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Fire in the sky, O'Neill colonies and asteroids
"Peter Fairbrother" wrote in message
... Lawrence Gales wrote: What is this obsession with spheres, torii (toruses?) and cylinders? It's very earth-bound thinking. Those are shapes that make for very efficient pressure vessels, which a space habitat essentially is. The advantage of a sphere is that it represents the greatest volume with the least amount of surface area. Since the surface area of a space habitat must be shielded from cosmic rays, that means 6 foot thick walls, which greatly affects overall mass. As is the desire for one g, but let that slide. I think assuming 1 G is required is the conservative and safe assumption we should start out with. We can start getting more experimental later on when we've accumulated more experience with lesser levels of G. Two modules with a long rope between them. Set them spinning, and you have any gravity you like. In any size you like. Space is big, there is plenty of room. This is a perfectly sensible design for a near-term habitat of modest requirements. (Though I would prefer a pressurized tunnel over ropes or cables. I like the idea of being able to get up to the spin axis in an emergency under your own power and without a space suit.) The tori, spheres, and cylinders are long-term habitat designs where the design goal is not just to keep people alive and healthy but to recreate the most pleasant areas found on the Earth's surface. -- Regards, Mike Combs ---------------------------------------------------------------------- By all that you hold dear on this good Earth I bid you stand, Men of the West! Aragorn |
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Fire in the sky, O'Neill colonies and asteroids
"ralph buttigieg" wrote in message
... "Lawrence Gales" wrote in message news:Pine.WNT.4.63.0603022344180.3940@your-kgj38sd53j... (a) Instead of the spheres or cylinders which cannot be made small w/o sacrificing gravity, the Stanford Torus can be scaled down dramatically while retaining full 1 gee How? I think he means by scaling down the cross-sectional radius while leaving the overall radius the same. Think of a Stanford Torus with the proportions of a hula-hoop. -- Regards, Mike Combs ---------------------------------------------------------------------- By all that you hold dear on this good Earth I bid you stand, Men of the West! Aragorn |
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Fire in the sky, O'Neill colonies and asteroids
On Wed, 15 Mar 2006, Jim Davis wrote: Date: Wed, 15 Mar 2006 19:41:29 -0000 From: Jim Davis Newsgroups: sci.space.policy, sci.space.tech Subject: Fire in the sky, O'Neill colonies and asteroids Lawrence Gales wrote: For the 1st colony I select 1500 feet in major diameter and 43 feet in minor diameter, so using strict scaling it should be (1/4)*(1/10)*(1/10) = 1/400 of the mass of the Stanford torus (the last (1/10) occurs because the tube would be 1/10 as thick as well as 1/10 as wide). This yields a structural mass of 625 tons, but we will set it at 1000 tons to be conservative. Some comments: 1. You've gone from 1 rpm from the original Stanford design to 2 rpm in your scaled down design to maintain 1 g. That will probably not be acceptable. ====================================== Well, O'Neill believed that it was acceptable, and it is my undestanding that most people be can be accustomed to 3 rpm, so 2 rpm should not be a stretch ================================================= 2. 1000 tons is about 5 times the mass of ISS and yet you intend to accomodate 200 people? ===================================== That is the raw structural weight w/o air, water, soil, shielding, etc. I scaled it from the Stanford Torus which had 250 times the weight, but based on other scalings that I saw on the Stanford Torus website (which seems to have disappeared) it seems reasonable. Note that the 10,000 person torus offered huge open spaces and nearly luxury living, whereas this initial colony is more of a construction shack. It does offer nearly 1000 feet^2 per person ===================================== 3. 1000 tons is about 4 times the mass of the Airbus A380 which cost about $12 billion to develop and build and yet you estimate your first torus cost at $3 billion? Jim Davis ====================================== I specifically stated that I did not include development costs -- only production and transport costs. -- Larry ================================================ |
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Fire in the sky, O'Neill colonies and asteroids
