I'm greatly looking forward to seeing your solution for keeping vital components at acceptable temperatures without any power.
polonium-210?
Actually, Plutonium 239. The Mars Science Lab uses a General Purpose Heat Source (a radioisotope brick) to both generate power using thermoelectrics, and as a source of heat during the martian night. A pumped fluid loop is used to cool the electronics during the day, and heat them at night.
When heating is needed, some of the fluid is diverted to two hot plates around the general purpose heat source.
Even water by itself has more hydrogen per volume than liquid hydrogen does. At 20 K, liquid hydrogen has a density of only 0.071 grams/ml. (Water has a density of 1 gram/ml, so has a hydrogen density of 0.11 grams/ml.) IANAP (I am not a physicist), but I've been told that the very low density is caused by quantum mechanical effects. In fact, liquid hydrogen is so light, that under high enough pressure, you can get is to float above gaseous helium.
"The Health Hazards of Not Going Nuclear", by Petr Beckman. Out of print and somewhat dated (about 20 years old), but goes into the different problems with coal versus nuclear power. Multiple copies available at abebooks.com
Interesting, I had also thought that it was the paint.
Actually, the most interesting thing is that most of the passengers were unharmed, and walked off the ship, because it settled fairly slowly (when was the last time that most of the passengers survived a major air crash?)
The temperature drop through the solid is too high
"That's a pretty one-sided assesment. Solid condutors certainly DO work, the only question for a designer would have to be 'how much material will be needed to conduct enough heat over ??inches to the outside of the case'"
First, I'm talking about the high power chips discussed above, with 4 times the power of current chips, or about 300 Watts. While it theoretically may be possible to use a solid conductor to transport the heat, it not economically practical, especially since you are talking about using natural convection in the air.
First, the heat flux off of the chip is around 300 W/cm^2. Assuming copper as your solid conductor, there is an 80 degree C drop through a 1/4 inch of copper at this heat flux. This means that your chip has to be well over 100 C (ignoring the temperature drop between the outer surface and the air). Copper is the best reasonably cheap conductor (there are other, very expensive composites) so the temperature drop is too high.
In addition, since you are using natural conduction, you need a much larger area to dump the heat, on the order of 100 times more, so your solid conductor must spread out to a larger area. This means a great deal of metal - it's a lot cheaper to use a heat pipe or other two-phase device to spread the heat, and conduct it away, since a heat pipe can have an effective conductivity that 1000 times greater than copper.
No, they're not heat pipes. In a heat pipe, you are vaporizing liquid (cooling the chip with the latent heat of the fluid). Vapor travels to a condenser, where heat is removed. The liquid is then returned to the chip.
In this case, you have a two-phase flow of vapor and liquid from the evaporator to the condenser. Some of the heat is removed by the vapor, the rest by raising the temperature of the liquid.
From the article, you can't tell if this would be better or worse than a heat pipe. Going to micro-channels allows you to get much higher heat transfer coefficients than in a more normal sized channel, but I think that a heat pipe could be designed for this application.
You can dump the heat this way with a heat pipe, which has a very high thermal conductivity. In fact, some laptops use the method - take the heat from the cpu and dump it to the case. This works well for lower power consumption cases. I sure wouldn't want an exposed sink trying to dump several hundred watts - it would be like have several lightbulbs in your lap.
Solid conductors won't work. The temperature drop through the solid is too high, so you can't cool the chip to a low enough temperature.
As some one above said, the heat eventually gets dumped to the air. Think of this device as a heat flux transformer. It cools a very concentrated heat source, and spreads the heat to a much larger area, where it can be cooled with a fan. Air is a lousy heat transfer fluid, and it wouldn't be practical to cool the chip directly with air. This system lets you size the surface where the liquid is cooled so that the air can efficiently remove the heat.
It's harder to form bubbles with mercury. You need the bubbles in the heated micro-channels, to help create the density difference between the two legs that drives the flow. Mercury has a much higher thermal conductivity, so boiling tends to be suppressed (the heat conducts much better in a liquid metal than water)
Even if mercury was the perfect fluid, it would be unacceptable from an environmental standpoint, as pointed out by the posters above. We're talking about millions of these systems being disposed of in a few years, and no one would want to have to deal with the attack lawyers. Consider that many thermometers used to contain mercury - I don't even know if you can buy a new mercury thermometer.
