Re:Unknown Error In The Submission
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Nuclear Batteries
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· Score: 2, Insightful
Whereas, my opionion (and I believe CT's) is that since this is no better or worse than the current situation (and we believe it might be slightly better due to greater awareness & Federal regulations during manufacture), that we should go for it in order to gain the technological advantages of the new batteries.
I actually think that putting radioisotope-based power sources in the hands of consumers is not a good idea, because of the disposal problem. The existing controls on radioactive waste will, fortunately, ensure that this won't be done. What I expect to happen instead is more or less what the original article proposes - use of radioisotope power sources in specialized applications (like automobile black boxes and long-term sensors) where you _can_ control the lifecycle. I don't think that we'll see many problems on the _manufacturing_ side of things, because of the controls (in North America especially, as having a radiological accident there is a financial and liability nightmare).
For consumers, fuel-cell based technologies should provide more than enough power to satisfy intermediate-term needs and emerging applications. They're a little fussier, but have far less stigma attached, and their disposal problems are no worse than those of batteries.
My objection to Doc Ruby's posts is that they're semi-coherent rants that are guilty of exactly the crime he accuses others of - endorsing an extremist position without being swayed my mere facts (in this case, the fact that radioisotope waste isn't any deadlier than chemical waste, in the scenarios being discussed).
breathe particles in, for example, and you're fvcked. this is high school stuff.
Quantity matters. You're already beathing carcinogenic car exhaust and second-hand tobacco smoke, as well as lovely alpha-emitting radon from natural sources.
The important number to find is "amount of material needed to provide a larger carcinogenic effect than you're already receiving". As with so many other situations, "relative risk" is a concept that most people don't seem to grasp.
Re:Unknown Error In The Submission
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Nuclear Batteries
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· Score: 1
I'm not sure adding beta/alpha emitters into the environment is a step in the right direction. I suspect (but haven't done the research) that the heavy metal characteristics alone would be enough to tip the scales against. To my mind radio active materials belong in nuclear reactors.
Neither nickel nor hydrogen (of which tritium is an isotope) are heavy metals. Last I heard a fair amount of currency was nickel-based, and hydrogen is pretty hard to avoid with a water-based biology. Tritium will be mildly chemically toxic due to slightly different electronic structure than hydrogen, but this would only be relevant if you drank a few litres of tritiated water (at which point chemical toxicity would be the least of your concerns).
Re:Unknown Error In The Submission
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Nuclear Batteries
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· Score: 1
But what amounts of the tritium or the isotope of nickel could be tampered with and weaponized?
These are useless as direct weapons, as they're not fissile. They could conceivably be used as poisons, but there are chemical poisons that are a lot easier to come by and a lot worse.
I'd worry more about pollution problems during their life cycle. These problems are manageable, but have to be recognized in order to be managed.
Re:Unknown Error In The Submission
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Nuclear Batteries
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· Score: 1
Is anyone in this thread actually paying attention? I'm not talking about the threat from the tiny radioactive doses in the proposed batteries. I'm talking about the threat from the larger, concentrated doses of pollution resulting from the manufacturing.
As compared to the massive amounts of lead, cadmium, and other goodies we're getting cycled through the system as a result of manufacturing chemical batteries? And the massive amount of radioactive crud that ends up in our atmosphere from the coal burned to recharge the NiCds?
These radiothermal batteries aren't intended for consumers. They're intended for long-term monitoring devices, like scientific instruments and black boxes in cars. There are much, much better controls on disposal for this kind of thing than for consumer goods.
Waste during manufacturing, you say? Apparently you aren't familiar with the hoops that have to be jumped through to get permission to manufacture anything that involves handling radioactive materials. You are watched like a hawk, and have to take *extremely* elaborate precautions to guarantee that materials won't get released during manufacture, even if accidents occur in the facility.
I talk about pollution, and I'm met with cries of "the batteries aren't that radioactive".
You apparently haven't been following all of the pollution-related threads attached to this article. Please do so.
Instead, you're constructing arguments for how some versions of traditional poisons could possibly be more dangerous than people expect.
You railed about Ni63 being far more toxic than mercury. I pointed out how exceedingly nasty mercury can be. I hope you've found this informative. Now troll elsewhere.
Re:Unknown Error In The Submission
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Nuclear Batteries
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· Score: 1
Sorry to contradict you, but pure mercury and methyl-mercury are two quite different things. At the uni where I study, if we break a thermometer it's "lock the drawer and clean up later". If 1/2mL of methyl mercury was spilt, we would evacuate the building and send in the HAZCHEM team.
I realize that, which is precisely why I used it as an example instead of elemental mercury. There's this bizzare perception that nuclear materials are more toxic than anything chemical, which is very demonstrably not the case:).
But we already agree on that.
Re:Seems extremely difficult with chemical rockets
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After the X Prize
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· Score: 1
But aren't there several factors working in favor of this being realistic?
Arguably, but I'm still not convinced, for anything near-term.
1) There is no specific requirement for ground launch. It seems that most of the X-Prize contestants have taken good advantage of this.
2) The cargo weight of this competition is relatively low. 7 adults isn't peanuts, but we're not trying to haul Hubble up there as well.
I'm grouping these, because they're related. The problem is that you need a fuel fraction of around 95% to reach orbit (the SS1 was something more on the order of 50%, if I understand correctly). Most of this will be structure, because the fuel tanks are big. A 2% cargo fraction is IMO extremely optimistic, with 1% being closer to reality. If we say around 70 kg per adult (pretty light), that gives around 500 kg of cargo, bare minimum. That gives a bare minimum craft mass of 50 T or so. Lifting that into the upper atmosphere will be quite tricky. The C-130 Hercules transport plane, by comparison, can carry slightly over 11 tonnes (metric, before anyone claims 12.5 tons). Its altitude ceiling is about 10 km, which is nice, but something like 20 km would be nicer (much thinner atmosphere).
A high-altitude launch is probably required for a craft as light as 50 T, too. It has to plow through 10 T of atmosphere (or more) per square metre of cross-sectional profile area if boosting from sea level. Unless craft profile mass density is much greater than this, it'll suffer considerable losses due to atmospheric drag. Launching at 10 km and 20 km reduces this to about 2.2 and 0.7, respectively. With a very cramped capsule and extremely narrow aspect ratio, you might be able to do a sea-level launch.
Realistically you're going to want something that can lift five times as much as the C-130 to the same altitude. I'm not convinced that that's cheaper than using a larger spacecraft.
3) There is no requirement for extended mission duration. So minimal life-support weight. This is a taxi, not a flying laboratory.
While this is true, it doesn't strongly affect my argument. This is still a very small rocket by spacecraft standards; it's just a lot bigger than SS1.
4) There continue to be fairly substantial progress in materials development.
This is the only thing that I can think of that would make such a craft small and cheap enough to be competitive with existing launch options. The threshold required for real progress to be made is far lower than that needed for, say, a space elevator. We're reasonably confident space elevator grade materials will be mass-produceable within 20 to 40 years, so smaller and cheaper rockets should show up well before then.
So, the X-33 demonstrated that reusable ground to orbit for a crew was feasible on paper (given a minimum $1B budget) and that this is an incredibly challenging task. But a decade of additional research, removing NASAs overhead and over-engineering, and a much more flexible set of design constraints, and I think you'll see some decent goes at it.
The X33 failed partly because of mis-management (arguably), but in large part also because it was trying to succeed at an extremely difficult task (SSTO is not anything I'd like to place money on being practical or (especially) cost-effective for chemical rockets any time soon). We've made considerable materials progress in the last decade, but the pace of change drastic enough to change the engineering picture is slower than that.
