The document summarizes the design of a space-based solar power system. It proposes using five satellites in geosynchronous orbit to collect and transmit solar power to five ground stations via microwave beams. Each satellite would have a large solar concentrating structure and transmitter to beam 1 GW of power to Earth. The design aims to meet requirements to transmit 1 GW of power by 2040 for under $21 billion.
4. RFP Requirements
Design a space based solar power system that can:
Transmit 1 GW of power to Earth
Be fully operational by 2040
Cost under $21 billion
Be safe and reliable
4
6. Basic Design Five satellites and five
ground stations
Each satellite in GEO
Mirrors always facing the
sun
Parabolic shape
Center cut out since solar
panels block it
5 to 1 concentration factor
Copper transmission
cables from solar array to
transmitter
Rotating Transmitter
2 Communications buses
6
7. Dimensions
Solar Concentrating System
Radius: 461 m
Cutout Radius: 186 m
Depth: 137 m
Cutout depth: 21 m
Solar Array
Radius: 186 m
Distance from mirrors: 388 m
Transmitter
Radius: 90 m
Communications bus
2.5 m x2.5 m x 1.5 m
7
8. Mass Estimates
Component Total Mass (kg)
Communications 120
SpaceBots 960
Copper Transmission Cable 13,500
Structure 31,300
Thrusters/Propellant 22,300
Reaction Wheels/Motors 12,500
Solar Panels 179,000
Transmitter 13,400
Propellant (Satellite) 91,250
Magnetrons 24,000
Mirrors 146,600
Total for one satellite 537,370
Total for SPOC 2,686,850
8
27. Overview
Refueling satellite placed in LEO
Payloads launched into LEO
Orbital Transfer Vehicle docks with and carries
payload to GEO on a spiral transfer
Reaction wheels counteract rotating transmitter
Hall Effect thrusters provide station-keeping
27
28. European Space Agency’s Automated Transfer Vehicle
Modification Specifications
Mass 13,336 kg
Payload Up to 46,000 kg to GEO
Attitude and Control Thrusters Busek BHT-600 Hall Effect Thrusters
Main Engines High Isp Nested Hall Effect Thrusters
Nuclear Reactor SAFE-400 Space Fission Reactor
Propellant Up to 5,495 kg of Krypton
28
29. Refueling Satellite
Pentagonal prism hub with five propellant tanks docked to it using
ATV docking system
ATVs dock with propellant tanks to refuel
Each tank carries 96,000 kg for a total of 480,000 kg
Located in 1,000 km circular orbit at zero inclination
Tanks coated in optical solar reflectors to reduces pressure to minimize
leakage
29
30. Spiral transfer
Time of flight varies for mass of the payload
Payload Mass (kg) Round Trip Time (days)
Propellant 45,612 163
Magnetrons 24,002 115
Solar Panels/Transmitter/Reaction Wheels 25,550 119
Solar Panels 37,577 145
Mirrors 42,680 156
Transmitter 4,618 73
Structure/Robots/Communications/Thrusters 30,000 128
Power Cable/Mirrors 37,214 144
Refueling Station Propellant Tank 98,500 99 (no return trip)
•Total time of flight to transfer all payloads to GEO is 6.7 years
•Time of flight and propellant requirements verified with STK; maximum error within
0.8%
•Total propellant required is 478,470 kg of krypton 30
34. Station-Keeping
Maneuver Burn Time Delta-V per burn
De-spin reaction wheels 47.3 minutes every 52.1
days
0.0109 m/s
E-W station-keeping 56 minutes, twice per day
at 6AM and 6PM
0.14 m/s
E-W station-keeping 5.7 minutes at midnight
every 60 days
0.006 m/s
N-S station-keeping 16 hours at 6AM every 60
days
2.5 m/s
•Station-keeping propellant mass is 57,770 kg per satellite
•Thrusters magnetically shielded to greatly reduce erosion (approx. 600 times
less) [4.1]
•Each satellite will carry 60,000 kg of propellant for station-keeping during
construction
34
39. Command and Data Handling
RAD750 single-board computer by BAE Systems Electronic
