https://www.centauri-dreams.org/2024/09/18/beamed-propulsion-and-planetary-security/ Centauri Dreams * Home * About * Administrative * Booklist * Contact Select Page [ ] Beamed Propulsion and Planetary Security by Paul Gilster | Sep 18, 2024 | Sail Concepts | 4 comments Power beaming to accelerate a 'lightsail' has been pondered since the days when Robert Forward became intrigued with nascent laser technologies. The Breakthrough Starshot concept has been to use a laser array to drive a fleet of tiny payloads to a nearby star, most likely Proxima Centauri. It's significant that a crucial early decision was to place the laser array that would drive such craft on the Earth's surface rather than in space. You would think that a space-based installation would have powerful advantages, but two immediate issues drove the choice, the first being political. The politics of laser beaming can be complicated. I'm reminded of the obligations involved in what is known as the Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, including the Moon and Other Celestial Bodies (let's just call it the Outer Space Treaty), spurred by a paper from Adam Hibberd that has just popped up on arXiv. The treaty, which comes out of the United Nations Office for Space Affairs, emerged decades ago and has 115 signatories globally. Here's the bit relevant for today's discussion, as quoted by Hibberd (Institute for Interstellar Studies, London): States Parties to the Treaty undertake not to place in orbit around the earth any objects carrying nuclear weapons or any other kinds of weapons of mass destruction, install such weapons on celestial bodies, or station such weapons in outer space in any other manner. The moon and other celestial bodies shall be used by all States Parties to the Treaty exclusively for peaceful purposes. The establishment of military bases, installations and fortifications, the testing of any type of weapons and the conduct of military manoeuvres on celestial bodies shall be forbidden. The use of military personnel for scientific research or for any other peaceful purposes shall not be prohibited. The use of any equipment or facility necessary for peaceful exploration of the moon and other celestial bodies shall also not be prohibited. So we're ruling out weaponry in orbit or elsewhere in space. Would that prohibit building an enormous laser array designed for space exploration? Hibberd believes a space laser would be permitted if its intention were for space exploration or planetary defense, but you can see the problem: Power beaming at this magnitude can clearly be converted into a weapon in the wrong hands. And what a weapon. A 10 km X 10 km installation as considered in Philip Lubin's DE-STAR 4 concept generates 70 GW beams. You can do a lot with that beyond pushing a craft to deep space or taking an Earth-threatening asteroid apart. Build the array on Earth and the political entanglements do not vanish but perhaps become manageable as attention shifts to how to avoid accidentally hitting commercial airliners and the like, including the effects on wildlife and the environment. [beam] Image: Pushing a lightsail with beamed energy is a feasible concept capable of being scaled for a wide variety of missions. But where do we put the beamer? Credit: Philip Lubin / UC-Santa Barbara. The second factor in the early Starshot discussions was time. Although now slowed down as its team looks at near-term applications for the technologies thus far examined, Starshot was initially ramping up for a deployment by mid-century. That's pretty ambitious, and we wouldn't have a space option that could develop the beamer if that stretchiest-of-all-stretch goals actually became a prerequisite. So if we ease the schedule and assume we have the rest of the century or more to play with, we can again examine laser facilities off-planet. Moreover, Starshot is just one beamer concept, and we can back away from its specifics to consider an overall laser infrastructure. Hibberd's choice is the DE-STAR framework (Directed Energy Systems for Targeting of Asteroids and Exploration) developed by Philip Lubin at UC-Santa Barbara and first described in a 2012 on planetary defense. The concept has appeared in numerous papers since, especially 2016's "A Roadmap