The document proposes a new concept for interstellar propulsion using a spherical thin-film photovoltaic structure to harness ambient light for power generation. Integrated diode lasers powered by the photovoltaic structure would emit photons in a single direction to provide thrust without onboard propellant. The concept aims to take advantage of isotropic radiation environments like between stars or within nebulae. However, the analysis finds that extremely low available power from distant stars and long transit times exceeding component lifetimes make the concept impractical for interstellar travel.
This document discusses recent advances in rocket propulsion technologies, focusing on interplanetary and interstellar flight applications. It describes deuterium micro-bomb rocket propulsion which uses a proton beam to ignite a fusion explosive, generating thrust. Relativistic propulsion concepts are also discussed, including photon propulsion and antimatter annihilation. The most promising approach proposed is a matter-antimatter gigaelectron volt gamma ray laser rocket which could achieve relativistic velocities through the complete conversion of mass to radiation via proton-antiproton annihilation. However, challenges to the practical implementation of antimatter propulsion systems remain due to the extremely inefficient production of antimatter.
Preparing interstellar travel with ultrafast beam-powered lightsailsAdvanced-Concepts-Team
This document discusses proposals for interstellar travel using beam-powered propulsion techniques. It presents three main classifications of interstellar travel: 1) Relativistic reaction propulsion using nuclear or antimatter rockets, 2) Spacetime distortions requiring exotic matter, and 3) Generation ships. It then focuses on the basics and applications of radiation propulsion, including solar and beam-powered light sails. Models are presented for photon rocket kinematics, single trips to Alpha Centauri using antimatter rockets and beam-powered sails, and a two-stage laser-pushed sail concept for roundtrips requiring much less energy than other proposals.
Fusion-powered rockets could enable much faster and longer trips throughout the solar system compared to chemical rockets. A small-scale approach to fusion propulsion involves using the propellant to compress and heat plasma to fusion conditions, channeling the fusion energy into heating the propellant. As the hot propellant passes through a magnetic nozzle, its thermal energy is converted to directed propulsive energy and electricity. My idea is to use D-T fusion reactions, where deuterium and tritium plasmas fuse to form an alpha particle and neutron with 17.6 MeV of energy. The accelerated alpha particle could provide high thrust for a long-duration plasma engine.
1. The document proposes an optical power infrastructure in Earth-moon space using lasers powered by concentrated sunlight to distribute power virtually anywhere and anytime.
2. It identifies four technical advances needed: concentrating sunlight to saturate a laser gain medium, removing heat without distortion, exciting the lowest order laser mode, and converting laser light to electricity efficiently.
3. Experiments are proposed to demonstrate key mechanisms at small scale, with the goal of maturing the technologies to eventually enable large-scale distribution of optical power throughout the Earth-moon system.
This document provides information on ion propulsion systems and solar sails. It discusses the key components of an ion propulsion system including the power source, propellant management system, and ion thruster. It describes how ion propulsion works by ionizing and accelerating ions using electricity to generate thrust. Solar sails are also introduced, using sunlight's radiation pressure for propulsion. Challenges in solar sail design like packaging and deploying large sails are discussed. CubeSats are mentioned as a potential core for solar sail missions, and various tests done before launch are summarized.
1. David Goodwin proposes an electromagnetic propulsion system for spacecraft that uses supercooled electromagnets vibrating at 400,000 times per second to provide thrust.
2. The system would use a nuclear reactor to power solid-state switches that pulse the electromagnets, generating a vibration that could theoretically propel a spacecraft at a fraction of 1% the speed of light.
3. While speculative, if successful the system could enable missions to the edge of the solar system and beyond, faster than any chemical rockets. Testing is needed to determine if the magnets can truly generate unidirectional thrust.
1) The document discusses the potential for reducing CO2 emissions in Kosovo by replacing fossil fuels with solar energy. Over 92% of Kosovo's electricity currently comes from burning fossil fuels.
2) Advanced solar technologies could provide an unused source of renewable energy in Kosovo. Kosovo has a sufficient number of sunny days each year and optimal temperatures for solar radiation according to measurements.
3) Investing in efficient solar technologies like LED lighting systems, solar panels, and photovoltaic systems could help protect the environment from the impacts of CO2 and greenhouse gases while providing a sustainably managed energy system.
This document discusses recent advances in rocket propulsion technologies, focusing on interplanetary and interstellar flight applications. It describes deuterium micro-bomb rocket propulsion which uses a proton beam to ignite a fusion explosive, generating thrust. Relativistic propulsion concepts are also discussed, including photon propulsion and antimatter annihilation. The most promising approach proposed is a matter-antimatter gigaelectron volt gamma ray laser rocket which could achieve relativistic velocities through the complete conversion of mass to radiation via proton-antiproton annihilation. However, challenges to the practical implementation of antimatter propulsion systems remain due to the extremely inefficient production of antimatter.
Preparing interstellar travel with ultrafast beam-powered lightsailsAdvanced-Concepts-Team
This document discusses proposals for interstellar travel using beam-powered propulsion techniques. It presents three main classifications of interstellar travel: 1) Relativistic reaction propulsion using nuclear or antimatter rockets, 2) Spacetime distortions requiring exotic matter, and 3) Generation ships. It then focuses on the basics and applications of radiation propulsion, including solar and beam-powered light sails. Models are presented for photon rocket kinematics, single trips to Alpha Centauri using antimatter rockets and beam-powered sails, and a two-stage laser-pushed sail concept for roundtrips requiring much less energy than other proposals.
Fusion-powered rockets could enable much faster and longer trips throughout the solar system compared to chemical rockets. A small-scale approach to fusion propulsion involves using the propellant to compress and heat plasma to fusion conditions, channeling the fusion energy into heating the propellant. As the hot propellant passes through a magnetic nozzle, its thermal energy is converted to directed propulsive energy and electricity. My idea is to use D-T fusion reactions, where deuterium and tritium plasmas fuse to form an alpha particle and neutron with 17.6 MeV of energy. The accelerated alpha particle could provide high thrust for a long-duration plasma engine.
1. The document proposes an optical power infrastructure in Earth-moon space using lasers powered by concentrated sunlight to distribute power virtually anywhere and anytime.
2. It identifies four technical advances needed: concentrating sunlight to saturate a laser gain medium, removing heat without distortion, exciting the lowest order laser mode, and converting laser light to electricity efficiently.
3. Experiments are proposed to demonstrate key mechanisms at small scale, with the goal of maturing the technologies to eventually enable large-scale distribution of optical power throughout the Earth-moon system.
This document provides information on ion propulsion systems and solar sails. It discusses the key components of an ion propulsion system including the power source, propellant management system, and ion thruster. It describes how ion propulsion works by ionizing and accelerating ions using electricity to generate thrust. Solar sails are also introduced, using sunlight's radiation pressure for propulsion. Challenges in solar sail design like packaging and deploying large sails are discussed. CubeSats are mentioned as a potential core for solar sail missions, and various tests done before launch are summarized.
1. David Goodwin proposes an electromagnetic propulsion system for spacecraft that uses supercooled electromagnets vibrating at 400,000 times per second to provide thrust.
2. The system would use a nuclear reactor to power solid-state switches that pulse the electromagnets, generating a vibration that could theoretically propel a spacecraft at a fraction of 1% the speed of light.
