Template D402-T01 (06/27/2014, Rev -) *
Space Solar Power Workshop,
IEEE WiSEE, 2017
1
Tatiana Vinogradova, PhD
Northrop Grumman-Caltech
Space Solar Power Initiative
(SSPI)
Technology maturation
NG Aerospace Systems, Military and Civil Space
Approved for public release; NG17-2005, 9/29/17
Agenda
• Space Solar Power Initiative (SSPI) Introduction
• Research, technology development and maturation
• System consideration for ultra light approach
• Tile unit maturation and testing
• Manufacturing process development and improvement
• Conclusions
2 9/29/2017
Collaborators
Pilar Espinet-Gonzalez, Nina Vaidya, Tatiana A. Roy, Emily C. Warmann, Ali
Naqavi, Samuel P. Loke, Jing-Shun Huang, Alexander J. Messer,
Christophe Leclerc, Terry Gdoutos, Ali Hajimiri, Sergio Pellegrino, and Harry
A. Atwater
Approved for public release; NG17-2005, 9/29/17
Summary: SSPI is a multi-year research in the field of Space Solar Power Initiative conducted by Caltech team in collaboration with Northrop Grumman (NG) Aerospace and Mission Systems division
SSPI approach: • Enabling technologies developed at Caltech
• Ultra-light deployable space structures • High efficiency ultra-light photovoltaic (PV) • Phased Array and Power Transmission
• Integration of concentrating PV, radiators, MW
power conversion and antennas in single cell unit
• Localized electronics and control for system
robustness, electronic beam steering
• Identical spacecraft flying in formation
• Specific power >2000W/kg to be cost competitive
SSPI technology development effort includes incremental demonstrations at the laboratory and on-orbit
Space Solar Power Initiative (SSPI) Northrop Grumman – Caltech partnership
SSPI concept is to build ultra-light modular system compatible with
today’s launch costs
9/29/2017
3 Approved for public release; NG17-2005, 9/29/17
SSPI System Architecture Notional
4
10 cm x 10 cm Tile
Photovoltaics
Electronics
Antenna Strip, 1.5 m
wide 60m x60m Module Basic Structural Unit /
spacecraft
3km x 3km Power Station Formation Flying Modules
SSPI concept is build upon the following architectural elements: • Tile - base unit containing power generation (PV), DC-RF conversion (IC) and transmission (Antenna) with timing control
and thermal management
• Strip – next level of assembly and a basic folding unit
• Module – basic structural unit for deployment which is built of strips, (60 m x 60 m) ~ 300,000 Tiles
• SPS system - formation flying 2,500 Modules ~ 900,000,000 Tiles
Caltech PI’s: Dr. Sergio Pellegrino, Dr. Harry Atwater, Dr. Ali Hajimiri
SSPI key functionality verification can be done in phases
M. Arya, N. Lee, S. Pellegrino, Ultralight Structures for Space Solar Power Satellites, AIAA SciTech, 2016,
Image use with authors permission
Approved for public release; NG17-2005, 9/29/17
Ultra-light approach Research and technology development
5
• Ultra-light reflectors
• Solar cells
• Interconnects
• Radiation shielding
• Thermal design
• Assembly & alignment
Concentrating photovoltaic
• RF IC
• Antennas
• Phase control
• Thermal management
• RF link
• Rectenna
• Tile Prototype development
• Tiles and modules integration flow
• Automated assembly concept
• Thermal system modeling and
model validation
• System space qualification testing
• Ultralight composites
• Thermal performance
• Module deployment
• Tracking & pointing
• Mission design
• Orbits & maneuvering
Multidisciplinary collaboration between Caltech research groups and Northrop Grumman
Power transmission
Advanced System Integration and test
Space Structures and deployment mechanisms
M. Kelzenberg et al., Space Power Workshop, April, 2017
Approved for public release; NG17-2005, 9/29/17
SSPI Technology Development and
Manufacturing Road Map
6
SSPI system
SSPI Scaled
Demo Module Integration
(1MW system)
SSPI
manufacturing,
N tile units
CubeSat
integration
CubeSat
demo
On-orbit demo, LEO 50
360,000
Additional space applications
900,000,000
Mass production
Intermediate production
Pilot Production
SSPI
technology
development
SSPI
technology
ground demo
Product development
Technology
development
5
Product manufacturing
Product manufacturing
On-orbit demo, Scaled