Just like so many people only buy unencrypted DVDs? The DVD standard does not require CSS encryption... and yet... how many unencrypted DVDs do you know about? Any movies you would want to buy?
On the other hand, when I buy a DVD, I know that it will work in essentially any DVD player. The copy-protected CD's won't work in computer CDs, and some other CDs, such as car players.
When all CDs are copy protected, I can't buy any CDs at all - I don't have anything that would play them.
"They went looking through the "steam tables" and found that nobody had ever looked at the sub-atmospheric range of pressures, and had to derive all of the thermodynamic properties themselves"
That's funny, I have a copy of the ASME Steam Tables, copyright 1936, that goes down to 0.088 psi absolute pressure at 32 F, which is as low as it goes, unless you are dealing with ice.:)
"Technically you didn't say whether you agreed or disagreed with my opinion, so there is little I can respond with."
I was not commenting on whether the system works or not, but trying to address several erroneous assumptions that you made as to why a heat pipe couldn't cool the system. Obviously heat pipes work for cooling the system, Dell (and others) have been using them for over 5 years in laptops.
"What I was saying was that you can't cram something like this into such a small space and expect to achieve a magical balance where the fans are cooling the vapour in the coils so that it condenses back on the gently warm CPU."
It's not a magical balance. For a brief description of how heat pipes work, go to http://www.thermacore.com/hpt.htm. There are also technical papers on the site that go into more detail. The liquid doesn't condense gently on the CPU, if it did, the heat pipe would be working backwards, heating the cpu. The liquid evaporates from the cpu area, cooling the cpu. The resultant vapor travels to the condenser (by the fans), and condenses, supplying heat in this area. This heat is removed by the fans. The liquid doesn't drop back, it is pulled back by capillary forces.
"If the system gets too hot, there will be no condensation, and if the 2"x2" heat source isn't near the boiling point of the fluid, I don't think you can pull enough heat away from it."
You are thinking that there is a single boiling point for the liquid (water). The boiling temperature is strongly dependent on the pressure. For example, it is 0.006 atm. at 0.1 C, 1 atm at 100 C, and 15.4 atm at 200 C. The pressure in the heat pipe adjusts so that the boiling temperature is in the range required. For electronics cooling, the pressure is usually subatmospheric. For a heat pipe operating at 60 C, the pressure would be about 0.2 atmosphere, or about 3 psia. If the cpu gets hotter, the pressure (and temperature) of the heat pipe also increase, but the heat pipe doesn't stop working (in fact, in this temperature range, it generally transfer heat better as it gets hotter).
"These guys don't even seem to indicate that the 'radiator' needs to be in any particular orientation."
That's because a heat pipe, when properly designed, can operate in any orientation. Gravity doesn't return the liquid to the evaporator (next to the chip), capillary forces do. A simple wick design can use surface tension to return the liquid back for several inches against gravity , very complicated designs (not suited for electronics cooling) can return the liquid for ~ 3 meters against gravity.
"There doesn't seem to be any pump... they're relying on the thermal gradient to cause the vapourizing fluid to move to the cool side of the radiator and condense. It doesn't work that way. "
Heat pipes generally consist of a pipe, a working fluid, and a wick. They work by vaporizing a liquid at the evaporator (cooling the chip with the latent heat of vaporization) The vapor flows along the heat pipe until it reaches the condenser. The vapor condenses back to a liquid, releasing the latent heat. This heat is removed by fans or natural convection. The condensed lqiuid is then pulled back to the evaporator using some combination of gravitational forces and surface tension forces (similar to the way that a sponge can soak up water). No small opening is needed. Temperature differences in the vapor space of the heat pipe are very small, generally much less than a degree (The National Bureau of Standards uses heat pipes for generating temperatures in a region that are uniform to better than 1 milliKelvin)
"On the other hand, if your fluid vapourizes at 60C, it doesn't actually DO anything until the CPU reaches that temperature. "
Pure fluids don't vaporize at a single temperature. The boiling temperature depends on the pressure. The heat pipes contain a mixture of fluid and vapor. The temperature (and pressure) of the heat pipe adjust so that the heat pipe is at a temperature between the heat source (chip) and heat sink.
