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#72
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Moon Base baby steps
In article ,
Greg D. Moore \(Strider\) wrote: "Joe Strout" wrote in message ... In article , (Russell Wallace) wrote: On 24 Jan 2004 06:30:13 -0800, (Alex Terrell) wrote: ........................ No. People have stayed in microgravity for extended periods of time; staying on the Moon will be no worse than that (and may be quite a bit better, for all we know). "Ah we sure?" Seriously, we may find the 1/6 g isn't enough to prevent calcium loss, but is enough to make bone breaks more likely than in orbit? So we take lots of calcium pills. At any rate, we are not likely to get answers unless we try, and there will be plenty of volunteers. This is not likely to be the only problem with living in reduced g. The answer is not on earth. -- This address is for information only. I do not claim that these views are those of the Statistics Department or of Purdue University. Herman Rubin, Department of Statistics, Purdue University Phone: (765)494-6054 FAX: (765)494-0558 |
#73
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Moon Base baby steps
(Henry Spencer) wrote in message ...
In article , Ross A. Finlayson wrote: I'm trying to get an understanding of the relationship of exit velocity, launch track length, G forces, and power. Anybody have a chart of that? v^2 = 2*a*d, where v is exit velocity, a is acceleration, d is distance (length). Something that can reach orbital velocity, assuming fairly low atmospheric-drag losses, ends up being around 4600 G-km, so getting the length down to 10km or so requires operation at several hundred Gs. NB, this assumes constant acceleration. Note that you would need a small rocket stage in the projectile, because an Earth-surface catapult *cannot* put something directly into orbit -- it can reach only orbits that intersect the atmosphere, so a bit of rocket fuel is needed to finish the job. P = m*a*v, where v and a are as before, m is projectile mass, and P is peak power. This is up in the gigawatts even for m=100kg; clearly one needs local power storage that can be charged up slowly and discharged very quickly. (t = v/a, so that 10km track is covered in about 2s.) Neglecting losses, energy is 0.5*m*v^2, so for m=100kg we need about 1250kW-hr per shot. Note that 100kg is almost certainly much too small to get acceptable atmospheric drag losses, and for that matter the drag loss assumed in the above example numbers is probably too low even with higher mass. This is different from a rocket which also makes a sonic boom and spews tons of poisonous gasses onto the launch pad, at irregular intervals. There's nothing particularly poisonous about the exhaust from a LOX/kerosene or LOX/LH2 rocket. The Earth to Orbit Mass Driver is a better environmental alternative to unassisted rocketry. A point of terminology: this is a catapult, not a mass driver. The two terms are not synonymous. A mass driver is a particular type of catapult, which accelerates its payloads in payload carriers, "buckets", which are decelerated and returned to the head end for re-use. The launch apparatus is completely reusable, hundreds, thousands, and perhaps hundreds of thousands of times. It's also extremely expensive. Its use introduces no toxins directly into the environment. Its exit shock wave will be rather hard on the surrounding environment. ...Electricity may be from greener sources... Or not, as the case may be. Ten kilometers is around six miles, let's say that the goal is to provide orbital velocity and also exit velocity, the orbital insertion booster is presumably robust, but on failure the ballistic projectile should not return to Earth. I can see why you think a mass driver is O'Neill's "High Frontier" electric racetrack with the regolith bucket, but an electromagnetic catapult is still a mass driver. I prefer to call it a mass driver personally. Thanks a lot for those calculations. The shockwave seems to be the Earth-to-orbit mass driver's drawback, in terms of operation and not construction. Again, to reiterate, in comparison with the alternative, rocket launch, they each suffer that issue. So I'm trying to get a better idea of what the launch tube would look like. I can agree that we would want pretty much constant acceleration, I think that means that each of the coils, say ten feet diameter rings, about six inches thick, spaced a couple feet apart, for say, one coil per meter or ten thousand coils. Here you may be able to tell I only have encountered the notion of using a gauss gun for orbital velocity recently. So anyways there are these coils, and then there are guide rails that the supercooled payload levitates upon via superconducting electromagnetic levitation, or plain old magnetic levitation, or a sled or wheeled cart sabot, thus that the hypersonic payload does not actually contact the coils. The coils are completely inerchangeable, they are each identical. They are also one piece construction with no moving parts. The power storage and perhaps generation facility is nearby, it must be able to incrementally store and quickly release the power into the coils in a carefully synchronized way. I guess this is the role of the capacitor and one of the issues to be resolved in the five year design stage of the