Re:so, you people want to build a gun eh?
on
Homemade Gauss Gun
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· Score: 1
Dude, you might want to check you facts before insulting someone. You are wrong on so many counts. First, 2000m/s over 3m is NOT hundreds of thousands of Gs, it's roughly 65G.
Actually this is exactly what has happened, is happening, and will continue to happen around 3 mile island - fish are being discovered with very strange mutations such as 2 heads.
Considering that the radiation exposure around TMI from the accident was much less than the dose the organisms there are naturally exposed to, I can conclude that either (1) your statement is bullshit, or (2) the rate of such deformations there is no higher than elsewhere, or (3) the cause is something entirely different, such as chemical pollution.
I'm not going to lie, I don't really know Lisp, I kinda of understand the basics of the syntax and that's about it. I'm assuming it's based on reverse polish notation or something. Is there a reason for this?
The reason is that Lisp programs are Lisp data structures. This is the foundation on which Lisp's incredibly cool macro system is based -- macros in Lisp can perform arbitrary computations
on the program tree, not just do simple and/or awkward textual substitutions.
It's also not any harder to type or understand
than more conventional syntax, once you get used to it. Don't let the shock of the unusual turn you off.
If a commercial compiler did worse than gcc on a platform gcc supported well, it would rapidly cease to exist. So any surviving commercial compilers must have better performance.
This technology is a good example of NASA's insistence on developing unnecessarily complex technology. Rockets are perfectly adequate for launching into orbit; Maglev systems, and particularly maglev coupled with airbreathing systems, are fancy technology for its own sake.
A properly implemented rocket system can get launch costs below the $1000/lb claimed for this system. Heck, the Russians can get below that with expendable rockets!
Recycling of plutonium from spent fuel has turned out to be grossly uneconomical, especially now when natural uranium is cheap. Don't let Club of Rome-type doomsters make you think that uranium scarce.
There *is* only so much uranium, but there's a whole lot of solar fusion to go around.
There's enough uranium in the ocean to supply the world's energy demand with a once-through fuel cycle for about 1000 years -- and the Japanese have shown how to extract this uranium at what is probably an acceptable cost.
Sure, solar energy is abundant, but so is fission energy. After 1000 years, we can think about fission breeder reactors. With those, the uranium and thorium resources in the crust will still be unexhausted when the sun's aging makes the earth uninhabitable.
Evaporation might actually be desirable, since you could get back some of the heat as the water vapor condensed going up the stack. This would retard the cooling of the upgoing air as it expands.
An alternate scheme was proposed some years back: inject water at the top of the tower. Evaporation cools the air, which descends, driving wind turbines at the bottom. One could use sea water if necessary. In dry, hot areas this would let you avoid building that 20 km^2 greenhouse.
How exactly do you account for barrels upon barrels of nuclear waste? Many of which are no longer properly secured and are eroding, etc., etc.?
High level nuclear waste -- the stuff that comes out of commercial nuclear reactors -- is properly secured, and is most certainly not 'eroding'. (Reprocessing waste from military nuclear programs is more problematic, but that doesn't have anything to do with commercial nuclear power, where reprocessing doesn't make economic sense.)
Perhaps you are thinking of drums containing low level nuclear waste? This is stuff like contaminated clothing with trace amounts of radioactivity. It's not a significant hazard.
I might be wrong about this, but also seem to recall a certain nuke plant on Lake Erie polluting the water and making it impossible to eat nearly
1/2 of the fish in the lake.
Oh great. Instead of building our spacecraft components on Earth, where manufacturing is very cheap, we get to do it in space, where labor is going to be four or more orders of magnitude more expensive, there's no easy access to suppliers, and so on.
The cost of moving all this industry into space would dwarf the cost of something as simple as mining the moon. Unless space operations become *vastly* larger, the cost will exceed the savings over launching from Earth. Also, remember that launch costs from Earth will decline as the size of the market increases, pushing out the point where space resources could be competitive.
*Maybe* something simple like mining volatiles for propellant could work, but even there it makes little sense at today's launch rates.
Platinum is not a rare-earth metal. In fact, the 'rare earths' (lanthanum, etc.) are not particularly rare.
