So new its scarcely noticed, So old its almost forgotten

Introduction This is a new concept for space solar power It combines the very new and the very old

Professor David C. Hyland, Sc.D. Director, Space Science and Space Engineering Research Texas A&M University College Station, Texas, USA

dhiland@neo.tamu.edu

The New The next slide shows the new technology. Solar collectors and microwave transmitters can be printed on

a thin fabric. The collectors and transmitters are combined in modules

called collectennasTM.

Substrate layer

Transmitter

Solar cell Solar cell

Conductive coating (ground)

Power connectors

Printed Solar Collectors Printed Patch Antennae

Solar-Microwave FabricTM

The New

The Old The next slide shows the Echo satellite technology. The satellite is launched in a small container, then inflated to

form a large, hollow sphere.

The Old

Fabrication of the Power StarTM Solar-Microwave FabricTM is produced in oval strips The strips are joined to make the sphere

Meridonial SectorsSpherical Balloon

Deployment The Power Star is folded in a small container that is launched

in one launch vehicle. The container opens and the balloon is inflated

Packaging and Deployment

Small final angular velocity

The Basic Module The sphere is covered with collectennaTM modules arranged in

a randomized pattern This avoids grating lobes

Ground beacons give the desired power distribution on the ground

Each collectennaTM module senses the ground beacon radiation, amplifies it, and transmits it in reverse time.

This gives the best fit to the desired power distribution Multiple beams can be formed and shaped

Rectenna Beacons

Beacon Radiation

Microwave

Power

Printed microwave transmitter elements Printed solar array

elements

Random tiling prevents grating lobes

Substrate layer

TransmitterSolar cell Solar cell

Conductive coating (ground)

In each collectennaTM: Local processor 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!

Fundamental Power Shaping Concept The next two charts illustrate the power shaping concept as

first devised for acoustics

The very same time-reversal principle has been applied to accoustics. See Scientific American, November 1999.

The Acoustic Time-Reversal Mirror

Illustration of Power Shaping The collectennaTM operations are simultaneous. But we

illustrate one step at a time. The next chart shows a simulation of a flat phased array

receiving radiation from two beacons on the ground.

Recording 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 two point sources representing the beacons

Each pixel on this line segment is a separate recorder

When the beacon radiation reaches the line segment representing the phased array, each point on the line records the wave-form that it sees.

Illustration of Power Shaping (Continued) The next chart shows the transmission step Two spots of concentrated power, centered on the beacon

locations are created. If the phased array were infinitely large, the two point sources

would be matched exactly

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

Note the converging wave fronts

Each pixel on this line segment transmits the recorded signal in reverse time

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

A Better Shape The next chart shows that a spherical phased array would work

as well. A sphere gives flexibility collect power from any direction,

transmit power in any direction. No moving parts needed.

Nor must the phased array be flat!

Dynamic Stability of Power StarTM The next chart shows that surface errors or damage can be

compensated solely by electronic means. There is no control/structure interaction The system is

inherently stable

Error Compensation is purely electronic. There is no control/structure Interaction

System Dynamics Sensor measurements of array element position

errors

Array element deformation/

vibration

Dynamic feedback control

Actuator dynamics

Actuator commands

Actuator forces and torques

Electronic phase adjustment

Phased Array Gain

Undistorted radiation pattern

Disturbances

The Overall Concept The next chart shows a sketch of the overall concept We also list the important features

Substrate layer

Transmitter ~ 10cm

Solar cell Solar cell

~ 1 km

Conductive coating (ground)

Power connectors

meridonial sheets with power coupling

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.

Conclusion Power StarTM is launched as a small seed, then grows to a

mighty sphere. Although large, it uses the independent action of each small

part. It uses the very new to give new life to an old but beautiful

satellite design.

(The Latin means: Nature is greatest in the smallest things)

Natura in Minima Maxima

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Professor David C. Hyland

David C. Hyland, Sc.D. is Director, Space Science and Space Engineering Research, Texas A&M University.

Dave joined Texas A&M University on September 1, 2003 as Associate Vice Chancellor of Engineering, Associate Dean of the Dwight Look College of Engineering, holder of the Wisenbaker Chair of Engineering, Professor of Aerospace Engineering in the College of Engineering and Professor of Physics in the College of Science. Most recently, he assumed the position of Director of Space Science and Space Engineering Research for Texas A&M. His current research interests include adaptive control for aerospace vehicle applications. Prior to his joining Texas A&M University, Dave served as Professor with tenure and Chairman of the Aerospace Engineering Department at the University of Michigan. Dave earned his B.S., M.S., and Sc.D. degrees, in Aeronautics and Astronautics at Massachusetts Institute of Technology (MIT).