Enthalpy

A correlation receiver has two or more antennas (could be hydrophones, microphones...) followed by separate preamplifiers, mixers, amplifiers, converters. It computes many time-shifted products of the signals caught by the antennas and integrate them over a long time. The time shifts correspond to different listening directions, and the integration time accumulates the desired signal, which is correlated at the antennas, but less so the uncorrelated noise, improving the sensitivity. I suppose one can compute products or something over more than two antennas; ask a radio-astronomer. With more hydrophones, irregular patterns reduce the sidelobes; for instance the VLT (that's interferometry, but it holds for correlation) has no square baseline. Hydrophones at varied depths would discriminate noise from the surface. This integration gain is paramount in radio-astronomy, whose signals are wideband random noises remarkable only by their provenance and correlation. A correlation receiver would have advantages as well with a narrow-band pinger: Reduce the local aquatic noise, including flow noise. Reduce the noise created by the hydrophones and preamplifiers. Integrate many pings. Reduce the background noise not in the listened direction. Identify the pinger's direction. Discriminate multiple propagation paths. If existing pingers at 37.5kHz have a ceramic buzzer and an oscillator powered on and off, the phase of successive pings is random, and a correlation receiver improves over a simple narrow-band (Fourier) receiver - but keep the narrow band. Same if the aquatic propagation introduces jitter whose difference is smaller between the paths to the hydrophones. How far apart should the hydrophones be? Directivity would accept very close hydrophones, but distant ones discriminate local noises better. The limit depends on how much and quickly the propagation conditions to the hydrophones differ, and should be experimented. I suppose different correlation receivers exist already at sonars, which correlate noise sources at the Ocean's surface with their echo at the silent target, but here we search an emitting target. Anyway, much knowledge and know-how is common. The hydrophones are expected to move over the Ocean floor: even 1m/s with 10m baseline and 3000m depth would shift a nadir signal after only 6 pings, so the software should identify the speed and compensate its effect over time for various depths and directions. The swarm of aquatic or subaquatic drones can use a correlation receiver, either when moving or by stopping when they listen (future muscles and a tail will be more silent than a propeller). A helicopter, quadrocopter or multicopter drone looks attractive to carry quickly a wide frame of hydrophones and dip it low (800m+) from place to place: fuel cells would give it range before it refuels on the continent or on its boat. Folding or retracting a bigger frame before landing would be a funny endeavour for mechanical designers. Marc Schaefer, aka Enthalpy

Welcome here! Mass spectroscopy counts individual atoms, so the amount wouldn't be a limit. I just wonder how to evaporate only the area that interests you; answers exist probably. Just ask such people. Possibly a jet of etchant ions could be directed only at the area of interest and evaporate the unknown nuclides only there. It would take some pure ion source which is not hydrogen nor oxygen. The jet would be produced inside the source chamber of the spectroscopy apparatus. This must exist somewhere, ready for use.

Isn't it a matter of acidity? Lemon juice for instance lets milk clump.

There is no significant tritium in our surroundings. Breeding it in tokamaks, provided they can, would pollute as much as uranium reactors do. http://www.scienceforums.net/topic/69318-is-fusion-power-the-way-forward/#entry704591

Keeping the inducing coil cold is difficult. The number of turns doesn't help, at least at low frequencies. In the same shape, if you put N times more turns, having each N times less cross-section, and total length N times bigger, then the (low frequency) resistance is N2 times bigger. The current is N time smaller, so the resistive losses stay the same. (Eddy currents and skin effect don't scale like this, hence I insist on low frequency) What helps is: - Copper versus more resistive material - Resistivity increasing at heat - If the heated material is ferromagnetic (...not too hot hence), then current flows only in a much thinner skin at its surface, and the resistance is much bigger. This is the case when the surface of a steel part is heated by induction, then this surface is cooled quickly by the deeper matter of the part, and this hardens the steel at the surface only.

From a practical point of view, I wonder how to stack 200 layers and maintain 1nm spacing. But maybe that's not what you're interested in right now.

Welcome here! IR for infrared? It can be quick. I'd prefer a position detector over a timing, because you can't predict accurately how strongly the projectile accelerates. "Basic soldering and electronics skills" would be a very serious limitation for this project. A coil gun is full of less-than-trivial electromagnetism and power electronics.

Very wrong for flexural waves, which is the case here. Flexural waves are the absolute pre-requisite to understand bells. I've provided a link to Wiki. By the way, 6000m/s would give nonsense resonant frequencies for a bell. Checking that figure tells that it's the wrong way.

