Enthalpy

And because the attached Xls have been lost here, I upload them again. EarthCargoDeparture.xls MarsCargoArrival.xls

The lowered perihelion transfer for a "short stay mission" is long known, also as "opposition-class" mission type. It is considered for instance in 2009 in Nasa's NASA/SP–2009–566 "Human Exploration of Mars, Design Reference Architecture 5.0" https://www.nasa.gov/pdf/373665main_NASA-SP-2009-566.pdf Because a short stay gathers less science and needs too long transfers (rays, microgravity) in wasn't favoured in 2009. Meanwhile, sensors on Mars' surface have shown that rays are rather benign there, and the astronauts can shield their house anyway http://www.scienceforums.net/topic/83289-manned-mars-mission/?do=findComment&comment=895610 so the long stay is a clear choice now. My corresponding spreadsheet here is NonHoMarsRadiusSlice5. ---------- And because the Xls are lost here, I upload them again. NonHoMarsRadiusSlice5.xls NonHoMarsInwardsOpposition2.xls

Electric thrusters need so much power that solar panels feed only a faint push. Operations near a planet, which takes stronger engines, lead to use a nuclear reactor which can't be very light and needs a big radiator. The cancelled Jupiter Icy Moons Orbiter Jimo (not the Explorer Jime) was such a project, and this drawing (thanks to Nasa) illustrates the oversized feeder for the electric engine: The reactor is at the tip, the "wing" is the 422m2 heat radiator, and from https://en.wikipedia.org/wiki/Jupiter_Icy_Moons_Orbiter the science payload orbiting Europa, Ganymede and Callisto would have been 1500kg, similar to what the sunheat engine promises - but Jimo would have needed chemical engines to leave Earth, so despite the electric thruster's higher Isp, it would have weighed 36t in Earth orbit launched in three heavy flights and cost 16G$.

Yes it's possible, sure. For instance the turbocharger of a piston engine is about half as powerful as the piston engine and is very small. A gas turbine alone would only be twice as big as the turbocharger. If electric engines are allowed to run as quickly as a gas turbine, then they're even a bit smaller then them. You can check this at a turbo-alternator: https://en.wikipedia.org/wiki/File:Turbogenerator01.jpg the three yellow casings host three pairs of low-pressure vapour turbines, the high pressure turbines are before, and the alternator (of same power necessarily) is in the small red casing at the rear. Then, you may ask if an electric motor running at 100m/s or more makes a convenient transmission to the wheels. Helicopters have such a gear. Intermediate situations exist. Electric cars have presently powerful motors that rotate not so fast and are typically located at the wheels. Find some drawings.

Hi Externet! Identical parallel wheels, same angular speed but opposite direction: no global torque is required to topple the frame BUT each wheel creates a strong torque, so everything but be sturdy enough. Two wheel axes perpendicular: nothing special, the net torque is the sum of both. The gyroscopic torque is the vector product or the wheel rotation (put inertia moments if you wish, I don't care presently) with the toppling rotation, hence perpendicular to both axes. For instance if the toppling axis is perpendicular to both wheel axes, you get two gyroscopic torques which are perpendicular to an other and add vectorially. Three wheel axes perpendicular: nothing special again. For instance if the toppling axis is parallel to one wheel axis, this wheel creates no gyroscopic torque, and the two other wheels do like in the previous case.

And they're made up of fibre optics.

No material withstands 8500°C. Either the plasma radiates little enough, is far enough, has a density small enough... and the walls have naturally a much lower temperature, or you'll have to cool the walls actively, whether you like it or not. Then, you must check if the plasma remain so hot despite the contact with the walls.