to Interstellar Flight." If the development of these ideas intrigues you, let me recommend Jim Benford's A Photon Beam Propulsion Timeline, published here in 2016, as well as Philip Lubin's DE-STAR and Breakthrough Starshot: A Short History, also from these pages. What Hibberd is about in his new paper is to work out how far away various categories of laser systems would have to be to ensure the safety of our planet. This leads to a sequence of calculations defining different safe distances depending on the size of the installation. The DE-STAR concept is modular, a square phased array of lasers where each upgrade indicates a power of base 10 expansion to the array in meters. In other words, while DE-STAR 0 is 1 meter to the side, DE-STAR 1 goes to 10 meters to the side, and so on. Here's the chart Hibberd presents for the system (Table 1 in his paper). [Screenshot-from-2024-09-18-04-56-53] Keep scaling up and you achieve arrays of stupendous size, and in fact an early news release from UC-Santa Barbara described a DE-STAR 6 as a propulsion system for a 10-ton interstellar craft. It's hard to imagine the 1,000 kilometer array this would involve, although I'm sure Robert Forward would have enjoyed the idea. So taking Lubin's DE-STAR as the conceptual model (and sticking with the more achievable lower end of the DE-STAR scale), how can we lower the risks of this kind of array being used as a weapon? And that translates into: Where can we put an array so that even its largest iterations are too far from Earth to cause concern? Hibberd's calculations involve determining the minimum level of flux generated by an individual 1 meter aperture laser element (this is DE-STAR 0) - "the unphased flux of any DE-STAR n laser system" - and using as the theoretical minimum safe distance from Earth a value on the order of 10 percent of the solar constant at Earth, meaning the average electromagnetic radiation per unit area received at the surface. The solar constant value is 1361 watts per square meter (W/ m2); Hibberd pares it down to a maximum allowed flux of 100 W/m2 and proceeds accordingly. Now the problems of a space-based installation become strikingly apparent, for the calculations show that DE-STAR 1 (10 m X 10 m) would need to be positioned outside cis-lunar space to ensure these standards, and even further away (beyond the Earth-Moon Lagrange 2 point) for ultraviolet wavelengths (l [?] 350nm). That takes us out 450,000 kilometers from Earth. However, a position at the Sun-Earth L2 Lagrange location would be safe for a DE-STAR 1 array. The numbers add up, and we have to take account of stability. The Sun /Earth Lagrange 4 and 5 points would allow a DE-STAR 2 laser installation to remain at a fixed location without on-board propulsion. DE-STAR 3 would have to be positioned beyond the asteroid belt, or even beyond Jupiter if we take ultraviolet wavelengths into account. The enormous DE-STAR 4 level array would need to be placed as far as 70 AU away. All this assumes we are working with an array on direct line of sight with the Earth, but this does not have to be the case. Let me quote Hibberd on this, as it's rather interesting: Two such locations are the Earth/Moon Lagrange 2 point (on a line from the Earth to the Moon, extending beyond the Moon by ~ 61, 000 km) and the Sun/Earth Lagrange 3 point (at 1 au from the Sun and diametrically opposite the Earth as it orbits the Sun). In both cases, the instability of these points will result in the DE-STAR wandering away and potentially becoming visible from Earth, so an on-board propulsion would be needed to prevent this. One solution would be to use the push-back from the lasers to provide a means of corrective propulsion. However it would appear a DE-STAR's placement at either of these points is not an entirely satisfactory solution to the problem. So we can operate with on-board propulsion to achieve no direct line-of-sight to Earth, but the orbital instabilities involved make this problematic. Achieving the goal of a maximum safe flux at Earth isn't easy, and we're forced to place even DE-STAR 2 arrays at least 1 AU from the Sun at the Sun/Earth Lagrange 4 or 5 positions to achieve stable orbits. DE-STAR 3 demands movement beyond the asteroid belt at a minimum. DE-STAR levels