I have to wonder what definition of "feasible" you're using that includes a project requiring "the present power output of all electrical plants on the planet over a decade" and more copper cable than has ever existed.
Something that we could conceivably do within 50 years if we decided we really wanted to (along the lines of the Manhattan Project).
As opposed to, say, building a Dyson Sphere or some other project that requires either vastly more resources than are available, or materials that we have no idea to produce.
So, I've got to ask... how does this explain Venus?
It's actually Earth, and not Venus, that's the abberation. The only reason Earth doesn't have a Venus-like atmosphere is that the moon's influence agitated the atmosphere enough for most of it to be stripped off.
Venus has no moon, and so is stuck with a surface temperature at which lead gets mushy.
I used to think this to, but Titan has even less gravity than Mars yet keeps an atmosphere that is about 50% thicker than Earths.
Titan's also a lot colder than Mars.
The criterion for keeping an atmosphere, if I remember correctly, is for the mean velocity of gas molecules at the ambient temperature to be less than 10% of escape velocity. That keeps the fraction of molecules _at_ escape velocity low enough for evaporation to be negligible.
So, a colder world can get away with a shallower gravity well.
For a lark, I did the calculations for artificially imposing a magnetic field if the Earth ever lost its own.
It turns out to be feasible even today, though horribly, horribly expensive. You'd build a mesh of copper cables around the equator (or superconducting, but copper's losses aren't that bad for this). Then you'd slowly ramp up the current until you have a magnetic field comparable in strength to today's.
Ramping up would be slow because of inductive power storage. The current loop and associated magnetic field store a *vast* amount of energy, all of which needs to be provided in order to bring the field up to strength. The present power output of all electrical plants on the planet over a decade or so would do it, if I remember correctly, so this is feasible. The power cost to maintain the field, even with copper cables, is much lower; put, say, a 10% tax on electricity, and you've paid for the extra plants to feed the mesh.
You'd use a mesh instead of a single cable _because_ of the amount of stored energy. If you break the current path of an inductor, current flows anyways, arcing across the gap. This only dies down as resistive losses across the gap dissipate the power stored in the inductor. Think about this - all of the inductor's stored power is dissipated in one place (the break), and we're storing an awfully large amount of power in this current loop. If the loop was a single cable and this cable was broken, you'd get something in the range of a 10-gigaton yield at the point of breakage. A mesh provides many alternate current paths, so breaks from sabotage or just plain wear can be repaired safely (as long as you overspec the current rating enough to allow the other paths to safely take up the load).
A copper cable a hundred metres wide, or ten thousand one-metre cables, would do the trick. You might _have_ to use copper, too; even if you spread the cables out to make a more uniform field near the Earth's surface, field strength near each wire would be much greater than the breakdown point of most superconductors.
We'd probably never bother doing this, but it's a fun thought experiment:).
"Dr Paul Murdin, of the Institute of Astronomy, Cambridge. 'On Mars, when its magnetic field failed permanently billions of years ago, it led to its atmosphere being boiled off."
Whoa.. steady on there Dr.Murdin! That's quite a brave thing to say as if it's a fact. That's just on theory, and an interesting one to, but you cannot prove this yet. I'm sure there are lots of other reasons why Mars atmosphere is the way it is now.
If I understand correcty, the accepted one is that Mars's gravity well is too shallow to hold on to an atmosphere of anything lighter than carbon dioxide over geologic time (which among other things means that any terraforming won't be permanent, and that we aren't likely to find *much* water underground).
Arh! I think it will make some lovely daytime aurora, and generally play havoc with electrical equipment.
And greatly increase the mutation rate (solar wind smacking into the atmosphere will produce a fair bit of secondary radiation (X-rays)). While this won't do much beyond raising the cancer rate in any given generation, it will mean that a lot of genetic defects will start piling up over the years.
Not that I'm worried. By the time the field weakens enough for this to be an issue, we'll have enough medical expertise to rewrite our genomes as we see fit, so repairing damage won't be a problem. If we don't just put an artificially generated field in place to protect our electronics first (this is feasible, barely).
I'll also point out that no one really knows how the planet's magnetic field is generated.
Sure we do. It's from dynamo currents caused by convection in the (liquid) outer core.
Magnetic field flips happen when turbulence grows enough to disrupt these patterns briefly.
This is why Jupiter has a much stronger magnetic field than Earth (huge liquid metallic hydrogen layer, and a very powerful internal heat source), and why the moon has almost no magnetic field (no liquid core; the only field is the one that was "frozen in" when the moon first cooled).
Re:Save$,don't lift the materials fromEarth's surf
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Why in the world would you build a solar power sat from materials that are conventionally launched from Earth at $10,000 / kg?
Build them from lunar materials instead. The much shallower gravity well would bring your costs down to, at most, $100 / kg.
Plus the $1000,000/kg amortized cost of the lunar mining facility.
Mining of lunar material is only cost-effective if you expect to use millions of tonnes of it or more. Solar power satellites don't _need_ that much mass, especially now that thin-film photovoltaic cells are becoming practical.
If your beam intensity is large enough to be useful (many times the intensity of sunlight), then it will cook birds that fly through it
Only if you use wavelengths that are absorbed by the birds. That's not a reqirement, there is a whole spectrum available.