3. While speculative, if successful the system could enable missions to the edge of the solar system and beyond, faster than any chemical rockets. Testing is needed to determine if the magnets can truly generate unidirectional thrust.
1) The document discusses the potential for reducing CO2 emissions in Kosovo by replacing fossil fuels with solar energy. Over 92% of Kosovo's electricity currently comes from burning fossil fuels.
2) Advanced solar technologies could provide an unused source of renewable energy in Kosovo. Kosovo has a sufficient number of sunny days each year and optimal temperatures for solar radiation according to measurements.
3) Investing in efficient solar technologies like LED lighting systems, solar panels, and photovoltaic systems could help protect the environment from the impacts of CO2 and greenhouse gases while providing a sustainably managed energy system.
This document discusses solar power and recent advances in solar cell technology. It notes that the Earth receives 174 petawatts of solar radiation annually and photovoltaics can convert solar energy directly into electricity using semiconductors. Recent innovations have led to solar cells that are over 40% efficient at converting sunlight to electricity and utilize multiple semiconductor materials or junctions to capture more of the solar spectrum. These technical advances could make solar electricity cost competitive with other energy sources.
This document presents research on the feasibility of using radioisotope-based electron sources for space applications. It introduces two new types of space propulsion systems: the Minaka thruster and Kabila thruster. The Minaka thruster uses clusters of self-powered radioisotope cells to generate micro-newtons of thrust. It applies the principle of self-sufficiency to power the radioisotope electron sources. The Kabila thruster uses a hollow cathode with a radioisotope heat source instead of a conventional heater. It was found to save up to 3% in overall power compared to conventional ion thrusters. Both systems aim to overcome the energetic limitations of traditional space propulsion through novel use of radioisotopes
The document provides an overview of solar sails, including their history, design, challenges, applications, and future. Solar sails use sunlight pressure on large, lightweight sails to propel spacecraft without the need for onboard fuel. Key points covered include different sail designs (square, spinning discs), materials used, deployment challenges, and recent solar sail missions by Japan and NASA. Potential future uses include exploration of the solar system and delivering payloads. Maintaining the large, delicate sails remains a technical challenge to enable more ambitious solar sailing missions.
1. Electrodynamic tethers use the interaction between electric current in a conducting tether and Earth's magnetic field to propel spacecraft. As the tether moves through the magnetic field, a voltage is induced along its length.
2. When current is run through the tether, the Lorentz force from the magnetic field can be used for propulsion. Current can be collected from ionospheric plasma to de-orbit a satellite or an external power source can overcome the induced voltage to boost an orbit.
3. Tethers provide propellantless propulsion and can lower the cost of in-space transportation by reducing the need to launch propellant from Earth. Potential applications include de-orbiting satellites
The document discusses a proposed system to remove space debris using a small microsatellite. It would use an electrodynamic tether (EDT) technology, which allows orbital transfers without propellant. The microsatellite would have a compact design, thrusters for maneuvering, sensors for navigation, and an extensible robotic arm to capture debris. It describes the key components like the EDT, release mechanism, reel mechanism, navigation sensors, and robotic arm. The system aims to provide an affordable way to actively remove large debris from useful orbits and address the growing issue of space debris.
Ed Friedman traveled to CERN in Geneva, Switzerland on June 8, 2012. While there, he took a tour of CERN headquarters and control rooms, and visited the Compact Muon Solenoid experiment. The CMS experiment uses a particle detector to investigate physics including the search for the Higgs boson and dark matter. Friedman's special access included a lecture on the status of the Higgs boson discovery.
The document summarizes a proposal for a fission fragment rocket engine (FFRE) capable of powering spacecraft. Key points:
- The FFRE uses suspended plutonium carbide dust grains that undergo fission, producing fragments that are directed out the nozzle at 1.7% the speed of light, generating thrust.
- Initial designs suggest the FFRE could provide 10s to 100s of pounds of continuous thrust for years, with a specific impulse over 500,000 seconds.
- Preliminary assessments found a FFRE-powered spacecraft could travel faster and with more payload than current chemical or nuclear designs, enabling missions to Jupiter within 8 years round trip.
- While the concept is
This document summarizes a seminar on solar sails. It discusses the physical principles behind solar sails, how they use radiation pressure for propulsion. It describes different sail configurations that have been proposed, including square, disk, and electric or magnetic field-based designs. The document also discusses challenges like attitude control and testing solar sails in Earth's atmosphere. It provides examples of solar sail materials like aluminum, kapton, and carbon fiber. The first successful deployment of a solar sail in space by the Japanese space agency JAXA in 2010 is also mentioned.
A 1 km^2 solar sail placed at Earth's orbit would experience a radiation pressure force of around 9 N from the Sun. This light pressure force could counteract the Sun's gravitational pull on the sail if the sail's area to mass ratio is greater than 663 m^2/kg. For an aluminum solar sail to achieve equilibrium, it would need to be extremely thin, with a thickness of around 570 nm.
Space solar power involves collecting solar energy via satellites in space and transmitting it to Earth via microwave beams. Peter Glaser was granted a patent in 1973 for transmitting power over long distances from a satellite to Earth using microwaves. A space solar power system would consist of solar panels on satellites to collect energy from the sun, which would then be converted to microwaves and transmitted to receiving antennas on Earth. Some benefits include availability 24/7 regardless of weather and no greenhouse gas emissions, but challenges include very high development costs. Potential applications include power delivery to Earth and powering drones.
The document discusses the technical challenges facing the development of space solar power (SSP). Key points include:
1) SSP could help address global energy needs and climate change by providing large-scale carbon-neutral energy from geostationary orbit.
2) Major challenges include developing technologies for very large solar arrays and wireless power transmission over long distances from space to Earth.
3) Significant improvements have been made, but constructing multi-gigawatt SSP systems will require overcoming challenges in areas like lightweight structures, high-power wireless power transmission, and modular satellite assembly and deployment.
This document proposes developing an ultra-light solar sail without a plastic backing for use in interstellar travel. It summarizes the proposed scope of work, which includes analyzing the reflectivity and engineering constraints of nanometer-thick aluminum sheets and grids, as well as doped carbon nanotubes. Preliminary analyses show these ultra-light concepts could achieve accelerations over 100 times greater than conventional solar sails and reach distances like Pluto in months or 10,000 AU in decades. The document recommends a Phase II experimental program to fabricate and test nanoscale reflectors and verify their properties.
Solar sails use radiation pressure from the sun for propulsion and have minimal moving parts. They produce very small thrusts but can be used repeatedly over long periods. A seminar discussed the physical principles behind solar radiation pressure and how it produces small forces on sails. Attitude control is needed to maintain the craft's orientation against various forces. Testing is challenging on Earth but applications could include satellites for trajectory corrections and missions close to the sun. Various sail configurations and materials have been proposed but deployment challenges have limited real-world testing until Japan's 2010 IKAROS mission, the first to use a solar sail as a primary propulsion system.
The document proposes a new concept for fusion propulsion that could enable faster space travel. It involves using the kinetic energy of fusion products like alpha particles directly for thrust generation, without needing to convert the energy to electricity first. This would be done through two processes: 1) transferring energy electrostatically from fast alpha particle bunches to slower, denser ion bunches, and 2) using the magnetic field of the dense bunches to push against and accelerate another bunch of ions for thrust. Near-term experimental plans are described to test aspects of this direct energy-to-thrust conversion process using an existing plasma device at the University of Illinois.
