The space station was *never* going to be a serious scientific tool. Microgravity research was always a rationalization for building the station, not a good justification for it. In the scientific community, about the only people who think microgravity research is worthwhile are the few groups feeding off NASA's (and some other governments) largess.
In the commercial world, there is little or no interest in microgravity research or manufacturing. The numbers just don't add up.
Face it -- all this hype about how great the station was going to be was fool bait, and you swallowed it.
No, this doesn't work. To be confined in a magnetic bottle, the antimatter has to be in the form of a plasma. Now, the antiprotons in this plasma are constantly interacting, scattering electrostatically off each other. The effect of these interactions is to make the antiprotons do a random walk across the magnetic field lines. Eventually, they'll diffuse out of the plasma. Plasma turbulence makes the problem even worse.
These are precisely the problems that prevent fusion reactors from confining plasmas for long periods. There would be a constant and intolerable leakage of antimatter into the walls of the storage vessel.
Now, you can get rather stable storage of non-neutral plasmas in Penning traps. However, the energy of the stored antimatter is comparable to the magnetic energy of the trap's coils, which makes the devices unable to store substantial amounts of antimatter.
If the ionizing radiation level is high enough to cause significant heating the astronauts will long since have died. A lethal dose of radiation will increase your body temperature by less than.01 degrees C.
The notion that throwing big rocks from the moon would make a good weapon is one of those false 'facts' that people learn from SF stories.
The problem is that to get 1 unit of impact energy on Earth, you need to expend about 1/10 of a unit of energy launching mass from the moon. That's nice, but you still need *enormous* energy production on the moon to equal the energy yield of even tactical sized nuclear weapons.
In 'The Moon Is A Harsh Mistress', the Earth forces would have been able to see the waste heat from the power supply for the launchers and have been able to take it out almost immediately. But that would not have made an interesting story.
No, there's only room for three due to NASA budget overruns. If Congress refuses to fund the overrun, that's not a budget cut.
If the ISS were actually useful for anything Congress might be more willing to cough up the funds. Too bad NASA doesn't seem to be able to do things that can be justified.
Davis's detector was a tank of perchloroethylene. Neutrinos occassionally transmuted chlorine atoms into radioactive argon atoms, which could be swept out by helium sparging and their individual decays detected separately.
His design heats the air to ambient temperature. You can get more work if the air is heated to a higher temperature. For example, heating it to 600 K will roughly double the work for a given quantity of air.
You could burn a fuel (external combustion engine), or you could use a 'thermal battery', which stores heat in a high temperature material in a vacuum insulated container. One can readily exceed 1 MJ/kg; this is much higher than the storage density of lead-acid batteries.
This approach is useful, but it always leaves the possibility of leaks, and has limited capacity.
The process of mineral carbonation exothermically reacts CO2 with certain silicate minerals (or materials derived from these minerals) to yield carbonates that are stable on a geological time scale. There are more than enough of the desirable silicates (serpentine, olivine) to react with all the CO2 that will ever be produced by fossil fuel combustion.
Actually, there are now drugs that are effective against the influenza virus (one is marketed under the name Tamiflu). Just like the anti-bacterial antibiotics, these anti-viral antibiotics work by binding to and interfering with specific macromolecules in the pathogens.
It's a really good thing we have these drugs -- if a major change in the flu virus (like the one that caused the 1918 pandemic that killed 20 million people around the world) were to occur they'd be the only hope for treating it.
They've been working on similar drugs against the common cold, btw, with some promising results.
You can do that, but it's grossly uneconomical compared to making the hydrogen from fossil fuels, or even from biomass, unless the price of electricity drops to less than 2 cents/kWh.
The Kyoto Accord would be very expensive, but worse is that for all its cost it would be completely inadequate to actually halt the buildup of greenhouse gases. Doing the latter would be outrageously expensive and probably not worthwhile.
Fortunately, the accord appears to be dead, now that Russia is balking at signing on. The treaty needs a certain fraction of CO2 emitting nations (55%, IIRC, weighted by emissions) before it goes into effect. Without Russia they won't get over the limit.
