Space-based solar power

History

In 1941, science fiction writer Isaac Asimov published the science fiction short story ” Reason, ” in which a space station transmits energy collected from the Sun to various planets using microwave beams. The SBSP concept, originally known as the solar-power system (SSPS), was first described in November 1968. ^[6] In 1973 Peter Glaser was granted US patent number 3,781,647 for his method of transmitting power over long distances (eg from an SPS to Earth ‘s surface) using microwaves from a very large antenna (on to a square kilometer) on the satellite to a much larger one, well known to a rectenna , on the ground. ^[7]

Glaser then was a vice president at Arthur D. Little , Inc. NASA signed a contract with ADL in the United States. (continued) more information and research. ^[8]

Between 1978 and 1986, the Congress authorized the Department of Energy (DoE) and NASA to jointly investigate the concept. They organized the Satellite Power System Concept Development and Evaluation Program. ^[9] [10] The study has been extensively performed to date (budget $ 50 million). ^[11] Several reports have been published investigating the engineering feasibility of such an engineering project. They include:

• Resource Requirements (Critical Materials, Energy, and Land) ^[12]
• Financial / Management Scenarios ^[13] [14]
• Public Acceptance ^[15]
• State and Local Regulations as Applied to Satellite Power System Microwave Receiving Antenna Facilities ^[16]
• Student Participation ^[17]
• Potential of Laser for SBSP Power Transmission ^[18]
• International Agreements ^[19] [20]
• Centralization / Decentralization ^[21]
• Mapping of Exclusion Areas For Rectenna Sites ^[22]
• Economic and Demographic Issues Related to Deployment ^[23]
• Some Questions and Answers ^[24]
• Meteorological Effects on Laser Propagation and Direct Beam Solar Pumped Lasers ^[25]
• Public Outreach Experiment ^[26]
• Power Transmission and Reception Technical Summary and Assessment ^[27]
• Space Transportation ^[28]

Discontinuation

The project was not continued by the 1980 US Federal elections. The Office of Technology Assessment concluded that “Too little is currently known to the technical, economic, and environmental aspects of SPS to make a decision to proceed with its development and deployment. engineering verification program would be a high-risk venture. ” ^[29]

In 1997 NASA conducted its “Fresh Look” study to review the modern state of SBSP feasibility. In assessing “What Has Changed” since the DOE study, NASA Asserted que la “US National Space Policy now calls for NASA to make significant investments in technology (not a Particular vehicle) to drive the costs of ETO [Earth to Orbit] transportation down This is an absolute requirement of solar power. ^[30]

Conversely, Dr. Pete Worden’s claim that space-based solar is more expensive than solar power from the Arizona desert, with a major cost being the transportation of materials to orbit. Dr. Worden referred to possible solutions as speculative, and that would not be available for decades at the earliest. ^[31]

On Nov. 2, 2012, China proposed space collaboration with India that said SBSP, “May be Space-based Solar Power Initiative so that both India and China can work for long-term to bring space solar power to earth. ” ^[32]

Space Solar Power Exploratory Research and Technology program

In 1999, NASA’s Space Solar Power Exploration Research and Technology Program (SERT) was initiated for the following purposes:

• Perform design studies of selected flight demonstration concepts.
• Evaluate studies of general feasibility, design, and requirements.
• Create conceptual designs of subsystems that make use of advanced SSP technologies to benefit future space or terrestrial applications.
• Formulate a preliminary plan of action for the US (working with international partners) to undertake an aggressive technology initiative.
• Construct Technology Development and Demonstration Roadmaps for Critical Space Solar Power (SSP) elements.

The concept of a solar power satellite (SPS) concept for a future gigawatt space power system, to provide electrical power by converting the Sun ‘s energy and beaming to Earth’ s surface, and provides a conceptual development that would utilize current technologies. Proposed SERT year inflatable photovoltaic gossamer structure with gold lenses concentrator solar heat engines to convert sunlight into electricity. The program is viewed both at systems and synchronous orbit and geosynchronous orbit . Some of SERT’s conclusions:

• The increasing global energy demand is likely to continue because of all sizes being built.
• The environmental impact of those plants and their impact on world energy supplies and geopolitical relationships can be problematic.
• Renewable energy is a compelling approach, both philosophically and in engineering terms.
• Many renewable energy sources are limited in their ability to provide the required level of supply for the world.
• Based on their Concept Definition Study, space solar power concepts may be ready to reenter the discussion.
• Solar power satellites should not be envisioned as requiring unimaginably large initial investments in fixed infrastructure before the location of productive power plants can begin.
• Space solar power systems appear to have many significant environmental advantages when compared to alternative approaches.
• The economic viability of space solar power systems depends on many new technologies, but the same can not be said of many other advanced power technologies options.
• Space solar power may well emerge as a serious candidate among the options for meeting the energy demands of the 21st century. Space Solar Power Satellite Technology Development at the Glenn Research Center-An Overview. James E. Dudenhoefer and Patrick J. George, NASA Glenn Research Center , Cleveland, Ohio.
• Launch costs in the range of $ 100- $ 200 per kilogram of low-cost earth orbit are needed if SPS are to be economically viable. ^[11]

