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The system architecting process for a solar power satellite concept
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The system architecting process for a solar power satellite concept
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Content
THE SYSTEM ARCHITECTING PROCESS FOR A
SOLAR POWER SATELLITE CONCEPT
by
Joseph Grady Bidwell
A Thesis Presented to the
FACULTY OF THE VITERBI SCHOOL OF ENGINEERING
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
MASTER OF SCIENCE
(ASTRONAUTICAL ENGINEERING)
December 2006
Copyright 2006 Joseph Grady Bidwell
ii
Table of Contents
List of Tables.......................................................................................................................................... iii
List of Figures ........................................................................................................................................ iv
Abstract .................................................................................................................................................. vi
1.0 Introduction ........................................................................................................................................1
2.0 Solar Power Satellite Concepts...........................................................................................................1
2.1 1979 NASA SPS Reference Architecture......................................................................................2
2.2 Sun Tower and Solar Disk.............................................................................................................5
2.3 Interplanetary Transport and Lunar Power Beaming.....................................................................6
3.0 System Architecting Process..............................................................................................................7
3.1 Lessons Learned and Relevant Heuristics .....................................................................................7
3.2 Strategic Decisions and Choices..................................................................................................10
3.3 Defining the System ....................................................................................................................12
3.4 Concept Production and Evaluation Process ...............................................................................14
4.0 Recommended SPS Concept............................................................................................................17
4.1 SPSS Mission Concept................................................................................................................17
4.1.1 Why do GEO satellites require fuel?....................................................................................20
4.1.2 Challenges for SPSS .................................................................................................................21
4.2 Power Beaming System...............................................................................................................22
4.2.1 Laser System Requirements and Design Options ................................................................23
4.2.2 Laser System Design and Sizing ..........................................................................................28
4.3 Power Rectification Analysis and Design....................................................................................31
4.3.1 Solar Cell Response to Laser Illumination ...........................................................................32
4.3.2 Solar Cell Response to Pulsed Laser Illumination ...............................................................34
4.4 SPSS Spacecraft Bus Design.......................................................................................................37
4.4.1 Power Generation.................................................................................................................37
4.4.2 Energy Storage .....................................................................................................................41
4.4.3 Thermal Control ...................................................................................................................42
4.4.4 Attitude Determination and Control.....................................................................................43
4.4.5 Propulsion System................................................................................................................44
4.4.6 Structures and Mechanisms..................................................................................................45
4.4.7 Communications & Command and Data Handling..............................................................46
4.5 SPSS Mission and Operation Modes...........................................................................................46
4.6 Cost Estimation............................................................................................................................48
5.0 Conclusions and Further Study.........................................................................................................49
Works Cited............................................................................................................................................52
Appendix A ............................................................................................................................................55
iii
List of Tables
Table 1: Experimentally tested solar cell efficiencies with different incident laser wavelengths
15
........25
Table 2: Laser power calculation............................................................................................................31
Table 3 Cell types test with RF FEL, inductive FEL, and CW laser light
31
...........................................35
Table 4: Measured cell efficiency response to inductive FEL format
31
..................................................36
Table 5: Cell efficiency response to RF FEL laser light
31
......................................................................36
Table 6: Preliminary SPSS power budget ..............................................................................................38
Table 7: Solar array sizing calculation ...................................................................................................39
Table 8: SPSS Cost Estimate..................................................................................................................49
iv
List of Figures
Figure 1: NASA's 1979 SPS Reference Architecture by Peter Glaser
11
..................................................3
Figure 2: Japanese SPS 2000 Concept
35
...................................................................................................5
Figure 3: Mankins' Sun Tower and Solar Disk Concepts
33
......................................................................5
Figure 4: Interplanetary transport, Solar Clipper
33
...................................................................................6
Figure 5: Photovoltaic Lunar Synchronous SPS Transmitter and Lunar Receiver Dish
41
........................7
Figure 6: Space-based SPS System Definition Diagram........................................................................14
Figure 7: Maier and Rechtin Intersecting Waterfall Diagram
32
..............................................................15
Figure 8: SPS Concept Definition and Evaluation Process Intersecting Waterfall Model .....................16
Figure 9: GEO satellite anomalies and failures since 1990....................................................................17
Figure 10: Power degradation over lifetime...........................................................................................19
Figure 11: Annual Delta V usage for East-West station keeping as a function of longitude
6
................20
Figure 12: Solar cell efficiency response to light of various wavelengths .............................................24
Figure 13: Solar cell saturation test
42
......................................................................................................25
Figure 14: Laser diffraction pattern
46
.....................................................................................................25
Figure 15: Laser beam spot size versus transmission distance for different aperture sizes....................26
Figure 16: SPSS Fiber Laser Design Architecture .................................................................................29
Figure 17: Characteristic GEO satellite power trend
39
...........................................................................29
Figure 18: Laser spectral lines................................................................................................................30
Figure 19: Laser power beaming field experiment setup and block diagram of the laser transmitter
and receiver sites
43
..................................................................................................................................33
Figure 20: Field experiment received power vs. transmitted power for CO
2
laser
43
..............................33
Figure 21: Energy transmission efficiency observed over a 24-hour period
43
........................................34
Figure 22: Comparison of Si and GaAs cells short-circuit current response to a 25 nS pulse
16
.............36
Figure 23: NREL historical view of solar cell efficiencies
45
..................................................................39
Figure 24: ISS solar array deployed and during assembly
1
....................................................................40
v
Figure 25: ISS beta gimbal assembly
1
....................................................................................................40
Figure 26: Ion engine from Deep Space 1 mission
4
...............................................................................44
vi
Abstract
This thesis discusses the system architecting process for a Solar Power Satellite (SPS) concept.
The heuristic approach allows a spectrum of concepts to be narrowed to final design. An example of the
heuristic process is shown through the systems architecting of the Solar Power Space Satellite (SPSS).
There are many learned lessons and heuristics applied from past studies on the topic.
SPSS design utilizes many commercial off-the-shelf components and commercial practices to
reduce overall mission risk. The system can be launched on traditional geosynchronous capable launch
vehicles, has standard deployments, and requires no on-orbit assembly. SPSS is designed to service
geosynchronous communication satellites by augmenting power levels or extending life.
A cost estimate showed that including the ground, space, and launch segments, plus 20 years
of operations, SPSS cost $1.02b. Reduction in cost will help SPSS successfully take the first step
towards SPS concepts for powering commercial and exploration missions.
1
1.0 Introduction
This discussion will study Solar Power Satellite (SPS) concepts, the system architecting
lessons learned from them, and recommendations for a new architecture. A SPS is a solar collection and
distribution system that beams power to users. These users can be terrestrial, space-based, and on other
planetary and bodies. There have been numerous concepts for SPS systems with various missions,
users, and designs. None of these concepts are currently being funded. This paper will examine where
the system architectures failed and the heuristics that can be derived from them.
The concept of an SPS started in the 1970’s during the energy crisis. Peter Glaser developed
NASA’s reference SPS system and published it 1979. This architecture was called for a dedicated
geosynchronous power station to supply power for large cities. The system was never funded because
of the large infrastructure and therefore cost required before power could be produced.
Over the years architects have revisited Glaser’s concept and developed new missions and
configurations. There have been studies on powering interplanetary missions, lunar bases, lunar rovers,
and space-based users. There have been studies on powering satellites from Earth and using power
beaming to fuel spacecraft propulsions systems. They have all faced the same struggle as Glaser and
have failed for the same reasons. While technologically feasible, the cost of these systems was too high.
These studies have, however, produced invaluable lessons and heuristics to be applied to new SPS
concepts.
2.0 Solar Power Satellite Concepts
This section will discuss SPS concepts suggested in the past, the lessons learned and heuristics
that apply to each. An examination of these relevant studies will show what these concepts lacked and
barriers they ran into. One thing that these studies did not lack is innovative, forward thinking. Most of
these concepts involved massive payloads, structures, and performance requirements, even by today’s
standards. Some were even developed prior to the Space Shuttle being deployed. The introduction of
the shuttle changed the space landscape in the early 1980’s by raising the bar possibilities. Before the
2
shuttle the only heavy lift vehicle in the United States was the Saturn V rocket. The Saturn had
incredible launch capacity, but was only used for lunar missions and went out of production. Prior to
this, SPS architects had to develop heavy launch systems to deploy their concepts. This obviously had
adverse affects on the cost of the systems, but demonstrated innovative architecting. Most of these
architects ran into technological hurdles along the way. And the majority of the obstacles revolved
around the power beaming technology. These architects were forced to predict laser and RF power
beaming technologies 10-20 years down the road. It is interesting to, now 20 years later in some cases,
see how close their predictions are to reality. It is also fascinating to note that solar collection, space
structures, and spacecraft bus were not then, and are not still today, the limiting technologies. Most of
the concepts took advantage of available technology with small growth estimates to create feasible,
achievable systems.
For an architect of an SPS system it is beneficial to use these past concepts to generate a wide
trade space of architecture ideas. The innovative thinking of these architects continues to benefit current
studies. The modern day SPS architect must meld these system ideas with up to date technology and
avoid pitfalls experienced by previous efforts.
2.1 1979 NASA SPS Reference Architecture
Researchers and architects have been investigating solar power satellite concepts for over 25
years. These studies include space-to-ground, ground-to-space, lunar, and interplanetary applications. A
good portion of the past efforts investigated solar powered systems as means to transmit power from
space to the ground for commercial use. The motivation for development of these space-to-ground SPS
systems was the “Energy Crisis” in the 1970’s. NASA, the Department of Energy, and other groups
were desperate to find alternative sources of energy to replace traditional fossil fuels. The government
groups funded numerous studies that looked into the use of space-based systems as a form of clean,
consistent energy. This was attractive due to the downfalls of terrestrial means. Fossils fuels were in
short supply and dirty. Nuclear power had its drawbacks due to toxic and hard to dispose, byproducts.
Even hydroelectric power requires large dams that largely impact to the surrounding environment.
3
In 1968, Peter Glaser patented the idea of a solar power satellite. He subsequently published
the first and most prominent of his studies, the NASA SPS Reference Architecture. This study proposed
the use of massive solar collectors, 5 km by 10 km by 0.5 km in GEO orbit. The RF transmitting array
was massive at 1 km in diameter. This beamed power to massive rectennas, 10 km by 13 km, on the
ground. This led to a massive cost. Each SPS system would provide 5-10 GW of power to a dedicated
spot on the ground, which would feed a city with clean, continuous electrical power. The system would
include a fully reusable launch system, a large on-orbit construction facility, and up to 60 SPS satellite
systems. The cost for this system was 250 billion dollars in FY96 dollars. The obvious problem this
architecture faced was the exorbitant cost of the system. It was new technology at the time and a new
way of “doing business” that needed to be sold to users. Below is a diagram of the space element for
this architecture.
11
Figure 1: NASA's 1979 SPS Reference Architecture by Peter Glaser
11
The challenge faced by Glaser and all SPS systems is to prove that this new technology can
improve the way things have been done since the beginning of the industry. An SPS must prove that it
is less costly, less risky, and better performing than its counter systems. This will not only be a
technological change but a sociological change as well. Customers may still be closed to the idea,
regardless of what is proven, because of sociological aspects. They may still feel that it is a risk, thus
4
not willing to invest the initial cost. Although the technology and infrastructure was in place to realize
Glaser’s system, customers did not buy into the initial cost and risk of the system. Energy had been
produced by hydro-electric plants, burning fossil-fuels, or nuclear plants for many years and any change
was met by opposition which made it difficult to sell. The SPS architect developed an achievable
architecture. However, it failed to overcome the sociological momentum of its counter systems. Any
SPS will face a similar challenge that will have to be addressed. This issue will be discussed further in
the lessons learned and relevant heuristics section.
NASA architect Geoffrey Landis examined “An Evolutionary Path to SPS” in 1990. In his
paper, he proposed first establishing the solar collection and distribution of power terrestrially. He
theorized that due to the success and risk reduction of extensive ground-based systems, space-based
variants would be readily achievable. These conclusions could be correct if the assumption of large-
scale acceptance of ground solar power is correct. However, in 15+ years since the study, growth of that
industry has been slow.
22
The Japanese have worked the problem most in recent years. They have come up with a
concept that can power remote ground sites that currently do not have utilities infrastructure. These
SPSs would beam RF energy to the ground like the Reference Architecture but fly in low-Earth orbit.
This reduces losses by reducing the transmission range, but each SPS can only provide intermittent
service. Thus, this concept requires multiple SPSs and the same ground infrastructure as the Reference
Architecture. Below is a drawing of the concept named SPS 2000. The total cost for the concept was
around $80-$100 billion dollars US.
