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events that took place.
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Day 57 - Acceleron IV and Polaron IV Flights
Ideal weather conditions for flying rockets
Setting up Polaron IV
We're always loosing things in the tall
Launch control giving final signals before
A good vertical take off. On its way to
Unusual flow of water from the red booster.
Polaron IV's altimeter profile.
Those aren't stars, those are blobs of foam
falling from the nozzle.
Fellow NSWRA members.
The large parachute lets us easily find the
rocket in the grass.
Filling the Tachyon sustainer with 800ml of
water and foam.
We turn everything on before we place the
sustainer on the booster but require a step
ladder to arm it.
Sustainer parachute tangles on the way down and
hence the unusual downward shape of the altitude
Sustainer and staging mechanism up close.
Prepping Acceleron IV for its second flight
of the day.
This time it is launched at 130 psi.
Corresponding altimeter data for the last
Acceleron flight for the day.
A panorama taken on the last flight as the
rocket pitched over at apogee.
Inspecting other rockets flown on the day.
This is one of our only few non-fuzzy shots
of pyro rockets launched.
Dad's monumental effort in machining all
these parts that make up the control panel.
The innards of the new control panel.
The exterior. I really like the retro look
with brass screws.
29th March 2008 (8am -
degrees C, wind speed < 5km/h gusting in
afternoon cloud cover 3/8
Team Members at Event:
GK, PK, John K, Paul K, AK, HK + Members of NSWRA and
It was another great weekend at the
launch event this month. The weather
conditions were perfect, although the ground
was a little wet and there was plenty of mud
everywhere. People brought some very
impressive rockets that are always fun to
see. I have included a video of the last
months pyro rocket highlights
Before we get into the events on the day
I'll cover some development topics leading
up to the launch day.
We finished rebuilding the Acceleron IV
booster a few days earlier. The main
difference being Acceleron's lower capacity
of around 18L compared to the previous 24L.
Each of the booster segments are now
attached by 3 strips of Velcro which makes
it much easier to get them on and off for
During full operational pressure tests we
discovered that the rocket wasn't sealing
well at all. Further inspection revealed
that we forgot to put in washers into 3
Robinson couplings. Doh! We had test
assembled the rocket 2 weeks earlier, and
forgot we hadn't gone back to put the seals
in. 5 minutes later all the seals were back
in and we ran the rocket up to ~100psi since
the neighbours were out in their back yard,
and having had this rocket fail a pressure
test in the past, we didn't want to push it.
We did have the video camera recording
though just in case. The rocket will most
likely get launched at 120psi on the day.
The rocket theoretically should hold up to
around 140psi operational pressure, with a
burst pressure of around 180psi.
We hooked up all the electronics and made
sure the staging still worked when the
pressure in the rocket dropped. We replaced
the sustainer in the test with a small
bottle full of water that fired as expected.
We replaced the rubber bands in the
staging mechanism as keeping them stretched
all this time in storage caused them to
deteriorate quite badly. The same went for
the wide rubber bands that held the fins on.
The launcher has also had an upgrade with
new longer fill tubes that allow us to use
the spliced pairs of bottles on the bottom
of each segment. We simply slipped new
thin-walled aluminium tubes over the
existing ones and epoxied them down.
Tachyon III Sustainer Work
The altimeter has been moved into the
space between the bottles that help to
protect it. The altimeter is attached to the
inter-bottle ring and having its own power
supply allows us to swap it between rockets.
The payload section now also has the
FlycamOne2 camera built in.
We also made a couple of rocket carriers
that help us transport and protect the
rockets. They also help prevent the rockets
from sagging in warm conditions.
Dad surprised me on my birthday last week
with a control panel he made for the rocket
launchers. We can use it with all our
launchers and especially the dual air supply
ones. See photo on left. The panel has a
pressure regulator, two valves for the lines, a bleed
valve and four gauges that show the tank
pressure, the regulated pressure coming out
of the regulator and then the two line
pressures. It comes with foldable legs, so
it stands up all by itself. Virtually all of
the internal fittings he made on the lathe
that connected everything up. It
has a great looking retro look. I am looking
forward to using it next time.
Okay now back to the launch day.
Launch Day Events
We first set up Polaron IV on the pad. It
was flying in the same configuration as the
previous month, but with the wind conditions
being so calm we wanted to see what
difference it makes to altitude. The
previous month we had really strong winds
and the rocket fish-tailed quite a bit.