Two modules with a long rope between them. Set them spinning, and you have
any gravity you like. In any size you like. Space is big, there is plenty of room. The longer the rope, the flatter the apparent gravity field - which is something you can't do easily with a sphere, cylinder or torus, you have to make those huge. Also it is less dizzy-making. And all it costs is a bit of rope. -- Peter Fairbrother Yes you can do that, but how would people get on and off such a station, with out having to despin/respin, each time you want to transfer personel? I would suggest going with one of the dumbbell designs, with a ridged shaft, that would have a non rotating hub with an elevator car that would link the two ends and the hub. What we really need to find out, is there a minium exceptible g level that humans can handle w/o any debliating effects, that could drive the minium diameter that would be required for spacesettlements. Just my $0.02 Space Cadet |
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Fire in the sky, O'Neill colonies and asteroids
Space Cadet wrote: Two modules with a long rope between them. Set them spinning, and you have any gravity you like. In any size you like. Space is big, there is plenty of room. The longer the rope, the flatter the apparent gravity field - which is something you can't do easily with a sphere, cylinder or torus, you have to make those huge. Also it is less dizzy-making. And all it costs is a bit of rope. -- Peter Fairbrother Yes you can do that, but how would people get on and off such a station, with out having to despin/respin, each time you want to transfer personel? I would suggest going with one of the dumbbell designs, with a ridged shaft, that would have a non rotating hub with an elevator car that would link the two ends and the hub. The elevator can always ride up the cable. I would suggest three habitat modules, connected by cross cables, to maintain a rigid structure. But there is no need for compression structures. What we really need to find out, is there a minium exceptible g level that humans can handle w/o any debliating effects, that could drive the minium diameter that would be required for spacesettlements. Agreed, and in different scenarios. What gravity is needed for: - Convenience for tourists over 1 week - Comfortable living over six months - Human pregnancy and birth |
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Fire in the sky, O'Neill colonies and asteroids
"Space Cadet" wrote in message
oups.com... What we really need to find out, is there a minium exceptible g level that humans can handle w/o any debliating effects, that could drive the minium diameter that would be required for spacesettlements. The old "Pioneering the Space Frontier" study suggested an orbiting "variable G research facility" as an early goal, reasoning that the lessons learned there would affect the mission design of the rest of the program. -- Regards, Mike Combs ---------------------------------------------------------------------- By all that you hold dear on this good Earth I bid you stand, Men of the West! Aragorn |
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Fire in the sky, O'Neill colonies and asteroids
http://en.wikipedia.org/wiki/Electromagnetic_pulse
The problems of EMP effects from nuclear pulse rockets is overstated. Let's look at what causes EMP. This from the FAS; A high-altitude nuclear detonation produces an immediate flux of gamma rays from the nuclear reactions within the device. These photons in turn produce high energy free electrons by Compton scattering at altitudes between (roughly) 20 and 40 km. These electrons are then trapped in the Earth's magnetic field, giving rise to an oscillating electric current. This current is asymmetric in general and gives rise to a rapidly rising radiated electromagnetic field called an electromagnetic pulse (EMP). Because the electrons are trapped essentially simultaneously, a very large electromagnetic source radiates coherently. The pulse can easily span continent-sized areas, and this radiation can affect systems on land, sea, and air. The first recorded EMP incident accompanied a high-altitude nuclear test over the South Pacific and resulted in power system failures as far away as Hawaii. A large device detonated at 400-500 km (250 to 312 miles) over Kansas would affect all of CONUS. The signal from such an event extends to the visual horizon as seen from the burst point. Typical Weapon sizes quoted in such scenarios are in the range of 20 Megatons. This is roughly 1000 times the sizes of the weapons the United States used in Japan at Hiroshima and Nagasaki which