35
5
Figure 2: Japanese SPS 2000 Concept
35
2.2 Sun Tower and Solar Disk
John Mankins of NASA APO conducted a study that reexamined SPS architectures with new
technology assessments, concepts, and market analysis completed by NASA from 1995-1997. There are
two concepts addressed in this study, Sun Tower and Solar Disk. Mankins shows how the Reference
SPS is not cost effective and that both concepts are cost effective given market growth. However, the
Sun Tower system’s total cost is $50-60 billion and the Solar Disk total cost is around $200 billion.
These concepts are innovative due to their modular design and high performance. Both designs are also
technologically feasible. However, the cost is still a problem for investors. Below is a figure of the Sun
Tower and the Solar Disk.
33
Figure 3: Mankins' Sun Tower and Solar Disk Concepts
33
6
2.3 Interplanetary Transport and Lunar Power Beaming
There have been several studies explaining the benefits of powering interplanetary exploration
with SPS systems. The first type is one that uses ground or space-based lasers to power a crawler that
works like an elevator and climbs up a thin ribbon to a space base in geosynchronous orbit. The other
types are vehicles that convert laser power from an SPS into thrust through electric propulsion. This
technique could be used to provide low mass propulsion to science exploration missions. Below is a
picture of NASA’s Solar Clipper concept that could benefit from laser power illumination.
33
Figure 4: Interplanetary transport, Solar Clipper
33
Geoffrey Landis and others have also suggested solar power beaming as a means of power for
manned bases on the moon and also lunar rovers. The lunar night is approximately 350 hours long
which drives energy storage systems for lunar missions to be large and costly. Power from a SPS could
provide uninterrupted power to a moon base or track a moving rover to extend its useable range. These
concepts have a lot of potential to extend the performance of a lunar mission. Also, these interplanetary
or lunar missions may provide the necessary demand and therefore enabling a push for the technology.
Below are two pictures from a NASA LaRC study of a lunar synchronous SPS similar to the one Landis
proposed.
23,24,5,41
7
Figure 5: Photovoltaic Lunar Synchronous SPS Transmitter and Lunar Receiver Dish
41
A study of these concepts and others allows architects to know what technologies and ideas
have been considered in the past. There are many lessons learned from these studies that will be
discussed in the next section. Mainly a survey of past and similar architectures is imperative for a
system architect. Otherwise there is a danger of going against the adage or heuristic:
“Don’t reinvent the wheel.” [Unknown]
This means that the architect could spend time and effort exploring a technology or system that
has already been considered and eliminated. This adage must be followed to be efficient with time and
money.
3.0 System Architecting Process
3.1 Lessons Learned and Relevant Heuristics
The system architecting of a SPS involves navigating a vast trade space of options. These
design options range from the type of transmitter used to the type of service to provide to users. A good
way of simplifying the problem is to examine the architecture with a heuristic approach. A heuristic can
be a “rule of thumb” or industry accepted technique. They are context and time dependent. However, if
used properly they can greatly reduced the complexity of a system, and allow the architect to focus on
defining the best system. In order to develop heuristics an architect must draw from past studies. This
study derives its heuristic approach from past system architects and studies on SPS concepts. The
studies examined are full of information for an architect designing a SPS system. They have relevant
technologies and much can be learned from their failures and successes. An architect’s job during this
8
step of the design is to glean as much as possible from them. The heuristic below is a good suggestion
to an architect to really learn as much as they can before starting.
“Pause and Reflect.” [Rechtin]
32
This prescriptive heuristic should be used throughout the design process to ensure the architect
is aware of requirements, technology, sociological, and environmental changes.
As the architecture progresses the architect must continue to employ this heuristic as well as
the one below.
“Choose, watch, choose.” [Rechtin]
32
These heuristics are useful in allowing the architect to evaluate the result of past decisions.
The previously discussed concepts are not being funded or developed mainly due to their high
cost. Their failures could be summed up in the heuristic:
“Do not get in a zero-sum game with the outside world.” [Rechtin]
32
These architects took on the large, established electric power industry. Power utility companies
and technologies have been around since Thomas Edison invented them in the late 1800’s. Moreover,
although they had ideas of utilizing the existing infrastructure, they took on the task of changing the
electricity paradigm. This paradigm of producing electric power through the burning of fossil fuels,
nuclear, and hydroelectric sources needs to change. Fossil fuel resources are dwindling and nuclear
power production is dangerous and produces hazardous waste. Hydroelectric facilities offer a clean
solution, but require large environmentally scaring impacts. Solar power production is a viable solution
to these issues. These and other NASA studies all agree that technologically a solar power system is
easily feasible. However, technical feasibility does not convince the public to want to invest 100’s of
billions of dollars to change something that works for now and has for the last 200 years. The heuristic
below is derived from lessons learned through these studies.
“Proving that a concept is technologically feasible and selling it to users are wholly different
things.” [Bidwell]
Proving that a system is feasible is challenging. However, making the sale to users and
overcoming opposition is much tougher. This heuristic is similar and related to Rechtin’s heuristic:
9
“Success is defined by the beholder, not by the architect.” [Rechtin]
32
This heuristic emphasizes the point that even if the architect knows the design works, the users
are the ones who set the success criterion.
Another good heuristic on this point from Rechtin book is:
“If social cooperation is required, the way in which a system is implemented and introduced
must be an integral part of its architecture” [Rechtin]
32
or,
“In introducing technological or social change, how you do it is often more important than
what you do.” [Rechtin]
32
The social and economic environments in this arena are quite challenging and ignoring them is
not a recipe for success. Architects must factor in these considerations as system drivers. Even though
they will not be written in any requirements document, they must be treated equally with other drivers
and constraints. The system must be designed to operate in the environment that it will reside.
There will also be considerable opposition from the people profiting from industries like oil
companies, coal companies, hydroelectric and nuclear. All these power producers have invested
astronomical amounts of money in the pursuit of their product. This leads into the next heuristic:
For every system, there will be at least one counter-system. [Rechtin]
32
In order for the users to buy into a system like an SPS there has to be sufficient need. The
demand for the service has to be cultivated. This heuristic from Rechtin describes it well:
“…to accomplish a top-down architectural change requires recognizing the opportunity
presented by a new technology at just the right time.” [Rechtin]
32
It means that the architectures in the past may have had the correct technology and a feasible
concept however, the timing may not have been right. Some of the previous studies were originally
started at a time when there was a large oil shortage. This was opportune timing because the public and
members of the government were open to change. The problem was that the technology required
incredible investment. As time went on, the technology progressed but the demand faded. Today’s
social and economic environments are starting to head in the direction of cleaner and smarter processes,
10
and the demand may resurface. Hopefully the technology and the demand from the users will be in line
to enable change. Rechtin states this heuristic in chapter 12:
“Risk is defined by the beholder, not the architect.” [Rechtin]
32
This is similar to the one mentioned before. However it states that in order for a concept to be
considered a safe investment the user must be convinced, not just the architect.
Ground-to-space applications for beaming power have added losses associated with
transmission of power through the atmosphere. Laser transmission systems require apertures 10+ meters
in diameter and expensive adaptive optics to correct atmospheric aberrations. These studies have
provided innovative uses for SPS systems. Moreover, in another study by Landis, satellite eclipse power
through ground-based laser illumination is mentioned. Even though the context does not apply, this is
good identification of another potential user group.
Interplanetary and lunar studies give insight into the effects and benefits of pushing the
available technology as far as possible. Architects can use this to extrapolate the state of technology in
the future, or the technology can be paired down to fit within budgetary and mission constraints. A
system architect must make decisions that will greatly affect the outcome of the system. As mentioned
above, the architect must decide whether the system will try to advance technology or be low cost
because these tend to be mutually exclusive. These options are greatly different system definitions.
30,24,5
3.2 Strategic Decisions and Choices
The focus for this paper has been the study of systems architecting of an SPS concept. The
study would be lacking without an examination of the strategic decisions and choices the architect must
address during the systems architecting process. These decisions and choices are a result of strategic
questions that the architect must propose. The reason the architect must pose these questions is open a
dialog with the customers and help define the requirements for the system. This is a key role for the
systems architect.
“The architecture of a system is determined by the decisions made in the first week.”
[Unknown]
11
This heuristic states that decisions made in the beginning of a program have the greatest affect
on the architecture. Therefore it means that when starting the architecting process one must make smart
decisions. In order to make smart decisions, the architect must employ the “pause and reflect” heuristic.
Rechtin states in his book that an architect will face hard lessons when these questions are not answered
early into concept development.
Is there a viable market?
Who benefits?
Who pays?
Who supplies?
Some of the other questions asked by the architect are, “Who are the customers?” and, “What
services should be provided?” These questions will greatly influence the architecture. The architect has
to think about who has need, what type of need is it, and how the system would suffice the need. In
addition, there are some strategic decisions that have been made about this study that greatly influence
the direction and scope.
Who has need for an alternate source of power besides tradition solar collection? User
satellites already have proven methods for producing power and storing energy. This concept will allow
them to either perform power production better, eliminate the need for an energy storage system, or
both. Satellites that could receive power from a continuously viewed constellation of power stations and
would not need to carry batteries for use during eclipse. Satellite builders could then reduce the overall
mass of the satellite. Thermal loading/unloading and large moments of inertia of solar panels drive the
size and complexity of attitude control systems. Eliminating panels could allow for smaller ACS
systems and/or more precision pointing control for user satellites.
What type of service do user satellites require from this type of system? The concept has to
define where they will provide service. What orbital regimes will this system service? This will greatly
drive the technology of the delivery system. How many users could this system support? If this is a
small number, the cost of the system is much higher for each user and probably not cost effective.
12
Making a system that can handle many users will drive the complexity of the technology, which directly
effects the cost.
What technological hurdles are there? What technology will be employed? Technology is the
enabling factor in this concept. The solar collection element will not be the focus. The collection piece
of the architecture is based on established technology. That is a strategic decision made early on in a
SPS study. This will allow the direction to be focused on the technology needed to transmit power from
the collection satellites to the users. The choice of power beaming designs is influential to the system.
The two candidates are RF and optical. This decision will come down to cost, risk, size, weight, power,
performance, and ease of implementation. Can the method provide enough power to user satellites?
Will it provide service to satellite as is, or are modifications to user satellites necessary?
“A good system architect needs to keep the trade space open enough for key decisions to be
made down the road when experience and knowledge are greater.” [Bidwell]
This heuristic agrees with Rechtin’s statement.
“Build in and maintain options as long as possible in the design and implementation of
complex systems. You will need them.” [Rechtin]
32
All the previous questions must be answered by the architect during the process. And the
architect must balance desire to make correct decisions with making progress. The architect can not
know all that is needed to make correct decisions. Decisions sometimes have to be made with imperfect
or partial information. A smart architect builds in the ability to change decisions and adapt as the
requirements, budgets, or environment changes. There are influential decisions made in the beginning
of a project, as mentioned above. However, a good systems architect should be clever enough to be able
to incorporate change and not be hand-cuffed by previous decisions. There is no doubt that this is easier
if good decisions are made in the early stages.
3.3 Defining the System
Another role of the system architect is to define the system, external systems and context in
which the systems operate. This is accomplished through talking with the customer. Once the architect
13
has a grasp of what the customer needs are it becomes easier to define the system to satisfy those needs.
It is also important for the systems architect to define the interfaces between the system, external
systems, and context. This is important because like the heuristic says:
“The greatest leverage in system architecting is at the interfaces.” [Rechtin]
32
For a space-based SPS system the context would be things like space environment, orbital
regime, and the sun. Interactions with the space environment can cause failure if not considered. The
system’s interface with the sun is a large part of the system. This is where the system collects power to
beam to users and is a significant portion of the overall cost. The architect must define this interface
carefully.
External systems would be users and their ground stations. A SPS system must communicate
through this interface to coordinate the action of supplying power to the users. SPSs must be able to
supply power to the users how and when they need it.
The system would be comprised of solar power satellites, ground systems, and the energy
collectors on the user satellites. The SPSs are made up of a solar collector, spacecraft bus, and power
transmitter. They would interact and have interfaces with the sun, each other, energy collectors on
users, and the ground station. Ground systems are comprised of the ground stations and the antennas.
The ground system interacts with the SPS elements commanding them in their mission and addressing
problems. The SPS will normally not be self-commanded because of added cost and complexity.
Therefore, this communication interface is vital. Energy collectors on the user satellites must interface
with the power transmitter and the user spacecraft subsystems. The user communications systems must
tell it where to point. It must rely on the user’s attitude determination and control system to point and it
must interface with the user’s power and thermal systems. All these interfaces are required to work in
order to complete the SPS mission. Rechtin said it correctly in the heuristic:
“The architecture of a support element must fit that of the system which it supports” [Rechtin]
32
The interface between the power transmitter and the energy collector is where the cost and
complexity are found in SPS systems. The rest of the systems are not cheap however, they are based on
14
more proven technology. An architect of a SPS system can affect cost and feasibility of the concept
most at this interface. The figure below is a system definition diagram for a space-based SPS. It shows
the SPS systems, external systems, and context.