Re:Moon composition, He3, and a reality check...
on
Mining On The Moon
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· Score: 1
> Launching the ore from the moon won't cost much b/c of the low gravity
Most of the cost of launch is labor cost. Labor will be incredibly expensive on the moon for the forseeable future. Combine that with the much higher cost of capital on the moon and we can conclude that launching from the moon will be far more expensive than launching from the Earth for the forseeable future.
It's a pity, but O'Neill just didn't get it right.
Holmium is not useless -- it is used in field shaping elements in very high strength magnets.
Do your research with Google next time.
Re:No. They are already abundant down here.
on
Mining On The Moon
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· Score: 1
Neither titanium nor tantalum are rare-earth metals.
BTW, the main use of titanium is in paint. Titanium dioxide, when purified, is the white pigment of choice. Raw titanium ore costs just pennies per pound; we're not going to be mining that in space for use on Earth.
Re:Could fuel further research in better propulsio
on
Mining On The Moon
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· Score: 1
Actually, chemical propulsion is highly efficient. Rockets are the most efficient heat engines ever built. The problem is that launchers are expensive, but this is because they currently require standing armies of workers and/or they throw away expensive hardware. Propellant cost itself is down in the noise.
Controlled thermonuclear fusion was achieved by Philo Farnsworth in 1967 in the ITT labs.
Nonsense, if you mean more fusion energy
out that energy in to the system.
If you mean fusion reactions were produced, then that was done in the 1930s using accelerators
on fixed targets. That can't reach breakeven,
but then neither did Farnsworth.
You're argument ist totally flawed. Plutoniom is so toxic, that it'll kill you by physiological means before the radiation has even gotten a chance to harm you.
This is bullshit. Plutonium's chemical toxicity is not terribly high. The high lethality so often mentioned is due to radiation-induced cancer.
Changing from a high-energy fuel like gasoline to a low(er)-energy fuel like hydrogen just means that you are going to have to carry proportionally more fuel.
Hydrogen has more energy per mass than hydrocarbons. It just requires larger tanks.
And what's the easiest way to make hydrogen gas? Electricity!
Why do so many people repeat this falsehood? The easiest way to make hydrogen is by thermochemical processes starting with natural gas, coal, or other organic compounds. That's how the very large amounts of hydrogen produced industrially are made today.
Electricity would have to drop to perhaps 1 cent per kWh for electrolytic hydrogen to begin to be competitive with these sources.
Slashdot Mirror
You're off by a factor of 1000.
Considering that the radiation exposure around TMI from the accident was much less than the dose the organisms there are naturally exposed to, I can conclude that either (1) your statement is bullshit, or (2) the rate of such deformations there is no higher than elsewhere, or (3) the cause is something entirely different, such as chemical pollution.
The reason is that Lisp programs are Lisp data structures. This is the foundation on which Lisp's incredibly cool macro system is based -- macros in Lisp can perform arbitrary computations on the program tree, not just do simple and/or awkward textual substitutions. It's also not any harder to type or understand than more conventional syntax, once you get used to it. Don't let the shock of the unusual turn you off.
If a commercial compiler did worse than gcc on a platform gcc supported well, it would rapidly cease to exist. So any surviving commercial compilers must have better performance.
Actually, the hydrogen in rocket fuel is produced directly from natural gas, not by electrolysis.
Given that rockets use a large portion of their fuel before clearing the tower (a quarter/half of their fuel, something like that),
This is simply wrong.
This technology is a good example of NASA's insistence on developing unnecessarily complex technology. Rockets are perfectly adequate for launching into orbit; Maglev systems, and particularly maglev coupled with airbreathing systems, are fancy technology for its own sake.
A properly implemented rocket system can get launch costs below the $1000/lb claimed for this system. Heck, the Russians can get below that with expendable rockets!
Recycling of plutonium from spent fuel has turned out to be grossly uneconomical, especially now when natural uranium is cheap. Don't let Club of Rome-type doomsters make you think that uranium scarce.
There *is* only so much uranium, but there's a whole lot of solar fusion to go around.
