FUEL CELL POWERED UNMANNED AERIAL VEHICLE
MAE-435W
APRIL 21ST, 2015
Advisors:
Dr. Ayodeji Demuren, Dr. Xiaoyu Zhang
MAE Students:
Timothy Bernadowski, Michael Beyrodt, Samuel Brooks, Josiah Hopkins,
Brian Johnson, Brandon Snyder, Ryan Turner
MET Students:
Edward Hubert, Dylan Keen
TABLE OF CONTENTS
LIST OF FIGURES ........................................................................................................................ 4
LIST OF TABLES .......................................................................................................................... 4
1
ABSTRACT ............................................................................................................................ 5
2
INTRODUCTION ................................................................................................................... 6
3
METHODS ............................................................................................................................ 10
3.1
AIRFRAME ................................................................................................................................ 10
3.2
VEHICLE SUBSYSTEMS ......................................................................................................... 12
Flight Controls .................................................................................................................................... 12
Power system ...................................................................................................................................... 13
3.3
FUEL CELL................................................................................................................................ 15
Fuel Cell System ................................................................................................................................. 15
Hybrid System .................................................................................................................................... 17
3.4
RAIL ASSIST LAUNCH DEVICE (RALD) ............................................................................. 18
3.5
INTEGRATED FLIGHT TESTS ............................................................................................... 19
Preflight Tests ..................................................................................................................................... 19
Flight Modifications............................................................................................................................ 20
Repairs ................................................................................................................................................ 21
Concept ............................................................................................................................................... 22
4
RESULTS .............................................................................................................................. 24
4.1
AIRFRAME ................................................................................................................................ 24
4.2
VEHICLE SUBSYSTEMS ......................................................................................................... 24
4.3
FUEL CELL................................................................................................................................ 26
Fuel Cell System ................................................................................................................................. 26
Hybrid System .................................................................................................................................... 27
4.4
RAIL ASSIST LAUNCH DEVICE ............................................................................................ 28
4.5
INTEGRATED FLIGHT TESTS ............................................................................................... 28
5
DISCUSSION ........................................................................................................................ 30
6
CONCLUSIONS ................................................................................................................... 33
7
REFERENCES ...................................................................................................................... 34
APPENDIX 1: GANTT CHART.................................................................................................. 36
APPENDIX 2: BUDGET ............................................................................................................. 37
2
APPENDIX 3: COMPARISON OF DIFFERENT FUEL CELL TECHNOLOGIES ..................................... 40
APPENDIX 4: PROPELLER FULL THROTTLE TEST RESULTS .......................................... 41
APPENDIX 5: SYSTEM COMPONENTS BY MASS ............................................................... 42
3
LIST OF FIGURES
Figure 1: PEM Fuel Cell (Office of Energy Efficiency and Renewable Energy, Fuel Cell Technologies
Office) ........................................................................................................................................................... 7
Figure 2: Skua FPV (Hobby King) ............................................................................................................. 11
Figure 3: Airwing Talon Drone (Nitro Planes) ........................................................................................... 11
Figure 4: Skywalker X8 (Hobby King)....................................................................................................... 11
Figure 5: Assembled Skywalker X8 Airframe without Fuselage Lid ......................................................... 11
Figure 6: Center of Gravity Measuring Device........................................................................................... 12
Figure 7: eCalc Calculations ....................................................................................................................... 13
Figure 8: 12x8 Propeller Test Current and Voltage Curves vs Time .......................................................... 14
Figure 9: ODU Wind Tunnel Test .............................................................................................................. 14
Figure 10: Hydrostik Fuel Storage (Fuel Cell Store) .................................................................................. 16
Figure 11: Fuel Cell Test Setup .................................................................................................................. 16
Figure 12: Direct Fill System ...................................................................................................................... 17
Figure 13: Layout of the Fuel Cell Hybrid System ..................................................................................... 17
Figure 14: Electrical Schematic of the Hybrid System ............................................................................... 18
Figure 15: Hand Launching ........................................................................................................................ 18
Figure 16: RALD, Fully Assembled with Airframe ................................................................................... 18
Figure 17: From Left to Right: UAV 1 - Frankenplane, UAV 2 – Newbie, & UAV 3 - Womb ................ 22
Figure 18: UAV Battery Powered Flight .................................................................................................... 22
Figure 19: Current and Power Draw Curves for Different Propellers during Full Throttle Tests .............. 24
Figure 20: Wind Tunnel Tests .................................................................................................................... 25
Figure 21: Current vs Time for Different Hydrostik Configurations .......................................................... 26
Figure 22: Power vs Current Curves (Hybrid System - left, Horizon Technologies Fuel Cell – right
(Horizon Fuel Cell Technologies)) ............................................................................................................. 27
Figure 23: Using a Tarp to Catch the UAV during Attempted Takeoff ..................................................... 32
Figure 24: Voltage Curves for Different Propellers .................................................................................... 41
Figure 25: Current Curves for Different Propellers .................................................................................... 41
Figure 26: Effects of Propeller Size on Motor Speed ................................................................................. 41
Figure 27: Power Curves for Different Propellers ...................................................................................... 41
LIST OF TABLES
Table 1: Comparison of Fuel Cell Technologies (U.S. Department of Energy)........................... 40
4
1
ABSTRACT
Unmanned aerial vehicles (UAVs) are being used more and more frequently by the
United States Military as a low cost, low risk option to manned flight. Standard battery power
does not ensure a UAV flight time long enough for many missions making power option
research necessary if flight time is to be increased. Fuel cells are of particular interest because of
their potential to improve the long-range flight performance of small scale electric unmanned
aerial vehicles. To address the scarcity of relevant data, and to serve as a proof of concept, a
commercially available airframe was designed to be retrofitted with a fuel cell based propulsion
system. Components of the system were selected based on a number of interrelated parameters
including flight endurance, system weight, propulsion efficiency, and aerodynamics.
The
Skywalker X8 delta wing airframe was chosen for its ability to carry large load and large
fuselage. The Horizon H-100 Watt Hydrogen fuel cell was chosen because of its light weight
profile and ability to provide significant power to the motor. The Hydrogen fuel storage system
consisted of several Horizon Hydrostik containers working in parallel. Work on the airframe and
the propulsion subsystems took place concurrently in an effort to identify and resolve any issues
while the project development was still flexible. Fuel cell performance was studied and analyzed
and a battery-fuel cell hybrid system was built in an effort to ensure proper power supply to the
motor during cruising as well as peak power demand during takeoff. The final stage of the
project consisted of flight testing and the attempted integration of the fuel cell/battery powered
UAV as a whole.
5
2
INTRODUCTION
Unmanned aerial vehicles (UAVs) are becoming an increasingly prevalent technology,
and can be implemented in a variety of commercial and military applications. Unfortunately,
between the high power draw of motors and technical data sensors, many small UAVs cannot fly
more than 30 minutes on conventional battery power, often requiring recharging or a second set
of batteries in order to function properly throughout the mission [1]. Traditionally, low
speed/low altitude small UAVs are powered by a lithium polymer battery. The flight endurance
of these vehicles is limited by the battery’s ability to endure the power draw [2]. The need for
longer lasting power in UAVs can be addressed through examining fuel cells as an alternative
power source.