Japan Aerospace Exploration Agency

The May 2014 IEEE Spectrum magazine carried a lengthy article “It’s Always Sunny in Space” by Dr. Susumu Sasaki. ^[33] The article stated, “It has been the subject of many prior studies and the stuff of sci-fi for decades, but space-based solar power could not at the Tokyo- based Japan Aerospace Exploration Agency (JAXA). ”

JAXA announced on 12 March 2015 that they wirelessly beamed 1.8 kilowatts 50 meters to a small receiver by converting electricity to microwaves and then back to electricity. This is the standard plan for this type of power. ^[34] [35]On 12 March 2015 Mitsubishi Heavy Industries demonstrated transmission of 10 kilowatts (kW) of power to a receiver unit located at a distance of 500 meters (m) away. ^[36]

Challenges

Potential

The SBSP concept is attractive because it has several major advantages over the Earth’s surface.

• It is always sunny noon in space and full sun.
• Collecting surfaces could receive much more intense sunlight, owing to the lack of obstructions such as atmospheric gasses , clouds , dust and other weather events. Therefore, the intensity in orbit is approximately 144% of the maximum possible intensity on Earth’s surface. ^{[ quote needed ]}
• A satellite could be illuminated over 99% of the time, and be in Earth’s shadow at a maximum of only 72 minutes per night at the spring and fall equinoxes at local midnight. ^[37] Orbiting satellites can be exposed to a consistently high degree of solar radiation , generally for an average of 29% per day. ^[38]
• Power could be relatively quickly redirected directly to areas that need it most. A collecting satellite could possibly direct power on demand to different surface locations based on geographical baseload or peak load power needs. Typical contracts would be for baseload, continuous power, since peaking power is ephemeral. ^{[ quote needed ]}
• Elimination of plant and wildlife interference.
• With very large scale implementations, especially at lower altitudes, it is possible to reduce incoming solar radiation reaching earth’s surface. This would be desirable for counteracting the effects of global warming .

Drawbacks

The SBSP concept also has a number of problems:

• The large cost of launching a satellite into space
• Inaccessibility: Maintenance of an earth-based solar panel is relatively simple, but construction and maintenance would typically be done telerobotically. In addition to cost, astronauts working in GEO (geosynchronous Earth orbit) are exposed to a very high radiation hazard and risk and cost to the same task as telerobotically.
• The space environment is hostile; They would be on earth (except at orbits that are protected by the magnetosphere). ^[39]
• Space debris is a major hazard, and all large structures such as these have been identified as potential sources of orbital debris. ^[40]
• The broadcast frequency of the microwave downlink (if used) would need to isolate the SBSP systems away from other satellites. GEO space is already used and it is expected that ITU would allow an SPS to be launched. ^[41]
• The large size and corresponding cost of the receiving station on the ground. ^{[ quote needed ]}
• Energy losses during several phases of “photon to electron to photon back to electron,” Elon Musk has stated. ^[42]

Design

Space-based solar power consists of three elements: ^[2]

1. collecting solar energy in space with inflatable reflectors or mirrors onto solar cells
2. wireless power transmission to Earth via microwave or laser
3. receiving power on Earth via a rectenna , a microwave antenna

The space-based portion does not require support against gravity (other than relatively weak tidal stresses). It needs no protection from terrestrial wind or weather, will aim-have to cope with space hazards Such As micrometeors and solar flares . Two basic methods of conversion have been studied: photovoltaic (PV) and solar dynamic (SD). Most analyzes of SBSP have focused on photovoltaic conversion using solar cells. Solar dynamic uses mirrors to concentrate light on a boiler. The use of solar dynamic could reduce mass per watt. Wireless power transmission was proposed early on the Earth’s surface, using microwave or laser radiation at a variety of frequencies.

Microwave power transmission

William C. Brown demonstrated in 1964, during Walter Cronkite ‘s CBS News program, a microwave – powered model helicopter that received all the power it needed for a flight from a microwave beam. Between 1969 and 1975, Bill Brown was the technical director of a JPL Raytheon program that beamed 30 kW of power over a distance of 1 mile (1.6 km) at 84% efficiency. ^[43]

Microwave power transmission of kilowatts has been obtained by existing tests at Goldstone in California (1975) ^{[43] [44] [45]} and Grand Basin on Reunion Island (1997). ^[46]

More recently, microwave power transmission has been demonstrated in Hawaii (92 miles away) by John C. Mankins. ^[47] [48] Technological challenges in terms of the array layout, the single radiation element design, and the overall efficiency, are presently a subject of research, as shown by the Special Session on “Analysis of Electromagnetic Wireless Systems for Solar Power Transmission “to be held in the 2010 IEEE Symposium on Antennas and Propagation. ^[49]In 2013, a useful overview was published, covering technologies and issues associated with microwave power transmission from space to ground. It includes an introduction to SPS, current research and future prospects. ^[50] Moreover, a review of current methodologies and technologies for the design of antenna arrays for microwave power transmission appeared in the Proceedings of the IEEE ^[51]