multi-million dollar project. Let's see, orbital velocity is, uh..., let's see, the mass of the Earth is 6*10^24 kg. F = G m1 m2 / r^2, the "Universal Law of Gravitation", I thought it was little g, the gravitational constant G is 6.7 * 10^11 Newton meters^2/kilograms^2. F = ma. Escape velocity is that instantaneous velocity which will be decelerated by gravity between Earth and the pod thus that when it reaches the point where Earth's gravity is nominal it still has non-nominal velocity, where Earth in its own orbit around the sun does not catch up with it. That's about not an orbit but shooting it away from Earth, directly away from the center of the planet, and having it near balance there. http://www.physlink.com/Education/AskExperts/ae158.cfm ETOMD doesn't shoot the pod straight up, that would require a ten kilometer launch tower or sunken shaft. Instead, it should take advantage of the topography to get as steep an angle as it can get on pod exit from the launch tube. Also the tube could be straight or constant curvature, preferably for simplicity of computation. So it has initial velocity components in two dimensions, the vertical velocity component, that being the one directly away from the center of Earth's mass, being required to be escape velocity or greater. This is what it would be designed to do on every single pod that is massed and balanced the same, for repeatibility and no pods falling back short on Earth. So anyways, the pod has left the atmosphere a couple hundred kilometers downrange from the launch track, maybe even in U.S. airspace. These kind of back-of-the-envelope/paper napkin calculations well make use of assumptions like "the Earth is spherical", "Earth's centroid is its center of mass" and "gravity is constant over the Earth" (re geodetic variation), "Earth orbital plane is at 23.5 degrees", etcetera. Maybe it should be launched at 23.5 degrees angle, or, well, whatever, depending on its latitude, perpendicular to Earth's orbit around the Sun. Also the Moon is sitting there in Earth orbit somewhere and its default escape path should either be in a path clear of the moon, or, perhaps it could take advantage of the Moon's location to shoot directly to Moon's orbit. That would be asking too much, as Moon orbits around the Earth in ways I don't know, ETOMD is a fixed emplacement, but many are obviously familiar with moon periods. I have to relearn a bunch of stuff to calculate escape velocity, the force applied by each coil to some hypothetical pod, by the energy, and what happens when the pod hits the air, depending on its composition, profile, velocity and atmospheric conditions. I have to relearn how to read a book because I know how to do none of that stuff except calculate escape velocity. "Dynamics of Multibody Systems - 2'nd Ed.", Tsuboi's "Gravity", Dover classics "Theoretical Kinematics", three or four tensor books, "Fluid Mechanics", this might help a lot: "Electrodynamics: A Modern Geometric Approach". Cripes, all this just to figure out what to put on the purchase orders for ten thousand ferromagnet or high temperature superconductor coils. Dang, if the coils each cost five thousand dollars then that's already ten percent of the project budget of five hundred million dollars, assuming the coils have no defects and need no replacement. In that case the track could be shortened to one kilometer, using one tenth the track length and having frighteningly higher acceleration. Or, maybe that's OK. The other project costs are the prepared track site, the presumably concrete footing for the thing, the power infrastructure, the capacitors, the capacitor synchronization instrumentation, shell and fairing for the launch track, perhaps airtight, cooling if superconductors are used, and command and control structures. I think the force is strongest between the coil and the pod when the pod is nearest to the coil, or is it inbetween that and distant? That is to say, I know a coil should be deenergized by the time the pod actually passes it, and not flip-flopped as this is pull design and not a pull-push design, that might use less power, but when should it be energized? What are realistic dimensions for the coils given the pod is to be designed to have a minimal aerodynamic profile, that is the droplet shape, the pod is to mass 2000 kilograms, etcetera? Please give your guesstimates on what the nuts and bolts of an Earth to escape velocity mass driver would be. You gave a figure of 1250 kwh for 100 kilograms, twenty times that for 2000 kg is around 25000 kwh, neglecting losses is several thousand dollars for electricity. That already puts a big dent in the launch cost, which is to be economical.If the pod, which has avionics and control systems, costs a hundred thousand, as they are produced by the thousands, that puts the actual launch costs at around a hundred thousand for the electricity and the pod, and then there are all the costs to run the command and control systems. Let's imagine: 250 000 for 1800 kilograms into space, that's around $140/kg. Nothing has ever been launched past Earth's gravity well for less than a hundred dollars a pound. The mass driver could run every daylight hour for years. People could launch their pets' ashes into space. On holidays it could coat the pod with pyrotechnic sparkle. It would be a good light show