Development of a fly-back CANSAT in 3 weeks

Mehmet Ertan Umit

Matthew TETLOWITU Faculty of Aeronautics and Astronautics

University of Adelaide

Space Systems Design and Testing Laboratory

School of Mechanical Engineering

Istanbul, TURKEY

Adelaide, AUSTRALIA

Willy CABANAS

Hiroaki AKIYAMA, Shusaku YAMAURA

Central America Association for Aeronautics and Space

Wakayama University Institute for Education on Space

Guatemala, GUATEMALA

Wakayama, JAPANSalu OLALEYE
African Regional Centre for Space,
Science & Technology Education
Osun State, NIGERIAIn this case launcher was an independent source for thedevelopment team. The requirements were set before launch.

Abstract-Two CanSats are developed in Wakayama University
by international researchers in one month. The first CanSat wasdeveloped in less than three days. The second CanSat was moreadvanced

anddevelopedinthreeweeks.

ThedesignB.

andCanSat

CanSat is the main payload. Avionics and structure could

development phases are explained in this paper.

be named as CanSat. There are several CanSat requirements.
Different competitions have their own requirements, but can

Keywords-component; CanSat, Guidance, Navigation, FlightControl

generalize some main requirements. These are;[1]•I.

CONCEPT

the rocket cargo.

CanSat concept was proposed by Prof. Twiggs in 1998. The•

main idea behind a CanSat was to create a simple satellite-like
satellites

havearound

10mincommunication

The CanSat shall be compatible with the launchingsystem.

device by students, to gain hands-on experience. Generally
LEO

All the components (CanSat, parachute etc.) shall fit intime.

•The CanSat should have a recovery system like aparachute to be able to be reused after launch.

Typically a 4 km altitude launched CanSat also have around 10min fly time. In CanSat mission students can read sensors on­•board and simply they can simulate a simple satellite. There areCanSats can use RF communications. CanSats with RF
Transmitters shall have properly licensed operators;

two important things to consider. These are the launcher andthe CanSat itself.

•Depending on the competition the total cost of theCanSat cannot exceed a certain amount. (in this caseA.

50.000¥)

Launcher

The launcher is used to send the CanSat into a certain
altitude. For launch rockets,helicopters,

basically

anythingballoons,
thatUAV's,flies

could•

planes orbeVolume: The CanSat should be equal or smaller than acylinder with dimensions of Wcm radius and 26cm

used.

height.

Generally a rocket is used for competitions or main mission.
For testing a balloon or a helicopter is more reliable and cheap•Mass: The CanSat mass is defined by the rocket, thus

solution. In this case a rocket is used for the main launch and athe heavier mass means lower altitude. For a safe

balloon is used for testing.

parachute opening altitude mass of the CanSat shouldbe lower than 1kg

For a safe launch a launch site was defmed for this case.
After the ejection the rocket opens its own parachute for a safe

•return.

978-1-4244-9616-7111/$26.00 ©2011 IEEEThe CanSat should be able to eject when the cargo bay
opens after reaching the apogee.

804

Basically there were 3 main methods to accomplish themission.
•Rover•Para-glider•

Glider

Surely the most successfully one of these methods is therover. Rover is a simple toy -car which goes to the target after
it lands. Landing is aided by a simple parachute. After landing
the rover comes out of the parachute and simply navigates tothe target by onboard avionics. Rover is successful because it
is simple, it doesn't require any complex flight systems. All it
needs is to roll the tires until it reaches the target.
Para-glider is simply a parachute with controller. It iseasier compared to glider, due to its static stable nature. As acontroller

para-gliderhastwostrings

attachedtotheparachute. If the strmg on the right should be pulled the para­
glider will try to turn right, or pulling the left string will tum
the para-glider left.
Glider is considered the most challenging version of acome-back mission CanSat. Glider is not stable as other types
and it requires complex algorithms to navigate.
The glider type is chosen due to its complexity. The main
mission was to learn how to do a CanSat, therefore choosing adifficult mission made sense.
The CanSat is called as TANGsat 2. The name comesfrom developers. Developers and the writers of this paper are
from Turkey, Australia, Nigeria and Guatemala. TANGsat IFigure 1. Wing shape of a F-14

was a simple telemetry receiving CanSat, which was built in 1week.
II.

STRUCTURE

Airfoil Sha�The main difficulty of the structure is the way to put theglider inside the rocket. The cargo of the rocket has acylindrical shape, but the glider should have wings, which
won't fit in to the rocket. Two different methods were selected
for the first trade off. One of them was rolling the wings using

Figure 2. NACA 64412 airfoil

steel measurement tape. Advantage of this type is its wing size,
but this design is flexible and has limited airfoil option.