Producing hydrogen from fossil fuels is cleaner than burning the fossil fuels in a car because the stationary conversion plant can have lots of heavy pollution control equipment. Moreover, the CO2 it produces can be sequestered (for example, by reaction with magnesium silicates to produce magnesium carbonate and silica), leading to zero greenhouse emissions.
I can agree with almost every other proposal in this article, but he's right - this one will cause a fracas.
I am not talking about removing int, float,
double, char, and other types completely. I
simply want to make them full objects with
classes, methods, inheritance, and so forth.
One word - ew!
Lisp (and Smalltalk?) solved this problem on integers ages ago. You represent small numbers (fixnums) in such a way that you can distinguish them from pointers. Most arithmetic will be fixnums (typically 29 bit values). You do the arithmetic assuming fixnums and branch to the general code on overflows. In non-statically typeed languages this is a harder job because you have to be able to distinguish a fixnum from anything, not just from bignums. If you know the result is a fixnum (say, because you declared the integer to have only 16 bits) you needn't even check for overflow.
In more detail: the integer x is actually stored as x shifted left 3 positions. Pointers have an extra 1 or 3 and-ed into them; you take this off with small offsets when derefing the pointer. The Sparc had instructions that did addition and subtraction but also trapped on the low bits, so you could check if you were trying to add to a non-fixnum with no extra check instructions. These instructions have been deprecated, alas.
You might want separate types that are 'integers mod N' for N being various convenient powers of two.
Another thing to worry about beyond memory cache efficiency is TLB efficiency. If your array is allocated in a single page of virtual memory it could have a smaller load on the TLB than nodes in a chained hash table that are spread over many pages.
In practice don't worry unless profiling shows the cost is significant.
Just as important as the amount of silicon is the kind of silicon. Metallurgical grade silicon is much cheaper than semiconductor grade silicon. IIRC, the spheral technology tolerates lower grade silicon -- when the silicon solidifies in the little spheres the impurities tend to concentrate on an outer layer, which they grind away.
The stupid thing about PV research is that more money gets put into chasing the percentages with wierd compounds rather than trying to achieve something that is useful.
High efficiency, high cost PV cells are useful, in two applications: (1) on spacecraft, and (2) in concentrator systems with high (500x, say) concentration factors. For the latter you want to get as much energy as you can to defray the cost of the optics and tracking hardware, so you want the PV cells to be as efficient as possible (and since the concentration is so high you can afford to spend a lot per unit cell area.)
Gallium arsenside is also useful in space because it can be made much thinner (hence, lighter) than silicon, and because it doesn't lose efficiency so quickly as it gets hot (for spacecraft on solar orbits bringing them closer to the Sun than 1 AU).
Am I to understand that the NASA Global GPS Network, the NASA Global Differentiation GPS, and the NASA GPS Application Exchange all have little or nothing to do with NASA?
The question being discussed was DOD's dependency on NASA. DOD (specifically, the Air Force, with assistance from the Navy) designed and built the GPS system. NASA certainly uses the system, and likely promotes civilian uses for the system, but that's irrelevant to the point that was being discussed.
NASA has little or nothing to do with GPS. The military has been very interested in satellite position location since the late 1950s, and fielded numerous (less capable) systems before fielding GPS.
Not quite. Anybody can deliver an Athlon. Not anybody can deliver a satellite into orbit. NASA is an important and currently irreplacable cog in the United States military machine.
NASA doesn't deliver satellites for the military anymore. The military has moved back to expendable launchers -- they're cheaper and more flexible. The expendables are provided directly by aerospace companies, not through NASA.
Oh, and there are more producers of launch vehicles than there are producers of x86 compatible processors.
The interesting thing about the supercollider project is that it actually cost more money to tear it down, rework the land and return it to other uses than was budgeted to complete the project!
