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Formation Flying

Shunsuke Hirayama

Tsutomu Hasegawa

Aziatun Burhan

Masao Shimada

Tomo Sugano

Rachel Winters

Matt Whitten

Kyle Tholen

Matt Mueller

Shelby Sullivan

Eric Weber

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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)

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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)

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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)

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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)

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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)

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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)

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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)

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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)

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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)

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• 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)

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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)

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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)

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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)

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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)

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• 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)

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• 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)

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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)

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• 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)

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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)

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Hardware determination

• Camera– Small mass, weight;

operable in space conditions

– This determined an orbit range to stay within

Rachel Winters (21/30)

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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)

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Hardware continued

• Gyro– Adds accuracy to

attitude determination– Included in Reaction

Wheel System

Rachel Winters (23/30)

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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)

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Hardware continued

• GPS– Differential GPS used

for location/velocity information

– Light weight– Includes two

antennas, two receivers

Receiver

AntennaRachel Winters (25/30)

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Hardware continued

• CPU– Provides computer

processing for hardware components

– Includes several USB ports

Rachel Winters (26/30)

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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)

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Hardware continued

• Thrusters– Needed to make

orbital changes– Cold gas thruster

system• Nitrogen

Tank

Thruster

Rachel Winters (28/30)

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Hardware continued

• Battery– Satellite needs power

to operate for 24 hours

– Use solar cells minimize battery demand

Rachel Winters (29/30)

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Hardware continued

• Heater– Some devices are

temperature sensitive– Maintains

temperature of satellite within allowable range

Rachel Winters (30/30)

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Demonstration

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Recommendations for Future Work

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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

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Thank you!

For all your time and assistance.

Mr. SurkaJoe

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Questions? Comments?

Formation Flying