There've been experiments with similar things. It does have a built in function VM currently used for isosurface functions and user defined patterns, but the programming facilities are pretty bare-bones. I did write a patch adding a C-like language of mine as a built in function, but never did much with it. (Creating new programming languages is a hobby of mine...the latest is a PostScript-like language with an OpenGL interface.)
Cg seems like it's oriented toward graphics card shaders, for POV-Ray, something more like RenderMan shaders would be more appropriate. There's already huge amounts of RenderMan code out there, and it doesn't have the assumptions and restrictions of a language designed for video cards. Check out POV-Man: http://www.aetec.ee/fv/vkhomep.nsf/pages/POVMan2
CSG objects are currently copied. You can still get very large memory savings due to the fact that you don't store tons of vertices, though.
For doing things that require huge numbers of objects, like a forest or field of grass, you generally use meshes, which do share the mesh data among multiple instantiations. And the scripting features of the POV-Ray scene description language make this very easy.
As for the scales...there are limits to machine precision, and some of the calculations POV does for ray intersections are particularly sensitive to these limits. These limits are rarely a problem, though.
There are no direct relationships between lighting values and real-world units, you must define them yourself. However, with appropriately chosen values, the results can be very accurate.
The Persistence Of Vision Raytracer. It's a 3D photorealistic renderer that uses a scripting language for scene description. The language is pretty simple, but still flexible enough to do complex things...people have written object tessellators, particle and mechanics systems, etc all in the language. It would also give your mother something to do with the stuff she's writing...make pretty pictures. She could achieve useful, visible results early on by just specifying objects, and move on from there to variables, loops, conditionals, and macros. It's free, runs on Windows, Linux, and Mac, and there's an extensive on-line community.
http://www.povray.org/
For example, here's a script that puts 9 reflective spheres in a ring on a checkered plane:
We could put it into low earth orbit...but we could put a lot of other, more useful stuff up for the same price. And then you're just in low earth orbit...not a very useful place to be, and you will have to continually re-boost the thing back into a higher orbit because of atmospheric drag, which will be harder because of its high mass (though it will be necessary less often for the same reason). Put the same mass into power systems for running this deflector, and you could use the same power supply to run an ion engine to counter the drag, and still have plenty of mass left over in your budget.
As for "once you push, its no longer a shove"...the more massive the object, the more work it takes to accelerate it to a given velocity. If you double the mass, you halve the speed, and make it twice as hard to reach Mars. (Not exactly, actual orbital mechanics make this more complex, but you get the idea.)
Even if it turns out to be twice as good at blocking radiation as everything else, it's no good if it takes ten times as long to get anywhere. The main things water shielding would be useful for are fixed habitats (probably in high orbit) and orbital cyclers. (Basically a habitat in an elliptical orbit that intersects that of Earth and some useful destination...Mars, for instance.)
Water would probably be better for its mass, actually. More nuclei for the mass...in lead, more of the mass is squeezed into bigger, but still tiny nuclei. Hydrogen and oxygen nuclei are smaller, but there's a lot more of them, so there's more of a "visible" cross-section. You want something dense (to reduce total volume) yet composed of light elements. I also seem to recall that hydrocarbons were particularly good at absorbing radiation.
The problem is that this requires putting a lot of mass into space, and then dragging that mass around wherever you go. Also, you have to carry enough water to protect against relatively brief periods of higher radiation, while with this shielding system, you could conceivably just overbuild the shielding systems and redirect more power to them when necessary.
If orbital mining gets started, we will probably have more than enough water to use for passive habitat shielding, but for anything that needs to accelerate or be lifted into orbit from the surface, it's just too much dead mass.
First: fusion plants don't blow up. Well, the boiler might...but the reactor won't, and practically any other kind of large power plant uses boilers. If containment fails in an electromagnetically confined plasma reactor like the tokamak...nothing happens. The reaction catastrophically loses heat through the reactor walls, and stops. You might have to do some repairs on the interior, but that's all. No big mushroom cloud, just a cooling reactor. The reason that we don't have fusion power yet is that it is hard to keep a fusion reaction going, not any danger of the reactor exploding. Besides all this, the isotopes of hydrogen likely to be used as fuel are not common...deuterium, currently used in the form of heavy water for some fission plants, and tritium, which is extremely rare and decays quickly. Besides that, many potentially useful fusion reactions also involve helium 3, which is also quite rare on Earth. Lithium isn't a byproduct, it's a fuel...it converts to tritium when irradiated with neutrons. The fusion "ash" of the reactions being considered for power is helium 4.
