Each flight log entry usually
represents a launch or test day, and describes the
events that took place.
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Filling the booster. Each segment was filled
with 1.5L for a total of 4.5L.
The sustainer air supply on the left and the
pressure switch (TDD) on the right.
Sustainer was filled with 800mL of water and
bubble bath mix.
Programming and Arming the sustainer flight
computer needs balance.
Looks like we are doing a little voodoo
dance ... probably just deep in thought.
Off to set a personal altitude record.
Just after separation. The booster is off to
the left.
Our cars on the left, and the team on the
right. The black square on the tarmac was used
to calculate altitude. It is 33m wide.
Apogee. Yup those are the Blue Mountains on
the horizon.
~ 177m (580')
Parachute starts to open.
Fully open parachute.
Descending under parachute. Look back
towards Penrith.
More trees and buildings near the launch
site.
Assessing the booster for damage during
landing. It was just fine.
More water. We add the food colouring for
better photos.
Some kind of very technical discussions ....
probably what we are going to have for lunch.
A fuzzy image taken from video showing the
start of the air pulse.
Just after separation the white line is the
sustainer foam trail. White dot in the middle is
the booster.
Booster coming in for a safe landing.
More water of course. The grass was well
watered after three launches.
Locking the sustainer into place with
special hooks.
The step ladder comes in handy when
launching water rockets. Ground to tip is 2.36m.
Dad took this photo as he pulled the string.
Acceleron IIIb hits top speed as the water
runs out.
... and back to Earth safely.
Date:29thJuly
2007 10:30am - 1:00 pm
Location:Quakers Hill
Conditions:Cool and
partly cloudy, calm winds.14 degrees
C.
Rockets:
(click the name for rocket details)
An upgraded sustainer that
provides better support during
liftoff.
Team Members at
Event:
GK, PK, AK,
IK, HK, Jordan K, John K and Paul K.
Today was an fantastic launch day with
very little wind and mild temperatures. We
had the whole family come out and watch and give
us a hand as we were going to fly the new
Acceleron IIIb booster and Tachyon sustainer for the first time.
We ended up flying the booster and
sustainer three times. It takes
about an hour to set up camp and get ready
for the first launch and then it is around
30 minutes to get the next launch ready
again. We were really happy with the
performance of the rocket as it did exactly
what it was suppose to do.
Flight Day Events
The day started off really well
until on the way to the launch site
dad's engine oil light came on. It
looked like we needed to scrap the
launch day, but after a few checks and a
top up with oil, he nursed it to the
launch site. We had two cars full of
equipment.
From previous experience we knew
that setting up a big launch you tend to
forget things, and so this time we came
prepared with a page long check list
that needed to be followed before each
launch. This proved very useful and made
sure we had all the right bits attached
and set as needed.
We also brought a small step ladder so
that we could reach the flight computer
on the sustainer. The fully assembled
rocket is 2.36m (~8 feet) tall.
Flight 1
We used only about 100psi on the
first launch, to make sure the bottles
wouldn't fail. We wanted to get at least
one launch under our belt so we took
minimal risks. The parachute delay on
the booster was set at 2.75 seconds
after second stage release. Due to the
lower pressure and longer delay, the
booster's parachute fully opened only
about 1 meter above the ground, but it
was enough to stop the booster from
suffering any damage.
The take off was nice and slow and
mostly vertical, it looked like it was
taking forever to release the second
stage, but it finally did and it flew
off very nicely. It took 34.5 seconds
for it to land.
We also attached an upward facing
camera to the side of the booster so
that it could film the second stage
separating. However, when we got home, I
noticed it did not record anything. This
was disappointing, and now I am really
considering getting a new camera that
can record longer that the 30 seconds.
It wasn't a complete loss as we had two
hand held digital cameras filming as
well.
The only other hiccup was a stuck
return valve in the sustainer air
supply which started draining the
sustainer into the booster when we
locked it down. This was quickly fixed, but it
meant we had to refill the sustainer
with water and foam again.
Flight 2
We weren't going to fly any more cameras
on the day, but a last minute decision was
made to swap the mirror used on the booster
camera and put it on the second camera.
Since the sustainer wasn't designed to carry
a camera, we simply taped the camera to the
mid section of the rocket. This adds about
10% more weight to the rocket, as well as
adding considerable drag to the rocket.
We
also set the deploy delay for the booster
parachute to 2 seconds to open a little
sooner.
This time we pressurised the rocket to
110psi and launched it. You could see and
hear that it had more power than the
previous launch and took off faster. The
rocket flew mostly vertical and again the
second stage released right on queue. (That
TDD works a treat Trevor!)
The second stage took off like a bullet
and headed almost vertical. We used a 7mm nozzle on
the sustainer for all flights. The in-flight
video shows how it steered itself
vertically. Using the in-flight
video The best estimate of
altitude came to 177m (580 feet).
[See altitude estimates below] The
sustainer took 40.64 seconds to reach the
ground. This was our highest altitude to
date.
The booster's chute opened at a nice
altitude and so it landed well again.
Unfortunately the onboard video only
has 30 seconds of record time 15 of which
was taken up while still on the ground, but shows the
entire ascent, the chute deploying and descent
under parachute for a few
seconds. The launch was covered by two hand
held DV cameras and one static pad video
camera.
(If the video does not play, try the latest
Flash player from Macromedia)
A better quality version is available
here (37Mb)
Also available on MySpace
here.