Proper operation of the vehicle subsystems is the first challenge to be addressed in order
to commence the venture of sustained flight of a UAV. The vehicle subsystems includes the
aircraft’s propulsion/power system and flight controls. The propulsion system of a UAV consists
of an energy source, electric motor, and propeller [3]. For remote controlled aviation, the power
system encompasses the propulsion system and Electric Speed Controller (ESC). Flight controls
include remote controller, receiver, and servomotors (servos).
Once proper operation of the vehicle subsystem is sustained, the next challenge is optimal
power output. As the UAV’s All Up Weight (AUW) increases, additional thrust is necessary.
Propeller pitch and diameter are critical specifications in the production of thrust. In order for
effective propeller selection, static and dynamic thrust must be evaluated. Incorrect electrical
connections and or insufficient propulsion can lead to destruction of internal components and
airframe making analysis of the power system and flight controls for satisfaction of component
supply needs and vehicle thrust demands a required step in UAV system design.
6
The integration of fuel cell power supply to UAVs provides a way to accomplish longer
flight time. Critical factors for flight endurance for UAVs are power source and weight. Fuel
cells allow generation of power at a controllable and constant rate. They run as long as fuel is
present and produce power at a rate controlled by the fuel supply and fuel cell controller. There
are several different types of fuel cells including polymer exchange membrane fuel cells, solid
oxide fuel cells, alkaline fuel cells, phosphoric acid fuel cells, and molten carbonate fuel cells (a
comparison of these types can be found in APPENDIX 3 (COMPARISON OF FUEL CELL
TECHNOLOGIES). For UAV power supply application, polymer exchange membrane fuel
cells (PEMFCs) are ideal because they are air cooled by an onboard fan and operate at low
temperatures [4]. PEMFCs use gaseous Hydrogen as fuel, along with Oxygen from the air. The
fuel is easily obtainable or can be produced in chemical reactions if pure Hydrogen is
unavailable [5, 6].
Several
design
considerations
such
as
cost,
operating temperature, and weight ultimately resulted in
selection of the polymer electrolyte membrane (PEM)
Hydrogen fuel cell (Figure 1), primarily using the Table
found in APPENDIX 3 (COMPARISON OF FUEL
CELL TECHNOLOGIES). Availability of Hydrogen fuel
cell test equipment in the lab was also a contributing factor.
Polymer electrolyte membrane fuel cells (PEMFCs)
operate by a chemical reaction between Hydrogen and
Figure 1: PEM Fuel Cell (Office of Energy
Efficiency and Renewable Energy, Fuel Cell
Technologies Office)
Oxygen to produce electrical current between a cathode and an anode (seen in the chemical
equations below).
7
Simplified Reaction:
𝐻2 + 12𝑂2 → 𝐻2 𝑂 (2-1)
Anode Reaction:
𝐻2 → 2𝐻 + + 2𝑒 − (2-2)
Cathode Reaction:
𝑂2 + 2𝐻 + + 2𝑒 − → 𝐻2 𝑂 (2-3)
1
2
These equations show that the PEM Fuel Cell can generate electricity with just Hydrogen
fuel and air with the only exhaust products being water vapor. It is a clean, sustainable source of
energy that can run smoothly and generate power for longer times than a battery can sustain.
There are several design considerations when implementing a fuel cell into a UAV, such
as peak power demand, Hydrogen storage, and weight distribution shifting the center of gravity.
The most favorable design method is to design the fuel cell system and the airframe
simultaneously [6, 7]. The long lasting performance of the fuel cell and propulsion system
(running until it is out of Hydrogen fuel) can be optimized with the airframe to produce a UAV
with increased flight endurance [8].
The power demand of UAV propulsion systems fluctuates similar to a traditional flight
vehicle. Hybridizing the propulsion system with a small conventional battery in a parallel circuit
allows for a smaller, less expensive fuel cell. Working together, the fuel cell and battery help the
UAV address power fluctuations from peak demands experienced at takeoff and landing, with
the fuel cell recharging the battery when under low demand when cruising [5, 9]. Fuel cells have
a higher energy density than many conventional batteries but the support systems required to
8
keep the cell stable and functioning properly increase the total weight. In a flight vehicle, size
and weight are critical because these can shift the center of gravity, affecting lift and
maneuverability. The smaller the size of the UAV the more important shifts in the center of
gravity become. For fuel cells to be successfully incorporated into UAVs, an airframe has to be
selected that has high lift and payload capacity with a low power requirement.
Generally, most of the weight in a fuel cell system, which is a big concern when
optimizing the system for a UAV, comes from the fuel (in the case of this study, the extra weight
of the hybrid system was the critical factor) [5]. This means that the onboard fuel must be
minimized in a flight application, so that the UAV’s payload is not maxed out. The fuel storage
must also be portable and easily manipulated in order to maintain the airframe’s required center
of gravity. Because of this importance, finding effective and minimized fuel storage options was
crucial in this project.
Fuel cells can provide the constant, long-term power needed by long distance UAVs and
can be incorporated into a UAV’s subsystems [5, 6]. The lack of designs and experimental data
involving the implementation of fuel cells with aircrafts calls for more research [10, 11].
Therefore, the purpose of this project was to retrofit an UAV’s airframe with a hybrid fuel cell
based propulsion system.
9
3
METHODS
In order to complete this project, the team split into four different groups, each focusing
on a specific section of the project. One team focused on the airframe, research, purchasing, and
construction as well as any center of gravity testing and material strengthening. Another team
focused on vehicle subsystems and optimization. A third team focused on the fuel cell and
hybrid power system. A fourth team focused on the design and creation of a launch device to
ensure safe UAV takeoff. Finally, the teams got together for flight tests and integration of
systems.
3.1
AIRFRAME
The objective of the Airframe subgroup is to research, purchase, and construct a
commercially available airframe (originally meant for battery powered operation) that is able to
fly while carrying the load of a fuel cell system.
The team narrowed down the airframes selection based on certain criteria. These criteria
included but was not limited to: (1) the airframe must be able to withstand a flight longer than 15
minutes, (2) it must be able to carry a cargo weight of 2Kg (the fuel cell system), and (3) the
airframe preferably should be easily modifiable with a relatively large fuselage space to allow for
relatively unobtrusive integration of the fuel cell system.
The three airframes brought before the entire group by the Airframe team for discussion
were; the “Skua”, the “Talon”, and “Skywalker X8“. The Skua was explored as an option
because of the carrying capacity and the simplicity of its modifications (Figure 2). The Talon
was brought to the table because of the high wing mount and large wing design allowing for a
massive amount of lift at low speeds with a very stable flight (Figure 3). The third model
seriously considered was the Skywalker X8 (Figure 4), which contained a relatively large cabin
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space as well as having a propeller in the back of the airframe which in turn provides more force
than a front propeller base model (push vs pull concept).