We'll get there, especially if we're just trying for multi-stagers with a better mass fraction. However, it'll take time. Look to the cargo-lifting companies for the real improvements, here (they have lots of volume and a shorter production cycle, compared to man-rated lifting).
Remember, the X-Prize won't cover the development for anyone - it's a subsidy. Scaled Composites is really after the licensing deal that happened with Virgin, it should be far more
What I don't understand is why they went with the electromechanical scheme that they used, instead of epitaxially depositing a big stack of P-I-N diodes and letting the ionizing radiation work its magic directly. The article mentions a single-layer diode test, but you want a big enough stack to sap charge from the entire trail left by the alpha or beta particle that's plowing through the device.
The electromechanical scheme has the virtue of collecting almost all of the energy as (nominally) usable heat, but conversion efficiency stinks, from what I can gather. Junction efficiency won't be so hot either (for the same reason solar cell efficiency is poor - carriers are given more energy than required to overcome the band-gap), but not too bad (anything over 10-15 eV will just create secondary showers of lower-energy electrons).
Can anyone familiar with these issues tell me what I'm missing?
In case anyone is wondering how these work, the idea is that the radiation from a small amount of radioactive material (NOT fissable material!) is captured and converted into electricity or other forms of energy. There is very little radiation emitted by these devices, because the radiation IS the power! Letting it escape would be poor economy.
The problem is contamination concerns during fabrication and as a result of accidents in the field as the devices are used, and especially due to disposal. Any single battery's radioactives won't make that big a mess, but it adds up. Look at how much fun we're having with all of the cadmium floating around from NiCd batteries.
Recycling and taking proper care can reduce or remove the problem, but the fundamental issue is that over the counter batteries are being put in the hands of people who just don't care very much about being responsible even when they know what they should be doing. A battery capable of generating useful amounts of power needs a _lot_ more radioactive material than a smoke detector, and has correspondingly larger waste concerns.
Re:Unknown Error In The Submission
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Nuclear Batteries
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· Score: 1
No, I live in the environment, which keeps getting polluted, behind the Pollyanna talk of safety. Mercury, though poisonous (as I stated when I introduced it to this discussion), is *less* poisonous than radioactive materials like they're considering for these batteries.
Look up the MSDSs for nickel 63, and, oh, let's say "methyl mercury". You will be enlightened.
Here's another hint. Look up how much radon you're inhaling from natural sources, especially if you spend any time at all below ground level. That gives you a rather enlightening ballpark figure for the "natural" background for ingested/inhaled radioactives. If the cumulative doses you're talking about from other sources aren't very substantially larger, the claimed effects won't be statistically significant.
Re:Seems extremely difficult with chemical rockets
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After the X Prize
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· Score: 1
Funny, that's the same thing they said about the X prize... the problem is too big for such a meager prize.
Fortunately it's not really about the prize money.
The problem is that lifting things to orbit is an expensive enough proposition that the barrier to entry for building a launcher is very high. You won't do it unless you have clients willing to pay a lot of money, probably at low volume. The market is also already saturated, unlike the sub-orbital tourism business, with many players and competitive options for cargo launching, and even solutions for non-government man-rated launches (we've been hearing about space tourism through the Russian space agency for years).
So, I'm not sure what this prize is supposed to be encouraging people to do. The companies and other entities in a position to offer man-rated launches either already are, or have decided that it's not in their best interests to do so at this time.
This will remain the case until the nature of ground-to-orbit travel changes (e.g., if someone builds a space elevator or a laser launcher). Both of the examples I give in this paragraph are already being actively investigated, and arguably pursued with some chance of results. The prize addresses neither (I'm pretty sure wording will rule out a scheme with remotely supplied power, though I'm not certain of this).
Seems extremely difficult with chemical rockets.
on
After the X Prize
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· Score: 5, Insightful
Although the energetic requirements are an order of magnitude higher for orbital spaceflight, this $50 million prize is almost an order of magnitude higher than the $10 million X-prize. The economic payback seems higher as well, since there are lots more reasons (both reasearch and tourism) to go to orbit than there are in sub-orbital spaceflight.
The problem is that the increase in difficulty is far, far greater than the increase in either energy or delta-v required seems to warrant at first glance.
There are two regimes in which a rocket can operate. In one, the delta-v required for the mission is much lower than the exhaust velocity. In this scenario, fuel is only a small fraction of the total craft weight, and scales linearly with delta-v. This is the easy scenario, and it includes the X prize's "get a rocket to a relative altitude of 100 km".
The second regime, the hard scenario, is the one in which the delta-v required for the mission is much higher than the exhaust velocity. In this scenario, the craft weight is dominated by fuel, and the fuel-to-everything-else ratio goes up exponentially with delta-v. Truly exponentially, not the "this is a quadratic but I'm calling it exponential" variety that I see so often around here. Craft design goes from "really hard" to "damn near impossible" to "outright impossible" very quickly.
Ground-to-orbit is balanced right on the knife-edge of "really hard" and "damn near impossible", and that's only when we use multi-stage rockets. Reusable single-stage-to-orbit chemical rockets are well into the "damned near impossible" regime, even with the advanced composites we have now. If the earth was even a little heavier, we wouldn't be getting off of it with chemical rockets at _all_. Orbital velocity is about 8 km/sec, escape is 13 km/sec, and the highest-Isp chemical rockets have an exhaust velocity between 3 and 4 km/sec (with SS1 having one in the range of 2 or so).
There are ways that you can make the hard scenario marginally easier. One is to use multi-stage rockets, though that's generally pretty much _assumed_ past a per-stage mass fraction of 5:1 to 10:1. Another is to use high-Isp chemical fuels - but these make your craft far more expensive due to handling concerns, and in the limiting case this can even be counterproductive (H2 is a lousy fuel for anything that launches from deep in the atmosphere or under a lot of acceleration, due to low storage density and large tank size). Another is to use as small a craft as possible to take advantage of stress scaling laws, but a) that means an upper-atmosphere launch instead of a ground launch, and b) your minimum cargo weight places a lower bound on the craft weight.
The only realistic options for a 7-human manned craft are a big, expensive multi-stage chemical rocket with disposable boosters (because refurbishing to man-rated spec costs an insane amount of money), or an exotic craft with a high-Isp drive, to push the problem back into the "easy" regime. The only high-Isp craft we can build right now with the required thrust is one with a NERVA-style nuclear drive. A remotely laser-powered craft can work too, and we have a good idea how to build these, but full-scale engineering of these haven't been done yet. Orion is _too_ large scale, and would be even less popular than NERVA.
So, I don't expect any vehicle-based solution to be easy to build or cheap enough to run to make the prize offered a significant attraction.
A single-passenger craft would be much easier, due to reduced craft mass (materials scaling, again).
But curiously, drinking deuterated water is apparently poisonous.
This is because the chemical behaviors of deuterium and light hydrogen are slightly different.
You can think of the electron and nucleus co-orbiting about a common centre of mass, rather than the electron orbiting while the nucleus remains fixed. Where the point is depends on the ratio of the masses of the electron and the nucleus (about 2000:1 for light hydrogen, and about 4000:1 for deuterium). The different orbit radius (for any given energy) for each case means that the energy level at which the orbit circumference is an integer number of electron wavelengths will be different for deuterium and light hydrogen.
This means that the energy structure of the electron shells is slightly different, which means that they will behave slightly differently chemically. This fact is exploited in some of the methods of isolating heavy hydrogen from light hydrogen (electrolysis method, as the reduction potential is different, and the more common chemical method involving forming hydrogen sulphide, as the rates of reaction are different).