beyond this will require new strategies for safety. Back to the original surmise. Even if we had the technology to build a DE-STAR array in space in the near future, safety constraints dictate that it be placed at large distances from the Earth, making it necessary to have first developed an infrastructure within the Solar System that could support a project like this. As opposed to one-off missions from Earth launching before such an infrastructure is in place, we'll need to have the ability to move freely at distances that ensure safety, unless other means of planetary protection can be ensured. Hibberd doesn't speculate as to what these might be, but somewhere down the line we're going to need solutions for this conundrum. The paper is Hibberd, "Minimum Safe Distances for DE-STAR Space Lasers," available as a preprint. Philip Lubin's "A Roadmap to Interstellar Flight" appeared in Journal of the British Interplanetary Society 69, 40-72 (2016). Full text. [tzf_img_post] 4 Comments 1. Alex Tolley on September 18, 2024 at 10:22 I would have thought the obvious placement solution is on the lunar farside. It satisfies the requirement to prevent the lasers from being in the "line of sight" of Earth, but still effectively in space, Barring issues of directionality with targets that may be close to the lunar horizon, almost all targets can be safely reached during a lunar month. If manufacturing much of the mass of the laser array can be done locally, that would be operational and cost-effective compared to an array placed at L2, and the moon would be a stable platform obviating the need for propellant for station-keeping, let alone the mass of the support structure for an array in space that would be nigh impossible to stop from flexing and interfering with the phasing of the laser beams. The main downside of placing an array on farside is that if there are a large number of lunar satellites, not to mention transport that requires orbital space over farside, the use of the arrays will have to allow for these to pass. [Any optical SETI on stars looking at our system might see not only a strong, narrow, monochromatic "signal", but possibly pulsed irregularly as it is turned off to prevent damage to satellites and spacecraft passing overhead on farside. How would an ETI version of "The Mote in God's Eye" or "Tower of Glass" be written with that as an inspiration?] Reply 2. Brenda Kalt on September 18, 2024 at 11:42 What about the far side of the Moon? Reply 3. Derek Miller on September 18, 2024 at 12:36 How about the "dark" side of the moon? Always pointing away from Earth! Radius is 1737km, which is a DE-STAR 6+ class. There should be plenty of material to build the thing there, but solar power and tracking may be a problem. Reply 4. William R Alschuler on September 18, 2024 at 14:16 This is a very interesting dilemma. Several thoughts occur: first, position maintenance for Lagrange point 3 could be provided by either solar sails attached to the laser arrays for corrections, which would be passive, or solar PV to electric propulsion motors (active). The latter might also be the power source to drive the laser arrays. Second, how about putting the laser arrays on the far side of the moon. This would allow any size array while blocking any direct-to-Earth beam unless a relay mirror system was added and this could be defended against. This location would face the same beam-steering challenges of the other locations, but at different time scales, at least in part. It would be close enough to allow quick visits to meet maintenance issues as they came up. Lunar dust might be a problem, however. If placed on Earth, perhaps the laser arrays could be either set in an annulus of large dimension or scattered almost at random over a large area. This would disperse the energy input to the atmosphere, perhaps lowering influence on turbulence and weather, but perhaps increasing the complexity of aircraft exposure avoidance. The beams would aim at a beam combiner at one of the considered distances mentioned in the post, chosen as appropriate for the power of the array. Techniques have been developed for maintaining beam integrity in the face of atmospheric turbulence both for laser weapons and for astronomical observations. Reply Submit a