So new it’s scarcely noticed,So old it’s almost forgotten

Principal Inventor:

D. C. HylandTexas A&M University

Also contributed at the International Conference on SBSP, Kobe, Japan, April 2014

A Revolutionary Concept for Space Solar Power

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Background

• All previous SPS concepts• Involve gigantic, complex, articulated structures• Contain numerous, perhaps 1000s, of moving parts• Require numerous launches• Require on-orbit fabrication/construction, usually robotic• Involve serious dynamic stability issues

• Power StarTM combines very new and very old technologies to obtain:

• The simplest possible structure• No moving parts (except electrons and photons)• One launch vehicle (A one-km system can fit into several

existing vehicles)• No on-orbit construction• Inherent dynamic stability and robustness

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Substrate layer

Transmitter

Solar cell Solar cell

Conductive coating (ground)

Power connectors

Printed Solar Arrays Printed Patch Antennae

Solar-Microwave

Fabric

The New

• Solar collectors and microwave transmitters are printed on a thin fabric in a randomized pattern.

• The collectors and transmitters are combined in modules called “collectennas”TM.

• The fabric collects solar energy, converts to microwaves and transmits it with adaptively formed beam(s) using an entirely localized algorithm. (Two modes of operation:

• Passive Mode: A cooperative target sends a low amplitude beacon signal

• Active Mode: The Fabric transmits a tracking signal and the return from the target serves as a beacon signal

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The Old: Echo Satellite Technology

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Meridonial SectorsSpherical Balloon

Balloon Fabrication

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Packaging and Deployment: One compact container, one launch

vehicle

Negligible final angular velocity

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Rectenna Beacons

Beacon Radiation

Microwave Power

Printed microwave transmitter elements

Printed solar array elements

Random Tessellation to prevent grating lobes

In each patch antenna:

Local microprocessor records beacon radiation waveform

Amplifies waveform and emits it back in reverse time.

Power optimally matches desired power distribution on the ground.

No moving parts!

Exterior surface

Substrate layer

TransmitterSolar cell Solar cell

transceivers

Copper grid

Power connector

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Illustration of beam shapingRecording the beacon signals, then amplifying them and playing them back in reverse time occur concurrently. To simplify the explanation, we illustrate these steps separately. First, consider the beacon propagation…

On this plane we have three point sources representing the beacons

Each pixel on the spherical surface is a separate recorder

When the beacon radiation reaches the surface each pixel representing a collectenna records the wave-form that it sees.

8The time-reversal principle was first applied to acoustics. See Scientific American, November 1999.

Now turn off the beacon and let each pixel on the surface re-transmit the wave-form it recorded - but in reverse time…

Note the converging wave fronts

Each pixel on the surface transmits the recorded signal in reverse time

The amplitude on the ground plane has three concentrations centered on the beacons. If the transmitting array were infinite in extent, these would be point concentrations.

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Beacon radiation

Solar radiation

,S B

,S B

,S B

,S B

Interior surface printed with -wave receiver/transmitters (possibly shorter wavelengths)

, exterior surface illuminated by both sun and beacon

External solar arrays power local external transmitters

, exterior surface illuminated by sun but no beacon

External solar array

S B

S B

s power the local internal

receiver/transmitters & they transmit power to the

internal receiver/transmitters in sector ,

, exterior surface exposed to beacon, but not t

S B

S B

he sun

Exterior transmitters powered by the local interior

receiver/transmitters (that receive power from , )

, exterior surface shaded from both sun and beacon

Do nothing

S B

S B

Localized Power Distribution

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Power Distribution - Summary• Each antenna transmits only if the beacon(s) radiation is

received.• Each transmitting antenna draws power from

• Solar cells in its immediate vicinity (within a few centimeters), or• Through the thickness of the “skin” from receivers on the inner surface

of the skin.

• Power transmission through the skin traverses a few centimeters or less. Each transmitter receives just a few Watts No high voltages, no large wires

• Power distribution to each antenna is local – there is no need for a complex power management system.

• Strictly local architecture means robustness against partial damage!

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~ 1 km

w

Printed microwave transmitter elements

Printed solar array elements

Random Tessellation to prevent grating lobes

Summary Sketch of the Concept

Unique features:

Its structure is extremely simple and can be fit into many launch vehicle payload envelopes.

It can gather solar power from any angle and beam power in any direction (s) without slewing or structural deformation.

It has no moving parts.

It can optimally approximate any desired field distribution on the ground.

It requires no in-space assembly or construction

It has no control/structure feedback so the system is guaranteed dynamically stable.

The operation of the phased array is adaptive so that even if severely damaged, the system can retain some level of useful performance.

Substrate layer

Transmitter

Solar cell Solar cell

transceivers

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An Extended Application:Placed at GEO, Power Star is easily designed to produce power densities that are safe for humans on the groundBut if an intruder should approach within just a few hundred kilometers, Power Star can be run in active mode and irradiate the target with enormous power density

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Rapidly Deployable Power Generation / Air and Missile DefenseAt a forward operating base, lay out Solar-Microwave “rugs”.

Whatever the mode of operation, the rugs need not be flat nor does one need a continuous sheet (there can be minor gaps)

For power generation, use only the solar cells. If receiving power from Power Star, engage transceivers

Substrate layer

Transmitter

Solar cell Solar cell

Conductive coating (ground)

Power connectors

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Rapidly Deployable Power Generation / Air and Missile DefenseUsing power direct from solar cells or another source, operate beam forming in active mode.

This means irradiate target, sense return and use as beacon signal. Beam forming proceeds as described for Power Star.

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