In the case of ingestion, deuterium's chemical behavior is similar enough to that of hydrogen that it gets incorporated into chemicals and otherwise interacted with as hydrogen would be, but different enough that it mucks up some of these reactions. Result, poisoning, much as you get from heavy metals displacing their chemical analogues (though less so, because D and H are a lot more similar, and your body cycles hydrogen through itself pretty quickly, while metals tend to accumulate).
As far as hydrogen isotopes go, though, tritium is the main concern. It's a beta emitter, and is formed in water-cooled reactors (especially the heavy-water-moderated reactors Canada uses, as only one transmutation step is required instead of two). It's a very low-energy emitter, but if ingested, will still cause problems. It's less nasty than most contaminents, though, as hydrogen gets cycled through the body very quickly, and tritium has a half-life of about a decade (short enough to disappear within a lifetime, long enough that it cycles out of the body without depositing much of its radiation dose).
Deuterium is mildly chemically toxic, but is not radioactive.
As long as there are a significant number of people who *like* to drive a car, autopiloted cars will be an alternative to, not a replacement for, conventional ones, in the same way that automatic gearboxes have been around for 50 years and still havnt made manuals extinct
Fair enough. However, it will be rare, as it takes years of training to learn how to drive adequately, and will cost money (in the form of higher insurance) to drive manually. The vast majority therefore won't.
The nature of driver training would also change. I'd expect it to become more like getting a pilot's license, where you do a large amount of training under very close supervision, as instead of having to demonstrate that you drive as safely as most humans on the road, you'll have to demonstrate that you drive as safely as most _autopilots_.
You'd also be limited in where you'd be able to drive, as there would be high-traffic areas that need a computer's group-think and precision to navigate (allows for better optimization of traffic flow, which means less expense building/widening roads, so these would exist).
Still, good observation. At minimum, you'd always have company-based human drivers to remotely drive in situations where car AIs have difficulty (per my other reply in this thread). And your point about hobbyists/enthusiasts is quite valid.
I don't see a practical autopilot happening any time soon. I see how it'd work on a freeway, but what about construction zones?. Lanes get closed or reversed. You might have to follow the hand-made directions of the repair crew. A turn might be changed temporarely into a really weird angle that only human perception is nowadays able to descipher.
This is why the "manual override" ability would still be present, for the intermediate term, at least. The autopilot would be set up to by default stop instead of proceeding into an area with features it couldn't identify with confidence, or to proceed only on paths that it _could_ confidently identify (e.g. not making that wierd turn, but instead proceeding with through-traffic and looking for an alternate route).
I'd expect construction crews to be issued ai-comprehendable instruction beacons for strange cases like that. Or even for simpler solutions to be implemented, like standardized symbols indicating what traffic is to do in construction zones (we're most of the way there already).
The point is that the system can be made to fail gracefully (and safely) under these conditions, and that the merits of the system (fewer accidents, insurance benefit) will eventually still outweigh this inconvenience.
In a world where people can still drive manually, falling back to manual override isn't a problem. In a world where people no longer know how to drive, your autopilot would be sold with a contract to a human-staffed agency that would take over and remotely drive for you under conditions where you decided that you _had_ to drive through a region the AI couldn't handle.
By the time we can handle this kinds of things properly, the fact that drives can drive themselves would not be all that important compared to other applications of the image processing and AI technnologies.
Never underestimate what an expert system can do, or how big the gap is between an expert system and a true AI. I think we'll have the required robust image processing algorithms a lot sooner than we'll have robust AI (arguably we already have them; image processing as a field is many decades old). And, as mentioned above, the autopilot only has to work optimally _most_ of the time, as long as failure is both safe and graceful.
In summary, I believe that a useful autopilot system could be built considerably more easily than you think.
Actually the cable seems quite safe even if part of it "falls". Please read the FAQ before such wild speculation.
This depends entirely on how massive the cable is. This in turn depends on how useful you want it to be. It takes a long time to get up the cable (one week for Liftport's version). Your cargo capacity is directly proportional to the cable mass (anywhere from 10% of the cable mass to around 1x the cable mass, depending on the safety factor you build into the cable). Divide to get the rate of mass transfer (5T per day, for Liftport's version).
The key virtue of a space elevator is that it lets you transfer _large_ amounts of mass cheaply. You'd use it for lifting mass for a starship, or for a Stanford Torus colony, or for something even bigger. If you're only sending up a few tonnes of mass per day, you don't capitalize on the benefits of having a space elevator in the first place. Lift costs will have to be much higher to amortize the cost of construction and maintenance, and the stuff you're sending up tends to be very expensive - expensive enough that paying $20,000/pound for a conventional launch isn't a big problem.
For the big construction applications - where you have to send a million tonnes of material a year, as fuel for your interstellar probe or structural material for your space station - you need a cable with a mass of hundreds of thousands of tonnes. In a worst-case accident, where the cable is severed in the middle, the energy of the impacting portion is about 10 times the equivalent weight in TNT. A cable this massive (even a multi-strand cable) stands a good chance of reaching the ground and doing damage, atmosphere or no atmosphere.
There are steps you can take to mitigate this risk - have a multistrand cable with strands separated by significant distance, and webbed so that the failure of any given strand just transfers load to other strands - but it's still awfully easy to induce failure in the whole cable, especially with the cheap access to space that the elevator gives. All it takes is an ion drive, a bit of patience, and a few big spools of iron chain.
In summary, the problem exists. Liftport only gets around the problem by severely limiting the usefulness of their elevator.
No, they won't aim for me. However, the semiconscious retard behind the wheel would have the pathetic excuse of "mechanical/electronic failure" keeping him from prison time when he accidentally mows me down with his H2.
He will then have to explain why "there's a pedestrian, for the love of God *stop*!" shows up in the logs and he chose to ignore it (or override the vehicle's automatic "stop before hitting $object" reflex). Black boxes _do_ have legitimate uses.
Two things that won't happen next year, but that will happen in the intermediate future and have very interesting consequences:
Cars will be autopiloted, with driver controls as a manual override only.
A lot of progress has been made on this over the past couple of decades, and we have a couple more decades of progress to go before it's safe enough to use in the real world, but as soon as an autopilot is invented that drives better than the average human (especially under emergency conditions), there will be a large insurance break for using it. Shortly after this it will become the norm.
Useful, cheap, and robust renewable fuel technology (electric or combustion based).
My money's on methanol or methane, as both can be stored as liquids (methanol more easily), and methanol can be burned in a conventional engine with a bit of tweaking (making the switch from internal combustion to electric engines much more graceful). You even have interesting hybrid options available, like an electric car with a gas turbine burning methane (or propane, which you can fill up with at gas stations now, making the switchover to _methane_ easier). Methane and methanol can both be synthesized directly from water, CO2, and electricity, meaning that they're suitable fuels for an electric vehicle infrastructure after fossil fuel supplies of them run out (and after we need more than we can get by reclaiming biological waste). We have lots of experience with moving hydrocarbon gases and volatile liquids around, so the transport infrastructure's already here. Methane and methanol have nowhere *near* the storage and handling problems hydrogen has.
It'll be interesting to see when the first point happens (I think it's pretty inevitable that it's going to). A methanol (or a methane) fuel system might or might not happen. If compact energy storage and vehicle efficiency get good enough, a direct electric scheme might work. However, most non-chemical methods of electric storage don't have high enough theoretical densities (even with nanotube-reinforced flywheels and induction rings), and a purely electric vehicle infrastructure is a lot harder to phase in gracefully. Alternatively, we might just keep improving our ability to harvest lower-grade and less-accessible hydrocarbon deposits, and push the fossil fuel problem far enough off that by the time the crunch hits, technology will be different enough to drastically alter the space of possible solutions.