Its not so much the amount of heat, but the heat flux that can be a problem. You're generating less heat per transistor, but there are more transistors, and they've been squeezed into a smaller space. The heat flux off of some chips is getting into the 100 W/cm^2 range, where removing the heat requires careful thermal engineering.
Heat pipes have been used to cool laptops since the mid to late 90's. The heat pipe transfers the heat from the cpu to the shield around the bottom of the laptop (which is one reason that our laptop often does a good job of warming your lap). The advantage is that cooling fans can be eliminated, which prolongs battery life.
Most of the heat pipes used in electronics cooling have a copper envelope, copper wick, and use water as the working fluid (operating under a partial vacuum). The advantage is not that they are really fast (the velocity of the water vapor is on the order of meters/second) but that they are very nearly isothermal. (The temperature drop in the heat pipe is essentially negligible, with small temperature drops occurring due to the heat conduction through the copper walls and wicks). This allows you to transfer heat over relatively long distances before removing the heat.
A second advantage is that heat pipes can be used to reduce the heat flux. The heat flux (watt/cm^2) out of the chip is fairly high. On the other hand, air cooling is relativley inefficient, so a low heat flux is preferred. By using a larger condenser than evaporator, the heat flux can be adjusted to match the capacity of the cooling media. This will become more important in the future, as the heat flux from the chips continues to rise. Some experimental designs water designs have cooled several hundred W/cm^2, which is higher than chips should reach in the near future (high temperature heat pipes - have removed in excess of 50,000 W/cm^2)
The best introductory book is Heat Pipes, by Chiu, but it is out of print. Dunn and Reay have a reasonable book on heat pipes, but it is quite expensive (~ $100).
"Solid-state Peltier-effect coolers are much more promising. They actually refrigerate, they have no moving parts, and they don't make noise"
Peltier coolers are generally a bad idea, _unless_ the chip has to operate below the temperature of the cooling stream. The problem is that they are inefficient, i.e., you need 70 or 80 Watts of electric power to remove 10 watts of thermal power. All of the electric power supplied ends up as thermal power, so you now have to get rid of 8 times the heat that you originally had.
A great book for understanding thermal cooling issues is "Hot Air Rises and Heat Sinks" by Tony Kordyban (www.asme.org). He explains peltiers shouldn't normally be used, and explains electronics cooling is an easily understood and humourous fashion.
A lot of laptops use heat pipes to eliminate the fan (not for noise, but to increase battery life). The heat pipe transfers the heat to the RF shield at the bottom of the laptop, giving you a much larger area to dissipate the heat. Its the reason that many laptops get really warm your lap:)
Right. If the accident happened today, it would look a lot better than any of the recent jumbo jet crashes. Many of the passengers _walked_ off the Hindenburg.
The radio announcer was hysterical, making the disaster seem worse than it was. If it happened to a jet today, it would be viewed as miraculous that so many of the passengers survived.
Why not the Baen Free Library (www.baen.com). They have a number of free books available in HTML, Rich Text, Microsoft E-book, Palm, and rocket e-book.
The commentary on why they have the Free Library is also of interest to this discussion. Among other things, they feel that making some of an author's books available for free in electronic form will help sales (both sales of that book, by people that read the e-book and decide that they want a hard copy), as well as sales of other books by the author.
Baen is also offering webscriptions for their new books - $10 for the four books coming out in a given month, available before the hardcover comes out.
With hotmail, it seems you get spam when you open an account with a name that is short, or that has a common name, i.e., JohnSmith103. The spammer just keeps incrementing the number, not caring whether the name is valid or not.
I opened a hotmail account 3 months ago with an obscure name. I haven't used it anywhere, and have received no spam.