Birds will absorb anything from the low end of the microwave spectrum up through hard UV. Practical power relaying will likely be in the middle of the microwave range, as a collimated microwave beam is easy to produce efficiently and easy to convert back to electricity efficiently. Higher frequencies are hard on both counts, and lower frequencies are hard to drive at the required energies and have sloppier focusing.
In summary, all practical bands for us to use have this problem.
Have they ever managed to keep the plasma torus stable enough in a tokamak to use it? From what I understood, this was one of the main problems with research tokamaks, which was preventing the project from going further.
I've heard varying stories as to what the limiting problems are with current reactors (and all are probably true). However, an interesting development re. turbulence was made relatively recently. A group installed sensors and correction magnets on a tokamak, and suppressed the small irregularities in the containment field that turbulence produced. The result was much better confinement.
I don't have a link handy, but it might even have been on Slashdot many months ago.
My personal suspicion is that better materials will provide a big boost. I'm drooling over what nanotubes will do for anything that involves strong magnetic fields - they're the next best thing to superconducting, and their tensile strength means you can run an extremely strong magnet without worrying about it tearing itself apart. Both high density and long confinement times are much easier to achieve with a stronger magnetic field.
Isn't it strange that the publisher of Penthouse (Bob Guccione) is the only celebrity to ever endorse nuclear fusion, which is the only viable solution we are ever going to have to our insatiable lust for energy?
Funding for nuclear fusion is scarce, probably due to energy companies' opposition to anything that could possibly mean free energy.
Actually, this is wrong on pretty much all counts.
Fusion reactors are very big, and very expensive. This is why funding for fusion projects tends to get cut when economic belts are tightened. This is also why fusion energy will never be free - your plant has yearly costs (maintenance, and the amortized cost of building the plant over a reasonable payback window). These costs are passed directly on to the consumer, in the form of a nonzero price for electricity. The same happens with things like hydroelectric and fission power - the cost of the fuel required is low (or zero, for hydroelectric). You're paying for the plant/dam.
Lastly, the fact that electricity never will be free (due to the cost of facilities for producing/distributing it) means that a) there will be no magic free-energy solution, and b) our lust for energy had damned well *better* be sated, because otherwise we'll be awfully disappointed when we find out there isn't a free (beer) supply.
Oh, and if anything, I'd expect the big fossil fuel companies to be the strongest _supporters_ of alternative power sources. They're on top of the market now, and as soon as fossil fuel supplies wane and prices go up (or taxes on fossil fuel emissions rise), they'll want to be right there ready to sell the alternatives.
The process for creating a fusion reactor has been mapped out since the 1970s -- however, it would require the equivalent of 7 fission reactors to start the reaction before it can sustain itself, and materials including a very large 3-foot thick shield of lithium.
Startup power isn't really an issue. The real problem is that producing fusion isn't as simple as building a big donut and watching it go. Fusion ignition is harder than anyone thought 30 years ago, and the engineering problems involved with building a useful fusion reactor are orders of magnitude harder that we'd thought as well. Progress is (slowly) being made, but it's going to be a while, and it's *not* going to be cheap.
In summary, I'd suggest doing a bit more reading about fusion and power generation in general before extolling it's virtues as a cure-all.
Beams are a concern, and lifetime.
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it's too bad all these little clean energy projects can't somehow pool their resources into building a few orbital solar satellites.
While solar energy is a very promising option, there are a couple of catches that make it less ideal than advertised:
Beam intensity is high enough to cause problems.
If your beam intensity is less than, say, the average intensity of sunlight, you might as well build photovoltaics or a solar heat engine on the ground, and save the cost of a satellite and receiving station. If your beam intensity is large enough to be useful (many times the intensity of sunlight), then it will cook birds that fly through it, muck royally with local weather (maybe even to the point of starting a local hurricane), and so forth. While these drawbacks aren't catastrophic, they have to be planned for.
There is no danger of the beam wandering and frying the landscape. It's generated by a host of phase-locked emitters - synced to a transmitter in the middle of the receiving patch. No transmitter to sync to, and the emitters on random phases send energy in all directions, and most of it would have a hard time hitting *earth*, much less your backyard....OTOH, a rogue receiving beacon could really ruin a city's day.
Working lifetime of the satellite will be short, and revenues low.
Not horribly short, but you're going to have to amortize the cost of the satellite over a decade or two before something wears out or micrometeorites turn your panels/mirrors into confetti. A solar power satellite costs a _lot_ to lift, and power is cheap. My own back-of-the-envelope calculations suggest it costing 10 times more to lift than would be generated from electricity sales over a decade even with very favourable assumptions (100 W wall-plug output per kg of satellite, $10,000/kg to build _and_ launch, $0.10/kw*hr sale price of the electricity).
In summary, solar power will need several technological breakthroughs (or an order of magnitude increase in terrestrial power cost) before being competitive.
The breakthroughs are on the horizon, though. High-efficiency photovoltaic cells are coming on to the market, and thin-film cells can already be bought over the counter. Combine this with aluminized mylar concentrating mirrors, and you might have a satellite cheap enough to lift.
My money's still on fusion, though.
Dams don't change world water levels.
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· Score: 5, Informative
What kind of environmental concerns will be raised about this? I remember the project in Canada or whatever (name slips me right now, some big bay) that was being considered for damming to produce tidal power. However, because of the amount of water involved, it would change water levels all over the world.
Um, no.
