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1
Formation Flying
Shunsuke Hirayama
Tsutomu Hasegawa
Aziatun Burhan
Masao Shimada
Tomo Sugano
Rachel Winters
Matt Whitten
Kyle Tholen
Matt Mueller
Shelby Sullivan
Eric Weber
2
Design
• A satellite that will fly escort to the space shuttle
• Satellite provides visual inspection of shuttle exterior for 24 hour period of time
• Satellite will be transported into space on shuttle
• Satellite must meet University Nanosat requirements
Rachel Winters (2/30)
3
Previous Work• AERCam “Sprint”
– Successfully tested on STS-87 for 1.25 hours around Orbiter
– Live video feed– Remote controlled
• Mini AERCam– Successful ground tests– Live video feed, including orthogonal
view– Remote and supervised autonomous
control optionshttp://aercam.jsc.nasa.gov/
http://spaceflight.nasa.gov/station/assembly/sprint/index.html
Rachel Winters (3/30)
4
Improvements
Our design is...– Completely autonomous– Powered sufficient to operate for 24 hours– Supervision is only necessary for launch and
retrieval
Rachel Winters (4/30)
5
Systems Integration & Management
Rachel Winters, Matt WhittenMajor Tasks:• Expendable vs Recoverable spacecraft• Recovery method design• Determine shuttle-interface
requirements• Determine picture order
Rachel Winters (5/30)
6
Relative Orbit Control & Navigation
Kyle Tholen, Matt MuellerMajor Tasks:• Determine relative orbit to meet mission
requirements• Determine major disturbances from orbit
and counteract them• Single vs Multiple spacecraft trade study• Determine thruster equipment• Find Tank size• Determine navigation method
Rachel Winters (6/30)
7
Configuration & Structural Design
Shelby Sullivan, Eric WeberMajor Tasks: • Find camera and lens• Camera field of view analysis• Design structure (material, shape)• Configure component positioning• Mass budget• Solidwork components
Rachel Winters (7/30)
8
Attitude Determination & Control
Shunsuke Hirayama, Tsutomu HasegawaMajor Tasks:• Determine method of attitude control• Single vs Multiple cameras• Determine pointing accuracy necessary• Determine torque disturbances
Rachel Winters (8/30)
9
Power, Thermal & Communications
Aziatun Burhan, Masao Shimada,Tomo Sugano
Major Tasks:• Determine power needed by satellite• Battery only vs Solar Cell + Battery• Define thermal environment (outside and
inside sources)• Determine method of heating• Determine transmission method• Determine differential drag• Integration for CPU
Rachel Winters (9/30)
10
Trade Studies
• Expendable vs Recoverable Satellite– less expensive to reuse– viable method of recovery– reasonable amounts of extra fuel needed
• Single vs Multiple Satellite(s)– amount of extra fuel needed for plane
transfers– ability to “see” entire shuttle with only 1
satellite
Rachel Winters (10/30)
11
• Solar cells + Battery vs Battery only– Amount of power solar cells can provide in 24
hr period– Amount of power needed by satellite
components– Size of battery needed to compliment solar
cells vs size of battery needed with no recharge
• Single vs Multiple camera(s)– Ability to control attitude– Camera size
Trade Studies continued
Rachel Winters (11/30)
12
Design Walkthrough
• Assumptions and Requirements– Mass restricted to 50 kg– Volume restricted to 60x60x50 cm3
– Necessary to operate for 24 hours, power source must last this long
– Assumed an earth-relative orbit that was the same as the ISS orbit
– Assumed our shuttle-relative orbit was within safety standards (rp = 118 m, ra = 237 m)
Rachel Winters (12/30)
13
Orbit Design
– Accuracy of known location/velocity was important
– Maintain a “safe” distance away from the shuttle
– Remain within camera range
Created a general orbit
Rachel Winters (13/30)
14
Orbit Design continued
• Determined orbital disturbances– J2 disturbances– Drag differences in Low Earth Orbit– This determined the amount of thrust
