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events that took place.
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Day 119 - Sydney Observatory and Altimeter Flights
Sydney Observatory 17th April 2012
Back court yard at the Observatory where the
observatory staff had their water rocket
NSWRA's static display was set up indoors
due to the bad weather.
David and John getting ready to launch a
rocket on the front lawn.
The small paper rocket launched on a 1/2A
motor. The rocket landed back on the lawn.
Parents and kids gathering ...
... for a static motor firing demonstration.
There were close to 500 kids and parents
that attended the observatory.
John setting up for another motor firing.
This time it was an E9 motor.
Doonside 28th April 2012
Setting up the small Axion III. There is no
need to detach the rail for this rocket.
Launch #1 at 120psi
Landed close by.
AltimeterOne says 296 feet.
The grass just keeps growing and growing.
2nd landing after being launched at 90psi.
A good day for NSWRA - a full rack with 71
entries in the log book for the day.
Lawn mowers and rockets ... what more do you
Paul's Pod-2 finding an empty rail.
It flew well again on a C6-5
3rd Launch was only at 70psi.
The rocket flew to 158 feet.
Axion V launched at 120psi.
It was a very slow launch.
Looking down from around 329 feet.
Flight time was around 26 seconds.
Rocket landed close by again.
2nd Launch at 125psi.
Rocket flew to 389 feet.
There were quite a few people at the NSWRA
Conditions:24C, overcast calm Team Members at Event:PK, Paul K and
Two weeks ago I took a day off from my
regular daytime job and went to the Sydney
Mini Rocket Scientist Party day to
help out as NSWRA was doing demonstrations there
for the kids and parents. Because the
so close to the city, a major freeway
and a helicopter flight path, we
could only launch the smallest paper
rockets on 1/2A motors. These were still
great for the kids to see. We also did a
number of static motor firing displays
up to an E motor so the kids could good
get an idea of the noise and smoke they
generate in bigger rockets.
We also had a static display set up
videos and rockets & motors the kids could touch.
Unfortunately it was quite a rainy day
and so we could only launch during the
breaks in the weather. Still it was a
great day and the Sydney observatory
staff even had a water rocket range set
up for the kids. They were launching
rockets to perhaps 30-40 feet as the
rockets only used half a tennis ball for a
recovery system. Despite the adverse
around 500 kids and
parents attended the open day. A big
thank you to all the staff at the
observatory for making it a great day
Shadow 2 Update
I've updated the
Shadow 2 build log with some recent
repair progress. It's mostly been a
fairly easy process since we have been
through it once before and there really
aren't new design considerations to be
made. Since we are repairing the top of
the pressure chamber, we decided to
extend it somewhat for more capacity,
The exact final extension (and capacity
increase) is still to be determined, but
at the moment it looks like the rocket
will be about 250mm longer.
will need to do a full pressure test
again because we are not sure if the
crash had weakened the pressure chamber
in any way. This will also test the seal
around the nozzle bulkhead since it moved so
far down the rocket on impact.
Our rocketry club (NSWRA) bought a
number of the AltimeterOne altimeters
recently for use in club competitions.
I've now seen quite a few people using
these on their water rockets as
I've always been hesitant about using
altimeters that detect launch themselves
as they usually rely on some threshold
to trigger them. The trigger condition
usually is a certain gain in altitude
over a given period of time. The problem
with some of our water rockets is that
they have a very slow take-off
especially when using foam. The altitude
threshold for launch detect on the
AltimeterOne is 50 feet, but I am not
sure over what period. So
this weekend we flew a number of flights
to see how well the AltimeterOne triggers on slower moving rockets.
We flew the small 3.35L Axion III rocket
3 times at 3 different pressures. All
three flights used 900mL of water and
were launched at 120psi, 90psi and
70psi. We then flew the Axion V rocket a
couple of times using foam and 1900ml of
water. These were visibly slow launches
off the pad.
In all five flights the AltimeterOne
performed really well, and the reported
altitudes looked about
right meaning they weren't reporting
spurious altitudes. Sometimes this a problem
with peak only altimeters. Overall the
AltimeterOne is very well designed and
simple to use.
I think we will use the AltimeterOne on
the less critical flights and continue
to use the logging altimeters for the
more important flights. I can see the
AltimeterOne useful in experiments where
you are testing a feature of a rocket on
repeated flights to see how the
performance compares to a rocket without
We mounted the altimeter with a couple
of wire wraps to the inside of one of
the inter bottle fairings and cut a
hole for the button. We also made sure
the fairing had a vent hole in it to allow the
pressures to equalize on the inside.
Apparently the colours of the #16
camera are supposed to be more
realistic, though I prefer
the more vibrant colours of the #11.
These flights weren't a true test of the
colours because it was an overcast day
and so everything usually is a little
washed out. But other than that the
camera is quite good and doesn't drop
frames even in complex scene changes.