The tide is actually a huge double-lobed bulge around the whole planet. To grossly simplify, two quarters of the planet have higher than normal water levels, and the other two have lower than normal.
Even if you built dams around all continents, the amount of water you'd trap would be about 0.1% of the surface area of the ocean, for a sea level change of one thousandth the height of the _dam_ (not the ocean). This is truly miniscule.
The real problem with dams is that when you build one, you flood a large region of land behind it. For areas that wouldn't normally be flooded (e.g. with hydroelectric projects), this causes environmental upset, and leaches all sorts of crud out of the rocks and soil far faster than rain leaching would (so you get a large spike in, say, mercury levels for a few years). This is unpopular.
Tidal areas are already flooded regularly, so the effects are far less drastic there. All you end up doing is making it very difficult for marine creatures to reach the shore (bad if you built in something like a turtle breeding ground), and change with the timing of the tide cycle (you need to drain the dam when the ocean is near the low mark and fill it when it's near the high mark to generate power, meaning a much more abrubt change in water level for the beach).
If there are any nearby planets with heavier elements and some range of chemistry, perhaps they could support life forms that derive their principal source of energy from such the magnetar's field.
This is an interesting thought. However, in this case, they (and the planet) would likely be boiled to vapour by the x- and gamma-ray bursts that let us know about the star's magnetic field in the first place.
Magnetic effects around gas giants, while far, far weaker, might still be strong enough to play a role in the evolution of any creatures on/in gas giant moons, though.
For a couple of interesting sci-fi books about life in and around neutron stars, check out "The Integral Trees"/"The Smoke Ring", by Larry Niven, and "Dragon's Egg", by Robert Forward.
And that makes me the perfect candidate to post here. Seriously though, one would think that a neutron star's magnetic field would extend well past the distance from the moon to the Earth.
"Extending" and "being able to suck change out of pockets and slow down locomotives" are two very different things.
Dipole magnetic fields drop off with the cube of distance, so on the surface of the neutron star (about 80,000 times closer), it would be strong enough to produce very exotic effects.
First of all, it doesn't have to be completely self-sufficient, it only has to be more self-sufficient. Anything it can do to reduce the amount of mass you have to lift is good.
This does not "make the space program profitable". This doesn't even make the space station you propose to build profitable. Cut supply costs by some small amount on a station that costs twice as much to build, or by a factor of two on a station that costs a hundred times as much? Either way, you're still paying *more*.
Second; industry. We should be (for example) actually building things in space instead of lifting them. Satellites are the prime example, since a fair number of them are launched now. Building them in orbit obviously saves money, all you have to do is maneuver them into position. You seem to assume that industry would not put up more satellites if the cost decreased; I disagree.
A satellite is a complex, specialized piece of equipment. It draws on a truly vast and diverse set of industries to build. You can't put all of those into space without needing a million tonne station, and putting only some of them into space gains nothing - you still have to supply most of your material from earth.
Secondly, if anything, industry demand for satellites has _decreased_. All of the constellation projects from the 1990s flopped spectacularly from the twin onslaught of cellular service proliferation (providing voice and data connections to most of the moving-user market) and improvements in fiber technology (we have network of fiber with a ludicrously high bandwidth linking all continents; the limiting factor is the routing electronics, not the linkages). There is no economic reason to route communications through satellites for anything but niche markets. The money is in ground-based communication.
The other main satellite use is remote sensing. I'd argue that the market for this is saturated already.
What satellites would companies put _up_?
It is not cost-effective to build large structures in space (including the ISS) without actually doing the mining in space. We should be taking up only things which cannot reasonably be built in orbit.
You are overlooking the cost of building the mining and manufacturing facilities needed to supply space construction. These are _huge_. Unless you _know_ you'll be building million tonne space stations, a mining facility costs more than just lifting materials from Earth.
You are also still assuming that an economic reason for large space construction exists at all. There is no industrial process for which there is significant demand that can be done in space that cannot be done more cheaply on earth (if you disagree - find one). There is no other profitable venture that anyone's been able to think of and make a good business case for that requires large-scale orbital construction. Vague noise has been made about ultra-pure crystals, exotic alloys, and so forth, but nobody's been able to produce a business case for these. Towing in an asteroid sounds like a great idea, but would only be useful if you needed the material in orbit - which we don't, at the moment. Selling to earth would be unlikely to be profitable vs. terrestrial mining operations, when you factor in the costs of towing the asteroid back.
To clarify once again - I love the idea of space exploration, and I hope we keep doing it. I just have no illusions about it being profitable any time in the near or medium-term future.
You could make the space program immediately profitable by putting up a real space station.
How?
Such a station could certainly be built, but how would it generate enough revenue to even pay for its day to day operating and resupply costs, let alone its construction?
All proposals for large-scale space projects that are supposed to be profitable assume that there's a very large market for space-based facilities (large enough to make the amortized cost of the construction and upkeep lower than the cost of providing the needed services from the ground).
Given that industry has no pressing need to send anything more than a few satellites into space, where's the demand? You're not going to get enough tourists to pay for a $10 trillion "real" station.
In order to have a really useful space station, something that doesn't have an insanely high operating cost, it must be large.
Anything smaller than a million tonnes won't be self-sufficient. Any large station we'd build any time soon would be *more* expensive than a small station.
NASA, stop throwing away booster tanks; Take them to the ISS and duct tape them together if you have to. They're useful.
