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Day 88 - Dual Deployment Mechanism
Dual deploy mechanism is a combination of
the side and in-line deployment mechanisms
The drogue parachute is in the nose, and the
main in the side.
Getting ready to launch the dual deploy on
its first flight.
Launched using a 9mm nozzle and 130psi.
Shortly after the main parachute opened.
The kids are now well trained to correctly
pick up the parachute and rocket. They even know
how to turn off the flight computer.
Turning on and attaching the MD-80 clone
Second flight ... just starting air-pulse.
(Photo: Andrew E.)
Flying the MD-80 clone. The video quality is
quite good in sunny conditions.
Both chutes were attached to the center of
gravity to make the rocket come down sideways.
(Photo: Andrew E.)
CATO on launch #3 destroyed the lowest
bottle. Here the nozzle is pushed up into the
Top of the bottle blew off. The Robinson
coupling remained in the top bottle.
Fourth flight. Both the rocket and launcher
have been extended.
Coming down under the drogue.
Panorama made from a composite of a number
of frames from the MD-80.
There were some very impressive pyro rockets
Pressure testing the nozzle seals on the
Acceleron booster. You can see the fog in the
Pressure testing the staging mechanism.
There was a small leak, so we replaced the
Gardena quick connector.
Aligning fins on the booster with the use of
a fin alignment jig.
Slowly taking shape...again....
Mounting the FlyCamOne in the lower part of
the rocket. Another camera will be on the
Tornado coupling Jet Foaming insert.
Date:27th February 2010
Location:Doonside, NSW, Australia
Conditions:Warm (30C) with mostly clear skies and
Team Members at Event:PK,
John K .
This week's update is a bit of a mixed
bag of different things we've been working
on since the last update. We did test
flights a dual deployment mechanism, test
flew the MD-80 clone camera and continued
work on the Acceleron booster.
Dual Deploy Mechanism
A dual deploy mechanism is designed to
open a small drogue parachute near apogee
and allow the rocket to fall in a controlled
manner but at moderate speed. As the rocket
approaches the ground the main parachute is
opened to slow the rocket down for a gentle
landing. This is done to minimize rocket
drift in windy conditions.
This dual deploy mechanism is a
combination of our
side deployment and
mechanisms. It was
from Washington Water Rockets who last month
suggested this arrangement so thanks for
that.:) For the first flight tests we simply
mounted the mechanism from the earlier tests
on top of an existing side deploy mechanism.
In its final form the in-line servo will be
integrated in the side deploy corriflute
frame. This will shorten the the whole
mechanism by about 1 inch and save a little
bit of weight. The prototype dual deploy mechanism
weighed in at 162 grams or around 25 grams
heavier than the side deployment alone. The additional
drogue parachute weighs 13 grams.
The flight computer we are using to
control the timing was designed with dual
deploy in mind, but this was the first time
we had actually flown it in that
We arrived at Doonside at around
9am. The conditions were almost ideal
except with wind blowing around 10km/h
with occasional higher gusts. We had a
couple of things we wanted to test this
weekend. One was the dual deploy
mechanism and flight testing the MD-80
clone camera. (see below)
The first flight of the day was
II with the dual deploy
mechanism. The deploy timing was set
conservatively since we didn't know
how exactly the rocket would behave under the drogue parachute. In
case the drogue didn't open, the main
was timed to open still before a
ballistic return to Earth. The drogue
was timed to deploy 4.2 seconds after
launch and the main was set to open 12
seconds after launch.
We tied both parachutes around the
center of gravity of the rocket to help
it come down sideways for increased drag
and in case only one of the parachutes
opened. In later configurations we may
try tying the drogue all the way down
near the nozzle. This would then allow
the rocket to come down nose first a
little faster and allow the main chute
maximum clearance when it is ejected.
We didn't attach the camera on the
first flight in case we would have
to perform shovel recovery on the
Thankfully both parachutes opened
when they were supposed to and the
rocket landed well. It landed pretty
close to the trees though. From video
the actual fully inflated parachute times were
5.2s for the drogue
and 13.4s for the main.
We left the parachute timing the
same for the second flight which was
almost identical except we mounted the
MD-80 clone camera in the side of the
rocket. The parachutes again behaved
themselves but because the wind had
picked up at that stage the rocket
drifted down range a bit. The main chute
timing could have easily been extended
another 5 seconds for lower opening. The
view from the camera was nice and clear
and due to the low spin rate the video
was quite stable. The drogue timing was
5.6s and the main was at 13.7s.
