Space Engineering Institute (SEI) Space Based Solar Power

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Space Engineering Institute (SEI)Space Based
Solar Power
Space Engineering Research Center Texas
Engineering Experiment Station, Texas AM
University

• By Bryan Babbitt, Nate Broughton, Will Dixon,
  Stephanie Hasskarl, Travis LaCour, Veronica
  Medrano, Joseph Noska, and Mindy Watts
• NASA Mentor Dr. G. D. Arndt
• TAMU Mentor Dr. Frank Little

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Project Goal

• Develop a design for a sandwich solar power
  satellite module with retrodirective wireless
  power transmission system for inclusion in
  Japanese LEO to earth solar power satellite
  demonstration
• Demonstrate software-controlled retrodirective
  wireless power transmission system

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Module System Sandwich Design
Photovoltaic Cells

• Energy Storage Power Conversion
• Retrodirective Control logic
• Thermal Management

Antenna Array
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Fall 2009 Goals

• Perform case studies for the preliminary design
  concept with software tools such as Satellite
  Tool Kit and Thermal Desktop
• Determine hardware components for
• Solar energy collection
• Power system
• Transmission system
• Antenna

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STK / Photovoltaic Cells

• Chose 35 angle of inclination circular orbit,
  based on orbits of other Japanese satellites of
  similar size.
• Chose a single crystal Si photovoltaic cell that
  has an efficiency of 17
• We modeled the top surface of our satellite ( 1
  m2) at this orbit and found
• Found that the average energy acquired for every
  month is 126X106 Joules 3X106 Joules per
  test transmission
• Determined experiment dates and times for beaming
  to College Station
• Satellite passes within 45 of normal
• Maximum transmission length of 170 seconds
• Eclipse requirement limits transmission times,
  but is still feasible.

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STK Image of Reception Cones
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Power Transmission and Antenna

• Power Transmission
• Determined a 40 km reception area required to
  achieve a beam coupling efficiency of 90
• Estimated a transmitting power of 2kW necessary
  for minimum ground pattern detection signal of
  0.1nW
• Identified hardware components for transmitter
  subsytem
• Microstrip Patch Antenna
• Maximum 450 element phased array
• Capable of achieving 2kW transmitting power
• Required area of elements is small enough to fit
  in the allowable area of 3/4 m2 without the
  possibility of inducing side lobes
• Polarization and power handling capability meets
  SPS requirements
• Inexpensive and uncomplicated to manufacture

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Transmitting Antenna

• Corporate Feeding
• Employs uniform amplification and phase shift to
  a 3x3 element subarray
• 5880 Duroid Substrate and copper rectangular
  patches

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Satellite Bus and Electronics
28V Bus
Terma Array Power Regulation Module
Terma Battery C/D Regulation Module
IRF E-Series DC-DC Converter
Power Transmission System (Solid State Amplifiers)
Misc. Components of Retro Directive Control and
Housekeeping
Silicon Solar Array
Saft MPS176065 Li-ion Battery

• The Saft MPS battery has a nominal energy of 480
  Wh and an end of charge voltage of 32.8 V
• DC-DC Converter, Regulation modules and battery
  have an efficiency of over 90
• Less than 6 Kg. for DC-DC Converter, Regulation
  modules and battery

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Thermal Management

• Goal is to ensure that equipment is kept within
  designated temperature ranges (-20C to 60)
• Hot Case Transmitting produces about 3 kW of
  heat
• Plan to transmit during eclipse
• Use loop heat pipes to transfer heat to radiator
  on bottom of satellite
• Use thermal storage with phase change material
• Cold Case Shaded by earth and not transmitting
• Use thermal energy stored from transmission time
  to heat electronics
• Use resistance heaters if additional heat is
  needed

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Thermal Desktop Image
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Transient Temperature Response
Heating of electronics during transmission with
assumed mass of 20 kg and assumed radiator size
of 0.25 m2.
Cooling of electronics after transmission, with
assumed mass of 20 kg and assumed radiator size
of 0.25m2.
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Retrodirective System

• Hardware Retrodirective Control Method
• Researched control technique that uses a 2nd
  harmonic transceiver to double and conjugate
  received pilot beam
• Requires that a receiving antenna be nested
  within the transmitting antenna array
• Requires a pilot signal of 2.9 GHz
• Software Retrodirective Control Method
• Use logic to establish conjugate phase of
  received pilot signal
• Use logic to implement phase conjugation and
  redirect transmit beam in the direction of the
  received pilot signal.
• Preliminary design and required components have
  been identified
• Method requires same antenna configuration as
  hardware method
• Frequencies of pilot signal less limited

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Retrodirective System
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Summary

• Determined solar energy data for a 35
  inclination orbit
• Determined power level of 2 kW required for
  transmitting detectable signal
• Plan to transmit during eclipse to meet thermal
  requirements
• Selected hardware components that meet power
  requirements
• Developed design of electronics hardware
• Developed preliminary design of satellite, but
  final design is to be determined with further
  analysis
• Gained knowledge of Thermal Desktop and can model
  accurately thermal behavior of satellite when it
  is updated.

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Plan for Spring 2010

• Integrate systems into a unified design
• Conduct trade studies for different system
  configurations.
• Maximize photovoltaic and antenna area while
  allowing sufficient space for radiators.
• Perform test demonstration of retrodirective
  system