4Figure 2: Skua FPV (Hobby King)
4Figure 3: Airwing Talon Drone (Nitro Planes)
Figure 4: Skywalker X8 (Hobby King)
The team unanimously chose the “Skywalker X8” for its large payload rating (3,500 all
up weight) and large wingspan providing ample lift given the additional weight. It also had a
large fuselage, enough room in the cabin space to fit the fuel cell system without modifications.
The team reviewed previous experiments in which the Skywalker X8 was used and was
impressed with its performance.
Three identical, yet separate airframes of Skywalker X8 were ordered and were delivered
on February 24th, 2015 with intention of one being integrated with the fuel cell system, one being
dedicated to pre-fuel cell system testing, and a third as a backup in case of material failure either
during construction or testing.
powered
UAV
was
tested
A battery
with
mock
weight/storage space of the actual fuel cell
system.
One of the three airframes was
assembled on March 1st, 2015, another was
assembled April 1st, 2015, and the third
airframe was assembled on April 17th, 2015.
Figure 5: Assembled Skywalker X8 Airframe without Fuselage Lid
11
Before each flight test, the center of gravity
was measured using the center of gravity balancing
device (Figure 6).
Before
flight
testing
was
conducted,
strengthening options were researched to increase
the durability of the Styrofoam Skywalker X8
Figure 6: Center of Gravity Measuring Device
airframe. The method of choice was a hardening
tape that is used in casting broken bones. The first attempt in applying this tape on the plane, it
didn’t stick; the adhesive properties were not strong enough for it to hold to the bottom of the
UAV. At this point, the decision was made to use tape in spots that need more support, with duct
tape, electrical tape, and packing tape being applied due to their high availability and ease of use.
3.2
VEHICLE SUBSYSTEMS
The components that get a UAV off the ground (e.g. motor, propeller, controller, pilot)
were the responsibility of the Vehicle Subsystems Team.
Flight Controls
The Spektrum DX6 remote control system was chosen to allow for the maximum number
of channels necessary for safe flight upgradability and for the programmability. Spektrum
programming of control switch disengages the throttle input to act as a safety interlock. DX6
Delta Wing Configuration programming of the servos allows for the wings in a delta wing design
to simultaneously behave as elevator and aileron (commonly referred to as elevon). The UAV’s
two Futaba S3400 servo’s amp draw was found to comply with the ESC’s maximum current and
was verified through pre-flight elevon actuation and multiple test flights without electrical,
mechanical or structural failure. The channels necessary for Delta wing flight, throttle, elevator
and aileron, proved to be operational before each launch.
12
Power system
The electric power plant was selected based upon compatibility with linked electrical
components and incorporated four main stages. Product screening in a hierarchy manner from
motor, to ESC, to battery, allowed for the selection of consistent equipment. A brushless motor,
with the ability to supply 800 watts to an UAV with an AUW of 3.5 kg, was procured. An ESC,
with the ability to supply the brushless motor’s peak current draw of 60 amps, was placed
between the motor and power source. A lightweight Lithium Polymer battery, with a peak
current discharge of 200 amps, was chosen to complete stage one: procurement of the batterypowered UAV model’s power plant.
Results from the first stage (power plant selection) were compiled via eCalc software
(Markus Mueller, Switzerland), in order to commence the second stage: propeller selection.
Through the eCalc software, it was estimated that the 12X8 inch propeller would produce a static
thrust of 2210 grams +/- 10%. The thrust to weight ratio was inspected at the vehicles maximum
predicted load.
13
Figure 7: eCalc Calculations
The third stage for the electric power plant concerned assembly and ground test of stage
one and two selected components. The ESC, motor, battery and propeller was stripped, soldered,
heat shrink applied and or adapted to mate with one another for full-throttle performance. The
propulsion system with a 12X8 inch propeller was tested at maximum power for 60 seconds and
throttled down for 10 seconds, with a through a fully charged 12.6 volt LiPo battery.
Figure 8: 12x8 Propeller Test Current and Voltage Curves vs Time
The data represented above in Figure 8, show that the 12X8 inch propeller results in a
current draw ~50% below that of the motor’s rated continuous current of 42 Amperes.
In order to relieve the lack of power drawn and maximize
thrust, the fourth stage (propeller optimization) commenced. In order
to provide an optimal power system balance, the fourth stage required
that further ground tests (similar to the one described above) be
coupled with wind tunnel analysis for multiple sizes of propellers.
The selection of a 13X10 inch and 14X10 inch propeller for
further ground and wind tunnel test was supported by an Old
Dominion University Design of Experiments Wind Tunnel Test
14
Figure 9: ODU Wind Tunnel Test
(Figure 9), which showed a correlation between increased thrust and increased pitch (see section
4.2 for results). In order to maintain an adequate thrust to weight ratio, larger pitch and diameter
propellers were tested in the wind tunnel for 30 seconds at full throttle and in the ground tests at
60 second full throttle, 10 second throttle down described above for the 12X8 propeller.
3.3
FUEL CELL
Fuel Cell System
Initial PEMFC experiments were conducted using the Heliocentris Fuel Cell Trainer
(Heliocentris, Berlin, Germany) and its accompanying software. There are several instructional
experiments designed for students to test the fuel cell stack’s operation under varying conditions
such as fan speed (varying both oxygen supply and temperature), flow rate, and resistance. They
are designed so that a short experiment is done on the fuel cell stack, experimental data is
collected, and then a brief analysis of that data can be performed. All of these experiments were
conducted on the 40 Watt fuel cell included with the system.
Horizon Fuel Cell Technologies (Horizon, Singapore, Malaysia) was selected as the
manufacturer of the fuel cell. They have a selection of PEM fuel cell stacks with a range of
outputs and are light weight, making them ideal for flight.
These light weight fuel cells
(aerostacks) are ideal for the application of this project. However, the cost is prohibitive with the
budget of this project. The heavier H-cell PEMFC stacks are significantly cheaper and slightly
heavier. A 100 Watt H-cell fuel cell was selected for use in this project.
Fuel storage was another design consideration due to weight and volume. 3-D printing
was considered for a customized fuel tank which would be optimized for our design. However,
pressure in the tank was a safety concern. Light weight fuel tanks which would be ideal for this
project are available but they are significantly more expensive than much heavier ones that
would prohibit flight.
Horizon Fuel Cell Technologies has small Hydrogen tanks called
15
Hydrostiks (Figure 10) that are light in weight (100g) and store
Hydrogen at very high pressure making them compact, a key feature
when integrating the fuel cell system into the UAV. The fuel cell
requires 1.3 L/min of Hydrogen flow and each Hydrostik supplies 0.30.5 L/min. Running several Hydrostiks in parallel with each other is a
Figure 10: Hydrostik Fuel
Storage (Fuel Cell Store)
functional solution which meets the budget limitations.
Two types of fuel cell tests were conducted, constant voltage tests and variable voltage
tests. In the variable voltage tests (which were tried first), the fuel cell was tested at different
voltage levels starting at the operating 18 Volts and coming down to the motor’s operating
voltage of 12 Volts and logging the performance. This was the first test attempted with the fuel
cell which was conducted on April 1st, 2015. In constant voltage tests, the fuel cell was tested
with varying amounts of fuel at 12 Volts output and performance was logged over time.