This is simply not true. The SSC was stopped after spending about $2 billion; there was another $4 B or so to go IIRC. The shutdown was a small fraction of a billion dollars.
Slashdot Mirror
The space station was *never* going to be a serious scientific tool. Microgravity research was always a rationalization for building the station, not a good justification for it. In the scientific community, about the only people who think microgravity research is worthwhile are the few groups feeding off NASA's (and some other governments) largess.
In the commercial world, there is little or no interest in microgravity research or manufacturing. The numbers just don't add up.
Face it -- all this hype about how great the station was going to be was fool bait, and you swallowed it.
As a taxpayer in the 30% bracket, I'd rather than NASA was completely eliminated, along with many other parts of the federal government.
No, this doesn't work. To be confined in a magnetic bottle, the antimatter has to be in the form of a plasma. Now, the antiprotons in this plasma are constantly interacting, scattering electrostatically off each other. The effect of these interactions is to make the antiprotons do a random walk across the magnetic field lines. Eventually, they'll diffuse out of the plasma. Plasma turbulence makes the problem even worse.
These are precisely the problems that prevent fusion reactors from confining plasmas for long periods. There would be a constant and intolerable leakage of antimatter into the walls of the storage vessel.
Now, you can get rather stable storage of non-neutral plasmas in Penning traps. However, the energy of the stored antimatter is comparable to the magnetic energy of the trap's coils, which makes the devices unable to store substantial amounts of antimatter.
All elements can capture neutrons.
Not true -- helium does not capture neutrons (5He is unstable to decay back to 4He and a free neutron).
If the ionizing radiation level is high enough to cause significant heating the astronauts will long since have died. A lethal dose of radiation will increase your body temperature by less than .01 degrees C.
The notion that throwing big rocks from the moon would make a good weapon is one of those false 'facts' that people learn from SF stories.
The problem is that to get 1 unit of impact energy on Earth, you need to expend about 1/10 of a unit of energy launching mass from the moon. That's nice, but you still need *enormous* energy production on the moon to equal the energy yield of even tactical sized nuclear weapons.
In 'The Moon Is A Harsh Mistress', the Earth forces would have been able to see the waste heat from the power supply for the launchers and have been able to take it out almost immediately. But that would not have made an interesting story.
Unfortunately, at current costs, even if lumps of solid gold were available in space it would not be economical to go get them.
No, there's only room for three due to NASA budget overruns. If Congress refuses to fund the overrun, that's not a budget cut.
If the ISS were actually useful for anything Congress might be more willing to cough up the funds. Too bad NASA doesn't seem to be able to do things that can be justified.
How do they focus gamma rays? They don't.
Some x-ray telescopes use grazing incidence mirrors, but that's not a practical way to shield.
Davis's detector was a tank of perchloroethylene. Neutrinos occassionally transmuted chlorine atoms into radioactive argon atoms, which could be swept out by helium sparging and their individual decays detected separately.
His design heats the air to ambient temperature. You can get more work if the air is heated to a higher temperature. For example, heating it to 600 K will roughly double the work for a given quantity of air.
You could burn a fuel (external combustion engine), or you could use a 'thermal battery', which stores heat in a high temperature material in a vacuum insulated container. One can readily exceed 1 MJ/kg; this is much higher than the storage density of lead-acid batteries.
This approach is useful, but it always leaves the possibility of leaks, and has limited capacity.
The process of mineral carbonation exothermically reacts CO2 with certain silicate minerals (or materials derived from these minerals) to yield carbonates that are stable on a geological time scale. There are more than enough of the desirable silicates (serpentine, olivine) to react with all the CO2 that will ever be produced by fossil fuel combustion.
Actually, there are now drugs that are effective against the influenza virus (one is marketed under the name Tamiflu). Just like the anti-bacterial antibiotics, these anti-viral antibiotics work by binding to and interfering with specific macromolecules in the pathogens.
It's a really good thing we have these drugs -- if a major change in the flu virus (like the one that caused the 1918 pandemic that killed 20 million people around the world) were to occur they'd be the only hope for treating it.