Depreciation is over a five(?)year period for computer equipment. When you make a large capital purchase, you're not allowed to subtract all of it from your current earnings before paying taxes. Instead, you reduce your earnings (and taxes) every month by a fraction of the original purchase price, until the item is fully depreciated.
If you switch to a monthly licence, then you can deduct that amount from your earnings in that month. There are reasons to dislike the monthly charges, but it probably doesn't affect your taxes very much.
Its not actually a problem with drilling through "hard rock", the formations are sedimentary, and many can be crumbled in your hand.
Drilling at an angle is desirable because you want to minimize the number of offshore platforms you require. You want a large number of equally spaced wells in the formation, however, A typical platform costs several billion dollars. With current technology, you start all of the wells under the platform, then angle them out to get good coverage in the oil formation.
There seem to be a number of problems with using this to drill for oil and gas, but combustion probably isn't a problem, since there is no oxygen.
There are two other potential problems that I see. The first is the high pressure underground. Oil companies typically use drilling mud which, in addition to cooling the bit and removing the cuttings, is weighted with additives (barite??) to increase the density. The density is controlled so that the hydrostatic pressure is higher than the pressure in the gas/oil reservoirs. This prevents blowouts, where the oil gushes to the surface (the gushers in the old movies) Oil companies hate this, because in addition to the problem of fires, you are wasteing the gas pressure that could be used to help produce additional oil. The laser process will have to supply the high pressure in some manner.
A second problem is damaging the well. Oil and gas are typically contained in sedimentary rock (NOT a liquid reservoir). In terms of flow properties, think of a massive brick saturated with oil - this is roughly what you are trying to produce oil from. Since the flow is radial to the well, damage right around the hole is the worst in terms of damaging the well. While its true that you can fracture the well to improve the production, this adds significant expense. (need to inject large quantities of liquid at high pressure to fracture the rock, as well as proppant (sand) to keep the fractures from closing back down).
Slashdot Mirror
I'm greatly looking forward to seeing your solution for keeping vital components at acceptable temperatures without any power.
i -final-paper-2005-01-28.pdf
polonium-210?
Actually, Plutonium 239. The Mars Science Lab uses a General Purpose Heat Source (a radioisotope brick) to both generate power using thermoelectrics, and as a source of heat during the martian night. A pumped fluid loop is used to cool the electronics during the day, and heat them at night.
When heating is needed, some of the fluid is diverted to two hot plates around the general purpose heat source.
A nice overview is "Mars Science Laboratory Thermal Control Architecture" which can be found at:
http://marstech.jpl.nasa.gov/publications/Bhandar
Even water by itself has more hydrogen per volume than liquid hydrogen does. At 20 K, liquid hydrogen has a density of only 0.071 grams/ml. (Water has a density of 1 gram/ml, so has a hydrogen density of 0.11 grams/ml.) IANAP (I am not a physicist), but I've been told that the very low density is caused by quantum mechanical effects. In fact, liquid hydrogen is so light, that under high enough pressure, you can get is to float above gaseous helium.
"The Health Hazards of Not Going Nuclear", by Petr Beckman. Out of print and somewhat dated (about 20 years old), but goes into the different problems with coal versus nuclear power. Multiple copies available at abebooks.com
Interesting, I had also thought that it was the paint.
Actually, the most interesting thing is that most of the passengers were unharmed, and walked off the ship, because it settled fairly slowly (when was the last time that most of the passengers survived a major air crash?)
The temperature drop through the solid is too high
"That's a pretty one-sided assesment. Solid condutors certainly DO work, the only question for a designer would have to be 'how much material will be needed to conduct enough heat over ??inches to the outside of the case'"
First, I'm talking about the high power chips discussed above, with 4 times the power of current chips, or about 300 Watts. While it theoretically may be possible to use a solid conductor to transport the heat, it not economically practical, especially since you are talking about using natural convection in the air.
First, the heat flux off of the chip is around 300 W/cm^2. Assuming copper as your solid conductor, there is an 80 degree C drop through a 1/4 inch of copper at this heat flux. This means that your chip has to be well over 100 C (ignoring the temperature drop between the outer surface and the air). Copper is the best reasonably cheap conductor (there are other, very expensive composites) so the temperature drop is too high.