Modulate a thousand frequencies of sunlight at the same time and pass them through your transmission medium of choice (space?) and don't stress about diffraction or diffusion as long as the light reaches the other side; because your receiver is an array of several tens of thousands of carbon nanotubes that auto-magically sort out the frequencies.
Ta-da! You just transmitted the entire Library of Congress in a matter of seconds.
The problem with using this for data transmission is that in order to measure amplitude accurately, you need several photons received in your measuring period. As frequency gets higher, the photons get more energetic and the sampling period (at the maximum rate of modulation) gets shorter. This results in power per unit data going up directly with frequency, and power per unit time going up as the square of frequency. The same relation turns out to hold even if you use other methods of signal processing (you could split the modulated light into its component frequencies and end up with a bunch of lower-bandwidth signals that way, for instance).
For signals modulated much more slowly than the frequency of the light itself, this penalty in power-per-bit may be acceptable if using light gives other advantages (like smaller dish size for a given divergence, or ability to pipe through fiber). However, at the maximum rate of modulation, both transmission power and power per unit area get prohibitive.
At one bit per sample (the most power-efficient encoding), you get a minimum power for an intelligeable signal of about 0.7 mW (1e15 samples of 4 photons at about 1 eV each). This is per nanotube antenna. This is unlikely to be survivable. For an 11 angstrom single-walled nanotube seen end-on, it corresponds to a power flux of about 7e14 W/m^2. At radiative equilibrium, this gives a surface temperature of around 300,000 K on your antenna array (room temperature is 300 K, nanotubes change phase somewhere between 3500 and 4000 K, and the surface of the sun is 5800 K). If you instead use the nanotubes side-on as antennae about the size of a photon's wavelength (around 1 micron), you get a power flux of about 7e8 W/m^2, giving an equilibrium temperature of around 8700 K (still hotter than the sun). This is misleading, though, as the signal would have to be coupled into a single nanotube antenna, with a much smaller surface area (giving a power flux on the order of 1000 times higher, and temperature 5-6 times higher).
Transmitting over interstellar distances is also very difficult, as you need to assume a collecting mirror size, and make sure that enough photons strike the collector to get an intelligeable signal. For a 10m telescope mirror, power needs to be about 9e-6 w/m^2. A broadcast signal at a range of, say, 10 light-years covers a surface area of about 1e35 m^2. This gives a broadcast power of about 9e29 W. By comparison, the sun puts out about 4e26 W. So broadcasting a beacon like that, even to a nearby star system, is impractical. Beaming it still covers a large area, due to divergence induced by aperture diffraction at the sending mirror. If we assume it's being broadcast from a 10 m telescope, divergence is about 1e-7 radian, for a spot diameter of 9e9 m. This gives a spot area of about 6e19 m^2, and a power of about 4e16 W (40 petawatts). A bit steep for a beacon, when you could save many orders of magnitude by either using radio, transmitting data more slowly, or both.
In summary, modulating data on an optical carrier has drawbacks, and doing it at optical data transfer frequencies almost certainly requires enough power to vapourize the detector. Still a nifty thought-experiment, though.
It's interesting that this should come up, as last spring or so, I was sitting on the presentation of a paper about doing this with far-infrared. Conventional lithographic techniques were used to make waveguides and rectifiers. Photons entering the wave guide caused currents when they struck the walls, which were picked up and rectified by interesting devices that worked by exploiting ballistic electron transport (looked like a wedge inside a T-joint; electrons flowing in one direction were preferentially scattered).
Frequency limit of this technique was related to the sizes of their structures, but I didn't get the impression that it would work at optical wavelengths. Still very nifty, though.
[The paper was presented at CCECE 2004, but I'm having difficulty finding a citation.]
On the other hand analog signals degrade gracefully. Even when you can only see 10% of the total image, you're looking at 10% of the whole thing, not 1/10 the frames or 1/10 of the picture. A little interference in a digital video stream makes the picture "jump" and may cause bizarre audio artifacting as well. A little interference in an analog video stream shows up as static, color that's "off", et cetera.
Degradation effects depend very strongly on how the data is encapsulated. When redundancy and precacheing are added for important parts (e.g. most important spectral components of the image, if we're doing lossy compression, and most important components of the audio), then noise and interruptions in the stream cause degradation that's at least as graceful as with analog TV. Argubly more graceful, for a well-defined protocol, as you get to pick which components you want to preserve at all costs, while in analog transmission, you're limited by the fact that you're displaying frames and pixels in a predefined sequence determined by old TV hardware.
There was an excellent demonstration of a scheme like this intended for mobile phones at TechCon 2003. That one worked by pretransmitting voice and key-frame data for a news clip, giving decent-looking and sounding results even when streaming was terminated half way through the broadcast.
In summary, digital transmission at least in principle gives you far _better_ degradation qualities than analog, because you can choose important features and make sure they arrive no matter what.
I'm waiting for TV via Wifi. Oh wait, I guess TV already is wireless.
I know this was intended to be a joke, but the advantage to using a digital streaming protocol for video over wireless is that you can at least in principle handle signal degradation and dropouts a lot better than you can with plain old analog TV. I know _I_ got tired of doing the "wave the rabbit ears around until it looks almost-decent" thing.
Furthermore since when does capitalism display dignity and display wisdom?
All the time, provided there are no artificial limits placed on it.
The forced economic classes that it creates can only be called dignifying to the rich and the quickly shrinking remnants of the middle class.
Wasn't always that way. There actually used to be a middle class back when people had careers instead of temp jobs. Almost anyone who put in a day's work could earn an honest wage and afford a home. Now, the median price for a home is almost a half million dollars and the average job lasts less than 18 months.
I am having difficulty reconciling your two statements, as both temp jobs and housing prices are a direct consequence of market forces at work. Yet, you seem to feel that they are undesirable, while the capitalism that produces these market forces produces predominately desirable results.
There will be no further significant space exploration because business decides everything and there are no money grabs available.
The "big business" which you take exception to is the natural end result of unfettered capitalism. A perfect capitalist entity acts to maximize its profit, and dominating a market, degrading produced value to the minimum that consumers will accept, and paying workers the minimum that they will tolerate, is the best way to do that. It is only _through_ artificial limits like anti-trust laws and labour laws that these harmful effects are kept in check (albeit imperfectly).
Over-regulation of business has its own problems, but a purely capitalist system with no artificial checks would very rapidly produce a _horrible_ quality of life for the majority (those who didn't come out on top of the pile when trying to amass vast wealth).
It's bad news for the space program either way, of course. There's nothing obviously profitable enough out there for business to want to go after, so in a money-dominated system, the space program languishes. We're also lacking a determined and sufficiently credible political rival going after space targets, so the government isn't going to strongly back a space effort in a government-dominated system. Even if scientists _could_ make an argument for it being a good research investment to send humans out to Mars (or even a LEO station), they don't have enough clout under either system to make much difference.
Big, flashy space projects will come back when China convinces the US government that it really might beat them to a moon or mars race within a couple of election terms, or when launch costs lower by enough orders of magnitude to make marginal or speculative payoffs attractive to business. In a few decades, either one might happen, but neither is the case now.
Cynical, aren't I?
Other lock-picking resources.
on
Steel Bolt Hacking
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· Score: 5, Informative
Second - as another poster noted, lock pins aren't typically made from high-strength alloys. A battery-powered hand drill (and a screwdriver to turn the lock when the pins are gone) is the best and fastest lock pick that there is. Didn't even leave any visible damage when I used this approach on a filing cabinet we'd lost the key to. Just pick a bit as wide as the key entryway, and drill down the line of pins.
