I'm sure they already know. Notice that they use a traditional ground-launch system for larger payloads or higher orbits.
Launching from a plane gains you a small bit of altitude and a tiny bit of initial velocity. The altitude is almost irrelevant...a ground launched rocket will pass that altitude at far greater speed very early in its launch....and the speed boost is tiny, even supersonic speeds are far lower than orbital speeds. At a guess, I'd say their main cost savings is the flexibility in launch locations...practically anywhere the carrier plane can take off from, allowing them to more easily achieve high inclination or equatorial orbits. They also don't have to build, maintain, or rent massive launch installations for these launchers.
Orbital rockets are big, heavy, and fragile, and launching one from a stable ground platform is hugely easier than launching from a flying aircraft. The heavier structure required to survive launch from an aircraft probably outweighs any fuel savings, and the heavier structure and first stage aircraft together would almost certainly cost more...fuel is cheap.
For the X Prize, it's a big deal because all they needed is altitude...they could get about halfway to the goal on an ordinary aircraft. Orbit is a lot harder to reach, not only do you need altitude, you need a great deal of speed that no airplane can come close to achieving. Aircraft simply aren't very helpful for getting to orbit.
It is a problem, due to Coriolis effects. Basically, get up too quick and you'll fall over. We could probably get used to it in time, but generally, the larger the radius and slower the rotation, the better. However, plants are unlikely to care, so you could just use a spinning shelf arrangement for the gravity-sensitive plants. It wouldn't have to be too complicated, just a squirrelcage type mechanism.
For humans, the best idea is probably to attach a counterweight to the inhabited section with a long cable. You could get a really huge radius of rotation that way with little material, it's extremely mechanically simple, and it doesn't involve sending huge amounts of material into orbit. The counterweight could be equipment that doesn't need constant human presence, or hazardous equipment such as a nuclear reactor. (With a long enough cable, you wouldn't need shielding for it.)
The electrode array's a couple millimeters on a side. It'd be like a really tiny stroke.
Of course, a full blown version would probably have electrodes scattered around the brain. In that case, anything ranging from seizures to death is possible. However, I really don't see something like this using a direct electrical connection. If I were designing it, I'd use an induction loop to transmit power to the internal electronics, and LED's under the skin to carry the detected signals. Rather than a plug, you'd just wear a headband. It would be impossible to apply any significant amount across electrodes. But I don't think brain interfaces will be seriously two-way for a very long time...brain output/audiovisual input is likely to work better for most purposes. Plant some little transducers in the inner ear, and strap your iPod on your head or around your neck...
When it goes nova, the white dwarf casts off most of the matter it gains, so it stays at nearly the same mass. However, the donor star is no longer fusing, so it cools and shrinks. As it becomes cooler and more compact, its "surface gravity" increases and the average molecular velocity goes down, both effects slowing the mass loss. It'll lose lighter elements preferentially, especially as it cools and heavier elements combine into even heavier molecules, while helium stays as single atoms and hydrogen mostly forms slightly lighter H2 molecules. (H2: 2 amu. He: 4 amu. CO: 28 amu. Higher molecular weight == lower molecular velocities at a given temperature, and lower rates of loss.) As a result, it ends up denser and with a higher surface gravity than typical objects of its size and temperature.
Also, only a tiny portion of the nova-expelled mass would be reabsorbed by the donor star, and most of that would again be lost to the dwarf. Actually, it seems likely that the energy of the extremely nearby nova would blast even more mass away from the donor star.
It's not fusing internally any more, so it's cooling down and shrinking. Its "surface" is deeper in its gravity well and colder, so it's not getting stripped away as quickly. The vampirism probably hasn't stopped, just become too small to detect.
Also, the thing probably has much higher concentrations of "metals" than typical brown dwarfs or gas giants...for a while, it was fusing, and it probably lost lighter elements to the white dwarf more easily.
How about storing (cold) antiprotons in a normal matter container? At short distances, the antiprotons would be repelled by the electrons in the orbitals of the neutral atoms. Maybe a cold antiproton-hydrogen mix would be stable for significant periods. To set it off, just jump an arc through it or something...ionize the hydrogen, freeing the protons to interact directly with the antiprotons. Result: lots of ionizing radiation, and more proton-antiproton annihilation.
Um...after the rocket burns out and before the vehicle gets deep enough back into the atmosphere to maneuver, it *is* a ballistic vehicle. (And so is everything in orbit, for that matter.) It's still a suborbital vehicle...it leaves the atmosphere, but never achieves orbital or escape velocity. "Goes straight up, and falls straight back down" is a pretty accurate description of its trajectory...the horizontal component is practically zero compared to what is necessary to reach orbit.
A space elevator is a really long "superstrong" ribbon.
Correct.
But then things get confusing. It's pretty obvious one end hooks to Earth, but what do you hook the other to? The Moon? An asteroid?