In addition, since you are using natural conduction, you need a much larger area to dump the heat, on the order of 100 times more, so your solid conductor must spread out to a larger area. This means a great deal of metal - it's a lot cheaper to use a heat pipe or other two-phase device to spread the heat, and conduct it away, since a heat pipe can have an effective conductivity that 1000 times greater than copper.
No, they're not heat pipes. In a heat pipe, you are vaporizing liquid (cooling the chip with the latent heat of the fluid). Vapor travels to a condenser, where heat is removed. The liquid is then returned to the chip.
In this case, you have a two-phase flow of vapor and liquid from the evaporator to the condenser. Some of the heat is removed by the vapor, the rest by raising the temperature of the liquid.
From the article, you can't tell if this would be better or worse than a heat pipe. Going to micro-channels allows you to get much higher heat transfer coefficients than in a more normal sized channel, but I think that a heat pipe could be designed for this application.
You can dump the heat this way with a heat pipe, which has a very high thermal conductivity. In fact, some laptops use the method - take the heat from the cpu and dump it to the case. This works well for lower power consumption cases. I sure wouldn't want an exposed sink trying to dump several hundred watts - it would be like have several lightbulbs in your lap.
Solid conductors won't work. The temperature drop through the solid is too high, so you can't cool the chip to a low enough temperature.
As some one above said, the heat eventually gets dumped to the air. Think of this device as a heat flux transformer. It cools a very concentrated heat source, and spreads the heat to a much larger area, where it can be cooled with a fan. Air is a lousy heat transfer fluid, and it wouldn't be practical to cool the chip directly with air. This system lets you size the surface where the liquid is cooled so that the air can efficiently remove the heat.
It's harder to form bubbles with mercury. You need the bubbles in the heated micro-channels, to help create the density difference between the two legs that drives the flow. Mercury has a much higher thermal conductivity, so boiling tends to be suppressed (the heat conducts much better in a liquid metal than water)
Even if mercury was the perfect fluid, it would be unacceptable from an environmental standpoint, as pointed out by the posters above. We're talking about millions of these systems being disposed of in a few years, and no one would want to have to deal with the attack lawyers. Consider that many thermometers used to contain mercury - I don't even know if you can buy a new mercury thermometer.
On the insurance part: if you are young and single, or married and childless, life insurance is probably the last thing you need.
While you don't need life insurance, you'd better have disability insurance.
Just like so many people only buy unencrypted DVDs? The DVD standard does not require CSS encryption ... and yet ... how many unencrypted DVDs do you know about? Any movies you would want to buy?
On the other hand, when I buy a DVD, I know that it will work in essentially any DVD player. The copy-protected CD's won't work in computer CDs, and some other CDs, such as car players.
When all CDs are copy protected, I can't buy any CDs at all - I don't have anything that would play them.
www.cdaccess.com has Planescape Torment for about $20, or Planescape Torment, Fallout 2, and Baldurs Gate together for about $30.
"They went looking through the "steam tables" and found that nobody had ever looked at the sub-atmospheric range of pressures, and had to derive all of the thermodynamic properties themselves"
:)
That's funny, I have a copy of the ASME Steam Tables, copyright 1936, that goes down to 0.088 psi absolute pressure at 32 F, which is as low as it goes, unless you are dealing with ice.
"Technically you didn't say whether you agreed or disagreed with my opinion, so there is little I can respond with."
I was not commenting on whether the system works or not, but trying to address several erroneous assumptions that you made as to why a heat pipe couldn't cool the system. Obviously heat pipes work for cooling the system, Dell (and others) have been using them for over 5 years in laptops.
"What I was saying was that you can't cram something like this into such a small space and expect to achieve a magical balance where the fans are cooling the vapour in the coils so that it condenses back on the gently warm CPU."
It's not a magical balance. For a brief description of how heat pipes work, go to http://www.thermacore.com/hpt.htm. There are also technical papers on the site that go into more detail. The liquid doesn't condense gently on the CPU, if it did, the heat pipe would be working backwards, heating the cpu. The liquid evaporates from the cpu area, cooling the cpu. The resultant vapor travels to the condenser (by the fans), and condenses, supplying heat in this area. This heat is removed by the fans. The liquid doesn't drop back, it is pulled back by capillary forces.