any day of the week. The Shuttle is currently, not including design, construction, and shelf maintenance costs, of billions and billions of dollars, running around some 25000 per kilogram, or 500 000 000 dollars to launch some 24000 kilograms. If the capacitors exist, the mass driver could be designed to launch instead of two thousand ten thousand kilogram payloads. That might just be twisting the knob. Of course, the mass driver is not designed for people, the acceleration forces we discuss would jellify a man. That would require a longer track, and perhaps a ten or fifteen second launch boost at less than four G's, it wouldn't make a louder noise. Well, I guess it's not exactly Earth to orbit, it's more Earth to escape velocity. There, it has control systems, of various kinds, special occasion launches, particularly if variable power could be used to apply different escape velocities, could help put the pods on their way to specific destinations. A hundred years ago the internal combusion automobile had to stop at an intersection, and the driver then had to get out and step into the intersection, light a firework and blast a horn, and offer all right of way to horsedrawn traffic. Two hundred years ago there wasn't a train track from coast to coast of North America or Europe and Asia. Fifty years ago no man had even been to space. It took almost seventy-five years after Wright's powered flight for a man to get to space. Today airports have decibel limits. Could building a coilgun system for beyond Earth escape velocity really cost less than one shuttle mission, and launching 250 tons with it to the moon less than two? Ross F. |
#74
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Moon Base baby steps
On 31 Jan 2004 09:20:21 -0600,
(Gordon D. Pusch) wrote: Why would you have that feeling? Argon is an inert gas, so it doesn't bond to anything (well, except for fluorine and chlorine, under contrived laboratory conditions), and its melting point is not that much higher than nitrogen's. You won't find frozen argon lying around until you're almost out to Neptune... But it's produced by the decay of potassium-40, so shouldn't rocks pretty much everywhere contain some? (Is that where Earth's argon supply comes from? Our atmosphere is ~1% argon IIRC.) -- "Sore wa himitsu desu." To reply by email, remove the small snack from address. http://www.esatclear.ie/~rwallace |
#75
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Moon Base baby steps
On Sat, 31 Jan 2004 10:42:06 +0000, Cardman
wrote: On Fri, 30 Jan 2004 21:16:57 GMT, (Russell Wallace) wrote: I'd have thought a modest-sized satellite would provide adequate living space and consumables for some mice for a few months? Hopefully such an experiment can be done aboard the ISS, when they have the right equipment that is. As that would be related to human sciences and can be better studied on the ISS. Then hopefully someone will do it there. Survive in the technical sense of "not dead yet", but I wouldn't call having your health seriously and to some extent permanently damaged "just fine". (Particularly since most of their waking hours have to be spent on keeping it at the "not dead yet" stage.) It's certainly not a viable basis for long-term human habitation of space, and if that's not the end goal, why are we spending money putting people in space at all? Taking claim of our rightful property? Why have just one planet, when there are countless numbers for the taking? Exactly - and to do that, we need to aim for viable long-term human habitation of other worlds, in environments that meet the requirements for sustaining health - which means we need to find out what those requirements are, particularly in terms of gravity. If putting people in space is to be more than a meaningless publicity stunt, it should be focused on viable long-term objectives, Since NASA cannot afford long term objectives, then that is why they are running "one step at a time" in order to build and support what they can afford in the future. Fine, but it would be more helpful to take one step at a time in the right direction rather than the wrong one. and that means coming up with ways to enable people to _live_ (as opposed to marginally survive) in space. Yes, just attach heavy weights to their ankles, wrists and torso, when 1/6th G will suddenly seem a lot heavier. That won't help. For example, it won't stop your immune system falling apart because cell division is botched without gravity to provide cues for the cytoskeleton. NASA certainly does need artificial gravity in Space though, when we known that lack of gravity is harmful. Yep. -- "Sore wa himitsu desu." To reply by email, remove the small snack from address. http://www.esatclear.ie/~rwallace |
#76
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Moon Base baby steps
On 31 Jan 2004 11:40:22 -0500, (Herman Rubin)
wrote: [living in 1/6 G] So we take lots of calcium pills. That won't necessarily help... At any rate, we are not likely to get answers unless we try But that's why I pointed out an easy way of getting a lot of the answers in advance. -- "Sore wa himitsu desu." To reply by email, remove the small snack from address. http://www.esatclear.ie/~rwallace |
#77
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Moon Base baby steps
"Gordon D. Pusch" wrote in message ...
