| Some More Food for Thought About Pods A fully loaded 747 amasses about 400 tons. A starship pod could amass 1000 tons and carry 400 hibernating passengers. The passengers, cabin and stassis chambers won't be the most massive part of the pod. The fusion drive, mag-sail and shields will be. At 1.5G, not to uncomfortable for sleepers on thick padding nor damaging to bones or organs, a pod can accelerate/decelerate to 0.5c in 120 days. Since KE= 0.5 mv2 ignoring relativity, 1.125E22 j is needed to accel/decl to/from 0.5c. Over the course of 120 days we must generate 1E15 watts. If the total efficiency of the system from solar panels to mass beam projector (which fires in opposing directions limiting eff. to 50% max.) to sail slippage and losses due to beam spread is 10%, then we must intercept 1E16 watts of stellar energy. At Mercury's distance from the Sun insolation is about 9000 watts/square meter. We need 1.11E12 square meters of collector area. That's one big round collector with a radius of 595 kilometers or twenty smaller collectors each with a radius of 133 km. Neither of these would be beyond megascale engineers of the future, but it is easier to make bricks than ten ton blocks and more numerous smaller collectors plus beam projectors means more reliability. If one device fails or is smashed by a meteor or even damaged by a solar flare there will be nineteen others that can increase power a bit to propell the pod. Beam Projectors The energy collector/mass beam projectors will be located in inclinded orbits around the Sun in planes paralell and perpendicular to the trjectory of the pods so that they are never ecllipsed by the Sun when firing their beams. Thousands could orbit the Sun to handle pod traffic from passing star ships. Passing star ships will be deflected by beams from stations like these to put them on course for the next star in their "string of pearls" routes through the galaxy. To deflect the ships we will need let us say 6% to 50% as much energy as required to accelerate them up to 0.5c. Using an average of about 30% as much energy as required to reach 0.5c, and a ship mass of 500,000 tons (about twice the mass of a supertanker but much larger because it's made of low mass materials instead of steel), we need 1.7E24j to deflect a ship typically and 1.7E25j from the Sun must be intercepted at 10% efficiency. So we need to intercept 1.63E18 watts and apply 1.63E17 watts to the ship's mag-sail if the deflection is done in 120 days. This means a collector with a radius of 7600 km. or twenty smaller ones with radii of 1700 km. This too should be within the abilities of megascale enginners of tomorrow. Silicon solar panels are about 15% efficient, gallium arsenide about 30% and gallium-inidium-nitride about 70%. We will need rare and exotic elements mined from stony-iron asteroids or from deep within Mercury, a dense and probably heavy metal rich planet. If we have 70% efficient panels and mass beam eff. is 50% max. then we are down to 35%. Super conducting cables, beam projector coils and the mag-sail itself will be very efficient, so an efficiency of 10% is not unreasonable if we can get high output solar cells. There might be photovoltaics of high efficiency made of mixtures of more common elements in the solar system yet to be discovered. Solar thermal turbogenerators running Brayton cycle turbines could reach 50% and low mass reflectors made of aluminum sheet could be used to focus light onto the helium "boilers." Turbogenerators are more complex than solar panels and will eventually wear out; however, photovoltaics start degrading when exposed to light and radiation reduces their output. They can be annealed with microwave heat to restore them every few years. The actual detials of the mass beam stations and their power sources remain to be worked out. More About Power Requirments If Proxima Centauri is thought of as a typical red dwarf, with a luminosity of just 0.00006 that of the Sun, then at 1 AU we get merely 0.081 watts per square meter. At 0.1 AU we get 8.1 watts/sq. meter. At 0.01 AU or 1.5 million kilometers we will get 810 watts/m2 and at 150,000 km., less that the distance from Earth to the Moon we will get a respectable 8100 watts/m2. Beam stations will orbit close to red dwarfs. Proxima is only 14.5% the diameter of the Sun or about 200,000 km. wide. The Moon is about 380,000 km. away, so Proxima would fit between our home planet and Luna. At 150,000 km. from the surface of Proxima the cicrumference of the orbit is 1,570,000 kilometers. A ring of 460 beaming stations, each 3400 km. wide, could be built around this star at this distance. We could even move closer in to 75,000 km and get four times as much energy per square meter ( 32,400 watts/m2) with 320 stations and a total of 2.8 times as much energy! Thus, a ring of stations each consisting of a 3400 km. circular collector orbiting 75,000 km above Proxima could intercept 9.4E19 watts and apply 9.4E18 watts to passing ships and pods at 10% total system efficiency. We need an average as discussed previously of 1.63E18 watts intercepted and 1.63E17 watts applied