"If the system gets too hot, there will be no condensation, and if the 2"x2" heat source isn't near the boiling point of the fluid, I don't think you can pull enough heat away from it."
You are thinking that there is a single boiling point for the liquid (water). The boiling temperature is strongly dependent on the pressure. For example, it is 0.006 atm. at 0.1 C, 1 atm at 100 C, and 15.4 atm at 200 C. The pressure in the heat pipe adjusts so that the boiling temperature is in the range required. For electronics cooling, the pressure is usually subatmospheric. For a heat pipe operating at 60 C, the pressure would be about 0.2 atmosphere, or about 3 psia. If the cpu gets hotter, the pressure (and temperature) of the heat pipe also increase, but the heat pipe doesn't stop working (in fact, in this temperature range, it generally transfer heat better as it gets hotter).
"These guys don't even seem to indicate that the 'radiator' needs to be in any particular orientation."
That's because a heat pipe, when properly designed, can operate in any orientation. Gravity doesn't return the liquid to the evaporator (next to the chip), capillary forces do. A simple wick design can use surface tension to return the liquid back for several inches against gravity , very complicated designs (not suited for electronics cooling) can return the liquid for ~ 3 meters against gravity.
"There doesn't seem to be any pump... they're relying on the thermal gradient to cause the vapourizing fluid to move to the cool side of the radiator and condense. It doesn't work that way. "
Heat pipes generally consist of a pipe, a working fluid, and a wick. They work by vaporizing a liquid at the evaporator (cooling the chip with the latent heat of vaporization) The vapor flows along the heat pipe until it reaches the condenser. The vapor condenses back to a liquid, releasing the latent heat. This heat is removed by fans or natural convection. The condensed lqiuid is then pulled back to the evaporator using some combination of gravitational forces and surface tension forces (similar to the way that a sponge can soak up water). No small opening is needed. Temperature differences in the vapor space of the heat pipe are very small, generally much less than a degree (The National Bureau of Standards uses heat pipes for generating temperatures in a region that are uniform to better than 1 milliKelvin)
"On the other hand, if your fluid vapourizes at 60C, it doesn't actually DO anything until the CPU reaches that temperature. "
Pure fluids don't vaporize at a single temperature. The boiling temperature depends on the pressure. The heat pipes contain a mixture of fluid and vapor. The temperature (and pressure) of the heat pipe adjust so that the heat pipe is at a temperature between the heat source (chip) and heat sink.
Its not so much the amount of heat, but the heat flux that can be a problem. You're generating less heat per transistor, but there are more transistors, and they've been squeezed into a smaller space. The heat flux off of some chips is getting into the 100 W/cm^2 range, where removing the heat requires careful thermal engineering.
Heat pipes have been used to cool laptops since the mid to late 90's. The heat pipe transfers the heat from the cpu to the shield around the bottom of the laptop (which is one reason that our laptop often does a good job of warming your lap). The advantage is that cooling fans can be eliminated, which prolongs battery life.
Most of the heat pipes used in electronics cooling have a copper envelope, copper wick, and use water as the working fluid (operating under a partial vacuum). The advantage is not that they are really fast (the velocity of the water vapor is on the order of meters/second) but that they are very nearly isothermal. (The temperature drop in the heat pipe is essentially negligible, with small temperature drops occurring due to the heat conduction through the copper walls and wicks). This allows you to transfer heat over relatively long distances before removing the heat.
A second advantage is that heat pipes can be used to reduce the heat flux. The heat flux (watt/cm^2) out of the chip is fairly high. On the other hand, air cooling is relativley inefficient, so a low heat flux is preferred. By using a larger condenser than evaporator, the heat flux can be adjusted to match the capacity of the cooling media. This will become more important in the future, as the heat flux from the chips continues to rise. Some experimental designs water designs have cooled several hundred W/cm^2, which is higher than chips should reach in the near future (high temperature heat pipes - have removed in excess of 50,000 W/cm^2)
The best introductory book is Heat Pipes, by Chiu, but it is out of print. Dunn and Reay have a reasonable book on heat pipes, but it is quite expensive (~ $100).