Solar Power Satellite #2
Spacecraft Bus
USER
Energy Collector
Ground Station
Ground Antennas Command and
Control
Power
Thermal
Comm
ACS
C&DH
USER
Energy Collector Power
Thermal
Comm
ACS
C&DH
USER
Energy Collector Power
Thermal
Comm
ACS
C&DH
User Ground Station(s)
Ground Antennas Command and
Control
Power
Thermal
Comm
ACS
C&DH
Solar Power Collector
Collection Array
Conversion Unit
Control Unit
Power Transmitter
Laser RF Transmitter
Control Unit
Solar Power Satellite #1
Spacecraft Bus
Power
Thermal
Comm
ACS
C&DH
Solar Power Collector
Collection Array
Conversion Unit
Control Unit
Power Transmitter
Laser RF Transmitter
Control Unit
SUN
GROUND
SPACE
Figure 6: Space-based SPS System Definition Diagram
3.4 Concept Production and Evaluation Process
Another role of a system architect is to produce valid concepts and analyze their feasibility.
This process is illustrated in the figure below. It shows the intersecting waterfall diagram from the
Maier and Rechtin book, The Art of Systems Architecting. Shown in the diagram are a manufacturing
process waterfall and the product development waterfall. They are intersecting to show the correlation
and interactions between them. It is the architect’s job to ensure that both process and product waterfalls
intersect at production. This can be difficult because they have distinctly different schedules and
constraints.
At a first glance, this model is not applicable to developing an SPS because the architect is not
yet producing hardware to be built or processes to define how to manufacture that hardware. Poducts
the architect will be manufacturing are concepts, their performance characteristics and cost. At this
stage, from a hardware perspective, the architect will only focus on top items of the waterfalls, which
are shown in blue.
15
To perform the feasibility analysis the architect needs to evaluate client needs and resources,
build system and payload models for different concepts, and examine the interfaces of concepts. The
client needs and resources are essential to determining feasibility of the concept. A concept must
address and meet customer needs in order to be feasible, but must also be cost effective and fit inside
their resources. The architect will develop a trade space of concepts that comes from evaluating
technologies for their performance, size, weight, power, cost, risk and interoperability/applicability. For
instance, laser power transmission may perform better but require too much power from the solar
collector. The idea is to evaluate concepts at a system level, not just a component or technology
element. This is where the system architecting is involved.
Process Waterfall
Enterprise Need and Resources
Modeling Product Waterfall
Engineering Client Need & Resources
Pilot Plant Conception & Model Building
Build Interface Description
Certify Engineering
PRODUCTION
Certification Maintenance
Operation & Diagnosis Reconfiguration
Evaluation & Adaptation Adaptation
Shutdown
Figure 7: Maier and Rechtin Intersecting Waterfall Diagram
32
As mentioned, the process waterfall is less applicable from the stand-point that the product is
not a tangible piece of hardware to be manufactured. However, while evaluating the concepts it is
important to keep track of the cost, infrastructure and processes to produce that concept. Modeling the
systems engineering and management, or enterprise needs and resources is critical to understanding the
true cost and feasibility of a concept. For instance, a concept that has one vehicle and one user will
require vastly different enterprise needs and resources than a concept with one vehicle and 500
users/payloads or one with 10 vehicles and 50 users each.
Another way to look at the production and evaluation of a concept is shown in this version of
Rechtin’s waterfall diagram below. The diagram is made up of two waterfalls, the product and process.
The product waterfall describes the steps taken in development of the concept. And the process
waterfall shows the means in which to evaluate the concepts.
16
The process to produce concepts is to evaluate client needs, cost constraints and available
technologies. These payload technology concepts will then be modeled, including their interfaces. The
systems engineering step applies to creating a list of concepts to be evaluated. The process for
evaluating the concepts is an integrated cost and performance model approach. This allows the architect
to evaluate large numbers of concepts given that each element can be modeled. With this method
instead of trading locally within a payload or element, architects and users can truly see the impact
throughout the entire system.
In the figure below the intersecting waterfall model is applied it to this type of system. One
interesting point is that the waterfalls do not necessarily intersect at production. The waterfalls now
intersect at the evaluation stage, when concepts are plotted for their performance versus cost. During
this CAIV step, a list of feasible concepts becomes apparent. One could argue that this is where feasible
concepts are produced. Realistically, it is where they are shown to be feasible, but not produced. In
order for a concept to be proven feasible, it has to be modeled and plugged into an integrated system
model. Actual production is before this step. This new intersecting waterfall model can help SPS
architects understand the interactions between concept definition process and evaluation process.
Enterprise needs and resources
Modeling
Engineering
Pilot Trade Mod el
Build Trade Model
Certify Trade Model
Client needs and resources
Payload Concept Modeling
Payload Concept Modeling Interfaces
Systems Engineering
Concept trade space Production
Maintain Trade Model
Reconfigure Trade Model
Adapt Trade Model
End -Use
Evaluate Concepts
Feasibility
Trade Space Redefinition
Trade Model Process Waterfall
Concept Trade Space Waterfall
Figure 8: SPS Concept Definition and Evaluation Process Intersecting Waterfall Model
Forming all the technology and configurations from the past studies into a trade space of
concepts, to be evaluated by an integrated cost and performance model, is beyond the scope of this
study. However, the method discussed in the figure above would be the best process for producing and
evaluating SPS concepts.
17
4.0 Recommended SPS Concept
4.1 SPSS Mission Concept
The system architecting process utilized during this study leverages lessons learned from past
studies and a heuristic approach. This section will discuss an example architecture that has benefited
from this approach. The example used is called the Solar Power Satellite for Space (SPSS). The SPSS
system will leverage these feasible technologies and others to provide power to user satellites. The
SPSS architecture and mission are described as well as applicable lessons learned and heuristics.
The architect can define the mission and market by asking correct strategic questions. The best
market for this system is most likely for geosynchronous communication satellites. These satellites are
optimized for maximum cost per dollar in order to turn a profit on the service they provide. This means
that the satellite designers are pressed to figure out ways to squeeze every ounce of performance from
their systems for a given cost. Communications satellites use large amounts of power (1-20 kW). A
typical communications satellite’s power system is about 20% of the total mass.
26
A large percentage of
that is energy storage system, typically comprised of massive batteries. A reduction or elimination the
need for these massive batteries or a replacement for the entire power system would mean significant
reduction in system mass. Designers could then have the ability to keep the same performance for a
reduction in launch costs, or use the margin gained to increase the performance. Either way, the
profitability of the satellites would grow. The SPSS will also have the ability to provide power to
geosynchronous communication satellites during eclipse and thus prolonging their operational
lifetimes.
27,26
GEO Satellite Anomalies & Failures
96
6
9 81
20
2
1
69
4
Pw r
Mech/ Thermal
TT&C Comm
ACS/ RCS
C&DH
Engine
S/W
P/L
Unknow n
Total: 288
Figure 9: GEO satellite anomalies and failures since 1990
18
Above is a chart showing the breakdown of GEO satellite anomalies and failures since 1990.
The data for this chart was gathered from open-sources and should not be considered to be
comprehensive. The main focus of this diagram is to breakdown the types of anomalies and failures.
Even though this may not contain all the failure events for GEO satellites, the data can be used to
extrapolate that roughly a third of all failures or anomalies are the result of the power system. As shown
in the graph above SPSS could potentially address a third of the problems for GEO communications
satellites. In addition, solar array’s output degrades over time due to micrometeoroid impacts, material
outgassing, thruster plume impingment, and radiation damage. The radiation damage has the most
effect on degradation. Typically, this degradation is roughly 2-4% per year. Due to degradation GEO
communications satellites normally have to start shutting off transponders as the satellite ages. This
means that the satellite services fewer and fewer users over its lifetime. SPSS could provide extra power
to the solar arrays and essentially fill the power gap as time goes along. This would allow the user to
leave all transponders on throughout the lifetime. SPSS will provide users the ability to maintain
beginning of life (BOL) performance. This means that users would not have to replenish their fleet as
often, and it would provide larger revenues for their systems. Below is a chart showing typical lifetime
degradation over the life of a 15-year mission. Also shown is the amount of power that could be
provided by SPSS to maintain BOL performance. For this example an SPSS could provide the user with
a 33% increase in performance. For most communications satellites increase performance is roughly
equal to profits. Therefore, an SPSS system will be quite useful to the GEO communications satellite
community.
This issue is currently plaguing the XM Radio satellites built by Boeing Corporation. The
Boeing 702 series GEO satellites have lost power output from their solar arrays faster than predicted.
This has caused XM and other customers problems. XM recently stated that the problem, “could result
in an earlier than expected replacement of its satellites in order to maintain acceptable power output
levels and service quality”. Apparently the problem is occurring in the 702’s because their solar arrays
utilize a concentrator to focus the sunlight on the cells and these concentrators are “losing their optical
19
quality and becoming foggy”. This information is from www.sat-index.com and is a good example of
where an SPSS system will be used.
44
Satellite Power Degradation Profile
0.00
0.20
0.40
0.60
0.80
1.00
1.20
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Misison Lifetime (years)
Percent O utput
SPSS Input
User Power Output
Figure 10: Power degradation over lifetime
Another use of the SPSS system would be to have it provide power to help prevent power
system failures. Above it was discussed how power systems are responsible for a third of the incidents
in GEO Comm Sats. An SPSS that could provide constant power and/or power through eclipse periods
could help ailing power systems. Providing power during eclipse periods would even allow a satellite
with a non-functioning energy storage system to stay operational. The energy storage system on GEO
satellites are designed to do just that.
Eclipse periods at GEO are not as regular as in LEO. The tilt of Earth’s rotation axis relative to
the Earth’s orbital plane means that satellites at GEO will be, for a large portion of the year, in constant
sunlight. This is typically the case except for two periods when the satellite’s orbital plane passes
behind the Earth. These eclipse periods are short relative to the orbital period and are centered around
the equinoxes. They are longest at the equinoxes and last around 60 minutes. However short, they still
drive the design of the power system. The normal energy storage method is batteries. Batteries vary in
density from 25-200 Whr/kg. Large systems require large battery systems to support the eclipse periods.
Eventually, as the SPSS system proves its usefulness, it could replace energy storage systems on new
GEO satellites. This would allow designers to remove all battery systems and their control and
conditioning units from their designs. SPSS could give these new systems the ability to pack on more
transponders and users, thus more profits.
20
GEO communications satellites are designed to be fuel limited. This means that if nothing else
goes wrong they will eventually lose the ability to maintain position. The SPSS system will ensure that
the power systems are not limiting the lifetimes of its users and allow them to be fuel limited.
4.1.1 Why do GEO satellites require fuel?
In GEO orbit, fuel is used to provide station keeping. Station keeping is necessary because of
orbit perturbations. These perturbations are split into two regimes, east-west and north-south. This split
is because they are caused by different phenomenon. The east-west drift is caused by the asymmetrical
oblateness of the Earth. This J 22 effect causes GEO satellites to drift towards two “gravity wells”, one
over the Himalayas and one over the western US. In order to counteract this drift a GEO satellite must
periodically fire thrusters to maintain longitudinal position. Below is a plot of annual Delta V usage for
these maneuvers versus longitude. The gravity wells are denoted by s1 and s2. There are other
equilibrium points on the plot, u1 and u2, however these are unstable.
Figure 11: Annual Delta V usage for East-West station keeping as a function of longitude
6
The north-south perturbation is caused by third-body (J
3
effects). These are caused by the
Moon and the Sun. The gravitational pull from these other bodies causes a GEO satellite’s inclination to
vary. This variation is periodic from 0 to 15 degrees over a 27 year period. The amount of Delta V
needed to keep a GEO satellite within +/- 0.1 degree control box is about 50 m/s/year. This is a larger
driver than east-west station keeping. GEO satellites can design their systems to work with differing
inclinations, thus being geosynchronous and not geostationary. Geostationary is useful because the
ground users do not have to change the pointing on their receive terminals. One work around for
21
systems with wide uplink beam widths is to gimbal the transmit aperture. This allows the designer to let
the vehicle drift in inclination and save the fuel.
4.1.2 Challenges for SPSS
Distributed power systems as SPSS or the studies listed all have to overcome proven and
widely proliferated technology and infrastructure. The space-to-ground architectures must compete with
traditional power sources that have been in use for centuries. SPSS must overcome standard methods of
individual power systems that have been used since the beginning of the space age. The studies listed
architected, massive systems that cost hundreds of billions of dollars to achieve. The technology to
achieve these systems is and has been in place, but the downfall has been the initial cost. The SPSS
system is designed to use the lessons learned from the past studies. The SPSS will not try to overtake
and electric utility industry in one expensive step. However, if SPSS can be proven cost effective in the
satellite communications industry it could begin the process of changing the paradigm. The SPSS is
designed to be a first step in that long process. Success in the Sat COM market will clear the way for
extensive space-based applications.