“The theoretical analysis result suggests that the impulsive electric field applied to the dielectric material may produce a sufficient artificial gravity to attain velocities comparable to chemical rockets.” ―Dr. Takaaki Musha
People: Al Bielek, Alcubierre, Andrew Bahnion, André Füzfa, Athanassios Nassikas, Biefeld, Bruce dePalma, Bud Rieken, Casimer, Cassenti, Dan Davidson, Daniel D. Home, David Cowlishaw, David Hammel, David Hooper, Dishington, Don Kelly, Douglas Torr, Dr. Albert Einstein, Dr. Berthart Heim, Dr. Charles F. Brush, Dr. Ed Witten, Dr. Edward Teller, Dr. Erwin Saxl, Dr. Eugene Podkletnov, Dr. Francis Nipher, Dr. Fredrick Alzofon, Dr. Ning Li, Dr. Richard Clark, Dr. Richard Clarke, Dr. Robert Dicke, Dr. Robert Forward, Dr. Schuman, Dr. Willaim Crookes, Dr. William Hooper., Ed Leedskelstein, Eric Laithwaite, Erich Halik, Floyd Sweet, Fran McCabe, Frost, Guido Fetta, Halvosky, Hans Nieper, Harold Aspden, Harold Puthoff, Harold Wilson, Hawasaka, Henry Wallace, Hoyassaka, James Clerk Maxwell, James Cox, James Hartman, James King Jr., James Woodward., Jefimenko, John Hutchingson, John Keely, John R. R. Searl, John Schnurrer, Kellogg, Le Sage, Leroy Cook, Lt. Col. Corso, Marcel Pages, Mark Tomion, Misner, Modanese, Moebuis (Faile), Montimen Delroy, Naudin, Neil Sorenzen, Nikola Tesla, Norman Dean, Oliver Heaverside, Otis T. Carr, P.M.S. Blackett, Paramahamsa Tewari, Patrick Bailey, Peter Kummel, Poliakov, Randall Mill, Richard Foster, Robert Collins, Robert Lazar, Sandy Kidd, Schnurer, Scpott Strachan, Shinicki Seike, T. Townsend Brown, Thorne, Tom Bearden, Travis Taylor, Viktor Schauberger, W. D. Clendonon, W. Peschaka, Wheeler, Wilbur Smith, William Littlejohn, William Rhodes, Yamashita Huaro
“Dr. Forward defines six different kinds of antigravity in his "Indistinguishable from Magic" book: Aside from the obvious "weightloss" in freefall as an astronaut in orbit; the first is to place a very heavy mass overhead to cancel the earth's gravity field. Secondly, we may use ultradense materials spaced very closely to the object we desire to be weightless. The last Newtonian idea, is to use various "guard" masses to reduce tidal forces on a test mass already in orbit on the space shuttle. From Einstein's theory, comes a fourth idea; that moving ultradense matter in a toroidal coil at high speed will generate a dipolar G-field. Fifth, the idea of dragging of inertial frames, which will pull objects along with them. Lastly, the sixth idea, is the possibility of negative matter (-m), just like negative charge, will reverse the direction of force; it moves towards you when you push on it! Negative, matter along with positive matter, will take off into space forming a space drive! Could the superconductor of Dr. Podkletnov be a form of negative matter?” ―James E. Cox
Alcubierre's drive allows to circumvent the speed of light limit. They are building a Negative Energy Generator to realize it.
The document proposes a concept for a realistic interstellar explorer probe. Key points:
- The probe would travel to about 1000 AU, penetrating the local interstellar medium to study it scientifically.
- Technologies needed include high-Isp propulsion for an acceleration at perihelion, thermal shielding, long-range communications, and a radioisotope power source.
- A key challenge is accelerating the probe to high speeds (>20 AU/year) through a perihelion burn near the Sun leveraging its gravity and Oberth effect. Several propulsion concepts are considered like solar thermal, nuclear pulse, or nuclear thermal.
This presentation gives a brief concept (engineering related) about solar space propulsion. It is all about the travelling technology of satellite in the space world. Hope it helps !
This document presents an overview of space plasma physics, specifically magnetic storms and substorms. It provides basic definitions and examples to educate those unfamiliar or rusty with the science. The outline includes sections on storm and substorm basics, examples with analysis, and data collected from satellites. Magnetic storms occur over weeks/months when particles enhance the ring current. Substorms happen over hours in growth, onset/expansion, and recovery phases, seen through auroral observations and particle densities. Examples of data include images, magnetic and electric fields, and particle fluxes.
This document discusses solar power satellites (SPS) as a solution for providing 24-hour power supply from space using wireless power transmission via microwaves. It describes issues with the stability of early phased array and SPS systems for accurate targeting. It proposes a simulation method called PAC (position and angle correction) to correct the position of SPS using measurements from receiver antennas on panel structures. The document outlines various advantages of SPS such as being unaffected by day-night cycles or weather and occupying no land area. However, it also notes challenges such as the complexity, large size, and high cost of a prototype SPS system.
El documento presenta una serie de preguntas y respuestas sobre temas históricos como la democracia, revoluciones culturales y políticas de varios países en la década de 1960. También resume el contexto de disturbios sociales y políticos globales que ocurrieron en 1968, conocido como el "Año Mágico", cuando hubo revueltas estudiantiles y sociales en todo el mundo que desafiaron el statu quo. Además, compara los deberes ciudadanos con los deberes de un estudiante universitario en la sociedad ecu
This document discusses different types of light bulb sockets including E-27 sockets with threads and E-14 sockets with threads. It mentions portalamparas or light bulb sockets in the E-27 and E-14 sizes both with threads for screwing in light bulbs.
This document discusses solar power and recent advances in solar cell technology. It notes that the Earth receives 174 petawatts of solar radiation annually and photovoltaics can convert solar energy directly into electricity using semiconductors. Recent innovations have led to solar cells that are over 40% efficient at converting sunlight to electricity and utilize multiple semiconductor materials or junctions to capture more of the solar spectrum. These technical advances could make solar electricity cost competitive with other energy sources.
This document presents research on the feasibility of using radioisotope-based electron sources for space applications. It introduces two new types of space propulsion systems: the Minaka thruster and Kabila thruster. The Minaka thruster uses clusters of self-powered radioisotope cells to generate micro-newtons of thrust. It applies the principle of self-sufficiency to power the radioisotope electron sources. The Kabila thruster uses a hollow cathode with a radioisotope heat source instead of a conventional heater. It was found to save up to 3% in overall power compared to conventional ion thrusters. Both systems aim to overcome the energetic limitations of traditional space propulsion through novel use of radioisotopes
The document provides an overview of solar sails, including their history, design, challenges, applications, and future. Solar sails use sunlight pressure on large, lightweight sails to propel spacecraft without the need for onboard fuel. Key points covered include different sail designs (square, spinning discs), materials used, deployment challenges, and recent solar sail missions by Japan and NASA. Potential future uses include exploration of the solar system and delivering payloads. Maintaining the large, delicate sails remains a technical challenge to enable more ambitious solar sailing missions.
1. Electrodynamic tethers use the interaction between electric current in a conducting tether and Earth's magnetic field to propel spacecraft. As the tether moves through the magnetic field, a voltage is induced along its length.