were 20 kilotons. Nuclear pulse rockets would use explosives that are far smaller still! Around 200 to 2,000 ton TNT equivalent yeild And modern microfission and microfusion concepts would be smaller yet in the 20 ton to 2 ton yeild range. The Orion concept involves a pusher plate that does not contain the blast so, could produced EMP at the altitude range indicated. Freeman Dyson proposed the Helios concept where the explosion would be totally contained in a thrust chamber. I envision an anti-matter catalyzed fusion bomblets consisting of of Boron-11 and Protium yeilding He4 and 8.5 MeV per event reacting in a supersonic nozzle. http://www.iop.org/EJ/abstract/-sear...5515/44/10/004 This nozzle is not the sort of convergent divergent nozzle proposed by Dyson having such poor performance. The nozzle I envision is a parabolic pusher plate that directs the bulk of the blast by reflecting the shock wave formed deep inside the nozzle at its focal point. The tiny bomblet is a point source of alpha particles (He4) radiating in all directions in a very dense pulse. They bounce off the nozzle, scattering propellant that coats the inner surface of the nozzle whose momentum is conserved. The interaction time is short, and the entire output of the pulse unit is deflected into useful thrust. A thin layer of propellant - a waxy semi-solid plastic material pumped through pores in the nozzle surface - pulses from the surface, much as in the Orion pusher plate - the combined kinetic energy creates a wave of high speed matter that flows away from the parabolic plate and out of the nozzle absorbing the output of the entire blast. Since there is no direct illumination of the atmosphere there is no compton scattering and no EMP possible from these tiny 2 ton TNT yeild blasts. Since the wave moves through the nozzle in microseconds, dozens of bomblets can be detonated per second, 2 tons of TNT produce 8.36 x 10^9 joules around 10^10 joules. At a rate of 20 blasts per second this is a jet power of 200 billion watts of power. If each blast consumes 1 kg of material, that's 20 kg/sec mass flow rate. At this power level the exhaust velocity is 141 km/sec and the thrust is 2,800 tonnes. So, this could lift a vehicle 2,000 tonnes - and only 124 tonnes of propellant would be needed to blast it into orbit. Another 300 tonnes of propellant would be needed to carry this vehicle to the moon and back, after soft landing there. A total of 1,000 tonnes of propellant with 1 million tiny bomblets, and a total of 100 milligrams of anti-matter - would be sufficient to carry this vehicle on a fast trajectory across the solar system, landing on any planet and returning to Earth. Only 3x10^15 anti-protons are required to trigger each blast. Since there 6.02x10^17 per microgram - a single microgram of anti-matter could detonate 200 blasts. In a 10 minute launch to orbit, at 20 detonations per second, 12,000 micro-fusion blasts would take place. 60 micrograms of anti-protons would be consumed. This is a rate of 100 nanograms per second. At 90 kJ per nanogram - this is an anti-matter power usage of 9 MW. about 1/20,000th the power of the jet. A Fermi-Lab sized anti-proton maker operating at 9 GW would produce sufficient anti matter to launch one of these daily. This is what I'd like to see built over the next few years. A fleet of these would scout the solar system and do early exploration. These could be enlarged, increasing the bomblets to 2 kiloton TNT equivalent yeild, the same amount of anti-matter per blast to trigger, and 2 million tonne vehicle, with 1 million tonne payload. lol. These would be the freighter fleet to carry industrial payloads, establish cities and ports across the solar system - and begin development of off world resources They would have the scout class vehicles as ship tender and escape vessels! lol. * * * * Lawrence Gales wrote: On Wed, 15 Mar 2006, William Mook wrote: Date: Wed, 15 Mar 2006 19:41:46 -0000 From: William Mook Newsgroups: sci.space.policy, sci.space.tech Subject: Fire in the sky, O'Neill colonies and asteroids The size of the spacecraft payload determines how much sheilding we can carry along - and this is determined by the size of the rocket, and the power of that rocket. When sheilding requirements are added in, chemical rockets become impractical. However, nuclear pulse rockets are very practical - being the right size, and right performance to carry along the needed sheilding - both from cosmic sources, and the propulsion system! lol. http://en.wikipedia.org/wiki/Nuclear_propulsion Of course, a series of engineered nuclear explosions can also be used to move asteroids, and