As the SPSS, system and related technology prove their mission utility with GEO
communications satellite builders, the SPSS system can be expanded to include powering orbital
transfer vehicles with electric propulsions systems.
27,30,5
These applications could include powering
scientific and exploration missions. This capability could be eventually grown to power exploration
missions on the surface of the moon. There have been many studies done on the benefits of such a
system to these missions.
23,5,41
By the time solar power satellites are used for powering moon bases and
rovers it will be a logical “next step” to begin the methodical transition of terrestrial power generation.
This time however, it will be with proven, utilized, and therefore cheaper space-based technology.
“It is easier to sell two separate $500 million dollar systems than a $1 billion dollar system.
Therefore, use incremental approach to spread out the system cost.” [Bidwell]
SPSS’s answer to the opposition of space-based power generation for terrestrial use is to start
small in a market that can benefit from such a system. This method allows all parties to benefit. The Sat
22
COM market benefits because it can grow to meet its increasing demand for a good profit. Society
benefits because solar power collection and beaming technology is being developed, built, and flown.
Thus, society gains from being secondary investors in the technology. SPSS provides a growth path to
the final architecture of space-based solar as proposed by these previous studies. The SPSS system will
be successful by incrementally growing the architecture, not trying to make drastic and costly changes.
The SPSS missions will be expanded as: the technology matures, is proven cost effective, and provides
mission utility.
33,14,25,22,21
4.2 Power Beaming System
During the discussion of the SPSS the power transmitter was assumed to be a laser system.
This is because of the previously stated mission advantages. SPSS will grow its capability over time.
This growth may include allowing satellite designers to install dedicated energy collectors made to
maximize the benefit from SPSS. These energy collectors could be concentrators for the laser light from
SPSS. Further study into dedicated collectors may prove that an RF transmitter/collector pair is a
superior option. Therefore, the SPSS system will have the ability to change. This leaves the RF
transmitter in the trade space and is in line with the heuristic.
“Build in and maintain options as long as possible in the design and implementation of
complex systems. You will need them.” [Rechtin]
32
In order to build in this flexibility the SPSS must have the interface between the spacecraft and
the power transmitter clean and well defined. As the heuristic states:
“In partitioning, choose elements so that they are as independent as possible, that is, elements
with low external complexity and high internal complexity.” [Alexander, 1964]
32
This means that the architect must design the power transmitter to be essentially “plug-and-
play”. The interfaces have to be well designed and architecture must be fairly robust to handle this
flexibility. As the civil engineering heuristic states:
“Design the structure with good ‘bones’.” [Rechtin]
32
23
There have been numerous studies on RF power beaming including the 1979 Reference
Architecture. These studies have shown RF power beaming to have system efficiencies up to 70-80%.
For instance, as a part of the NASA initiative to study SPS technology, NASA and the Jet Propulsion
Laboratory (JPL) were able to transmit 30 kW over 1 mile with a rectenna at the Goldstone facility in
the Mojave Desert. The Goldstone test showed the feasibility of high power transmission. In 1987,
Canadian researches demonstrated the use of power beaming for powering aircraft while developing the
Stationary High Altitude Relay Platform (SHARP). Japan has also conducted many studies on SPS
concepts and power beam technology. In 1993, they launched a suborbital flight carrying an experiment
called International Space Year-Microwave Energy Transmission in Space (ISY METS). ISY METS
had a mother ship and a daughter ship. The mother transmitted 832 watts from a phased array to the
daughter’s two rectenna paddles, which successfully received power. These experiments have set the
precedent for use of RF power transmission in space power beaming, and the possible use on follow-on
generations of SPSS satellites.
NASA held a conference in 1988 at the Lewis Research Center in Cleveland, OH. The topic of
the conference was Free Space Power Transmission. The conference proceedings and papers are listed
in the Appendix A and contain many interesting concepts for space power beaming and it use. As
mentioned above, the first generation of SPSS will utilize a laser to illuminate user satellite’s solar
arrays. Future SPSS concepts will have to revisit some of the power beaming technologies available.
The technological advances and changes in the SPSS mission make this necessary.
4.2.1 Laser System Requirements and Design Options
The laser system is crucial in the design because it drives the overall size, power, and
performance of the system. The laser must be tuned to the correct wavelength. Wavelength is important
because the user’s solar cells will react with poor conversion efficiency if it is wrong. The power needs
of users drive the output power of the laser. The size of the user’s solar array and range from SPSS to
the user will influence the size of the beam director’s aperture. The laser beam will grow in size as it
propagates through space. And the beam director’s aperture needs to be sized to ensure that the beam’s
24
spot size does not grow larger than the user’s solar panels. These factors will help size the laser, and
thus the rest of the system.
Figure 12: Solar cell efficiency response to light of various wavelengths
In the diagram above solar cell conversion efficiency is plotted versus wavelength. The
majority of GEO communications satellites either have Gallium Arsenide (GaAs) or Silicon solar cells.
Silicon solar cells have been around for a long time and are a cheap and reliable solar cell option. GaAs
cells started coming into the market in the early 1990’s. They inherently have higher conversion
efficiencies than silicon but were not widely used at first due to their high manufacturing costs.
However, as those technologies progressed, these cells became cheaper because of the development of
techniques to grow and dope layer of GaAs on germanium. In addition to their higher efficiency GaAs
cells have higher resistance to radiation damage than silicon cells. Space solar cells experience high
levels of radiation over their lifetimes. Silicon cells can loose up to 10% of their output due to radiation
effects. As the technology for GaAs cells has progressed it has replaced silicon on many GEO
communications satellites. The first generation of SPSS can expect to see a mix of silicon and GaAs
solar arrays on its users. Therefore, based on the diagram above the SPSS laser should have a
wavelength around 850 nm in order to maximize the efficiency of both types of cells. In the future,
other cells types may be more prevalent and therefore future versions of SPSS will have to study
potential users in order to pick a laser wavelength. Another study performed a survey of using solar
cells for power rectification from different sources in 1990. This study also investigated saturation of
these cells. It found that conventional cells handle intensities up to 500 equivalent suns before they
saturate. The figure below is from this study and shows solar cell responses to increasing intensities.
42
25
Figure 13: Solar cell saturation test
42
The table below shows the benefits from 850 nm laser light. An interesting note is that the cells
tested included gaps like those found on standard arrays. Therefore, the efficiencies listed include the
losses from those gaps.
15
Table 1: Experimentally tested solar cell efficiencies with different incident laser wavelengths
15
PV Cell Material 0.81 um 0.83 um 0.85 um
Al 0.08Ga 0.92As 25.5 -- --
GaAs 57.5 58.5 58.5
Si 37.5 38.5 40
Efficiency (%) (Input = 1 W/cm
2
As mentioned above, laser light diffracts as it travels. This diffraction must be taken into
account when designing a power beaming system. In order to be efficient the receiver aperture needs to
be close to the size of the Airy disk. This disk is a spot in which 84% of the laser energy is focused.
Otherwise, energy is being wasted by missing the receive aperture. Below is picture of a laser
diffraction pattern and associated Airy disk.
Figure 14: Laser diffraction pattern
46
26
The radius of the Airy disk can be calculated by the formula below approximated from the
Rayleigh criterion; where λ is the laser wavelength, L is the distance transmitted, and d is the radius of
the transmitting aperture.
d
L
r
22 . 1
The beam director must accurately point the laser beam directly on the target’s solar array to
minimize losses in the energy transfer. Also, the aperture of the beam director must be chosen such that
the beam does not diverge larger than the solar array. Below is a figure showing the relation of spot size
to transmission range. The plot shows this relation for three different aperture sizes. The first generation
SPSS will service users at a maximum range of 10,000 km. This range gives the SPSS a reach of 13.6
degrees of the GEO belt. The figure shows that the aperture needs to be 3 m in diameter in order to keep
the beam spot size from being larger than the small dimension of a typical solar array, 5 m, as
mentioned previously. This aperture is a large optical system on the order of the Hubble Space
Telescope.
13
Laser Beam Spot Radius
0.00
1.00
2.00
3.00
4.00
5.00
6.00
7.00
8.00
9.00
10.00
5 ,0 0 0 . 0
5 ,5 0 0 .0
6 ,0 0 0 .0
6 ,5 0 0 .0
7 , 0 0 0 .0
7 , 5 0 0 . 0
8 , 0 0 0 . 0
8 ,5 0 0 .0
9 ,0 0 0 .0
9 ,5 0 0 .0
1 0 ,0 0 0 .0
1 0 , 5 0 0 . 0
1 1 , 0 0 0 . 0
1 1 ,5 0 0 . 0
1 2 ,0 0 0 .0
1 2 ,5 0 0 .0
1 3 ,0 0 0 .0
1 3 , 5 0 0 .0
1 4 , 0 0 0 .0
1 4 ,5 0 0 . 0
1 5 ,0 0 0 .0
Distance (km)
S pot Ra di us (m)
1 m Aperture
3 m Aperture
5 m Aperture
Laser Beam Spot Radius
0.00
1.00
2.00
3.00
4.00
5.00
6.00
7.00
8.00
9.00
10.00
5 ,0 0 0 . 0
5 ,5 0 0 .0
6 ,0 0 0 .0
6 ,5 0 0 .0
7 , 0 0 0 .0
7 , 5 0 0 . 0
8 , 0 0 0 . 0
8 ,5 0 0 .0
9 ,0 0 0 .0
9 ,5 0 0 .0
1 0 ,0 0 0 .0
1 0 , 5 0 0 . 0
1 1 , 0 0 0 . 0
1 1 ,5 0 0 . 0
1 2 ,0 0 0 .0
1 2 ,5 0 0 .0
1 3 ,0 0 0 .0
1 3 , 5 0 0 .0
1 4 , 0 0 0 .0
1 4 ,5 0 0 . 0
1 5 ,0 0 0 .0
Distance (km)
S pot Ra di us (m)
1 m Aperture
3 m Aperture
5 m Aperture
Figure 15: Laser beam spot size versus transmission distance for different aperture sizes
Other requirements for the laser are that it must be continuous (CW), renewable, have good
beam quality, quickly repositionable, and be power efficient. Further on in the discussion, solar cell
response to laser illumination will be further examined. Solar cells do respond more efficiently to CW
laser light. The laser must be able to provide power to a user over an extended period of time. Most
high power lasers can only produce that high power output for a short amount of time. Beam quality is
important because the better it is the tighter the spot in which the beam can be focused. Also, the beam
27
director system must be fast and accurate in pointing of the beam. SPSS must be able to service
multiple users in order to be cost effective. Therefore, it must be able to have a long operational range
and be quickly cycled between users.
13
There are many types of lasers available for this application. The requirements listed above
help narrow the trade space. Chemical lasers, like CO 2 lasers, are capable of very high power output up
to 10’s of kW. However, they require a large quantity of lasant to flow through the gain module. This
hinders their ability to lase for long durations without massive amounts of lasant. This lasant must be
temperature controlled and recycled for space based operations.
38
Free-electron lasers (FEL) are wavelength tunable and can produce high output powers. These
characteristics make them an interesting option for SPSS. However, FELs produce a pulsed format to
which solar cells do not respond well. Solar cell response to pulsed laser light will be discussed in later
sections. FELs also have not be demonstrated to be tunable to the correct wavelengths needed for this
application. Further analysis and research is needed to determine the utility of FEL technology for
SPSS. That being said, FEL technology holds some promise for future SPSS missions.
A promising choice for the SPSS is solid state lasers. Solid state laser technology has grown
exponentially over the past decade. The power output of solid state lasers is increasing to a point where
they could be used for SPSS. The first solid state lasers (SSL) were constructed on a doped rod
“pumped” or fed light by a flash lamp. Because the lasing material absorbs light efficiently in a few
specific wavelengths this method of pumping is extremely inefficient. The majority of the broad
spectrum being produced by the flash lamp is wasted. The answer to this problem is to pump the gain
medium with diodes that only emit light in high absorption wavelengths. This means that all the light
being produced can be used in the lasing process. The benefit of SSLs is that they need no lasant. The
gain medium is a solid slab or rod. The only thing limiting the duration of use is thermal dissipation.
Therefore in SSLs, as in all lasers, thermal design is critical to the overall system. As the slab or rod is
pumped it becomes hot, and the hotter it gets the less efficient the lasing. Another benefit of solid state
lasers is that they can be modular. Gain modules can be connected in series or in parallel to increase the
power output of the system.