First version of the CanSat was built of aluminum. But theThe other option was to use foldable wings. Thisweight

design is used on F-14 aircraft [2]. The wings are folded in the90kmlh

version has smaller area of wing but it has an efficient airfoil
and structurally it's more stable. The wings of F-14 could be

anliftitself. Our

payload or electronics. After

someElevator of the glider is made of balsa wood. It has a sizewings is 7cm on the tip and 4,6cm on fuselage. The airfoil is[3],anytoflight speed was aroundlimit; therefore its width is limited to 10 cm. The size of the tailis important, because total length of the glider should be shorter

NACA 64412. The ribs are cut from simple foam. The wings
lavafoilwithoutheavy

decreased to 40kmlh.

stable structure and efficient airfoil. The cross-section of thefilm.

too170grams with payload. After optimizing the wing area and theAfter the trade-off foldable wings are chosen, because of its

shrinkingwasangle between wings and fuselage the cruise speed hasoff and landing.

bygliderThe weight of the CanSat has dropped from 350grams tospeed cruise and low aspect ratio on low speed cruise or take­coveredtheunsuccessful attempt the structure was changed to balsa wood.

seen on Figure 1. The wings have high aspect ratio on highareof

calculations showed that cruise

rocket and after the ejection they unfold using a spring. This

than 35 cm; it's hard to have enough momentum from tail.

onlinedevelopment software is used to determine the airfoil. A

Because of the folding wings there were no space for alavafoil screen capture of the airfoil is presented on Figure 2.

horizontal tail on the upper side of the glider; therefore the805

horizontal tail was put below the fuselage. The horizontal tailwas also cut out from foam; it has a NACA 64012 airfoil
section to increase the force on the horizontal tail. Because of
the folding wings no ailerons were used on glider. Control andguidance of the glider will be maintained by rudder, therefore
to increase the force of the horizontal tail. All the horizontal
tail is used as rudder.
The payload of the CanSat could be considered as sensors,
actuators and electronic systems. To attach the payload to theglider a special "gondola" was cut out of foam. This gondola
has a shape to decrease drag of the payload and it will also help

Figure 4. MBED Microcontroller overview

to float on water after a water-landing incidence.

There are also sensors for attitude determination of theCanSat. These are 3-axis accelerometer, 3-axis gyro, 2-axis
magnetometer,

temperatureandstaticpressure

sensors.

Accelerometer and gyro data is used for roll and pitch angle
detection. Magnetometer is used for heading. Pressure sensor isused for altitude determination.
A GPS receiver is also used for navigation purposes. The
receiver is an EM-41l GPS [5]. Commercial GPS receivers
have acceleration, speed and altitude limitations. Depending on
previous missions some receivers might lose tracking the GPSsignal. Hot start of the GPS is around 30 seconds, therefore toensure

positioning

abackupinertial

navigation

isalsoconsidered.
An xbee pro [6] modem is used for communication with theground station. Every data from sensors are processed andpacked in mbed and send to ground station using this modem.
In ground station simple software just records this data forfuture processing.
3-axis accelerometer is an ADXL345 [7]. Its data is being
read 100Hz using I2C bus. ADXL345 is selected because of its
high g characteristics. It can read up to l6g. The rocket canreach up to 20g. This high acceleration should be read for theinertial navigation system.
3-axis gyro used on-board was an ITG-3200 [8] mems
gyro. It is a serial output low-power high accuracy gyro. Thecommon thing between these sensors is the availability andFigure 3. Mechanical design

simplicity. All the sensors are easily available on the internet oreven in local electronic stores. There are also lots of examples

Figure 3 shows the two different positions of the wings.

available on the internet about these avionics,

The upper figure shows the glide (open) position of the wings.
CanSat will wait safely in cargo untill ejection.
III.

which

isessential in a fast development process.

The figure bellow shows the launch position, in which theDigital compass was a CMPS03 [9]. It has 2 magnetic
sensors to measure the angle between the sensor and magneticAVIONICS

north.