2. When current is run through the tether, the Lorentz force from the magnetic field can be used for propulsion. Current can be collected from ionospheric plasma to de-orbit a satellite or an external power source can overcome the induced voltage to boost an orbit.
3. Tethers provide propellantless propulsion and can lower the cost of in-space transportation by reducing the need to launch propellant from Earth. Potential applications include de-orbiting satellites
The document discusses a proposed system to remove space debris using a small microsatellite. It would use an electrodynamic tether (EDT) technology, which allows orbital transfers without propellant. The microsatellite would have a compact design, thrusters for maneuvering, sensors for navigation, and an extensible robotic arm to capture debris. It describes the key components like the EDT, release mechanism, reel mechanism, navigation sensors, and robotic arm. The system aims to provide an affordable way to actively remove large debris from useful orbits and address the growing issue of space debris.
Ed Friedman traveled to CERN in Geneva, Switzerland on June 8, 2012. While there, he took a tour of CERN headquarters and control rooms, and visited the Compact Muon Solenoid experiment. The CMS experiment uses a particle detector to investigate physics including the search for the Higgs boson and dark matter. Friedman's special access included a lecture on the status of the Higgs boson discovery.
The document summarizes a proposal for a fission fragment rocket engine (FFRE) capable of powering spacecraft. Key points:
- The FFRE uses suspended plutonium carbide dust grains that undergo fission, producing fragments that are directed out the nozzle at 1.7% the speed of light, generating thrust.
- Initial designs suggest the FFRE could provide 10s to 100s of pounds of continuous thrust for years, with a specific impulse over 500,000 seconds.
- Preliminary assessments found a FFRE-powered spacecraft could travel faster and with more payload than current chemical or nuclear designs, enabling missions to Jupiter within 8 years round trip.
- While the concept is
This document summarizes a seminar on solar sails. It discusses the physical principles behind solar sails, how they use radiation pressure for propulsion. It describes different sail configurations that have been proposed, including square, disk, and electric or magnetic field-based designs. The document also discusses challenges like attitude control and testing solar sails in Earth's atmosphere. It provides examples of solar sail materials like aluminum, kapton, and carbon fiber. The first successful deployment of a solar sail in space by the Japanese space agency JAXA in 2010 is also mentioned.
A 1 km^2 solar sail placed at Earth's orbit would experience a radiation pressure force of around 9 N from the Sun. This light pressure force could counteract the Sun's gravitational pull on the sail if the sail's area to mass ratio is greater than 663 m^2/kg. For an aluminum solar sail to achieve equilibrium, it would need to be extremely thin, with a thickness of around 570 nm.
Space solar power involves collecting solar energy via satellites in space and transmitting it to Earth via microwave beams. Peter Glaser was granted a patent in 1973 for transmitting power over long distances from a satellite to Earth using microwaves. A space solar power system would consist of solar panels on satellites to collect energy from the sun, which would then be converted to microwaves and transmitted to receiving antennas on Earth. Some benefits include availability 24/7 regardless of weather and no greenhouse gas emissions, but challenges include very high development costs. Potential applications include power delivery to Earth and powering drones.
The document discusses the technical challenges facing the development of space solar power (SSP). Key points include:
1) SSP could help address global energy needs and climate change by providing large-scale carbon-neutral energy from geostationary orbit.
2) Major challenges include developing technologies for very large solar arrays and wireless power transmission over long distances from space to Earth.
3) Significant improvements have been made, but constructing multi-gigawatt SSP systems will require overcoming challenges in areas like lightweight structures, high-power wireless power transmission, and modular satellite assembly and deployment.
This document proposes developing an ultra-light solar sail without a plastic backing for use in interstellar travel. It summarizes the proposed scope of work, which includes analyzing the reflectivity and engineering constraints of nanometer-thick aluminum sheets and grids, as well as doped carbon nanotubes. Preliminary analyses show these ultra-light concepts could achieve accelerations over 100 times greater than conventional solar sails and reach distances like Pluto in months or 10,000 AU in decades. The document recommends a Phase II experimental program to fabricate and test nanoscale reflectors and verify their properties.
Solar sails use radiation pressure from the sun for propulsion and have minimal moving parts. They produce very small thrusts but can be used repeatedly over long periods. A seminar discussed the physical principles behind solar radiation pressure and how it produces small forces on sails. Attitude control is needed to maintain the craft's orientation against various forces. Testing is challenging on Earth but applications could include satellites for trajectory corrections and missions close to the sun. Various sail configurations and materials have been proposed but deployment challenges have limited real-world testing until Japan's 2010 IKAROS mission, the first to use a solar sail as a primary propulsion system.
The document proposes a new concept for fusion propulsion that could enable faster space travel. It involves using the kinetic energy of fusion products like alpha particles directly for thrust generation, without needing to convert the energy to electricity first. This would be done through two processes: 1) transferring energy electrostatically from fast alpha particle bunches to slower, denser ion bunches, and 2) using the magnetic field of the dense bunches to push against and accelerate another bunch of ions for thrust. Near-term experimental plans are described to test aspects of this direct energy-to-thrust conversion process using an existing plasma device at the University of Illinois.
“The theoretical analysis result suggests that the impulsive electric field applied to the dielectric material may produce a sufficient artificial gravity to attain velocities comparable to chemical rockets.” ―Dr. Takaaki Musha
People: Al Bielek, Alcubierre, Andrew Bahnion, André Füzfa, Athanassios Nassikas, Biefeld, Bruce dePalma, Bud Rieken, Casimer, Cassenti, Dan Davidson, Daniel D. Home, David Cowlishaw, David Hammel, David Hooper, Dishington, Don Kelly, Douglas Torr, Dr. Albert Einstein, Dr. Berthart Heim, Dr. Charles F. Brush, Dr. Ed Witten, Dr. Edward Teller, Dr. Erwin Saxl, Dr. Eugene Podkletnov, Dr. Francis Nipher, Dr. Fredrick Alzofon, Dr. Ning Li, Dr. Richard Clark, Dr. Richard Clarke, Dr. Robert Dicke, Dr. Robert Forward, Dr. Schuman, Dr. Willaim Crookes, Dr. William Hooper., Ed Leedskelstein, Eric Laithwaite, Erich Halik, Floyd Sweet, Fran McCabe, Frost, Guido Fetta, Halvosky, Hans Nieper, Harold Aspden, Harold Puthoff, Harold Wilson, Hawasaka, Henry Wallace, Hoyassaka, James Clerk Maxwell, James Cox, James Hartman, James King Jr., James Woodward., Jefimenko, John Hutchingson, John Keely, John R. R. Searl, John Schnurrer, Kellogg, Le Sage, Leroy Cook, Lt. Col. Corso, Marcel Pages, Mark Tomion, Misner, Modanese, Moebuis (Faile), Montimen Delroy, Naudin, Neil Sorenzen, Nikola Tesla, Norman Dean, Oliver Heaverside, Otis T. Carr, P.M.S. Blackett, Paramahamsa Tewari, Patrick Bailey, Peter Kummel, Poliakov, Randall Mill, Richard Foster, Robert Collins, Robert Lazar, Sandy Kidd, Schnurer, Scpott Strachan, Shinicki Seike, T. Townsend Brown, Thorne, Tom Bearden, Travis Taylor, Viktor Schauberger, W. D. Clendonon, W. Peschaka, Wheeler, Wilbur Smith, William Littlejohn, William Rhodes, Yamashita Huaro
“Dr. Forward defines six different kinds of antigravity in his "Indistinguishable from Magic" book: Aside from the obvious "weightloss" in freefall as an astronaut in orbit; the first is to place a very heavy mass overhead to cancel the earth's gravity field. Secondly, we may use ultradense materials spaced very closely to the object we desire to be weightless. The last Newtonian idea, is to use various "guard" masses to reduce tidal forces on a test mass already in orbit on the space shuttle. From Einstein's theory, comes a fourth idea; that moving ultradense matter in a toroidal coil at high speed will generate a dipolar G-field. Fifth, the idea of dragging of inertial frames, which will pull objects along with them. Lastly, the sixth idea, is the possibility of negative matter (-m), just like negative charge, will reverse the direction of force; it moves towards you when you push on it! Negative, matter along with positive matter, will take off into space forming a space drive! Could the superconductor of Dr. Podkletnov be a form of negative matter?” ―James E. Cox
Alcubierre's drive allows to circumvent the speed of light limit. They are building a Negative Energy Generator to realize it.