Hello you all! Here's a means to produce a sine wave voltage, very pure, with metrologic amplitude, whose frequency can be varied over 2+ octaves in the audio range - this combination may serve from time to time. It uses sums of square waves with accurate shape and timeshift. A perfectly symmetric square wave has no even harmonics. Adding two squares shifted by T/6 suppresses all 3N hamonics as the delay puts them in opposition; this makes the waveform well-known for power electronics. Two of these waveforms can be added with T/10 shift to suppress all 5N harmonics, then two of the latter with T/14 shift, and so on. A filter removes the higher harmonics as needed. The operation makes sense, and may be preferred over direct digital synthesis, because components and proper circuits may provide superior performance. Counters produce accurate timings. If a fast output flip-flop outputs a zero 1ns earlier or later than a one, at 20kHz it leaves -90dBc of second harmonic and at 1kHz -116dBc, but at 1MHz less interesting -56dBc. If the propagation times of the output flip-flops match to 0.5ns, at 20kHz they leave -100dBc of third, fifth, seventh... harmonic and at 1kHz -126dBc. 74AC Cmos output buffers have usually less than 15ohm and 25ohm impedance at N and P side. On a 100kohm load, the output voltage equals the power supply to +0 -200ppm. 5ohm impedance mismatch contributes -102dBc to the third harmonic, less at higher ones. Common resistor networks achieve practically identical temperatures and guarantee 100ppm matching, but measures give rather 20ppm. This contributes -110dBc to the third harmonic, less at higher ones. This diagram example would fit 74AC circuits. Programmable logic, Asic... reduce the package count and may use an adapted diagram. To suppress here the harmonics multiple of 2, 3, 5 and 7, it uses 8 Cmos outputs and resistors. As 3 divides 9, the first unsqueezed harmonic is the 11th. A counter by 210 has complementary outputs so that sending the proper subsets to 8-input gates lets RS flip-flops change their state at adequate moment. Programmable logic may prefer GT, LE comparators and no RS. I would not run parallel counters by 6, 5 and 7 instead of 210 as these would inject harmonics. The RS flip-flops need strong and fast outputs. Adding an octuple D flip-flop is reasonable, more so with programmable logic. I feel paramount that the output flip-flops have their own regulated and filtered power supplies, for instance +-2.5V, and the other logic circuits separated supplies like +-2.5V not touching the analog ground. That's a reason to add an octuple D flip-flop to a programmable logic chip. For metrologic amplitude, the output supplies must be adjusted. All the output flip-flops must share the same power supplies, unless the voltages are identical to 50ppm of course. A fixed filter can remove the higher harmonics if the fundamental varies by less than 11 minus margin, and a tracking filter for wider tuning is easy as its cutoff frequency is uncritical. The filter must begin with passive components due to the slew rate, and must use reasonably linear components. ---------- I tried almost three decades ago the circuit squeezing up to the fifth harmonic, and it works as expected. Squeezing up to the third is even simpler, with a Johnson counter by 6 and two resistors. Measuring the spectrum isn't trivial, for instance Fft spectrometers can't do it; most analog spectrometers need help by a linear high-pass filter that attenuates the fundamental. Marc Schaefer, aka Enthalpy

And who's to blame for that? Madrid's forces stole in advance the ballots, the boxes, and at that day blocked the voting rooms. The vote's organisation was the least bad adaptation to this pressure. Among the imperfections of this vote, you could add the 770,000 expressed votes stolen by Madrid's forces. And as well, the police and guardia civil beating the voters. Some could understandingly get influenced.