Laser power beaming

Laser power beaming was envisioned by some at NASA as a stepping stone to further industrialization of space. In the 1980s, researchers at NASA worked on the use of lasers for space-to-space power beaming, focusing primarily on the development of a solar-powered laser. In 1989 it was suggested that power could also be used by laser from Earth to space. In 1991 the SELENE project (SpacE Laser ENErgy) had begun, which included the study of laser power beaming for supplying power to a lunar base. The SELENE program was a two-year research effort, but the cost of taking the concept to operational status was too high, and the official project ended in 1993 before reaching a space-based demonstration. ^[52]

In 1988 the use of an Earth-based laser to power an electric thruster for space propulsion was proposed by Grant Logan, with technical details worked out in 1989. He proposed using diamond solar cells operating at 600 degrees to convert ultraviolet laser light.

Orbital location

The advantage of locating a space power station in geostationary orbit is that the antenna geometry constant constant, and so keeping the antennas lined up is simpler. Another advantage is that continued continuous power transmission is placed in orbit; other space-based power stations have much longer start-ups A collection of Low Earth Orbit (LEO ) space power stations has been proposed to GEO ( Geostationary Orbit ) space-based solar power. ^[53]

Earth-based receiver

The Earth-based rectenna would likely consist of many short dipole antennas connected via diodes . Microwave broadcasts from the satellite would be received with 85% efficiency. ^[54] With an antenna as an antenna, the reception efficiency is better, but its cost and complexity are also much greater. Rectennas would be likely to be several kilometers across.

In space applications

A laser SBSP could also power the moon or Mars on the surface of the moon. A spacecraft or another satellite could also be powered by the same means. NASA on Space Solar Power, Solar Power Propulsion Systems could potentially be used for interplanetary human exploration missions. ^{[55] [56] [57]}

Launch costs

One problem for the SBSP concept is the cost of space launches and the amount of material that would need to be launched.

Much of the material has not been delivered to its eventuality orbit immediately, which allows for high efficiency (but slower) engines could move SPS material from LEO to GEO at an acceptable cost. Examples include ion thrusters or nuclear propulsion . Power beaming from geostationary orbit by microwaves carries the difficulty that the required ‘optical aperture’ sizes are very large. For example, the 1978 NASA SPS study required a 1-km diameter transmitting antenna, and a 10 km diameter receiving rectenna, for a microwave beam at 2.45 GHz . These sizes may be decreased by using shorter wavelengths, although they have increased atmospheric absorptionand even potential beam blockage by rain or water droplets. Because of the thinned array curse , it is not possible to make a narrower beam by combining the beams of several smaller satellites. The large size of the transmitting and receiving antennas means that SPS will necessarily be high; small SPS systems will be possible, but uneconomic. ^{[ original research? ]}

To give an idea of ​​the scale of the problem, assuming a solar panel mass of 20 kilograms per kilowatt (without considering the mass of the supporting structure, or any significant mass reduction of any focusing mirrors) at 4 GW power station would weigh about 80,000 metric tons , ^[58] all of which, in present circumstances, be launched from the Earth. Very light designs could achieve 1 kg / kW, ^[59] meaning 4,000 metric tons for the solar panels for the same 4 GW capacity station. This would be the equivalent of between 40 and 150 heavy-lift launch vehicle(HLLV) launches to the earth orbit, where it would likely be converted into subassembly solar arrays, which then could use high-efficiency rocket-to-engine (to) reach GEO ( Geostationary orbit ). With HLLVs of $ 500 million to $ 800 million, and HLLVs at $ 78 million, the total cost would be between $ 11 billion (low cost HLLV, low weight panels) and $ 320 billion ( expensive ‘HLLV, heavier panels). ^{[ citation needed ] [ original research? ]}To these costs must be added to the environmental impact of heavy space launch emissions, if such costs are to be used in comparison to earth-based energy production. For comparison, the cost of a new coal ^[60] or nuclear power plant ranges from $ 3 billion to $ 6 billion per GW (not including the full cost to the environment of CO2 emissions or nuclear fuel, respectively); Another example is the Apollo Missions to the Moon cost a grand total of $ 24 billion (1970s’ dollars), which would cost $ 140 billion today, more expensive than the construction of the International Space Station . ^{[ original research? ]}

Building from space

From lunar materials launched in orbit

Gerard O’Neill , noting the problem of high-flying in the early 1970s, proposed building the SPS’s in orbit with materials from the Moon . ^[61] Launch costs from the Moon are much less than from Earth, due to the lower gravity and lack of atmospheric drag . This 1970s NASA’s Space Shuttle. This approach would require substantial upfront investment capital to establish mass drivers on the Moon. ^[62]Nevertheless, on 30 April 1979, the Final Report (“Lunar Resources Utilization for Space Construction”) by General Dynamics’ Convair Division, under NASA contract NAS9-15560, concluded that it would be cheaper than Earth-based materials for a Solar Power Satellites of 10GW capacity each. ^[63]

In 1980, when it became obvious, O’Neill et al. published another road to manufacturing using lunar materials. ^[64] This 1980s SPS concept we relied less human presence in space and more on Partially self-replicating systems on the lunar surface area under remote control of workers stationed on Earth. The high net energy gain of this proposal derives from the Moon’s much shallower gravitational well .