They also have mass, which means significantly less payload if you spend the extra effort to lift them to orbit instead of letting them drop. Some of the effort's already been spent by jettison time, but not all of it by a long shot.
In summary, lifting the tanks isn't free. You might as well lift something more useful instead.
I don't know Columbus, this new world thing is cool and all, but, we have so many problems here in Spain...Shouldn't we solve those first? I mean I have no problem with explorer playing with the crown's money(peoples' taxes), but shouldn't the aristocrocy (and the people) get something out of it as well?
Columbus's trip actually had a justifiable business purpose - he was looking for a more economical trade route to India (hence the whole "indians" misnomer that's plagued us ever since). My understanding - which may be incorrect on a few points - is that it was well-known by the aristocracy that the earth was round (and so that such a trip was theoretically possible), but it was thought that the ships of the time wouldn't be able to make such a long trip (and they might have been right; Columbus only had to make it part way around before finding the New World).
Space exploration is blue-sky research. It does not have a strong business case for it. That doesn't mean it shouldn't happen; it just means that it's unlikely to ever be directly profitable.
Possible justifications include:
It stimulates high tech R&D, and spreads money around the high tech industries, which has direct and indirect spinoff benefits for the rest of the economy.
It will provide unforseen payoffs down the road (blue-sky research often does; remember the laser?).
People like it. If enough people think it's cool, it's worth spending money on even without a direct payback mechanism (it's the cultural equivalent of playing an arcade game).
I personally feel that it is in our best interests as a species to have a good understanding of space and to exist on multiple worlds (as our outlook for surviving in geologic time at any single location is not so good). This, in addition to it being cool and stimulating R&D, justifies it as far as I'm concerned. YMMV.
PR, but what's the use? Detailed pics of Saturn and rings, yay, but nothing we don't have. Although, the huygens probe actually looks useful, I think NASA should be more ambitious.
Pretty pictures of Saturn are the least of what's coming back. Go to the mission objectives page for the probe to see all of the experiments that will be done.
What, exactly, do you _want_ them to do? Bear in mind that sending humans *anywhere* costs at least 20 times what a probe with comparable scientific capabilities costs.
Don't bother decelerating. You want to stop a probe? Put a planet in the way. Just make sure you gather (and transmit) lots of data--really fast--on the way down. Or do a flyby. Or aim really carefully and put yourself into an orbit about some object of interest.
Unfortunately, planets or even stars won't help you much if you're going for a capture orbit. As a useful interstellar probe's velocity would be much higher than either's escape velocity, even a star would only cause a shallow deflection even if you were grazing the surface on flyby.
Flybys would still be neat, though. You'd have a few seconds to perform a close-up survey of an Earth-sized world, and not much more for a gas giant.
For major course corrections, we'd just need a handy neutron star...
I think I read that matter and antimatter, while being equal, are not. In our universe, it takes more animatter to destroy matter.
This is incorrect. Matter and antimatter annihilate 1:1. This is due to conservation rules - most of the quantum numbers have to sum to zero for annihilation to occur (positive and negative charge cancel, positive and negative lepton or baryon numbers have to cancel, etc.).
What you're probably thinking of is the asymmetry in matter and antimatter _production_. Certain reactions tend to produce matter more often than antimatter (which is why there's any matter in the universe at all).
This chip could be the start of something big in the Linux space as well. Think about it, we are now at a point where a few companies other than Intel are now poised to take the center stage in the next gen workstation, most notably AMD, Apple, and now IBM themselves.
Bear in mind that when IBM says "desktop workstation" they mean a $20k+ machine. Consumer desktop machines these aren't.
A lot of Intel's questionable moves (12K micro-ops instruction cache?) for the P4 were obviously not copied by AMD, and x86-64 seems to be the 64 bit desktop chip of the future.
The P4 has its flaws, but IMO cacheing decoded instructions isn't one of them. It shortens the pipeline, and paves the way for a true trace cache (cache of decoded basic blocks indexed by entry point; very handy for renaming and scheduling).
What is the efficiency of the process? A Peltier is around 5% efficient (very wasteful). These guys [powerchips.gi] are working on a similar device and are proclaiming efficiencies in the 70 to 80% range. Consider that a car engine is 15% efficient (approx) or a gas turbine is 30% efficient (approx).
Bear in mind that efficiency isn't necessarily symmetrical. If I'm trying to generate electricity from a 10:1 heat differential across a boundary, I can be up to 90% efficient ((Th-Tc)/Th). But if I'm trying to enforce a 10:1 heat gradient (i.e. keep the cold side cool), I can be at most 11% efficient (Tc/(Th-Tc)).
I'll still only believe PowerChips' numbers when I see a working device with that efficiency, of course.
The Apple guys then asked us what was the missing link preventing anyone from producing the contraption. The answer: "folding glass." Of course, we know now (and probably did then, just we didn't want to admit it) that the CPU's and graphics processors of the time would have choked on the OS needed to pull off the magic.
What I don't understand is why people think controlling your computer by talking to it is a good idea. Information transfer is more precise and (often) faster via keyboard (and that's ignoring mouse-based tasks that have no easy verbal-command equivalents).
Even on a PDA, I have a hard time believing that verbal commands are faster than stylus gestures. Perhaps as a very limited set of shortcuts...
Remember when touch-screens were going to be the new thing in input devices for desktop computers? Remember how ergonomics rapidly ripped that idea to shreds? Same deal. Use input modes only where they make sense.