As for fission plants...they don't blow up either. The Chernobyl incident was a *steam* explosion, made worse by hydrogen generated by superhot steam coming into contact with hot graphite, and then air full of oxygen being intoduced into the whole superhot mess. And Chernobyl *did* suffer meltdown. It didn't just come close, large chunks of the core melted. TMI also suffered a partial meltdown, though much less severe than that at Chernobyl, and the safety systems were able to keep it from turning into the kind of mess we had at Chernobyl. There was also a partial meltdown at NRX in Canada (1952), and a fire and meltdown at Sellafield in England in 1957, and several other incidents of fires or meltdowns. Modern reactor designs just won't get that far...the reaction is self limiting, and the reactor simply can't get hot enough to cause damage.
"Enrichment" of uranium has nothing to do with purity. Uranium has several isotopes, and uranium 235, the one that's useful in fission bombs, is extremely rare. Enriched uranium has been processed to contain a higher concentration of this isotope.
A grazing strike would mean more atmosphere to pass through, burning off more of the asteroid, and making it more likely to break up before reaching the surface.
I'm not sure how different the damage would be if it hit the ground. A low velocity strike will splash a lot more debris in the direction of the impact, but I have the impression that the cratering caused by this type of impact is caused more by extremely hot vaporized material expanding in all directions from the site rather than just the asteroid pushing stuff out of its way. Most large craters seem to be pretty circular, anyway...
You are mistaken. The vast majority of the elements always exist in the form of molecules. Atomic hydrogen (lone atoms) will quickly bond to something, it will be very strongly reducing. Gaseous hydrogen is normally composed of covalently bonded H2 molecules. Noble gases like helium, neon, xenon, etc. are the only ones I know of that commonly exist in atomic form.
A helium atom has the outer (and only) electron shell full, so it doesn't try to combine with other atoms to form molecules. This is the same shell that hydrogen atoms have (the 1s shell), and though it contains two electrons in the case of helium, it is roughly the same size (smaller, actually). A H2 molecule is considerably larger than a helium atom.
However, common helium atoms are more massive than common hydrogen molecules (containing two protons as well as two neutrons when H2 has only two protons), so they move faster than helium atoms at the same temperature. And hydrogen molecules are more chemically active than helium (which is one of the "inert" gases), and may interact with solid materials in such a way that makes them diffuse through it faster.
The innovation here is that the only part that moves in this lens is the lens itself, or rather the fluids within the lens. No motors, solenoids, or other mechanical parts, the lens itself responds to the electrical impulse. Possibly more controllable and better shaped, definitely more reliable.
We've done flybys...but not of this comet, and even if it comes loose from the comet, it is likely to stick close to it for a longer period than any of our other probes.
As for Shoemaker-Levy 9...it smacked into a gas giant after being torn apart by the tidal forces caused by being that deep in Jupiter's gravity well. The same tidal forces that make Io the most volcanic body in the solar system. This is not a comparable situation. In addition, I don't recall anyone being surprised that it broke up.
Using constant thrust to hold the probe on the comet surface while it anchors itself would require very finely-controlled thrusters, plus a great deal of extra fuel, plus motors, transmissions, the drill bits and anchors themselves, and a power supply sufficient to run them (which would be overkill for running the rest of the probe after it landed). More parts to fail, more mass to carry along, more complex to design, and a complicated operation to perform which would have to be completely automated, all to get the probe anchored far more strongly than it needs to be. The harpoon is small, simple, a lot easier to do, and far less to go wrong.
Mars is a bit further from the sun...less radiation to shield from in the first place. Also, though the Earth's magnetic field does shield from radiation, the atmosphere does a much more thorough job. Thickening up the atmosphere of Mars would greatly reduce the amount of charged particle radiation reaching the surface. And once things started producing oxygen, it would be possible for an ozone layer to form, blocking much of the UV.
As for the solar wind stripping away the atmosphere...that'll be a worry when the sun is going into its red giant phase. In other words, of no concern to us. To back up my point: Venus has no significant magnetic field, on top of being less than half the distance from the sun, and it has an atmosphere far thicker than that of Earth.