SPS being built. SPS being built. The low cost of lunar materials in O’Neill’s vision would be supported by solar power satellites. Advanced techniques for launching from the Moon can reduce the cost of a solar power satellite from lunar materials. Some proposed techniques include the lunar mass driver and the lunar space elevator , first by Jerome Pearson. ^[65] It would require establishing silicon mining and solar cell manufacturing facilities on the Moon . ^{[ citation needed]}

On the Moon

David Criswell suggests the Moon is the optimum location for solar power stations, and promotes lunar solar power . ^[66] [67] The main advantage he Envisions is building Largely from locally available lunar materials, using in-situ resource utilization , with a teleoperated mobile factory and crane to assemble the microwave reflectors, and rovers to assemble and paved solar cells, ^{[ 68]} which would significantly reduce costs compared to SBSP designs. Power relay satellites orbiting around the earth and the Moon are also part of the project. A new project of 1 GW starts at $ 50 billion. ^[69] The Shimizu Corporationcombination of lasers and microwave for the lunar ring concept, along with power relay satellites. ^[70] [71]

From an asteroid

Asteroid mining has also been considered seriously. A NASA design study ^[72] evaluated at 10,000 ton mining vehicle (to be assembled in orbit) that would return a 500,000 ton asteroid fragment to geostationary orbit. Only about 3,000 tones of the mining ship would be traditional aerospace-grade payload. The rest would be a reaction to the mass-driver engine, which could be arranged to rocket stages used to launch the payload. Assuming that 100% of the returned asteroid was useful, and that the asteroid could be reduced to 95% reduction in launch costs. However, the true merits of such a method would depend on a thorough mineral survey of the candidate asteroids; thus far, we have only estimates of their composition. ^[73]One proposal is to capture the asteroid Apophis into earth orbit and convert it into 150 solar power satellites of 5 GW Each gold the larger asteroid 1999 AN10 qui is 50x the size of Apophis and wide enough to build 7,500 5-Gigawatt Solar Power Satellites ^{[74 ]}

Gallery

• A Lunar base with a mass driver. NASA conceptual illustration

• An artist’s design of a “self-growing” robotic lunar factory.

• Microwave reflectors on the moon and robotic teleoperated paving rover and crane.

• “Crawler” sleepers Lunar surface, smoothing, melting a top layer of regolith, then depositing elements of silicon PV cells directly on surface

• Sketch of the Lunar Crawler to be used for the production of lunar solar cells on the surface of the moon.

• Shown here is an array of solar collectors that converts into microwave beams.

• A solar power satellite built from a mined asteroid.

Counter arguments

Safety

The use of microwave transmission of power has been the most controversial issue in any SPS design. At the Earth’s surface, it has suggested a maximum beam intensity of 23 mW / cm ² (less than 1/4 the solar irradiation constant ), and an intensity of less than 1 mW / cm ² outside the rectenna fenceline (the receiver’s perimeter). ^[75] These comparisons with current United States Occupational Safety and Health Act (OSHA) workplace exposure limits for microwaves, which are 10 mW / cm ² , ^{[76] [ original research? ]}– the limit itself being expressed in voluntary terms and ruled unenforceable for Federal OSHA enforcement purposes. ^{[ citation needed ]} A beam of this intensity is therefore at its center, of a similar magnitude to current safe workplace levels, even for long term or indefinite exposure. ^{[ original research? ]} Outside the receiver, it is far less than the OSHA long-term levels ^[77] Over 95% of the energy beam will fall on the rectenna. The remaining microwave energy will be absorbed and dispersed well within the standards of the world. ^[78]It is important for system efficiency as much of the radiation as possible be focused on the rectenna. Outside the rectenna, microwave intensities should be completely unaffected. ^[79]

Exposure to the beam is able to be minimized in other ways. On the ground, physical access is controllable (eg, via fencing), and typical aircraft flying with a protective metal shell (ie, a Faraday Cage ), which will intercept the microwaves. Other aircraft ( balloon , ultralight , etc.) can not be controlled by the airspace. The microwave beam intensity at the center of the beam would be designed and built into the system; simply, the transmitter would be too far away and too small to be able to increase the intensity of unsafe levels, even in principle.

In addition, a design constraint is that the microwave beam must not be so intense as to insult wildlife, particularly birds. Experiments with deliberate microwave irradiation at reasonable levels have failed to show negative effects even over multiple generations. ^[80] Suggestions have been made to locate rectennas offshore, ^[81] [82] but this presents serious problems, including corrosion, mechanical stresses, and biological contamination.

A recursive phased array antenna / rectenna. A “pilot” microwave beam emitted from the center of the rectenna on the ground establishes a phase front at the transmitting antenna. There, circuits in each of the antenna’s comparisons compare the driving beam with the internal phase to control the phase of the outgoing signal. This force has been characterized by a high degree of phase uniformity; if the pilot beam is lost for any reason the phase control value fails and the microwave power beam is automatically defocused. ^[79]Such a system would be incapable of focusing its power beam anywhere that did not have a pilot beam transmitter. The long-term effects of beaming through the ionosphere in the form of microwaves has yet to be studied, but nothing has been suggested.