• SSPI tile and system integration design is stable
• Key system characteristics and critical
manufacturing steps are identified
Additional space
applications
Program
launch
Design
performs as
expected
Project is in technology development / ground demonstration stage SSPI vision is to advance TRL level and capture design and manufacturing early in development
GEO orbit • Power conversion • Scaled module
deployment • Power transmission • Beam steering • Complete tile testing
• Scaled Deployment • Power conversion • Power transmission • Beam steering • Power receiving • Complete tile test
before launch
• All required technical validation
• Sample tile testing
Approved for public release; NG17-2005, 9/29/17
Space Solar Power Concept General considerations
7
Power Collection (DC) Photovoltaic system (PV)
Efficiency: 25% - 30%
End-to-end efficiency
Incident sunlight
Power Conversion (DC to RF)
Efficiency: 50% - 80%
Power transmission RF downlink
Efficiency: 50% - 80%
Power Collection Rectenna (RF to DC)
Efficiency: 85% - 95%
25%-30%
6%-20%
13%-27%
7%-21%
Key performance parameters Key components and efficiencies
• Power Density (BOL, EOL), [kW/kg] • Mass to area ratio, [g/m2] • Power Areal density, [kW/m2] • Stowed Vol. Power Density, [kW/m3]
• Synchronization and Power generation architecture
• Phase control performance • Power amplifier performance
• Transmitting antenna parameters (frequency, etc.)
• Maximum Power Density, [W/m2] • Transmission losses (attenuation,
diffraction, scattering, etc.).
• Receiving antenna parameters • Maximum Power Density, [W/m2] • Power Density (BOL, EOL), [kW/kg]
SSPI breakthrough parameter is power density at the collection and receiving stage
Approved for public release; NG17-2005, 9/29/17
Power Collection (1 of 2) SSPI System notional parameters
System parameter Tile Module Comments
Mass-to-area ratio, [g/m2] 80 102-120 Ref: M. Arya, et all, Ultralight Structures for Space Solar Power Satellites, AIAA SciTech, 2016
Power collection efficiency >25% >25% Combined CPV efficiency
Power density, BOL, [kW/kg]
>3.1 >2.4 DC generated on orbit per unit weight
Power Areal Density, [kW/m2]
>0.25 >0.25 M. Arya, N. Lee, S. Pellegrino, Ultralight Structures for Space Solar Power Satellites, AIAA SciTech, 2016
Stowed Volume Power Density, [kW/m3]
N/A ~ 700
System Area, [m2] 0.01 3600
System mass, [kg] 8x10-4 368-425 Module includes margin for support components
Total Power, BOL, [kW] >2.5x10-3 >9.1x102 DC generated on orbit
Radiation tolerance >0.85 >0.85 Fractional power output after exposure to 1015 1MeV electrons per cm2
Package Volume, [m3] N/A 1.18 1.5 m cylinder of 1m diameter
8 SSPI range of parameters for power collection
Approved for public release; NG17-2005, 9/29/17
Power Collection (2 of 2) Technology development: flexible light solar arrays
9
Enabling technologies of new generation for flexible solar arrays are demonstrated for
reduced mass, efficient packaging and deployability in space.
ATK, MegaFlex DSS ROSA
Parameter Mega Flex ROSA SLASR SSPI, Module
Solar Power Collection System Type Flat panel Flat panel Concentrators Concentrators
Power density, [kW/kg] 0.150 0.200 - 0.500 0.200-0.362 >2
Stowed Volume Power Density, [kW/m3] ~40 ~50 ~80 ~700
SSPI approach is to develop ultra-light flexible concentrating system and deployable space structures to reach breakthrough power density
Stretched Lens Array SquareRigger
(SLASR) prototype, ATK, NASA,
ENTECH , follow on SCARLET
design
Images credit: NASA
Approved for public release; NG17-2005, 9/29/17
SSPI Power Collection Ultra-light approach
10
SSPI Concentrating Photovoltaic Tile Concept Key CPV performance parameters
Concentrators and thermal
management technology
development
Technology focus areas: • Concentrators design
• Flexible thin film
specular reflectors
• Carbon Fiber mirrors
• Thermal management
• Collaborations:
• III-V Multi Junction Solar
cells advanced design
• Advanced glass coating
options
9/29/2017
• Power Density (BOL, EOL), [kW/kg] • Mass to area ratio, [g/m2]
• Power Areal density, [kW/m2] • Stowed Vol. Power Density, [kW/m3]
Ad
van
ced
co
ati
ng
an
d n
ew
gen
era
tio
n o
f ra
d.
