| Points to Ponder On other pages I have suggested using miniature neutron stars instead of miniature black holes to generate propulsion beams and even to power Bussard ramjets (presuming a Bussard ramjet powered by something more powerful than fusion could overcome drag in the interstellar medium) because I erroneously thought that miniature BHs would evaporate rapidly. Let's see: BH lifetime in seconds = M3/3K K= 3.98E15 kg3/sec (not to be confused with deg. K) Thus, a 7.7 million metric ton BH from one million cubic meters of iron would live for: (7.7E9 kg)3/ 3K = 3.82E13 seconds or 1.2 million years! Not bad. Our starships won't last nearly this long and these objects could power colonies in deep space beyond the limits of the outer planets for a long time. A 7.7 million ton BH would work well with a 25 or 30 megaton Rama class vessel. It's mass would be about the same as the magsail loop determined earlier. Combined with a Bussard ramjet the vessel would have manueverability independent of propulsion beams, tugs, etc. The limitations due to mass beam dispersion over distance would be overcome. Is it too good to be true? What about the ram scoop? If the magnetic scoop can harvest matter with a vast magnetic field one million km. in diameter and there is one hydrogen ion per cubic centimeter of interstellar space we find that over a distance of 2E12 kilometers, the distance covered in 236 days at one G acceleration up to 66% c, 1.6E39 hydrogen ions will be collected. Dividing by Avagadro's number, 6.02E23, we find that this equals 2.66E15 grams or 2.66 billion tons of hydrogen ions. That's more than enough for the jet mass. Certainly we can get by with a smaller ram scoop. With a scoop area about 1/100 or about 100,000 km. wide we can harvest a mass of ions about equal to the mass of the enormous Rama. The coils for generating the magnetic scoop would not be nearly as large. If our mini-BH can energize the ions to high fractions of light speed the ship can reach similar speeds. MV=MV Now we must look at the snags.* The temperature of the mini-BH can be found by: approximate Temp. = 1.228E23 deg. K per kg./M Our 7.7 million ton mini-BH will have a temperature of about 1.595E13 degrees K.! Since: peak wavelength = 2.989E-3 meters/ deg. K the object will radiate gamma rays at 1.874E-16 meters (1.874E-7 nm) or 1.6E24 hertz The energy of the rays will be: E= (4.136E-15 eV-s)( 1.6E24 cps) = 6.62 Giga electron volts. Those are some pretty high energy rays! Most materials will be transparent (so we can forget about a light sail) to gamma rays at this energy but they will also undergo ionization. How will this effect the superconducting coils that contain the mini-BH and the structure that supports the coils? I can't answer that question. Will intense currents in the coils fill the holes left in the outer orbitals of the elements that compose the coils? Will electrons kicked out of atoms jump into holes in the outer orbitals of other ionized atoms? Will a sort of fortunate chaos of electrons in the superconductors result? Or will the compounds be disrupted? Perhaps superconductors could be bombarded with high energy gamma rays in the GeV range to determine experimentally what happens. How's anybody going to get research funding from the government to do that? "Well, honorable senators of the science sub-committe, we want to build a starship..." "What? Build a starship when billions of people on this planet are hungry and living in sub-standard housing! You get the Golden Fleece award!" Remember the honorable (depending on how you feel about him) Mr. Proxmire? Now, if we were designing some kind of weapon for ballistic missle defense...Like a mini-BH powered energy beam of immense destructive power...At this point we will face eggs thrown by radical feminists, environmentalists and people who hate the WTO and the Iraq war. Many of us will be sleeping on the couch longer than President Clinton did after the Lewinsky scandal and told to think about solar energy or never have sex again...depending on what kind of woman you have in your life, of course. What about the luminosity of the mini-BH? L= 3.568E32 watts-kg.2 / M2 Thus, our mini-BH emitts 6E12 watts. That's pretty bright. About 1.55E-14 as bright as the Sun. However, it will be shining with Hawking radiation in the high energy gamma ray region of the spectrum and be invisible. If the structure that contains the mini-BH as I have pictured it is about 2 km wide it will be illuminated by 478,000 watts per square meter. Perhaps there will be so little absorption, compton scattering, particle pair production, etc. that the structure and the coils don't heat up, but what about the passengers? The giant Rama has passenger hulls a kilometer or two away. Even so, they and the electronic micro and nano-circuitry of the computers will probably get fried!!! So things don't look so good after all. Perhaps we can still build huge propulsion beams with coils and structures 20 km. wide or more that are blasted by 4780 watts per square meter, about 3.5 times the brightness of light from the Sun at Earth's distance, although in the form of high energy gamma rays. There will also be energy emitted by the spiraling gas we feed to the mini-BH to form the