The document proposes a concept for a realistic interstellar explorer probe. Key points:
- The probe would travel to about 1000 AU, penetrating the local interstellar medium to study it scientifically.
- Technologies needed include high-Isp propulsion for an acceleration at perihelion, thermal shielding, long-range communications, and a radioisotope power source.
- A key challenge is accelerating the probe to high speeds (>20 AU/year) through a perihelion burn near the Sun leveraging its gravity and Oberth effect. Several propulsion concepts are considered like solar thermal, nuclear pulse, or nuclear thermal.
This presentation gives a brief concept (engineering related) about solar space propulsion. It is all about the travelling technology of satellite in the space world. Hope it helps !
This document presents an overview of space plasma physics, specifically magnetic storms and substorms. It provides basic definitions and examples to educate those unfamiliar or rusty with the science. The outline includes sections on storm and substorm basics, examples with analysis, and data collected from satellites. Magnetic storms occur over weeks/months when particles enhance the ring current. Substorms happen over hours in growth, onset/expansion, and recovery phases, seen through auroral observations and particle densities. Examples of data include images, magnetic and electric fields, and particle fluxes.
This document discusses solar power satellites (SPS) as a solution for providing 24-hour power supply from space using wireless power transmission via microwaves. It describes issues with the stability of early phased array and SPS systems for accurate targeting. It proposes a simulation method called PAC (position and angle correction) to correct the position of SPS using measurements from receiver antennas on panel structures. The document outlines various advantages of SPS such as being unaffected by day-night cycles or weather and occupying no land area. However, it also notes challenges such as the complexity, large size, and high cost of a prototype SPS system.
El documento presenta una serie de preguntas y respuestas sobre temas históricos como la democracia, revoluciones culturales y políticas de varios países en la década de 1960. También resume el contexto de disturbios sociales y políticos globales que ocurrieron en 1968, conocido como el "Año Mágico", cuando hubo revueltas estudiantiles y sociales en todo el mundo que desafiaron el statu quo. Además, compara los deberes ciudadanos con los deberes de un estudiante universitario en la sociedad ecu
This document discusses different types of light bulb sockets including E-27 sockets with threads and E-14 sockets with threads. It mentions portalamparas or light bulb sockets in the E-27 and E-14 sizes both with threads for screwing in light bulbs.
Sudarshan Ramakrishna Chetlur is a branding and advertising professional with over 23 years of experience. He has worked with various companies in different domains to develop branding strategies that focus on the human experience and portray brands as a form of "life". Some of the key campaigns and projects highlighted in his profile include developing corporate branding campaigns for Ranbaxy Laboratories and Fresenius Kabi Oncology, as well as product launches, advertising campaigns and collateral designs for brands like Quest Diagnostics and Kabigef. Testimonials from former clients praise his creativity, ability to listen to clients' needs, and talent for translating ideas into practical designs that deliver results.
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Iaetsd rf controlled sailing robot for oceanic missions
First Scientific Paper
1. Joint Conference of 30th ISTS, 34th IEPC and 6th NSAT, Kobe-Hyogo, Japan
July 4 – 10, 2015
1
Assessment of an Interstellar Photon Propulsion Concept
IEPC-2015-144/ISTS-2015-b-144
Presented at Joint Conference of 30th International Symposium on Space Technology and Science
34th International Electric Propulsion Conference and 6th Nano-satellite Symposium,
Hyogo-Kobe, Japan
July 4 – 10, 2015
John E. Sinko1
and Tyler R. Baxter2
St. Cloud State University, St. Cloud, Minnesota, 56301, USA
Abstract: In the past decade, solar sail propulsion has been successfully demonstrated
in space. In this paper, we propose a new type of interstellar propulsion system and
critically examine its physical feasibility in the context of modern photovoltaic and solar sail
technologies. This paper analyzes the viability of a spherical interstellar propulsion concept,
and explores its physical parameters and the limitations against its practical
implementation. The proposed system would use a spherical, thin film photovoltaic
structure, relying on ambient light in the astrophysical environment for power and
ultimately, thrust generation. Integrated diode lasers powered by the photovoltaic structure
would produce a net unidirectional thrust in an adjustable direction with no onboard
propellant. Compared to planar solar sails, there would seem to be inherent promise for
niche applications where the distribution of radiant power sources is roughly isotropic, such
as propulsion between stars or within a luminous nebula. However, our analysis indicates
that the device is impractical as an interstellar propulsion system, primarily due to low
thrust and long transit times that would exceed component lifetimes by orders of magnitude.
Nomenclature
= Wavelength [m]
= Areal density [g/m2
]
= Thrust [N]
A = Area [m2
]
c = Speed of light in the vacuum [m/s]
f = Repetitive pulse frequency [Hz]
E = Energy [J]
Eg = Band gap energy [J]
F = A unitless temperature-dependent function of temperature related to laser diodes
h = Planck’s constant [J s]
I = Total impulse [N s]
kB = Boltzmann’s constant [J/K]
K = A material-dependent constant
MTTF = Mean time to failure [s]
N = Number of photons
p = Momentum [N s]
P = Power [W]
P0 = Optical peak power [W]
Poutput = Stellar power output [W]
r = Radius [m]
1
Assistant Professor, Department of Physics and Astronomy, jesinko@stcloudstate.edu
2
Undergraduate student, Department of Physics and Astronomy, baty1102@stcloudstate.edu
IEPC-2015-144/ISTS-2015-b-144
IEPC-2015-144/ISTS-2015-b-144
2. Joint Conference of 30th ISTS, 34th IEPC and 6th NSAT, Kobe-Hyogo, Japan
July 4 – 10, 2015
2
t = Time [s]
tL = Laser pulse length [s]
T = Temperature [K]
w = Laser emitter width [m]
I. Introduction
F humans are to eventually travel between stars, we must consider non-traditional methods of propulsion. For
interstellar travel, reducing mass and increasing specific impulse are critical steps. One way to reduce propellant
mass is to use massless photons as the propellant. Photon thrust, predicted by Kepler,1
is a well-established concept
in which by absorption or reflection, a number of photons N delivers a total impulse I. When delivered in a time
interval t, this process results in an average thrust . The de Broglie momentum for a photon is:
h
p (1)
for a single photon with wavelength and Planck’s constant (h 6.626 10-34
J s). Absorptive thrust is then:
t
Nh
t
I
, (2)
and considering the energy of a single photon is E = c p, then the thrust obtained under radiative power P is:
c
P
(3)
An increase of roughly a factor of 2 can be obtained by using photon reflection instead of absorption, but given
that c 3 108
m/s, photon thrust will still be small compared to rocket thrust (i.e. exhaust of material with mass),
even for significant optical power. These observations apply to all photon sails.