Plant life can easily survive in the temperature, moisture, and radiation conditions that appear to exist on Mars. Atmosphere would be a slightly bigger problem for anything of any size, but not insurmountable. The atmosphere would need to be thickened quite a bit...some of that would happen if it the planet just warmed up a little, to release more CO2 and water vapor trapped in the ground, which would in turn help the planet warm up more.
The big problem is that Mars has an atmosphere consisting almost entirely of CO2 though, while that of Earth is mostly nitrogen with about 18% oxygen. It might be possible to convert it almost entirely to a thin oxygen atmosphere which would be breatheable, barely, but it won't be anything like Earth unless we somehow add a lot more atmospheric nitrogen. Also, consuming the CO2 will cool the planet...not desired for terraforming. We could probably establish plant life on Mars within a decade, but it wouldn't be anything like Earth for a very, very long time.
1: if the harpoon doesn't get a good hold, the probe probably will drift away from the comet. Getting the probe that close in the first place will still be a huge achievement, and it'll still return useful data.
2: It's a comet. An orbital ice-berg that's been bashed around for billions of years. A little harpoon isn't going to break it in half. Might smash a small chunk off, but it won't split the comet in half.
3: The lander's heading toward the comet already, the harpoon launch recoil (assuming there is any) is unlikely to overcome the probe's momentum. And it is probably a small rocket harpoon, with practicaly no recoil.
As for the drill-and-screw...a harpoon would be far more likely to get the initial hold. It's a quite well understood technology. On Earth, drilling typically requires rather firm support for the machinery doing the drilling. For the probe, it would require maneuvering up to the comet and holding position next to it while it attempted to drill in an anchor, at a distance from any human which makes real-time remote control impossible. Plus, it would be far more mechanically complex, a lot heavier, and a lot more power-hungry. The harpoon could use a small solid-fuel rocket, the drill would require a motor and power supply to run it. Not to mention the fuel required to hold the probe in place while drilling.
Slashdot Mirror
There've been experiments with similar things. It does have a built in function VM currently used for isosurface functions and user defined patterns, but the programming facilities are pretty bare-bones. I did write a patch adding a C-like language of mine as a built in function, but never did much with it. (Creating new programming languages is a hobby of mine...the latest is a PostScript-like language with an OpenGL interface.)
Cg seems like it's oriented toward graphics card shaders, for POV-Ray, something more like RenderMan shaders would be more appropriate. There's already huge amounts of RenderMan code out there, and it doesn't have the assumptions and restrictions of a language designed for video cards. Check out POV-Man: http://www.aetec.ee/fv/vkhomep.nsf/pages/POVMan2
CSG objects are currently copied. You can still get very large memory savings due to the fact that you don't store tons of vertices, though.
For doing things that require huge numbers of objects, like a forest or field of grass, you generally use meshes, which do share the mesh data among multiple instantiations. And the scripting features of the POV-Ray scene description language make this very easy.
As for the scales...there are limits to machine precision, and some of the calculations POV does for ray intersections are particularly sensitive to these limits. These limits are rarely a problem, though.
There are no direct relationships between lighting values and real-world units, you must define them yourself. However, with appropriately chosen values, the results can be very accurate.
The Persistence Of Vision Raytracer. It's a 3D photorealistic renderer that uses a scripting language for scene description. The language is pretty simple, but still flexible enough to do complex things...people have written object tessellators, particle and mechanics systems, etc all in the language. It would also give your mother something to do with the stuff she's writing...make pretty pictures. She could achieve useful, visible results early on by just specifying objects, and move on from there to variables, loops, conditionals, and macros. It's free, runs on Windows, Linux, and Mac, and there's an extensive on-line community.
http://www.povray.org/
For example, here's a script that puts 9 reflective spheres in a ring on a checkered plane:
camera {
location < 0, 3,-8>
look_at < 0, 0.5, 0>
angle 35
}
light_source {<-5, 8,-3>, color rgb <1, 1, 1>}
plane {y, 0
pigment {checker color rgb < 1, 1, 1>, color rgb < 0, 0, 0>}
}
union {
#local J = 0;
#while(J < 9)
sphere {< 1, 0.25, 0>, 0.25 rotate y*J*360/9}
#local J = J + 1;
#end
pigment {color rgb < 1, 1, 1>}
finish {reflection 1 diffuse 0 ambient 0}
}
We could put it into low earth orbit...but we could put a lot of other, more useful stuff up for the same price. And then you're just in low earth orbit...not a very useful place to be, and you will have to continually re-boost the thing back into a higher orbit because of atmospheric drag, which will be harder because of its high mass (though it will be necessary less often for the same reason). Put the same mass into power systems for running this deflector, and you could use the same power supply to run an ion engine to counter the drag, and still have plenty of mass left over in your budget.