Figure 11: Fuel Cell Test Setup
16
Volume of Hydrogen Required:
𝐿
𝑉̇𝐻2 (𝑚𝑖𝑛) × 𝑅𝑢𝑛 𝑚𝑖𝑛𝑢𝑡𝑒𝑠 = 𝑉𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 ℎ𝑦𝑑𝑟𝑜𝑔𝑒𝑛 𝑟𝑒𝑞𝑢𝑖𝑟𝑒𝑑 (3-1)
In order to fill the Hydrostiks faster than their included Hydrofill system (which took 8
hours on average to fill one Hydrostik) a direct fill system was designed and put together which
lead to the Hydrostiks being able to be refilled in less than 15
minutes, just over 3% of the original fill time.
Hybrid System
Since the fuel cell was able to outlast the battery, the battery
drain is considered the limiting factor on maximizing flight duration.
The hybrid system was set up with the 3S Lipo Battery powering the
fuel cell controller and the motor simultaneously with the fuel cell
wired to supply power to the motor in parallel. Load box tests were
conducted with this system. Then a 2 battery hybrid system was set
up and tested with the load box. In this scenario, one 3S Lipo battery
Figure 12: Direct Fill System
was powering the fuel cell controller while another
powered the motor in parallel with the fuel cell. Load box
tests were then conducted with the second iteration of the
hybrid power system, varying the voltage and measuring
the current output (results from these tests can be found in
section 4.3).
17
Figure 13: Layout of the Fuel Cell Hybrid System
3.4
RAIL ASSIST LAUNCH DEVICE
(RALD)
It was decided later on in the project that
due to the rear propulsion, a launch system was
needed to launch the UAV. It is typical for UAVs
to be hand launched in order to generate enough
momentum for takeoff. A substitution for hand
launching is a rail assist launch device (RALD).
The intended results were to increase safety
Figure 14: Electrical Schematic of the Hybrid System
standards, provide additional initial thrust, and to
receive consistent launch angle and initial thrust by
removing human error. The device operates by using a
cart/rail system which is placed under tension and then
released; proving the thrust needed to achieve flight. The
design was loosely based off of a previously existing
designs used for the Skywalker X-8 model, was
constructed of steel and aluminum, and designed to be
Figure 15: Hand Launching
collapsible for transport to the testing site.
The initial plans were based from studying the
previously existing design, and drew from the systems
general mechanics. Once that was complete a parts list
was constructed, and initial drawings made in Inventor
(Autodesk, San Rafael, CA). Availability of needed parts
Figure 16: RALD, Fully Assembled with Airframe
proved to be one of the main limiting factors, and the
18
design was modified accordingly. The rail consisted of two hollow square tubes that were
attached with clamps to provide easy deconstruction for portability. The insides of the ends that
were to be attached were installed with aluminum angles to act as supports. Once the two beams
were attached, they were rotated forty five degrees in order that the corners could act as the
track. Legs consisting of four smaller square tubes, two longer for the front and two shorter for
the back, were then attached to the main beam. The cart consisted of a U bar which was attached
to a base. This base consisted of eight bearings designed to slide over the top and bottom corners
of the main beam and were spaced apart to prevent any slippage occurring. The U bar was
designed to support the plane on either side of the fuselage while allowing clearance for the rear
propeller on takeoff. V bars were attached to the U bar to prevent premature lift while still
allowing the needed forward thrust. Latex tubing was used to provide the force needed for
takeoff, with one end anchored to the front of the beam and the other attached to the cart. At the
rear end of the beam a release mechanism was designed to be put in place which would allow the
cart to be locked into place and be released when needed. Locking the cart into place would put
the attached tubing under tension, which would then provide the initial thrust needed to achieve
flight when released. The tubing can also be adjusted to provide the appropriate thrust for
varying weight.
The RALD was brought to the first flight test day and was used for two-thirds of the
testing that day.
3.5
INTEGRATED FLIGHT TESTS
Preflight Tests
Flight tests with the battery powered system occurred on April 3rd, 7th, 11th, 17th, and 18th,
2015. Preflight tests went as such:
19
The wings were taped with an ‘X’ across the orange connector to better secure the wings
to the body (pulling from two directions rather than one) to create optimal security since the glue
melts in the warmer weather and loses its sticky qualities.
The plane’s center of gravity (CG) was centered so the nose of the plane is a bit heavier
than the tail, (CG found via testing to be located at about 1 foot back from the nose). This
provides for better control of the plane when flying and also keeps the plane from rising too
quickly and crashing hard as a direct result of the potential energy from the altitude.
Taping the motor to the engine mount was also done to create a “cheap fix” to withstand
multiple crash situations without causing major damages to rear of plane, motor, or propeller; the
idea was that the tape would tear instead of the prop breaking or damage being caused to the rear
of the plane, which was plastic and Styrofoam.
The motor was taped using half-strips,
approximately 4-6 inches in length, to pull over each of the four lobes on the motor base mount
to secure firmly.
Taping the lid or body cavity cover on was also done after multiple “pop-offs” during
extended flights and during crashes to keep the internal components all inside the plane to reduce
the chance of losing something. Velcro strips could be applied to the interior of the plane to
secure the lid instead of taping the exterior shut to reduce drag over the body.
Once all vehicle subsystems were online, the “elerons” and throttle were tested prior to
takeoff.
Flight Modifications
Launching the plane by hand can be very dangerous with a rear mounted prop, so followthrough is important to keep hands away from the blades as they pass over. Launching was
achieved by holding the plane with two fingers and thumb (index and middle finger at rear, ring
and pinky finger to one side and thumb on other side) in each of the finger pockets designed into
20
the aircraft belly with one hand. The other hand then pinched the underside of the nose for
stability during throttle up of prop.
The plane was launched at no more than 30 degrees to the horizontal but typically as
level as possible to reduce the chances of stalling the motor out. Launching into the wind also
provided us with more lift which was very important for the weighted tests for fuel cell weight or
“load”. In addition to launching into the wind, the pilot stood behind the launcher to establish
better control during takeoffs and again during landings for better perspective on roll and pitch of
the plane to land smoothly and level. The right wing was also marked with an easily noticeable
colored tape to better distinguish the direction of the plane during flights.
Repairs
Almost any damage the plane incurred during crashes and landings was fixable no matter
how bad the crash appeared to be. Packaging tape was found to be light and very strong in
tension to hold wings on and re-glue parts down, while the duct tape was stickier at times and
much more pliable for tight spaces and curves on the body. The duct tape must be brand name as
the knock off brands did not suffice and much more had to be applied for the same repair adding
weight. Additionally, super glue was also found to be very useful for smaller parts or things that
had much tighter tolerances; any glue or chemical added to the plane should be tested prior to
application, as Styrofoam melts when interacting with many chemical products and will damage
the plane beyond repair.