[Another ObNitpick: They should have worried more about speech recognition, which is still only a partly-solved problem. A pair of rigid screens is an adequate, if annoying, solution to the folding problem.]
[Last ObNitpick: Good luck getting any computer that's not sapient to understand and appropriately react to naturally-spoken English, as opposed to rigidly defined commands.]
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I have to wonder what definition of "feasible" you're using that includes a project requiring "the present power output of all electrical plants on the planet over a decade" and more copper cable than has ever existed.
Something that we could conceivably do within 50 years if we decided we really wanted to (along the lines of the Manhattan Project).
As opposed to, say, building a Dyson Sphere or some other project that requires either vastly more resources than are available, or materials that we have no idea to produce.
So, I've got to ask ... how does this explain Venus?
It's actually Earth, and not Venus, that's the abberation. The only reason Earth doesn't have a Venus-like atmosphere is that the moon's influence agitated the atmosphere enough for most of it to be stripped off.
Venus has no moon, and so is stuck with a surface temperature at which lead gets mushy.
I used to think this to, but Titan has even less gravity than Mars yet keeps an atmosphere that is about 50% thicker than Earths.
Titan's also a lot colder than Mars.
The criterion for keeping an atmosphere, if I remember correctly, is for the mean velocity of gas molecules at the ambient temperature to be less than 10% of escape velocity. That keeps the fraction of molecules _at_ escape velocity low enough for evaporation to be negligible.
So, a colder world can get away with a shallower gravity well.
For a lark, I did the calculations for artificially imposing a magnetic field if the Earth ever lost its own.
:).
It turns out to be feasible even today, though horribly, horribly expensive. You'd build a mesh of copper cables around the equator (or superconducting, but copper's losses aren't that bad for this). Then you'd slowly ramp up the current until you have a magnetic field comparable in strength to today's.
Ramping up would be slow because of inductive power storage. The current loop and associated magnetic field store a *vast* amount of energy, all of which needs to be provided in order to bring the field up to strength. The present power output of all electrical plants on the planet over a decade or so would do it, if I remember correctly, so this is feasible. The power cost to maintain the field, even with copper cables, is much lower; put, say, a 10% tax on electricity, and you've paid for the extra plants to feed the mesh.
You'd use a mesh instead of a single cable _because_ of the amount of stored energy. If you break the current path of an inductor, current flows anyways, arcing across the gap. This only dies down as resistive losses across the gap dissipate the power stored in the inductor. Think about this - all of the inductor's stored power is dissipated in one place (the break), and we're storing an awfully large amount of power in this current loop. If the loop was a single cable and this cable was broken, you'd get something in the range of a 10-gigaton yield at the point of breakage. A mesh provides many alternate current paths, so breaks from sabotage or just plain wear can be repaired safely (as long as you overspec the current rating enough to allow the other paths to safely take up the load).
A copper cable a hundred metres wide, or ten thousand one-metre cables, would do the trick. You might _have_ to use copper, too; even if you spread the cables out to make a more uniform field near the Earth's surface, field strength near each wire would be much greater than the breakdown point of most superconductors.
We'd probably never bother doing this, but it's a fun thought experiment
"Dr Paul Murdin, of the Institute of Astronomy, Cambridge. 'On Mars, when its magnetic field failed permanently billions of years ago, it led to its atmosphere being boiled off."
.. steady on there Dr.Murdin! That's quite a brave thing to say as if it's a fact. That's just on theory, and an interesting one to, but you cannot prove this yet. I'm sure there are lots of other reasons why Mars atmosphere is the way it is now.
Whoa
If I understand correcty, the accepted one is that Mars's gravity well is too shallow to hold on to an atmosphere of anything lighter than carbon dioxide over geologic time (which among other things means that any terraforming won't be permanent, and that we aren't likely to find *much* water underground).
Arh! I think it will make some lovely daytime aurora, and generally play havoc with electrical equipment.
And greatly increase the mutation rate (solar wind smacking into the atmosphere will produce a fair bit of secondary radiation (X-rays)). While this won't do much beyond raising the cancer rate in any given generation, it will mean that a lot of genetic defects will start piling up over the years.
Not that I'm worried. By the time the field weakens enough for this to be an issue, we'll have enough medical expertise to rewrite our genomes as we see fit, so repairing damage won't be a problem. If we don't just put an artificially generated field in place to protect our electronics first (this is feasible, barely).
I'll also point out that no one really knows how the planet's magnetic field is generated.
Sure we do. It's from dynamo currents caused by convection in the (liquid) outer core.
Magnetic field flips happen when turbulence grows enough to disrupt these patterns briefly.
This is why Jupiter has a much stronger magnetic field than Earth (huge liquid metallic hydrogen layer, and a very powerful internal heat source), and why the moon has almost no magnetic field (no liquid core; the only field is the one that was "frozen in" when the moon first cooled).
Why in the world would you build a solar power sat from materials that are conventionally launched from Earth at $10,000 / kg?
Build them from lunar materials instead. The much shallower gravity well would bring your costs down to, at most, $100 / kg.
Plus the $1000,000/kg amortized cost of the lunar mining facility.
Mining of lunar material is only cost-effective if you expect to use millions of tonnes of it or more. Solar power satellites don't _need_ that much mass, especially now that thin-film photovoltaic cells are becoming practical.