propulsion beams that jet from the accretion disk of the spinning weird object. Finally, there is the actual production of the mini-BH. Perhaps we could implode smaller masses of iron and then increase the mass by feeding matter to the object although up to 40% of that mass will be converted to energy. We would be wise to stay far away from the mini-BH so that we don't get fried by all the radiation. So what now? We seem to be back to propulsion beams and mag-sails or magnetoplasmic sails. Magnetoplasmic sails might be better than standard mag-sails consisting of a superconducting cable loop. The plasma bubble could be maintained with liquefied gas stored on the ship and we won't have to worry about damage to it as we would a cable loop. The Rama vessel is built around a magnetic coil that serves as a deflector of incident particles that hopefully won't create too much drag. This same coil could control the plasma bubble. The bubble would catch the propulsion beams and be used for braking. What about an antimatter powered ramjet? To propell a 25 megaton Rama up to 66% c we'd need 5E26 joules of energy and this could come from the annihilation of 5,555,555 tons of mass. So we'd need about 2,777,777 tons of antimatter to react with an equal amount of matter harvested by the ram scoop. I don't know if it will ever be practical to produce this much antimatter, contain it in magnetic bottles safely, and I don't know what kind of radiation problems would result from such a huge antimatter rocket engine generating 2.45E19 j per second during a 236 day acceleration at one Gee to 66% c. What next? How about a mini-neutron star? This could convert 10% of infalling matter to energy and it would not shine with Hawking radiation. Seems like a good idea. Let's look a little closer. If we can take a million cubic meters of iron amassing 7.7 million metric tons and slam pieces of this together at relativistic velocities using solar powered propulsion beams and mag-sails or compress smaller masses with thermonuclear explosions in deep space then feed matter to the object to accrete a larger mini-ns we might be "in business." Since a neutron star has a density of 1014 grams/cubic centimeter, this object will be: 7.7 gr/cc)/x = 1014 gr./cc x= 7.7E-14 (106 cubic meters or 1012 cc)(7.7E-14)= 0.077cc It's radius will will be 0.264 cm If a gram of highly compressed matter falls on it, so we can ignore the radius of this mass, the force will be: F= GMm/r2 = (6.67E-8 cm3/ gr sec2)(7.7E12 gr * 1 gr)/(0.264 cm2) = 7369002 gr cm/sec2 or 73,690 gr m/sec2 or enough force to accelerate one gram at 7520 Gees. That isn't much. Seven point seven million tons of mass doesn't have much gravity. The escape velocity is even more pathetic. u=GM= 513590 Vesc= SQRT( 2u/r) = 3839 cm/sec or 38.39 meters per second Unless I have goofed, a 7.7 million ton neutron is not much to be afraid of or proud of... Since a nuetron star has an escape velocity of about 50% c we can make another calculation: 1.5E10 cm/sec = SQRT ( 2u/r) r = 1027180/ 2.25E20 = 4.56E-15 cm volume = 3.96E-43 cc density = 1.94E55 gr/cc That's much denser than a neutron star. It's pretty close to the density of a black hole. Rs = 2GM/c2 = (2*6.67E-8 cc/gr-sec2 *7.7E12 gr.)/ (9E20 cm2/sec2) = 1.141E-15 cm volume of event horizon = 6.2E-45 cc density = 1.24E57 gr/cc The density is actually infinite for the singularity. We can see that a 7.7 million ton object dense enough to accelerate matter to 50% c which will impact and give up its kinetic energy which will be roughly 10% of its mass energy (we'll skip that calculation) is much denser than a typical neutron star. It would be more like a mini-quark star. It would also probably be unstable and might collapse into a black hole. Like a quark star it might be very hot and cool rapidly. Who knows? As it absorbs mass it will probably collapse into a black hole or it might just explode. We have no experience with such things. So what now? What if the 7.7 megaton object with neutron star density of 1014 gr/cc had an intense magnetic field, much stronger than its gravity that could accelerate ions to relativistic velocities? It would be like a mini-magnetar. Although its gravity isn't much, its magnetic field might do the job of accelerating ions and crashing them into its magnetic poles where they give up their kinetic energy. Again, we have no experience with such things. We don't know if we could even create such objects anymore than we could ever produce megatons of antimatter. What if we abandon Rama for now and think about smaller starships? A 25,000 tons ship at 66% c would need 5E23 joules of energy. If we accelerate at one G for 20,400,000 seconds (about 236 days) we must produce 2.45E16 watts for the propulsion beam at 100% efficiency. Let's say we have a system of solar collectors and particle accelerators and can miraculously siphon mass from the Sun with magnetic scoops to supply mass for the beam that has a total system efficiency of 10%. We need 2.45E17 watts. If the solar collector is within the orbit of Mercury at 50 million kilometers we get 12,150 watts per square meter. We need a solar collector about 4500 kilometers square ( about 20 million square km.) This might be possible in the future of