This document describes a project to design and construct an experiment to rapidly resolidify ZBLAN glass samples in microgravity using Queensland University of Technology's drop tower facility. The experiment will use an infrared furnace to heat ZBLAN glass samples, which will then be rapidly ejected onto a copper cooling pad using a solenoid-triggered release mechanism. Numerical simulations and high-speed video analysis showed the samples could be ejected and cooled within 0.0439 seconds. The experiment aims to minimize crystal formation in ZBLAN glass by processing it in microgravity conditions using the drop tower.

1. Queensland University of Technology
The design/construction of a QUT
Drop Tower ZBLAN glass rapid
resolidification experiment
Justin Murusali
Mechanical Engineering
08637750
Ryan Miller
Electrical Engineering
08567042
Talara Johnston
Mechanical Engineering
08403783
Dr. Martin Castillo
Project Supervisor

2. Queensland University of Technology
Outline
• Introduction to ZBLAN glass
• QUT Drop Tower
• System Overview
• System Components
• Conclusion
• Questions

3. Queensland University of Technology
ZBLAN Glass - Introduction
• ZBLAN glass has the theoretical lowest attenuation loss
out of all solid fill fibre materials
• Theoretically predicted attenuation loss of 0.001 dB/km,
much lower than current silica fibres of 0.15 dB/km
• ZBLAN refers to the mixture of Zirconium (Zr), Barium
(Ba), Lanthanum (La), Aluminum (Al), Sodium (Na)
Fluoride materials

4. Queensland University of Technology
ZBLAN Glass Applications - Introduction
Potential applications of ZBLAN glass include fibre
amplifiers, fibre optic gyroscopes, delivery systems
for laser cutting, drilling and surgery, radiation
resistant data links, nonlinear optical systems, and
ultra-low-loss repeater-less transcontinental
and transoceanic optical fibre.

5. Queensland University of Technology
ZBLAN Glass in Microgravity
• The optical properties of ZBLAN degrade during the fibre
drawing process due to the undesired crystal formation.
• Gravity-driven density segregation is the major cause for
viscoelastic shearing between the heavy particles causing
crystallization
• The use of microgravity in the synthesis of ZBLAN glass
will minimise crystal formation thus improving optical
characteristics due to the suppression of buoyancy and
viscoelastic shear.

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QUT Microgravity Facility
• The QUT Drop Tower is
the only free-fall induced
microgravity facility in the
Southern Hemisphere
• Drop Tower corridor is
21.3 meters high
• Provides free fall time of
~2.1 seconds

7. Queensland University of Technology
System Overview
Trigger
3 lever mechanical trigger
system used to release the
rod when the solenoid is
activated
Trigger Circuit
Transistor used as a
switch so that when
2 connected wires
are cut it activates
the solenoid
causing the rod to
fall.
Latching Mechanism
This prevents locks the rod
in the final position micro-
gravity.
Infrared furnace
Is able to heat samples up
to 3000°C/s.
Platform
Accommodate and protect
the other system
components and guide rod
Copper cooling pad
To quench sample at
a rate of 1000°C /s.

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• The platform is one of the fundamental
components of the system.
• It was design to with stand a force up
60G (588.6N)
• The main purpose of this structure is to
accommodate and protect the IR
furnace and for use in the
guidance/trigger system to eject the
ZBLAN glass from the furnace rapidly
• Constructed from aluminium alloy
(6061-T6)
The Platform

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• A diagonal member was
added to the vertical
F-shape frame to increase
rigidity of the structure.
• The rectangular base was
replaced with a plate twice
as thick as the initial plate
to increase stiffness.
The Platform Structure
Changes from initial version
Before
After

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The Solenoid Circuit
• DC circuit was created to power the solenoid, which acts as an
actuator to release the rod when the capacitor releases its stored voltage
• Runs on eight 1.5V AA batteries connected in series to produce 12V.
• Diode (D2) protects circuit from incorrect battery polarity, allowing the
current to flow in intended direction only.
• LED (D1) indicates power on via S1 on/off switch, R3 limits LED to 2V
which is what it can only handle.

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The Solenoid Circuit
• 2200µF capacitor charges through R4 and Solenoid (L1)
• Field effect transistor (FET) held off while two connected terminals (X1-
1 & X1-2) are shorted by wire
• Capacitor stores just under 12V, discharges when the circuit is cut, as
the FET conducts heavily
• Resistors R1 & R2 form a voltage divider, dissipating 6V each when the
circuit is switched off rather than opened.

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The Solenoid Circuit
Drop Wire
• Circuit will be connected to the
Drop Wire when placed in the drag
shield.
• This will allow the solenoid to
release the rod instantaneously
alongside the falling experiment,
when the drop wire is cut.