They've been working on similar drugs against the common cold, btw, with some promising results.
You can do that, but it's grossly uneconomical compared to making the hydrogen from fossil fuels, or even from biomass, unless the price of electricity drops to less than 2 cents/kWh.
The Kyoto Accord would be very expensive, but worse is that for all its cost it would be completely inadequate to actually halt the buildup of greenhouse gases. Doing the latter would be outrageously expensive and probably not worthwhile.
Fortunately, the accord appears to be dead, now that Russia is balking at signing on. The treaty needs a certain fraction of CO2 emitting nations (55%, IIRC, weighted by emissions) before it goes into effect. Without Russia they won't get over the limit.
Producing hydrogen from fossil fuels is cleaner than burning the fossil fuels in a car because the stationary conversion plant can have lots of heavy pollution control equipment. Moreover, the CO2 it produces can be sequestered (for example, by reaction with magnesium silicates to produce magnesium carbonate and silica), leading to zero greenhouse emissions.
Lisp (and Smalltalk?) solved this problem on integers ages ago. You represent small numbers (fixnums) in such a way that you can distinguish them from pointers. Most arithmetic will be fixnums (typically 29 bit values). You do the arithmetic assuming fixnums and branch to the general code on overflows. In non-statically typeed languages this is a harder job because you have to be able to distinguish a fixnum from anything, not just from bignums. If you know the result is a fixnum (say, because you declared the integer to have only 16 bits) you needn't even check for overflow.
In more detail: the integer x is actually stored as x shifted left 3 positions. Pointers have an extra 1 or 3 and-ed into them; you take this off with small offsets when derefing the pointer. The Sparc had instructions that did addition and subtraction but also trapped on the low bits, so you could check if you were trying to add to a non-fixnum with no extra check instructions. These instructions have been deprecated, alas.
You might want separate types that are 'integers mod N' for N being various convenient powers of two.
Microtel is the company that makes the Windows-less x86 PCs that Walmart sells online.
Another thing to worry about beyond memory cache efficiency is TLB efficiency. If your array is allocated in a single page of virtual memory it could have a smaller load on the TLB than nodes in a chained hash table that are spread over many pages.
In practice don't worry unless profiling shows the cost is significant.
Just as important as the amount of silicon is the kind of silicon. Metallurgical grade silicon is much cheaper than semiconductor grade silicon. IIRC, the spheral technology tolerates lower grade silicon -- when the silicon solidifies in the little spheres the impurities tend to concentrate on an outer layer, which they grind away.
High efficiency, high cost PV cells are useful, in two applications: (1) on spacecraft, and (2) in concentrator systems with high (500x, say) concentration factors. For the latter you want to get as much energy as you can to defray the cost of the optics and tracking hardware, so you want the PV cells to be as efficient as possible (and since the concentration is so high you can afford to spend a lot per unit cell area.)
Gallium arsenside is also useful in space because it can be made much thinner (hence, lighter) than silicon, and because it doesn't lose efficiency so quickly as it gets hot (for spacecraft on solar orbits bringing them closer to the Sun than 1 AU).
The question being discussed was DOD's dependency on NASA. DOD (specifically, the Air Force, with assistance from the Navy) designed and built the GPS system. NASA certainly uses the system, and likely promotes civilian uses for the system, but that's irrelevant to the point that was being discussed.
NASA has little or nothing to do with GPS. The military has been very interested in satellite position location since the late 1950s, and fielded numerous (less capable) systems before fielding GPS.
The link you posted has nothing about NASA in it.
NASA doesn't deliver satellites for the military anymore. The military has moved back to expendable launchers -- they're cheaper and more flexible. The expendables are provided directly by aerospace companies, not through NASA.
Oh, and there are more producers of launch vehicles than there are producers of x86 compatible processors.
This is simply not true. The SSC was stopped after spending about $2 billion; there was another $4 B or so to go IIRC. The shutdown was a small fraction of a billion dollars.