Not the moon. And not necessarily an asteroid, or anything. You could build a ribbon that extends far past GEO, and you won't need any kind of counterweight. As long as there is enough mass higher than GEO, the elevator will stay up.
Assuming we find a substance strong enough to build such a cable from, don't we then have to worry about the strength of the tethers and ultimately the consequences of altering Earth's rotation?
As mentioned, we have found materials strong enough, the problem is now producing them. And there will be no significant effects on Earth's rotation. Yes, momentum for the payloads will be taken from Earth's angular momentum...but Earth is really, really big and massive. Tidal effects with the moon will likely have greater effects than we could cause with beanstalks.
190,236,576 miles is just barely over 2AU...I wonder if someone mistook the major diameter of Earth's orbit for its mean radius. Still a stupid error...if they didn't make an extreme conversion error, they completely screwed up the definition of the unit.
They do...but we also have computers that let us do even better by doing a transfer like this. One really big reason to do it this way is that we can do an extended mission rather than a short flyby. Mars and Venus have atmospheres that can be used for aerobraking, and aren't that far from Earth in orbital velocity. Mercury doesn't have an atmosphere, you have to carry enough fuel to do the entire job of insertion into orbit, which for a direct insertion into orbit around Mercury or any of the planets past Mars, is quite a bit of fuel...fuel which takes up mass that could otherwise be devoted to instruments.
I hear it too, I can tell a muted TV is on as soon as I enter a room. The horizontal sync frequency for NTSC is 15.75 kHz, I've always assumed it was coils or deflector plates vibrating at that frequency. I've never personally met someone who hears it, but they may just not have noticed it...normal hearing is supposed to go up to 20 kHz.
> What I don't accept is that clouds themselves are a product of bacterial colonies other than as a by-product from releaseing water vapor from inside their cellular structures. Water clouds would form even if the Earth were sterile of life.
Well, spores and other microbes could act as condensation seeds. Have a hard time getting bacteria in one droplet to produce more droplets though...just about the best you could hope for would be bacteria getting rained down, dried out, and then kicked back up as dust. Cloud-borne life would probably be transferred by air currents and droplet collisions, and would be unlikely to have a strong effect on cloud formation. Well, absorption of light by the bacteria could heat the cloud up, dispersing it or making it less likely to rain out, but they would be quite noticeable then.
Cellular automata often produce cloud-like shapes, which really isn't surprising when you think about it. And some aspects of cloud formation could be simulated with CA...they have some similarities. The cloud is a group of tiny droplets condensed out of the air, the vaprous water is the "food", the droplets are the "cells". However, fluid dynamics makes a better cloud simulation...you get similar effects in many fluid systems, without any chemistry (organic or otherwise) involved. Clouds are simply caused by fluid dynamics and temperature/phase changes.
Clouds are complex systems that show some aspects of life, but none of a living organism. However, they could make a good home for microbial life.
As far as I can tell, this is basically an overly complex version of a momentum wheel...basically, a massive, low-speed flywheel. Spin it one way, the surrounding structure spins the opposite direction...stop the momentum wheel, and the entire structure stops spinning. That is, angular momentum for the entire structure is conserved.
The Hubble telescope uses momentum wheels for very precise aiming without requiring propellant and complex, failure-prone, and mirror-dirtying thrusters. These people are trying too hard...the basic idea is just a massive wheel attached to an electric motor.
This seems to be a common misconception. The solar wind is not a blowtorch that blasts any unprotected atmosphere into space. It will very slightly increase the rate of atmosphere escape, but it will still happen so slowly that it will probably not make a difference until after the sun ages enough to render Earth uninhabitable anyway. We have one big counterexample to that theory...Venus has slightly less gravity than Earth, and virtually no internally generated magnetic field, only a barely detectable one induced by the sun. It also receives over 1.9 times as much solar radiation as Earth, and over 4.4 times as much as Mars, yet its atmospheric pressure is 90 times as high as that of Earth...that's about 12000 times as much as Mars. Mars has little atmosphere because of its formation...it likely lost some gases that would have formed its atmosphere to Jupiter, and got more blasted off its surface by bombardment from the forming asteroid belt. Then it cooled, and a big chunk of its atmosphere froze...Martian atmospheric pressure actually varies highly depending on season, due to sublimating and freezing CO2.
In addition, the Earth's atmosphere makes an excellent shield against charged particles...there will likely be a slight increase in secondary radiation, but not enough to cause measureable effects on Earthly life.
In addition...it was mentioned that U238 has a half-life of four billion years. This is a *good* thing...as you mentioned, it decays very slowly, giving off very low amounts of radiation in any reasonable period of time. It's the medium-life isotopes you have to worry about, the ones with half-lives long enough to stick around a while, but short enough to produce high amounts of radiation.