Solutions
Altair HB+ star tracker by Surrey Satellite Technologies
SSOC-A60 sun sensor by Innovative Solutions In Space
Thrusters and reaction wheels control
39
40. Communications
Ku-band
12.5 GHz downlink
14.0 GHz uplink
Ground station in Jupiter, Florida + backup
Frequency division multiple access (FDMA)
40
Google maps
41. Communications
Spacecraft antenna
2.4 m diameter parabolic
reflector offset feed by Av
Comm
deployable
• Ground station
antenna
– 2.4 m diameter parabolic
reflector offset feed by
Skyware Global
[5.2][5.1]
41
42. Link Budget
Data rate = 12 kbps
4kbps - commands
8 kbps - health and telemetry data
Margin = 34.72
enough to account for rain attenuation
42
46. Overview
Power Management and Distribution
Satellite Power Consumption – Collection
Satellite Power Consumption - Eclipse
Thermal Trade Study
Solar Concentration Factor Selection
Photovoltaic Thermal Control System Configuration
Thermal Control System Summary
46
47. Power Management and Distribution
Electrical Power System Schematic
• High Voltage,
Long Distance
47
48. Satellite Power Consumption - Collection
*** Not an actual power mode for satellite, validation purposes only
Component Quantity
Power Requirement For Mode (W)
Radiation
Pressure
Control
Burn
Longitudinal
& Inclination
Control Burn
Reaction
Wheel De-
Spin Control
Burn
Max Possible
Power
Draw***
Star Trackers 4 17 17 17 34
Sun Sensor 6 1 1 1 2
Spacecraft Antenna 2 38 38 38 76
Onboard Computer 2 5 5 5 10
CC&DH Total 61 61 61 122
Electric Thrusters 45 240,000 520,000 60,000 900,000
Reaction Wheels 10 3,500,000 3,500,000 3,500,000 3,500,000
Propulsion Total 3,740,000 4,020,000 3,560,000 4,400,000
Total Power 3,740,061 4,020,061 3,560,061 4,400,122
48
49. Satellite Power Consumption – Eclipse
Component Quantity Power (W)
Star Trackers 4 17
Sun Sensor 6 1
Spacecraft Antenna 2 38
Onboard Computer 2 5
CC&DH Total 61
Electric Thrusters 45 -
Reaction Wheels 10 -
Propulsion Total 0
Total Power 61
49
50. Thermal Trade Study
Solution
Technology
System
Type
Description Issues Conclusion
Pure
Conduction
PTCS
Conductive material to dissipate
heat
● Heat flux too high
● Likely to melt
Impractical
Heat Pipes PTCS
Uses pipes with fluids that cool PV
cells with vapor/condensing
● Small scale
● Only low thermal loads
Infeasible
Fluid Loop ATCS
Pumps system with fluid to
remove heat
● Expensive to launch
● Potential leaks
Impractical
Passive
Radiation
PTCS
Passively managed with paints and
coatings
● Low conc. factor
Viable, for low
conc. factor
50
51. Solar Concentration Factor Selection
Solar concentration factor over
temperature range to determine
optimal Photovoltaic Thermal
Control System configurations.
• Static Heat Balance
• Concentration Factor of 5 : 1
• PV Cells Temp ≈ 60 ̊C
-250 -200 -150 -100 -50 0 50 100 150 200 250
0
5
10
15
20
25
30
Solar Concentration Factor Over Temperature Range
Solar Collector Temperature (ºC)
SolarConcentrationFactor
X: 62
Y: 5.003
▪ Design Point
–– Optimal PV Regime
(Currently)
51
53. Thermal Control System Summary
Location Component
Emissivity
(ɛ)
Function
Solar Panel
Rear (Sun-
Facing)
Optical Solar
Reflectors
0.92
High emissivity surface component
Reflect incoming solar rays
Facilitate thermal radiation
Solar Panel
Front Main
(Reflector-
Facing)
PV Laminate 0.75
Emissivity surface coating
Facilitate thermal radiation
Reflector Rear
Face
None 0.53
The Mylar film reflector will
naturally radiate thermal loads
without any PTCS assistance
53
54. Thermal Control System Summary
Optical Solar Reflector PV Laminate None
PV - Sun Facing Reflector BackPV - Reflector Facing
* Locations highlighted in yellow
54
57. Introduction
Five ground power receiving stations (GPRS)