If using atoms instead of electrons, the size of these atoms limit the resolution - to about one atom. This is an other limit than the wavelength. Electron microscopes use energies well over 7keV and achieve resolution little better than one atom. The limit for them is more the poor quality of the "lenses", as well as the available intensity in very small areas. You might consider protons, deuterons, alphas instead. But as a drawback, they give more momentum to the atoms they hit, making a bigger damage.

Nuclear weapons were only the first attempt to create EMP. Presently, they use pulse electric power, are operational and in use in most armed forces, and most military electronic equipment is designed to resist it. A common design is a flux compressor, were chemical explosive compresses a strong magnetic flux to increase quickly the induction. Invented by Sakharov hence old, used against Al Jezeerah's station in Iraq during the war. These are bomb-sized. A more recent design uses quick electronic switches. Probably MOS transistors, simply, but they could be Blumlein or even a Marx generator. They fit in a suitcase, destroy to 10-100m range, temporarily disable to 100-1000m range. Such an EMP weapon was probably used in Aosta, from the effects observed by inhabitants. So it's absolutely actual. I wish to ask airliner designers to build their electronics EMP-resistent.

The electrons have the volume of the atom itself. I don't imagine them as points. So I don't say that an atom is void. By the way, it's not what you'll hear most often, but I have good company in that representation of particles. Schriffer (from BCS) said it exactly the same way: the electron IS the wave (in the case of an atom, this wave is an orbital) and HAS that size, which depends on its state.

Some geologists took advantage of the search for MH370 wreckage to encourage the complete mapping of the Ocean floor by sonar, for a few billion bucks. http://www.bbc.com/news/science-environment-26956798 Of course, any very hypothetical help in this search from better maps isn't worth the money. For other purposes, I don't know. But if someone was to make this exhaustive mapping, he should reconsider the method. Sending surface boats and crews for years costing billions, there must be better methods. One first alternative to consider would be, still by sonar, a swarm of aquatic drones. If sailing in close group, they could get a better resolution, just as the MiG-31 does with its radar - provided sound propagation doesn't blurr it. Submarine drones could be advantageous: no separate towed sonar, and unmanned ones would easily dive to 800m or more. Electric engines are more silent; range may need to surface and charge batteries - but consider fuel cells, which give present German U-Boots over one week underwater operation.

You could have a look at the arguments of the proponents of the travelling wave reactor. These people knew very little about nuclear energy. They just said "it would be fantastic", not a word about "how" (because, anyone knows for long the potential advantages, only they didn't understand the difficulties), and this was enough to pull money from Bill Gates. It's impossibility results from detailed figures, which aren't even well accessible to hand computations. So there's no simple qualitative answer. But consider that any breeder is seriously difficult to bring to plutonium regeneration, using optimum conditions everywhere: shape, size, concentrated military plutonium fuel - and then the breeding figure is like one dot zero something. The travelling wave reactor would be a breeder, but under very unfavourable conditions. No chance to run. Then, you may read the initial proposal by the crooks: they wanted to ignite the travelling wave using uranium - which clearly tells they don't understand the topic. I wonder: how do you decide what (or who, which is a less good choice) you want to believe? The ones you read first? Or the proposal that fits your desires better? Be reassured that it's not my personal opinion: the whole nuke community considers for decades the travelling wave reactor as an obvious impossibility.

Vapour rises at >300°C depending on the location and depth. That's as good as in water-cooled nuclear reactors, which have >30% conversion efficiency. Compare with 45% for gas power plants, and keep in mind that Earth's heat is for free. In the former coal mining basin where I live presently, all houses tilt, some being rendered unuseable. A magnitude 3 quake makes less damage.

Elements of answers in bulk: Type I superconductors, the less capable ones, have zero resistance if low enough below the transition temperature, in a field small enough, with a current density small enough. These exhibit the full Meissner effect. For significant induction, only type II superconductors accept the necessary current density and field, and these do have a resistance, though much smaller than metals at normal temperature. These are used at colliders and so on, because there's no choice. They demand helium cooling for any interesting induction. The coil that levitated the frog in Holland was resistive, if I remember properly. Put a few tens of MW in copper, cool with water consequently, get 10+ tesla. Unfortunately, building and powering such a coil is difficult - I'd say too difficult for your present knowledge. A superconducting coil is too difficult as well. The frog levitated due to diamagnetism, especially of its water. It also works with pyrolytic carbon, among the common substances. This is not the Meissner effect. Stability results from the shape of the field and of the weight (otherwise the stable position would be simply: far from the magnet): the induction must be stronger at the sides and at lower positions, which is often the case, say at a ring (flat annular) coil. http://en.wikipedia.org/wiki/Diamagnetism resistive coils, superconducting coils and permanent magnets behave in a similar way for that. The effect of the object on the magnetic energy is locally like 0.5*B2/µ0*X, but the field rearranges a bit, so the net coefficient is <0.5, not by a magnitude. If this energy varies with the height faster than the gravitation energy does, the object levitates. What is accessible to simple experiments is: - curve the surface of water by a strong permanent magnet - levitate pyrolytic carbon on permanent magnets - more ?