There's enough uranium in the ocean to supply the world's energy demand with a once-through fuel cycle for about 1000 years -- and the Japanese have shown how to extract this uranium at what is probably an acceptable cost.
Sure, solar energy is abundant, but so is fission energy. After 1000 years, we can think about fission breeder reactors. With those, the uranium and thorium resources in the crust will still be unexhausted when the sun's aging makes the earth uninhabitable.
Evaporation might actually be desirable, since you could get back some of the heat as the water vapor condensed going up the stack. This would retard the cooling of the upgoing air as it expands.
An alternate scheme was proposed some years back: inject water at the top of the tower. Evaporation cools the air, which descends, driving wind turbines at the bottom. One could use sea water if necessary. In dry, hot areas this would let you avoid building that 20 km^2 greenhouse.
How exactly do you account for barrels upon barrels of nuclear waste? Many of which are no longer properly secured and are eroding, etc., etc.?
High level nuclear waste -- the stuff that comes out of commercial nuclear reactors -- is properly secured, and is most certainly not 'eroding'. (Reprocessing waste from military nuclear programs is more problematic, but that doesn't have anything to do with commercial nuclear power, where reprocessing doesn't make economic sense.)
Perhaps you are thinking of drums containing low level nuclear waste? This is stuff like contaminated clothing with trace amounts of radioactivity. It's not a significant hazard.
1/2 of the fish in the lake.
You're wrong about that.
Oh great. Instead of building our spacecraft components on Earth, where manufacturing is very cheap, we get to do it in space, where labor is going to be four or more orders of magnitude more expensive, there's no easy access to suppliers, and so on.
The cost of moving all this industry into space would dwarf the cost of something as simple as mining the moon. Unless space operations become *vastly* larger, the cost will exceed the savings over launching from Earth. Also, remember that launch costs from Earth will decline as the size of the market increases, pushing out the point where space resources could be competitive.
*Maybe* something simple like mining volatiles for propellant could work, but even there it makes little sense at today's launch rates.
Platinum is not a rare-earth metal. In fact, the 'rare earths' (lanthanum, etc.) are not particularly rare.
> Launching the ore from the moon won't cost much b/c of the low gravity
Most of the cost of launch is labor cost. Labor will be incredibly expensive on the moon for the forseeable future. Combine that with the much higher cost of capital on the moon and we can conclude that launching from the moon will be far more expensive than launching from the Earth for the forseeable future.
It's a pity, but O'Neill just didn't get it right.
> The difference is that the moon's silicon and
> oxygen isn't at the bottom of earth's gravity
> well.
... which happens to be where 100% of the paying customers are located.
Holmium is not useless -- it is used in field shaping elements in very high strength magnets.
Do your research with Google next time.
Neither titanium nor tantalum are rare-earth metals.
BTW, the main use of titanium is in paint. Titanium dioxide, when purified, is the white pigment of choice. Raw titanium ore costs just pennies per pound; we're not going to be mining that in space for use on Earth.
Actually, chemical propulsion is highly efficient. Rockets are the most efficient heat engines ever built. The problem is that launchers are expensive, but this is because they currently require standing armies of workers and/or they throw away expensive hardware. Propellant cost itself is down in the noise.
Nonsense, if you mean more fusion energy out that energy in to the system.
If you mean fusion reactions were produced, then that was done in the 1930s using accelerators on fixed targets. That can't reach breakeven, but then neither did Farnsworth.
This is bullshit. Plutonium's chemical toxicity is not terribly high. The high lethality so often mentioned is due to radiation-induced cancer.
Hydrogen's specific energy is much higher than jet fuel. Its volumetric energy density is lower.
Hydrogen has more energy per mass than hydrocarbons. It just requires larger tanks.
Why do so many people repeat this falsehood? The easiest way to make hydrogen is by thermochemical processes starting with natural gas, coal, or other organic compounds. That's how the very large amounts of hydrogen produced industrially are made today.
Electricity would have to drop to perhaps 1 cent per kWh for electrolytic hydrogen to begin to be competitive with these sources.
Please explain how the use of hydrogen as a fuel would "decrease the dependancy on foriegn oil"?
It's made from natural gas or coal, silly.