hard
so
lar
cells
Cover glass development
Rad hard cell design
Thermal management
material development
Advanced concentrators
and thermal management
T. Vinogradova et al., Space Power Workshop, April, 2017
Approved for public release; NG17-2005, 9/29/17
SSPI Structural Design Module, ultra-light approach
11
Example,
coilable booms :
NG Astromast
• Design Considerations
– Minimize Weight (to reduce launch costs)
– Maximize Stiffness (to maintain sun-pointing accuracy)
– Maintain Flexibility (for compact packaging)
M. Arya, N. Lee, S. Pellegrino, Ultralight Structures for Space Solar Power Satellites, AIAA SciTech, 2016, Image use with authors permission
Coilable Boom Maintain Structure,
Control Deployment
Hub Store Electronics
Diagonal Cord Constrain Ends of Strips
Strip Support Tiles
Specific CPV power as a function of cord tension
Approved for public release; NG17-2005, 9/29/17
SSPI Structural Design Module Packaging Concept
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Flattened
Module with
Concentric
Squares
Fold along lines, alternating
between “Mountain” and
“Valley” folds
Pinch together
edges to form
star-like shape
Roll all four
arms into a
spiral
Wrapping
results in a
compact
cylindrical
packaging
60m x 60m Module can be folded into a 1m Diameter x 1.5m Tall Cylinder
M. Arya, N. Lee, S. Pellegrino, Ultralight Structures for Space Solar Power Satellites, AIAA SciTech, 2016, Image
use with authors permission
Approved for public release; NG17-2005, 9/29/17
SSPI Technology Maturation Tile development
13
Tile design characterization: - Functional - Vibration - Thermal balance - Thermal vacuum - Scaled deployment - Reliability characht. (subcomponents) - Power transmission, lab
Integration and test to qual level
Thermal Vibration Environmental Scaled Deployment Power conversion Performance
Tile prototype characterization:
Functional demo at ambient Concentrator design characterization Thermal evaluation at ambient Electrical performance Efficiencies: optical, PV, concentrating
Technology development and characterization
Demonstration and test in ops environment
Tile mockup: Mass budget Tile flattening spring demo Mechanical models update
Simulations: Optical Electrical Thermal Structural
Applied research
Flight demo: Thermal Vibration Environmental Scaled Deployment Power conversion Power transmission Beam steering Power receiving
Prototype
in Ops environment
System
qualification
Mission proven
Breadboard
in lab
Prototype in
Rep environment
Bread board
in rep environment
Proof of concept
Concept formulati
on
Basic
principles
Light weight, high efficiency, radiation-hard SSPI tile development road map
9/29/2017 Approved for public release; NG17-2005, 9/29/17
Optical characterization for CPV unit
9/29/2017
14
0 2 4 6 8 10 12 14 16 18 200
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
Concentartion ratioA
cc
ep
tan
ce
an
gle
at
90
%, [d
eg
]
Acceptance angle, scaled by reflectance vs concentration
Membrane mirror, LAPSS
CF mirror, LAPSS
T. Vinogradova et al., ‘Optical characterization of ultra-light photovoltaic concentrator for space power applications’, Space Power Workshop, April, 2017
• Tile unit was assembled at Caltech and tested at NG
Space solar factory facility
• NG Large Area Pulsed Solar Simulator (LAPSS)
capabilities:
• 0.1 and 0.5 degrees beam divergence angles in
the two orthogonal axes
• Uniform intensity field of pulsed light of an intensity
of 1 AM0 (at 1% accuracy)
• Experimental data confirmed optical performance
prediction and verified
• Key fabrication and evaluation steps were verified:
Consistent performance for preliminary contacts
Test uncertainties
Error budget for optical efficiency
Optical efficiency and acceptance angle
Test successfully demonstrated CPV tile functionality and provided the estimates on efficiency sensitivity to key fabrication errors
Approved for public release; NG17-2005, 9/29/17
15
SSPI Radiation environment GEO Orbit, 10 years mission analysis
TID vs depth curves with ceramic
shielding at IC locations
1
10
100
1000
0 10 20 30 40
Tota
l In
tegr
ated
Do
se [
MR
ads
(Si)
]
Shielding Thickness [mils ceramic]