The concept explored in this paper deviates from typical sails in that it uses photon emission for thrust
generation (instead of reflection or absorption). Ultimately, though, this concept must face the same inherent
challenges. As background for our concept, we will begin the paper with a discussion of a few solar sail missions
and concepts for beamed power photon sails. We will discuss the ‘state of the art’ of thin film photovoltaic power.
Finally, we will analyze a concept for a spherical power array that feeds a laser ‘photon thruster’. We will attempt to
integrate the disparate components and finally consider whether a spherical, laser-driven, photon-momentum-based
propulsion system could be viable for interstellar travel.
II. Context: Traditional Solar Sails
The vehicle concept presented in this paper draws heavily from existing solar sails and solar sail concepts.
Consideration of the existing literature will help inform design and analysis.
A. Solar Sail Missions
International interest in solar sail technology has recently surged. Maturation of manufacturing processes for
thin films and new schemes for sail deployment have contributed to this rise in interest; however, progress in solar
sails has seen its share of setbacks.
In June 2005, Cosmos 1, a solar sail produced by the Planetary Society, was launched on a Volna rocket.2
The
payload had a mass of about 100 kg; its sail, made of aluminized PET, had an area of 600 m2
. Its expected
acceleration was 5 10-5
m/s2
. The anticipated mission lifetime was 30 days, with the intent of executing an orbit-
raising maneuver as a technology demonstration. It failed to reach orbit.
In 2008, NASA also made an effort at launching a solar sail. The NanoSail-D mission would have tested solar
sail propulsion with a 4 kg payload and 10 m2
area, but the satellite was lost shortly after launch due to a
malfunction of the Falcon-1 launch vehicle.3
The subsequent Nanosail-D24
was more or less a duplicate of the
original. Successfully launched from a Minotaur IV rocket in November 2010, Nanosail-D2 had a square, 7.5 m-
thick, 10 m2
sail, intended to demonstrate sail deployment technology. It re-entered Earth’s atmosphere in late 2011.
I
3. Joint Conference of 30th ISTS, 34th IEPC and 6th NSAT, Kobe-Hyogo, Japan
July 4 – 10, 2015
3
In May 2010, JAXA launched IKAROS (Interplanetary Kite-craft Accelerated by Radiation of the Sun), which
successfully demonstrated solar sail propulsion, passing Venus around December 2010.5
The square sail had about
200 m2
area, 300 kg total mass with a 7.5 μm-thick sail composed of aluminum-coated polyimide. It was used in a
hybrid propulsion scheme combining photon propulsion and thin film photovoltaic-driven ion propulsion. About
5% of the sail area was devoted to solar cells which generated about 500 W, used to drive the ion engine.
NASA had been developing a solar sail mission called Sunjammer,6
which had been planned to include a 5 m-
thick sail with 1200 m2
area, and about 9 mN thrust. It was canceled in 2014.
The missions in the last 10 years indicate that at least part of the world aerospace sector is excited about research
in solar sails. However, unless solar sail missions can demonstrate significant advantages compared to conventional
propulsion methods, the technology is unlikely to be enthusiastically adopted for future missions. This situation
motivates our attempt to apply solar sail technology to interstellar propulsion.
B. Beamed Sails
The beamed sail concept was probably first proposed by Forward in 19627
and Marx in 1966.8
Instead of
sunlight, beamed sails incorporate a terrestrial or space-based power source, probably a laser, to propel the sail with
larger thrust than possible with solar radiation alone. Although Marx’s original idea to use a 1-km wide, hard x-ray
laser beam is not currently feasible, visible lasers with 10-100 kW total output power are now commonplace.
Realization of beamed photon sails is challenged by the basic limitations of diffraction; namely, large aperture and
small wavelength are needed.
Beamed sail vehicle concepts are essentially identical to those for solar sails. Such topics have been explored
conceptually, for instance by Landis.9
Experimentally, Myrabo, et al.10
investigated laser-driven carbon fabric
sputtered with molybdenum under vacuum, measuring about 10 dynes thrust from 10 kW incident irradiation by a
CO2 laser. In the process, they raised the sail material to temperatures around 2500 K, with significant ablation of
the sail observed above about 13 kW irradiated power. An upper limit on allowable irradiance may be inferred for
beamed sails and solar sails. An alternative realization of a beamed sail arises in the efforts of Bae11
towards an
intracavity laser-driven ‘photonic thruster’. Yet, the use of a remote laser in beamed energy propulsion for sail
missions is still ‘diffraction limited’. A laser is of doubtful use at interstellar distances due to the rapid falloff of
transferred power over light years. Can the sail itself be used as a practical power source in interstellar space?
III. Solar Sail Power Sources and Power Management
Photon sail vehicle concepts require an external power source. As discussed above, the source could be the Sun,
a laser beam, or some more exotic radiator. Towards considering interstellar photon propulsion, interesting non-
traditional options for power sources are stars and radiant interplanetary gases. We will now consider whether these
sources are sufficient to be utilized for propulsion purposes. Light from point-like sources dissipates according to
the inverse square law; however, an interstellar vehicle surrounded by stars can in principle be considered to rest in
an isotropic radiation environment. Let this vehicle lie at some arbitrary position near, but outside of, our solar
system. Considering the vast distances, how much power can be intercepted from stars in our astrophysical locale?
Table 1 indicates relevant
properties of the nearest 10 stars
including Hertzsprung-Russel
classification, power output,
rough distance from Earth, and
irradiance (computed as Poutput
divided by spherical area at the
indicated distance). The
irradiances from these remote
sources at best are on the order
of 10-7
W/m2
. This situation sets
extreme limits on the power
available to the spacecraft, and
suggest that the design for the
propulsion system be trimmed
back as far as possible, for
example by reducing mass to
maximize acceleration.
Table 1. Properties of the 10 nearest stars.12
Star Type
Poutput
(W)
Distance
(m)
Irradiance
(W/m2
), at Earth
Sol G2V 3.9 1026
1.49 1011
1.4 103
Proxima Centauri M5.0V 6.3 1023
4.01 1016
3.1 10-11
α Centauri A
α Centauri B
G2V
K0V
5.9 1026
2.0 1026
4.16 1016
2.7 10-8
9.2 10-9
Barnard’s Star M4V 1.3 1024
5.67 1016
3.2 10-11
Wolf 359 M5.5V 5.5 1023
7.38 1016
8.0 10-12
Lalande 21185 M2V 1.2 1025
7.85 1016
1.6 10-10
Sirius A
Sirius B
A1V
DA2
9.9 1027
9.9 1024
8.13 1016
1.2 10-7
1.2 10-10
Luyten 726-8 A
Luyten 726-8 B
M5.5V
M6V
3.5 1023
1.5 1022
8.23 1016
4.1 10-12
1.8 10-13
Ross 154 M3.5V 2.5 1024
9.17 1016
2.4 10-11
Ross 248 M5.5V 5.5 1023
9.74 1016
4.6 10-12
4. Joint Conference of 30th ISTS, 34th IEPC and 6th NSAT, Kobe-Hyogo, Japan
July 4 – 10, 2015
4
Table 2 indicates expected irradiances from the sun at
significant distances. In consideration of the results of
Myrabo, et al.,10
it is likely that sails activated within the
orbit of Mercury would suffer unduly from ablation.