As for the pyrophoricity...aluminum is pyrophoric. Make a large pile of aluminum powder, and you risk it spontaneously igniting in a very, very hot fire, especially in a slightly damp atmosphere. (The water loses oxygen to the aluminum, producing heat and hydrogen. You get a pile of hot, flammable metal with high internal concentrations of hot, flammable gas.) Another metal known for flammability is magnesium...which doesn't need to be finely divided, it can burn in bulk quantities (though it isn't easily ignited in that state). Guess what...aluminum-magnesium alloys are in common use, and are not known for bursting into flame.
> I was wondering, it seems people who die from radiation do so because their body rejects itself since it's been popped full of tiny holes. Would it be possible to save more people with radiation exposure by pumping them full of anti-rejection drugs or shutting down their immune system somehow?
That's nearly the worst thing you could do. The problems don't arise from rejection, they come from ions and free radicals formed by the radiation impacting on the various chemicals in the body. A particularly unlucky hit can irreparably ruin a vital portion of DNA or cause enough damage to other cellular processes to kill the cell. If this happens a lot, you die from the toxic byproducts of the dying cells, and from the loss of cells that you really need. A very unlucky hit only modifies the DNA in such a way that the cell loses control of its reproduction...if the immune system doesn't detect the problem and kill that cell and all its descendants, you develop cancer. To make it all worse, your immune system is weakened by cell damage and the need to cope with all the junk floating around the system, leaving you more open to both infection and tumors caused by mutated cells.
For extreme radiation exposure, what you want is antioxidants, immune system *boosters*, lots of fluids, and other support to keep your kidneys and liver from shutting down under the load. And fortunately, although large amounts of radiation exposure do increase the risk of cancer, it is still very unlikely. If you do get cancer, it was probably due to something else.
Even if it is 1/3 as reliable...they could put 3 redundant systems in place and still pay only $3.9 million rather than $100 million. And have plenty of spare parts to swap around...3 systems would be more than 3 times as reliable, as the redundant systems on the ISS recently showed. (Machine 1 has faulty part A, machine 2 has faulty part B, rip part A out of machine 2 and you can have machine 1 working again.)
More mass to lift into orbit, of course...it's a minimization problem. However, government projects often seem to miss this, going for a slight improvement in reliability at a large cost increase when more redundant lower reliability components would do just as well at lower cost. Of course, there are some times where you just must have the highest quality possible...
What electricity? It conducts electricity, it doesn't generate it...you would have to bring your conductive clothes into contact with an already dangerous exposed source, which clothes made of insulating fibers would be no guarantee of protection from. And even then, the danger is almost entirely due to electricity passing through the core of the body, which it is unlikely to do when said core is surrounded by a far better conductor.
Really, your complaints remind me of a comment I once heard while I was working on some electronics by someone who was worried a short length of wire that wasn't connected to anything was in danger of electrocuting me. Don't you realize that most jewelry is made of conductive material? Silver is the best metallic conductor there is, and gold isn't far behind copper. Conductivity != full of electricity.
The dark areas thought to be ethane oceans turned out to be water ice discolored by organic impurities...this does not mean there is no liquid on Titan. In fact, the article specifically refers to liquid rain, though I don't see any references to this on the nasa.gov site.
However, if you do see hail on Titan...the surface gravity is just 0.14 times that of Earth, and the atmosphere 1.6 times as thick. Unless methane ice is much more dense than water ice, hail would fall much more slowly. It would look like slow-motion, and unless the hailstones grow very slowly, the hail could get quite big. Sounds like something that would be very interesting to see...
Another rendering system that supports photon mapping is POV-Ray, the Persistance Of Vision Raytracer. Unlike Brazil, it is free, and although it is not Open Source, the source code is available, and you can distribute patches and, with some restrictions, modified versions.
To summarize, Forward raytracing: traces actual photons through the scene from the light source, reflecting off/refracting through objects in the scene, and through the camera aperture onto the "film". You end up tracing many photons that will never hit the camera, and the results are blurry or grainy unless you use settings that are just impractical with current technology.
Backwards (traditional) raytracing: traces the light paths backwards, out through the camera onto an object in the scene. From there, rays are traced to the lights in the scene to check for shadowing objects. This works pretty well, but can not compute illumination from mirrored reflections or refraction. However, it can compute diffuse reflection, by tracing more rays to find the illumination of the surrounding scene. This is usually slower than scanline rendering, but produces very good results.
Photon mapping: forward raytracing (like that used in this project) is used to build a map of photons deposited on surfaces within the scene, which is then used in the illumination computations when the scene is rendered with backwards raytracing or scanline rendering.
> The lunar regolith doesn't allow light to pass through, and thus prevents effective farming. Humans aren't the only things that need shielding.
Actually, we pretty much are. Crops have a very limited growing season, long-term effects from mutations just aren't much of a worry for them. Filters to reduce the intensity (or simply an arrangment of mirrors indirectly lighting the crops) and cut out some UV will be sufficient.
