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Day 132 - Painting the sky with Inverter
Date:30th
March 2013
Location:Doonside, NSW, Australia
Conditions:Sunny, light winds < 10km/h
early,
25C
Team Members at Event:GK,
PK, Paul K, Jordan K and John K.
Launch Day
It was a beautiful morning for launching
rockets. The skies were clear with only a
light breeze.
With the launcher leak fixed from the last
Inverter launch, the Inverter rocket was the
first off the pad. During the last launch we
noticed that the water with food colouring
that we poured in
first stayed in the lowest spliced-pair, and
really didn't want to mix with the water in
the upper spliced pairs. We had to squeeze
the lowest bottle to pump it around to mix
up. The launch tube in the Tornado coupling
makes a pinch point with very little cross
sectional area for the water to mix. This
got us thinking and so we decided to put different colours in each of
the spliced pairs to see if we could change
the colour of the water stream in flight. We
knew that the top two colours would mostly
mix by the time they got out, and so we
chose blue and yellow for the top two
colours so that when they'd mix we would get
green.
Pouring in blue
Putting on the air manifold
After 20 minutes the colours
mixed a little
For the first launch we had prepped the
rocket and poured in the water but had to
wait about 20 minutes to get all pyro
rockets launched first. By the time it came to launch this rocket, some of the
colours had mixed a little.
We launched this one sooner so
very little
mixing took place.
Getting ready for the second
flight
We launched the rocket at 120psi, and
again it had a nice slow take-off, and
then accelerated well. You could see the
different colours as it flew but it was
fairly quick. The rocket reached an altitude
of 395 feet
(120m). You can see how the colour changes
in the photos below. These are extracted
from the video sequence.
Composite of the changing
colours
Although the rocket arced over it was
very stable on the way up and didn't roll
which always makes for good on-board video.
During the last Inverter flight we noticed that the
rocket rocked sideways under parachute and
so we added a couple of stabilising strings
to try to keep it level and give a better
view. This worked very well. Next time we'll
have to put a second camera facing down to
get a view of the ground when it is falling
under parachute.
On the second flight we got the rocket up
in the air within minutes of filling it with
different colours and so they hadn't had a chance to mix
very much at all. The problem is that as the
rocket is pressurised the volume of the
lowest bottles increases and water flows
between the sections mixing to a certain
extent.
The second flight was very similar to the
first, and again you could see the change in
colours. It's much more visible though on
the slow motion video. The rocket landed
again without any problems. I know for sure I forgot to turn on
the on-board camera on this flight as there
were too many distractions at the time. The
rocket reached an altitude of 377 feet
(115m)
Here is a
video of the changing colours:
Materials Challenge Revisited
For this week's launch we also wanted to
revisit the materials challenge
from the last launch
day to see if we
could strengthen the fins to survive the
high speed and acceleration. We reused a couple of the rockets from
the last attempt and reattached the fins
using a different technique. This time we
cut little flaps on the fins and cut some slots in
the fin can fairing and then alternatively
welded the tabs inside and outside the fairing.
This way it wasn't only the welds that were
holding the fins on. This definitely felt
like a
much stronger connection.
Newly attached fins
We then swapped the release head over to
the Clark cable-tie launcher and put the
repaired PETOne rocket on it. At 120psi it was a very fast
launch, and this time the fins stayed
attached! The rocket went straight up and
straight down and landed less than a foot
from the launch pad. With a flight time of
8.8 seconds according to the simulator the
altitude would have been close to 302 feet
(92m). When the rocket hit the ground one of
the fins came off again.
We took the second rocket and pressurised
it to 130psi. This time the launch must have
been even faster as you could hear the fins
flutter on the way up. This would have
created a lot more drag and as a result the
flight time was only 8.4 seconds. All fins
stayed attached even after landing. I think
for the higher pressures the fins would need
to be reinforced or redesigned to withstand
the high air speed. We are now satisfied
that this challenge is completed. The
crumple nose recovery is working well, as
all you have to do is pull the neck out and
the rocket is ready to fly again.
Our last launch of the day was the old Axion
II. Launched again at 120psi it went up nice
and straight and the parachute opened nicely
after apogee.
There was also a great turnout
at the launch with lots of pyro rockets
(around 70) going up on A to H motors which was great to see.