Hello everybody! Earthquake light is said to appear in the sky during some earthquakes https://en.wikipedia.org/wiki/Earthquake_light its mere existence is controversial and poorly explained. Several explanations have been proposed, I'm pleased with none, so I just feel the need to add my own piece of mess to the ambient chaos. Internet-era videos show short light reflected by clouds for which narrow sources can be seen on the ground. Electric sparks explain these neatly, prompting some people to reduce all observations to mundane causes. Though, earthquake light has been reported centuries ago and also over the Ocean, a big difficulty for triboelectric, ionic and mundane explanations. ---------- My attempt relies on vertical ground or Ocean movements transmitted to the atmosphere which propagates them upwards. As an example, I take peak 0.5m/s vertical speed and 2Hz sine, or peak 0.64g and 40mm. The wavelength is 750m in the Ocean, whose lower impedance can nearly double the amplitude, and 170m in the lower atmosphere. Supposing a plane acoustic wave (inaccurate but simpler), the impedance is 400ohm near the ground, this wave's peak pressure 200Pa and power density 100W/m2, and a 5s burst carries 250J/m2. If the tectonic plate moved vertically over 20km*20km, the peak acoustic power is pleasant 40GW and the burst energy 100GJ. As its density decreases very little over one wavelength height, the atmosphere transmits the power perfectly to the altitude through the dropping density and acoustic impedance. I see only turbulence that could hamper this transfer. We can take a constant sound wavelength, as the velocity depends only on sqrt(T) and on the mean molar mass. From 340m/s, it drops to 280m/s in the stratosphere, then increases to 320m/s, drops to 250m/s at the mesopause and increases again. Data is from pages 9/54 and 30/54 of "Atmospheric Composition and Vertical Structure" by Thomas W. Schlatter At 86km altitude, the density is 7mg/m3, the temperature 187K, and the acoustic impedance /4702. For our wave, The sound pressure is /470 or 0.4Pa, about the atmospheric pressure The displacement speed is *470 or 235m/s, about the sound velocity there. so the acoustic wave becomes a Mach wave, with strong and steep changes of temperature and pressure that propagate faster than sound. I won't try to estimate the Mach's wavefront thickness nor the propagation losses, sorry. Someone else shall do it. Admitting that the wave energy is kept, over arbitrary 500m wavelength now, thinner air at even higher altitude spreads this energy on less mass. Around 120km altitude, the density is 22µg/m3. The (arbitrarily) 3* longer wave spreads the energy on little air mass: 50J/m2/wavelength over 11mg/m2/wavelength. A sine distribution would give a peak of 9MJ/kg or over 4000K, and the Mach wavefront is even hotter, letting the air radiate light efficiently. At these 120km at rest, the molecular mean free path is 1.2m, so a sinewave of lambda/2pi=81m is still propagated, but at 150km the mean free path is 33m so the 2Hz sinewave stops approximately there, a shockwave supposedly too. It takes some 27km to multiply the mean free path by 2.7, and the wave energy must be lost over such a distance; if this occurs at 150km, the burst's 250J/m2 spread over 56mg/m2, and the losses heat the air to 4000K too, so it radiates light. Though, I expect the previous process to have already attenuated the wave. This latter dissipation happens at an altitude where our atmosphere is warmer and occurs for all causes on the ground, including Ocean waves and wind turbulence. It must happen also at our Sun's chromosphere, maybe corona. ---------- According to my model : Stronger earthquakes produce light more likely, vertical movements are needed, and the Ocean is no drawback; Direct line of sight is possible up to 1200km (400km were observed); Up to 40GW per front are available to produce light. At 100km it's as much as 40kW at 100m: room for inefficient conversion and for a hemispherical pressure wave, rather than plane; The light must appear over the strongest vertical movement and some 5min later. It must be broad (but refraction applies). ---------- The air movement at 1km/s in the 40µT geomagnetic field induces only 40mV/m, very little for a gas discharge. Bad alternative explanation to my eyes. The 4MJ/kg heat deposited at 150km would suffice to propel this air to hundreds of km height. Transferring the 0.1Hz movement to higher, thinner air amplifies the speed (and the temperature). As some air reaches the lower Van Allen belt, it must glow like any Polar light. Though, this light would last for about 5min. Marc Schaefer, aka Enthalpy

