Design of a Millimeter Waveguide Satellite for

Space Power Grid

Design of a Millimeter Waveguide Satellite for

Space Power GridBrendan DessantiRichard ZappullaNicholas Picon

Narayanan Komerath

Experimental Aerodynamics and Concepts Group

School of Aerospace Engineering

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Conference Papers from Our TeamConference Papers from Our Team

• B. Dessanti, R. Zappulla, N. Picon, N. Komerath, “Design of a Millimeter Waveguide Satellite for Space Power Grid”

• N. Komerath, B. Dessanti, S. Shah, “A Gigawatt-Level Solar Power Satellite Using Intensified Efficient Conversion Architecture”

• N. Komerath, B. Dessanti, S. Shah, R. Zappulla, N. Picon, “Millimeter Wave Space Power Grid Architecture 2011”

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OutlineOutline

• Introduction to the Space Power Grid• Space as a Dynamic Power Grid• Millimeter Waveguide Satellite Design

– Waveguide Subsystem– Antenna Subsystem– Thermal Control Subsystem– Mass and Efficiency Summary– Effect on Overall Architecture

• Waveguide Satellite Design Summary and Conclusions• Overall Conclusions

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Space Power Grid ArchitectureSpace Power Grid Architecture

Phase I• Constellation of LEO/MEO Waveguide Relay Sats• Establish Space as a Dynamic Power Grid

Phase II• 1 GW Converter Satellites – “Girasols”• Gas Turbine Conversion at LEO/MEO

Phase III• High Altitude Ultra-light Solar Reflector Satellites – “Mirasols”• Direct unconverted sunlight to LEO/MEOfor conversion

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Space as a Dynamic Power GridSpace as a Dynamic Power Grid

Use Space for synergy with terrestrial power sources

• Phase 1 generates revenue by using space as means of power exchange

• Makes terrestrial solar and wind more viable (and more green, by eliminating need for fossil fuel based auxiliary generators)

• Creates an evolutionary path• Early Revenue Generation• Modest Initial Investment

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Space Power Grid ArchitectureDeviations from Traditional Approaches

Space Power Grid ArchitectureDeviations from Traditional Approaches

• Use Primary Brayton Cycle Turbomachine Conversion of highly concentrated sunlight (InCA: Intensified Conversion)

Specific Power, s• Separate the collection of sunlight in high orbit from conversion

in low orbit Antenna Diameter

• Millimeter Wave Beaming at 220GHz Antenna Diameter

• Use Tethered Aerostats Efficiency Through Atmosphere

• Power Exchange with terrestrial renewable energy Cost to First Power Barrier

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Millimeter Waveguide Satellite DesignMillimeter Waveguide Satellite Design

Conceptual Design of Phase I SPG Satellite• What it must do?

– Receive and relay beamed power at multi-MW levels– Maximize efficiency– Minimize thermal losses– Minimize satellite mass launch costs

Conceptual Design Process1. Define Need and Design Requirements from established SPG architecture2. Determine preliminary spacecraft parameters and overall configuration3. Calculate power and mass budgets4. Develop waveguide subsystem and other subsystems (TCS, antennae…)5. Develop spacecraft configuration

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Millimeter Waveguide Satellite DesignDefining the Need

Millimeter Waveguide Satellite DesignDefining the Need

Parameter Value

Orbit Altitude 2000 km

Design Frequency 220 GHz

Design Power 60 MW

Satellite Lifetime 17 years

Total Antennas (per satellite) 3

Space-Space Antennas 2

Ground-Space Antenna 1

Delta II Launcher Class <6000kg

Design Requirements

Relay Satellite

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Waveguide Satellite ConfigurationWaveguide Satellite Configuration

Parameter Value

Space-Space Antenna Diameter

90 m

Space-Ground Antenna Diameter

50 m

Space orbit propulsion Isp 5300 s

Antenna Mass/Unit Area 0.05 kg/m2

Preliminary Spacecraft Parameters

Configuration

Using initial configuration and parameters, subsystem mass budgets determined using traditional spacecraft design methods

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Millimeter Waveguide Satellite DesignWaveguide System

Millimeter Waveguide Satellite DesignWaveguide System

Must Transmit Power from Receiving Antenna to Transmitting Antenna At Very High Efficiency

Proposed Solution: Corrugated Waveguides• Using HE11 mode, Corrugated structures can be designed to be nearly

lossless (Ohmic Losses)• General Atomics Produces Corrugated Waveguides for various

frequencies (including 220 GHz)

http://www.ga.com/fusionproducts/microwaves/SCWaveguide/index.phpGeneral Atomics

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Millimeter Waveguide Satellite DesignWaveguide System