Timeline

In the 20th century

• 1941 : Isaac Asimov published the science fiction short story “Reason,” in which a space station transmits energy collected from the sun to various planets using microwave beams.
• 1968 : Dr. Peter Glaser introduces the concept of a “solar power satellite” system with square miles of solar collectors in high geosynchronous orbit for the collection and conversion of sun’s energy into a microwave beam to transmit usable energy to large receiving antennas ( rectennas ) on Earth for distribution.
• 1973 : Dr. Peter Glaser is granted United States patent number 3,781,647 for his method of transmitting power over long distances using microwaves from a large (one square kilometer) antenna on the satellite to a much larger one on the ground, now known as a rectenna . ^[7]
• 1978-81 : The United States Department of Energy and NASA examines the solar power satellite (SPS) extensively concept, publishing design and feasibility studies.
• 1987 : Stationary High Altitude Relay Canadian Experiment
• 1995-97 : NASA conducts a “Fresh Look” study of space solar power (SSP) concepts and technologies.
• 1998 : The Space Solar Power Concept Definition Study (CDS) identified credible, commercially viable SSP concepts, while pointing out technical and programmatic risks.
• 1998 : Japan’s space agency begins developing a Space Solar Power System (SSPS), a program that continues today. ^{[ quote needed ]}
• 1999 : NASA’s Space Solar Power Exploratory Research and Technology Program ( SERT, see below ) begins.
• 2000 : John Mankins of NASA testifies in the US House of Representatives , saying “Large-scale SSP is a very complex integrated system of systems that requires many significant advances in technology and technology. for the most needed advances – albeit over several decades. ^[11]

In the 21st century

• 2001 : NASDA (one of Japan’s national space agencies before it became part of JAXA ) announces plans to perform additional research and prototyping by launching an experimental satellite with 10 kilowatts and 1 megawatt of power. ^[83] [84]
• 2003 : ESA studies ^[85]
• 2007 : The US Pentagon ‘s National Security Space Office (NSSO) from a postponement ^[86] on October 10, 2007 Stating They INTEND to collect solar energy from space for use on Earth to help the United States’ Ongoing relationship with the Middle East and the battle for oil. A demo plant could cost $ 10 billion, produce 10 megawatts, and become operational in 10 years. ^[87]
• 2007 : In May 2007 a workshop is held at the Massachusetts Institute of Technology (MIT) to review the current state of the SBSP market and technology. ^[88]
• 2010 : Professors Andrea Massa and Giorgio Franceschetti announce a special session on the “Analysis of Electromagnetic Wireless Systems for Solar Power Transmission” at the 2010 Institute of Electrical and Electronics Engineers International Symposium on Antennas and Propagation. ^[89]
• 2010 : The Indian Space Research Organization and US ‘National Space Society launched a joint venture to enhance solar energy through solar collectors. Called the Kalam-NSS Initiative after the former Indian President Dr. APJ Abdul Kalam , the forum will join the groundwork for the space-based solar energy program. ^[90]
• 2010: Sky’s No Limit: Space-Based Solar Power, the next major step in the Indo-US Strategic Partnership? Written by USAF Lt. Col. Peter Garretson was published at the Institute for Defense Studies and Analysis. ^[91]
• 2012 : China proposed joint development between India and China developing a solar power satellite, during a visit by Indian Judge Dr. APJ Abdul Kalam . ^[92]
• 2015 : JAXA announced on 12 March 2015 that they wirelessly beamed 1.8 kilowatts 50 meters to a small receiver by converting electricity to microwaves and then back to electricity. ^[34] [35]
• 2016: Lt Gen. Zhang Yulin, deputy chief of the Central Military Commission, suggested that China would have to start exploiting Earth-Moon space for industrial development. The goal would be the construction of space-based solar power satellites that would beam energy back to Earth. ^[93] [94]
• 2016: A team with membership of the Naval Research Laboratory (NRL), Defense Advanced Projects Agency (DARPA), Air Force Air University, Joint Staff Logistics (D-4), Department of State, Makins Aerospace and Northrop Grumman won the Secretary of Defense Defense (SECDEF) / Secretary of State (SECSTATE) / USAID Director’s agency-wide D3 (Diplomacy, Development, Defense) Innovation Challenge with a proposal that the US must lead in space solar power. The proposal was followed by a vision video
• 2016: Citizens for Space-Based Solar Power has turned into a hot topic on the White House Website “America Must Lead the Transition to Space-Based Energy” and Change.org “USA Must Lead the Transition to Space-Based Energy” along with the following video .
• 2016: Erik Larson and others from NOAA Produce a paper “Global atmospheric response to broadcasts from a Proposed reusable space launch system” ^[95] The paper Makes a box that up to 2 TW / year of power satellites Could Be constructed without intolerable damage to the atmosphere. Before this paper there was concern that the NOx produced by Reentry would destroy too much ozone.