mega-scale engineering and it doesn't require anything as exotic as antimatter or mini-black holes. A 25,000 tons ship might have a mag-sail about half its mass and it would not carry a large crew. It would take about 6.5 years to reach Alpha Centauri and about 5 years would elapse aboard the ship. A naval destroyer has a mass of 10,000 to 12,000 tons but this thing would be made of super lightwieght materials instead of steel and be more voluminous; however, we'd have to include the cosmic ray shield mass and that would decrease passenger living space. Our crew would find themselves lock up inside a ship for 5 years. This might not be very pleasant. If cyrostassis is possible the crew won't mind 5 years of confinement and the ship might be even smaller or carry more humans. Large, slow freighters would travel to the destination star system many decades beforehand with a number or replicating AI robots to build habitat in the destination star system and even solar collectors and propulsion beams for return flight. I have a lot of faith in AI. The destination would be well charted ahead of time with huge space telescopes and robotic probes. Is cryostassis possible or will ice crystals form in the frozen body fluids of humans and puncture cell membranes causing fatal damage? Proteins and nucleic acids could be damaged by super cold temperatures thereby making resurrection of the "corpsickles" impossible. Are human space travelers the future? What about androids? Perhaps we could construct skeletons of metal or super polymers, attach artificial muscles made of polymers that contract when electrified, cover the bodies with polymer skins that have millions of microscopic touch, pressure and temperature sensors imprinted in them much the way we make microcircuits on chips. Semi-conducting polymers are possible. Proprio-reception microsensors could be installed in the artificial muscles. High resolution camera eyes, microphone ears, and small gryoscopic balance sensors could be provided. Taste and smell might not be necessary. Electronic brains that store information in the molecular structure of modules that store quintillions of bits of memory might be possible. The androids could power down for years at a time and "wake up" when arriving at destination star systems. They would be powered by nuclear batteries and have no need for food, water or oxygen. Androids could be our ambassadors to other star systems. Would they be alive or just mimic life? What is conciousness? What is the soul? If the soul exists could we transfer ourselves into android bodies that last for thousands of years and travel freely amongst the stars, or would this be hideous to most human animals? And if we can grapple with the soul and store it in some kind of crystal perhaps, why not just load the ship up with magically crystallized souls and some sperm and ova along with some artificial wombs, then grow new biological bodies and enter then mysteriously when we arrive at destination star systems...This is beyond science. If such things like soul transfer were possible then why not telepathy, precognition, instantaneous teleportation to anywhere in the universe and other miracles??? I am certain that we could manufacture androids but as for souls and such, I don't know. Although we can play with numbers and hypothetical ideas about miniature black holes and other things we have no actual experience of hard engineering data about such things and I am not a professional astronautrical engineer or physicist. Greater minds than mine are at work on these things and may come up with surprising inventions. Travel to the planets of the solar system can be done with chemical rockets, nuclear thermal rockets, nuclear electric drives, cycling stations, mag-sails, solar sails and in coming decades even fusion. We might make it to the stars with fusion if we are willing to take about a century to reach the nearest star system. Such a journey would probably be a one way colonization mission with genetically engineered humans who can live for over a century, maybe several. Much progress is being made in genetic science and in the causes and cures of aging. Aging may have more to do with evolutionarily planned obsolescence than anything else. Is interstellar travel every going to be practical or even desirable? Man and woman might someday create a civilization on Earth and on the planets and moons of the solar system and in space colonies without war, poverty, most disease, and even without crime. Much bigotry and hatred would have to be overcome as well as technological progress. We would have to develop a greater understanding of the human psyche than religion or law has ever provided. There are still people in this world chanting "Death to America" and there are people preaching hatred in America. If humanity can overcome its ignorance and prejudice and avoid more major wars and progress out of hatred, the future could be glorious. I won't live past mid-century in all probability. I may die before then. Unlike many scientists I believe in a Universal Spirit but as Diests believe we must take action rather than wait for God to fix things. I believe in life after death, even the possibility of reincarnation, although I can't seen why