can be used to move space colonies as well! In fact, that would be a cool thing to do. Build a space colony, and then attach a propulsor to move the colony, once established, to another world, and then using that as an orbiting base, explore the world with piloted and unpiloted vehicles descending and returning from the surface. ============================================ I completely agree: nuclear pulse rockets operating in deep space (and hence free from the problems of nuclear fallout and EMP) are so vastly superior to any other means of propulsion that I would be astounded that NASA does not pursue them, except I know that NASA actually has zero interest in real space flight. -- Larry |
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Fire in the sky, O'Neill colonies and asteroids
Lawrence Gales wrote:
This is partly in answer to the Scientific American article about cosmic rays likely preventing human spaceflight. I have long believed that O'Neill colonies are vastly superior to Mars or any other planetary surface as an abode for human life and development: (a) They permit nearly total control over sunlight, day-night cycles, temperature, atmosphere, radiation, and gravity, all of which can be set at earth normal levels, or to almost any level you desire (b) Initially they will be positioned in near earth-moon space reducing the problems of radiation, transport, communication, and rescue. (c) They have access to energy that is superior not only to that which you find on Mars, but better than anything on earth -- solar energy in free space far from the shadow, gravity, or atmosphere of any large planet or moon has no rival (d) When they are later built in the asteroid belt they have access to materials enough for hundreds of times the surface area of earth. (e) Scaled down, highly modified versions of such colonies propelled by Medusa type fission-fusion nuclear blasts will permit manned interstellar flight However, as Henry Spencer once told me, most believe that Mars colonies can start out small whereas O'Neill colonies require huge up-front costs, as the smallest Island I colony of O'Neill can't be made much smaller than 3 million tons if it is to provide earth normal gravity. But two things have changed: (a) Instead of the spheres or cylinders which cannot be made small w/o sacrificing gravity, the Stanford Torus can be scaled down dramatically while retaining full 1 gee (b) Asteroids such as Nereus, which require only tiny amounts of energy to move material to L5, drastically reduce the cost of raw materials for L5 Here are the economic assumptions I make: (a) All the costs are for production and transport, not design. (b) The launch cost is assumed to be $1M/ton ($500/lb) to LEO, $4M/ton to L5, and $5M/ton to soft landing on the Moon (c) The cost of manufactured materials in space is set at $1M/ton (same as current aerospace) (d) The mass of material to be launched from the earth into space for construction of a product is 20% larger than the mass of the final product. So first let us look at the O'Neill/Island One concept: (a) The mass driver on the Moon weighs 10,000 tons and launches 600,000 tons/year at 2.4 km/sec for 6 years to send 3.6 M tons or 7.2B pounds to L5. The cost would be: $5M*(10,000 + 2000) + $1M*(10,000) = $70B or ~ $10/lb to L5 (b) The earth launch to L5 is 42,000 tons, so the cost is: $4M*(42,000) + $1M*(42,000) = $210 Billion So the total cost of Island One is $280 Billion Agree with you about O'Neils vrs Mars. Liked your post, but I've had another thought regarding the economics of building them. Thought I'ld toss it out. The cost advanmtage of lunar mass, rather then Earth launch is based on launch costs. But launch costs are sensitive to flight rate, since the upfront program cost to field a good launcher is at least a couple billion. Divide that over a 100 flights and your talking 10's to 100's of million of $ a flight, before you buy or launch the craft. Launch 10,000 flights and said developmental overhead drops to millions of dollars. Given all your proposals talk at least about lifting tens of thousands of tons, I think you have to consider the economies of scale of the launch infrastructure. For example. In the mid 90's McDonnel Douglas estimated commercial development (without political overhead and expenses) of a DC-X derived SSTO launcher at about $3 billion. For that your 20 ton DC-X ish shuttles can lift 20 tons a flight, fly 3-4 flights a week, and cost about $400 million each. Labor is about 800 man hours to prep for launch (amazing the improvements if you design for serviceability). Service life was estimated at 100-200 flights. 