"Solid-state Peltier-effect coolers are much more promising. They actually refrigerate, they have no moving parts, and they don't make noise"
Peltier coolers are generally a bad idea, _unless_ the chip has to operate below the temperature of the cooling stream. The problem is that they are inefficient, i.e., you need 70 or 80 Watts of electric power to remove 10 watts of thermal power. All of the electric power supplied ends up as thermal power, so you now have to get rid of 8 times the heat that you originally had.
A great book for understanding thermal cooling issues is "Hot Air Rises and Heat Sinks" by Tony Kordyban (www.asme.org). He explains peltiers shouldn't normally be used, and explains electronics cooling is an easily understood and humourous fashion.
A lot of laptops use heat pipes to eliminate the fan (not for noise, but to increase battery life). The heat pipe transfers the heat to the RF shield at the bottom of the laptop, giving you a much larger area to dissipate the heat. Its the reason that many laptops get really warm your lap :)
Right. If the accident happened today, it would look a lot better than any of the recent jumbo jet crashes. Many of the passengers _walked_ off the Hindenburg.
The radio announcer was hysterical, making the disaster seem worse than it was. If it happened to a jet today, it would be viewed as miraculous that so many of the passengers survived.
Why not the Baen Free Library (www.baen.com). They have a number of free books available in HTML, Rich Text, Microsoft E-book, Palm, and rocket e-book.
The commentary on why they have the Free Library is also of interest to this discussion. Among other things, they feel that making some of an author's books available for free in electronic form will help sales (both sales of that book, by people that read the e-book and decide that they want a hard copy), as well as sales of other books by the author.
Baen is also offering webscriptions for their new books - $10 for the four books coming out in a given month, available before the hardcover comes out.
With hotmail, it seems you get spam when you open an account with a name that is short, or that has a common name, i.e., JohnSmith103. The spammer just keeps incrementing the number, not caring whether the name is valid or not.
I opened a hotmail account 3 months ago with an obscure name. I haven't used it anywhere, and have received no spam.
Depreciation is over a five(?)year period for computer equipment. When you make a large capital purchase, you're not allowed to subtract all of it from your current earnings before paying taxes. Instead, you reduce your earnings (and taxes) every month by a fraction of the original purchase price, until the item is fully depreciated.
If you switch to a monthly licence, then you can deduct that amount from your earnings in that month. There are reasons to dislike the monthly charges, but it probably doesn't affect your taxes very much.
Its not actually a problem with drilling through "hard rock", the formations are sedimentary, and many can be crumbled in your hand.
Drilling at an angle is desirable because you want to minimize the number of offshore platforms you require. You want a large number of equally spaced wells in the formation, however, A typical platform costs several billion dollars. With current technology, you start all of the wells under the platform, then angle them out to get good coverage in the oil formation.
There seem to be a number of problems with using this to drill for oil and gas, but combustion probably isn't a problem, since there is no oxygen.
There are two other potential problems that I see. The first is the high pressure underground. Oil companies typically use drilling mud which, in addition to cooling the bit and removing the cuttings, is weighted with additives (barite??) to increase the density. The density is controlled so that the hydrostatic pressure is higher than the pressure in the gas/oil reservoirs. This prevents blowouts, where the oil gushes to the surface (the gushers in the old movies) Oil companies hate this, because in addition to the problem of fires, you are wasteing the gas pressure that could be used to help produce additional oil. The laser process will have to supply the high pressure in some manner.
A second problem is damaging the well. Oil and gas are typically contained in sedimentary rock (NOT a liquid reservoir). In terms of flow properties, think of a massive brick saturated with oil - this is roughly what you are trying to produce oil from. Since the flow is radial to the well, damage right around the hole is the worst in terms of damaging the well. While its true that you can fracture the well to improve the production, this adds significant expense. (need to inject large quantities of liquid at high pressure to fracture the rock, as well as proppant (sand) to keep the fractures from closing back down).