19
28
There is a study by NASA Langley Research Center that utilized a chemical laser to produce a
1 megawatt Solar Power Laser. Lasant was stored in large tanks and had to be resupplied on a regular
basis because the laser system could only recycle a fraction. The system for controlling the flow was a
closed system with a condenser and compressor. The lasant was condensed after passing through the
gain medium and heat was removed. The part that could be recycled was then compressed to restore
flow back to the correct pressure and speed to support lasing. This laser was also a direct solar pumped
system. The concept was to use a large concentrator to focus the sun’s rays into a gain medium to pump
the lasing process. It was thought that this would be more efficient than converting the sun’s energy into
electricity to then drive a laser. However, this method suffers from the same inefficiencies as the first
SSLs. The sun’s ability to pump the gain medium is hindered by the fact that it produces a broad
spectrum of light. Also, the wasted light energy introduced into the system only makes the thermal
dissipation issues worse. But, it is an interesting technology that should be considered for future SPSS
systems.
7,8
4.2.2 Laser System Design and Sizing
The first generation SPSS will utilize a diode pumped solid-state laser to produce a power
beam. An SSL was chosen because of its ability to run for long periods of time and scalability. The
laser will utilize a diode pumped fiber laser with grating to combine the beam. The design will also use
the master oscillator-power amplifier (MOPA) design. In a MOPA, the master oscillator provides a seed
laser beam that feeds the power amplifying fiber gain modules. A fiber laser architecture for this
amount of power would consist on many fiber amplifiers coupled together to create the required output.
This lends itself to harmonic generation because the conversion can be done on lower power levels and
therefore be efficient. This and the ease of heat dissipation from the fibers is why SPSS has a fiber laser
instead of the tradition slab SSL configurations. The fibers will be pumped by a diode array producing
790-810 nm output. This range of wavelengths lies in a good absorption band for neodymium (Nb) host
lasers. The fiber amplifiers will be made of Nb doped with ytterbium, aluminum, and garnet (YAG).
These Nb:YAG fiber amplifiers will each produce 1 kW of 1064 nm infrared light. The wavelength of
29
the laser, the number of fiber amplifiers, and the need for harmonic generation will be explained later in
this discussion. Below is a figure showing the laser architecture for SPSS.
38,12,20
Collimating
Optics Grating
Output
Beam
Pump Diode Array
Fiber Amplifiers
Diode Pumped Fiber Solid State Laser Architecture
Harmonic
Generation Optics
Fiber Array
Master Oscillator
Collimating
Optics Grating
Output
Beam
Pump Diode Array
Fiber Amplifiers
Diode Pumped Fiber Solid State Laser Architecture
Harmonic
Generation Optics
Fiber Array
Master Oscillator
Figure 16: SPSS Fiber Laser Design Architecture
The size of the laser system is driven by the user satellite’s power needs. A typical GEO
communications satellite requires between 1-20 kW. Their solar arrays come in all shapes and sizes,
and can be 50 m long and 5 m wide to produce required power. As shown in the figure below the trend
for GEO communications satellites has been headed towards 10’s of kilowatts. Currently spacecraft like
the popular Boeing 702 is capable of up to 25 kW.
Figure 17: Characteristic GEO satellite power trend
39
The multiple kilowatt 850 nm SSL does not currently exist. The highest power currently at that
wavelength is only a couple watts. Industry experts are predicting that this technology will be there in
the next 5-10 years. There is ongoing research, by groups like Lawrence Livermore National
Laboratory, on Alkali Vapor Lasers (AVL) that produce high power output at the correct wavelength.
Therefore, if SPSS will not be implemented for the next 10 years then it would advantageous to wait on
laser technology growth like these AVLs. If SPSS is to be employed sooner then another solution is
necessary. Below is a figure showing wavelength ranges for several types of lasers.
2, 36,3
30
Figure 18: Laser spectral lines
Currently there are SSLs that can easily produce the power required for this application. The
problem is they have a 1064 nm wavelength. As can be seen in the figure above, this works well for
Silicon cells, but GaAs cells would not be able to convert this wavelength. Harmonic generation is a
nonlinear optical effect that can take an input laser wave and amplifies multiples of the harmonic
frequency. The second harmonic frequency of a wave is half the frequency as the first, or half the
wavelength. Similarly, the third harmonic is a third of the frequency, or a third of the wavelength.
Harmonic generation is accomplished by placing a nonlinear crystal in the laser light. These nonlinear
crystals can take 1064 nm input and produce 532 nm at about 60% efficiency. The 40% of the 1064 nm
light can be passed through. In this case, there would be light at two wavelengths exiting the system. If
the 1064 nm light can not be used, like with GaAs solar cells, it can be separated off the optical path.
The 532 nm, green light, does work for GaAs. From the figure above GaAs can convert this light at
about 30%. The SPSS has two different types of users and therefore two different scenarios. GaAs users
will be serviced with 532 nm laser light produced from a 1064 nm, frequency doubled neodymium
laser. For silicon users, the harmonic generator will be removed from the optical path and straight 1064
nm light will be produced. And as mentioned above having the laser at lower power allows for this
process to be the efficiency mentioned.
19,12, 36,38
There is a chain of inefficiencies that the architect has to consider when sizing the SPSS
system. Starting at the user, the first loss will be its solar array efficiency. Further on in this study the
power rectification of a user’s solar array will be discussed. For sizing purposes 60% conversion
efficiency will be assumed. The next loss is from the laser beam hitting the target. As mentioned, even
31
if the beam control can place the entire Airy disk on the solar array, that disk only contains 84% of the
beam’s energy. That loss is caused by the beam’s diffraction. Only a few years ago, even the best lasers
were only about 10% wall-plug efficient with most being below 1%. Today there are SSLs that boast
35-40% efficiencies and 50-60% efficient lasers are not far down the road. There is a loss in collecting
the sun’s energy and converting it to electricity to drive the laser. There are some new solar cell
technologies that will be developed and could be utilized for SPSS that are 35% solar to electric
efficient. Using these estimates for losses and the power budget shown above the table below shows the
sizing calculations. For this calculation, it is assumed that the user needs follow the trend above and
require 10 kW of power. In addition, this calculation is done for both types of users, GaAs and Si.
12,38
Table 2: Laser power calculation
user power needs 10,000 10,000 W
user SA efficiency 30% 35%
power to user 33333.3 28571.4 W
laser diffraction 56% 84%
laser power 59523.8 34013.6 W
laser efficiency 40% 24%
power to laser 148809.5 141723.4 W
Silicon GaAs
Laser Power Calculation
The Si users would need a 60 kW laser because the spot radius for the given beam director size
is larger than the typical solar array. Therefore about a third of the energy misses the solar array from
10,000 km. This is because the wavelength is twice as large. In order to counteract this, the laser either
has to be more powerful, as in the table, or SPSS would have to operate from half the distance. The
GaAs users require a less powerful laser because all of the spot fits on their solar arrays from the given
range. However, as mentioned before, the harmonic generation to produce 532 nm light is only about
60% efficient and so the laser requires more power to operate. Therefore, designing for the worst case,
the SPSS system needs a 60 kW, 1064 nm laser and roughly 150 kW from the spacecraft to operate.
These are rough calculations used to scale the SPSS systems.
4.3 Power Rectification Analysis and Design
At the other end of the power beaming system is the power rectification system. This will be
made up of the user’s solar arrays for the first generation of SPSS. Therefore, this discussion will look
32
into how solar cells respond to laser light. There have been several field and laboratory experiments to
test this respose.
There are other methods to convert beamed laser power into electricity. For instance, there is a
concept to use incident laser light to pump a magneto hydrodynamic (MHD) generator for power
beaming applications. This study claims high conversion efficiencies and therefore necessitates further
research into applications for future SPSS generations. This and other concepts will not be used because
of the desire for the first SPSS to service satellites as they are, and a new technology would require
unwanted modification. As mentioned above, as SPSS’s utility has proven these concepts will be
relevant to designers looking to build power beaming into their systems.
17
4.3.1 Solar Cell Response to Laser Illumination
There was a field experiment done to prove out the concept of laser beaming and electric
rectification. CO 2 and YAG lasers were used to beam power over a distance of 500 m. On the other end,
GaAs, c-Si, tandem-type a-Si, and CuInSe 2 (CIS) solar cells were used to convert the laser light into
electricity. This experiment measured the efficiency of the energy transfer. The test was a ground test
and was subject to varying weather conditions that factored in to beam pointing and transmission
performance. However, the results are valuable for space-based applications as a system end-to-end
test. Also, the short distance over which the environment acted on the beam reduced its overall affect of
the results.
43
The transmitter used was an off-axis parabolic mirror (diameter 15 cm) Cassegrain telescope
(diameter 20 cm). The receiver was an off-axis parabolic mirror (diameter 15 cm) that directed the laser
light onto the subject solar cells. Below are diagrams of the experiment setup and the laser transmitter
and receiver sites.
33
Figure 19: Laser power beaming field experiment setup and block diagram of the laser
transmitter and receiver sites
43
The receiving laser power as a function of transmitted power from this experiment using the
CO 2 laser is plotted below.
Figure 20: Field experiment received power vs. transmitted power for CO
2
laser
43
The efficiency of the energy transmission was estimated as the slope of the plot. It can be
approximated by combining efficiency estimates in the transmission path. First the radius of the Airy
disk is calculated to ensure the receive aperture is large enough to fit the disk. The wavelengths of
different lasers are shown below in the figure.
This experiment used a CO
2
laser over a distance of 500 m and with a transmitting aperture
radius of 7.5 cm. This yields an Airy disk radius of roughly 9 cm from the formula above. Therefore the
receive aperture is smaller than the diffraction limit spot size and some of the laser energy is missing
the receiver. The amount missing is about 24% by area and 16% by radius. The paper on the experiment
used the radius calculation in its estimate which gave an efficiency estimate close to the results in the
above graph. The reflective efficiency of the mirrors was estimated to be 95%, and atmospheric
transmittance of the laser was estimated to be between 90-95%. This gives system efficiency between
60-63%, which as mentioned fits with the experimental results.
34
The experiment was run for 24 hour period in order to ensure stability of the efficiency results.
Below is a plot of that efficiency over the time period. The results varied from 45-65% showing the
environmental effects. The paper states that there was falling snow at times, temperature varied from -
4
o
C to 10
o
C, and humidity fluctuated between 40% and 90%. A space-based system would not have
these variables and could expect more stable efficiencies near the upper end of the ranges.
Figure 21: Energy transmission efficiency observed over a 24-hour period
43
4.3.2 Solar Cell Response to Pulsed Laser Illumination
Previously it was shown that solar cells react with high electrical efficiencies when under
monochromatic, continuous (CW) laser light. The technology of high power CW lasers is emerging.
Heritage studies have suggested using pulsed lasers for power beaming purposes because of their high
output powers. A popular choice is the free-electron laser (FEL) because of their MW power scaling
possibilities and ability to be frequency tunable. High power FELs under consideration can be split into
two categories, induction and RF. The RF FEL output is a sequence of short pulses ~15 nanoseconds
apart and about 20-40 picoseconds in duration. The induction FEL has longer pulses, 10-50
nanoseconds in duration, and they are spread to about a 20-50 KHz repetition rate.
There have been several studies into the response of solar cells under pulsed laser light. One of
these studies tested a number of cell types under both RF and induction FEL simulated laser light. The
induction pulse format was produced by an 800-Watt average power copper vapor laser. The RF pulse
was simulated by a frequency-doubled, mode-locked Nd:YAG laser. The efficiency response of the
cells was measured. The types of cells measured are shown in the table below.
31
35
Table 3 Cell types test with RF FEL, inductive FEL, and CW laser light
31
When determining the response of a solar cell to pulsed laser light it is important to consider
the minority carrier lifetime of the cell. What happens is if the time constant of the solar cell response is
longer than the gap between pulses then the cell will essentially see CW input. This is important
because of the high efficiency response to CW input. The efficiency of solar cells to pulses spread wide
is low. Weakly absorbed light has slow initial decay, and the strongly absorbed light has a high rate of
decay. Therefore, in order to have the high output of the pulse to be seen as CW the time between
pulses must be short compared to the material’s timescale. In other words, the pulse is broadened over
the timescale. The response of the material drops by a factor of e over the timescale. Silicon cells have a
longer time scale because Si is an indirect bandgap material. Put another way, Silicon cells have weaker
optical absorption and longer minority carrier lifetimes, which leads to deeper absorption of light and
longer time constants. GaAs, GaSb, and CuInSe
2
cells have shorter minority carrier lifetimes because of
their direct bandgap materials. Therefore, these differing types of cells will require different pulse
formats for peak efficiency response. Silicon cells were found to broaden the input pulses by 25
nanoseconds and GaAs cells only about 0.1 nanoseconds. This effect can be seen in the figure below. It
shows a comparison of Si and GaAs short-circuit current response to a 25 nanosecond pulse.
16
36
Figure 22: Comparison of Si and GaAs cells short-circuit current response to a 25 nS pulse
16
The figure above shows how fast the GaAs cell’s response drops off compared to the Si. As
stated, this slower response allows Si to broaden the pulse. The efficiency results of the Lowe, Landis,
Jenkins induction and RF FEL tests are shown in the tables below. This study also published result for
induction FEL format that is wavelength corrected for the cell material. This correction gives even
higher efficiency.