As for "once you push, its no longer a shove"...the more massive the object, the more work it takes to accelerate it to a given velocity. If you double the mass, you halve the speed, and make it twice as hard to reach Mars. (Not exactly, actual orbital mechanics make this more complex, but you get the idea.)
Even if it turns out to be twice as good at blocking radiation as everything else, it's no good if it takes ten times as long to get anywhere. The main things water shielding would be useful for are fixed habitats (probably in high orbit) and orbital cyclers. (Basically a habitat in an elliptical orbit that intersects that of Earth and some useful destination...Mars, for instance.)
Water would probably be better for its mass, actually. More nuclei for the mass...in lead, more of the mass is squeezed into bigger, but still tiny nuclei. Hydrogen and oxygen nuclei are smaller, but there's a lot more of them, so there's more of a "visible" cross-section. You want something dense (to reduce total volume) yet composed of light elements. I also seem to recall that hydrocarbons were particularly good at absorbing radiation.
The problem is that this requires putting a lot of mass into space, and then dragging that mass around wherever you go. Also, you have to carry enough water to protect against relatively brief periods of higher radiation, while with this shielding system, you could conceivably just overbuild the shielding systems and redirect more power to them when necessary.
If orbital mining gets started, we will probably have more than enough water to use for passive habitat shielding, but for anything that needs to accelerate or be lifted into orbit from the surface, it's just too much dead mass.
First: fusion plants don't blow up. Well, the boiler might...but the reactor won't, and practically any other kind of large power plant uses boilers. If containment fails in an electromagnetically confined plasma reactor like the tokamak...nothing happens. The reaction catastrophically loses heat through the reactor walls, and stops. You might have to do some repairs on the interior, but that's all. No big mushroom cloud, just a cooling reactor. The reason that we don't have fusion power yet is that it is hard to keep a fusion reaction going, not any danger of the reactor exploding. Besides all this, the isotopes of hydrogen likely to be used as fuel are not common...deuterium, currently used in the form of heavy water for some fission plants, and tritium, which is extremely rare and decays quickly. Besides that, many potentially useful fusion reactions also involve helium 3, which is also quite rare on Earth. Lithium isn't a byproduct, it's a fuel...it converts to tritium when irradiated with neutrons. The fusion "ash" of the reactions being considered for power is helium 4.
As for fission plants...they don't blow up either. The Chernobyl incident was a *steam* explosion, made worse by hydrogen generated by superhot steam coming into contact with hot graphite, and then air full of oxygen being intoduced into the whole superhot mess. And Chernobyl *did* suffer meltdown. It didn't just come close, large chunks of the core melted. TMI also suffered a partial meltdown, though much less severe than that at Chernobyl, and the safety systems were able to keep it from turning into the kind of mess we had at Chernobyl. There was also a partial meltdown at NRX in Canada (1952), and a fire and meltdown at Sellafield in England in 1957, and several other incidents of fires or meltdowns. Modern reactor designs just won't get that far...the reaction is self limiting, and the reactor simply can't get hot enough to cause damage.
"Enrichment" of uranium has nothing to do with purity. Uranium has several isotopes, and uranium 235, the one that's useful in fission bombs, is extremely rare. Enriched uranium has been processed to contain a higher concentration of this isotope.
A grazing strike would mean more atmosphere to pass through, burning off more of the asteroid, and making it more likely to break up before reaching the surface.
I'm not sure how different the damage would be if it hit the ground. A low velocity strike will splash a lot more debris in the direction of the impact, but I have the impression that the cratering caused by this type of impact is caused more by extremely hot vaporized material expanding in all directions from the site rather than just the asteroid pushing stuff out of its way. Most large craters seem to be pretty circular, anyway...
You are mistaken. The vast majority of the elements always exist in the form of molecules. Atomic hydrogen (lone atoms) will quickly bond to something, it will be very strongly reducing. Gaseous hydrogen is normally composed of covalently bonded H2 molecules. Noble gases like helium, neon, xenon, etc. are the only ones I know of that commonly exist in atomic form.