Millimeter Waveguide Satellite DesignWaveguide System

Parameter Value

Length Waveguide 1 18.5 m

Length Waveguide 2 20.3 m

Total Length 38.8 m

Material Copper

Medium Vacuum

Mode HE11

Corrugation Period 0.66 mm

Corrugation Width 0.46 mm

Corrugation Depth 0.41 mm

Diameter 63.5 mm

Frequency 220 GHz

Waveguide System Parameters

Parameter Value

Max Power Transmitted 60 MW

Attenuation 0.001 db/10m

Efficiency through Waveguide

0.99

Efficiency Waveguide-Antenna Junction

0.99

Total System Efficiency 0.97

Power Loss 1.8 MW

Density Material 8.94 g/cm3

Wall Thickness 2 mm

Mass/Unit Length 1.81 kg/m

Mass 70.3 kg

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Millimeter Waveguide Satellite DesignAntenna Sizing Derivation

Millimeter Waveguide Satellite DesignAntenna Sizing Derivation

Fraunhofer Diffraction at a circular aperture can be represented by the Bessel Function:

Solving for the first zero (first ring of airy disc), and using geometry gives thefollowing relationship governing transmitter and receiver diameter and frequency:

Where:

From the Rayleigh Limit, the amount of power that can be received is found using the Bessel Function (84% for the first zero/ring):

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X: 8.48Y: 0.952

X: 2.44Y: 0.838

Millimeter Waveguide Satellite DesignAntenna Sizing Plot

Millimeter Waveguide Satellite DesignAntenna Sizing Plot

Airy Ring % Power J1 Zeros kR kD

1st Ring 83.8% 3.83 1.220 2.44

2nd Ring 91.0% 7.02 2.233 4.47

3rd Ring 93.8% 10.17 3.238 6.48

4th Ring 95.2% 13.32 4.241 8.48

5th Ring 96.1% 16.47 5.243 10.49

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Millimeter Waveguide Satellite DesignThermal Control System

Millimeter Waveguide Satellite DesignThermal Control System

Limiting Factor Equilibrium Temperature

Achieve High K using:2 Part Separated Spacecraft Main Body

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Millimeter Waveguide Satellite DesignEnd-to-End Efficiency and Mass AnalysisMillimeter Waveguide Satellite Design

End-to-End Efficiency and Mass AnalysisSystem/Subsystem Mass (kg)

Payload (3 antennas) 734

Propulsion 75

Attitude Control 180

C & DH 64

Thermal 989

Electrical Power 775

Structure and Mechanisms

571

Waveguide 70

Communications 64

Total Spacecraft Dry Mass

3422

Total Loaded Mass w/ Contingencies

4267

Efficiency Parameter Value

Efficiency Through Atmosphere

0.90

Ground Receiver Capture Efficiency

0.95

Satellite Receiver Capture Efficiency

0.95

Space Receiver Antenna Efficiency

0.90

Space Transmitter Antenna Efficiency

0.90

Efficiency of Waveguide System

0.97

Total Spacecraft Efficiency 0.79

End-to-End Efficiency* 0.43

*Power beamed from ground to satellite 1, relayed to satellite 2, and beamed to ground

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Technical and Economic Results Analysis:Waveguide Effect on NPV Trough

Technical and Economic Results Analysis:Waveguide Effect on NPV Trough

Phase 1 Breakeven Occurs Before Satellite LifetimeMass Estimate Comes In Under Previously Used Estimate

Phase 1 Costs Very Small Relative to Full ArchitecturePhase 1 Launch Cost Not Crucial to Full Architecture

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Millimeter Waveguide Satellite DesignSummary and Conclusions

Millimeter Waveguide Satellite DesignSummary and Conclusions

Does the Design Close?• Sizing estimate fits within bounds of SPG economic model

• Satellite efficiency values are sufficient to provide power at reasonable cost to achieve breakeven in 17 year satellite lifetime

• No anticipated technical show stoppers to millimeter waveguide spacecraft development

YES

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Overall Conclusions from all 3 PapersOverall Conclusions from all 3 Papers

"The problems of the world cannot possibly be solved by skeptics or cynics whose horizons are limited by the obvious realities. We need men who can dream of things that never were." – John F. Kennedy

• Conceptual Design of Phase 1 Waveguide Satellite Refined

• Conceptual Design of Phase 2 Girasol 1 GW Converter Satellite Established

• SPG Architecture Updated With Large Improvements and Reduced Uncertainty

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Questions?Questions?

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