Table 4: Measured cell efficiency response to inductive FEL format
31
Table 5: Cell efficiency response to RF FEL laser light
31
37
This study, as well as others like it, shows that using pulsed format lasers is feasible for power
beaming applications. However, in order to be efficient the pulse length and repetition rate have to be
tuned to the type of solar cells used. The technology of FELs and other pulsed lasers is growing. And as
SPSS architectures need higher and higher powers it will be interesting to see if pulsed lasers prove to
be viable. However, the first generation SPSS will utilize CW laser sources to ensure high efficiencies.
4.4 SPSS Spacecraft Bus Design
This section discusses the cost and concept driving SPSS subsystems. There are some sizing
calculations done in order to approximate the spacecraft bus.
4.4.1 Power Generation
The SPSS will employ solar collection technologies studied in the past. The technology has
been thoroughly researched and established. The different concepts above used different sizes, shapes,
and concentrators. However, the basic technology is similar and therefore readily adapted to the specific
needs of SPSS.
28
The power needed to run the spacecraft bus functions is small compared to the laser transmitter
and therefore is not the real driver for the system. Therefore, the power generation system will not be
designed to optimize for the bus, because although a smaller system may be the best for the bus it is not
the true system driver. A power system designed just for the laser transmitter would have voltages too
high for the bus components. The power generation system will have a power conditioning system that
converts the power to the bus to its required voltage. An important lesson for architects is spelled out in
the heuristic below. This is an obvious example but should be applied when designing any part of the
system.
“Define the drivers across the system; otherwise the system will be optimized locally instead of
for the entire system.” [Bidwell]
The SPSS will have to employ a large solar array in order to provide the power needed for the
spacecraft bus systems as well as the power beaming element. A preliminary power budget used for
38
spacecraft sizing is listed below. As mentioned and as shown in the table below the laser is the driving
element of the system. This laser power is required to produce a powerful laser beam on the user’s solar
array and will be described in detail later.
Table 6: Preliminary SPSS power budget
Power (W)
Laser(s) 150000.0
Laser Pointing 250
Power System 100
Thermal System 50
ADCS 75
Communications 150
Propulsion 2100
Total 152,725
Spacecraft Power Budget
The size of the solar array depends on a number of inputs outside the power budget. The
architect must account for solar irradiance variance, inherent degradation, lifetime degradation, worst-
case sun angle, and solar array efficiency. The solar irradiance or solar energy per unit area varies due
to the time of year. This happens because of differing distances from the Earth to the Sun over the orbit.
If the Earth’s orbit was perfectly circular the irradiance would only vary due to the solar cycle. The
solar activity such as sunspots varies on 11-year cycles. The peak of this cycle produces solar flares and
coronal mass ejections (CMEs). These events cause a high flux of charged particles in earth orbit. The
intensification in solar radiation causes increased solar cell damage. For the purposes of this discussion,
the effects of the solar cycle will be assumed constant at worst case. Also, for spacecraft sizing purposes
the solar constant will be used to estimate the irradiance. This constant varies between 1310 and 1400
W/m
2
. The value of 1358 W/m
2
will be used as an estimate for sizing. The inherent degradation is
efficiency losses in assembly, due to thermal effects, and spacecraft shadowing. The inherent
degradation can vary between 30% and 60% efficiency losses. The same lifetime degradation issues
that plague the user satellites will affect the SPSS. As mentioned above the lifetime degradation varies
from 2-4% per year. The solar arrays will be gimbaled to face the sun as directly as possible. However,
with only one axis of rotation the arrays will not be able to point exactly at the sun due to the tilt of the
Earth’s rotation axis relative to the orbit plane. This could be fixed by using a biaxial gimbal. The
International Space Station (ISS) has large arrays that are articulated to sun point but only have single
axis gimbals. In order to leverage the same technology a single axis gimbal similar to the ones on ISS,
39
and therefore a worst case sun angle of 23
o
is assumed. The solar array efficiency is based on the
material of the solar cells. Below is a graph of solar cell materials and the trends in efficiencies put
together by the National Renewable Energy Laboratory (NREL).
Figure 23: NREL historical view of solar cell efficiencies
45
The SPSS designed will use the highly efficient triple-junction GaAs solar cell on its solar
array panels. This solar cell will give the solar array an efficiency of 35%. Given these input the solar
array will have to have an area of approximately 1,200 m
2
. The calculation of the solar array area is
shown in the table below.
Table 7: Solar array sizing calculation
Spacecraft Total Power 152,725 W
Solar Array Efficiency 35%
Solar Constant 1358 W/m^2
Output Power/Unit Area 475.3 W
Inherent Degradation 68%
Lifetime 20 years
Lifetime Degradation 44%
Worst-Case Sun Angle 23 degrees
Power (BOL) 296.4608 W
Power (EOL) 131.0364 W
Area Solar Array 1165.5 m^2
Mass Solar Array 1298.2 kg
Solar Array Sizing Calculation
The ISS has 8 solar array panels, 400 m
2
each. Each panel produces 23 kW of power and is
comprised of 16,400 Silicon cells. SPSS will have a smaller array than the ISS because it will use GaAs
cells which are 2-3 times more efficient as Si. Below are pictures of an ISS solar array.
1
40
Figure 24: ISS solar array deployed and during assembly
1
SPSS will utilize the heritage solar array technology from ISS. The differences between the
solar arrays on the two systems will be the types of cells. The solar array gimbal and truss assembly
from ISS is pictured below. This system will be used on SPSS because of the high Technology
Readiness Level (TRL). As mentioned, ISS will use eight of these assemblies for a long mission
lifetime. Therefore the technology will be proven by the time SPSS is operational.
Figure 25: ISS beta gimbal assembly
1
Conventional spacecraft run on a 128 Volt bus system. This bus voltage supports all the large
power draw systems on the bus. A power conditioning unit will be needed to regulate this bus voltage
and further downgrade it for the spacecraft systems that run on 28 Volts. The ISS uses a primary bus
voltage between 150-160 Volts DC and a secondary of 125 +/- 1.5 Volts DC. The SPSS design will use
the customary 128 and 28 Volts DC for its design. This will maximize the standardization of the
components. Given these power requirements the solar arrays will be made up of cells in strings. Each
string will consist of fifty two, 2.5 V cells.
41
4.4.2 Energy Storage
There have been many advances in space battery technology over the last ten years. An
example is the shift from NiCad to Li-Ion. These new batteries have been used on various mission
including XSS-11 and the Mars Rover program. Li-Ion batteries have more capacity per mass than
NiCad, and even more important, they do not have the depth-of discharge memory issues inherent in the
NiCad technology. Ni-H 2 batteries are another good option because of their high specific energy and the
same lack of dept-of-discharge memory. The SPSS will employ Li-Ion battery packs to power the
spacecraft bus during eclipse periods. The transmitting payload will not be operated during eclipse
because its operation would require a massive energy storage system.
From prior discussion, GEO satellites see short eclipse periods during the equinox periods.
These periods, although rare, drive the design of the energy storage system. Maintaining full mission
operation during these periods would require batteries that would render the concept too costly.
Flywheel energy storage systems have large a capacity to mass ratio because more energy can be put
into the flywheels by just increasing the mass of the flywheel or the speed at which it turns. However,
these systems, unless designed correctly, can induce large torques to the spacecraft. In addition, they are
a relatively unproven technology for space systems. The International Space Station (ISS) planned to
use them however they were ruled out because of their lack of flight heritage.
27,26,5
The problem with the 1979 Reference SPS and other past systems has been the large initial
cost.
25
The capability to operate through eclipse may be an additional capability available in the next
generation SPSS satellite. This incremental approach will allow the initial SPSS to have a smaller price
tag and give the SPSS program a better probability of success. Lastly, the energy storage system is not
the place to take the large risks in the system. The first SPSS increment will buy down the risk for
future increments in the new technology laden components, like the collection aperture and its control,
the transmitter, and laser system.
“Take risk on true system drivers.” [Bidwell]
This heuristic means that trying to drive down cost by accepting risk on non-cost driving
components is unfruitful. The problem is the risk taken will save the architect only $10 thousand on a
42
$1 billion dollar program. However, assuming risk on a component that costs $50 million may save the
architect $10 million on the same program. A humorous adage in the industry is:
“10 million here, 10 million there…put a bunch of those together and you’re talking real money.”
[Unknown]
The SPSS energy storage system will have to support 2,725 W of bus power, for about an
hour. A typical Li-Ion battery has a specific energy around 150 Wh/kg. This would allow SPSS to have
redundant energy storage systems for around 50-75 kg. In order for SPSS to continue beaming power
through eclipse periods the energy storage system would need to grow to over 2,000 kg.
4.4.3 Thermal Control
The thermal subsystem is responsible for keeping satellite payloads within their require
temperature limits. For SPSS the thermal system will be driven by waste heat produced by the laser.
The laser used is approximately 40% efficient. Therefore, for SPSS’s laser system, producing 60 kW,
the thermal system will radiate 90 kilowatts into space. Although this subsystem is not a cost driver to
the system, it is a crucial function that must support the more costly systems. Again, Rechtin’s heuristic
applies.
“The architecture of a support element must fit that of the system which it supports”
[Rechtin]
32
Each system on the spacecraft will be connected to the radiator through heat pipes. This will
make the spacecraft cold-biased. This means that it is naturally cold and fits a system that will produce
as much heat as the SPSS. There will be excess heat from the laser system that could be used to warm
other bus components. This would involve a complex system to regulate and move heat to cold
components. The first SPSS will just use heaters and thermal blankets to control the temperature of
sensitive components.
The laser system has multiple systems that must be cooled. The laser system design allows the
system to be conductively cooled. This eliminates the need for complex convective systems. The first
component would be the master oscillator. This box can be conductively cooled. This is because it
43
produces only a small amount of heat due to its low laser power. The pump diodes must be cooled
because their output wavelength is temperature dependent. The fiber laser amplifier design makes the
cooling of the system easier than conventional slab architectures. The thin fiber allows the thermally
conductive material to be placed around and close to the hot lasing material. Thus, it promotes quick
and efficient conduction of the heat away from the material. Excess heat in the fiber would cause
thermal lensing and possible damage to the fiber. The optical path also needs to be cooled to ensure
there is no thermal distortion of the optics.
The radiator must dissipate 92 kW of thermal energy into space. The radiator must be 185 m
2
in size and will weigh around 500 kg. The radiator will be deployed on the backside or behind one of
the solar array panels. This position will block it from the sun and allow it accomplish its job
efficiently.
4.4.4 Attitude Determination and Control
This system, like the thermal control subsystem, serves a support function. The attitude
determination and control system (ADCS) is driven by the need to control the large solar array and
accurately point the power transmitter to the users. The solar must be kept pointed at the sun throughout
the orbit. This causes a problem because the large area of the solar array is largely affected by solar
radiation pressure. This drives the ADCS system to be large and powerful. The ADCS also has to
precisely point the power transmitter at the user satellites, otherwise the power is wasted and profits are
lost. Again, the heuristic relates.
“The architecture of a support element must fit that of the system which it supports”
[Rechtin]
32
The ADCS will provide the course pointing and a stable platform for the beam director. In
order to accomplish accurate pointing and stability, SPSS will use control moment gyroscopes (CMGs).
These CMGs are powerful and carry a large amount of momentum. This allows them to hold the
spacecraft steady but also to turn it quickly. The CMGs used on SPSS are made by Honeywell. Their
M50 CMG weighs around 28 kg. SPSS will have 4 of these for multi-axis control and redundancy.
44
SPSS will use three types of sensors for attitude and position knowledge. The first type is two star
trackers from Goodrich that will provide precision attitude knowledge. The second type is two
Goodrich Multi-Mission Earth Sensors. These sensors will provide a second set of attitude knowledge
data to the ADCS. The third type will be a Global Positioning Satellite (GPS) receiver. Normally GPS
receivers are not designed to work at GEO. In order for the receiver to get a signal at GEO is has to see
a GPS satellite on the other side of the earth. Because of this the measurements from the GPS system
will be intermittent. Therefore, SPSS will also rely on ranging from the communications link.
4.4.5 Propulsion System
The SPSS system will require an adequate propulsion system to provide station keeping and to
maneuver it to user locations. The SPSS system should be able to hold it inertial position tightly. This
will allow for users to quickly acquire and point to the SPSS and also help users to stay locked on to the
power beam. Due to the large amounts of power being produced by the power system, electric
propulsion would be a good choice for this system. Electric propulsion requires large amounts of power,
it produces a small amount of constant thrust. The later characteristic is very helpful for SPSS. The
small amounts of constant thrust will allow the station keeping control box to be very small. This means
SPSS will hold its position very accurately. SPSS could use an ion engine similar to the one used on
Deep Space 1. Below is a picture of Deep Space 1’s ion engine being tested. The total mass of the
system was 48 kg. And it requires 2.1 kW power. The power system on SPSS will easily accommodate
this power draw because it is so large.
