vantage points on video and stills so
that we could see its performance. Of
particular interest was the timing of the
air-pulse from the individual segments as
at this transition point there can be
quite a difference in thrust between the
segments if one is still ejecting water
while another is going through the
air-pulse. On slow motion replay it is
very noticeable the different times that
each segment goes through the air-pulse.
Although they do not all happen
simultaneously, we found that the rocket
only rocked slightly, but kept flying
We are interested in what happens to the
rocket at this point as this is the point
at which the second stage will separate.
We want to minimise any unnecessary loads
on the separation mechanism.
On a couple of the flights Acceleron
went fairly straight up which was
encouraging as that will be needed for
second stage. For the other two flights
the rocket arced over a bit, but again we
had fairly windy conditions, so we are
looking forward to calm conditions to try
On Acceleron's last flight, we
realised we had the small video camera we
normally used for in-flight video for
Frankovka. So we decided to just tape it
to the side of one of the segments for an
impromptu in-flight video. The video wasn't
great but the rocket was never designed to
carry a camera. It did give us another
perspective though of how the rocket moves
in the air with the three nozzles.
(If the video does not play, try
downloading the latest
Flash player from Macromedia)
Note: The video quality here is limited by
what YouTube offers, we have higher
definition video of all the flights,
unfortunately it would take up too much
space on our ISP.
On the slow motion replay of the
flights we noticed that the water columns
tended to come together a few meters
behind the rocket. We attributed this to
the air coming back together after flowing
around the rocket.
We need to improve the robustness of
the fins on Acceleron. The landings are
pretty hard on the fins. We have already
snapped one, and the fin strut broke on
this day as well. The parachute is still a
little too far forward and the rocket
still tends to land on the tail. The frame
had bent a little, but we were able to
straighten it and let it fly again.
When we were swapping launchers, we
tugged a little too hard on the air hose
and that managed to knock the SCUBA tank
over. The pressure gauge was damaged and
could no longer be used. The pressure
regulator seemed to be okay, so we will
have to swap in a new pressure gauge for
the next flight day.
We also launched Danny's Millennium
Falcon rocket a couple of times and it
flew very nicely. Without a parachute it
sure comes back to earth pretty fast.
1.5L of water used
in each segment for a total of 4.5L.
The rocket flew in a slight arc, and
the nosecone fell off soon after the
air pulse, but the rocket continued
for another few seconds before the
parachute finally started opening.
One fin strut was damaged, but was
1.25L of water used
per segment. The rocket went
straight up with good performance
from all nozzles. Parachute opned
before apogee and the rocket landed
1.25L of water per
segment. This was a good flight with
the rocket again arcing over gently.
Good parachute deploy and a good
1.25L per segment.
The rocket flew with a camera
attached to the side with a piece of
tape. The flight was a little short
with the parachute deploying a
Pressure unknown as
the pressure gauge was damaged. This
was a very good flight and went
straight up. Good bounce on landing
but no real damage.
The rocket arced
over on this flight but flew well.
Crushing of the bottle was a little
more severe on this flight, but
should be ok.
Design and Development
We have also been building a new launcher
for our new regular non-cluster rockets such
as J4 and
Polaron. The new
launcher should be adequate for the next
phase of development of longer rockets. It
is fully adjustable for rockets of various
diameters, and uses an all-metal Gardena hose
attachment release mechanism. The guide
rails are now 2 meters (~7 feet) in height
and a lot sturdier. The base is also much
wider. The launcher can accommodate rockets
with ring fins as well as conventional fins.
More details and photos of the new
launcher with the next update.