Planes were flown until they were no longer flyable after reconstruction. This was
usually due to damage of the wings and elerons. The body was then removed and used on a new
pair of wings in some cases.
Of the three planes one was almost completely destroyed
(Frankenplane) after learning to fly on it and multiple hard crashes. The second plane (Newbie)
attained much longer flights with a lot more control since it was almost new when first used.
21
The last plane (Womb) was reserved for fuel cell tests only for optimal control with a brand new
plane that remained in a box unbuilt for most of the testing period until the hybrid system was
ready.
Figure 17: From Left to Right: UAV 1 - Frankenplane, UAV 2 – Newbie, & UAV 3 - Womb
Concept
Flight testing began with the battery powered system which had a total All Up Weight
(AUW) of 900 grams. The UAV’s rated AUW is 3,500 grams. Due to airframe durability
constraints at the time of testing, mock weight was then added to simulate the full fuel cell
Figure 18: UAV Battery Powered Flight
22
system AUW of 3,020 grams. On a different testing day, mock weight was increased to the
second iteration of the hybrid system AUW of 3,470 grams.
23
4
RESULTS
4.1
AIRFRAME
The hard fiber tape was determined to be an ineffective way to strengthen the airframe
due to its inability to adhere to Styrofoam. The airframe selected was able to be assembled
successfully and was able to carry the weight of the battery powered system and the first iteration
of the hybrid fuel cell system but was unable to support the weight of the second iteration of the
hybrid system, with the weight of an additional battery.
4.2
VEHICLE SUBSYSTEMS
The 12X8 propellers (as mentioned earlier) drew about half the motor’s rated maximum
current. Results from ground and wind tunnel testing verified the results found during the
Design of Experiments and showed that the 14X10 inch propeller was able to draw a current
~7% above the motor’s 42 Amperes continuous current draw and ~25% below the motors
maximum burst current (Figure 19).
Figure 19: Current and Power Draw Curves for Different Propellers during Full Throttle Tests
24
The results from the wind tunnel tests
showed the thrust generated by each of the
propellers based on the freestream velocity of
the wind tunnel (Figure 20). From these tests,
there was a noticeable positive correlation
between propeller size and thrust generated.
Thus, the 14X10 inch propeller generated the
most thrust and would get the airframe into the
Figure 20: Wind Tunnel Tests
air easiest.
Using a 14X10 inch propeller, the margin between power drawn and the max power
before motor failure, showed to be the optimal power system setup. In addition, weight
management was accomplished, resulting in a final AUW for the battery-powered UAV model
of 1777 grams, 49% percent below the maximum AUW.
Vehicle Subsystem Total Weight:
𝐿𝑖𝑃𝑜 𝐵𝑎𝑡𝑡𝑒𝑟𝑦 + 𝑆𝑒𝑟𝑣𝑜𝑠 + 𝑀𝑜𝑡𝑜𝑟 + 𝑃𝑟𝑜𝑝𝑒𝑙𝑙𝑒𝑟 + 𝐴𝑑𝑎𝑝𝑡𝑜𝑟 + 𝐸𝑆𝐶 = 897.22 𝑔𝑟𝑎𝑚𝑠 (4-1)
Maximum Motor Power:
𝑃 = 𝐼 ∗ 𝑉 = (60 𝐴𝑚𝑝𝑠)(12.6 𝑉𝑜𝑙𝑡𝑠) = 756 𝑊𝑎𝑡𝑡𝑠 (4-2)
Battery Continuous Discharge:
𝐴𝑐𝑜𝑛𝑡𝑖𝑛𝑢𝑜𝑢𝑠 = 20 ∗ 𝐶𝑎𝑝𝑎𝑐𝑖𝑡𝑦 = 20 ∗ (
5000𝑚𝐴ℎ
)
1000 𝑚𝐴⁄𝐴
= 100 𝐴𝑚𝑝𝑠 (4-3)
Battery Maximum Discharge:
5000𝑚𝐴ℎ
𝐴𝑚𝑎𝑥 = 40 ∗ 𝐶𝑎𝑝𝑎𝑐𝑡𝑖𝑦 = 40 ∗ (1000 𝑚𝐴⁄𝐴) = 200 𝐴𝑚𝑝𝑠 (4-4)
25
Watt Hours:
5000𝑚𝑎ℎ
𝑊ℎ = 𝑁𝑜𝑚𝑖𝑎𝑙 𝑉𝑜𝑙𝑡𝑎𝑔𝑒 ∗ 𝐶𝑎𝑝𝑎𝑐𝑖𝑡𝑦 = (11.1 𝑣𝑜𝑙𝑡𝑠) (1000 𝑚𝐴⁄𝐴) = 55.5 𝑊𝑎𝑡𝑡 𝐻𝑜𝑢𝑟𝑠 (4-5)
Battery Life (Nominal Approximation based on 14x10 Propeller Performance):
𝐶𝑎𝑝𝑎𝑐𝑖𝑡𝑦∗60 𝑚𝑖𝑛𝑢𝑡𝑒𝑠
5𝐴ℎ∗60 𝑚𝑖𝑛
𝑀𝑖𝑛𝑢𝑡𝑒𝑠 = 𝑀𝑜𝑡𝑜𝑟 𝑀𝑎𝑥 𝐴𝑚𝑝 𝐷𝑟𝑎𝑤∗ ℎ𝑜𝑢𝑟 = 53.9 𝐴𝑚𝑝𝑠∗1ℎ = 5.57 𝑚𝑖𝑛𝑢𝑡𝑒𝑠 (4-6)
Equation 4-6 shows the minimum approximation of battery life based on continuous
maximum power draw from the 14X10 inch propeller is 5.57 minutes. This is a very short time
relative to mission length but should be extended by the fuel cell hybrid system.
4.3
FUEL CELL
Fuel Cell System
A maximum fuel cell power output of 164 Watts was recorded during load box tests. In
the timeframe 0-11 minutes, the fuel cell behaved in a transient state. During this time, the fuel
cell power output would fluctuate between peak current output and 0 Amps.
Figure 21: Current vs Time for Different Hydrostik Configurations
26
The current
decayed over time beyond the initial transient state, though the fuel cell operated in a steadier
state. The longest current over time test was recorded using a configuration of three Hydrostiks,
which supplied power for 63 minutes. To avoid starving the cell, the constant voltage tests
(displayed in Figure 21, above) were stopped before all Hydrostiks were emptied. Transient
behavior of the fuel cell is believed to be caused by the Hydrogen supply configuration. The
chemical reaction in the Hydrostiks between metal hydride and Hydrogen does not produce a
steady output flow and pressure. The multiple tube lines cause Hydrogen to flow with uneven
distribution. During fuel cell operation, one or more Hydrostiks were depleted of Hydrogen
while others continued to supply. At that point, the behavior of the fuel cell in the test changed
from transient to steady state.
Hybrid System
The hybrid power system components lessened much of the transient tendencies. The
battery in the hybrid system acted as a damper to supply steady output as the fuel cell output
rises and falls. Figure 22 represents the hybrid power system performance compared to the
known behavior of the fuel cell, provided by Horizon Technologies. A nearly linear PowerCurrent trend was recorded up to 26 Amperes with a relative maximum power of 283 Watts.