Timeline

In the 20th century

• 1941 : Isaac Asimov published the science fiction short story “Reason,” in which a space station transmits energy collected from the sun to various planets using microwave beams.
• 1968 : Dr. Peter Glaser introduces the concept of a “solar power satellite” system with square miles of solar collectors in high geosynchronous orbit for the collection and conversion of sun’s energy into a microwave beam to transmit usable energy to large receiving antennas ( rectennas ) on Earth for distribution.
• 1973 : Dr. Peter Glaser is granted United States patent number 3,781,647 for his method of transmitting power over long distances using microwaves from a large (one square kilometer) antenna on the satellite to a much larger one on the ground, now known as a rectenna . ^[7]
• 1978-81 : The United States Department of Energy and NASA examines the solar power satellite (SPS) extensively concept, publishing design and feasibility studies.
• 1987 : Stationary High Altitude Relay Canadian Experiment
• 1995-97 : NASA conducts a “Fresh Look” study of space solar power (SSP) concepts and technologies.
• 1998 : The Space Solar Power Concept Definition Study (CDS) identified credible, commercially viable SSP concepts, while pointing out technical and programmatic risks.
• 1998 : Japan’s space agency begins developing a Space Solar Power System (SSPS), a program that continues today. ^{[ quote needed ]}
• 1999 : NASA’s Space Solar Power Exploratory Research and Technology Program ( SERT, see below ) begins.
• 2000 : John Mankins of NASA testifies in the US House of Representatives , saying “Large-scale SSP is a very complex integrated system of systems that requires many significant advances in technology and technology. for the most needed advances – albeit over several decades. ^[11]

In the 21st century

• 2001 : NASDA (one of Japan’s national space agencies before it became part of JAXA ) announces plans to perform additional research and prototyping by launching an experimental satellite with 10 kilowatts and 1 megawatt of power. ^[83] [84]
• 2003 : ESA studies ^[85]
• 2007 : The US Pentagon ‘s National Security Space Office (NSSO) from a postponement ^[86] on October 10, 2007 Stating They INTEND to collect solar energy from space for use on Earth to help the United States’ Ongoing relationship with the Middle East and the battle for oil. A demo plant could cost $ 10 billion, produce 10 megawatts, and become operational in 10 years. ^[87]
• 2007 : In May 2007 a workshop is held at the Massachusetts Institute of Technology (MIT) to review the current state of the SBSP market and technology. ^[88]
• 2010 : Professors Andrea Massa and Giorgio Franceschetti announce a special session on the “Analysis of Electromagnetic Wireless Systems for Solar Power Transmission” at the 2010 Institute of Electrical and Electronics Engineers International Symposium on Antennas and Propagation. ^[89]
• 2010 : The Indian Space Research Organization and US ‘National Space Society launched a joint venture to enhance solar energy through solar collectors. Called the Kalam-NSS Initiative after the former Indian President Dr. APJ Abdul Kalam , the forum will join the groundwork for the space-based solar energy program. ^[90]
• 2010: Sky’s No Limit: Space-Based Solar Power, the next major step in the Indo-US Strategic Partnership? Written by USAF Lt. Col. Peter Garretson was published at the Institute for Defense Studies and Analysis. ^[91]
• 2012 : China proposed joint development between India and China developing a solar power satellite, during a visit by Indian Judge Dr. APJ Abdul Kalam . ^[92]
• 2015 : JAXA announced on 12 March 2015 that they wirelessly beamed 1.8 kilowatts 50 meters to a small receiver by converting electricity to microwaves and then back to electricity. ^[34] [35]
• 2016: Lt Gen. Zhang Yulin, deputy chief of the Central Military Commission, suggested that China would have to start exploiting Earth-Moon space for industrial development. The goal would be the construction of space-based solar power satellites that would beam energy back to Earth. ^[93] [94]
• 2016: A team with membership of the Naval Research Laboratory (NRL), Defense Advanced Projects Agency (DARPA), Air Force Air University, Joint Staff Logistics (D-4), Department of State, Makins Aerospace and Northrop Grumman won the Secretary of Defense Defense (SECDEF) / Secretary of State (SECSTATE) / USAID Director’s agency-wide D3 (Diplomacy, Development, Defense) Innovation Challenge with a proposal that the US must lead in space solar power. The proposal was followed by a vision video
• 2016: Citizens for Space-Based Solar Power has turned into a hot topic on the White House Website “America Must Lead the Transition to Space-Based Energy” and Change.org “USA Must Lead the Transition to Space-Based Energy” along with the following video .
• 2016: Erik Larson and others from NOAA Produce a paper “Global atmospheric response to broadcasts from a Proposed reusable space launch system” ^[95] The paper Makes a box that up to 2 TW / year of power satellites Could Be constructed without intolerable damage to the atmosphere. Before this paper there was concern that the NOx produced by Reentry would destroy too much ozone.