Outside of over-irradiance, the sun probably remains the
best fixed single source of radiant power up to about 1
light year from Earth. On the other hand, the fixed stars
are not the only possible sources of radiant power.
Table 3 lists a few other sources, which are (roughly)
isotropically distributed.
In theory, a single-directional, planar sail effectively
intercepts light from 2 steradians at perfect efficiency. In
reality, additional losses will be present, for instance when
not at normal incidence, due to the Lambert cosine factor.
If the sail material is reflective in one direction but
absorbing in the other, it will still generate thrust when
illuminated isotropically, as long as it is not in thermal
equilibrium with its isotropic radiation environment.
Happily, this would not be the case for a sail, since the
thermal environment is roughly at 2.7 K, whereas the
typical photon temperature in the visible spectrum is
roughly ~5000-6000 K.
Thin film photovoltaic devices and semiconductor
materials are under intense scrutiny at present for their
potential use in optics, photonics, and commercial solar power.14
Thin film photovoltaic materials composed of
silicon, copper indium gallium selenide (CIGS) and
cadmium telluride (CdTe) are approaching opto-electrical
efficiencies of 20%. Table 4 provides a few details about
these thin film photovoltaic materials in terms of mass,
cost, and efficiency.
A 10 m2
array of any the materials in Table 4 will
produce on the order of 1 kW electrical power in Earth
orbit. Although other types of thin film photovoltaic
materials and devices are currently under development, the
above may be considered representative of the ‘state of the
art’ for photovoltaic power.
We will now attempt an integration of photovoltaic
materials into our interstellar propulsion concept.
IV. The Proposed Interstellar Vehicle Concept
The concept proposed in this paper is a photovoltaic laser thruster. Rather than operating by absorbing or
reflecting photons, the idea is to operate by absorbing power and then emitting photons in a single direction to
generate momentum. The collector would be realized by wrapping a thin film photovoltaic ‘sail’ on the surface of a
spheroid. The intent would be flexibility to use either directional or isotropic sources of radiation for power.
A. Possible Modes of Operation
For operational parameters, two thrust modes are suggested by this situation. The first mode would be used
when the craft was primarily irradiated from a single direction. This mode resembles that of photon sail propulsion,
in that the craft could generate thrust by photon reflection and/or absorption. However, thrust for attitude control
could be delivered using the onboard laser, powered by the energy of the same photons generating momentum by
absorption, and approaching the 2 factor on thrust achieved by photon reflection in typical sails. This concept is
shown diagrammatically in Fig. 1. It should be clear from the figure that some efficiency factor will be necessary
due to the Lambertian character of irradiation onto the oblate spheroid.
Table 2. Irradiances at Distances from Sol.12
Location Solar ‘altitude’ Irradiance
[m] [W/m2
]
Solar surface 0 6.4 106
Mercury 5.8 1010
9.3 103
Venus 1.1 1011
2.7 103
Earth 1.5 1011
1.4 103
Mars 2.3 1011
6.0 102
Jupiter 7.8 1011
5.1 101
Saturn 1.4 1012
1.5 101
Uranus 2.9 1012
3.7 100
Neptune 4.5 1012
1.5 100
1 light year 9.5 1015
3.4 10-7
Table 3. Astrophysical Radiation Sources13
Isotropic Source
Irradiance
(W/m2
)
Zodiacal light 1.2 10-7
Integrated starlight 3.0 10-8
Diffuse galactic light 9.1 10-9
Cosmic light 9.1 10-10
Table 4. Photovoltaic Thin Film Properties.15-17
Areal density
(g/m2
)
Areal cost
($US/m2
)
Efficiency
(%)
Si 5 ~200 10-12
CdTe 5-6
~50 9Cd 5-6
Te 0.04
CIGS 6
~6 10-20
Cu 2.53
In 3.16
Ga 0.76
5. Joint Conference of 30th ISTS, 34th IEPC and 6th NSAT, Kobe-Hyogo, Japan
July 4 – 10, 2015
5
The second mode would be used when the craft was
far from any single power source, so that diffuse power
sources dominated. Isotropically-intercepted incident
photons would generate insignificant net thrust by
momentum transfer due to net cancellation. However,
power harvested from these photons would be routed to
the lasers to generate directional thrust, as imagined in Fig. 2. In either usage, there would be power loss due to the
electrical-optical efficiency of the laser. It might also be necessary in the case of low power, to cycle the lasers
using an onboard power storage system.
B. Laser Emitters for Thrust
In considering this propulsion concept, the thrust mechanism is important. Possible options for photon emitters
include laser diodes and diode-pumped solid state (DPSS) lasers, both of which have made steady inroads into
worldwide commercial markets due to small size, low cost, high power output, and high electrical-optical efficiency.
Laser diodes may be the best option for a system,
due to their simplicity of use, high efficiency, and long
lifetimes. Several common kinds of laser diodes and
corresponding wavelengths and wall plug efficiencies
(optical output/electrical input) are tabulated in Table 5.
Compared to laser diodes, DPSS systems have
better output coherence, but suffer additional losses to
efficiency. A few possible candidate processes based
on AlGaAs pump diodes, with corresponding output
wavelengths and efficiencies, are tabulated in Table 6.
As discussed by Davarcioglu,22
the lifetime of a
laser diode is typically limited to 10,000-
30,000 hours of operation. The failure likelihood is
described by a ‘bathtub curve’ – initially high
failure rates (‘infant failures’) give way
exponentially to an essentially flat, low probability
of random failures, until device end of life
approaches, when the failure rate increases more or
less exponentially again as the device ages.23
The useful life of the device is thus in the flat part of the ‘bathtub’.
Migration of aluminum ions within AlGaAs diodes can eventually culminate in device failure. It may therefore be
wise, in going forward, to choose an alternative diode laser source, such as a system based on gallium nitride. Diode
laser lifetime is sometimes estimated in the industry based on mean time to failure (MTTF):24
26
0
6
)(
LtPf
TFwK
MTTF . (4)
Table 6. Parameters of a few common DPSS lasers.22
Process (nm) Ideal efficiency
AlGaAs NdYVO4 594 1%
AlGaAs NdYVO4 KTP 532 48%
AlGaAs NdYVO4 BBO 473 5%
AlGaAs BBO 404 12%
Table 5. Common laser diode parameters.18-21
Laser diode type (nm) Wallplug efficiency
InGaN 405 ~25%
GaN 450 ~12%
GaAs 650 ~30%
AlGaAs/GaAs 808 ~50-60%
GaAs 940-980 ~70%
InP 1530 ~50%
Figure 1. Directional power configuration.
Figure 2. Isotropic power configuration.