4
Figure 26: Ion engine from Deep Space 1 mission
4
45
This ion engine uses Xenon gas as the propellant. The way it works is as the propellant enters
the engine it is ionized. Two grids, electrified to 1300 volts, then accelerate the gas out of the engine at
around 35 km/s. This provides a small amount of constant thrust, which is ideal for this mission. The
amount of Xenon propellant used is very small compared to conventional chemical propulsion. The
SPSS ion engine will only use about 50 grams per day. For a 10 year mission SPSS will use under 200
kg of fuel.
4
4.4.6 Structures and Mechanisms
The structure of the SPSS will be based on commercial practices. The structural technologies
are all in place for this system. This mission will require a stable platform and a gimbal to accurately
point the beam director. The structures for SPSS will be similar to that of a commercial
communications satellite, like the Boeing 702 series. These satellites already are designed for higher
power and precision pointed payloads. The pointing of the laser beam will be important to keeping the
beam’s spot focused on the user’s solar array. In addition, the gimbal may have to cycle the spot across
the solar array to ensure optimal performance. Currently there are designs for such systems like
Airborne Laser (ABL). This missile defense system has a large beam director to point its laser beam.
SPSS will utilize a celeostat design similar to ABL. Although the ranges for SPSS are longer than ABL,
it does not have to deal with a bouncing airplane and atmospheric aberration. In order to point the laser
beam on target from 10,000 km the beam director must have a pointing accuracy of 0.001 arc seconds.
This accuracy requirement is an order of magnitude tougher than that of the Hubble Space Telescope.
To achieve this accuracy the beam director will sit on an isolated optical bench to ensure low jitter to
the optics. The spacecraft attitude control system will dampen disturbances from solar arrays and other
deployables. The reflectance of the laser light off the user can be used to help the main beam align with
the target. This could be accomplished by using the harmonic generator to produce a different color
laser light than the one used for power beaming, to illuminate the use’s solar panel. A camera in the
beam director’s optical path could receive that light and produce an image of where the beam is aligned.
This image is either transmitted to the ground to an operator who controls the alignment or to on-board
46
beam control software to do the same. Normally, systems like Hubble rotate and move because of their
stringent pointing requirements. Further study would be needed to determine how quickly SPSS would
need to slew between targets. It would involve a trade between precision pointing and fast slew
capability.
18,9
In either case, there will be a need for cooperation between SPSS and its users. The user
satellite must relay its detailed ephemeris data through SPSS’s control site to aid in acquisition.
Moreover, the user must have knowledge of SPSS’s position in order to point the arrays at the incoming
laser beam. This cooperation will need to continue throughout the power beaming process. The user
will have to relay any attitude or position changes in real-time to the SPSS control system. Even though
the worst case pointing requirements are harder than systems like Hubble, SPSS has the advantage of a
collaborative user on the other end.
4.4.7 Communications & Command and Data Handling
The communication system on SPSS will have to support the command and control of the
system. The command of where the laser is pointed, duration, and intensity must be tightly controlled.
This system is the tie between SPSS and its users. The data handling system will not have to be
complicated. The function of this system will be to telemeter vitals and operational parameters of the
power collection, thermal control, and power beaming systems. These systems, especially the laser and
pointing systems, will have to be monitored carefully to ensure efficiency and accident avoidance. The
communications link architecture is assumed to be a direct downlink to the mission control ground site
or through the Air Force Satellite Control Network (AFSCN). AFSCN provides SPSS will global
coverage at GEO altitude.
4.5 SPSS Mission and Operation Modes
The SPSS will provide power to user satellites through space power beaming. The strategy to
achieve full operational capability is to develop the SPSS systems incrementally. This systematic
47
approach will allow SPSS to leverage new technologies and lessons learned as the constellation
expands. As the constellation expands, the mission capabilities can grow to address more users.
The first SPSS system will provide power to ailing GEO Sat COM satellites by beaming power
to their existing solar arrays with a laser. This will provide power lost due to degradation of the solar
arrays. As mentioned, power from SPSS can be used to power these users through their eclipse periods,
thus relieving the burden on the energy storage batteries. This SPSS will prove the utility of the system
and will likely lead to follow-on SPSS systems that perform the same mission.
27
The success of the first type of SPSS will pave the way for future systems. Spacecraft
designers can start to design systems to harness power from SPSS more efficiently as see the advantage
of a centralize power system. The design can take advantage of SPSS by reducing the size, complexity,
and cost of the power system or replace it completely with a system optimized to harness power from
SPSS.
The second generation of SPSS systems could expand their output to power scientific missions
like deep-space observatories, interplanetary missions, lunar or Martian exploration missions. The
second generation SPSS’s risk will be bought down by the previous SPSS systems. Later generations of
SPSS systems could be grown to power terrestrial needs.
The SPSS system is designed to operate in various modes during its lifetime on orbit. These
modes ensure the safe operation of the satellite. SPSS operational modes are:
Launch and orbit insertion
Deployment and checkout
Mission operations
Safety
Disposal
The SPSS system will be launch into orbit and is responsible with making necessary
corrections to position itself on station. During this phase, the SPSS will begin to deploy its solar
collection aperture. It will also establish communication to the ground and calibrate its instruments. It
will then prove the output and control of the solar collector and power transmitter.
48
The mission of supplying power to users can begin once the systems checkout. SPSS will
continue to perform its mission until its expected lifetime or if there is a fault in the system. The
systems are designed to be doubly fault tolerant. However, if something goes wrong with the SPSS
system it will revert to a safe mode. This inertial mode is designed to keep the spacecraft solar arrays
pointed at the sun and communications antennas at the ground terminals. This orientation ensures power
to the vital spacecraft systems and the communications link to allow ground operators to diagnose and
fix the problem. The power transmission will cease upon entering safe mode. Without the main power
draw the system produces more power than it needs and therefore must waste excess power produced
thermally. This would require large shunt resistors and radiators to dispose of the excess. Because of
this SPSS is designed to turn its solar array to an angle away from normal to the sun during safe mode.
Thus, the solar collector is only producing the amount of power needed by the bus alleviating the need
for such a robust power dissipation system. In addition, this incident angle to the sun means that the
large solar array will experience less solar radiation pressure and is easier to control during safe mode.
The SPSS satellites will burn themselves into SuperSychronous disposal parking orbits at their
end-of-life. Without station-keeping control they will eventually drift to the one of the two ‘gravity-
wells”.
4.6 Cost Estimation
The cost of SPSS is of utmost importance. As has been shown, previous SPS concepts have
failed due to their high cost. A cost estimate for SPSS was derived from the sizing of the different
components and either industry quotes or cost estimating relationships (CERs). The industry quotes
were found through component fact sheets or phone calls to the vendors. The CERs were derived from
the book Space Mission Analysis and Design by Jim Wertz and from previous SPS studies. The table
below shows the cost estimate for SPSS.
40,8
49
Table 8: SPSS Cost Estimate
Component
Size
(m
2
)
Mass
(kg)
Estimated
Cost
(FY06$k)
PM/SEIT
Wrap
Rate
Total Estimated
Cost (FY06$k) Comments
Spacecraft Structure 400 $15,500.00 30% $20,150.00 SMAD CER
Power Subsystem
Solar Array 1200 1300 $15,600.00 30% $20,280.00 Sized for 150 kW
Batteries 50 $3,100.00 25% $3,875.00 Sized for 2.725 kWh
Electronics 75 $4,700.00 20% $5,640.00 SMAD CER
Thermal Control System
Heaters/Blankets/Control Electronics 50 $5,000.00 20% $6,000.00 SMAD CER
Radiator 185 499.5 $10,000.00 20% $12,000.00 SMAD CER
Laser Subsystem
Laser 150 $45,000.00 30% $58,500.00 CER = $750/W
Beam Director & Optics 100 $100,000.00 30% $130,000.00 3 m diameter mirror + Gimbal
ADCS Subsystem 150 $25,000.00 20% $30,000.00 SMAD CER
Propulsion Subsystem
Ion Engine 25 $20,000.00 20% $24,000.00 NSTAR engine + electronics
Propellant 50 $2,000.00 20% $2,400.00 SMAD Estimate
Comm/C&DH/TT&C 100 $10,000.00 30% $13,000.00 SMAD Estimate
Ground System n/a $50,000.00 50% $75,000.00 SMAD Estimate
Operations & Maintenance n/a $400,000.00 10% $440,000.00 20 years @ $20M/yr
Launch n/a $150,000.00 20% $180,000.00 Atlas V
Total: 2950 $1,020,845.00
SPSS Cost Estimation Table
The estimated cost for the SPSS system is $1.02 billion. This number includes the space
segment, launch segment, ground segment, and 20 years of operations. The launch is assumed to be an
Atlas IV EELV, which will provide plenty of lift capability to GEO. Even though the cost of SPSS is
estimated to be high, it is orders of magnitude lower than any previous SPS concept. For comparison,
NASA’s estimate for the cost of the International Space Station’s initial operational capability was
$17.4 billion, with operations adding another $13 billion. The cheapest SPS design was the previously
mentioned Sun Tower by John Mankins. The Sun Tower had a 50-60 billion dollar price tag. Therefore,
SPSS will prove the power beaming concept at a greatly reduced cost.
33
5.0 Conclusions and Further Study
This thesis discusses the system architecting process for a Solar Power Satellite (SPS) concept.
Previous studies are examined and lessons learned are applied. The heuristic approach allows a broad
spectrum of concepts to be narrowed to final design. Strategic choices and decisions help define the
solution for the architect. In addition, the process for defining and analyzing SPS concepts is discussed.
This process is useful for generating and evaluating numerous concepts simultaneously with a trade
model. This model based approach fits better with a rational approach method to systems architecting.
50
The systems architecting of Solar Power Space Satellites (SPSS) uses the heuristic method. This
method works well because there are many learned lessons and heuristics applied from past studies on
the topic.
SPSS design utilizes many commercial off-the-shelf components and commercial practices to
reduce overall mission risk. It reuses solar collection structures and mechanisms from the International
Space Station. SPSS will fly standard Goodrich attitude determination sensors and Honeywell attitude
control actuators. The propulsion system is a reuse of the ion engine from the Deep Space 1 mission.
This will provide SPSS with station keeping thrust while burning little propellant. Another advantage of
the ion drive is that it has small amounts of continuous thrust, which will reduce system disturbances.
This is important because the spacecraft platform must be stable for laser pointing. The system can be
launched on traditional geosynchronous capable launch vehicles, such as Atlas IV. It has standard
deployments and requires no on-orbit assembly.
SPSS was designed to be a spiral development program. The first generation would prove the
concept and pave the way for further fine-tuning of technologies on later generations. Because of this,
the first SPSS is built to service geosynchronous communication satellites as they are. This service will
either boost their output back to beginning of life levels or extend the life of ailing systems. This means
that power-beaming concepts that require modification to the user satellites would be held for later
SPSS designs. This allows the SPSS architect to not have to overcome industry standard methods in a
single expensive step.
Different candidate laser designs are investigated. Chemical lasers are ruled out because of
short on-times and lasant replenishment requirements. Free-electron lasers show promise because of
high output power and tunable wavelength. However, their pulsed output poses an efficiency loss. This
technology has potential for future SPSS systems. The laser chosen was a diode pumped, Nd:YAG
fiber, solid-state laser. This laser was chosen because of its high power scaling and its ability to be
frequency doubled from 1064 nm to 532 nm efficiently. The laser needs to produce green light because
gallium arsenide solar cells do not convert 1064 nm of light to electricity. Ultimately the laser that
would work best is one that produces light at 850 nm. Currently, technology to produce that light in
51
high average power is 5-10 years down the road. This technology should be closely watched as it
progresses because it has the ability to make SPSS and similar systems more efficient.
A cost estimate was constructed from industry quotes, past studies, and cost estimating
relationships. This estimate showed that including the ground, space, and launch segments, plus 20
years of operations, SPSS costs are around 1 billion dollars. Even though this is a lot of money,
compared to previous SPSS concepts it is orders of magnitude less costly. Reduction in cost will help
SPSS successfully take the first step towards SPS concepts for powering space exploration missions,
lunar bases, and terrestrial sites.
It would be interesting to study the next generations of SPSS architectures and how
geosynchronous satellite builders could incorporate them into their designs. The lifetime of SPSS was
chosen for utility reasons and so a detailed investigation into the reliability of the technologies will need
to be done to meet this requirement. In addition, an area of concern are the political ramifications of
putting a kilowatt class laser into space, as it could be misconstrued as a space-based weapon. SPSS
will be designed and operated in a way that ensures no damage could be done to a user or any other
vehicle. That being said, SPSS will have to overcome substantial political hurdles prior to launch. A
survey of the legal limitations and safing requirements for such vehicles are needed.