to sails (if sail is 100% eff.) to deflect passing ships.We have almost sixty times this much energy. Not to shabby for a tiny red dwarf star. A ring of 320 stations should not be beyond megascale engineers either. To propell a 500,000 ton ship up to 0.5c about 5.625E24 joules is needed. I'm ignoring relativistic mass increase again to simplify calculations, but this gets us in the ballpark. If the ship is accelerated away at 5G unmanned fresh out of the shipyards in orbit around Sirius A or another hot blue-white star rich with energy, it will take 35.4 days to reach 0.5c and cross 230 billion kilometeers of space or about 1500 AU. Fast acceleration means less distance to cruise velocity and less mass beam spread. Power applied to the ship must be 1.837E18 watts. Power intercepted at 10% system eff. must be 1.837E19 watts. At 1 A.U. from Sirius insolation is 31,050 watts per square meter. Sirius is 23 times brighter than our Sun. At 0.1 A.U. we will get 3,105,000 watts per square meter! Ive read of solar cells illuminated at 400 suns or 540,000 watts per square meter. This would be really intense. If we use reflectors made of dieletric films at 99% reflectivity about 31,000 watts per square meter would be absorbed. This might be too hot! If we settle for an intensity of 400 suns, or 540,000 watts/m2 we must locate energy collectors at 0.24 A.U. To intercept 1.837E19 watts we need a collector area of 34 trillion square meters or a circular collector with a radius of only 3300 kilometers. The collectors orbiting Sirius that harvest enough energy to give the ships their initial velocity of 0.5c don't need to be much larger than the ones orbiting the Sun that are used merely for deflection and pod accel/decel. assuming they can handle the intense illumination and heat. The mass beam projectors will have to be larger and they must be shielded by foil or dielectric films from the intense light of Sirius to help keep their superconductors cold. By tapping the intense radiation of blue-white stars like Sirius we will not need to build enormous partial Dyson shells around dimmer stars like our Sun to propell beamriders on their way out into the network and the scale of the project is reduced. This makes it more plausible. Even in a future with almost limitless robotic labor efficiency and economy will be important so that more work can be done faster and more robotic labor can be devoted to building space colonies of all sizes, terraforming planets, mining out shell worlds, constructing world houses, mining the atmosphers of planets like Venus or the Gas Giants, erecting space elevators and ring worlds and providing for the demands for survival and luxury for trillions of humans and other beings in the galactic civilization of the future. About Ships Since mass beam stations won't have to be so huge at energy rich Sirius and other star systems where ships are built from local resources and sent on their way, the robots can devote more time and effort to building fleets of highly sophisticated ships. The ships don't need to be spartan metal dungeons like today's submarines. They could be furnished inside with fine furniture and art works, carpeting and tapestries, some made by human artisans and others robot made. Elaborate dumbwaiter systems could convey meals to private cabins. Kitchens wth every culinary tool known and farms that produce a wide variety of foods from fast growing genetically engineered crops as well as meat cell cultures could be a part of the ships. Fine dinnerware could be provided also. Android gourmet chefs could whip up meals to satisfy any palate. Super sophisticated VR, computer and electronic communication systems could be installed. Passengers could wear tiny wireless phone earrings and communicate with anybody anywhere on the ship and send as well as receive messages across time and space via the ship's interstellar laser telecommunication links. The most advanced medical equipment and drugs could be obtained in sick bay as well as the best android doctors. The android crew might be the most complex creations of them all, more complex than the mass beam projectors and ships themselves, aside from the AI computers that run the ship. Three dimensional stereolithographic machines could produce almost any item requested including toys for kids. There could be nano-manufactories both dry and wet (bio-nano) aboard the ship. Public baths, holographic theatres, spas, recreation rooms, biotassis chambers, laundries, android barbers and hair stylists, new clothing and shoes from android tailors and nano-textile mills, recycling systems, would all add to the sophistication of the ships. The ships might have hulls with a layer of nano-bots that can seal or "heal" the hull rapidly if it is penetrated by a colliding small object. I don't think collision with a small object will result in a nuclear explosion level event. The object will go through the hull and bulkheads like a high power bullet without releasing all that kinetic energy. If the nano-layer in the hull can seal the wound rapidly pressure will not be lost. If someone is hit