If your beam intensity is large enough to be useful (many times the intensity of sunlight), then it will cook birds that fly through it
Only if you use wavelengths that are absorbed by the birds. That's not a reqirement, there is a whole spectrum available.
Birds will absorb anything from the low end of the microwave spectrum up through hard UV. Practical power relaying will likely be in the middle of the microwave range, as a collimated microwave beam is easy to produce efficiently and easy to convert back to electricity efficiently. Higher frequencies are hard on both counts, and lower frequencies are hard to drive at the required energies and have sloppier focusing.
In summary, all practical bands for us to use have this problem.
Have they ever managed to keep the plasma torus stable enough in a tokamak to use it? From what I understood, this was one of the main problems with research tokamaks, which was preventing the project from going further.
I've heard varying stories as to what the limiting problems are with current reactors (and all are probably true). However, an interesting development re. turbulence was made relatively recently. A group installed sensors and correction magnets on a tokamak, and suppressed the small irregularities in the containment field that turbulence produced. The result was much better confinement.
I don't have a link handy, but it might even have been on Slashdot many months ago.
My personal suspicion is that better materials will provide a big boost. I'm drooling over what nanotubes will do for anything that involves strong magnetic fields - they're the next best thing to superconducting, and their tensile strength means you can run an extremely strong magnet without worrying about it tearing itself apart. Both high density and long confinement times are much easier to achieve with a stronger magnetic field.
Isn't it strange that the publisher of Penthouse (Bob Guccione) is the only celebrity to ever endorse nuclear fusion, which is the only viable solution we are ever going to have to our insatiable lust for energy?
Funding for nuclear fusion is scarce, probably due to energy companies' opposition to anything that could possibly mean free energy.
Actually, this is wrong on pretty much all counts.
Fusion reactors are very big, and very expensive. This is why funding for fusion projects tends to get cut when economic belts are tightened. This is also why fusion energy will never be free - your plant has yearly costs (maintenance, and the amortized cost of building the plant over a reasonable payback window). These costs are passed directly on to the consumer, in the form of a nonzero price for electricity. The same happens with things like hydroelectric and fission power - the cost of the fuel required is low (or zero, for hydroelectric). You're paying for the plant/dam.
Lastly, the fact that electricity never will be free (due to the cost of facilities for producing/distributing it) means that a) there will be no magic free-energy solution, and b) our lust for energy had damned well *better* be sated, because otherwise we'll be awfully disappointed when we find out there isn't a free (beer) supply.
Oh, and if anything, I'd expect the big fossil fuel companies to be the strongest _supporters_ of alternative power sources. They're on top of the market now, and as soon as fossil fuel supplies wane and prices go up (or taxes on fossil fuel emissions rise), they'll want to be right there ready to sell the alternatives.
The process for creating a fusion reactor has been mapped out since the 1970s -- however, it would require the equivalent of 7 fission reactors to start the reaction before it can sustain itself, and materials including a very large 3-foot thick shield of lithium.
Startup power isn't really an issue. The real problem is that producing fusion isn't as simple as building a big donut and watching it go. Fusion ignition is harder than anyone thought 30 years ago, and the engineering problems involved with building a useful fusion reactor are orders of magnitude harder that we'd thought as well. Progress is (slowly) being made, but it's going to be a while, and it's *not* going to be cheap.
In summary, I'd suggest doing a bit more reading about fusion and power generation in general before extolling it's virtues as a cure-all.
While solar energy is a very promising option, there are a couple of catches that make it less ideal than advertised:
If your beam intensity is less than, say, the average intensity of sunlight, you might as well build photovoltaics or a solar heat engine on the ground, and save the cost of a satellite and receiving station. If your beam intensity is large enough to be useful (many times the intensity of sunlight), then it will cook birds that fly through it, muck royally with local weather (maybe even to the point of starting a local hurricane), and so forth. While these drawbacks aren't catastrophic, they have to be planned for.
There is no danger of the beam wandering and frying the landscape. It's generated by a host of phase-locked emitters - synced to a transmitter in the middle of the receiving patch. No transmitter to sync to, and the emitters on random phases send energy in all directions, and most of it would have a hard time hitting *earth*, much less your backyard.
Not horribly short, but you're going to have to amortize the cost of the satellite over a decade or two before something wears out or micrometeorites turn your panels/mirrors into confetti. A solar power satellite costs a _lot_ to lift, and power is cheap. My own back-of-the-envelope calculations suggest it costing 10 times more to lift than would be generated from electricity sales over a decade even with very favourable assumptions (100 W wall-plug output per kg of satellite, $10,000/kg to build _and_ launch, $0.10/kw*hr sale price of the electricity).
In summary, solar power will need several technological breakthroughs (or an order of magnitude increase in terrestrial power cost) before being competitive.
The breakthroughs are on the horizon, though. High-efficiency photovoltaic cells are coming on to the market, and thin-film cells can already be bought over the counter. Combine this with aluminized mylar concentrating mirrors, and you might have a satellite cheap enough to lift.
My money's still on fusion, though.
What kind of environmental concerns will be raised about this? I remember the project in Canada or whatever (name slips me right now, some big bay) that was being considered for damming to produce tidal power. However, because of the amount of water involved, it would change water levels all over the world.
Um, no.
