Enthalpy

The aerodynamic centre does move with the angle of attack, even before stalling. In today's profiles it's wide behind 1/4 of the chord. Some profiles are designed to give passive pitch stability to avoid a stabilizer, but that's difficult, needs other sacrifices, and is uncommon. A canard doesn't necessarily help avoid stalling, and can be quite detrimental in this aspect. Root extensions aren't vortex generators - two different methods.

Because can't adjust the oven's heat to your water needs, I feel better to have a separate water boiler. Heat it with wood as well. Then corrosion won't pollute your food and is less of a worry; it may still pollute your water. Many water boilers have copper pipes (they release dirt but survive for long). Stainless steel would resist better and may be cheaper. Could you maybe find a trashed water boiler - meant for gas for instance - and burn wood below it? It would already have an efficient heat exchanger, and if your scrap dealer isn't too expensive, you can replace the heater when wood fume makes it unusable.

Keratotomomania was just meant as a synonym for hairsplitter. OK, no fun, sorry. The Pdf report from Sandia tells MV and µs but through thicker water, like 0.1m or 0.4m. But never mind, D-D fusion needs only a few 10kV, leading to a water thickness like your 2mm. I don't really grasp why you want to increase the pressure prior to the discharge. A short event would leave water at its inital density which isn't bad. If you plan to increase the density several fold, no container will hold the pressure; this would be a dynamical process (=an implosion), and under these conditions, you obtain a conductive plasma, no more insulating water. Up to now, attempts to accelerate D or T ions by an electric field to smash them against T or D, even at the density of a solid, did easily produce fusion but failed to produce more fusion heat than the electricity consumed. Instead, promising processes use a high temperature at D or T or both, with some containment method, that allows to use the thermal energy of the atoms over many collisions, so that the energy investment may eventually pay off.

Non-invasive methods work right now to map the cortex' activity: MRI (magnetic resonance imaging), PET (positron emission tomography), MEG (magneto-encephalogram). MRI and PET map the flow of blood in the cortex (not the less abundant neurotransmitters) which varies locally according to the activity. The time-resolved Raman build by the researchers in Amsterdam does show hidden objects, like explosives in a bottle. I only suggest to show the cortex within the skin and skull, especially the local blood flow. This is not a picture of the skull. Scattering of light is a very serious limit to pictures made through the flesh if using visible or near-infrared light. The explosive detection suggested by the research paper is far less hindered by scattering than a picture. I had falsely hoped Raman would completely suppress scattering, as the Raman frequency change happens only once - but unfortunately, light can be scattered in the flesh both before or after the Raman effect. This must be a big advantage of time-resolved Raman over the process I suggest, with illumination and observation from different angles. In my proposal, light scattering followed or preceded by Raman appear like a Raman hapening at a different depth without scattering. At time-resolved Raman, it takes two successive scatterings compensating an other so the detected light comes from the proper direction: less probable, especially if the in- and outcoming rays are offset by more than one cell diameter. Scattering is so intense in flesh for red light that it should hamper even time-resolved Raman, but longer wavelengths should improve that - especially if longer than a cell diameter, which would be a somewhat longer wave than thermal infrared. Less comfortable: the frequency would be similar to a typical Raman shift. In conditions where scattering isn't extremely strong, an different or complementary approach would let the light source and the imager move with respect to the observed object and add the light coming from the same voxels - a bit like we move our head to observe an object through a dirty window. Over many frames, non-scattered light adds up more efficiently to result in a clearer picture. Marc Schaefer, aka Enthalpy

A varying electric field always means a magnetic field as well, and a varying magnetic field always means an electric field as well. You can create pure electric or pure magnetic fields, but only static ones. Static fields don't propagate far: they're local, or "near-field". This is just observation, or if you prefer, the way Nature works, or name it accordingly to your beliefs. Yes, some maths could "prove" it... But actually, the result only proves that the maths chosen by Maxwell adhere to reality. In fact, the incomplete equations pre-existed; Maxwell added that the current corresponding to the polarization of dielectrics and of vacuum creates a rot(B) just as a flow of charged particles does. This tells that, as a varying electric field creates a polarization current, the induction can't be uniformly zero then. With that addition, Maxwell explained EM waves. So the maths would be flexible enough to model other EM behaviours than the one observed. In an atom, orbitals are immobile solutions for an electron in the sense that the electron's wave amplitude doesn't depend on time (the phase does, it rotates around the nucleus over time, which explains why an orbital can have a mechanical and a magnetic momentum). These immobile, or stationary solutions, don't radiate - for lack of movement if you wish. A weighted sum of orbitals isn't a stationary solution any more. The wave amplitude does vary over time, at a frequency equal to the energy difference between the stationary orbitals, and this movement of the charged electron does absorb or radiate light at that frequency. You're right to make a very concrete mental image of this process, as long as you don't imagine a point-like electron. Now, if you want to imagine as a short oscillating current this "movement" of a charged electron that still pertains both to the old and new orbitals, or if you compute the field produced by a short antenna, you can use the Biot&Savart equations. The current gives you a magnetic vector A with B=rot(A) and the pair of charges at the wire's ends gives you an electric field E. The current accumulates charges and the charges result in a current, as soon as they oscillate - and so do the resulting B and E fields.