Non-typical configurations and architectural considerations

The typical reference system-of-systems involves a large number of individual satellites in GEO (multi-gigawatt systems of service or significant portion of Earth’s energy requirements). The typical reference design for the individual satellite is in the 1-10 GW range and usually involves planar or concentrated solar photovoltaic (PV) as the energy collector / conversion. The most typical transmission designs are in the 1-10 GHz (2.45 or 5.8 GHz) RF band where there are minimum losses in the atmosphere. Materials for the satellites are sourced from, and manufactured on Earth and expected to be transported to LEO via re-usable rocket launch, and transported between LEO and GEO via chemical or electrical propulsion. In summary, the architecture choices are:

• Location = GEO
• Energy Collection = PV
• Satellite = Monolithic Structure
• Transmission = RF
• Materials & Manufacturing = Earth
• Installation = RLVs to LEO, Chemical to GEO

There are several interesting design variants from the reference system:

Alternate energy collection location : While GEO is most typical because of its advantages in the field of earthquake

• Sun Earth L1: Robert Kennedy III, Ken Roy & David Fields have proposed a variant of the L1 sunshade called “Dyson Dots” ^[96] where a multi-terawatt primary collector would beam energy back to a series of LEO sun-synchronous satellite receivers . The much farther distance to Earth requires a correspondingly larger transmission aperture.
• Lunar Surface : Dr. David Criswell has proposed the Lunar surface itself as a collection of medium, beaming power to the ground via a series of microwave reflectors in Earth Orbit. The chief advantage of this approach would be the ability to manufacture solar collectors in-situ with the energy cost and complexity of launch. Disadvantages include the long distance, the requirement for larger transmission systems, the required “overbuild” to deal with the lunar night, and the difficulty of sufficient manufacturing and pointing satellites. ^[97]
• MOE: MEO systems have been proposed for in-space utilities and beam-power propulsion infrastructures. For example, see Royce Jones’ paper. ^[98]
• Highly Elliptical Orbits: Molniya, Tundra, or Quazi Zenith orbits have been proposed for early niche markets, requiring less energy to access and providing good persistence. ^[99]
• Sun-Sync LEO: In this near Polar Orbit, the satellites need to be able to face the Sun as they rotate around Earth. This is an easy to access orbit requiring far less energy, and its proximity to Earth requires smaller (and therefore less massive) transmitting apertures. However, it is important to understand this approach when it comes to receiving stations, or storing energy for a burst transmission. This orbit is already crowded and has significant debris space.
• Equatorial LEO: Japan ‘s SPS 2000 proposed an early demonstrator in equatorial LEO in which multiple equatorial participating nations could receive some power. ^[100]
• Earth’s Surface : Dr. Narayan Komerath has proposed a space power grid where the energy of an existing grid or power plant on one side of the planet can be passed to orbit, across to another satellite and down to receivers. ^[101]

Energy Collection: The most typical designs for Solar Power Satellites include photovoltaics. These may be planar (and usually passively cooled), concentrated (and maybe actively cooled). However, there are multiple interesting variants.

• Solar Thermal: Proponents of Solar Thermal in the United States. Advantages of this method may include an overall system mass (disputed), non-degradation due to solar-wind damage, and radiation tolerance. One recent thermal solar power design by Keith Henson has been visualized here.
• Solar Pumped Laser: Japan has pursued a solar-pumped laser, where sunlight directly excites the lasing medium used to create the coherent beam to Earth.
• Fusion Decay: This version of a power-satellite is not “solar”. Rather, the vacuum of space is a “feature not a bug” for traditional fusion. Per Dr. Paul Werbos, after fusion even particles in a large volume would allow direct conversion to current. ^{[ quote needed ]}
• Solar Wind Loop : Also called Dyson-Harrop satellite satellite. Here the satellite makes use of the photons from the Sun but rather the particles in the solar coil which is electro-magnetic coupling generated in a large loop.
• Direct Mirrors: Early concepts for a direct mirror re-direction of light to earth. Dr. Lewis Fraas has explored an array of parabolic mirrors to augment existing solar arrays. ^[102]

Alternate Satellite Architecture: The typical satellite is a monolithic structure composed of a structural truss, one or more collectors, one or more transmitters, and sometimes primary and secondary reflectors. The entire structure can be gravity gradient stabilized. Alternative designs include:

• Swarms of Smaller Satellites : Some designs offers swarms of free-flying smaller satellites. This is the case with several laser designs, and appears with CALTECH’s Flying Carpets. ^[103] For RF designs, an engineering constraint is the sparse array problem.
• Free Floating Components : Solaren has proposed an alternative to the monolithic structure where the primary reflector and transmission reflector are free-flying. ^[104]
• Spin Stabilization: NASA explored a spin-stabilized thin film concept.
• Photonic Laser Thruster (PLT) stabilized structure: Dr. Young Bae has proposed that photon pressure may be substituted for compressive members in large structures.