The tide is actually a huge double-lobed bulge around the whole planet. To grossly simplify, two quarters of the planet have higher than normal water levels, and the other two have lower than normal.
Even if you built dams around all continents, the amount of water you'd trap would be about 0.1% of the surface area of the ocean, for a sea level change of one thousandth the height of the _dam_ (not the ocean). This is truly miniscule.
The real problem with dams is that when you build one, you flood a large region of land behind it. For areas that wouldn't normally be flooded (e.g. with hydroelectric projects), this causes environmental upset, and leaches all sorts of crud out of the rocks and soil far faster than rain leaching would (so you get a large spike in, say, mercury levels for a few years). This is unpopular.
Tidal areas are already flooded regularly, so the effects are far less drastic there. All you end up doing is making it very difficult for marine creatures to reach the shore (bad if you built in something like a turtle breeding ground), and change with the timing of the tide cycle (you need to drain the dam when the ocean is near the low mark and fill it when it's near the high mark to generate power, meaning a much more abrubt change in water level for the beach).
If there are any nearby planets with heavier elements and some range of chemistry, perhaps they could support life forms that derive their principal source of energy from such the magnetar's field.
This is an interesting thought. However, in this case, they (and the planet) would likely be boiled to vapour by the x- and gamma-ray bursts that let us know about the star's magnetic field in the first place.
Magnetic effects around gas giants, while far, far weaker, might still be strong enough to play a role in the evolution of any creatures on/in gas giant moons, though.
For a couple of interesting sci-fi books about life in and around neutron stars, check out "The Integral Trees"/"The Smoke Ring", by Larry Niven, and "Dragon's Egg", by Robert Forward.
And that makes me the perfect candidate to post here. Seriously though, one would think that a neutron star's magnetic field would extend well past the distance from the moon to the Earth.
"Extending" and "being able to suck change out of pockets and slow down locomotives" are two very different things.
Dipole magnetic fields drop off with the cube of distance, so on the surface of the neutron star (about 80,000 times closer), it would be strong enough to produce very exotic effects.
First of all, it doesn't have to be completely self-sufficient, it only has to be more self-sufficient. Anything it can do to reduce the amount of mass you have to lift is good.
This does not "make the space program profitable". This doesn't even make the space station you propose to build profitable. Cut supply costs by some small amount on a station that costs twice as much to build, or by a factor of two on a station that costs a hundred times as much? Either way, you're still paying *more*.
Second; industry. We should be (for example) actually building things in space instead of lifting them. Satellites are the prime example, since a fair number of them are launched now. Building them in orbit obviously saves money, all you have to do is maneuver them into position. You seem to assume that industry would not put up more satellites if the cost decreased; I disagree.
A satellite is a complex, specialized piece of equipment. It draws on a truly vast and diverse set of industries to build. You can't put all of those into space without needing a million tonne station, and putting only some of them into space gains nothing - you still have to supply most of your material from earth.
Secondly, if anything, industry demand for satellites has _decreased_. All of the constellation projects from the 1990s flopped spectacularly from the twin onslaught of cellular service proliferation (providing voice and data connections to most of the moving-user market) and improvements in fiber technology (we have network of fiber with a ludicrously high bandwidth linking all continents; the limiting factor is the routing electronics, not the linkages). There is no economic reason to route communications through satellites for anything but niche markets. The money is in ground-based communication.
The other main satellite use is remote sensing. I'd argue that the market for this is saturated already.
What satellites would companies put _up_?
It is not cost-effective to build large structures in space (including the ISS) without actually doing the mining in space. We should be taking up only things which cannot reasonably be built in orbit.
You are overlooking the cost of building the mining and manufacturing facilities needed to supply space construction. These are _huge_. Unless you _know_ you'll be building million tonne space stations, a mining facility costs more than just lifting materials from Earth.
You are also still assuming that an economic reason for large space construction exists at all. There is no industrial process for which there is significant demand that can be done in space that cannot be done more cheaply on earth (if you disagree - find one). There is no other profitable venture that anyone's been able to think of and make a good business case for that requires large-scale orbital construction. Vague noise has been made about ultra-pure crystals, exotic alloys, and so forth, but nobody's been able to produce a business case for these. Towing in an asteroid sounds like a great idea, but would only be useful if you needed the material in orbit - which we don't, at the moment. Selling to earth would be unlikely to be profitable vs. terrestrial mining operations, when you factor in the costs of towing the asteroid back.
To clarify once again - I love the idea of space exploration, and I hope we keep doing it. I just have no illusions about it being profitable any time in the near or medium-term future.
1. sail to India directly.
;).
2. find new world instead.
3. lose one ship.
4. Another mutinies and leaves.
5. ???
6. profit!
This nicely demonstrates why even something you can make a business case for won't necessarily turn a profit
You could make the space program immediately profitable by putting up a real space station.
How?
Such a station could certainly be built, but how would it generate enough revenue to even pay for its day to day operating and resupply costs, let alone its construction?
All proposals for large-scale space projects that are supposed to be profitable assume that there's a very large market for space-based facilities (large enough to make the amortized cost of the construction and upkeep lower than the cost of providing the needed services from the ground).
Given that industry has no pressing need to send anything more than a few satellites into space, where's the demand? You're not going to get enough tourists to pay for a $10 trillion "real" station.
In order to have a really useful space station, something that doesn't have an insanely high operating cost, it must be large.