> the Lunar soil contains large amounts of oxygen... in tightly locked-up forms that are not easy to process.
You can get far by simply heating it, easier on the Moon than on Mars.
> Not on Mars; Mars has the hydrogen (the moon doesn't). What, you think we're going to be powering either site (which are expected to have refining) by shipping *chemical fuel*? Are you crazy? Have you looked at the math involved? It's ludicrous.
I thought I was pretty clear that it would only use it for the setup power. Initially, it will require some form of power transported to the moon. The craft taking people and materials to the moon will require power. This all results in a significant amount of water being taken to the vicinity of the moon.
Mars does have the hydrogen, but it also has less than half the amount of sunlight per square meter.
Your entire argument about farming is ridiculous...I specifically said supplementary food. You ignore the fact that the growing season is only a small portion of the year to inflate the figures, and I have no idea what crops you were thinking of. The oxygen would be provided by a solar furnace during the day, not an electrical Brazilian alumina smelter on demand.
> It's an issue of shielding. A partial pressure dome for farming wouldn't work on the moon for farming because of radiation.
A double-layered translucent dome (to help regulate the temperature), plus Venetian blinds to provide a diurnal cycle for plants that need it would probably work just fine on the moon. As I said, crops probably don't need much protection from radiation, they certainly don't need as much as us.
> So you pick and choose which asteroids? I'm talking mining in general. The best asteroids aren't necesarily going to pass by Earth.
You chopped out the part which explained what I was talking about. The asteroid would have an elliptical orbit that comes close to that of Earth and the belt. Habitats would be built on the asteroid, which would then provide a means of safely transporting people between Earth and the belt. No need to go to Mars. Even if the delta-V is higher, the manned ships have far shorter trips to make, and can greatly cut down on shielding.
A comets tail is very thin, and the gravity of a comet is practically zero. Titan and Mars are giants compared to comets.
As for the magnetic field of Saturn...Titan actually sometimes passes outside the Saturnian magnetopause. Being within the magnetic field is no guarantee of protection either: like Earth, Saturn has radiation belts, which may intersect the orbit of Titan.
Venus has a magnetic field about 0.000015 times as strong as Earth's, probably resulting from interactions between ions in its upper atmosphere and the solar wind. And I extremely strongly doubt that volcanic activity can account for an atmosphere on a roughly Earth-sized planet which is 90 times as heavy as that of Earth.
The magnetic field is not the reason for the thin atmosphere. Venus also has no significant magnetic field, slightly less gravity than Earth, receives far more solar radiation (nearly twice that of Earth, about 4.46 times that of Mars), and its surface atmospheric pressure is about 90 times that of Earth. Titan's atmosphere, mostly nitrogen, has a surface pressure 1.6 times that of Earth, and much less gravity: about 0.14 gee (though it does receive about 1/12 as much light as Mars). Mars would lose atmosphere faster than Earth, but it would still do so at geological rates.
* Higher gravity means less need for strength training to stop bone loss and other problems
We really have no idea how much will be required. It may only be necessary to strength train a short period before returning to Earth.
* Partial natural radiation shielding
That exists in both places...the Moon has plenty of dirt that makes pretty good shielding.
* Ample known water supplies (moon ice is currently only speculative, despite plenty of lunar-orbit studying)
The lunar soil contains large amounts of oxygen, and large amounts of hydrogen will need to be supplied anyway for power. Burn the hydrogen with the oxygen in fuel cells. Use some of the water that results for the inhabitants, and once you have large amounts of solar power, you can electrolyze the rest back into hydrogen and oxygen for fuel during the lunar night.
* Cheap to get bulk raw materials to anywhere we care about. Even cheaper to get raw materials to Earth than it is from the moon, due to the orbital energy of the moon that needs to be overcome.
A direct transfer orbit from Mars orbit from Earth might be cheaper. The moon would probably be cheaper using other trajectories. In any case, you don't really want to send the materials to Earth, you want to send them elsewhere in space.
* Ample sunlight for farming; artificial light for farming is a pretty doomed concept, when you do the energy calculations.
The moon has more, but you would probably want an orbital farm, because providing light during the lunar night would be a pain. Providing supplementary food for a small number of people would not use an impractical amount of power.
* Partial-pressure domes
The pressure difference between the interior and outside will be nearly the same. The Martian atmosphere is very thin.
* Far more mineral rich in every respect except for Helium-3, which is currently pretty worthless.
The minerals are highly oxidized. The moon has significant amounts of reduced metals. A solar furnace could vaporize these to extract the desired metals. Mars receives far less light from the sun, making this kind of high-energy processing more difficult.
* A perfect stopping point for a triangle trade with the incredibly mineral rich asteroid belt (Mars raw materials and people can get to the asteroid belt with very little energy; asteroid belt materials get sent to Earth; Earth sends small, high tech components that Mars can't build to Mars).
