Design of a Millimeter Waveguide Satellite for Space Power Grid Brendan Dessanti Richard Zappulla Nicholas Picon Narayanan Komerath Experimental Aerodynamics and Concepts Group School of Aerospace Engineering

2 Conference 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”

3 Outline 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

4 Space 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/MEO for conversion

5 Space 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

6 Space Power Grid Architecture Deviations 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

7 Millimeter 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 Process 1.Define Need and Design Requirements from established SPG architecture 2.Determine preliminary spacecraft parameters and overall configuration 3.Calculate power and mass budgets 4.Develop waveguide subsystem and other subsystems (TCS, antennae…) 5.Develop spacecraft configuration

8 Millimeter Waveguide Satellite Design Defining the Need ParameterValue Orbit Altitude2000 km Design Frequency220 GHz Design Power60 MW Satellite Lifetime17 years Total Antennas (per satellite)3 Space-Space Antennas2 Ground-Space Antenna1 Delta II Launcher Class<6000kg Design Requirements Relay Satellite

9 Waveguide Satellite Configuration ParameterValue Space-Space Antenna Diameter 90 m Space-Ground Antenna Diameter 50 m Space orbit propulsion I sp 5300 s Antenna Mass/Unit Area0.05 kg/m 2 Preliminary Spacecraft Parameters Configuration Using initial configuration and parameters, subsystem mass budgets determined using traditional spacecraft design methods

10 Millimeter Waveguide Satellite Design Waveguide System Must Transmit Power from Receiving Antenna to Transmitting Antenna At Very High Efficiency Proposed Solution: Corrugated Waveguides Using HE 11 mode, Corrugated structures can be designed to be nearly lossless (Ohmic Losses) General Atomics Produces Corrugated Waveguides for various frequencies (including 220 GHz) General Atomics

11 Millimeter Waveguide Satellite Design Waveguide System ParameterValue Length Waveguide m Length Waveguide m Total Length38.8 m MaterialCopper MediumVacuum ModeHE 11 Corrugation Period0.66 mm Corrugation Width0.46 mm Corrugation Depth0.41 mm Diameter63.5 mm Frequency220 GHz Waveguide System Parameters ParameterValue Max Power Transmitted60 MW Attenuation0.001 db/10m Efficiency through Waveguide 0.99 Efficiency Waveguide- Antenna Junction 0.99 Total System Efficiency0.97 Power Loss1.8 MW Density Material8.94 g/cm 3 Wall Thickness2 mm Mass/Unit Length1.81 kg/m Mass70.3 kg

12 Millimeter Waveguide Satellite Design Antenna 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 the following 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):

13 X: 8.48 Y: X: 2.44 Y: Millimeter Waveguide Satellite Design Antenna Sizing Plot Airy Ring% PowerJ 1 ZeroskRkR kDkD 1 st Ring83.8% nd Ring91.0% rd Ring93.8% th Ring95.2% th Ring96.1%

14 Millimeter Waveguide Satellite Design Thermal Control System Limiting Factor Equilibrium Temperature Achieve High K using: 2 Part Separated Spacecraft Main Body

15 Millimeter Waveguide Satellite Design End-to-End Efficiency and Mass Analysis System/SubsystemMass (kg) Payload (3 antennas)734 Propulsion75 Attitude Control180 C & DH64 Thermal989 Electrical Power775 Structure and Mechanisms 571 Waveguide70 Communications64 Total Spacecraft Dry Mass 3422 Total Loaded Mass w/ Contingencies 4267 Efficiency ParameterValue 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 Efficiency0.79 End-to-End Efficiency*0.43 *Power beamed from ground to satellite 1, relayed to satellite 2, and beamed to ground

16 Technical and Economic Results Analysis: Waveguide Effect on NPV Trough Phase 1 Breakeven Occurs Before Satellite Lifetime Mass Estimate Comes In Under Previously Used Estimate Phase 1 Costs Very Small Relative to Full Architecture Phase 1 Launch Cost Not Crucial to Full Architecture

17 Millimeter Waveguide Satellite Design Summary 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

18 Overall 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

19 Questions?

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