Be advised that the lock tends to jam after closing again, as the remains of the pins fall back into their channels when the lock returns to its original position. But if you're drilling a lock, you're typically looking for a one-time solution anyways.
you obviously haven't seen "A Brief History of Time", "In Search of Schrodinger's Cat", "Schrodinger's Kittens" and many other non-maths physics books.
These are "physics books" the way "the matrix" is a computing and AI primer. That is to say, they tell you that several of the important concepts exist, in a way that's entertaining, but don't do much to tell you how to actually _use_ them.
At best, "physics overview for the layman", as opposed to "physics reference".
Slashdot Mirror
Whereas, my opionion (and I believe CT's) is that since this is no better or worse than the current situation (and we believe it might be slightly better due to greater awareness & Federal regulations during manufacture), that we should go for it in order to gain the technological advantages of the new batteries.
I actually think that putting radioisotope-based power sources in the hands of consumers is not a good idea, because of the disposal problem. The existing controls on radioactive waste will, fortunately, ensure that this won't be done. What I expect to happen instead is more or less what the original article proposes - use of radioisotope power sources in specialized applications (like automobile black boxes and long-term sensors) where you _can_ control the lifecycle. I don't think that we'll see many problems on the _manufacturing_ side of things, because of the controls (in North America especially, as having a radiological accident there is a financial and liability nightmare).
For consumers, fuel-cell based technologies should provide more than enough power to satisfy intermediate-term needs and emerging applications. They're a little fussier, but have far less stigma attached, and their disposal problems are no worse than those of batteries.
My objection to Doc Ruby's posts is that they're semi-coherent rants that are guilty of exactly the crime he accuses others of - endorsing an extremist position without being swayed my mere facts (in this case, the fact that radioisotope waste isn't any deadlier than chemical waste, in the scenarios being discussed).
breathe particles in, for example, and you're fvcked. this is high school stuff.
Quantity matters. You're already beathing carcinogenic car exhaust and second-hand tobacco smoke, as well as lovely alpha-emitting radon from natural sources.
The important number to find is "amount of material needed to provide a larger carcinogenic effect than you're already receiving". As with so many other situations, "relative risk" is a concept that most people don't seem to grasp.
I'm not sure adding beta/alpha emitters into the environment is a step in the right direction. I suspect (but haven't done the research) that the heavy metal characteristics alone would be enough to tip the scales against. To my mind radio active materials belong in nuclear reactors.
Neither nickel nor hydrogen (of which tritium is an isotope) are heavy metals. Last I heard a fair amount of currency was nickel-based, and hydrogen is pretty hard to avoid with a water-based biology. Tritium will be mildly chemically toxic due to slightly different electronic structure than hydrogen, but this would only be relevant if you drank a few litres of tritiated water (at which point chemical toxicity would be the least of your concerns).
But what amounts of the tritium or the isotope of nickel could be tampered with and weaponized?
These are useless as direct weapons, as they're not fissile. They could conceivably be used as poisons, but there are chemical poisons that are a lot easier to come by and a lot worse.
I'd worry more about pollution problems during their life cycle. These problems are manageable, but have to be recognized in order to be managed.
Is anyone in this thread actually paying attention? I'm not talking about the threat from the tiny radioactive doses in the proposed batteries. I'm talking about the threat from the larger, concentrated doses of pollution resulting from the manufacturing.
As compared to the massive amounts of lead, cadmium, and other goodies we're getting cycled through the system as a result of manufacturing chemical batteries? And the massive amount of radioactive crud that ends up in our atmosphere from the coal burned to recharge the NiCds?
These radiothermal batteries aren't intended for consumers. They're intended for long-term monitoring devices, like scientific instruments and black boxes in cars. There are much, much better controls on disposal for this kind of thing than for consumer goods.
Waste during manufacturing, you say? Apparently you aren't familiar with the hoops that have to be jumped through to get permission to manufacture anything that involves handling radioactive materials. You are watched like a hawk, and have to take *extremely* elaborate precautions to guarantee that materials won't get released during manufacture, even if accidents occur in the facility.
I talk about pollution, and I'm met with cries of "the batteries aren't that radioactive".
You apparently haven't been following all of the pollution-related threads attached to this article. Please do so.
Instead, you're constructing arguments for how some versions of traditional poisons could possibly be more dangerous than people expect.
You railed about Ni63 being far more toxic than mercury. I pointed out how exceedingly nasty mercury can be. I hope you've found this informative. Now troll elsewhere.
Sorry to contradict you, but pure mercury and methyl-mercury are two quite different things. At the uni where I study, if we break a thermometer it's "lock the drawer and clean up later". If 1/2mL of methyl mercury was spilt, we would evacuate the building and send in the HAZCHEM team.
:).
I realize that, which is precisely why I used it as an example instead of elemental mercury. There's this bizzare perception that nuclear materials are more toxic than anything chemical, which is very demonstrably not the case
But we already agree on that.
But aren't there several factors working in favor of this being realistic?
Arguably, but I'm still not convinced, for anything near-term.
1) There is no specific requirement for ground launch. It seems that most of the X-Prize contestants have taken good advantage of this.
2) The cargo weight of this competition is relatively low. 7 adults isn't peanuts, but we're not trying to haul Hubble up there as well.
I'm grouping these, because they're related. The problem is that you need a fuel fraction of around 95% to reach orbit (the SS1 was something more on the order of 50%, if I understand correctly). Most of this will be structure, because the fuel tanks are big. A 2% cargo fraction is IMO extremely optimistic, with 1% being closer to reality. If we say around 70 kg per adult (pretty light), that gives around 500 kg of cargo, bare minimum. That gives a bare minimum craft mass of 50 T or so. Lifting that into the upper atmosphere will be quite tricky. The C-130 Hercules transport plane, by comparison, can carry slightly over 11 tonnes (metric, before anyone claims 12.5 tons). Its altitude ceiling is about 10 km, which is nice, but something like 20 km would be nicer (much thinner atmosphere).
A high-altitude launch is probably required for a craft as light as 50 T, too. It has to plow through 10 T of atmosphere (or more) per square metre of cross-sectional profile area if boosting from sea level. Unless craft profile mass density is much greater than this, it'll suffer considerable losses due to atmospheric drag. Launching at 10 km and 20 km reduces this to about 2.2 and 0.7, respectively. With a very cramped capsule and extremely narrow aspect ratio, you might be able to do a sea-level launch.
Realistically you're going to want something that can lift five times as much as the C-130 to the same altitude. I'm not convinced that that's cheaper than using a larger spacecraft.
3) There is no requirement for extended mission duration. So minimal life-support weight. This is a taxi, not a flying laboratory.
While this is true, it doesn't strongly affect my argument. This is still a very small rocket by spacecraft standards; it's just a lot bigger than SS1.
4) There continue to be fairly substantial progress in materials development.
This is the only thing that I can think of that would make such a craft small and cheap enough to be competitive with existing launch options. The threshold required for real progress to be made is far lower than that needed for, say, a space elevator. We're reasonably confident space elevator grade materials will be mass-produceable within 20 to 40 years, so smaller and cheaper rockets should show up well before then.
So, the X-33 demonstrated that reusable ground to orbit for a crew was feasible on paper (given a minimum $1B budget) and that this is an incredibly challenging task. But a decade of additional research, removing NASAs overhead and over-engineering, and a much more flexible set of design constraints, and I think you'll see some decent goes at it.
The X33 failed partly because of mis-management (arguably), but in large part also because it was trying to succeed at an extremely difficult task (SSTO is not anything I'd like to place money on being practical or (especially) cost-effective for chemical rockets any time soon). We've made considerable materials progress in the last decade, but the pace of change drastic enough to change the engineering picture is slower than that.