Figure 22: Power vs Current Curves (Hybrid System - left, Horizon Technologies Fuel Cell – right (Horizon Fuel Cell
Technologies))
27
Power draw from the hybrid system decayed beyond 26 Amperes. Comparing the hybrid system
performance in with the published Horizon H-100 fuel cell performance, the hybrid system
achieved a greater power draw. The primary source for power in the hybrid power system is the
fuel cell. It acts to charge the battery above 12 volts. The battery is the secondary power source
and only provides output to cover the transience of the fuel cell. Since the fuel cell is the core
component of power draw, the Hydrogen supply is considered the limiting factor on power
duration.
4.4
RAIL ASSIST LAUNCH DEVICE
Unfortunately due to the constraints on time, the release mechanism could not fully be
integrated, and the final product could not be properly tested. The prototype design was able to
be tested, using a temporary release system consisting of rope which was anchored by hand, but
was unsuccessful in launching the plane due to resistance created by the misalignment of the two
main tubes, and premature lift caused by the lack of rigidity of the V bars. It was discovered that
the method used to join the main tubes failed to provide enough support, and was redesigned to
be welded together to form one solid piece rather two collapsible pieces. The material of the V
bar was also changed to provide enough resistance to bending caused by the lift of the plane.
4.5
INTEGRATED FLIGHT TESTS
The plane flew several times with a battery system only. The longest flight was 3
minutes. Flight could be sustained in the air for the whole 6 minutes of tested, full throttle,
battery life if the pilot had more experience flying the plane. This can be explained by the fact
that as the flight days progressed so did the pilot’s ability to control the plane. Flying the plane
in a large loop was easiest for the pilot to control. Additionally, the higher the plane, the more
time there was to adjust to the pitch of the plane and keep it from crashing since the plane lost
altitude while turning.
28
Additional tests were conducted to fly the UAV weighted to the load of the fuel cell
hybrid system. This was a much more difficult task then the already tough task of keeping the
battery operated plane in the air. The plane had to be powered at full throttle and into the wind
to gain as much lift as possible to achieve this feat. The plane would fly for a short time with the
additional weight required for the fuel cell but could not be controlled for any longer than 10-15
seconds.
Unfortunately, flight was not achieved with the fuel cell hybrid system due to equipment
malfunction and lack of testing time. This could be accomplished with only a week more of
flight time as a direct result of the experience gained over the five days of flight testing. Flight
times that were four seconds on day one were over three minutes on day five. A huge factor that
limited testing time was the weather condition. Too much wind (greater than 5mph) proved to
be too much for the large Skywalker X8 to maintain control. Additionally, finding a location
that was large enough to fly with mostly grass to land on was also a major issue. The Bridge
Church location on Indian River Road in Virginia Beach proved to be very nice but a bit far (3040 minutes from campus). This would mean a two and a half hour trip to refill Hydrostiks give
that all 6 sticks needed to be refilled. Flight with the AUW of 3,020 grams (1st iteration hybrid
system) was proven to be a success but when the 2nd iteration of the hybrid system with the extra
battery weight was deemed necessary, the AUW of 3,470 grams proved to be too close to the
rated AUW of 3,500 grams. Combine that with the wind at the time, which was 9 mph, and the
UAV could not achieve flight at the mock weight of the 2nd iteration hybrid system, leading no
onboard fuel cell-battery hybrid system testing to occur.
29
5
DISCUSSION
The purpose of this project was to investigate the feasibility of using fuel cell technology
to replace the battery power in an Unmanned Aerial Vehicle (UAV).
This was done by
modifying an already existing UAV model designed to fly using battery power, and converting it
to fly using a hybrid system of fuel cell and battery power. The intended result was to prove the
concept of fuel cell powered flight with a second objective of extending flight endurance, as well
as reduce ground time.
The Skywalker X8 was chosen as the airframe to convert because of its high payload
rating. While the initial calculations of the total weight of the fuel cell were technically within
range of the airframe’s weight capacity, the airframe lacked a high enough safety factor to
accommodate the slight change of additional weight found necessary once the hybrid system
moved on to the 2nd iteration. One of the other two airframes considered originally may have
performed better, particularly the Talon, since it was more durable than the Styrofoam
Skywalker X8.
The vehicle subsystems analysis and selection was a complete success, matching the
needs of the UAV at every point of the project. Larger diameter and pitch propellers were
deemed more applicable in this scenario because of the extra thrust generated, even though they
draw more power.
Cost, power output, and weight were the main parameters in fuel cell parts selection. For
the fuel cell type selection, these parameters limited the type chosen to the PEM fuel cell which
is run on pure Hydrogen, a fuel that is readily available via Hydrogen generators supplied by the
Mechanical Engineering Department here at ODU. The operating temperature also was a large
factor in selection, as more than half of the types available operate at temperatures much too high
30
to be considered being placed in a Styrofoam fuselage. Experiments proved that Hydrostiks
could be used as fuel storage for a Horizon H-100W fuel cell, though they had limited
effectiveness. They also showed that the hybrid system had a greater power output than just the
fuel cell’s rated power output. Three Hydrostiks was proven to be the most effective during fuel
cell tests. The Hydrostiks had never been tried on a fuel cell as large as the H-100W and testing
proved that their integration with this fuel cell system is possible, though not effective. Because
of the irregular flow, a lot of Hydrogen is wasted in the transient state period of operation and the
fuel cell is not as efficient. A large fuel canister could be utilized, so long as it is deemed safe
and is not too heavy. The 2nd iteration of the hybrid system proved to be stable and functional
but for weight purposes, an alternative power source than the 3S Lipo Battery should be used for
the fuel cell controller.
The RALD, which was built because of testing ease and safety concerns, not only failed
to successfully launch the plane on every trial, but also caused severe damage to the propeller
and the airframe body per launch. In order to achieve effective use of the RALD, a new release
mechanism must be designed and integrated to fit the new welded beam. Once this is done the
system should achieve full functionality. The integration of 3D printing into the design of the
release mechanism would be the most optimal route as it would allow a semi-intricate
mechanism to be designed that would also fit into a limited space. 3D printing should also be
integrated into the cart base, as doing so would provide increased stability and a more accurate
fit onto the rail. Improvements could also be made by having the main beam re-machined in
order to have the holes properly placed for the legs and release mechanism. Using pull action
toggle clamps in place of welding for the main beam could also greatly improve the support and
potentially restore its intended collapsibility.
31
Though there were no injuries during testing, a glove of ¾ forearm length is
recommended for safety of the UAV thrower, as the propeller can cause serious injuries if great
care is not taken. Additionally, using a large tarp as a buffer for the first 10 feet of flight proved
to be extremely helpful in keeping the plane together better after crashes during takeoff (Figure
23). Four people held the corners of the tarp
and “caught” the plane before it could hit the
ground. A wind vein or wind sock to measure
wind direction also proved to be very useful
for testing as the wind is a huge factor in the
control during flight.