Due to the higher wind conditions we added the guide rail
extensions to the launcher.
For the third flight we wanted to
fly a foam rocket which meant swapping
out the bottom fin section on the
rocket. This fin section has a Robinson
coupling in the bottle which allows us
to use Jet foaming. This particular
bottle with attached fins was made back
in August 2008 and has seen perhaps a
dozen launches since. As we approached
120psi, the base of the bottle failed
around the Robinson coupling resulting
in a nice CATO. The rest of the rocket
with the attached Robinson coupling now
acting as a nozzle flew off, but without
fins it pitched over and landed on its
side safely in the grass. The rocket
landed before the drogue parachute had a
chance to open.
Other than the blown up bottle,
everything else remained undamaged. One
of the launcher guide rails was slightly
bent from the explosion, but can be
easily bent back. The on-board camera
also captured the action.
We screwed on another fin section
and the rocket was ready for it's fourth
flight. The last flight was flown at
125psi. The dual deploy mechanism worked
well again and the rocket landed without
We had one issue with the MD-80
clone camera though. When we downloaded
the video from the explosion, it said
the file was corrupt, but VLC Media
player fixed it and we were able to see
the entire movie. We always download the
video after each flight just in case the
rocket is damaged or lost. When we flew
the last flight, I noticed that the
camera only had the two original files
on it, there was no third flight. This
looked like a malfunction, or perhaps I
didn't press the record button properly.
It wasn't until I got home and was
downloading the videos again from the
camera that I noticed that the second
file contained the last flight. Because
the second file was corrupt the camera
simply recorded over the previous
flight. Luckily I had the original
second flight on the laptop that we
downloaded on site after the explosion,
so we were able to recover all three
videos. I am not sure why the AVI file
was corrupt, perhaps it just wasn't
closed off properly although all the
video was there. The explosion may have
had something to do with it, but I'm not
really sure. So just in case, back up
your videos after each flight!
I think we will add the dual-deploy
mechanism to our box of spare parts that
we bring with us. We can attach it to
rockets when there are higher wind
conditions at the launch site.
Here is a highlights video of the dual
deploy mechanism in action:
Otherwise it was a great day for rockets
both pyro and water. There were quite a few
new faces at Doonside and quite a few larger
pyro rockets too. Here is a pyro highlights
video from the day:
Acceleron V build progress
Since the last update, Acceleron V has
been progressing well. It is now mostly
assembled with a few more minor things to
do. We did pressure tests on the new nozzle
seals, and decided to make them a little
wider so dad machined up a new seal cutter.
We also cut the new seals out of harder
rubber so they would not distort so much
when the bottles were tightened.
We pressure tested the staging mechanism
and discovered a minor leak in the Gardena
release head. It looked like there were a
couple of scratches in the o-ring seat where
the sustainer nozzle sits. This was a fairly
minor leak but we decided to replace the
Gardena quick connector. We still need to
pressure test it this week.
The focus now is on getting the
sustainer finished. The sustainer is being
made from all new spliced bottles. The
fin-can is now finished so hopefully we'll
be able to pressure test the whole rocket
After the failure of the bottle in the
Robinson coupling this weekend
we had a discussion in the car on the way
home, and dad suggested that instead of the
Robinson coupling we could put an insert
into a tornado coupling to give us the
same size jet of water to create foam. Since Acceleron's sustainer uses Jet foaming, we
may replace the Robinson coupling with this
insert to try to reduce the chances of
another bottle base failing. Over the years
we've had quite a few bottles fail this way.
If it works it would also eliminate a metal
component from the pressure chamber.
On Sunday he machined up the insert for
our tornado couplings that has a converging
section at the top end and a straight
section in the bottom for the water jet. We
will do a couple of static tests of this
arrangement to see how well it works. We
made an 8mm hole in the insert which the
same as our Robinson couplings since we know
the performance envelope of a hole that
size. We may also try the insert upside down
with the divergent section pointing down.
The theory there goes that as the water/air
comes down from the upper bottle some of it
will be deflected towards the sides of the
bottle helping to reduce the blow through
effect and also assist in preventing the
water and foam from sticking to the sides.
The static tests will also be done this week.