I'm not sure at all that the search is mislead - and having no reason to believe so, I prefer to believe it's done properly by everyone. What I'm sure about is that if a company or government believes that showing a design flaw on the plane hampers the sales, then they will easily leave the wreckage and bodies where they are to favour the sales. As the Airbus 320 got its infancy crashes, investigations were deliberately hampered and mislead. Lithium batteries: some are reasonably safe but heavier. On the Dreamliner, designers and supervisors at the company and certification agencies took a chemistry that had already caught fire at laptops. That was an error to my opinion, by successive people, but mass constraints are just brutal at an aeroplane. Once these batteries caught fire as they just do sometimes, designers couldn't replace them by a heavier chemistry on the Dreamliner, which relies on huge electricity storage. They put a box, which is an answer, if not the ideal one. What is unthinkable is that Airbus took the same chemistry for the A380 and, instead of replacing it - as the A380 needs less electricity storage - they tried to explain that the size of the batteries, not the chemistry, made them dangerous on the Dreamliner. To my knowledge, the A380 hasn't even added boxes around its batteries. That's bad behaviour. ---------- More pings heard today, supposedly from MH370's black boxes. Fainter, but underwater propagation isn't reproducible. According to the Beeb http://www.bbc.com/news/world-asia-26950387 sonobuoys will be dropped in the more accurate zone, with hydrophones hanging 300m below the surface.

Earthquakes were also observed "in relation" with fracking for shale oil and gas. At least for the quake in the Rhine valley, it happened as I had just applied at the geothermal energy company, and resulted from "human error" as they call it. That is, it didn't need to happen. You can consider it differently: if one builds a home in a quake-prone region, the house shall be quake-safe, please. Basel was completely destroyed few centuries ago, so homes damaged by a magnitude <3 have nothing to do in the upper Rhine valley - whatever triggers the quake. If there's a devastating quake every 500 years and you build your house for >50 years, the odds are 1 to 10.

The Iraqi reactor had not been started. The area polluted by the Chernobyl reactor is evacuated. I have written "weapons" and "armed forces" and "enemy". Please don't mislead to terrorism and aeroplanes.

After a Chinese ship heard pings at 37.5kHz, so did an Australian ship yesterday, and much louder, but at locations very distant from the first one, and today it heard none at that place. I wonder. The pings are extremely caracteristic, and yesterday they were heard for a very long time, needing margin on the signal strength. It has been proposed that today the batteries are empty. Though, I read previously that the signal strength would first decay over several days. How could both pingers run out of power at the same night, and so abruptly? And since losing the black boxes hundreds of miles apart isn't believeable, could one ship mistake a noise for the ping, which has an accurate and very uncommon frequency, at a regular 1s repeat beat? That's obscure to me. ---------- I've also read some proposals to improve plane wreckage recovery at sea in the future. Some even propose specialized radar satellites for that. And, despite understanding the importance for the relatives, my position is that one billion dollars are completely out of proportion with the usefulness of finding a wreckage and explaining a crash. With very few millions, you would equip avalanche rescue helicopters with radars that see the victims through the snow, and save living persons. ---------- Anyway, there would be cheaper methods to locate black boxes more easily at sea, the first one being a sound frequency better chosen than 37.5kHz. For instance here, you find the absorption versus frequency (and depth) in the Ocean: http://resource.npl.co.uk/acoustics/techguides/seaabsorption/ At 37.5kHz its about 65dB over 10km distance at 3,000 depth (and impractical 130dB over 20km distance) At 3kHz it's 15dB over 100km distance that's why sonars and mammals use low frequencies. A submarine hull reflects less than 1mW active sonar power (less than a pinger can emit) but is detected very (very) far away under neutral conditions. 3kHz would also be audible by humans (almost the highest note on a Piccolo flute) without technology or just with a stethoscope, which I consider a big advantage. In an emergency situation, no-tech or ubiquituous low-tech is better. And with technology: that's a frequency military sonars would hear, and one ship-based helicopter would cover the search area quickly. My first estimates indicate that compact transducers are feasible. As a note, one shouldn't evaluate a sound range at sea from open-space propagation and losses. Sound velocity increases at depth because pressure makes water stiffer, and the resulting refraction reduces a signal emitted from the Ocean floor. Temperature differences at water layers also create refraction. This explains why towed hydrophones are flown deeply. ---------- In an other thread I suggest planes and helicopters with hydrogen tanks and fuel cells. For the present search far from the coast, the several days flight time would be an advantage. Have more pilots on board, or a remote control - or build them as drones, since both Sonar and optical survey is an easy task for them.