Phobos and Deimos, maybe. A large asteroid in an elliptical orbit that takes it close to the orbit of Earth and the belt would be even better.
* Major terraforming prospects; estimated workforce needed to terraform Mars to 1atm=10,000 people; procodes enough pressure and CO2 for plants, which over about 100 years can produce enough O2 for humans to breathe.
You severely underestimate the requirements for terraforming Mars.
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I'm sure they already know. Notice that they use a traditional ground-launch system for larger payloads or higher orbits.
Launching from a plane gains you a small bit of altitude and a tiny bit of initial velocity. The altitude is almost irrelevant...a ground launched rocket will pass that altitude at far greater speed very early in its launch....and the speed boost is tiny, even supersonic speeds are far lower than orbital speeds. At a guess, I'd say their main cost savings is the flexibility in launch locations...practically anywhere the carrier plane can take off from, allowing them to more easily achieve high inclination or equatorial orbits. They also don't have to build, maintain, or rent massive launch installations for these launchers.
Orbital rockets are big, heavy, and fragile, and launching one from a stable ground platform is hugely easier than launching from a flying aircraft. The heavier structure required to survive launch from an aircraft probably outweighs any fuel savings, and the heavier structure and first stage aircraft together would almost certainly cost more...fuel is cheap.
For the X Prize, it's a big deal because all they needed is altitude...they could get about halfway to the goal on an ordinary aircraft. Orbit is a lot harder to reach, not only do you need altitude, you need a great deal of speed that no airplane can come close to achieving. Aircraft simply aren't very helpful for getting to orbit.
It is a problem, due to Coriolis effects. Basically, get up too quick and you'll fall over. We could probably get used to it in time, but generally, the larger the radius and slower the rotation, the better. However, plants are unlikely to care, so you could just use a spinning shelf arrangement for the gravity-sensitive plants. It wouldn't have to be too complicated, just a squirrelcage type mechanism.
For humans, the best idea is probably to attach a counterweight to the inhabited section with a long cable. You could get a really huge radius of rotation that way with little material, it's extremely mechanically simple, and it doesn't involve sending huge amounts of material into orbit. The counterweight could be equipment that doesn't need constant human presence, or hazardous equipment such as a nuclear reactor. (With a long enough cable, you wouldn't need shielding for it.)
The electrode array's a couple millimeters on a side. It'd be like a really tiny stroke.
Of course, a full blown version would probably have electrodes scattered around the brain. In that case, anything ranging from seizures to death is possible. However, I really don't see something like this using a direct electrical connection. If I were designing it, I'd use an induction loop to transmit power to the internal electronics, and LED's under the skin to carry the detected signals. Rather than a plug, you'd just wear a headband. It would be impossible to apply any significant amount across electrodes. But I don't think brain interfaces will be seriously two-way for a very long time...brain output/audiovisual input is likely to work better for most purposes. Plant some little transducers in the inner ear, and strap your iPod on your head or around your neck...
When it goes nova, the white dwarf casts off most of the matter it gains, so it stays at nearly the same mass. However, the donor star is no longer fusing, so it cools and shrinks. As it becomes cooler and more compact, its "surface gravity" increases and the average molecular velocity goes down, both effects slowing the mass loss. It'll lose lighter elements preferentially, especially as it cools and heavier elements combine into even heavier molecules, while helium stays as single atoms and hydrogen mostly forms slightly lighter H2 molecules. (H2: 2 amu. He: 4 amu. CO: 28 amu. Higher molecular weight == lower molecular velocities at a given temperature, and lower rates of loss.) As a result, it ends up denser and with a higher surface gravity than typical objects of its size and temperature.
Also, only a tiny portion of the nova-expelled mass would be reabsorbed by the donor star, and most of that would again be lost to the dwarf. Actually, it seems likely that the energy of the extremely nearby nova would blast even more mass away from the donor star.
It's not fusing internally any more, so it's cooling down and shrinking. Its "surface" is deeper in its gravity well and colder, so it's not getting stripped away as quickly. The vampirism probably hasn't stopped, just become too small to detect.
Also, the thing probably has much higher concentrations of "metals" than typical brown dwarfs or gas giants...for a while, it was fusing, and it probably lost lighter elements to the white dwarf more easily.
How about storing (cold) antiprotons in a normal matter container? At short distances, the antiprotons would be repelled by the electrons in the orbitals of the neutral atoms. Maybe a cold antiproton-hydrogen mix would be stable for significant periods. To set it off, just jump an arc through it or something...ionize the hydrogen, freeing the protons to interact directly with the antiprotons. Result: lots of ionizing radiation, and more proton-antiproton annihilation.
Um...after the rocket burns out and before the vehicle gets deep enough back into the atmosphere to maneuver, it *is* a ballistic vehicle. (And so is everything in orbit, for that matter.)