Sincethe sensor

is 2-axis,

itcannot compensate

inclination and tilt angles; therefore custom tilt compensation isMain on-board avionic is the microcontroller mbed [4]. It

used for accurate heading detection.

has a 100MHz microprocessor. Developed algorithms are
running on this microprocessor. An online C++ compiler isThe battery is a very small 200mAh 7.4V lithium-polymer

available for mbed. Figure 4 shows the view of the mbed

battery, which only weighs 24 grams. According to the power

microcontroller.

budget the peak current of the satellite is 600mAh, therefore a
JOC battery is selected. The battery can support the electronics
for 20 minutes, which is enough for a fly-back mission.
IV.

NAVIGATION AND GUIDANCE

To navigate the CanSat a GPS receiver is used. The GPS
datasheet shows that positioning error is around 5meters,

806however by testing the accuracy is observed as 2 meters. The
aim of the mission is to come closer than 100 meters to theFigure 5 shows the detailed flight plan of the CanSat.

target. The GPS provides time, longitude, latitude, altitude,V.

speed and heading information in 10 Hz.

TESTINGFor testing the CanSat a special balloon is used. TheA 2-axis digital compass is used for heading data. Theballoon is filled with helium and ascended about 50 meters. Asensor has 12C output as heading value in degrees compared tomagnetic north. Because of 2-axis magnetic measurement, thespecial device is used for ejection, which has the same volume

device doesn't have any tilt compensation; therefore a tilt

with the rocket. After testing it has been seen that the CanSats

compensation

accurate

glide ratio [10] is around 1. This low glide ratio is anmeasurement. Tilt angles are measured from accelerometer andadvantage, because higher glide ratios means faster dives,

systemhad

beendeveloped

forusing simple trigonometric functions with 2-axis magnetic

according to our flight plan. In a windy condition the rocket

measurements heading value was corrected. The new digital

will launch with an angle compared to the surface of the earth.

compass is able to work +-40 degrees of tilt with 10 degrees of

Test with the final design of the CanSat could not be

accuracy. The heading angle from GPS and compass iscompleted due to the earthquake happened in 11 of Marchmeasured and mean average value is used for guidance.

2011 in Japan.

A command from ground station records the currentVI.

position of the CanSat as the target position from GPS and theCONCLUSIONThe CanSat project is considered as a successful project,static pressure level from pressure sensor. The pressure isejection

because the aim of the project was to distribute CanSat idea tomicroprocessor receives the position information from GPSthe world. Project members have gained experience on every

and compares that info with the target position. The tum angles

topic of CanSat and they return to their countries eager to startaretheir own CanSat group.

measuredfor

calculated

altitudeusinginformation.

simpletrigonometry

After

with

alreadycalculated heading information. This tum value is required by

On technical aspect the final design could not be tested due

control system.

to the disaster happened in Japan. This design could be tested
in future by other groups or students in Wakayama University.

For an accurate landing the altitude should be controlled.
Altitude is measured using GPS and pressure sensor values.

ACKNOWLEDGMENT

After ejection the glider should tum to target and dive with aspecific angle. The altitude accuracy of the GPS receiver isThis project is built in Wakayama University Japan.

around 15, which is not enough for landing; therefore theDevelopers are grateful to those who organized "CanSat

pressure sensor is important on landing. Before launch theLeader Training Program" We also want to present our thanks

static pressure is recorded and during dive when the pressure

to academic/non-academic employers, teaching assistants andlevel becomes close to target point, a pitch-Up command will

students of Wakayama University. Finally we would like tosend to the elevator for a soft landing.

express our sympathy to the kind people of Japan, who
suffered from that disaster.
REFERENCES[I]

Europen Union CanSat
competitions.html[2]F-14 Tomcat
http://www.fas.orglprograms/ssp/man/uswpns/air/fighterIfl4.html

requirements,

http://www.ca nsa t.eu/cansat­[3]

Javafoil. http:// www.mh-a erotools.de/a irfoils/ja va foil.htm[4]

MBED Microcontrollers- http://mbed.org!

[5]

Globalsat EM-411 GPS modulehttp://www.globalsat.co.uk/product pages/gsat products module em41I.htm

[6]

Xbee
Pro
modemhttp://www.digi.com/products/wireless/pointmultipointlxbee-pro-series I-module.jsp[7]

ADXL345 accelerometer- http://www.analog.com/en/mems­
sensorslinertial-sensors/adx 1345/products/product.html[8]ITG-3200 gyro http://invensense.com/mems/gyro/itg3200.html[9]

CMPS 03 Digital Compass - http://www.robot­
electronics.co.uklhtrn/cmps3tech.htm[10] Glide Ratio http://en.wikipedia.orglwiki/Lift-to-drag_ratio#GlideJatio

Landing
Figure 5. Flight Plan

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