Surprisingly, a patent by CEA tells a method: Mix some mercury into a flow of oxygen and butadiene, irradiate by a mercury lamp depleted of the isotope 196, this separates the isotope 196 in the flow. Which might be a variant of the laser method proposed for uranium enrichment... I just wonder how the hell the ultra-faint optical frequency shift by the neutrons shall change light absorption by mercury in th gas mixture. All gases - including in the lamp - must be at a damned low pressure, or line widening due to the short mean free path will let all lines overlap. Edit : Webster and Zare, "Photochemical Isotope Separation of 196 Hg by Reaction with Hydrogen Halides" J. Phys. Chem. 85, 1302 (1981) tells 10mm Hg, a mystery for me. Maybe a multi-step separation. Next interrogation: how much energy does it take per isolated atom? In that patent, I believe to understand every mercury atom is excited by inefficient optical means just to extract the 0.15% isotope, which is nearly as inefficient as mass spectroscopy. Present methods seek to expend less than one ionization energy per isolated atom, which is an advantage of diffusion and centrifugation over mass spectroscopy. Finally, Mosheh Thezion, could you explain us this interest in 196Hg? CEA paid a patent for it, so it must have some use, beyond the mere availability of mercury lamps? Did someone finally find a neutron multiplicator that is less polluting than lead? It would be nice, since lead spallation makes D-T fusion reactors as polluting as uranium fission. Or do you want to build lamps? From http://www.patentgen...nt/5205913.html : "U.S. Pat. No. 4,379,252, the advantages of utilizing higher than normal levels of .sup.196 Hg in the Hg added to fluorescent lamps are described and include unexpectedly high efficiency gains in light output." "The drawback of using this isotope lies in its high cost. For example, using conventional enrichment techniques, mercury which has been enhanced to contain about 35% of the .sup.196 Hg isotope can cost about $500 per milligram." Which deepens the mystery for me. Well, if 196Hg radiates light so much better, you can probably build a lamp and collect in it the Hg fraction that is already de-excited. Or the one that is less prone to non-radiative de-excitation. Will you tell us? Thanks!

I expect - but wait for other opinions - that 0.1V is too low for any effect. There are thresholds, higher that 0.1V, just because an electrode's surface isn't a clean metal, and differs from water as well. You may use a low voltage when both electrodes are the same metal dissolved in the electrolyte, but even then, 0.1V is little. If the voltage exceeds the minimum necessary for electrolysis to happen, I expect a small current density to first deposit fully the easiest metal, limiting the voltage to what this metal needs, and then the voltage to increase to deposit the second easiest metal - which may never happen in a river that replenishes the easiest metal. When all metals easier to separate than hydrogen are gone, you get hydrogen. Which isn't a strict limit experimentally. The same should happen at the other electrode with the anions, complicating the voltage behaviour. With a decent current density, the process is less selective and you get a cation and anion soup.

Dear John Cuthber, I recognize here your keratotomomania... Efficiency uses to compare the useful production with the costly expenses, and not the energy input and output - as you perfectly know but pretend to ignore for the sake of your answer... If one really wanted to compare total input and output, he would need to include the loss of potential nuclear energy included in the atomic masses of D, T and He, and then the efficiency would be exactly 100%. Which would also need to catch the energy of any emitted neutrino (since D-D produces an unstable neutron), a technology still immature.

A fusor would be a funny project, and at the fusion rate it achieves, you won't end like David Hahn. It has been done often but is still a demanding entreprise for a beginner. You need vacuum seals, high voltage and so on. Hydrogen abundance implies deuterium can be isolated with a significant effort. Tritium, which is necessary for tokamaks like ITER, is not available from the Ocean. Sorry.

1kHz to 100kHz usually does NOT electrolyze water. Even 50Hz is too fast for that. You better use DC; mix you gases thereafter if this is what you need. A research paper from what century?

What "best bet"? The only good oxidizer is liquid oxygen. Everything else is inefficient, explosive, toxic - often all at once. So what kind of improvement do you seek? Shall it be solid, cryogenic, storable? First stage, interplanetary mission, lander? These days many companies claim to have a magic "green" propellant and they are just crooks. Their stuff uses to be very dangerous and inefficient, but somehow they manage to get subsidies. Within few years we won't need to replace tetroxide any more, because satellites and craft will all use ionic propulsion, and applications needing more thrust will have oxygen+fuel. Indefinite cold storage with a cryocooler is a better answer than all these bad chemicals. A glow plug is a better answer than hypergolic ignition. I wouldn't waste a single cent on these useless and dangerous attempts, where the present generation has forgotten why so many propellants were abandoned and re-discovers it the hard way. Things like N2O, peroxide+ethanol, acetylene are just unusable explosives.

The amount of heat stored by any liquid lubricant film would be negligible, and here we're speaking about a solid film.

