Transcript Power Star
Global Prosperity Through SpaceBased Solar Power The Power StarTM Concept Prof. David Hyland Mech Aero – 2014 Hilton Philadelphia Airport Hotel September 8 -10, 2014 Also contributed at the International Conference on SBSP, Kobe, Japan, April 2014 So new it’s scarcely noticed, So old it’s almost forgotten 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 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 “collectennas”TM. The New Printed Solar Arrays Solar-Microwave Fabric Trans mitter Solar cell Power connectors Solar cell Conductive coating (ground) Substrate layer Printed Patch Antennae 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 Sectors Spherical 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 Negligible final angular velocity Packaging and Deployment 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 In each patch antenna: Local microprocessor records beacon radiation waveform Amplifies waveform and emits it back in reverse time. Transmitter Solar cell Exterior surface Solar cell Substrate layer Copper grid Power connector transceivers Power optimally matches desired power distribution on the ground. Rectenna Beacons Random Tessellation to prevent grating lobes No moving parts! Printed microwave transmitter elements Printed solar array elements 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 acoustics. 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 waveform 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! Solar radiation Localized Power Distribution S , B exterior surface illuminated by both sun and beacon External solar arrays power local external transmitters S, B S , B exterior surface illuminated by sun but no beacon S, B Beacon radiation External solar arrays power the local internal receiver/transmitters & they transmit power to the internal receiver/transmitters in sector S , B S, B S , B exterior surface exposed to beacon, but not the sun Exterior transmitters powered by the local interior S, B receiver/transmitters (that receive power from S , B ) S , B exterior surface shaded from both sun and beacon Do nothing Interior surface printed with -wave receiver/transmitters (possibly shorter wavelengths) 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! Dynamic Stability of Power TM Star • 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 Phased Array Gain Disturbances System Dynamics Undistorted radiation pattern Array element deformation/vibrat ion Sensor measurements of array element position errors Actuator forces and torques Dynamic feedback control Actuator dynamics Actuator commands Electronic phase adjustment The Overall Concept • The next chart shows a sketch of the overall concept • We also list the important features Summary Sketch of the Concept Random Tessellation to prevent grating lobes Unique features: Its structure is extremely simple and can be fit into many launch vehicle payload envelopes. ~ 1 km 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. Printed solar array elements It can optimally approximate any desired field distribution on the ground. Printed microwave transmitter elements It requires no in-space assembly or construction It has no control/structure feedback so the system is guaranteed dynamically stable. Transmitter Solar cell Solar cell w Substrate layer transceivers 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