(Russell Wallace) writes: On 29 Jan 2004 15:27:59 -0800, (Alex Terrell) wrote: Carbon is abundant in many NEOs. Nitrogen is a problem, but not a major problem until we move from Torus colonies to Cylinder colonies with their large volumes. Until then, a Heavy Lift Vehicle delivering NH3 is enough. As far as air-filler goes, wouldn't argon be an adequate substitute for nitrogen? I've a feeling the moon and asteroids ought to contain argon. (Someone correct me if I'm wrong.) Why would you have that feeling? Argon is an inert gas, so it doesn't bond to anything (well, except for fluorine and chlorine, under contrived laboratory conditions), and its melting point is not that much higher than nitrogen's. You won't find frozen argon lying around until you're almost out to Neptune... Actually there's always a little argon floating around the Moon as a product of nuclear decay, so some may be trapped in the ground. But I doubt that you could collect it, considering the Moon's atmosphere compressed to Earth pressure would fill only about a sports stadium, and that's mostly hydrogen from the Sun. Also the argon might be ra- dioactive isotopes themselves; I don't know that much about it... -- __ "A good leader knows when it's best to ignore the __ ('__` screams for help and focus on the bigger picture." '__`) //6(6; ©OOL mmiv :^)^\\ `\_-/ http://home.t-online.de/home/ulrich....lmann/redbaron \-_/' |
#78
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Moon Base baby steps
In article ,
(Russell Wallace) wrote: don't need to do that, we know that people survive a year just fine in much less than 1/6 G. Survive in the technical sense of "not dead yet", but I wouldn't call having your health seriously and to some extent permanently damaged "just fine". (Particularly since most of their waking hours have to be spent on keeping it at the "not dead yet" stage.) It's certainly not a viable basis for long-term human habitation of space, and if that's not the end goal, why are we spending money putting people in space at all? Well obviously, people are not going to be living (in the long-term habitation sense) in microgravity (*). But this is not a difficult problem to solve: you spin the habitat. We've known how to solve that problem for decades. Now, that doesn't work quite as elegantly on the Moon, and this may or may not turn out to be a problem for long-term habitation there. If it is, then maybe the Moon will never have many long-term inhabitants, but only term workers. I'm OK with that. But we won't know until we go set up base there and see how we do. - Joe (*) At least in biological form. Once mind uploading is developed, of course, we can build ourselves to be perfectly comfortable in a wide range of environments, including microgravity. But that probably won't happen in this century. ,------------------------------------------------------------------. | Joseph J. Strout Check out the Mac Web Directory: | | http://www.macwebdir.com | `------------------------------------------------------------------' |
#79
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Moon Base baby steps
(Gordon D. Pusch) wrote in message ...
(Russell Wallace) writes: As far as air-filler goes, wouldn't argon be an adequate substitute for nitrogen? I've a feeling the moon and asteroids ought to contain argon. (Someone correct me if I'm wrong.) Why would you have that feeling? Argon is an inert gas, so it doesn't bond to anything (well, except for fluorine and chlorine, under contrived laboratory conditions), and its melting point is not that much higher than nitrogen's. You won't find frozen argon lying around until you're almost out to Neptune... The Moon was formed in an impact with Earth so it has very few volatiles. In fact, the Earth has fewer volatiles than it should due to this event (compare with Venus). Mars, however, has plenty of easily accessable Nitrogen, and Argon. If extraterrestrial production and shipping of atmospheric components are at all economically worthwhile from any off-Earth location in the Solar System then the same from Mars would likely be very competitive. Also, Argon may not make the best filler gas for breathing. It's slightly heavier than air and also a mild anasthetic gas. Not really the best combinations. |
#80
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Moon Base baby steps
On 31 Jan 2004 11:40:22 -0500, (Herman Rubin)
wrote: At any rate, we are not likely to get answers unless we try Ah, looks like someone agrees with me about the best way to start getting answers ^.^ http://www.spacedaily.com/news/mars-general-04c.html -- "Sore wa himitsu desu." To reply by email, remove the small snack from address. http://www.esatclear.ie/~rwallace |
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