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The Solenoid Circuit
Capacitor Charge Over Time
• The 2200µF capacitor takes
26.4 secs to reach full charge
(Time constant of 5.28 s)
• Found using the formula:
t = C*R
= 2200 * 10^-6 * 2400
= 5.28 s
5.28 * 5 = 26.4 s
•Instantaneously discharges
voltage to solenoid when the
circuit is cut

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The Solenoid Circuit
Capacitor Discharge Over Time
• When the shorted circuit is
switched off rather than opened
capacitor discharges over time
•Takes much longer than to
charge
• At 37% of it’s final voltage, the
capacitor will be at 1 time
constant:
12 * 0.37 = 4.44V
Discharges to 4.44V at 13
seconds (approx.)
13 * 5 = 65 seconds approx.
to reach 0V

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Release Mechanism
• The release mechanism is designed to hold
the glass vial inside the furnace while heating.
• The solenoid is attached to a system of levers
that that hold the rod in place by latching on to
a notch in the rod
• While in this position the springs on the rod are
in compression storing potential energy to
eject the rod when released

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Release Mechanism
• Once the ZBLAN sample is heated the
solenoid is activated and pulls in, this
releases the levers from the rod.
• The force in the springs eject the rod
downwards until it latches in place at
the bottom. This holds the sample in
place on the copper cooling pad for
rapid quenching in microgravity.

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Release Mechanism
Hooke’s Law
F = -kX
k is a constant (characteristic of the spring)
X is the distance the spring is being stretched
or compressed
Ejection force of the spring

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Release Mechanism
For the springs used k = 0.61 N/mm
F= -kX = -(0.61 N/mm).(-57 mm)
F= 34.77 N
∆X = X2-X1
∆X = 53 mm-
110 mm
∆X = -57 mm

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Release Mechanism
Original Design
In the original design the
34.77 N of force from the
spring was acting
downwards in the y direction
directly on to the solenoid
causing too much friction for
the solenoid to release
when triggered.

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Release Mechanism – Solenoid Trigger
Improved Design
• A new trigger design was
made with 3 levers.
• The levers reduce the
force acting on the
solenoid from 34.77 N to
0.0245 N
• That’s a reduction of
99.93%!!

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Release Mechanism
t = 0.0133 st = 0 t = 0.0033 s t = 0.0067 s t = 0.0100 s
t = 0.0167 s t = 0.0200 s t = 0.0233 s t = 0.0267 s t = 0.0300 s
t = 0.0333 s t = 0.0367 s t = 0.0400 s t = 0.0433 s t = 0.0467 s
Images from high speed camera showed the time taken from when the rod
is ejected until it reaches the copper plate is between 0.0433 and 0.0467
seconds

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Release Mechanism
Closer look
Constant Velocity
Acceleration
Deceleration
The movement of the rod goes through 3 stages

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Release Mechanism
Closer look
y = 3654x – 28.837
R2
= 0.99372
y = 129.17
Lines intercept at
X = 0.0439 s

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Release Mechanism
• Analysing images from the high speed video
concluded that the ZBLAN sample will be ejected
from the IR Furnace and reach the copper cooling
pad in 0.0439 s
• This represents the time that the ZBLAN glass
sample begins its complex cooling process. This
information will be vital when it comes to modeling
the rapid cooling phenomena of the ZBLAN glass.

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Conclusion
• The trigger circuit was constructed to create a relay switch to activate a
solenoid
• The capacitor reaches it’s full charge at 26.4 s
• The capacitor discharged <11.7×10-3
s
• The unloaded discharge take ~65 s to reach 0 V
• The stress analysis showed that the diagonal support rods needed to
be implemented into the platform so it wouldn’t fail from fatigue
• Using calculations and high speed video it was found that the rod ejects
the ZBLAN sample from the furnace with 34.77N of force to reach the
cooling pad in 0.0439 seconds in unit gravity

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Future Work
• Experiments will be conducted to see if undesired
crystallization occurs in 0.0439 seconds in low gravity and
unit gravity conditions
• Synthesizing ZBLAN glass
• Using these QUT Drop Tower designs to aid in the design
of a payload for the United States Air Force suborbital
satellite

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Thank you for listening
A special thanks to Dr. Martin Castillo
and David Kabelele

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Drag Shield and inner experimental rack
Drop Wire
Experimental
Rack
Drag Shield

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30. Queensland University of Technology
ZBLAN Glass in Microravity
ZBLAN fibre processed at unit
gravity
ZBLAN fibre processed in micro
gravity
Comparison images from the published work of Dennis Tucker in 2004 show
the difference in crystallisation of ZBLAN at unit gravity and micro gravity.

31. Queensland University of Technology
Von Mises stress

32. Queensland University of Technology