this will be terrible, but perhaps the object will miss the passenger's brain and just knock a leg or arm off and she or he could be rushed to sick bay, stabilized, and stem cells used to grow new limbs or organs to repair the unfortunate passenger. Robots and the Future Robot labor throughout the galaxy will also be hard at work producing homes and mansions with luxurious baths and sun rooms, skyscrapers and food as well as trillions of private autos, boats and airplanes way beyond the vehicles available today; private spaceships also. You name it the robots make it. Airships? Deep submersibles? Balloon borne villages in the sky? Custom made spacesuits? Retro clothing, furniture, telephones, mechanical typewriters, reading material printed on paper the old fashioned way? Booze? Musical instruments? Mass transit systems? Powerplants? Broadcasting, cable, telecommunication and internet systems? Hospitals? Flying ambulances? Micro-implants to monitor your health and record medical data over time for analysis by doctors that can send out emergency signals and summon up a flying ambulance with android paramedics and doctors aboard if you are injured or have a heart attack? Orbital satellite systems that watch over travelers in autos, boats, airplanes and monorails to prevent accidents and send help if there are accidents, as well as navigate the vehicles? Why not? It's all possible. Don't forget all the water and sewer systems, trash pick up and recycling, robot police and firemen also. Custom made cars with luxurious styling could fly and be driven by computers. Boats could be high speed hydrofoils. Airplanes could take off and land vertically. Underground mass transit systems (subways) could have supersonic bullet trains in them. Subterranean railroads could haul freight at low speeds. Moving trains and large factories underground with the help of robot miner armies could restore the countryside and prevent the destruction of nature on other planets. Concrete super highways? Who needs them with flying cars? Engineers could design nearly anything regardless of cost and the pragmatic financial decisions of executives when robots make everything inexpensively compared to human labor as long as industrial activities don't threaten a planet's ecosystem. Ultra-high yeild genetically engineered crops as well as food from chemicals could reduce the amount of farmland needed and save forests. Half the farmland today is used to grow livestock feed. If we culture meat, poultry and fish cells in underground food factories we could have our omnivorous tastes without growing all that feed, working with filthy animals and disgusting slaughter houses and polluting rivers with animal manure. That would save a lot of forests and prairies. Genetically enhanced humans of the future might have more efficient metabolisms and digestion so that they need to eat only a fraction as much as we do today and their hunger drives could be managed also with genetic alteration and non-toxic appetite suppressant drugs. Obesity could be conquered. Humans would eat less, live more, save forests and other biomes from the ax and the plow, and spend less time on the toilet! Open water mariculture could supply food also. On Earth and similar oceanic planets there's plenty of area at sea. Floating cities could be surrounded by genetically engineered floating aquatic crops for food as well as fiber and other products. Decorative aquatic flowers could also be cultivated to beautify these aquarian cities. Eventually, it might not be necessary to till the land anywhere. Humans and other beings could live in total harmony with Nature thanks to advanced technology. So it makes sense to make the interstellar beam rider network as efficient as possible for relativistic two way travel amongst the stars rather than devoting a large fraction of the robot labor pool to giant Dyson spheres and massive ships that stop at each destination and are propelled back up to cruise velocity. In the same way that we don't want to destroy Nature on the surfaces of planets, even seemlingly lifeless planets like Mars and lifeless planets like the Moon by putting transportation and industry underground including pipelines of all sorts and using fusion reactors located underground along with the power grid instead of covering thousands of square miles with solar panel farms or even rectennas for receiving power from orbital solar power satellites, we don't want to destroy the cosmos with Dyson spheres covering millions of stars. Dyson clouds or more probable, Dyson discs, of space colonies won't harm anything as space is vast. I say Dyson discs because I am not sure about having millions of space colonies in different orbital planes that might collide, but with intelligent planning of orbits this might be perfectly safe. Ring worlds would be mere threads around planets and stars, unless they were exceptionally thick. Space elevators would rise up into the sky and disappear in the blue. Human and super-human creations could augment Nature rather than deface it. |
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