Comment Cancel reply Your email address will not be published. Required fields are marked * [ ] [ ] [ ] [ ] [ ] [ ] [ ] Comment * [ ] Name * [ ] Email * [ ] Website [ ] [ ] Save my name, email, and website in this browser for the next time I comment. [Submit Comment] [ ] [ ] [ ] [ ] [ ] [ ] [ ] D[ ] Search [ ]Search Charter In Centauri Dreams, Paul Gilster looks at peer-reviewed research on deep space exploration, with an eye toward interstellar possibilities. For many years this site coordinated its efforts with the Tau Zero Foundation. It now serves as an independent forum for deep space news and ideas. In the logo above, the leftmost star is Alpha Centauri, a triple system closer than any other star, and a primary target for early interstellar probes. To its right is Beta Centauri (not a part of the Alpha Centauri system), with Beta, Gamma, Delta and Epsilon Crucis, stars in the Southern Cross, visible at the far right (image courtesy of Marco Lorenzi). Now Reading [kaltenegger] Recent Posts * Beamed Propulsion and Planetary Security * All the Light We Can See * Green Mars: A Nanotech Beginning * The 'Freakish Radio Writings' of 1924 * Pumping Energy into the Solar Wind * Our Earliest Ancestor Appeared Soon After Earth Formed * Are Interstellar Quantum Communications Possible? * The Odds on an Empty Cosmos On Comments If you'd like to submit a comment for possible publication on Centauri Dreams, I will be glad to consider it. The primary criterion is that comments contribute meaningfully to the debate. Among other criteria for selection: Comments must be on topic, directly related to the post in question, must use appropriate language, and must not be abusive to others. Civility counts. In addition, a valid email address is required for a comment to be considered. Centauri Dreams is emphatically not a soapbox for political or religious views submitted by individuals or organizations. A long form of the policy can be viewed on the Administrative page. The short form is this: If your comment is not on topic and respectful to others, I'm probably not going to run it. Follow with RSS or E-Mail RSS Follow by Email Follow by E-Mail Get new posts by email: [ ] [Subscribe] Advanced Propulsion Research Beginning and End Exoplanet Projects (Earth) * AFOE * Amateur Exoplanet Archive * Anglo-Australian Planet Search * APACHE Project * ASTEP: Antarctic Search for Transiting Extrasolar Planets * ASTRA * Astro Gregas * Atacama Large Millimetre Array * Automated Planet Finder * Berlin Exoplanet Search Telescope * California & Carnegie Planet Search * Carl Sagan Institute (Cornell) * CARMENES * Carnegie Astrometric Planet Search * CBA Belgium Observatory * CHIRON * CLEVER Planets * CODEX * Colossus * Coralie * DayNight * DEMONEX (DEdicated MONitor of EXotransits) * Dispersed Matter Planet Project * East Asian Planet Search Network * Elodie * ESO Coude Echelle Spectrometer * ESPRESSO (Echelle SPectrograph for Rocky Exoplanet and Stable Spectroscopic Observations) * European Extremely Large Telescope * Evryscope * Exoplanet Tracker * Externally Dispersed Interferometry * Fabra-ROA * GAPS (Global Architecture of Planetary Systems) * Gemini Planet Imager * GEMSS: Global Exoplanet M-dwarf Search-Survey * Geneva Extrasolar Planet Search * Habitable Zone Planet Finder * HARPS North * HARPS-N * HATNet Exoplanet Survey * High Accuracy Radial velocity Planetary Search * Hobby-Eberly Telescope * Italian Search for Extraterrestrial Life * ITASEL * Keck Interferometer * Keck Planet Finder * KELT North * KELT South * KMTNet (Korea Microlensing Telescope Network) * KOBE: K-dwarfs Orbited By habitable Exoplanets * Large Binocular Telescope * Las Cumbres Global Telescope Network * Low Frequency Array * LYOT Project * MACHO * Magdalena Ridge Optical Interferometer * Magellan Telescope * MARVELS * MARVELS (Multi-object APO Radial Velocity Exoplanet Large-area Survey) * MASCARA * Maunakea Spectroscopic Explorer * McDonald Observatory * MEarth * METIS (Mid-Infrared E-ELT Imager and Spectrograph) * MicroFUN Microlensing Follow-Up Network * Microlensing Planet Search Project * MINERVA (MINiature Exoplanet Radial Velocity Array) * MOA * MONET * N2K * Nancay Decametric Search * NEAR * NEID Spectrograph * New Mexico Exoplanet Spectroscopic Survey Instrument * NGTS (Next-Generation Transit Survey) * NIRPS (Near Infrared Planet Searcher) * Okayama Planet Search Program * Optical Gravitational Lensing Experiment * OWL * PARAS (PRL Advanced Radial-velocity Allsky Search) * Permanent All Sky Survey * PHASES * PIRATE (Physics Innovations Robotic Astronomical Telescope Explorer) * PISCES (Planets in Stellar Clusters Extensive Search) * PLANET * PLANETS * Precision Radial Velocity Spectrometer * PRIMA-DDL * Project 1640 * Pulsar Planet Detection * QES (Qatar Exoplanet Survey) * Radio Interferometric Planet Search * RoboNet (Microlensing) * SAINT-EX * Search for Trojan Extrasolar Planets * SEEDS (Subaru Strategic Exploration of Exoplanets and Disks) * SHINE * Solaris * Sophie * Spectrashift * SPECULOOS * SPHERE * SPOTS: (Search for Planets Orbiting Two Stars * Square Kilometer Array * STARE * STELLA * SuperWASP * Systemic * Tennessee Automatic Photoelectric Telescope * TEP * Thirty Meter Telescope * TransitSearch * Transitsearch * TRAPPIST (TRAnsiting Planets and PlanetesImals Small Telescope) * TrES: The Transatlantic Exoplanet Survey * TRESCA Project * United Kingdom Infrared Telescope * University of St. Andrews Planet Search * UNSWEPS Project * UVES * Very Large Telescope Interferometer * VIDA * WASP (Wide Angle Search for Planets) * WHAT * XO Project Exoplanet Projects (Space) * ACEsat * Aragoscope * ARIEL: (Atmospheric Remote-Sensing Infrared Exoplanet Large-survey) * ASTERIA * Astro-1 * ATLAST (Advanced Technology Large-Aperture Space Telescope) * CHEOPS - CHaracterising ExOPlanet Satellite * CoRoT * CubeSat * Darwin * Dual Use Exoplanet Telescope * ECHO (Exoplanet Characterization Observatory) * Eddington * EPOXI (Extrasolar Planet Observation and Deep Impact Extended Investigation) * Euclid * EXCEDE * ExoplanetSat CubeSat * FINESSE * Gaia * GEST * HabEx * HEK (Hunt for Exomoons with Kepler) * High Etendue Multiple Object Spectrographic Telescope (THE MOST) * High-Definition Space Telescope * HST Astrometry * James Webb Space Telescope * Kepler * Kilometer Space Telescope * Laser Interferometer Space Antenna * LISE Hypertelescope * LUVOIR * MOST (Microvariability and Oscillations of STars) * Nancy Grace Roman Space Telescope * NEAT * New Worlds Imager * Origins Billion Star Survey * Origins Space Telescope * Pegase * Planet Imaging Concept Testbed * Plato * PlaVi (PlanetVision) * Project Blue * SISTINE * Space Interferometry Mission * SPICES (Spectro-Polarimetric Imaging and Characterization of Exo-planetary Systems) * Spitzer Space Telescope * SUPER-SHARP * SWEEPS * Terrestrial Planet Finder * TESS (Transiting Exoplanet Survey Satellite) * TOLIMAN * Twinkle * UMBRAS Further Astronomical and Astronautical Resources * 100 Year Starship * Acta Astronautica * ADS Abstract Service * Alternative Earths Astrobiology Center * American Astronomical Society * American Geophysical Union * American Institute of Aeronautics and Astronautics * astro-ph preprint server * AstroArt of David A. Hardy * AstroBetter * Astrobiology Magazine * Astrobites * Astrometry.net * Astronautics Now * Astronomical Journal * Astronomy & Astrophysics * Astronomy Picture of the Day * Astrophysical Journal * Beyond NERVA * British Interplanetary Society * Bulletin of the American Astronomical Society * Cosmic Ancestry * Division for Planetary Sciences * European Federation of Biophysics * Event Horizon Telescope * Exoplanet Transit Database * Exploring the Universe with Andrew Fraknoi * Extrasolar Planets and Astrobiology * Extrasolar Planets Encyclopedia * Galaxy Forum * Galileo Project * Google Scholar * Icarus Interstellar * Institute for Interstellar Studies * Interstellar Journey * Interstellar Research Centre * Interstellar Studies Bibliography * James Benford * L'Institut de l'Information Scientifique et Technique * Lunar and Planetary Institute * Meteoritics and Planetary Science * NASA Technical Reports Server * Nature * Orbital Index * Orbital Index * Overview Institute * Physics * Planetary and Life Science Community Meetings Calendar * Planetary and Space Science * Principium (Journal of I4IS) * ResearchGATE * RocketSTEM * Science * Scitizen * SDSS SkyServer * SETI News * SFSU Exoplanet Group * SIMBAD Astronomical Database * Space Agenda * Space Sailing * Space Telescope Science Institute * Space