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| Advanced Interplanetary Ships Interplanetary Ships to Match Mighty Star Arks Required Enormous starships of the distant future, when war and biogtry ( let's hope so), poverty and diseases of the body and mind (mental illness, addiction) and most crime are long gone, must be complemented by interplanetary ships beyond the nuclear fission electric ships coming in this 21st century. Star Carriers that have decelerated from relativistic interstellar speeds and gone into orbit around destination stars will ride the solar winds of destination stars to maneuver at "low" speeds to rendezvous with space stations where passengers can transfer to small interplanetary ships for "short jaunts" to planets, moons, asteroids and space colonies of the destination star system. Large numbers of interstellar travelers like those aboard a Rama class Carrier will have many destinations in the target star system and one big ship can't take them all to each planet or asteroid one stop at a time. They will need to fan out in smaller interplanetary ships. Mag-sailing ships will haul interstellar travelers from Star Terminals, city sized space docks where the Carriers are harbored, to various destinations on multi-month voyages. In the inner solar system of the destination star the driver beams could be solar powered. Fusion powered ships could also be used for high speed interplanetary travel. With fusion engines that have a specific power of 4000 kW per kg. of system mass ships that can reach any planet in our solar system in a matter of weeks or months can be built. Oort Cloud dwellers will also need ships capable of bridging the average 20 AU. gap between comets and clusters of space colonies built from individual comets in the abyss. Imagine a 2000 tons ship capable of travel at about 250 kps, or 900,000 kph. If the ship is a mag-sailer or beamrider it will require 6.25E16 joules or the energy or the equivalent of 15 megatons of TNT. If this ship is based in the Oort Cloud, it will need a rather large protium fusion reactor and some powerful drivers to propel it up to speed. Since these reactors and drivers are stationary, more or less, orbiting slowly around the Sun they can amass millions of tons while the ship's mass is kept as low as possible. The ship will brake with its mag-sail without expending propellant. It could cross 20 AU. in 140 days, not considering acceleration and deceleration. If the ship accelerates to speed in ten days the reactors and drivers must pump out energy equivalent to 17.5 tons of TNT every second or 72 GW for a week and a half. A protium reactor and a driver beam several kilometers long should be able to do that without too much strain. I envision protium reactors as enormous devices with particle accelerators several kilometers long to ram hydrogen nuclei together. Future lasers or even muon catalyzed fusion may make this kind of reactor less of a behemoth. A propulsion beam energized by an artificial miniature neutron star "fed" with cometary hydrogen to generate plasma beams is also a possibility. Since these machines will last virtually forever in the rust free vacuum of space and they will be built by AI robots under human supervision, the entire gross domestic product of the world won't be dumped into this endeavor. In the distant future we will be beyond money and beyond financial limitations thanks to AI and the immense natural resources of outer space. Time of flight is always a challenge. Presuming that people of the future will be genetically engineered for increased intelligence, longer life spans and capable of hibernation by activating enzymes used by hibernating mammals still present in humans today, it will not be surprising if most people spend a few years in rotating hibernation during long space voyages. By rotating hibernations I mean a few months of torpor followed by a few months of wakefulness and repetition over a number of years. Whether or not this is possible and safe for the human body with genetic modification is unkown at this time. If hibernation is possible this will reduce logistical demands and smaller faster ships can be used. Antimatter? What about antimatter propulsion? Let's envision a 2000 ton interplanetary ship using matter-antimatter (m-am or amat) propulsion. Let's give it an exhaust velocity of 10,000 kps and a delta V of 500 kps. Using a computer program we find that a ship could make it from Earth to Saturn in only 66 days with delta V of 485 kps (close enough to 500 kps). That's 230 kps at departure and 255 kps arrival. There shouldn't be too many places farther than Saturn is from Earth from our Star Terminals. Using the rocket equation: e^(500/10,000)=1.0513 1.0513*2000=2102 tons, thus we need 102 tons of reaction mass. Using the Newtonian kinetic energy equation, because the velocities involved are not high enough to worry about the relativistic correction: K.E.