The document discusses concepts for a space-based solar power satellite system including: 1) A 15km long satellite that would generate 3GW of power using concentrated solar panels and microwave transmission. 2) Use of robots and modular transmitter arrays to assemble and maintain the satellite components in space. 3) Preliminary economic analysis found generation costs could be less than 5 cents/kWh making the system competitive with other power sources.

1. Sun Tower Concept
15 kM bed length
3 GW output beam
< 5 cents/kW­Hr
$125B Fab Estimate
Microwave beam to
earth mounted
“Rectenna”

2. Introduction
Introduction
Laser Beam to Existing Photovoltaic
Solar Array

3. Satellite Concept of Operation
1. Concentrator focuses
sunlight on space­based
PV array
2. PV array powers laser diode
3. Laser diode pumps fibers
4. Light from fibers is fed to
optics and transmitted to Earth
7. Power is
6. DC electricity distributed to
is converted to AC consumers
5. Terrestrial PV
receiver array converts
sunlight to DC electricity

4. Transmitter Face and Robot
83,841,250 Radiating Elements
Microwave (5.8GHz) 2.141 GW Radiated
•Two robots placed
symmetrically on
transmitter’s frontside
•Robots move on a rail
connected at perimeter
and center
Robot assembles and
repairs transmitter modules

5. Solar Cell Efficiency vs Wavelength
1kW/m2
~ Sun on Earth
Typical earth
mounted solar
array has 14%
efficiency
Visible Light
(reference)
Example: Laser Diode Array achieves 40% with LASER SSP &
Photovoltaic ground Array

6. Economic and Market Factors ­ General Cost Findings
– For 1996, U.S.
• Generating costs for new plants averaged about 3.8 ¢/kWh (EIA, 1997)
– For ~ 2020, U.S.
•A “reference case” for generation costs in 2020 is ~ 3.2 to 3.3 ¢/kWh
– World Bank experts suggested an average generating cost, ~ 2020, for
rapidly growing economics, of ~ 5.5 ¢/kWh
Under following conditions:
• Deregulation of foreign electric power markets
• Resource inputs trade in a world market at world prices
• Globalization of investment and technology
• Interfuel competition holds costs down
10
SSP Economic & Market Analysis Team

7. Preliminary Observations ­ Market
Growth In Electric Capacity Supply
1995 ­ 2020 (GW)
695
1,043
1,738
China OECD Other Developing
World Energy Prospects to 2020, IEA, 1998
14
SSP Economic & Market Analysis Team

8. SPG Pointing Accuracy, Structural Control Trades
• Pointing
– Off pointing : % of capture (2 degrees of control)
– Surface accuracy requires active control
– 1­2o for PV concentrator cells
– Each concentrator needs its own control
– Disturbance while pointing may impact WPT
– Station keeping
• Lifetime (40 yrs)
– Rotating machinery
– Concentrator Materials
– Actuator control
Pat George

9. Robotics
• SSP must be managed by robotics
– Installation
– Perform maintenance
– Affect repairs
• All are imperative to achieve cost
objective of < 5 cents per kW­Hour

10. LEMUR
Legged Excursion Mechanical Utility Robot
LEMUR
A new type of autonomous n­pod walker
called LEMUR has been developed for
assembly, inspection, and maintenance.
This robot demonstrates multi­mode
operations (mobility, inspection, and
manipulation) with a modular and
multifunctional toolset.
LEMUR Configuration – Demonstrated fine manipulation
and tool based operations
– Examined payload identification
Stereo Cameras
methods
– Implemented fiducial markers for
encoding payload identification,
orientation, and characteristics
– Performed visual inspection of
4 DOF Hex Driver Leg
payloads and robots
4 DOF Gripper Leg
w/ in­line camera
(Palm­cam) 3 DOF Gripper Leg

11. LEMUR
Legged Excursion Mechanical Utility Robot
• Accomplishments
– Designed and integrated LEMUR mobile
platform
– Developed a three­fingered manipulator Three­
with compliant grasp adjustment for fingered
manipulation of fine/delicate payloads manipulator
with
– Developed a hex driver end­effector with
integrated
retractable foot
camera optics
– Developed a miniature macroscopic
imaging camera (Palm­cam) for
integration into grasping manipulator
– Developed algorithms and computer code
for stereo vision and pattern recognition
using wavelet decomposition of fiducials
– Demonstrated visual object and self­
inspection using the Palm­cam Hex driver with
retractable foot
• Current Work
– Developing software for autonomous
navigation, inspection, and manipulation
of target

12. Hyper Redundant Intelligent Systems
Description
•Develop small, identical robotic elements that can
accomplish tasks collectively that are well beyond the
capabilities of its individual members.
•Approach
•Utilize serpentine chain of linkages with integrated
computing, sensing, and power as testbed for
cooperative robotics executing construction, inspection,
and maintenance
Participants
NASA ­ Haith, Wright, Loch, Thomas
CMU ­ Howie Choset
Industry ­ Randy Sargent (Newton Labs)
Technology Elements
• Mechanism Configuration: advanced actuators,
packaging, lightweight structure, power,
biomimetic skin
• Single Robot Control: force and redundancy
control strategies, communication, simulation &
modelling of hyper­redundant systems
• Cooperative Robot Control: Autonomy;Mobility
planning in complex structures, payload strategies,
data sharing/sensing

13. Hyper Redundant Intelligent Systems
• Benefits
– Highly Redundant (> 7 DOF) serial
link manipulator chains
– Capable of long reach into highly
constrained spaces (trusses,
frames)
– Capable of prehensile grasping,
limbless locomotion
– Redundant to multiple joint failures
• Research Challenges
– Path and motion planning to
arbitrary locations in a complex 3D
structure using generalized voronoi
graph search

14. Assessing Technology Readiness Levels
System Test, Launch
& Operations TRL 9 Actual system “flight proven” through successful
mission operations
System/Subsystem TRL 8 Actual system completed and “flight qualified” through
Development test and demonstration (Ground or Flight)
TRL 7 System prototype demonstration in a space
Technology
environment
Demonstration
TRL 6 System/subsystem model or prototype demonstration
in a relevant environment (Ground or Space)
Technology
TRL 5 Component and/or breadboard validation in relevant
Development
environment
TRL 4 Component and/or breadboard validation in laboratory
Research to Prove
Feasibility environment
TRL 3
Analytical and experimental critical function and/or
Basic Technology
characteristic proof­of­concept
Research
TRL 2
Technology concept and/or application formulated
Basic principles observed and reported
TRL 1