20,000 tons of lift over 3 years = 1,000 flights over 150 weeks, 6 2/3 flights a week average = 5 ships good for 200 flights, 3 flights a week per ship, $2 billion worth of ships + $3 billion in R&D overhead = $5B = $5 million a flight = $125 a pound = 10 ships good for 100 flights, 3 flights a week per ship, $4 billion worth of ships + $3 billion in R&D overhead = $7B = $7 million a flight = $175 a pound On top of this 800 man hours, fuel, and spares runs a couple million a flight, so your in the $200-$300 costMcDonnel Douglas was expecting. Your lift costs are about half your estimates to LEO Now lets go crazy and budget the full 3.6M tons to LEO. 20 tons per flight = 180,000 flights = 900-1800 ships Your $3 billion in R&D drops to about $17,000 per flight. Ship cost per launch $2-$4 million = $50-$100 a pound to leo plus labor and parts. $720B to LEO. We could quibble that if you order that many ships you cost per ship could drop WAY down, but lets keep going. Of course by now you might really want to invest more upfrount and get a VERY well worked out class of RLVs, with more service life, cargo capacity, etc. Say a 600 flight capable Star-Raker or super DC-x with 100 ton to leo capacity. After you drop $20B in R&D, $400M per ship 3.6M tons to LEO. 100 tons per flight = 36,000 flights = 900-1800 ships R&D per flight $0.6 million purchase cost per flight $0.6 million (might want to pay a bit more for longer lasting RLVs.) Assuming labor and parts per flight are also down (which seems likely with this size market to provide lessons learned) you could be looking at $10 for your 200,000 lb of cargo. At this point you actually need to consider fuel and such. $20-$30 a pound to orbit is possible - but near the limits for chemical launchers. 3.6M tons to LEO. = 7.2B pounds = $140 - $210 Billion total lift cost of your prefab Island L-5 colony, not your reference $280B. At this point does the development and servicing of the Lunar mass driver and catcher even make sence? You need to field the RLV launchers anyway, and they need to be far more reliable and advanced then all current ones so you don't kill a crew and ship ever 50-60 flights. Cost of prefab gear for said city is a lot cheaper if your buying everything prefap on earth for $'s per pound for prefab gear, and far less for your heavy shielding (reinforced concrete anyone?). Labor costs drop since more work can be contracted out to folks on the earth - anywhere on the earth. So is the cost to develop/field/service/ and operate the Lunar launchers and orbital catchers make much sence? Again your not estimate costs to develop, and operate the lunar system, or for that mater the asteroid tug (though I expect that would easily beat any earth to LEO based system without a space elevator. |
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Fire in the sky, O'Neill colonies and asteroids
This is the second time I've responded to this - so I don't know what's
up. Seems whenever I talk of things nuclear it gets canned once or twice before appearing. lol. * * * EMP NOT A PROBLEM Okay couple of points about EMP. The problem with EMP is over-stated. That's because EMP occurs for big blasts - 20 megatons or more - occuring between 20 km and 40 km altitude in the atmosphere. At that pressure and temperature, the big gamma ray burst from the blast creates a huge number of compton scattered electrons over a wide region - scattered off the atmosphere, which all interact coherently and recombine coherently to make a big ass electromagnetic pulse that can knock out continental sized areas. Which is cool, but not what we're doing with nuclear pulse. Blasts in the 20 kt range - 1/1,000th the size of the blast we're talking about, blasts like those in Hiroshima and Nagasaki - which didn't have EMP - have very limited EMP effects when detonated at the right altitude. Blasts in the 2 kt range and below, something the Orion would use, would have even less effect if any. And, advanced designs, like the Helios proposed by Freeman Dyson, would contain the blast effects entirely which means zero EMP at all altitudes. Now Helios turned out to have very small thrust to weight and so that's used to argue against total confinement, but details count! lol. An unconventional nozzle that operates like a pusher plate, but shaped to capture the spherical wave front and redirect it (think of a parabola being illuminated by a point source wave at its focus) wouldn't suffer the same performance problems as the publicly released Helios design - which allowed the heat of the bomblet to thermalize a working fluid and expand it out