Rectenna design that is safe, cost effective, and least
obstructive to the general population
57
61. Ground Station Design Cont.
Visualization of a ground power receiving station [7.2]
61
62. Ground Station Locations
Federal Lands Nature Topography Weather
National Recreation Areas Land and water Open mountains Windstorms
American Indian
Reservations
National Forests Hills Hail
Military Reservations Marsh Vegetation Mountains Thunderstorms
Other Federal Lands Wetlands Sheet Rainfall
Endangered species habitat Acid Rainfall
62
74. Tug (ATV)
Payload Number Number of Tugs Needed Components Total Mass (kg) Time of Flight (round
trip, in days)
1 1 Propellant (ATVs) 98,500 99
2 2 Robonauts/
Communications/Structure/
Thrusters/Propellant
60,000 128
3 2 Solar Panels 75,150 145
4 2 Solar Panels 75,150 145
5 2 Solar Panels/
Transmitter/
Reaction Wheels
51,000 119
6 1 Transmitter 9,300 73
7 1 Magnetrons 24,000 115
8 2 Propellant (Satellite) 91,250 163
9 2 Power Cable/Mirrors 74,500 144
10 2 Mirrors 85,400 156
74
75. ATV Docking
Used on current ATV
Equipped with guidance
system to direct ADA
into PDA
ATV has ADA
Refueling satellite has 5
PDAs
Payload containers have
ADA and PDA (one on
each end)
3rd IAASS Conference - 4 -
“Building a safer space together”
ATV to ISS docking using th
ISS docking
port: PDA
ATV Docking
system: ADA
cone
socket
Grooves &
Latch stops
Probe
head
latches
Docking system [8.9]
75
77. Launch Timeline
56 total launches (6 Ariane 5, 50 Falcon Super Heavy)
First satellite with ATVs total of 426 days (2031) to
launch
Satellites 2-5 average of 392 days to launch per satellite
Total of 6.4 years to fully launch all satellite
components, 6.7 (late 2036) years for all components
to be in GEO
77
79. Risk Assessment
Number 1 2 3 4 5
Probability of
Occurrence
Very low Low Moderate High Very High
Not expected
to occur
Less likely
than not to
occur
May or may
not occur
More than
likely to occur
Expected to
occur
Impact on
Mission
Negligible Minor Moderate Significant Severe
Little to no
impact
Slight impact
but system still
functional
close to
intended
Medium
impact;
System
functional as a
whole but less
than intended
Parts of
system not
functional;
Loss of
mission
objective
Total system
and mission
failure
Total Risk Weight = Probability of Occurrence x Impact on Mission
79
80. Overall Risk
Probability
5 Very High 1
4 High
3 Moderate 2 1
2 Low 2 7 6 3 2
1 Very Low 4 1 2
Very Low Low Moderate High Very High
1 2 3 4 5
Impact
Mitigated risk by:
• Multiplicity
• Redundancy
• Buffers
• Factoring in additional costs
80
81. Cost Analysis
Determined raw materials costs for each subsystem
Applied Advanced Missions Cost Model (AMCM) for
items that needed to be research and developed
further
Applied cost estimating relations (CER) for parametric
cost estimation for items that needed to be
manufactured after raw materials were purchased
81
82. Project SPOC Costs
Subsystem Total Cost ($FY13)
Structures 29,284,800
Power Generation and Transmission 812,770,000
Orbit Transfer, Attitude
Determination, and Station Keeping 1,769,129,000
CC&DH 12,575,000
Spacecraft Power and Thermal
Systems 22,615,800
Ground Power Receiving Station 2,079,521,900
Launch Services 13,440,000,000