6. Joint Conference of 30th ISTS, 34th IEPC and 6th NSAT, Kobe-Hyogo, Japan
July 4 – 10, 2015
6
Here, K is a material-dependent constant (e.g., 7 1019
), w is the width of the laser emitter, F(T) is a function of
temperature (F(T)=1 at 25 C), f is the repetitive pulse frequency, P0 is optical peak power, and tL is the laser pulse
length. The empirical relationship
TkE Bg
eTF
/
)( has been observed,25
so operation at high temperature will tend
to reduce MTTF. Leuzinger23
notes that lifetimes can be extended up to millions of hours (on the order of 50 years),
for instance using single emitters that operate at multi-Watt output. Considering the latter diodes are designed for
reliable industrial use, a similar technology might be appropriate for our application. Our proposal is for a long-
range device that could traverse interstellar distances. Component lifetimes are crucial because an arbitrarily long
trip time assures eventual component failures. An interesting question is whether it would be wiser to optimize for a
single long-life emitter, or to include multiple, low-mass emitters that are replaced as the trip progresses.
An important factor significantly influencing the device lifetime, which we have so far neglected, is radiation
from the ambient environment. This topic was explored in detail by Phifer,26
and more recently by Galofaro.27
Radiation effects on semiconductor devices are often deleterious for a number of reasons, but in some cases can
actually result in improvements in performance. Such effects would need to be studied in detail for an interstellar
mission, since radiative degradation of either the photovoltaic cells or the laser diodes could preclude long-term
functionality of the system. In concluding this discussion, it is worth noting that the output power of the laser device
would necessarily vary along the vehicle trajectory as incident power fluctuated.
C. Scaling for a Practical Spherical Photon Thruster
Now that the state of the art in thin film photovoltaic technology has been introduced, let us generally apply the
benchmark values so far to our spherical photon thruster concept for analysis. Based on the previously stated values
for thin film materials, assume an areal density 5 g/m2
, photovoltaic efficiency of 10%, solar irradiance (around
Earth orbit) of 1.4 kW/m2
, and laser electrical-optical efficiency of 40%. Based on solar sail technology, our
consideration of the maximum practical radius for the device will be held to 1 km. Table 7 is intended to provide a
context of expected intercepted power and thrust for
various sized conventional solar sails. Table 7 reinforces
the idea that photon thrust from a traditional solar sail is
reasonable (if still small) when operated close to a power
source; i.e., a star.
Turning back to our proposed spherical photon
propulsion device, we wish to consider a limit of operation
far from any single powerful radiation source, e.g.,
interstellar space. Considering the factor of 1/c that
reduces intercepted power to thrust, one might assume that
the surface area needs to be as large as possible to increase thrust to a reasonable level. However, Newton’s second
law indicates that scaling up the area will not result in improvement in acceleration because mass and intercepted
power (and therefore emitted power, and thrust) also scale directly with area. Increases in acceleration can thus only
be achieved by reducing the thin film photovoltaic thickness or by improving efficiencies.
Table 8 summarizes, in analogy to
Table 7, the thrust scaling for a spherical
photon thruster. Note that even for a
hypothetical radius of nearly 200 km, the
intercepted power does not provide
significant thrust. Although deficiency in
intercepted power can – to an extent – be
offset by reduction of mass, the deficit will
likely remain too great for practical use of
this system. This trouble is exacerbated
because the expected lifetimes of the
component devices (e.g., 10-50 years) that
compose the system are much shorter than
the trip time, imposed by low acceleration. Can reduction of the system thickness make this propulsion system
feasible? Commercial thin film photovoltaics weigh around 1-10 g/m2
, and although new materials may drive down
the lower limit of this range, it is likely to be at a cost in photovoltaic efficiency. Table 9 helps evaluate the
situation, assuming a spherical surface area of 1.3 107
m2
corresponding to a thrust of 2.8 10-10
N, as noted in Table
8. At the smallest considered areal density (1.0 10-3
g/m2
) assuming the material has volume density around
Table 7. Scaling for a Planar Solar Sail.
Radius
(m)
Mass
(kg)
P, Earth ( R2
)
(kW)
Thrust
(N)
0.9 0.05 0.32 4.7 10-7
2.8 0.5 3.2 4.7 10-6
8.9 5 32 4.7 10-5
28.2 50 320 4.7 10-4
1000 62,800 4.1 106
5.9 10-1
Table 8. Area Scaling for Spherical Propulsion System.
Radius
(m)
Area (4 r2
)
(m2
)
Mass
(kg)
Power emitted
(W)
Thrust
(N)
9.0 10-1
1.0 101
5.0 10-2
6.4 10-8
2.1 10-16
2.8 100
9.9 101
5.0 10-1
6.3 10-7
2.1 10-15
8.9 100
1.0 103
5.0 100
6.4 10-6
2.1 10-14
2.8 101
9.9 103
5.0 101
6.3 10-5
2.1 10-13
1.0 103
1.3 107
6.5 104
8.3 10-2
2.8 10-10
1.9 103
4.5 107
2.3 105
2.9 10-1
9.7 10-10
6.1 104
4.7 1010
2.4 108
3.0 102
1.0 10-6
1.9 105
4.5 1011
2.3 109
2.9 103
9.7 10-6
7. Joint Conference of 30th ISTS, 34th IEPC and 6th NSAT, Kobe-Hyogo, Japan
July 4 – 10, 2015
7
5 g/cm3
, the thickness would be only 2.0 10-10
m. Considering the matching acceleration in Table 9, even with a
single-atom-thickness, the proposed system
will still not produce sufficient thrust to
make the device practical as an interstellar
propulsion method.
Our main conclusion from this study is
that the spherical photon propulsion concept
is not appropriate for interstellar propulsion.
However, the possibility is left open that the
system might find use in a different
isotropic environment, for instance within a
cloud of luminous gas. Further, incorporating a moveable diode laser into a traditional planar solar sail could be a
valuable method to produce thrust redirection without changing the orientation of the entire sail.
V. Conclusion
In this paper, we examined an interstellar propulsion concept that uses a thin film photovoltaic array to power a
laser and produce thrust based on photon momentum. The system would draw power in an isotropic radiation
environment to produce propellant-less, directional thrust. Although the concept seems interesting, insurmountable
challenges prevent its realization. Existing solar sails are capable of acceleration on the order of 1 10-6
m/s2
in the
solar environment. Our analysis indicates that in interstellar space, optimistically, an interstellar spherical
propulsion system like the one described in this paper would have a maximum acceleration about 6 orders of
magnitude less than traditional solar sails. This limitation effectively precludes its intended use as an interstellar
propulsion system, since the trip times, even to nearby stars, are unreasonably long – and, since the component
devices would only function for a small fraction of the trip. However, our research suggests that implementation of
diode lasers with conventional sails is not out of the question, and may enable better sail control via steering with
photons emitted from a diode laser.
Acknowledgments
The authors thank St. Cloud State University and the St. Cloud State University Department of Physics and
Astronomy for support. Highly useful assistance was also provided by Prof. Todd Vaccaro of the St. Cloud State
University Department of Physics and Astronomy.
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2.2 10-15
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1.0 100
1.3 104
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1.0 10-1
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1.0 10-2
1.3 102
2.2 10-12
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1.4 103
8. Joint Conference of 30th ISTS, 34th IEPC and 6th NSAT, Kobe-Hyogo, Japan
July 4 – 10, 2015
8
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