of a conventional nozzle. Finally advanced nuclear engineering can make very interesting reactions possible. STRAWMAN DESIGN FOR A PRACTICAL INTERPLANETARY CRUISER For example, think of Protium (plain vanilla hydrogen without isotopes) and Boron-10 - heat that sucker up quickly to maintain density - meeting the Lawson criterion - with a small number of anti-protons (about 3x10^15) and you've got a nice bomblet that produces nothing but alpha particles, no neutrons gammas or anything. And Boron-10 and Protium are easy to obtain, and cheap. The resulting alphas (He4) have about 8.54 MeV if I recall correctly. And a small quantity produces 2 ton TNT equivalent yeild. That's about 8.36 GJ per blast. Say 10 GJ per blast. Anti-protons have 90 MJ per micro-gram. A gram has 6.02x10^23 anti-protons. So, a microgram has 6.02x10^17 anti-protons. That's enough anti-protons to detonate 200 bomblets. A nanogram has 6.02x10^14 anti-protons - so, you need about 50 nanograms per bomblet to trigger a fusion reaction. A solid state -microsized- penning trap can store this easily. The size of the fusion reaction is determined by the amount of fusion material you have, since the shock wave created by the anti-proton blast can propagate once the Lawson criterion is met. The key to this design is how quickly you can dump your anti-proton pulse, and how tightly you can focus the beam! And this is easily achieved with anti-protons at normal pressures and temperatures. So, with anti-proton triggered Boron-10/Protium fusion bomblets each yeilding 2 ton TNT equivalent yeild. The resulting alpha pulse flash evaporates a few kg from the shaped pusher plate (unconventional nozzle) where everything starts out supersonic and stays supersonic lol - no thermalization, and everything has the same advantage as the orion plate, but you capture the entire blast as thrust. With the evaporated material consisting of waxy semisolid plastic administered through pores in the underlying shaped titanium plate - and 20 blasts per second - you'd have a jet power of around 200 GJ, you'd use antiprotons at a rate of 90 MW - and btw you could easily replace them with something like the size of Fermi lab in Chicago, adapted to produce anti-protons exclusive and cool them and capture them in advanced penning traps - residing at the centers of the bomblets. (actually you'd have the traps on the side of the bomblets and pulse them through a feed line into the center as you compressed the whole things with explosives - this for safety's sake so you could have two part bomblet that couldn't detonate until you put the parts together and launched it into the nozzle) This system would produce 2800 tonnes of thrust and lift a 2000 tonne vehicle into orbit by consuming around 12,000 bomblets, and 120 tonnes of propellant if I did my maths right. 300 tonnes of propllant would allow you to fly to the moon, land and come back. 900 tonnes of propellant would allow you to fly to any part of the solar system on a high speed orbit, land at your destination and come back. A nice sized scout ship with a crew of 15 to 20 perhaps - judging b the size of comparable submarines and naval research vessels. It would also be a nice 200 foot space yacht for wealthy folks. lol. Or if a latter day Henry Ford could arrange for large scale production, we could have one at every space yacht club across the world! lol. People would rent them the way they now rent yachts for sailing on the weekend at Chesapeake bay. lol. LARGER SHIPS POSSIBLE Some of the research done by the Orion project, and other research after suggests that with larger bomblets (but the same sized triggers) we could increase jet power and so vehicle size, by a factor of 1,000 - by creating a 2 kt bomblet. This far larger engine - would lift a 2,000,000 tonne vehicle and allow for the industrial development of solar system resources. We could put big chunks of cities and space ports, bases and industrial systems on the planets with this sort of vessel. This would be a freighter sort of vehicle - with perhaps a crew of 30 to 50 in a freighter mode. As a cruise liner type ship, one designed to carry lots of people in comfort - suitable for carryiing colonists leaving Earth perhaps, or just tourists visiting the planets - you'd have 5,000 to 10,000 people, and maybe 1,200 service staff - or by then perhaps robotic staff! lol. It would be large enough to carry the scout class vessels as ship tenders. A fleet of 1,200 ships of the larger ships operating across the solar system would be capable of establishing interplanetary nations throughout interplanetary space. Construction of a few