Each flight log entry usually
represents a launch or test day, and describes the
events that took place.
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Day 28 - Foam Flights and 15mm Nozzle
Getting ready to fly Polaron III. Water is
still only in the lower bottle. We tip the
launcher over to get water into the next bottle
up.
Rocket is pressurised (low density foam in
upper bottles)
The foam trail extended almost all the way
to apogee.
J4 II launching with the Jet Foaming
technique.
Polaron IIIs last ever image. The white blob
is part of the fuselage, and a fin can be seen
in the lower right.
Now it will be easier to pack in the back of
the car.
It would have been fun to see it hit the
ground as it broke up.
An image from Google Earth showing the take
off point and where it landed. The park is
getting too small!
Jordan ready to fly with a 15mm nozzle and a
launch tube.
Transition to air pulse.
Date: 11th March
2007 6:45am -
8:30am
Location:
Denzil Joyce Oval. (launch site #4)
Conditions:
Clear skies and Mild temperatures. Very
light breeze.
Rockets:
(click the name for rocket details)
Team Members at
Launch Event:
PK, GK, John K and Paul K. Number
of launches: 5
We were really looking forward to today,
after almost a month of tests we were going
to fly both the foam and the baffle to see
how static fire tests compare with the real
thing.
Flight Day Events
First off the pad was Polaron III.
Since it was a first for us in using
foam we decided not to fly the camera.
From the tests we were expecting that
the thrust will be fairly low on take
off and so the rocket could tip over and
fly horizontally! We also saw in the
tests that the thrust phase was a lot
longer, so we decided to set the deploy
delay a little later too.
We pressurised it to 120psi and
launched. The rocket took off real slow
and proceeded to accelerate leaving a
beautiful foam trail behind it. It
almost looked like a pyro rocket. The
rocket arced over gently and the
parachute deployed soon after the thrust
phase so it didn't coast for too long.
The total flight time was
29.88 seconds which was probably
the longest for this rocket at this
pressure. (typical flight is ~27
seconds for 130psi) Although we don't
have qualitative measurements yet, we
believe that foam even without a CD
nozzle improved the rockets performance,
but it is too early to tell - more tests
are needed. The three seconds may no
sound like much but the rocket was only
at 120 psi, probably carried about 100 -
150 mL more water than usual, and the
parachute deployed a little early.
(If the video does not play, try the latest
Flash player from Macromedia)
Compare the thrust
profile for the same rocket at 130 psi
pressure but with a normal water/air mix
here: Day
25 Highlights video.
The noise produced by the rocket is
also very different to normal water/air
mix. The audio is a more continuous
noise with occasional hick-ups but no
definite air pulse.
We loaded it up again and this time
put the camera in it. The rocket took
off slowly again at a bit of an angle
and proceeded to accelerate but now
flying quite pitched over. We watched it
disappear on the other side of the
river. We did not see the chute deploy,
and there was a cheer from the
neighbouring baseball game. It took us
about 10 minutes to find it, completely
destroyed. The flight computer was still
on, and the parachute was out, but not
the secondary parachute. The main chute
probably came out after impact. The
camera survived and provided an
interesting point of view of the flight.
Later on Google Earth we measured the
distance to the impact site from the
launcher and it was over 200 meters. We
are still investigating why the
parachute failed to deploy. Well another
excuse to rebuild the rocket - parts of
it can be reused.
We also flew J4 II with the foam and
it also had a nice take off and left a
great foam trail. The parachute deployed
a little early, and the rocket landed
well.
We weren't game to test the 7mm
nozzle as the total thrust on takeoff
is even less. We will
try the 7mm nozzle with higher
pressures.
Because of the Polaron III crash we
weren't able to fly the baffle to see
what effect it has on flight. It will
have to wait for the rebuild.
We also tested an older rocket -
Jordan with the 15mm nozzle and a 300mm
launch tube. Quite a difference in take
off speed is evident, and sounds more
like a gun shot than the typical
restricted nozzle flights. The rocket
flew nice and high and survived the
landing well despite having no recovery
system.
The launcher also sprung a leak at
the hand tightened nut that attaches the
different release mechanisms. We'll have
to figure out why, but it is most likely
that it just wasn't tight enough as we
swapped the release mechanisms. It has
been sealing fine up this point.
Flight Record
Launch
Rocket
Pressure (PSI)
Notes
1
Polaron III
120
The rocket used Jet Foaming
technique with about 60mL of bubble
bath. (9 mm nozzle).
Beautiful flight with slow take off
and a long sustained acceleration.
Computer setting was 8 and the
parachute probably opened a little
early not allowing the rocket to
coast to apogee.
2
Polaron III
120
The rocket used Jet Foaming
technique with about 60mL of bubble
bath. Same configuration as flight
#1 but the with a camera added.
Rocket tipped over soon after launch
and from the video we saw that it
picked up a bit of spin. Parachute
didn't open and the rocket was
destroyed. Landed over 200 meters
from launch site.
3
J4 II
120
The rocket used Jet Foaming
technique with about 60mL of bubble
bath. Great flight with a long
contrail but the chute opened a
little early just after the thrust
phase. Good landing.
4
Jordan
120
First time tested with a 15mm
Gardena nozzle and a 300mm launch
tube. Very fast take off and fairly
high. Landed well and was undamaged.
5
Jordan
120
Tested again with an almost
identical flight profile to launch
#4. Rocket was undamaged.
Notes to Self
Put a beeper on the rocket to make it
easier to find.