It's still a suborbital vehicle...it leaves the atmosphere, but never achieves orbital or escape velocity. "Goes straight up, and falls straight back down" is a pretty accurate description of its trajectory...the horizontal component is practically zero compared to what is necessary to reach orbit.
190,236,576 miles is just barely over 2AU...I wonder if someone mistook the major diameter of Earth's orbit for its mean radius. Still a stupid error...if they didn't make an extreme conversion error, they completely screwed up the definition of the unit.
They do...but we also have computers that let us do even better by doing a transfer like this. One really big reason to do it this way is that we can do an extended mission rather than a short flyby. Mars and Venus have atmospheres that can be used for aerobraking, and aren't that far from Earth in orbital velocity. Mercury doesn't have an atmosphere, you have to carry enough fuel to do the entire job of insertion into orbit, which for a direct insertion into orbit around Mercury or any of the planets past Mars, is quite a bit of fuel...fuel which takes up mass that could otherwise be devoted to instruments.
I hear it too, I can tell a muted TV is on as soon as I enter a room. The horizontal sync frequency for NTSC is 15.75 kHz, I've always assumed it was coils or deflector plates vibrating at that frequency. I've never personally met someone who hears it, but they may just not have noticed it...normal hearing is supposed to go up to 20 kHz.
> What I don't accept is that clouds themselves are a product of bacterial colonies other than as a by-product from releaseing water vapor from inside their cellular structures. Water clouds would form even if the Earth were sterile of life.
Well, spores and other microbes could act as condensation seeds. Have a hard time getting bacteria in one droplet to produce more droplets though...just about the best you could hope for would be bacteria getting rained down, dried out, and then kicked back up as dust. Cloud-borne life would probably be transferred by air currents and droplet collisions, and would be unlikely to have a strong effect on cloud formation. Well, absorption of light by the bacteria could heat the cloud up, dispersing it or making it less likely to rain out, but they would be quite noticeable then.
Cellular automata often produce cloud-like shapes, which really isn't surprising when you think about it. And some aspects of cloud formation could be simulated with CA...they have some similarities. The cloud is a group of tiny droplets condensed out of the air, the vaprous water is the "food", the droplets are the "cells". However, fluid dynamics makes a better cloud simulation...you get similar effects in many fluid systems, without any chemistry (organic or otherwise) involved. Clouds are simply caused by fluid dynamics and temperature/phase changes.
Clouds are complex systems that show some aspects of life, but none of a living organism. However, they could make a good home for microbial life.
As far as I can tell, this is basically an overly complex version of a momentum wheel...basically, a massive, low-speed flywheel. Spin it one way, the surrounding structure spins the opposite direction...stop the momentum wheel, and the entire structure stops spinning. That is, angular momentum for the entire structure is conserved.
The Hubble telescope uses momentum wheels for very precise aiming without requiring propellant and complex, failure-prone, and mirror-dirtying thrusters. These people are trying too hard...the basic idea is just a massive wheel attached to an electric motor.
This seems to be a common misconception. The solar wind is not a blowtorch that blasts any unprotected atmosphere into space. It will very slightly increase the rate of atmosphere escape, but it will still happen so slowly that it will probably not make a difference until after the sun ages enough to render Earth uninhabitable anyway. We have one big counterexample to that theory...Venus has slightly less gravity than Earth, and virtually no internally generated magnetic field, only a barely detectable one induced by the sun. It also receives over 1.9 times as much solar radiation as Earth, and over 4.4 times as much as Mars, yet its atmospheric pressure is 90 times as high as that of Earth...that's about 12000 times as much as Mars. Mars has little atmosphere because of its formation...it likely lost some gases that would have formed its atmosphere to Jupiter, and got more blasted off its surface by bombardment from the forming asteroid belt. Then it cooled, and a big chunk of its atmosphere froze...Martian atmospheric pressure actually varies highly depending on season, due to sublimating and freezing CO2.
In addition, the Earth's atmosphere makes an excellent shield against charged particles...there will likely be a slight increase in secondary radiation, but not enough to cause measureable effects on Earthly life.
In addition...it was mentioned that U238 has a half-life of four billion years. This is a *good* thing...as you mentioned, it decays very slowly, giving off very low amounts of radiation in any reasonable period of time. It's the medium-life isotopes you have to worry about, the ones with half-lives long enough to stick around a while, but short enough to produce high amounts of radiation.
As for the pyrophoricity...aluminum is pyrophoric. Make a large pile of aluminum powder, and you risk it spontaneously igniting in a very, very hot fire, especially in a slightly damp atmosphere. (The water loses oxygen to the aluminum, producing heat and hydrogen. You get a pile of hot, flammable metal with high internal concentrations of hot, flammable gas.)
Another metal known for flammability is magnesium...which doesn't need to be finely divided, it can burn in bulk quantities (though it isn't easily ignited in that state). Guess what...aluminum-magnesium alloys are in common use, and are not known for bursting into flame.