196Hg is stable, its natural occurrence is 0.15% http://www.webelements.com/mercury/isotopes.html Isotope separation is long and costly. Only hydrogen is easier.

Hi Happyp! The copper pipe is definitely inadequate, Pvc was the right choice. I did rather similar games with a comparable capacitor energy and did see a mechanical effect - but just on a shorted loop of copper wire, not too heavy, close to my flat coils, and it was repelled to few cm height. So depending on what a bb is (foreign language, sorry) it's very possible that the energy doesn't suffice. You might try the lightweight copper loop first. Your coil isn't ridiculous (what's the diameter?), as is discharges the capacitors with 3ms half-period (I suppose the inductance is measured!). Damping is rather low so you should check if the switching circuitry or the rectifier protects your capacitors against inverse polarisation. An SCR can handle some 10* the rated current for such a half-sine pulse, but be prepared to replace it occasionally - this depends on the precise waveforms in your circuit. If you increase the energy (I had once 1m3 capacitors and 20kA to make magnets) be prepared to hold all wires firmly and check all contacts, as bad contacts detonate. And with 250V DC, please use appropriate care.

My considerations about such a balloon are there: http://saposjoint.net/Forum/viewtopic.php?f=66&t=2520 The easiest I could imagine was a skin on a truss. Not extremely complicated then, but a very nice challenge.

Swede and German submarines do use fuels cells, yes. Said to navigate over 2 weeks under water, which is enough for a military attack, making nuclear reactors less necessary.

Plain bearings are not for high speed nor heavy loads, unless you can guarantee their lubrication and the beaing oil film. Use two ball bearings.

Your electrodes can be graphite, obtained from a 1.5V saline battery. Wash your hands afterwards! Use an acid, since salt would produce chlorine or rather hypochloride. Gases are produced at separate locations so they recombine little. Any amount of hydrogen produced by this method is not dangerous. Keep it in the tube.

From your other question it seems you know too little to handle them all safely (some are a bit caustic), so I suggest to seek someone to accompany you in the game, who knows the consequences and precautions. To the very least, wear protective goggles.

Zinc resists attacks not too badly because its oxide holds firmly on the metal and is impermeable. This is why steel is commonly protected from water corrosion by a layer of zinc. Vinegar won't make much to it.

You better mix the alpha emitter finely with the netron converter, since neutrons escape the material better than alphas do. A common alpha-to-neutron converter is beryllium, it's expensive and can be toxic. Lithium, in a safe chemical compound (=not metal) may convert as well. You don't need a foil. I suggest to compute the danger by neutrons before going further. As they's absorbed in your body, they "activate" some nuclides which get radioactive. When computing the danger of the "alpha" material, please remember it also radiates gammas, or if not, its children will, or impurities in your source. Other activities are fun as well, did you try them all?

Pity! The flat Earth IS very bad for your model. This is in fact what prevent a very flat re-entry angle, thus needing a brutal deceleration at reentry capsules. At a bigger object with worse mass-over-area ratio, the deceleration is limited, and it will impact Earth brutally. Gravity sling needs gravity at the right position, the rest needs serious engineering! Put some figures on it, it's challenging. I expect lucrative asteroids to be very compact, as ore needs gravity to separate the elements. These differentiated bodies result from the destruction of a big, compact and dense object.

I had searched for said formula and didn't find it... This may look strange in 21st century but I had to compute by myself the analytic solution for the heat profile, it took me one week. Even a 5cm-thick book devoted only to the propagation and the diffusion equation didn't mention a solution. But afterwards, I found one in: Introduction aux transferts thermiques, by Sacadura (in French, sorry) who uses a Laplace transformation with half-integer powers - I find my solution easier. DrRocket, if you know a third method, please tell the world! By the way, all analytical solutions suppose that conductivity and capacity are independent of temperature, which is brutally false in a brake. So FEM would be an answer. As for how heat splits between both materials, that'a a matter of model! People commonly assume a split proportional to sqrt(density*volumiccapacity*conductivity). Their rationale is that contact points share a common temperature. Well, why not.

It had been proposed to dispatch small power to many uses in aeroplanes, where optic fibres would carry both information and a few mW of power, thus saving the mass of electric wires. The best lasers (semiconductors) have some 50% power efficiency, the best photovoltaic cells illuminated by a single wavelength would have 50% if they were matched with the laser... Good news: semiconductor lasers can output hundreds of watts, like the ones used to pump other lasers - dangerous then. What is simpler? At a few cm distance, induction is pretty simple, and a pair of wires are even simpler. If your application shall produce light at a distant location, you might also consider producing this light where power is available and transport the light by lenses, mirrors, fibres or broad transparent guides (PMMA).

The direction of the magnetic field versus the current isn't simple - just consider that every electric circuit is closed, at least at DC or low requency. What you can say in DC or low frequency is that the magnetic field wraps the current and the current the magnetic field. The local force is perpendicular to both the local current and the local induction. The corresponding mathematical operator is called a vector product, it's zero if current and induction are parallel and maximum if they're perpendicular.