one would give up the joys of eternal life in the hereafter to return to Earth. Perhaps many lifetimes are needed to learn all that one must learn to live peacefully in the after life. Nobody has ever come back from the dead they say, but there have been prophets and supposedly there have been visitations by angels who have told us about the life beyond death. I've met people who went to the devil for answers and they convinced me that devils exist, therefore there must be a God, or I am just plain schizoid! Once again, this is not science. If we can create an Earthly utopia, not quite heavan because death will still exist and other miseries of the body like old age and broken bones, unpleasant biological functions, etc., and even take vacations on the Moon or journey to Mars, why bother with interstellar travel? We could send robotic probes to other star systems propelled by fusion or solar powered propulsion beams and these probes could radio back 3D images of the surfaces of other worlds. Mobile landers, robotic airplanes and orbital probes could send us images that can be enjoyed in 3D cinema displays. So why go there? Why leave the technological utopia of tomorrow to risk death on a planet orbiting Tau Ceti and sacrifice decades of one's life also to get there and back at 66% c? Most people are happy with the basic essentials, some luxuries, a happy family and social life. If technology from medical science to robotic mass production can secure all these things and free people from hard work and allow them to pursue their favorite interests and recreations, why would they care to travel to other stars? We won't do it to keep expanding the human population I am certain of that. More people today are concerned with down to Earth things like losing weight, improving their sex life, getting healthy, exercising, and paying the bills. Some people take vacations by jet airplane and go on cruises. Other people are worried about getting enough to eat, controlling their birth rate, and just surviving. In some parts of the world people are living a neolithic existence and in other places they are practicing female circumcision and slavery even exists. There are war zones where people are mutiltated horribly. Humanity has a long way to go. We still build houses out of flammable wood, burn fossil fuels and don't bother to build earthquake or hurricane resistant structures. Now that we know where the earthquake and hurricane zones are we must wonder why people continue to live in those places. I guess they don't have the money to move! Humanity has a lot of improving to do. We could feed the world if we just didn't feed so much grain to livestock for meat! It all boils down to economics. Robotic mass production and even robotic farming could dramatically improve economic conditions. People could go to work in all kinds of social service jobs or become skilled craftsmen and work shorter hours too. The reality of space travel today is apparent to anyone who watches the news. Many people question the value of the manned space program. There should be no questions about the value of weather, GPS, resource monitoring, communication and defense satellites. Solar power from space and helium 3 fusion fuel from the Moon are real possiblities. Geothermal energy from shafts bored into deep rock is also a possibility. The energy future is unclear but we can be certain that petroleum will run out, prices will go up, and global warming will become obvious to the most hard headed skeptics. Thinking about space travel is no crime. It is fascinating. Science fiction is no crime either. We all need to escape into fantasy sometime. But are our scientific and science fiction visions any better than Leonardo's designs, Jules Verne's cannon or Cyrano de Bergerac's various ways of reaching the Moon where he met the prophet Elijah? What if through some greater understanding of physics it becomes possible to overcome inertia or travel in higher dimensions of hyperspace as some science fiction writers suggest? Relativity demonstrates that there is something more to the universe than the ordinary three dimensions we can perceive. Could we set up gravitational vibrations, warp space, and teleport to any place in the universe? Does reality exist within a cosmic mind that can make or break all laws of physics? Is there an infinite sea of vacuum energy in which all observed matter and energy exists? And if we could tap this energy, could we avoid blowing ourselves up with it? If we do venture to other star systems and encounter intelligent alien life, will we see them as potential customers, wiser than ourselves or inferior, creatures to wage war against, or will we go through all the trouble and expense of interstellar travel just to ask them if they believe in God? And what if they look at us like we are crazy and say," God? We never thought of that before. You humans sure are queer." |
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| * After I wrote this I discovered that the interstellar medium might contain only 0.01 hydrogen ions per cc. Well that makes drag less of a problem, it also kills any kind of ram scoop. See: Centauri Dreams page |
| Sources for equations can be found at thinkquest and hyperphysics |