We'll get there, especially if we're just trying for multi-stagers with a better mass fraction. However, it'll take time. Look to the cargo-lifting companies for the real improvements, here (they have lots of volume and a shorter production cycle, compared to man-rated lifting).
Remember, the X-Prize won't cover the development for anyone - it's a subsidy. Scaled Composites is really after the licensing deal that happened with Virgin, it should be far more
What I don't understand is why they went with the electromechanical scheme that they used, instead of epitaxially depositing a big stack of P-I-N diodes and letting the ionizing radiation work its magic directly. The article mentions a single-layer diode test, but you want a big enough stack to sap charge from the entire trail left by the alpha or beta particle that's plowing through the device.
The electromechanical scheme has the virtue of collecting almost all of the energy as (nominally) usable heat, but conversion efficiency stinks, from what I can gather. Junction efficiency won't be so hot either (for the same reason solar cell efficiency is poor - carriers are given more energy than required to overcome the band-gap), but not too bad (anything over 10-15 eV will just create secondary showers of lower-energy electrons).
Can anyone familiar with these issues tell me what I'm missing?
In case anyone is wondering how these work, the idea is that the radiation from a small amount of radioactive material (NOT fissable material!) is captured and converted into electricity or other forms of energy. There is very little radiation emitted by these devices, because the radiation IS the power! Letting it escape would be poor economy.
The problem is contamination concerns during fabrication and as a result of accidents in the field as the devices are used, and especially due to disposal. Any single battery's radioactives won't make that big a mess, but it adds up. Look at how much fun we're having with all of the cadmium floating around from NiCd batteries.
Recycling and taking proper care can reduce or remove the problem, but the fundamental issue is that over the counter batteries are being put in the hands of people who just don't care very much about being responsible even when they know what they should be doing. A battery capable of generating useful amounts of power needs a _lot_ more radioactive material than a smoke detector, and has correspondingly larger waste concerns.
No, I live in the environment, which keeps getting polluted, behind the Pollyanna talk of safety. Mercury, though poisonous (as I stated when I introduced it to this discussion), is *less* poisonous than radioactive materials like they're considering for these batteries.
Look up the MSDSs for nickel 63, and, oh, let's say "methyl mercury". You will be enlightened.
Here's another hint. Look up how much radon you're inhaling from natural sources, especially if you spend any time at all below ground level. That gives you a rather enlightening ballpark figure for the "natural" background for ingested/inhaled radioactives. If the cumulative doses you're talking about from other sources aren't very substantially larger, the claimed effects won't be statistically significant.
Funny, that's the same thing they said about the X prize... the problem is too big for such a meager prize.
Fortunately it's not really about the prize money.
The problem is that lifting things to orbit is an expensive enough proposition that the barrier to entry for building a launcher is very high. You won't do it unless you have clients willing to pay a lot of money, probably at low volume. The market is also already saturated, unlike the sub-orbital tourism business, with many players and competitive options for cargo launching, and even solutions for non-government man-rated launches (we've been hearing about space tourism through the Russian space agency for years).
So, I'm not sure what this prize is supposed to be encouraging people to do. The companies and other entities in a position to offer man-rated launches either already are, or have decided that it's not in their best interests to do so at this time.
This will remain the case until the nature of ground-to-orbit travel changes (e.g., if someone builds a space elevator or a laser launcher). Both of the examples I give in this paragraph are already being actively investigated, and arguably pursued with some chance of results. The prize addresses neither (I'm pretty sure wording will rule out a scheme with remotely supplied power, though I'm not certain of this).
Although the energetic requirements are an order of magnitude higher for orbital spaceflight, this $50 million prize is almost an order of magnitude higher than the $10 million X-prize. The economic payback seems higher as well, since there are lots more reasons (both reasearch and tourism) to go to orbit than there are in sub-orbital spaceflight.
The problem is that the increase in difficulty is far, far greater than the increase in either energy or delta-v required seems to warrant at first glance.
There are two regimes in which a rocket can operate. In one, the delta-v required for the mission is much lower than the exhaust velocity. In this scenario, fuel is only a small fraction of the total craft weight, and scales linearly with delta-v. This is the easy scenario, and it includes the X prize's "get a rocket to a relative altitude of 100 km".
The second regime, the hard scenario, is the one in which the delta-v required for the mission is much higher than the exhaust velocity. In this scenario, the craft weight is dominated by fuel, and the fuel-to-everything-else ratio goes up exponentially with delta-v. Truly exponentially, not the "this is a quadratic but I'm calling it exponential" variety that I see so often around here. Craft design goes from "really hard" to "damn near impossible" to "outright impossible" very quickly.
Ground-to-orbit is balanced right on the knife-edge of "really hard" and "damn near impossible", and that's only when we use multi-stage rockets. Reusable single-stage-to-orbit chemical rockets are well into the "damned near impossible" regime, even with the advanced composites we have now. If the earth was even a little heavier, we wouldn't be getting off of it with chemical rockets at _all_. Orbital velocity is about 8 km/sec, escape is 13 km/sec, and the highest-Isp chemical rockets have an exhaust velocity between 3 and 4 km/sec (with SS1 having one in the range of 2 or so).
There are ways that you can make the hard scenario marginally easier. One is to use multi-stage rockets, though that's generally pretty much _assumed_ past a per-stage mass fraction of 5:1 to 10:1. Another is to use high-Isp chemical fuels - but these make your craft far more expensive due to handling concerns, and in the limiting case this can even be counterproductive (H2 is a lousy fuel for anything that launches from deep in the atmosphere or under a lot of acceleration, due to low storage density and large tank size). Another is to use as small a craft as possible to take advantage of stress scaling laws, but a) that means an upper-atmosphere launch instead of a ground launch, and b) your minimum cargo weight places a lower bound on the craft weight.
The only realistic options for a 7-human manned craft are a big, expensive multi-stage chemical rocket with disposable boosters (because refurbishing to man-rated spec costs an insane amount of money), or an exotic craft with a high-Isp drive, to push the problem back into the "easy" regime. The only high-Isp craft we can build right now with the required thrust is one with a NERVA-style nuclear drive. A remotely laser-powered craft can work too, and we have a good idea how to build these, but full-scale engineering of these haven't been done yet. Orion is _too_ large scale, and would be even less popular than NERVA.
So, I don't expect any vehicle-based solution to be easy to build or cheap enough to run to make the prize offered a significant attraction.
A single-passenger craft would be much easier, due to reduced craft mass (materials scaling, again).
But curiously, drinking deuterated water is apparently poisonous.
This is because the chemical behaviors of deuterium and light hydrogen are slightly different.
You can think of the electron and nucleus co-orbiting about a common centre of mass, rather than the electron orbiting while the nucleus remains fixed. Where the point is depends on the ratio of the masses of the electron and the nucleus (about 2000:1 for light hydrogen, and about 4000:1 for deuterium). The different orbit radius (for any given energy) for each case means that the energy level at which the orbit circumference is an integer number of electron wavelengths will be different for deuterium and light hydrogen.
This means that the energy structure of the electron shells is slightly different, which means that they will behave slightly differently chemically. This fact is exploited in some of the methods of isolating heavy hydrogen from light hydrogen (electrolysis method, as the reduction potential is different, and the more common chemical method involving forming hydrogen sulphide, as the rates of reaction are different).
In the case of ingestion, deuterium's chemical behavior is similar enough to that of hydrogen that it gets incorporated into chemicals and otherwise interacted with as hydrogen would be, but different enough that it mucks up some of these reactions. Result, poisoning, much as you get from heavy metals displacing their chemical analogues (though less so, because D and H are a lot more similar, and your body cycles hydrogen through itself pretty quickly, while metals tend to accumulate).