=0.5(102000kg)(10,000,000m/s^2)= 5.1E18 joules Since 5.18E18j=m(300,000,000m/s^2) m=57 kilograms of antimatter Presuming we could manufacture the stuff and store it safely in some kind of magnetic bottle, it doesn't seem to hard to believe we could energize 102 tons of liquid hydrogen reaction mass in some kind of magnetic nozzle based engine. Now let's say we run this thing for 14 days, 7 for acceleration and 7 for deceleration, we have (5.1E18j/(3600*24*7)= 4.13E12 joules/second or 4.13 terrawatts of power to handle. At 4000 kW/kg. the engine amasses about 1000 tons or half the ship. That's reasonable. The Saturn V first stage engines ran at 1.62E11 watts or 217 million horsepower. Our amat engine will be equal to 52 Saturn V first stages or 260 F1 engines. However, it will not be thrusting tons of mass every second. It will be expelling just a thin stream of plasma at a low thrust level for one week at a time. The super hot plasma will be magnetically contained and most of the emitted radiation will be reflected back into the plasma. Another way to utilize antimatter will be amat-magsail pulse. See: Propulsion Critique 2. Small bombs or pulse units consisting of magnetic bottles with small amounts of amat in them and small tanks of LH2 are ejected from the tail of the ship. The magnetic bottles are discharged and the amat and normal matter of the LH2 annihilate each other with some of the LH2 being superheated to a high speed plasma that spreads out an applies pressure to a mag-sail 50 kilometers in diameter. The enormous energies of the pulse will spread out in a could of plasma. It will not contact anything composed of matter and fry it. The passenger section of the ship will be located far from the small detonations and the radiation will be thoroughly dissipated. There will also be radiation shields. Beamriders! The 2000 ton beamrider described earlier performs a similar flight as the amat ship with a deltaV of 500 kps, 250 kps departure and 250 kps arrival by braking in the solar wind plasma, with only 6.25E16 joules of energy instead of 5.1E18 joules and no reaction mass aboard the ship at all. This is far more efficient. The beamrider doesn't need any reaction mass if it uses microwave or laser sails and this greatly simplifies logistical operations. It uses solar energy or mini-black holes to power the propulsion beams and has no potential for exploding. It can also use its sails to solar sail with free photon pressure from the central star in the inner system. It can use a combination of light sails propelled by microwave or laser beams and mag-sails to brake. Since interplanetary speeds are much lower than interstellar speeds and the interplanetary plasma is much denser than the interstellar medium, mag-sail braking is highly effective for IP vehicles. Also, the 2000 tons beamrider is almost all spaceship, with just a few hundred tons devoted to sail, powerplant and cooling systems. If the ship uses mag-sails, which are actually lighter than light sails, it can ride around on the solar wind and it can pick up plasma propulsion beams from stations in stellar orbit. DRIVER beams like those used to propel CARRIERs orbiting near the Sun or another star might harvest solar wind gases with huge magnetic scoops or siphon matter directly from the solar surface with magnetic scoops and feed then into mini-black holes to create jets of plasma. If harvesting solar winds is not possible then microwave and laser sails with mag-sail brakes are the way to go. See: Solar Sailing At greater distances from the central star where the solar wind is weak matter can be mined from asteroids, ice moons or the atmospheres of gas giant planets to feed the DRIVERs. Propulsion beams could be located near the Star Terminals to send ships on there way. Since the gravity of the Terminals and Drivers will be so weak they won't have to be located at Lagrange points or regions in relation to each other. They will probably be located at L points in relation to other planets. It might be best to locate Star Terminals near the central star so that interplanetary ships can fan out to other destinations under intense power from DRIVERs located near the star. Beams would be required at other planets to send the mag-sailers back to the Terminals; however, a magsail can operate in reverse. It can lose speed and fall into a fast cometary orbit towards the Sun. It can even use magnetic attraction between the Sun and the sail to pull it down towards the Sun even faster. Star Terminals Star Terminals could be located close to the destination star so that the drivers can tap solar energy. Also, synodic periods between bodies in fast orbits near the Sun or any other star and worlds beyond are shorter than anywhere else in any planetary system. In other words, launch windows to and from Mercury to or from any other planet in the solar system are more frequent than for any other planet. So locating Star Terminals near the central star is ideal. The driver beams don't involve harvesting