Research and developmentcosts 2,198,250,000
Manufacturing costs 18,937,270
Total 20,383,000,000
82
87. Component Dimensions
Mirror module (377/satellite)
Mirror Truss
1.1 m side length (hexagon)
388 kg
3.14 m2
25 m length (0.75 m stowed)
0.25 m diameter
Thin film reflector segment 25.35 m side length (hexagon)
1640 m2
Frame truss (136/satellite) 60 m length
1.121 m diameter
3.85 kg/m
Backbone Segments (4) 300 m each
Connecting Trusses (4) 375 m each
Overall Structure
Outer Rim
Inner Rim
Radius – 461.2 m
Depth – 137 m
Cutout Depth – 21.5 m
Solar Array Radius – 182.6 m
Focal Length 388.15 m
2900 m circumference
1150 m circumference 87
90. Best Research-Cell Efficiencies
2. Table from Kazmerski, Lawrence, “Best Research-Cell Efficiencies” ,Rev 4-2011, National Renewable
Energy Laboratory, March 2011 90
91. Magnetron Subarray Density
Step % of Max
Power Density
Subarrays Magnetrons/
Subarray
Number of
Magnetrons
Outer Radius
of Step Ring
(m)
1 100% 19 443 8610 24.879
2 83.33% 24 369 8782 37.101
3 66.67% 19 295 5741 44.671
4 55.56% 24 246 5854 52.469
5 44.44% 31 197 6038 61.071
6 33.33% 31 148 4528 28.602
7 25% 12 111 1391 71.457
8 22.22% 31 98 3019 77.992
9 16.67% 43 74 3191 86.367
10 11.11% 20 49 990 90
Total 255 48144
91
92. Solar Cell Band Gaps
Substrate Band Gap (eV) Max.
Wavelength
(nm)
GaInP2 1.8 689.28
GaAs 1.43 867.62
Ge 0.67 1851.79
92
94. ATV Appendix
High Isp NHT engine (per unit) [4.2] Isp: 5000s
Thrust: 6.1 N
Efficiency: 65%
Power consumption: 200 kW
Mass: 280 kg
Busek BHT-600 thruster (per unit) [4.3] Isp: 1585 s
Thrust: 42 mN
Efficiency: 49%
Power consumption: 600 W
SAFE-400 Fission Reactor (per unit) [4.4] 400 kWt
200 kWe
540 kg
Krypton Propellant ATV Maximum 5,495 kg
94
95. ATV Appendix
Payload Propellant Round Trip (kg)
Propellant 5,493
Magnetrons 3,526
Solar Panels/Transmitter/Reaction Wheels 3,663
Solar Panels 4,763
Mirrors 5,228
Transmitter 1,761
Structure/Robots/Communications/Thrust
ers
4,073
Power Cable/Mirrors 4,730
Refueling Station Propellant Tank 4,091 (no return trip)
95
96. Payload Round Trip Time (days)
Propellant 163
Magnetrons 115
Solar Panels/Transmitter/Reaction Wheels 119
Solar Panels 145
Mirrors 156
Transmitter 73
Structure/Robots/Communications/Thrust
ers
128
Power Cable/Mirrors 144
Refueling Station Propellant Tank 99 (no return trip)
ATV Appendix
96
97. Refueling Satellite Appendix
5 Titanium 6Al-4V fuel tanks 2 mm thick, interior volume
530 m3 carry 96,000 kg krypton each
Spacecraft bus is pentagonal prism with a PDA on all 5
sides for propellant tanks to dock with
Tanks will be coated with optical solar reflectors to keep
maximum temperature at 150 K
Orientation will remain in the plane of the ecliptic to
minimize surface area exposed to the Sun
Busek BHT-1000 [4.3] Isp: 1,750s
Thrust: 58 N
Power consumption: 1 kW
Mass: ~5 kg
97
98. Station-Keeping Appendix
NASA-300M thrusters [4.5] Isp: 3,220s
Thrust: 1.13 N
Efficiency: 63%
Power consumption: 20 kW
Mass: ~15 kg
Reaction Wheels Aluminum
0.75 m radius
0.23 m height
3,500 RPM
98
100. References
[4.1] Mikellides, Ioannis G., Katz, Ira, Hofer, Richard R., and Goebel,
Dan M., “Magnetic shielding of walls from the unmagnetized ion beam
in a Hall thruster”, Applied Physics Letters, Jan 2013.