Anything smaller than a million tonnes won't be self-sufficient. Any large station we'd build any time soon would be *more* expensive than a small station.
NASA, stop throwing away booster tanks; Take them to the ISS and duct tape them together if you have to. They're useful.
They also have mass, which means significantly less payload if you spend the extra effort to lift them to orbit instead of letting them drop. Some of the effort's already been spent by jettison time, but not all of it by a long shot.
In summary, lifting the tanks isn't free. You might as well lift something more useful instead.
Columbus's trip actually had a justifiable business purpose - he was looking for a more economical trade route to India (hence the whole "indians" misnomer that's plagued us ever since). My understanding - which may be incorrect on a few points - is that it was well-known by the aristocracy that the earth was round (and so that such a trip was theoretically possible), but it was thought that the ships of the time wouldn't be able to make such a long trip (and they might have been right; Columbus only had to make it part way around before finding the New World).
Space exploration is blue-sky research. It does not have a strong business case for it. That doesn't mean it shouldn't happen; it just means that it's unlikely to ever be directly profitable.
Possible justifications include:
I personally feel that it is in our best interests as a species to have a good understanding of space and to exist on multiple worlds (as our outlook for surviving in geologic time at any single location is not so good). This, in addition to it being cool and stimulating R&D, justifies it as far as I'm concerned. YMMV.
PR, but what's the use? Detailed pics of Saturn and rings, yay, but nothing we don't have. Although, the huygens probe actually looks useful, I think NASA should be more ambitious.
Pretty pictures of Saturn are the least of what's coming back. Go to the mission objectives page for the probe to see all of the experiments that will be done.
What, exactly, do you _want_ them to do? Bear in mind that sending humans *anywhere* costs at least 20 times what a probe with comparable scientific capabilities costs.
Don't bother decelerating. You want to stop a probe? Put a planet in the way. Just make sure you gather (and transmit) lots of data--really fast--on the way down. Or do a flyby. Or aim really carefully and put yourself into an orbit about some object of interest.
Unfortunately, planets or even stars won't help you much if you're going for a capture orbit. As a useful interstellar probe's velocity would be much higher than either's escape velocity, even a star would only cause a shallow deflection even if you were grazing the surface on flyby.
Flybys would still be neat, though. You'd have a few seconds to perform a close-up survey of an Earth-sized world, and not much more for a gas giant.
For major course corrections, we'd just need a handy neutron star...
I think I read that matter and antimatter, while being equal, are not. In our universe, it takes more animatter to destroy matter.
This is incorrect. Matter and antimatter annihilate 1:1. This is due to conservation rules - most of the quantum numbers have to sum to zero for annihilation to occur (positive and negative charge cancel, positive and negative lepton or baryon numbers have to cancel, etc.).
What you're probably thinking of is the asymmetry in matter and antimatter _production_. Certain reactions tend to produce matter more often than antimatter (which is why there's any matter in the universe at all).
This chip could be the start of something big in the Linux space as well. Think about it, we are now at a point where a few companies other than Intel are now poised to take the center stage in the next gen workstation, most notably AMD, Apple, and now IBM themselves.
Bear in mind that when IBM says "desktop workstation" they mean a $20k+ machine. Consumer desktop machines these aren't.
A lot of Intel's questionable moves (12K micro-ops instruction cache?) for the P4 were obviously not copied by AMD, and x86-64 seems to be the 64 bit desktop chip of the future.
The P4 has its flaws, but IMO cacheing decoded instructions isn't one of them. It shortens the pipeline, and paves the way for a true trace cache (cache of decoded basic blocks indexed by entry point; very handy for renaming and scheduling).
What is the efficiency of the process? A Peltier is around 5% efficient (very wasteful). These guys [powerchips.gi] are working on a similar device and are proclaiming efficiencies in the 70 to 80% range. Consider that a car engine is 15% efficient (approx) or a gas turbine is 30% efficient (approx).
Bear in mind that efficiency isn't necessarily symmetrical. If I'm trying to generate electricity from a 10:1 heat differential across a boundary, I can be up to 90% efficient ((Th-Tc)/Th). But if I'm trying to enforce a 10:1 heat gradient (i.e. keep the cold side cool), I can be at most 11% efficient (Tc/(Th-Tc)).
I'll still only believe PowerChips' numbers when I see a working device with that efficiency, of course.
The Apple guys then asked us what was the missing link preventing anyone from producing the contraption. The answer: "folding glass." Of course, we know now (and probably did then, just we didn't want to admit it) that the CPU's and graphics processors of the time would have choked on the OS needed to pull off the magic.
What I don't understand is why people think controlling your computer by talking to it is a good idea. Information transfer is more precise and (often) faster via keyboard (and that's ignoring mouse-based tasks that have no easy verbal-command equivalents).
Even on a PDA, I have a hard time believing that verbal commands are faster than stylus gestures. Perhaps as a very limited set of shortcuts...
Remember when touch-screens were going to be the new thing in input devices for desktop computers? Remember how ergonomics rapidly ripped that idea to shreds? Same deal. Use input modes only where they make sense.
[Another ObNitpick: They should have worried more about speech recognition, which is still only a partly-solved problem. A pair of rigid screens is an adequate, if annoying, solution to the folding problem.]
[Last ObNitpick: Good luck getting any computer that's not sapient to understand and appropriately react to naturally-spoken English, as opposed to rigidly defined commands.]