SSPI, Parabolic mirror IC TID vs. Depth of Shielding
Top
Mid
Bot
P. Espinet et al., ‘Impact of Space Radiation Environment on Concentrator Photovoltaic Systems, PVSC, June, 2017
1 MeV e- equivalent fluence for vs.
front shielding (DDD analysis)
10-2
10-1
100
101
102
108
1010
1012
1014
1016
Energy, [Mev]
Inte
gra
l fluence,
[e-
cm
2]
Simulated integral spectra Trapped El,GEO orbit,10 year
AE8, 10 years
AP8, 10 years
ASP8, 10 years
• Trapped electrons and energetic solar protons from solar
events are a dominating factor at GEO environment
• SSPI radiation analysis is performed with NOVICE
simulation for preliminary trade studies for IC and PV
shielding options
• PV shielding is a critical parameter for SSPI W/g measure
and mission lifetime
• Collected experimental data on PV irradiation confirms
simulated results
GEO Integral specta for SSPI
analysis
Approved for public release; NG17-2005, 9/29/17
SSPI Manufacturing Development and process improvement
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• PV Fabrication in large quantities; substrate
reuse, optimizing manufacturing process for
cost reduction
• High radiation resistance PV development; PV
characterization
• Effective assembly and test with glass
protection, reflective coating and
interconnection
Flexible thin specular reflectors
Booms, tension cords, longerons
• Modular vacuum bag technology as an alternative
to produce very long booms at reduced production
costs
• Qualification of the production facility and
processes
• Customization for technical performance and supply
chain
• Radiation hardness
• Qualification and test of IC in mass production
Advanced concept development and implementation • Tiles, strips and modules integration flow and
automated assembly concept
• Automated approach for space qualification testing
• Optimizing the manufacturing process
Prototype development • Initial prototype as an auto assembly of the scaled
SSPI production
• Specularity performance for metallization
thicknesses; film properties variation in bulk
production, carbon fiber materials for
concentrators
• Metallization in tapered thicknesses in large
volumes
• Multilayer reflective coating practice for large
production
• High reflectance in-band, High emissivity out-
of-band, High thermal conductivity materials
• Concentrators shape fabrication process
III-V Multi Junction Solar cells, ELO technology
MW Power transmission, Integrated Circuits
Ultralight space structures and deployment mechanisms
Concentrators
SSPI Integration and test
Manufacturing process improvement areas with a high payoff Approved for public release; NG17-2005, 9/29/17
Conclusions SSPI strategy, demo opportunities
Near term technology demonstration opportunities:
• Tech maturation of tiles & structure, thermal vacuum testing
• Several working tiles targeted for a space demonstration
• Manufacturing demo for scaled module production
• Scaled system demonstrator
Caltech, Principal Investigators
• Dr. Sergio Pellegrino, Joyce and Kent Kresa Professor of Aeronautics and Professor of Civil
Engineering
• Dr. Harry Atwater, Howard Hughes Professor of Applied Physics and Materials Science Director, Resnick Sustainability Institute
• Dr. Ali Hajimiri, Thomas G. Myers Professor of Electrical Engineering and Professor of Medical Engineering
Caltech team of senior researchers, post doctoral scholars and graduate students
13
Northrop Grumman • NG brings expertise in developing and building highly
reliable space system
• NG is developing manufacturing capabilities as the project
transitions core technologies from development to testing
and production stage
NG expertise in the areas of: Microelectronic Devices, Solar
Arrays Products, Mirror Coating, Advanced Systems Concepts ,
ELO processing, Space Systems, Integration and test, Light
structures and deployment, System Engineering
Strategic partnerships, Strengthening NG Relationship with academia
Approved for public release; NG17-2005, 9/29/17