needed to maintain desired orbit
Rachel Winters (14/30)
15
Orbit Design continued
• Plane change decided– Used a plane change to keep the number of
satellites to 1 (Trade Study)– Affects the amount of cold gas needed
Rachel Winters (15/30)
16
• We determined the type of attitude control we wanted: zero-momentum– It allows us to control all three axes of
rotation– We needed to be able to point at the shuttle
at all times– This determined the mode of control:
Reaction Wheels
• We already needed control to counteract torque disturbances– Aerodynamic torque– Gravity-Gradient torque– Solar radiation pressure torque
Satellite Design
Rachel Winters (16/30)
17
• To simplify the process of calculating torque, we chose to design the center of mass to be in the center of the satellite
• We chose to make the satellite a 50x50x50 cm3 cube to simplify the thermal analysis
Satellite Design continued
Rachel Winters (17/30)
18
Satellite Design continued
We modeled the components and satellite in Solidworks to map out what we wanted it to look like
Rachel Winters (18/30)
19
• Thermal control designed– Found the temperature range of the
environment– Found the temperature tolerance of
hardware– Used the mass-based layout to determine
necessary thermal control within satellite
Satellite Design continued
Rachel Winters (19/30)
20
Satellite Design continued
• Power subsystem– Approximated power drain with major
components– Made early approximation on battery/solar
requirements– Determined number of solar cells we can
support– Found power demand including all
components– Determined back-up battery requirements
Rachel Winters (20/30)
21
Hardware determination
• Camera– Small mass, weight;
operable in space conditions
– This determined an orbit range to stay within
Rachel Winters (21/30)
22
Hardware continued
• Star tracker– For accurate attitude
control, 2 sensors needed
– Very accurate (within .001 degree)
– Must not be exposed to sunlight
Rachel Winters (22/30)
23
Hardware continued
• Gyro– Adds accuracy to
attitude determination– Included in Reaction
Wheel System
Rachel Winters (23/30)
24
Hardware continued
• Reaction wheel– Used to keep shuttle
in field of view– Able to induce up to
50 mNm of Torque
Rachel Winters (24/30)
25
Hardware continued
• GPS– Differential GPS used
for location/velocity information
– Light weight– Includes two
antennas, two receivers
Receiver
AntennaRachel Winters (25/30)
26
Hardware continued
• CPU– Provides computer
processing for hardware components
– Includes several USB ports
Rachel Winters (26/30)
27
Hardware continued
• Transmitter (wifi)– Able to transmit large
amounts of data over orbit range
– Connects with USB port
– Orbiter must also be connected to wireless network
http://www.amazon.com/802-11G-Wireless-Adapt-FROM100-Meters/dp/B000MN8MV4
Rachel Winters (27/30)
28
Hardware continued
• Thrusters– Needed to make
orbital changes– Cold gas thruster
system• Nitrogen
Tank
Thruster
Rachel Winters (28/30)
29
Hardware continued
• Battery– Satellite needs power
to operate for 24 hours
– Use solar cells minimize battery demand
Rachel Winters (29/30)
30
Hardware continued
• Heater– Some devices are
temperature sensitive– Maintains
temperature of satellite within allowable range
Rachel Winters (30/30)
33
FMEAFailure Mode Likelihood Solution
Electrical/ wiring failure Medium Recover or abandon,
depending on severity
Unable to recover
satelliteMedium Abandon, satellite orbit
will decay
Failure of star tracker
(one attitude sensor)Low – Med Backup sensor (gyro)
until recovery is made
Dirt or ice on camera
lensLow – Med Protective sleeve on lens,
debris check pre- launch
Error in focus of lens Low Computerized check
prior to shuttle launch
Collision with Orbiter Very Low Add failsafe to propel
satellite away from
shuttle
Coronal activity on sun
destroys satelliteVery Low This is known in advance,
plan missions around