[4.2] Space Mission Analysis and Design, Microcosm Press, CA, pp 560.
[4.3] “Low Power Hall Effect Thrusters”, Busek, 2012.
[http://www.busek.com/index_htm_files/70008510_revA.pdf. Accessed
02/15/2013].
[4.4] Poston, David I., Kapernick, Richard J., and Guffee, Ray M.,
“Design and Analysis of the SAFE-400 Space Fission Reactor”, AIP
Conference.
[4.5] Kamhawi, Hani, Haag, Thomas W., Jacobsen, David T., and
Manzella, David H., “Performance Evaluation of the NASA-300M
20kW Hall Effect Thruster”, 47th AIAA/ASME/SAE/ASEE Joint
Propulsion Conference and Exhibit, Aug. 2011.
100
102. References
[7.1] “Satellite Power System,” DOE/NASA Concept Development and
Evaluation Program, DOE/ER-0023, Oct. 1978.
[7.2] “Cutting the cord: ISTF-07.” Mainland High School ISTF. 2007.
[http://mainland.cctt.org/istf2008/rectennas.asp Accessed 1/19/13.]
[7.3] Blackburn, J. B., Bavinger, B. A., “Satellite Power System (SPS)
Mapping of Exclusion Areas for Rectenna Sites,” DOE/NASA Concept
Development and Evaluation Program, HCP/R-4024-10, Oct. 1978.
102
103. References
[8.1] Arianespace, “Ariane 5 User’s Manual, Issue 5 Revision 1,” Arianespace, Washington, DC, July 2011.
[8.2] Wertz, R. J., Everett, D. F., and Puschell, J. J. (eds.), Space Mission Engineering: The New SMAD, Microcosm Press, Hawthorne,
CA, 2011, pp. 859, 862.
[8.3] United Launch Alliance, “Atlas V Launch Services User’s Guide, Revison 11,” United Launch Alliance, Littleton, CO, March 2010.
[8.4] United Launch Alliance, “Delta IV Payload Planners Guide,” United Launch Alliance, 06H0233, Littleton, CO, September 2007.
[8.5] Space Exploration Technologies, “Falcon 9 Launch Vehicle Payload User’s Guide, Rev 1,” Space Exploration Technologies, SCM
2008-010 Rev. 1, Hawthorne, CA, 2009.
[8.6] Andrews Space & Technology, “Expendable Launch Vehicles,” Andrews Space & Technology, 2001.
[http://www.spaceandtech.com/spacedata/elvs/elvs.shtml. Accessed 11/30/12.]
[8.7] Space Exploration Technologies, “Falcon Heavy Overview,” Space Explorations Technologies, Hawthorne, CA, 2012.
[http://www.spacex.com/falcon_heavy.php. Accessed 11/30/12.]
[8.8] Strickland, J.K. Jr., “The SpaceX Falcon Heavy Booster: Why Is It Important?,” National Space Society Blog, 2011.
[http://blog.nss.org/?p=3080. Accessed 2/22/13.]
[8.9] European Space Agency, “The Russian Docking System and the Automated Transfer Vehicle: a safe integrated concept” from
“Stages to docking tonight,” ESA ATV blog, 28 March 2012, [http://blogs.esa.int/atv/2012/03/28/stages-to-docking-tonight/. Accessed
4/3/13.]
103