a tremendous amount of mass, just a lot of energy with streams of plasma particles whose mass is largely the result of relativistic factors. We must also consider the possibility of Carriers going into orbit around Earthlike planets from which most travelers could descend via space elevators to the surface while others boarded ships that were launched by the rotation of the ring to various destinations in the target solar system. A solar system is a big place. I find it hard to believe that 40,000 people on a Rama class Star Carrier would all be headed to the same place. If they were headed to the same planet we could get them there, send them down the space elevator and then let them find their own way to cities of interest via lifting fuselage Bernelli airplanes, titanium sea going ships, high speed monorails and electric automobiles. But some are going to be headed elsewhere and there is no reason to sail a giant Carrier to hundreds of different planets, moons and asteroids for just a small number of people. Common sense! From a centrally located planet or Terminal near the Sun or another star they can spread out. They can launch without fuel from a planet girdling ring world directly to other planets or to rendezvous with interplanetary cycling stations, thus once they leave the Terminal and travel to their first destination, they can travel by other methods to other planets. A system of interplanetary cycling stations in colonized star systems for travel between specific worlds will be reasonable. The cyclers will use solar sails, mag-sails and gravitational assists to keep their orbits synchronized with other planets. Small ships flung from ring worlds could fly to moons of another planet and fuel for landers can come from various sources like aluminum and oxygen for chemical rockets or hydrogen, water, methane or ammonia mined on icy bodies for NTR. It will become necessary for travelers to wait at the arrival planet or Terminal until the planets of the destination system are in the right position for travel. One will have to plan his interstellar voyage in great detail with the help of highly intelligent travel agents and AI computers. The purpose of most star voyages will not be reaching a destination to do business; that can be done via radio or laser communication, but for the sake of the trip itself. Deluxe accomodations will be available everywhere. Downsizing My Own Vision I once calculated that a partial Dyson sphere that I dubbed the RAVEN that collected 10% of the Sun's energy with a total system efficiency of 10% could harness enough energy to send 900 giant starships amassing 2.5 billion tons each with ten million people aboard for a total of nine billion people on their way at 66% c every year to nearby stars. We could probably cut everything down by a factor of one thousand, and still have nine million interstellar voyagers every year in 900 Carriers with just 10,000 people each. That would be a more realistic vehicle than a 2.5 gigaton ark given today's visions of space colonies. A Bernal Sphere with 10,000 people at 66% light speed is still nothing to sneeze at. However, the surface area of a sphere increases with the square of the radius while the volume increase with the cube. Thus, a larger spherical hull has a better passenger volume to hull surface area ratio, and the most massive component of the vessel is the radiation shield the mass of which is dependent on the surface area of the sphere. A larger vessel can thus carry more passenger per mass of the vessel and this is more efficient. This is the best reason for building smaller numbers of large STAR CARRIERS than greater numbers of smaller ones. With DRIVERs powered by mini-black holes instead of the gargantuan RAVEN that might be right. If humans can live 120 years then a trillion could travel to other star systems over the course of a human life time. We might see giant starships someday carrying hundreds of thousands or millions of people after all. Besides, a larger vessel will be a more interesting place to spend five or ten years inside of. There's always the possibility that we might have to evacuate the Earth and colonies on other worlds of our solar system because of some terrible natural catastrophe, but that's unlikely. |
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| More pages related to matters discussed above. See: Interplanetary Tourism |
| Many thanks to Peter Kokh for his input regarding pages in the IP Tourism index. Also, see: Spaceships and Moving the Masses Thru Space |
| Rama class Star Carrier and fusion powered interplanetary ships for conveying passengers to worlds of the destination star system |
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| Space colonies in the destination star system built by earlier colonists serve as terminals for the large numbers of people arriving by Star Carriers. Star farers stay in space colonies until launch windows to other worlds of the system occur. |