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represents a launch or test day, and describes the
events that took place.
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Day 38 -
Tachyon Test Flights
Setting up in the cold and windy conditions.
Just before Tachyon's maiden flight. The
parachute is not packed yet.
Quite a bit of water goes upwards during
Start of air-pulse.
Quick repairs with a gaffer tape to
re-attach the launch detect switch, and the rocket is ready
to go again.
Second launch was closer to vertical, but
the strong breeze still made it fly down range
quite a ways.
You can get an idea from the inflated
parachute at the strength of the wind.
The last launch and flight were almost
identical to launch #2.
2007 7:15am -
Denzil Joyce Oval
Conditions:Cold (6 degrees C)
20km/h wind, clear skies.
(click the name for rocket details)
A new rocket designed
specifically as a sustainer to work
with the Acceleron III booster.
Team Members at
GK and PK
Finally after 3 weeks of not being able
to launch due to bad weather, we were able
to get out for a few launches to test the
sustainer. It was less than ideal flight
weather, but we had a go anyway.
We were only launching the Tachyon sustainer on
this day to evaluate its performance,
dynamic stability, its new flight computer and
the new parachute deployment mechanism.
Flight Day Events
The sustainer was filled with 800ml of
water, pressurised to 120psi and given a
7mm nozzle to simulate the sort of flight
conditions it is going to encounter when
its released from the booster. Because we
were launching it as a single stage, the
slightly larger nozzle and less water were
used to get the rocket up to speed. 1000ml
and 5mm nozzle will be used for actual
Soon after its first launch the rocket
angled over significantly and headed over
to the river. It appeared to be a little
unstable during the thrust phase - most likely
because of the fins being so far forward.
After the thrust phase the rocket flew
nice and straight.
When it passed through apogee and kept
heading towards the ground, and looking like
we were going home early, the chute opened
about 10 meters above the ground. - A
close shave. The delay I set for the
deploy was for 4.75 seconds, obviously a
little too long. The deploy delay does not
mean the time to when the chute opens, rather
when the door latch starts opening. It
takes a further .36 seconds for the packed
chute to clear the door, and probably
another 1 - 1.5 seconds to fully open.
This timing is consistent with what we
observed in the video.
The late chute deploy actually worked
in our favour for two reasons:
1) Had it opened at normal altitude, the
rocket would have drifted either into the
trees or the river; and
2) It tested the deploy mechanism,
parachute attachment and parachute at high
speed. This is going to be important once
we fly it on the booster.
After inspecting the rocket post
landing we noticed that the payload
section had moved slightly in the nosecone
and that the straw and nail of the launch
detect switch had separated from the PCB.
A quick repair with a piece of gaffer tape
fixed it up.
On the second launch we put some
washing detergent in ( we ran out of
bubble bath) and set the rocket up for Jet
Foaming. We also set the time delay on the
flight computer to 3.75 seconds and
pressurised it to 130 psi because foam
produces lower thrust on take off.
The rocket flew quite straight up and the
parachute opened right around apogee.
The rocket drifted down range about 180
meters. Luckily the wind blew in the right
direction otherwise it would have gone
across the road.
The third launch was almost identical,
although the rocket again took off at a
bit of an angle. The drift due to the wind
under parachute was again very
We decided to call it a day when the
wind started picking up and people started
arriving for soccer.
(If the video does not play, try the latest
Flash player from Macromedia)
We were very happy with the performance
of the sustainer, and although there was
some dynamic instability during the thrust
phase, we believe this will be reduced due
to the speed it will already be travelling
when it is released from the booster.
The angled take-offs were likely
helped by the strong wind.
The payload section will need to be
secured better to prevent it from moving
inside the rocket
A small change will be made to the flight
software to position the servo to the
correct position when it is turned on.
We are going to paint it darker colours,
and put reflective stickers on it.
From what we saw on the video, the rocket will
be very difficult to see and track when it
Other than that, the sustainer should be
ready to go for the two stage rocket.
7mm nozzle, 800ml water,
"7" setting on FC. Rocket flew off at an
angle, and deployed parachute very late.
Landed well. Launch detect switch nail
and straw broke off.
7mm nozzle, 800ml water,
detergent, "3" setting on the FC. Water
set up for Jet Foaming. Rocket flew
relatively vertical and quite high,
parachute deployed right around apogee.
Drifted a long way from launch pad.
Moved launch pad, 7mm
nozzle, 800ml of water, "3" setting on
the FC, detergent and water set up for
Jet Foaming. Parachute deployed slightly
after apogee. Rocket drifted a long way