Additionally an
anemometer should be considered to measure
Figure 23: Using a Tarp to Catch the UAV during Attempted Takeoff
wind speeds for data collection and flight
analysis. Due to the range and speed of the plane, first person view (FPV) flying equipment
would be a worthwhile investment to better gage distances from plane to object and also to keep
the plane in the view of the pilot since the plane was much easier to control when flying higher
and in large loops.
32
6
CONCLUSIONS
After months of research and testing, several conclusions were drawn:
The Skywalker X8 has plenty of room for the fuel cell system but the delta wing
configuration may not be the ideal type of airframe for this application, as maneuverability and
liftoff have proven to be obstacles. As propeller size (the pitch in particular) increases, so does
the thrust generated, though the larger propellers tend to draw more power from the power plant.
Fuel cells can be successfully integrated with batteries to create hybridized power systems that
perform better than each of the systems individually. Additionally, Hydrostiks can be used as
fuel storage solutions for 100 Watt fuel cells, but are not very effective. A Rail Assist Launch
Device (RALD) is a great idea for getting the UAV off the ground safely and smoothly but there
are a lot of things that may go wrong with the system that can negate the RALD’s effectiveness.
Finally, flying UAVs requires a lot of experience and getting a UAV into the air is the hardest
part of flight.
This research has proven the concept of powering a UAV with a fuel cell system is
possible, given that fuel cell system weight can be minimized. If fuel cell system weight can be
minimized, flight times can be extended greatly, limited only by how much fuel is onboard the
UAV to power the fuel cell system, since at cruise conditions, the fuel cell serves mainly to
charge the battery as well as power the motor. While there was limited information about this
research at the time of the start of this study, the results of this study can be used for the next
UAV Fuel Cell team to almost certainly get the project off the ground and into the skies.
33
7
REFERENCES
[1]
A. Birk, B. Wiggerich, H. Bulow, M. Pfingsthorn, and S. Schwertfeger, "Safety, Security,
and Rescue Missions with an Unmanned Aerial Vehicle (UAV) Aerial Mosaicking and
Autonomous Flight at the 2009 European Land Robots Trials (ELROB) and the 2010
Response Robot Evaluation Exercises (RREE)," Journal of Intelligent & Robotic
Systems, vol. 64, pp. 57-76, 2011.
[2]
U. C. Ofoma and C. C. Wu, "Design of a fuel cell powered UAV for environmental
research," in Proceedings of the AIAA 3rd" Unmanned... Unlimited" Technical
Conference, Workshop, and Exhibit, September, 2004, pp. 20-23.
[3]
Gur, O., Rosen, A. “Optimizing Electric Propulsion Systems for UAV’s.” AIAA 20085916. 12th AIAA/ISSMO Multidisciplinary Analysis and Optimization Conference,
Victoria, British Columbia Canada, 10-12 September 2008.
[4]
C. Herwerth, C. Chiang, and A. Ko, "Integration of a PEM Fuel Cell into Slow Speed
UAV," Unmanned Syst. North America Conf., vol. 1, pp. 414-428, 2006.
[5]
K. Kyunghwan, K. Taegyu, L. Kiseong, and K. Sejin, "Fuel cell system with sodium
borohydride as hydrogen source for unmanned aerial vehicles," Journal of Power
Sources, vol. 196, pp. 9069-75, 2011.
[6]
T. H. Bradley, B. A. Moffitt, T. F. Fuller, D. N. Mavris, and D. E. Parekh, "Comparison
of Design Methods for Fuel-Cell-Powered Unmanned Aerial Vehicles," Journal of
Aircraft, vol. 46, pp. 1945-56, 2009.
[7]
T. H. Bradley, B. A. Moffitt, T. F. Fuller, D. Mavris, and D. E. Parekh, "Design studies
for hydrogen fuel cell powered unmanned aerial vehicles," American Institute of
Aeronautics and Astronautics, 2008.
34
[8]
M. Zhou and J. Prasad, "Transient Characteristics of a Fuel Cell Powered UAV
Propulsion System," Journal of Intelligent & Robotic Systems, vol. 74, pp. 209-220,
2014.
[9]
C. Hao and A. Khaligh, "Hybrid energy storage system for unmanned aerial vehicle
(UAV)," in IECON 2010 - 36th Annual Conference of IEEE Industrial Electronics, 7-10
Nov. 2010, Piscataway, NJ, USA, pp. 2851-6, 2010.
[10]
Bradley, T. H., Moffitt, B., Thomas, R. W., Mavris, D. and Parekh, D. E., 2006.
“Test
Results for a Fuel Cell-Powered Demonstration Aircraft,” in Society of Automotive
Engineers Power System Conference, November 7-9, 2006, New Orleans, 2006.
[11]
Moffitt, B., Bradley, T. H., Mavris, D., and Parekh D. E. “Design Space Exploration of
Small- Scale PEM Fuel Cell Long Endurance Aircraft.” in 6th AIAA Aviation
Technology, Integration and Operations Conference, September 25-27, 2006, Wichita,
Kansas. AIAA-2006
[12]
M. Dudek, P. Tomczyk, P. Wygonik, M. Korkosz, P. Bogusz, and B. Lis, "Hybrid Fuel
Cell–Battery System as a Main Power Unit for Small Unmanned Aerial Vehicles
(UAV)," Int. J. Electrochem. Sci, vol. 8, pp. 8442-8463, 2013.