A helium atom has the outer (and only) electron shell full, so it doesn't try to combine with other atoms to form molecules. This is the same shell that hydrogen atoms have (the 1s shell), and though it contains two electrons in the case of helium, it is roughly the same size (smaller, actually). A H2 molecule is considerably larger than a helium atom.
However, common helium atoms are more massive than common hydrogen molecules (containing two protons as well as two neutrons when H2 has only two protons), so they move faster than helium atoms at the same temperature. And hydrogen molecules are more chemically active than helium (which is one of the "inert" gases), and may interact with solid materials in such a way that makes them diffuse through it faster.
The innovation here is that the only part that moves in this lens is the lens itself, or rather the fluids within the lens. No motors, solenoids, or other mechanical parts, the lens itself responds to the electrical impulse. Possibly more controllable and better shaped, definitely more reliable.
We've done flybys...but not of this comet, and even if it comes loose from the comet, it is likely to stick close to it for a longer period than any of our other probes.
As for Shoemaker-Levy 9...it smacked into a gas giant after being torn apart by the tidal forces caused by being that deep in Jupiter's gravity well. The same tidal forces that make Io the most volcanic body in the solar system. This is not a comparable situation. In addition, I don't recall anyone being surprised that it broke up.
Using constant thrust to hold the probe on the comet surface while it anchors itself would require very finely-controlled thrusters, plus a great deal of extra fuel, plus motors, transmissions, the drill bits and anchors themselves, and a power supply sufficient to run them (which would be overkill for running the rest of the probe after it landed). More parts to fail, more mass to carry along, more complex to design, and a complicated operation to perform which would have to be completely automated, all to get the probe anchored far more strongly than it needs to be. The harpoon is small, simple, a lot easier to do, and far less to go wrong.
Mars is a bit further from the sun...less radiation to shield from in the first place. Also, though the Earth's magnetic field does shield from radiation, the atmosphere does a much more thorough job. Thickening up the atmosphere of Mars would greatly reduce the amount of charged particle radiation reaching the surface. And once things started producing oxygen, it would be possible for an ozone layer to form, blocking much of the UV.
As for the solar wind stripping away the atmosphere...that'll be a worry when the sun is going into its red giant phase. In other words, of no concern to us. To back up my point: Venus has no significant magnetic field, on top of being less than half the distance from the sun, and it has an atmosphere far thicker than that of Earth.
Plant life can easily survive in the temperature, moisture, and radiation conditions that appear to exist on Mars. Atmosphere would be a slightly bigger problem for anything of any size, but not insurmountable. The atmosphere would need to be thickened quite a bit...some of that would happen if it the planet just warmed up a little, to release more CO2 and water vapor trapped in the ground, which would in turn help the planet warm up more.
The big problem is that Mars has an atmosphere consisting almost entirely of CO2 though, while that of Earth is mostly nitrogen with about 18% oxygen. It might be possible to convert it almost entirely to a thin oxygen atmosphere which would be breatheable, barely, but it won't be anything like Earth unless we somehow add a lot more atmospheric nitrogen. Also, consuming the CO2 will cool the planet...not desired for terraforming. We could probably establish plant life on Mars within a decade, but it wouldn't be anything like Earth for a very, very long time.
1: if the harpoon doesn't get a good hold, the probe probably will drift away from the comet. Getting the probe that close in the first place will still be a huge achievement, and it'll still return useful data.
2: It's a comet. An orbital ice-berg that's been bashed around for billions of years. A little harpoon isn't going to break it in half. Might smash a small chunk off, but it won't split the comet in half.
3: The lander's heading toward the comet already, the harpoon launch recoil (assuming there is any) is unlikely to overcome the probe's momentum. And it is probably a small rocket harpoon, with practicaly no recoil.
As for the drill-and-screw...a harpoon would be far more likely to get the initial hold. It's a quite well understood technology. On Earth, drilling typically requires rather firm support for the machinery doing the drilling. For the probe, it would require maneuvering up to the comet and holding position next to it while it attempted to drill in an anchor, at a distance from any human which makes real-time remote control impossible. Plus, it would be far more mechanically complex, a lot heavier, and a lot more power-hungry. The harpoon could use a small solid-fuel rocket, the drill would require a motor and power supply to run it. Not to mention the fuel required to hold the probe in place while drilling.