As the pressure reached around 90psi, the
main stage nozzle sprung a leak. We could
have launched, but I had the deploy timer
set on a longer delay expecting the long
boost. If the rocket had not reached a high
enough altitude there was the danger that
the parachute would open too late. Over the
last 2 years we have learnt that if
everything is not 100% correct just before
launch, it is much better to abort and try
We were glad that we had the bleed valves
in the launcher, and we safely released the
pressure from both the main stage and the
The seal probably wasn't sitting properly
which sometimes happens, but on removal we
noticed that there were also some small aluminium
shavings in it. I am not sure of the source
but perhaps when the nozzle was left out in
the workshop. We washed them out,
reconnected the nozzle and all was fine.
We pressurised to 120psi and let the
rocket go. The boosters again behaved as
predicted and the flight was almost
completely vertical. Altimeter gave us an
altitude of 510'. The in-flight video also turned out
Bizarre Flow: Both the ground video and a
still photo showed our first mach diamonds.
Well not really mach diamonds as such but it
was quite a bizarre flow from one of the
boosters. There were definite pulses visible
in the water flow, but only one of them
showed this. The video shows there were two
distinct pulsing events before water ran
We have not seen this before in any of
our launches. So far we have no idea how
they originated. Perhaps some sort of
cavitation effects caused it? You can see
the column of normal flow before the pulses
start. You can also see that the booster
(red one) is nowhere near its air pulse as
there is still quite a bit of water left in
it. It didn't seem to affect performance as
far as we could see, so we will not try to
do anything about it, but will keep an eye
out on future launches to see if it happens
again. The boosters are numbered so we will
be able to track it down if a particular one
Next off the pad was the newly rebuilt
Acceleron IV booster with the Tachyon III
sustainer. Again we were struck by a minor
fault that caused us to abort the launch.
This time it was the fact that the rocket
wasn't locked down all the way. It was
locked down earlier in the checklist, but
somehow we must have caught on the string
during preparation and unlocked it. This
has happened once previously and is a reason
why it is on the checklist. We now know to
double check prior to pressurization.
As we reached about 20psi, the booster
started hopping up and down a few
centimetres as it started venting the water.
The guide rails did their job preventing the
rocket from tipping over. As the water
drained we ended up with a small air pulse
and the pressure drop was detected by the
flight computer and deployed the sustainer.
The sustainer had just enough pressure to
lift off perhaps 10cm and clear the booster.
As it did so, it sprayed foamy water all
over the electronics pod and the side of the
booster. The sustainer luckily fell on its
tail and suffered no damage. On board video
and altimeter captured the whole sequence.
We cleaned up the mess, dried off what we
could and refilled everything again. This
time the rocket was locked down properly. We
turned everything on again and filled it to
The launch was very good and mostly
vertical. Staging happened right on cue and
the sustainer proceeded to fly to 160m
(525') according to the altimeter.
Both parachutes also opened, but the
sustainer's parachute tangled and the rocket
hit the ground at a less than ideal
velocity. Thankfully the parachute was out
and causing some drag, and the ground was
soft with tall grass, heavy damage was
done to the nosecone. The altimeter was
ok, and all the electronics and camera
survived well. The camera did not record any
footage that we could recover. I noticed
that the SD card had popped out of the
camera on impact. It was either this or a
power spike that caused the camera to stop
recording or corrupt the file.
For Acceleron's last flight of the day we
fixed the sustainer by replacing the
nosecone section from the Hyperon rocket we
had along as standby. The altimeter ring was
simply reused, but the Hyperon nosecone did
not have a bay for the new video camera so
we just taped it to the side with duck
(gaffer) tape. This was less than ideal
aerodynamically, but we weren't after
altitude, but the footage. The rocket
reached 153m (503'). The parachute opened
well on the sustainer and it landed close
to the tallest trees in the field. The
booster's parachute opened very late,
apparently only a couple of meters above the
ground. I couldn't see it as I was tracking
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Good launch and
separation. A4 opened parachute well
above ground. T3 opened right around
apogee and tangled on the way down.
The nosecone was heavily damaged.
Altimeter, cam and flight computer
ok. cam failed to record card popped
out. A4 okay.