As far as hydrogen isotopes go, though, tritium is the main concern. It's a beta emitter, and is formed in water-cooled reactors (especially the heavy-water-moderated reactors Canada uses, as only one transmutation step is required instead of two). It's a very low-energy emitter, but if ingested, will still cause problems. It's less nasty than most contaminents, though, as hydrogen gets cycled through the body very quickly, and tritium has a half-life of about a decade (short enough to disappear within a lifetime, long enough that it cycles out of the body without depositing much of its radiation dose).
Deuterium is mildly chemically toxic, but is not radioactive.
As long as there are a significant number of people who *like* to drive a car, autopiloted cars will be an alternative to, not a replacement for, conventional ones, in the same way that automatic gearboxes have been around for 50 years and still havnt made manuals extinct
Fair enough. However, it will be rare, as it takes years of training to learn how to drive adequately, and will cost money (in the form of higher insurance) to drive manually. The vast majority therefore won't.
The nature of driver training would also change. I'd expect it to become more like getting a pilot's license, where you do a large amount of training under very close supervision, as instead of having to demonstrate that you drive as safely as most humans on the road, you'll have to demonstrate that you drive as safely as most _autopilots_.
You'd also be limited in where you'd be able to drive, as there would be high-traffic areas that need a computer's group-think and precision to navigate (allows for better optimization of traffic flow, which means less expense building/widening roads, so these would exist).
Still, good observation. At minimum, you'd always have company-based human drivers to remotely drive in situations where car AIs have difficulty (per my other reply in this thread). And your point about hobbyists/enthusiasts is quite valid.
I don't see a practical autopilot happening any time soon. I see how it'd work on a freeway, but what about construction zones?. Lanes get closed or reversed. You might have to follow the hand-made directions of the repair crew. A turn might be changed temporarely into a really weird angle that only human perception is nowadays able to descipher.
This is why the "manual override" ability would still be present, for the intermediate term, at least. The autopilot would be set up to by default stop instead of proceeding into an area with features it couldn't identify with confidence, or to proceed only on paths that it _could_ confidently identify (e.g. not making that wierd turn, but instead proceeding with through-traffic and looking for an alternate route).
I'd expect construction crews to be issued ai-comprehendable instruction beacons for strange cases like that. Or even for simpler solutions to be implemented, like standardized symbols indicating what traffic is to do in construction zones (we're most of the way there already).
The point is that the system can be made to fail gracefully (and safely) under these conditions, and that the merits of the system (fewer accidents, insurance benefit) will eventually still outweigh this inconvenience.
In a world where people can still drive manually, falling back to manual override isn't a problem. In a world where people no longer know how to drive, your autopilot would be sold with a contract to a human-staffed agency that would take over and remotely drive for you under conditions where you decided that you _had_ to drive through a region the AI couldn't handle.
By the time we can handle this kinds of things properly, the fact that drives can drive themselves would not be all that important compared to other applications of the image processing and AI technnologies.
Never underestimate what an expert system can do, or how big the gap is between an expert system and a true AI. I think we'll have the required robust image processing algorithms a lot sooner than we'll have robust AI (arguably we already have them; image processing as a field is many decades old). And, as mentioned above, the autopilot only has to work optimally _most_ of the time, as long as failure is both safe and graceful.
In summary, I believe that a useful autopilot system could be built considerably more easily than you think.
Actually the cable seems quite safe even if part of it "falls". Please read the FAQ before such wild speculation.
This depends entirely on how massive the cable is. This in turn depends on how useful you want it to be. It takes a long time to get up the cable (one week for Liftport's version). Your cargo capacity is directly proportional to the cable mass (anywhere from 10% of the cable mass to around 1x the cable mass, depending on the safety factor you build into the cable). Divide to get the rate of mass transfer (5T per day, for Liftport's version).
The key virtue of a space elevator is that it lets you transfer _large_ amounts of mass cheaply. You'd use it for lifting mass for a starship, or for a Stanford Torus colony, or for something even bigger. If you're only sending up a few tonnes of mass per day, you don't capitalize on the benefits of having a space elevator in the first place. Lift costs will have to be much higher to amortize the cost of construction and maintenance, and the stuff you're sending up tends to be very expensive - expensive enough that paying $20,000/pound for a conventional launch isn't a big problem.
For the big construction applications - where you have to send a million tonnes of material a year, as fuel for your interstellar probe or structural material for your space station - you need a cable with a mass of hundreds of thousands of tonnes. In a worst-case accident, where the cable is severed in the middle, the energy of the impacting portion is about 10 times the equivalent weight in TNT. A cable this massive (even a multi-strand cable) stands a good chance of reaching the ground and doing damage, atmosphere or no atmosphere.
There are steps you can take to mitigate this risk - have a multistrand cable with strands separated by significant distance, and webbed so that the failure of any given strand just transfers load to other strands - but it's still awfully easy to induce failure in the whole cable, especially with the cheap access to space that the elevator gives. All it takes is an ion drive, a bit of patience, and a few big spools of iron chain.
In summary, the problem exists. Liftport only gets around the problem by severely limiting the usefulness of their elevator.
No, they won't aim for me. However, the semiconscious retard behind the wheel would have the pathetic excuse of "mechanical/electronic failure" keeping him from prison time when he accidentally mows me down with his H2.
He will then have to explain why "there's a pedestrian, for the love of God *stop*!" shows up in the logs and he chose to ignore it (or override the vehicle's automatic "stop before hitting $object" reflex). Black boxes _do_ have legitimate uses.
A lot of progress has been made on this over the past couple of decades, and we have a couple more decades of progress to go before it's safe enough to use in the real world, but as soon as an autopilot is invented that drives better than the average human (especially under emergency conditions), there will be a large insurance break for using it. Shortly after this it will become the norm.
My money's on methanol or methane, as both can be stored as liquids (methanol more easily), and methanol can be burned in a conventional engine with a bit of tweaking (making the switch from internal combustion to electric engines much more graceful). You even have interesting hybrid options available, like an electric car with a gas turbine burning methane (or propane, which you can fill up with at gas stations now, making the switchover to _methane_ easier). Methane and methanol can both be synthesized directly from water, CO2, and electricity, meaning that they're suitable fuels for an electric vehicle infrastructure after fossil fuel supplies of them run out (and after we need more than we can get by reclaiming biological waste). We have lots of experience with moving hydrocarbon gases and volatile liquids around, so the transport infrastructure's already here. Methane and methanol have nowhere *near* the storage and handling problems hydrogen has.
It'll be interesting to see when the first point happens (I think it's pretty inevitable that it's going to). A methanol (or a methane) fuel system might or might not happen. If compact energy storage and vehicle efficiency get good enough, a direct electric scheme might work. However, most non-chemical methods of electric storage don't have high enough theoretical densities (even with nanotube-reinforced flywheels and induction rings), and a purely electric vehicle infrastructure is a lot harder to phase in gracefully. Alternatively, we might just keep improving our ability to harvest lower-grade and less-accessible hydrocarbon deposits, and push the fossil fuel problem far enough off that by the time the crunch hits, technology will be different enough to drastically alter the space of possible solutions.
Definitely interesting times ahead.
Modulate a thousand frequencies of sunlight at the same time and pass them through your transmission medium of choice (space?) and don't stress about diffraction or diffusion as long as the light reaches the other side; because your receiver is an array of several tens of thousands of carbon nanotubes that auto-magically sort out the frequencies.
Ta-da! You just transmitted the entire Library of Congress in a matter of seconds.