> I was wondering, it seems people who die from radiation do so because their body rejects itself since it's been popped full of tiny holes. Would it be possible to save more people with radiation exposure by pumping them full of anti-rejection drugs or shutting down their immune system somehow?
That's nearly the worst thing you could do. The problems don't arise from rejection, they come from ions and free radicals formed by the radiation impacting on the various chemicals in the body. A particularly unlucky hit can irreparably ruin a vital portion of DNA or cause enough damage to other cellular processes to kill the cell. If this happens a lot, you die from the toxic byproducts of the dying cells, and from the loss of cells that you really need. A very unlucky hit only modifies the DNA in such a way that the cell loses control of its reproduction...if the immune system doesn't detect the problem and kill that cell and all its descendants, you develop cancer. To make it all worse, your immune system is weakened by cell damage and the need to cope with all the junk floating around the system, leaving you more open to both infection and tumors caused by mutated cells.
For extreme radiation exposure, what you want is antioxidants, immune system *boosters*, lots of fluids, and other support to keep your kidneys and liver from shutting down under the load. And fortunately, although large amounts of radiation exposure do increase the risk of cancer, it is still very unlikely. If you do get cancer, it was probably due to something else.
Even if it is 1/3 as reliable...they could put 3 redundant systems in place and still pay only $3.9 million rather than $100 million. And have plenty of spare parts to swap around...3 systems would be more than 3 times as reliable, as the redundant systems on the ISS recently showed. (Machine 1 has faulty part A, machine 2 has faulty part B, rip part A out of machine 2 and you can have machine 1 working again.) More mass to lift into orbit, of course...it's a minimization problem. However, government projects often seem to miss this, going for a slight improvement in reliability at a large cost increase when more redundant lower reliability components would do just as well at lower cost. Of course, there are some times where you just must have the highest quality possible...
What electricity? It conducts electricity, it doesn't generate it...you would have to bring your conductive clothes into contact with an already dangerous exposed source, which clothes made of insulating fibers would be no guarantee of protection from. And even then, the danger is almost entirely due to electricity passing through the core of the body, which it is unlikely to do when said core is surrounded by a far better conductor.
Really, your complaints remind me of a comment I once heard while I was working on some electronics by someone who was worried a short length of wire that wasn't connected to anything was in danger of electrocuting me. Don't you realize that most jewelry is made of conductive material? Silver is the best metallic conductor there is, and gold isn't far behind copper.
Conductivity != full of electricity.
The dark areas thought to be ethane oceans turned out to be water ice discolored by organic impurities...this does not mean there is no liquid on Titan. In fact, the article specifically refers to liquid rain, though I don't see any references to this on the nasa.gov site.
However, if you do see hail on Titan...the surface gravity is just 0.14 times that of Earth, and the atmosphere 1.6 times as thick. Unless methane ice is much more dense than water ice, hail would fall much more slowly. It would look like slow-motion, and unless the hailstones grow very slowly, the hail could get quite big. Sounds like something that would be very interesting to see...
Another rendering system that supports photon mapping is POV-Ray, the Persistance Of Vision Raytracer. Unlike Brazil, it is free, and although it is not Open Source, the source code is available, and you can distribute patches and, with some restrictions, modified versions.
To summarize,
Forward raytracing: traces actual photons through the scene from the light source, reflecting off/refracting through objects in the scene, and through the camera aperture onto the "film". You end up tracing many photons that will never hit the camera, and the results are blurry or grainy unless you use settings that are just impractical with current technology.
Backwards (traditional) raytracing: traces the light paths backwards, out through the camera onto an object in the scene. From there, rays are traced to the lights in the scene to check for shadowing objects. This works pretty well, but can not compute illumination from mirrored reflections or refraction. However, it can compute diffuse reflection, by tracing more rays to find the illumination of the surrounding scene. This is usually slower than scanline rendering, but produces very good results.
Photon mapping: forward raytracing (like that used in this project) is used to build a map of photons deposited on surfaces within the scene, which is then used in the illumination computations when the scene is rendered with backwards raytracing or scanline rendering.
> The lunar regolith doesn't allow light to pass through, and thus prevents effective farming. Humans aren't the only things that need shielding.
... in tightly locked-up forms that are not easy to process.
Actually, we pretty much are. Crops have a very limited growing season, long-term effects from mutations just aren't much of a worry for them. Filters to reduce the intensity (or simply an arrangment of mirrors indirectly lighting the crops) and cut out some UV will be sufficient.
> the Lunar soil contains large amounts of oxygen
You can get far by simply heating it, easier on the Moon than on Mars.
> Not on Mars; Mars has the hydrogen (the moon doesn't). What, you think we're going to be powering either site (which are expected to have refining) by shipping *chemical fuel*? Are you crazy? Have you looked at the math involved? It's ludicrous.