Flight 3
As we prepared for the third launch,
we kind of winged it and forgot to follow the check
list procedure. We only realised once we
started pressurising the rocket that the
booster wasn't locked into the launcher.
At about 30-40psi the rocket popped up out
of the launcher about an inch and
proceeded to spray the booster water
everywhere. Due to the launcher setup the
rocket did not tip over and the guides
kept it in place.
The sustainer computer was already armed
and the little pop up was enough for it to
detect "launch" and popped the parachute
about 8 seconds later. The booster
computer was not armed and therefore did
not release the sustainer when the
pressure dropped to zero. We have to arm
the booster flight computer after it has
about 40 psi in it, enough for the
pressure switch to be securely
deactivated.
The problem was that we had a partially
pressurised sustainer on the launch pad
and a deployed parachute. We could have
manually launched it but we weren't sure
what would happen. So instead we
disconnected the non return valve and let
the sustainer drain through the air supply
line.
We refilled everything, locked it down
and launched it a third time with no
cameras and again at 110psi. The booster and
sustainer again performed really well, and
the sustainer took 50.36! seconds to come
back to earth. The estimated altitude was:
This flight set two new personal
records for flight time and altitude.
Altitude Estimates
Without an altimeter we have to try to
calculate how high our rockets go. (I know,
I know we have to get one). Normally we
don't publish how high they go in our
updates unless we have some reasonable way
of measuring the altitude.
On board video gives us this ability and
on today's flight #2 the camera took a
picture of a large area of asphalt (old
runway) directly below the rocket as it was
approaching apogee. We measured the asphalt
to be 33m wide. We then used a calibration
image taken from the same camera and using
the similar triangles method we calculated
the altitude for the second flight to be
~ 177m. (580 feet).
The third flight altitude estimate has a
greater margin of error because there was no
camera. However, we were still able to
get a reasonable estimate of altitude.
This is how we arrived at the altitude
estimation:
Flight 2 and 3 both used the same launch
pressure, same parachute deployment setting
and the same amount of water in the booster
and sustainer.
We used ground based video to get timing
information for total flight time and time
to separation, from launch. In flights
2 and 3 the time to separation was the same
at 2.24 seconds. This led us to
believe that the ascent profiles were
relatively similar.
The one big difference between flight 2
and 3 was the extra ~10 seconds of flight
time. Since most of the extra flight
time would have been under parachute, we
needed to know the rocket's descent rate.
This was calculated from flight #2. The
average descent rate was calculated by figuring out
how long the rocket fell under parachute and
over what altitude. Since it took 7.36
seconds to reach apogee - timing we got from
the onboard video. Also from the video we
know it took a further 2.4 seconds before
the parachute opened. Subtracting these from
the total flight time we know that the
rocket fell under parachute for ~31 seconds.
But before the parachute opened, the rocket
was in free fall from apogee for 2.4
seconds. Using simple acceleration due
to gravity calculation, we work out that the
rocket fell by ~28 meters in the 2.4
seconds. We neglect drag as this was
relatively low velocity.
Therefore, the altitude lost during
parachute descent was 177 - 28 = 149 meters.
This makes the descent rate 149 / 31 = ~4.8
m/s.
Now since the the rocket on flight 3 took
10 seconds longer to land, and assuming that
most of this 10 seconds was under parachute,
this gives us an extra altitude of about 48
meters. This, however, is highly
unlikely and we need to take into account
potential updrafts and slightly lower
descent rate due to the lower weight of the
rocket, as well as a little extra time to go
that little bit higher.
All things being equal the simulator
predicted that due to the lower weight and
drag (no camera), we should have gained an
extra 10 meters in altitude.
Therefore, instead of the extra 48 meters we
considered only a gain of 15 meters for this
flight giving a total of 192 meters (630
feet). This is our best estimate of
the altitude and is probably within +/-10
meters of the actual value.
Flight Record
Launch
Rocket
Pressure (PSI)
Notes
1
Tachyon II and
Acceleron IIIb
100
Sustainer: FC
setting 'b' 7mm nozzle and 800ml Foam
and water mix.
Booster: FC setting '3'. 1.5L per
segment. Camera on booster.
Slow take off, mostly vertical with a
great release of second stage. Both
landed well.
2
Tachyon II and
Acceleron IIIb
110
Sustainer: FC
setting 'b' 7mm nozzle and 800ml Foam
and water mix. Camera on sustainer.
Booster: FC setting '0'. 1.5L per
segment.
Excellent flight. Good deploys all
around.
3
Tachyon II and
Acceleron IIIb
110
Sustainer: FC
setting 'b' 7mm nozzle and 800ml Foam
and water mix. Booster: FC
setting '0'. 1.5L per segment.
Excellent flight again. Great deploys,
and our highest altitude to date at
~192 meters. Flight time 50.36
seconds.
Thoughts
This two stage rocket has been in
development for about seven months with
progressive complexity introduced along
the way and lots of trial flights. The
booster and sustainer together now have
around 400 individual components. We are
likely to put further development on the
back burner for now and concentrate on a
few other developments and experiments we
have been considering for a while but
haven't had time to do them.
When we fly this rocket again, it will
likely be a little lighter and also be
launched at 120psi, and hopefully with a
real altimeter.
Write your checklists, and FOLLOW
them.
Acknowledgements
Many thanks go to our family who have
supported and helped us along the way in
this fun hobby.
Also thanks goes to all the water
rocketeers out there that have contributed
with materials, design issues and insights
into how these things work.