52
Works Cited
1. Barrett, M. J.; Lyle, R. G.: NASA Space Vehicle Design Criteria (Guidance and Control):
Spacecraft Solar Cell Arrays. NASA SP-8074, May 1971.
2. Beach, R. J.; Krupke, W. F.; Kanz, V. K.; Payne, S. A.; Dubinskii, M. A.; Merkle, L. D.: End-
Pumped Continuous-Wave Alkali Vapor Lasers: Experiment, Model, and Power Scaling.
Journal of the Optical Society of America B, Volume 21, Issue 12, Pages: 2151-2163,
December 2004.
3. Bibeau, C.; Beach, R. J.; Mitchell, S. C.; Emanuel, M. A.; Skidmore, J.; Ebbers, C.A.; Sutton,
S. B.; Jancaitis, K. S.: High-Average-Power 1-m Performance and Frequency Conversion of a
Diode-End-Pumped Yb: YAG Laser. IEEE Journal of Quantum Electronics, Volume 34, Issue
10, Pages: 2010-2019, October 1998.
4. Brophy, J. R.; Kakuda, R. Y.; Polk J. E.; Anderson, J. R.; Marcucci, M. G.; Brinza, D.; Henry,
M. D.; Fujii, K. K.; Mantha, K. R.; Stocky, J. F.; Sovey, J.; Patterson, M.; Rawlin, V.; Hamley,
J; Bond, T.; Christensen, J.; Cardwell, H.; Benson, G.; Gallagher, J.; Matranga, M.; Bushway,
D.: Ion Propulsion System (NSTAR): DS1 Technology Validation Report. NASA & JPL
Technical Report, September 2000.
5. Chang, J. J.; Christiansen, W. H.: Waveguide CO 2 Lasers Pumped by Broad-band Radiation.
IEEE Journal of Quantum Electronics, Volume 29, Issue 5, Pages: 1412 – 1422, May 1993.
6. Chobotov, V. A.: Orbital Mechanics. 3
rd
Edition. American Institute of Aeronautics and
Astronautics, Reston, VA. 2002.
7. De Young, R. J.; Lee, J. H.; Williams, M. D.; Schuster, G.; Conway, E. J.: Comparison of
Electrically Driven Lasers for Space Power Transmission. NASA Technical Memorandum
4045, June 1988.
8. De Young, R. J.; Walker, G. H.; Williams, M. D.; Schuster, G. L.; Conway, E. J.: Preliminary
Design and Cost of a 1-Megawatt Solar-Pumped Iodide Laser Space-to-Space Transmission
Station. NASA TM-4002, September 1987.
9. Feinberg, L. D.; Hagopian, J; Budinoff, J; Dean, B.; Howard, J.: Spherical Primary Optical
Telescope (SPOT): A Cost Effective Space Telescope Architecture. IEEE Aerospace
Conference, 5-12 March 2005.
10. Glaser, P. E.: The Potential of Satellite Solar Power. Proceedings of the IEEE, Volume 65,
Issue 8, Pages: 1162-1176, August 1977.
11. Glaser, P. E.: The Satellite Power Station. G-MTT International Microwave Symposium
Digest, Volume 73, Issue 1, Pages: 1230-1238, June 1973.
12. Hecht, J.: Understanding Lasers: An Entry-Level Guide. 2
nd
Edition. John Wiley & Sons. New
York, NY. 1993.
13. Hodgson, N.; Weber, H.: Laser Resonators and Beam Propagation. 2
nd
Edition. Springer
Science + Business Media. New York, NY 2005.
53
14. Hoffert, M. I.; Potter, S. D.: Beam It Down: How the New Satellites can Power the World.
Extracted from “Solar Power Satellites: A Space Energy System for Earth.” Space Future
Publication, October 1997.
15. Iles, P.A.: Non-Solar Photovoltaic Cells. Paper from IEEE Photovoltaic Specialists
Conference. Volume 1, Pages: 420-425, 21-25 May 1990.
16. Jain, R. K.; Landis, G. A.: Transient Response of Gallium Arsenide and Silicon Solar Cells
Under Laser Pulse. Paper from IEEE Photovoltaic Specialists Conference. Volume 2, Pages:
1874 – 1877, 5-9 Dec. 1994.
17. Jalufka, N. W.: Laser Production and Heating of Plasma for MHD Application. NASA TP-
2798, March 1988.
18. Jefferys, W. H.: Calibration of the Hubble Space Telescope Fine Guidance Sensors: An
Application of Seminal Ideas of H. K. Eichhorn. NASA Contract Report 32906, June 1998.
19. Krupke, W. F.: High Average Power, Diode-Pumped Solid-Sate Lasers. Paper Presented at the
Conference on Lasers and Electro-Optics Europe, Page: 54, 28 August – 2 September 1994.
20. Kwon, J. H.; Williams, M. D.; Lee, J. H.: A Survey of Beam- Combining Technologies for
Laser Space Power Transmission. NASA TM-101529, December 1988.
21. Landis, G. A.: A Supersynchronous Solar Power Satellite. Presented at SPS-97 Space and
Electric Power for Humanity. Montreal, Canada. August 1997.
22. Landis, G. A.: An Evolutionary Path to SPS. Space Power Vol. 9 No. 4 pp. 365-371, 1990.
23. Landis, G. A.: Laser Illumination on Moon Base: Moon Base Night Power by Laser
Illumination. AIAA Journal of Propulsion and Power Vol. 8 No. 1, January 1992.
24. Landis, G. A.: Laser Power Beaming: Satellite Demonstration Applications. NASA CR-
190793, 1992.
25. Landis, G. A.: Reinventing the Solar Power Satellite. NASA TM-2004-212743, February
2004.
26. Landis, G. A.: Satellite Eclipse Power by Laser Illumination. IAF-90-053, 40
th
International
Aeronautics Federation Conf., Dresden, GDR. October 1990.
27. Landis, G. A.: Space Power by Ground-Based Laser Illumination. Presented at 26
th
Intersociety Energy Conversion Engineering Conf., Boston, MA. 1991.
28. Landis, G. A.: Space Solar Array Technology 1997. Presented at SPS-97 Space and Electric
Power for Humanity. Montreal, Canada. August 1997.
29. Landis, G.A.: Photovoltaic Receivers for Laser Beamed Power in Space. Paper from IEEE
Photovoltaic Specialists Conference. Volume 2, Pages: 1494-1502, 7-11 October 1991.
30. Landis, G. A.; Stavnes, M.; Oleson, S.; Bozek, J.: Laser Power Beaming: Space Transfer with
Ground-Based Laser/Electric Propulsion. AIAA-92-3213, 1992.
54
31. Lowe, R. A.; Landis, G. A.; Jenkins, P.: Response of Photovoltaic Cells to Pulsed Laser
Illumination. IEEE Transactions on Electronic Devices, Vol. 42, Issue 4, Pages: 744 – 751,
April 1995.
32. Maier, M.; Rechtin, E.: The Art of Systems Architecting: 2
nd
Edition. CRC Press LLC. Florida
2002.
33. Mankins, J. C.: A Fresh Look at Space Solar Power: New Architectures, Concepts and
Technologies. IAF-97-R.2.03-38
th
, Space Future Publication, 1996.
34. Maryniak, G. E.: International Activities Related to Power from Space. Proceedings of the 31
st
Intersociety Energy Conversion Engineering Conference. Volume 1, Pages: 474-478, August
1996.
35. Nagatomo, M.; Sasaki, S.; Naruo, Y: Conceptual Study of a Solar Power Satellite, SPS 2000.
International Symposium on Space Technology and Science Paper No. 94-e-04. May 1994.
36. Page, R. H.; Beach, R. J. Kanz, V. K.; Krupke, W. F.: First Demonstration of a Diode-Pumped
Gas (Alkali Vapor) Laser. Paper presented at the Conference on Lasers and Electro-Optics,
Volume 1, Pages: 467-469, 22-27 May 2005.
37. Rechtin, E.: Systems Architecting: Creating and Building Complex Systems. Prentice Hall
PTR. New Jersey 1991.
38. Seigman, A. E.: Lasers. University Science Books. Sausalito, CA. 1986.
39. Walls, B.: Utility Aspects of Space Power: Load Management Versus Source Management.
NASA Technical Memorandum 108496, July 1995.
40. Wertz, J. R.; Larson, W. J.: Space Mission Analysis and Design. 3
rd
Edition. Microcosm Press.
El Segundo, CA. 1999.
41. Williams, M. D.; De Young, R. J.; Schuster, G. L.; Choi, S. H.; Dagle, J. E.; Coomes, E. P.;
Antoniak, Z. I.; Bamberger, J. A.; Bates, J. M.; Chiu, M. A.; Dodge, R. E.; Wise, J. A.: Power
Transmission by Laser Beam From Lunar-Synchronous Satellite. NASA TM-4496, November
1993.
42. Yater, J. A.; Lowe, R. A.; Jenkins, P. P.; Landis, G. A.: Pulsed Laser Illumination of
Photovoltaic Cells. Paper from IEEE Photovoltaic Specialists Conference. Volume 2, Pages:
2177 – 2180, 5-9 Dec. 1994.
43. Yugami, H.; Kanamori, Y.; Arashi, H.; Niino, M.; Moro, A.; Eguchi, K.; Okada, Y.; Endo, A.:
Field Experiment of Laser Energy Transmission and Laser to Electric Conversion. Paper from
Energy Conversion Engineering Conference and Exhibit. Volume 1, Page(s):625 – 630, 27
July-1 Aug. 1997.
44. http://www.sat-index.com/failures/index.html?http://www.sat-
index.com/failures/702arrays.html
45. www.nrel.gov
46. http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/cirapp2.html &
http://www.cambridgeincolour.com/tutorials/diffraction-photography.html
55
Appendix A
Appendix A is a listing of papers that are not quoted in the text but were apart of the
background research into SPS system and the related technology.
1. Bourgasov, M. P.; Kvasnikov, L. A.; Smakhtin, A. P.; Tchuyan, R. K.; Tolyarenko, N. V.:
Conception of Spacecraft Centralized Power Supply. IEEE Aerospace and Electronic Systems
Magazine, Volume 12, Issue 10, Pages: 3-7, October 1997.
2. Feingold, H.: Space Solar Power (SSP) Concept and Technology Maturation (SCTM) Program
– Systems Integration, Analysis and Modeling Status and Plans. SCTM Technical Interchange
Meeting #1 Presentation. Ohio Aerospace Institute. September 2002.
3. Free-Space Power Transmission – NASA Conference Publication 10016
4. Hull, J. R.; Myers, I. T.: High-Temperature Superconductors for Space Power Transmission
Lines. Paper Submitted to ASME Winter Annual Meeting Conf., San Francisco, Pages: 1-20,
August 1989
5. Landis, G. A.: Applications for Space Power by Laser Transmission. OE Reports December
1994 Issue.
6. Landis, G. A.; Bailey, S. G.: Photovoltaic Engineering Testbed on the International Space
Station. Paper Presented at The 2
nd
World Conference on Photovoltaic Solar Energy
Conversion, July 1998.
7. Lee, J. H.; Tabibi, B. M.: Space-Borne Solar Laser for Power-Beaming Applications. AIP
Conference Proceedings, Vol. 664 - Issue 1, May 2003.
8. McMahon, W. E.; Emery, K. E.; Friedman, D. J.; Ottoson, L.; Young, M. S.; Ward, J. S.;
Kramer, C. M.; Duda, A.; Kurtz, S.: Outdoor Testing of GaInP2/GaAs Tandem Cells with Top
Cell Thickness Varied. Paper from International Conference on Solar Concentrators for the
Generation of Electricity or Hydrogen, May 2005.
9. Ortiz, G. G.; Sandusky, J. V.; Biswas, A.: Design of the Opto-Electric Receiver for Deep
Space Optical Communications. SPIE Proceedings, Vol 3932, Paper 13. January 2000.
10. Smestad, G.; Ries, H.; Winston, R.; Yablonovitch, E.: The Thermodynamic Limits of Light
Concentrators. Solar Energy Materials, Volume 21, Pages: 99-111, 1990.
Abstract (if available)
Abstract
This thesis discusses the system architecting process for a Solar Power Satellite (SPS) concept.The heuristic approach allows a spectrum of concepts to be narrowed to final design. An example of the heuristic process is shown through the systems architecting of the Solar Power Space Satellite (SPSS). There are many learned lessons and heuristics applied from past studies on the topic.
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Creator
Bidwell, Joseph Grady
(author)
Core Title
The system architecting process for a solar power satellite concept
School
Viterbi School of Engineering
Degree
Master of Science
Degree Program
Aerospace Engineering (Astronautics)
Publication Date
11/17/2006
Defense Date
10/25/2006
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Language
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Erwin, Daniel A. (
committee chair
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