Transmission: The most typical design for energy transmission is via an RF antenna at below 10 GHz to a rectenna on the ground. Controversy exists between the benefits of Klystrons, Gyrotrons, Magnetrons and solid state. Alternate transmission approaches include:

• Laser: Lasers offers the advantage of much lower cost, but there is controversy about benefits of efficiency. Lasers allow for much smaller transmitting and receiving apertures. However, a highly concentrated beam has eye-safety, fire safety, and weaponization concerns. Proponents believe they have answers to all these questions. A laser-based approach must also find alternate ways of coping with precipitation.
• Atmospheric Waveguide: Somewhat proposed it may be possible to use a short pulse laser to create an atmospheric waveguide through which concentrated microwaves could flow. ^{[105] [106] [107]}
• Scalar: Some have even speculated it may be possible to transmit power through scalar waves. ^[108]

Materials and Manufacturing: Existing on the Earth, and the use of earth based materials for the satellite and propellant. Variants include:

• Lunar Materials: Designs exist for Solar Power Satellites that source> 99% of materials from lunar regolith with very small inputs of “vitamins” from other locations. Using materials from the Moon is attractive because of the Moon is in theory far less complicated than from Earth. There is no atmosphere, and so components do not need to be packed tightly in an aeroshell and survive vibration, pressure and temperature loads. Launch may be via a magnetic mass driver and the requirement to use propellant for launch entirely. Launch from the Moon the GEO also requires far less than Earth’s much deeper gravity well. Building all the solar power satellites to fully supply the planet requires one millionth of the mass of the Moon.
• Self-Replication on the Moon: NASA explored a self-replicating factory on the Moon in 1980. ^[109] More recently, Justin Lewis-Webber proposed a method of speciated manufacturing of core elements ^[110] based on John Mankins SPS-Alpha Design . ^[111] [112]
• Asteroidal Materials: Some asteroids are thought to have lower temperatures than those of the Moon, and some of these materials may be more concentrated or easier to access.
• In-Space / In-Situ Manufacturing: With the advent of in-space additive manufacturing, such concepts as SpiderFab might allow mass launch of raw materials for local extrusion. ^[113]

Method of Installation / Transportation of Material to Energy Collection : In the reference designs, component material is launched via well-named chemical rockets (usually fully reusable launch systems) to LEO, after which the chemical or electrical propulsion is used to carry them GEO. The desired characteristics for this system is very high mass-flow at low total cost. Alternate concepts include:

• Lunar Chemical Launch : ULA has recently showcased a concept for a fully re-usable chemical lander to move the materials from the Lunar surface to LLO or GEO. ^[114]
• Lunar Mass Driver : Launch of materials from the lunar surface using a similar system to an aircraft carrier electromagnetic catapult. An unexplored compact alternative would be the slingatron.
• Lunar Space Elevator : An equatorial or near-equatorial cable extends to and through the lagrange point. This is a proposal for a traditional mass driver.
• Space Elevator : A ribbon of pure carbon nanotubes extends from its center of gravity in Geostationary orbit, allowing climbers to climb up to GEO. Problems with this problem, the definition of a ribbon of such length with adequate strength, management of collisions with satellites and space debris, and lightning.
• MEO Skyhook: As part of an AFRL study, Roger Lenard proposed to MEO Skyhook. It appears that gravity gradient-stabilized with its center of mass in MEO can be constructed of available materials. The bottom of the sky is a non-keplerian orbit. A re-usable rocket can launch to match altitude and speed with the bottom of the tether which is in a non-keplerian orbit (tracking much slower than typical orbital speed). The payload is up and it climbs the cable. The cable itself is kept from de-orbiting via electric propusion and / or electromagnetic effects.
• MAGLEV Launch / StarTram : John Powell has a concept for a very high mass flow system. In a first-gen system, built into a mountain, accelerates a payload through an evacuated MAGLEV track. A small on-board rocket circulizes the payload. ^[115]
• Beamed Energy Launch: Kevin Parkin and Escape Dynamics both have concepts ^[116] for ground-based irradiation of a mono-propellant launch vehicle using RF energy. The RF energy is absorbed and directly heats the propellant not unlike in NERVA-style nuclear-thermal. LaserMotive has a concept for a laser-based approach.

In fiction

Space stations transmitting solar power have appeared in science fiction works like Isaac Asimov ‘s ” Reason ” (1941), which centers around the troubles caused by the robots operating the station. Asimov’s short story ” The Last Question ” also features the use of SBSP to provide limited energy for use on Earth. Ben Bova’s thriller PowerSat involves a billionaire bent on creating a solar powersat while others try to sabotage it.

In the video game Sid Meier Alpha Centauri , the player can build a city called “Orbital Power Transmitter” which, while expensive, provides energy to all other cities. Constructing many of these results in huge bonuses for energy production for all cities the player owns. In the novel “Skyfall” (1976) by Harry Harrison, an attempt to launch the core of powers of a captive orbit. Several SimCity games have featured space-microwave power plants as buildable options for municipal energy, along with (unrealistic) disaster scenarios where the beam strays off the collector and sets fire to nearby areas. In the manga and animeMobile Suit Gundam 00 , an orbital ring containing multiple solar collectors and microwave transmitters, along with power stations and space elevators for carrying power back to Earth’s surface, are the primary source of electricity for the Earth in the 24th century.

Various aerospace companies also showcased imaginative future solar power satellites in their corporate vision videos, including the Boeing You Just Wait , Lockheed Martin’s The Next 100 Years , and the United Launch Alliance CIS-Lunar 1000 .