Shattering a nuclear reactor disseminates the fission products it contains, whatever its technology. It's basically what happened at Chernobyl. Some countries offer 20 to 100 such targets to an assaillant. The country would be uninhabitable. Battletanks have kinetic energy penetrators http://en.wikipedia.org/wiki/Kinetic_energy_penetrator that break present reactor confinements from few km distance. Battletanks protect against radiation. Bunker buster bombs would break any future reactor confinenement dome and vessel http://en.wikipedia.org/wiki/Massive_Ordnance_Penetrator some can be launched from a remote plane. A much bigger and faster kinetic energy penetrator can be launched by a rocket from a truck at 5,000km distance. Hugely more destructive than an explosive head. This one would let a fast neutron reactor (like a breeder) detonate like a plutonium bomb, by compressing the core.

Solar energy does NOT mean photovoltaic, and means even less semiconductor. Solar thermal is a better way, because the collecting area (mirrors) is cheaper, the conversion more efficient (35% and more), and heat is stored for night.

Wind turbines are cheaper than nuclear power plants. The produced electricity, as well. Storage works already. In Solar thermal power plants in Spain, on an interesting scale, with meaningful economic constraints. Then you have geothermal energy, which is available where and when you need it, needing little ground area. Including 3,000km away from the next geyser. Convincing ideas exist to store electricity. That would be a reasonable million-buck effort, not a billion-buck waste in nuclear plants, which lost us two valuable provinces to make 1% of the world's electricity, and have too little uranium to replace hydrocarbon energies.

On Earth nor anywhere else, the travelling wave reactor doesn't work. Even the Indian engineers, who spent such a big effort on thorium reactors, have abandoned the hope of breeding with thorium reactors. Thorium reactors will always need additional plutonium made by uranium reactors, which are limited by the abundance of natural 235U. That is: with the natural 235U, one can fuel uranium reactors, or less directly thorium reactors, and in both cases, this natural abundence limits the available energy. Only a tiny proportion of the available thorium can be used. In addition, thorium reactors would be extremely proliferant. Having the fast neutron core, the customer country could just replace the thorium blankets with uranium to get 239Pu. And anyway, two bombs using 233U were already detonated. Then you have the risk of a nuclear explosion, just like a plutonium bomb, if a kinetic impactor weapon hits a fast neutron core, including at a thorium breeder reactor. For the same use of thorium needing plutonium, one can just burn a plutonium-thorium mix in a normal uranium-water reactor. It's already done in VVER. No additional money waste needed.

The best methode to locate a pinger may rely on Doppler effect. A ship sailing at 10m/s (20knt) observes 0.67% Doppler shift on sound, far from the source. Provided that it hears the ping at that speed, and so on. The operation is then: sail at constant speed, record the ship's position and the received frequency against time. Measure the received frequency long before and long after passing at the maximum amplitude. Compute the mean of both frequencies, and deduce where the boat passed through thes zero-shift received frequency. This is the minimum distance, more accurate than the amplitude would tell. Then, take a new route to pass over the previous point, but at 90° from the previous route. Repeat the recording and position estimate. The two minimum distance lines intersect at a point, the best position. You may repeat the first pass, this time right over the already estimated position. Well, there are many conditions for that method to work... The emitted frequency must be stable enough - if the pinger oscillator goes on when the piezo doesn't emit, then far better than 0.1% minute-term stability results from any RC oscillator. The received signal must be clean enough to measure a frequency. The ping duration must suffice to measure the frequency accurately. But if the oscillator goes on between ping emission, one could correlate the phases from one ping to an other. 0.67% shift over 37.5kHz already makes 25 cycles over 0.1s. Multipath propagation would be a worry. And of course, it takes special apparatus, or possibly software. Nothing complicated, but time runs out. Marc Schaefer, aka Enthalpy

If the absolutely thinkable cyber attack did occur, be 100% confident that Boeing and its governments will do everything they can to hide it. Even misleading the search if they feel it necessary. To be clear: Airbus' governments will do the same, if Airbus as well was stupid enough to merge all data networks on its future planes. After the fires on the Dreamliner, Airbus realized they had the same wrongly chosen lithium battery chemistry on the A380, so propagandists tried to explain that only the battery size on the Dreamliner is dangerous.