I thought I was pretty clear that it would only use it for the setup power. Initially, it will require some form of power transported to the moon. The craft taking people and materials to the moon will require power. This all results in a significant amount of water being taken to the vicinity of the moon.
Mars does have the hydrogen, but it also has less than half the amount of sunlight per square meter.
Your entire argument about farming is ridiculous...I specifically said supplementary food. You ignore the fact that the growing season is only a small portion of the year to inflate the figures, and I have no idea what crops you were thinking of. The oxygen would be provided by a solar furnace during the day, not an electrical Brazilian alumina smelter on demand.
> It's an issue of shielding. A partial pressure dome for farming wouldn't work on the moon for farming because of radiation.
A double-layered translucent dome (to help regulate the temperature), plus Venetian blinds to provide a diurnal cycle for plants that need it would probably work just fine on the moon. As I said, crops probably don't need much protection from radiation, they certainly don't need as much as us.
> So you pick and choose which asteroids? I'm talking mining in general. The best asteroids aren't necesarily going to pass by Earth.
You chopped out the part which explained what I was talking about. The asteroid would have an elliptical orbit that comes close to that of Earth and the belt. Habitats would be built on the asteroid, which would then provide a means of safely transporting people between Earth and the belt. No need to go to Mars. Even if the delta-V is higher, the manned ships have far shorter trips to make, and can greatly cut down on shielding.
A comets tail is very thin, and the gravity of a comet is practically zero. Titan and Mars are giants compared to comets.
As for the magnetic field of Saturn...Titan actually sometimes passes outside the Saturnian magnetopause. Being within the magnetic field is no guarantee of protection either: like Earth, Saturn has radiation belts, which may intersect the orbit of Titan.
Venus has a magnetic field about 0.000015 times as strong as Earth's, probably resulting from interactions between ions in its upper atmosphere and the solar wind. And I extremely strongly doubt that volcanic activity can account for an atmosphere on a roughly Earth-sized planet which is 90 times as heavy as that of Earth.
The magnetic field is not the reason for the thin atmosphere. Venus also has no significant magnetic field, slightly less gravity than Earth, receives far more solar radiation (nearly twice that of Earth, about 4.46 times that of Mars), and its surface atmospheric pressure is about 90 times that of Earth. Titan's atmosphere, mostly nitrogen, has a surface pressure 1.6 times that of Earth, and much less gravity: about 0.14 gee (though it does receive about 1/12 as much light as Mars). Mars would lose atmosphere faster than Earth, but it would still do so at geological rates.
* Higher gravity means less need for strength training to stop bone loss and other problems
We really have no idea how much will be required. It may only be necessary to strength train a short period before returning to Earth.
* Partial natural radiation shielding
That exists in both places...the Moon has plenty of dirt that makes pretty good shielding.
* Ample known water supplies (moon ice is currently only speculative, despite plenty of lunar-orbit studying)
The lunar soil contains large amounts of oxygen, and large amounts of hydrogen will need to be supplied anyway for power. Burn the hydrogen with the oxygen in fuel cells. Use some of the water that results for the inhabitants, and once you have large amounts of solar power, you can electrolyze the rest back into hydrogen and oxygen for fuel during the lunar night.
* Cheap to get bulk raw materials to anywhere we care about. Even cheaper to get raw materials to Earth than it is from the moon, due to the orbital energy of the moon that needs to be overcome.
A direct transfer orbit from Mars orbit from Earth might be cheaper. The moon would probably be cheaper using other trajectories. In any case, you don't really want to send the materials to Earth, you want to send them elsewhere in space.
* Ample sunlight for farming; artificial light for farming is a pretty doomed concept, when you do the energy calculations.
The moon has more, but you would probably want an orbital farm, because providing light during the lunar night would be a pain. Providing supplementary food for a small number of people would not use an impractical amount of power.
* Partial-pressure domes
The pressure difference between the interior and outside will be nearly the same. The Martian atmosphere is very thin.
* Far more mineral rich in every respect except for Helium-3, which is currently pretty worthless.
The minerals are highly oxidized. The moon has significant amounts of reduced metals. A solar furnace could vaporize these to extract the desired metals. Mars receives far less light from the sun, making this kind of high-energy processing more difficult.
* A perfect stopping point for a triangle trade with the incredibly mineral rich asteroid belt (Mars raw materials and people can get to the asteroid belt with very little energy; asteroid belt materials get sent to Earth; Earth sends small, high tech components that Mars can't build to Mars).
Phobos and Deimos, maybe. A large asteroid in an elliptical orbit that takes it close to the orbit of Earth and the belt would be even better.
* Major terraforming prospects; estimated workforce needed to terraform Mars to 1atm=10,000 people; procodes enough pressure and CO2 for plants, which over about 100 years can produce enough O2 for humans to breathe.
You severely underestimate the requirements for terraforming Mars.