million a year of the smaller ships would complete the picture. Vessels of various sizes between these two extremes would be constructed, mostly for police or military or special scientific use. ENOUGH FUSION FUEL TO POWER LARGE FLEETS 19.8% of all Boron found on Earth is Boron 10. In 2005 according to the USGS the US produce 657,000 tonnes of Boric Oxide (B2O3) - and Boron is 11 and Oxygen is 16 so on a molecular basis we have 22 + 48 = 70, so 22/70th of this amount is Boron itself, so that's 206,480 tonnes of Boron - and 19.8% of that is 44,800 tons of Boron 10. Boron is found in Borax, and if we paid to process all the Boron 10 out of the Boron being mined, we could easily achieve 3 to 5 times this annual production rate from existing resources on Earth. Of course as we expanded across the solar system, Boron would be something we'd be looking for. Protium isn't a problem, its plain hydrogen and there's lots of that in water and other things. We can produce 74.7 GJ per gram of Boron/Protium mix. So, we use about 1/8th gram of boron per 2 ton blast - about the size of an aspirin tablet, and 125 grams of boron per 2 kt blast - a bottle of aspirin. So, a gram produces 8 of the smaller bomblets, a kilogram 8,000, a metric ton 8 million, 1,000 metric tons 8 billion, 10,000 metric tons 80 billion, and 50,000 metric tons 400 billion - of the smaller ones, and 400 million of the larger ones. There are 31.56 million seconds in the year - that's 12,674 of the smaller bomblets per second to achieve 400 billion production rate. At a rate of 20 per second, that's a continuous firing of 633 scout class ships - and with a 2% duty cycle - you're thrusting only 2% of the time during flight - that's a total of 31,685 ships in flight - and with a 10% flight time to hanger time - comparable to aircraft, that's a total of 316,850 ships system wide. If this were larger freighters, that's only 316 freighters system wide. If we could increase Boron production on Earth 10x - which should be aciheveable - and half were allocated to the smaller ships and half to the larger - we could have 3 million scout class cruisers and 3,000 freighter class cruisers. Enough to create a sort of sci-fi fantasy world where space travel were common place. If 25% of the 3000 freigher class vessels carried 100,000 people per year off world, that's 750 vessels x 100,000 = 75 million people per year. That's about 1% of the world's population and equal to the world's population growth rate. Other trechnologies might be superior. Solar pumped lasers to support laser rockets, or tethers, might augment, and surpass the capacity of fusion powered rockets. But, we clearly have the technical means, if we had the will, to create the sort of interplanetary culture space enthusiasts dream about with fusion rockets today. * * * Lawrence Gales wrote: On Wed, 15 Mar 2006, William Mook wrote: Date: Wed, 15 Mar 2006 19:41:46 -0000 From: William Mook Newsgroups: sci.space.policy, sci.space.tech Subject: Fire in the sky, O'Neill colonies and asteroids The size of the spacecraft payload determines how much sheilding we can carry along - and this is determined by the size of the rocket, and the power of that rocket. When sheilding requirements are added in, chemical rockets become impractical. However, nuclear pulse rockets are very practical - being the right size, and right performance to carry along the needed sheilding - both from cosmic sources, and the propulsion system! lol. http://en.wikipedia.org/wiki/Nuclear_propulsion Of course, a series of engineered nuclear explosions can also be used to move asteroids, and can be used to move space colonies as well! In fact, that would be a cool thing to do. Build a space colony, and then attach a propulsor to move the colony, once established, to another world, and then using that as an orbiting base, explore the world with piloted and unpiloted vehicles descending and returning from the surface. ============================================ I completely agree: nuclear pulse rockets operating in deep space (and hence free from the problems of nuclear fallout and EMP) are so vastly superior to any other means of propulsion that I would be astounded that NASA does not pursue them, except I know that NASA actually has zero interest in real space flight. -- Larry |
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Fire in the sky, O'Neill colonies and asteroids
The problem with EMP is over-stated. EMP occurs with very large nuclear