35
APPENDIX 1: GANTT CHART
36
APPENDIX 2: BUDGET
Funds
Supplier
Frank Batten College of Engineering
Mechanical Engineering Department
Mechflutech LLC
Total
Amount
$1,000.00
$1,000.00
$3,000.00
$5,000.00
Costs
Date
Friday, February 13,
2015
Friday, February 13,
2015
Friday, February 13,
2015
Friday, February 13,
2015
Friday, February 13,
2015
Friday, February 13,
2015
Friday, February 13,
2015
Friday, February 13,
2015
Friday, February 13,
2015
Friday, February 13,
2015
Friday, February 13,
2015
Tuesday, February 24,
2015
Tuesday, February 24,
2015
Part
Type
Supplier
Quantity Cost/Part
Total Cost
Budgeted Amt
Remaining
$5,000.00
Total Budgeted Amount
Battery
3S 11.1v
5000mah20c
lithium ion
polymer
Debbie's
RC World
2
($60.99)
($121.98)
$4,878.02
Wire adapters
Parallel Deans U
adapter 2 to 1
Debbie's
RC World
1
($10.99)
($10.99)
$4,867.03
Electronic Speed
Controller
Phoenix Edge 75
32V 75 AMP
Debbie's
RC World
1
($102.00)
($102.00)
$4,765.03
Battery Charger
Prophet Sport
Duo 50WX2 AC
Debbie's
RC World
1
($89.99)
($89.99)
$4,675.04
Servos
S3004 Servo
Standard BB
Debbie's
RC World
4
($13.99)
($55.96)
$4,619.08
Adapter
Ultra Plug
Debbie's
RC World
2
($3.75)
($7.50)
$4,611.58
Propeller
Sport Propeller 12
x7
Debbie's
RC World
2
($4.29)
($8.58)
$4,603.00
Debbie's
RC World
1
($74.99)
($74.99)
$4,528.01
Debbie's
RC World
1
($229.99)
($229.99)
$4,298.02
Motor
Remote
Power 32
Brushless
Outrunner Motor
Dx6 6 Channel
System w/ AR610
Receiver
Airframe
Skywalker X-8
FPV 2120mm
Hobby
King
3
($229.80)
($689.40)
$3,608.62
Direct Fill /
Hydrostik Test
Equipment
Hydrogen UHP
Grade, 300 cf
Airgas
1
($29.13)
($29.13)
$3,579.49
Direct Fill /
Hydrostik Test
Reg. High Del, 01000 psi, 350
Airgas
1
($350.00)
($350.00)
$3,229.49
37
Tuesday, February 24,
2015
Tuesday, February 24,
2015
Tuesday, February 24,
2015
Friday, February 27,
2015
Friday, February 27,
2015
Monday, March 02,
2015
Monday, March 02,
2015
Monday, March 02,
2015
Monday, March 02,
2015
Friday, March 06,
2015
Wednesday, March
18, 2015
Wednesday, March
25, 2015
Thursday, March 26,
2015
Thursday, March 26,
2015
Thursday, April 09,
2015
Thursday, April 09,
2015
Thursday, April 09,
2015
Thursday, April 09,
2015
Equipment
CGA
Direct Fill /
Hydrostik Test
Equipment
Direct Fill /
Hydrostik Test
Equipment
Direct Fill /
Hydrostik Test
Equipment
6' Hose
Assembly, Hoses,
1/4 FM NPT
Airgas
1
($147.27)
($147.27)
$3,082.22
Brass Quick
Connect (M)
Airgas
1
($46.20)
($46.20)
$3,036.02
Brass Quick
Connect (F)
Airgas
1
($34.40)
($34.40)
$3,001.62
Soldering Iron
Soldering Iron 60
W
Debbie's
RC World
1
($10.59)
($10.59)
$2,991.03
Propeller
12x8 Prop
Debbie's
RC World
1
($4.23)
($4.23)
$2,986.80
Fuel Cell
Horizon H-100
Fuel Cell
Fuel Cell
Store
1
($1,745.00)
($1,745.00)
$1,241.80
Fuel Storage
Hydrostik PRO
Fuel Cell
Store
1
($30.00)
($30.00)
$1,211.80
Pressure
Regulators
Horizon Fuel Cell
H-Series
Pressure
Regulator
Fuel Cell
Store
4
($158.00)
($632.00)
$579.80
Fuel Cell
Store
1
($29.00)
($29.00)
$550.80
Debbie's
RC World
1
($27.55)
($27.55)
$523.25
Home
Depot
1
($118.20)
($118.20)
$405.05
Hoses
Hoses and
Fittings
B&B
Hose and
Rubber
Co.
1
($13.57)
($13.57)
$391.48
Adapter
Pressure Adapter
Swagelok
1
($9.80)
($9.80)
$381.68
Adapter
Pressure Adapter
Swagelok
1
($6.10)
($6.10)
$375.58
Electric Connector
Kwik Grip EZ
Connector
Debbie's
RC World
2
($2.04)
($4.08)
$371.50
Motor
Power 32
Brushless
Outrunner Motor
Debbie's
RC World
1
($74.99)
($74.99)
$296.51
Propeller
12x10 Prop
Debbie's
RC World
2
($3.99)
($7.98)
$288.53
Propeller
12x8 Prop
Debbie's
RC World
1
($4.30)
($4.30)
$284.23
Shipping
USB ESC Link
Quick Field
Programmer Air
Link
Catapult Supplies
38
Thursday, April 09,
2015
Thursday, April 09,
2015
Thursday, April 09,
2015
Thursday, April 09,
2015
Wednesday, April 15,
2015
Thursday, April 16,
2015
Friday, April 17, 2015
Friday, April 17, 2015
Propeller
13x10 Prop
Debbie's
RC World
2
($4.89)
($9.78)
$274.45
Propeller
13x8 Prop
Debbie's
RC World
1
($5.06)
($5.06)
$269.39
Propeller
14x10 Prop
Debbie's
RC World
1
($5.99)
($5.99)
$263.40
Debbie's
RC World
1
($6.73)
($6.73)
$256.67
Tax
Fitting
Fitting for
Hydrostik
Fuel Cell
Store
1
($50.00)
($50.00)
$206.67
Servos
S3004 Servo
Standard BB
Debbie's
RC World
2
($14.83)
($29.66)
$177.01
Propeller
14x10 Prop
Debbie's
RC World
4
($5.18)
($20.73)
$156.28
Battery
3S 11.1v
5000mah20c
lithium ion
polymer
Debbie's
RC World
2
($64.65)
($129.30)
$26.98
Breakdown by Subsection
Total Budget
Airframes
Vehicle Subsystems (Batteries,
Motor, Controller, Propeller, etc)
Fuel Cell & Hydrostik & Hydrofill
Rail Assist Launch Device
Total Budget Left
39
$5,000.00
($689.40)
($1,042.95)
($3,122.47)
($118.20)
$26.98
APPENDIX 3: COMPARISON OF DIFFERENT FUEL CELL TECHNOLOGIES
Table 1: Comparison of Fuel Cell Technologies (U.S. Department of Energy)
40
APPENDIX 4: PROPELLER FULL THROTTLE TEST RESULTS
Figure 24: Voltage Curves for Different Propellers
Figure 25: Current Curves for Different Propellers
Figure 27: Power Curves for Different Propellers
Figure 26: Effects of Propeller Size on Motor Speed
41
APPENDIX 5: SYSTEM COMPONENTS BY MASS
Battery Powered UAV:
Component
UAV Frame
3S Battery
S3004 servo
S3004 servo
Power 32
motor
12x7 Propeller
Adaptor
ESC
Total
AUW
Fuel Cell/Battery
UAV 1st Iteration
Fuel Cell/Battery
UAV 2nd Iteration
Mass
(grams)
Component
UAV Frame
3S Battery
S3004
S3004
Power 32 motor
12x7 Propeller
Adaptor
ESC
Stack weight
Hydrostik (3)
Pressure regulator
(5)
Fuel Cell Controller
Total
AUW
Component
UAV Frame
880
447.92
37.2
37.2
205.3
44.2
13.9
111.5
1777.22
897.22
Mass
(grams)
880
447.92
37.2
37.2
205.3
44.2
13.9
111.5
1290
280.2
150
400
3897.42
3017.42
Mass
(grams)
880
42
3S Battery
S3004
S3004
Power 32 motor
12x7 Propeller
Adaptor
ESC
Stack weight
Hydrostik (3)
Pressure regulator
(5)
Fuel Cell Controller
extra battery
Total
AUW
447.92
37.2
37.2
205.3
44.2
13.9
111.5
1290
280.2
150
400
447.92
4345.34
3465.34
43