The problem with using this for data transmission is that in order to measure amplitude accurately, you need several photons received in your measuring period. As frequency gets higher, the photons get more energetic and the sampling period (at the maximum rate of modulation) gets shorter. This results in power per unit data going up directly with frequency, and power per unit time going up as the square of frequency. The same relation turns out to hold even if you use other methods of signal processing (you could split the modulated light into its component frequencies and end up with a bunch of lower-bandwidth signals that way, for instance).
For signals modulated much more slowly than the frequency of the light itself, this penalty in power-per-bit may be acceptable if using light gives other advantages (like smaller dish size for a given divergence, or ability to pipe through fiber). However, at the maximum rate of modulation, both transmission power and power per unit area get prohibitive.
At one bit per sample (the most power-efficient encoding), you get a minimum power for an intelligeable signal of about 0.7 mW (1e15 samples of 4 photons at about 1 eV each). This is per nanotube antenna. This is unlikely to be survivable. For an 11 angstrom single-walled nanotube seen end-on, it corresponds to a power flux of about 7e14 W/m^2. At radiative equilibrium, this gives a surface temperature of around 300,000 K on your antenna array (room temperature is 300 K, nanotubes change phase somewhere between 3500 and 4000 K, and the surface of the sun is 5800 K). If you instead use the nanotubes side-on as antennae about the size of a photon's wavelength (around 1 micron), you get a power flux of about 7e8 W/m^2, giving an equilibrium temperature of around 8700 K (still hotter than the sun). This is misleading, though, as the signal would have to be coupled into a single nanotube antenna, with a much smaller surface area (giving a power flux on the order of 1000 times higher, and temperature 5-6 times higher).
Transmitting over interstellar distances is also very difficult, as you need to assume a collecting mirror size, and make sure that enough photons strike the collector to get an intelligeable signal. For a 10m telescope mirror, power needs to be about 9e-6 w/m^2. A broadcast signal at a range of, say, 10 light-years covers a surface area of about 1e35 m^2. This gives a broadcast power of about 9e29 W. By comparison, the sun puts out about 4e26 W. So broadcasting a beacon like that, even to a nearby star system, is impractical. Beaming it still covers a large area, due to divergence induced by aperture diffraction at the sending mirror. If we assume it's being broadcast from a 10 m telescope, divergence is about 1e-7 radian, for a spot diameter of 9e9 m. This gives a spot area of about 6e19 m^2, and a power of about 4e16 W (40 petawatts). A bit steep for a beacon, when you could save many orders of magnitude by either using radio, transmitting data more slowly, or both.
In summary, modulating data on an optical carrier has drawbacks, and doing it at optical data transfer frequencies almost certainly requires enough power to vapourize the detector. Still a nifty thought-experiment, though.
It's interesting that this should come up, as last spring or so, I was sitting on the presentation of a paper about doing this with far-infrared. Conventional lithographic techniques were used to make waveguides and rectifiers. Photons entering the wave guide caused currents when they struck the walls, which were picked up and rectified by interesting devices that worked by exploiting ballistic electron transport (looked like a wedge inside a T-joint; electrons flowing in one direction were preferentially scattered).
Frequency limit of this technique was related to the sizes of their structures, but I didn't get the impression that it would work at optical wavelengths. Still very nifty, though.
[The paper was presented at CCECE 2004, but I'm having difficulty finding a citation.]
On the other hand analog signals degrade gracefully. Even when you can only see 10% of the total image, you're looking at 10% of the whole thing, not 1/10 the frames or 1/10 of the picture. A little interference in a digital video stream makes the picture "jump" and may cause bizarre audio artifacting as well. A little interference in an analog video stream shows up as static, color that's "off", et cetera.
Degradation effects depend very strongly on how the data is encapsulated. When redundancy and precacheing are added for important parts (e.g. most important spectral components of the image, if we're doing lossy compression, and most important components of the audio), then noise and interruptions in the stream cause degradation that's at least as graceful as with analog TV. Argubly more graceful, for a well-defined protocol, as you get to pick which components you want to preserve at all costs, while in analog transmission, you're limited by the fact that you're displaying frames and pixels in a predefined sequence determined by old TV hardware.
There was an excellent demonstration of a scheme like this intended for mobile phones at TechCon 2003. That one worked by pretransmitting voice and key-frame data for a news clip, giving decent-looking and sounding results even when streaming was terminated half way through the broadcast.
In summary, digital transmission at least in principle gives you far _better_ degradation qualities than analog, because you can choose important features and make sure they arrive no matter what.
I'm waiting for TV via Wifi. Oh wait, I guess TV already is wireless.
I know this was intended to be a joke, but the advantage to using a digital streaming protocol for video over wireless is that you can at least in principle handle signal degradation and dropouts a lot better than you can with plain old analog TV. I know _I_ got tired of doing the "wave the rabbit ears around until it looks almost-decent" thing.
Furthermore since when does capitalism display dignity and display wisdom?
All the time, provided there are no artificial limits placed on it.
The forced economic classes that it creates can only be called dignifying to the rich and the quickly shrinking remnants of the middle class.
Wasn't always that way. There actually used to be a middle class back when people had careers instead of temp jobs. Almost anyone who put in a day's work could earn an honest wage and afford a home. Now, the median price for a home is almost a half million dollars and the average job lasts less than 18 months.
I am having difficulty reconciling your two statements, as both temp jobs and housing prices are a direct consequence of market forces at work. Yet, you seem to feel that they are undesirable, while the capitalism that produces these market forces produces predominately desirable results.
There will be no further significant space exploration because business decides everything and there are no money grabs available.
The "big business" which you take exception to is the natural end result of unfettered capitalism. A perfect capitalist entity acts to maximize its profit, and dominating a market, degrading produced value to the minimum that consumers will accept, and paying workers the minimum that they will tolerate, is the best way to do that. It is only _through_ artificial limits like anti-trust laws and labour laws that these harmful effects are kept in check (albeit imperfectly).
Over-regulation of business has its own problems, but a purely capitalist system with no artificial checks would very rapidly produce a _horrible_ quality of life for the majority (those who didn't come out on top of the pile when trying to amass vast wealth).
It's bad news for the space program either way, of course. There's nothing obviously profitable enough out there for business to want to go after, so in a money-dominated system, the space program languishes. We're also lacking a determined and sufficiently credible political rival going after space targets, so the government isn't going to strongly back a space effort in a government-dominated system. Even if scientists _could_ make an argument for it being a good research investment to send humans out to Mars (or even a LEO station), they don't have enough clout under either system to make much difference.
Big, flashy space projects will come back when China convinces the US government that it really might beat them to a moon or mars race within a couple of election terms, or when launch costs lower by enough orders of magnitude to make marginal or speculative payoffs attractive to business. In a few decades, either one might happen, but neither is the case now.
Cynical, aren't I?
First, the obligatory link to a mirror of the MIT Lockpicking Guide.
Second - as another poster noted, lock pins aren't typically made from high-strength alloys. A battery-powered hand drill (and a screwdriver to turn the lock when the pins are gone) is the best and fastest lock pick that there is. Didn't even leave any visible damage when I used this approach on a filing cabinet we'd lost the key to. Just pick a bit as wide as the key entryway, and drill down the line of pins.
Be advised that the lock tends to jam after closing again, as the remains of the pins fall back into their channels when the lock returns to its original position. But if you're drilling a lock, you're typically looking for a one-time solution anyways.
you obviously haven't seen "A Brief History of Time", "In Search of Schrodinger's Cat", "Schrodinger's Kittens" and many other non-maths physics books.
These are "physics books" the way "the matrix" is a computing and AI primer. That is to say, they tell you that several of the important concepts exist, in a way that's entertaining, but don't do much to tell you how to actually _use_ them.
At best, "physics overview for the layman", as opposed to "physics reference".