blasts, 20 megatons or more, at an altitude of 20 to 40 km, when a very large gamma ray burst scatters electrons off the thin atmosphere over a large area. Those electrons recombine coherently to make a huge electromagnetic pulse. Smaller explosions, Hiroshima and Nagasaki are 20 kt and are 1/1,000th the size of this explosion, didn't produce EMP. Explosions of the size of the Orion spacecraft would be less than 2 kt, and the EMP effects would be nearly non-existant. Also, Helios type spacecraft, like that proposed by Freeman Dyson, totally enclose the nuclear explosion in a nozzle that absorbs all the energy of the propelling explosion. So, there's no chance at all in creating an EMP. Now, Helios had proposed a sort of nuclear pulse thrust chamber that wasn't every efficient. And people have said that this inefficiency is a necessary feature of total enclosure. That's not exactly true. Performance, as always, depends on details. A supersonic nozzle, one where the propellant starts supersonically and continues flowing supersonically, has many of the features of the Orion pusher plate, while still affording total enclosure. Imagine a pulse from a small bomblet originating at the focal point of a parabola. The wave of energetic material strikes the parabolic pusher plate, and causes a directed wave to exit the base of the nozzle. This is distinctly different than say using a nuclear explosion to heat a large amount of propellant that is then expanded through a conventional nozzle. It has many of the advantages of Orion type pusher plates, but is more efficient in many ways - and totally eliiminates EMP. By compounding the nuclear pulse WITHOUT a fissile materials, we can create a relatively clean exhaust. Boron-10 and Protium ignited by 3*10^15 anti-protons - about 5 nanograms - can generate energetic pulses of between 2 tonne TNT equiv. to 2,000 tonne TNT equivalent. Detonating these tiny pulse units at a rate of 20x per second, we can lift vehicles ranging in size from 2,000 tonnes to 2,000,000 tonnes and carry 50% of this mass throughout the solar system. Boron-10 & Protium produce alpha particles only. No neutrons, no gamma rays. Helium-4 that's it, at 8.54 MeV per reaction. A particle accelerator the size of Fermilab could be built specifically to produce anti-protons. Penning traps made of solid state materials can be made to efficiently store and transport the needed anti-protons, and deliver them in a form that is concentrated enough - in time and space - to exceed the Lawson criterion and setup a detonation wave in the Borton-10/Protium mix. Since hydrogen and boron can unite chemically to form borohydrides, these bomblets need not be too complex. Since 20% of the world's supply of Boron, extracted mostly from Borax in Turkey and elsewhere, the world might produce 50,000 tonnes of Boron-10/Hydride per year at fairly reasonable costs. At 75 MJ per gram - equivalent to the energy contained in 12 barrels of oil, this 50,000 tonnes per year of material could yeild 21x more energy than we now produce by burning oil. This is enough energy to fly thousands of the very large rockets and millions of the smaller rockets. In any case, we have the means to develop industrially the entire solar system. Lawrence Gales wrote: On Wed, 15 Mar 2006, William Mook wrote: Date: Wed, 15 Mar 2006 19:41:46 -0000 From: William Mook Newsgroups: sci.space.policy, sci.space.tech Subject: Fire in the sky, O'Neill colonies and asteroids The size of the spacecraft payload determines how much sheilding we can carry along - and this is determined by the size of the rocket, and the power of that rocket. When sheilding requirements are added in, chemical rockets become impractical. However, nuclear pulse rockets are very practical - being the right size, and right performance to carry along the needed sheilding - both from cosmic sources, and the propulsion system! lol. http://en.wikipedia.org/wiki/Nuclear_propulsion Of course, a series of engineered nuclear explosions can also be used to move asteroids, and can be used to move space colonies as well! In fact, that would be a cool thing to do. Build a space colony, and then attach a propulsor to move the colony, once established, to another world, and then using that as an orbiting base, explore the world with piloted and unpiloted vehicles descending and returning from the surface. ============================================ I completely agree: nuclear pulse rockets operating in deep space (and hence free from the problems of nuclear fallout and EMP) are so vastly superior to any other means of propulsion that I would be astounded that NASA does not pursue them, except I know that NASA actually has zero interest in real space flight. -- Larry |
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