Transport and Engineering Methods * spaceweather.com * The neighborhood * Trans-Neptunian Automated Occultation Survey * Troy Project Weblogs, Discussions, Commentaries * Adam Crowl (Crowlspace) * Airminded * Alien Life * Ancient Solar System * Antimatter * Apparent Brightness * AstroBlog * AstroEngine.com * Astrogator's Logs (Athena Andreadis) * Astronautical Evolution * Astronomist * Astronomy Blog * Astronomy.com Blog * astroPT * Astroquizzical * Asymptotia * Atlas of the Universe * B612 Foundation * Bad Astronomy * Beyond Earthly Skies * Beyond Impossible * Billion Year Plan * Buran Space Shuttle * Captain Interstellar (Paul Titze) * Celestial Matters * Cheap Astronomy * Cocktail Party Physics * collectSPACE * Colony Worlds * Comets & Asteroids: Small Bodies of the Solar System * Cosmic Diary * Cosmic Mirror * Cosmic Tusk * Cosmic Variance * Cosmic Visions * CosmoCoffee * Cumbrian Sky * Dad2059 * Deep Sky Blog * Dialogos of Eide * Dick's Rocket Dungeon * Dragon's Gaze * Dream of the Open Channel * Dreams of Space - Books and Ephemera * Dreams of Space: Books and Ephemera * Drew Ex Machina (Andrew LePage) * DSFP's Spaceflight History Blog * Dynamics of Cats * Eternos Aprendizes * Eureka * Eureka (Daniel Marin) * Ex Space * ExoClimes.com * Exoplanetology * Exoplanets Channel * Extrasolar Visions II * Final Frontier * Finding Pluto * Flank Speed * Fly Me to the Moon * Fraknoi's Universe * Future & Cosmos * Future Incredible * Future Planetary Exploration * Futurismic * Galactic Journey * Gregory Benford * Habitable Worlds * Habitable Zone * Hop's Blog * Il Tredicesimo Cavaliere * In the Dark (Peter Coles) * Innovation Watch * Innumerable Worlds * Invitation to ETI * Isaac Arthur (videos) * James Essig * James Randi Educational Foundation Forum * Jatan's Space * John Cleary Creations * Jon Lomberg * Kentucky Space * Know the Cosmos * Last Word on Nothing * Laurel's Pluto Blog * Leonard David's Inside Outer Space * Letters to Nature * Lifeboat Foundation * Lone Mind * Long Bets Foundation * Long Now Foundation * Lost in Transits * Magellan AO * Many Worlds (Marc Kaufman) * Martian Chronicles * Meridiani Journal * Music of the Spheres * Nano Age * NASA Watch * NASA-UC Eta-Earth Survey * New Papyrus * Next Big Future * NGTS (Next-Generation Transit Survey) * On the Path to Space * One-Minute Astronomer * OrbitalHub * Orion's Arm * Our Universe in 202 Notations * Out of the Cradle * Overcoming Bias (Robin Hanson) * Patrick McCray * peregrinus interstellar * PHASES (Palomar High-precision Astrometric Search for Exoplanet Systems) * Physics arXiv Blog * PI Club * Planet/Planet * PLANETPLANET (Sean Raymond) * Polymath (Robert Clark) * Posthuman Blues * Potentia Tenebras Repellendi * Profiles of Our Future in Space * Project Icarus Weblog * Project Rho (Winchell Chung) * Quasar9 * Real Science * Remote Central * Rick Costello Space Art * Riding with Robots * Robot Explorers * Robot Guy * Rymden i Dag * Science Meets Fiction * Science News * SciTech Journal * Scitizen * Simostronomy * Singularity Institute * Slacker Astronomy * SolStation * Sorting Out Science * Space Archaeology * Space Elevator Blog * Space FTW * Space Law Probe * Space Pragmatism * Space Review * Space Transport News * Space Travel Blog UT Tartu Observatory * Spaceflight History * Spacewriter's Ramblings * Stan Erickson's Alien Civilization Blog * Star Bright? * Star Stryder * Starts with a Bang * Strange Paths * Sufficiently Advanced * Supernova Condensate * This Is Rocket Science * This Week's Finds in Mathematical Physics * Tiny Mantras * Titan Exploration * Tom Barclay/Planet Hunter * Tomorrow Is Here * Trevor Paglen * Ultratech Memes * Universe Today * Unmanned Spaceflight * Velcro City Tourist Board * Visions 2200 * Visual Astronomy * Visualizing Science * Wanderingspace * Watered Down Physics * Where's The Flux (Tabby's Star) * Will Gater * Woodward Effect * Worlds of David Darling * Wow! Signal Podcast * Written Worlds Archives * 2024 (66) * 2023 (102) * 2022 (104) * 2021 (181) * 2020 (188) * 2019 (191) * 2018 (225) * 2017 (235) * 2016 (237) * 2015 (247) * 2014 (242) * 2013 (232) * 2012 (251) * 2011 (244) * 2010 (268) * 2009 (275) * 2008 (314) * 2007 (382) * 2006 (327) * 2005 (330) * 2004 (131) Copyright (c) 2023 Centauri Dreams. All Rights Reserved.