The importance of this question in Spain shouldn't be underestimated I can cite the example of Monaco, whose team plays in the French league. So calm relations would make it possible - presently they aren't. It would be extremely interesting, but how to know that? We may equally well suppose that the registered voters meaning "no" (the unionists) did not want to participate to a vote declared unconstitutional and dismissed by Madrid. So while some "yes" people didn't dare to vote, I find impossible to estimate any proportion. I put the figures here above because even if we suppose that all non-voters favoured "no", just adding the cast ballots stolen by Madrid's forces, with an assumption (=same proportion of "yes" as in the counted ballots) that I find reasonable, already gives a clear answer. ---------- The present mess results from the vote on 1st of October being very far from perfect. But the ones that use this as an argument caused it themselves. Independence itself is contrary to the Spanish constitution. But how important should it be as compared with the popular will? The French revolution was illegal too, and in France itself, the constitution was amended to make the independence of New-Caledonia possible. Which doesn't prevent the newspapers of France, where Northern Catalunya lies, to put these days "this would be impossible in France"... Many governments in Europe have their eyes on Catalunya.

The question on October 1 was: "Do you want Catalonia to become an independent state in the form of a republic?" https://en.wikipedia.org/wiki/Catalan_independence_referendum,_2017 The organization was highly disturbed as Spain's constitutional tribunal declared the referendum unconstitutional. Judges and the Madrid government ordered the police and guardia civil to prevent it take place. Much of the process was undercover and disrupted (some videos on bbc.co.uk). Consequently, the results are not verified independently, only announced by the separatist Catalan government: 5,313,564 registered voters 2,262,424 votes 2,196,709 valid votes 2,020,144 yes 176,565 no 770,000 estimated votes prevented: stations forcibly closed, boxes removed... So the measured turnout was 42%, but if including the (estimated!) prevented votes it's 57%. The "yes" makes 89,3% of all votes (including invalid ones). If extrapolating this proportion to the prevented votes, it makes 2,707,700 "yes". Even if supposing that all non-voters meant "no", the "yes" would be backed by 51% of the registered voters.

Hi Dionysus, hope to have grasped the description properly. The photon has a short coherence time and is split in two intervals. I will add the hypothesis that the two intervals are a bit separated, so that the wave isn't correlated in the two intervals. This avoids the intermediate cases as the end of the first interval is slightly correlated with the beginning of the second one. Whether you open and close the slits or not has no influence. The source that splits the pulse in two and directs the halves at different slits has already done that job. Whether you have one or several photons makes no difference. When recombining the two intervals, you get no interference, because they are not coherent. The narrow-band filter doesn't change that. It loses power of the wideband light, makes the half-pulses longer so that they now overlap, but their superposition will not be consistently additive at some constant places and subtractive at others, because their relative phase changes randomly, after the filter too. ---------- As opposed, you can make interferences with slits open at different times, provided that you delay the wave passed through the earlier slit. It would also work with the narrow-band filter and no delay, but needs a source with a coherence time that spans the two intervals. ---------- In such photon experiments, single or multiple photons use to make no difference. You can propagate photons like a non-quantized wave, and only upon detection and if needed, remember that some properties don't split.

I proposed on August 21, 2014 a single-photon source that isn't good enough. Within the considered time frame, it emits a photon with a small probability e, but it can also emit two photons with e2 probability, and this is too much. With the source and setup I described, the observations could even be explained with no photons at all. It would suffice to attribute to the target fermions (like electrons in a photodiode) a probability e to get excited by light of that intensity (understood as a field without quanta) and the probability of observing an excitation at both detectors would be e2. To make photons patent, the setup demands a source that has zero probability, not e2, to emit two photons. That's why experimenters use sources like single atoms (for instance a nitrogen atom in a diamond crystal) rather than the attenuated diode I had proposed. Then, if never observing two simultaneous excitations at the detectors, we have some reasons to say the photon, and check with additional hardware that the photon takes both paths but excites only one detector. Sidenote: this particular setup would leave other interpretations open. Light could have no quanta, provided that the emitting and detecting fermions have some separate means to coordinate themselves. Such interpretations get increasingly complicated if the emitting fermion has disappeared before a detector gets excited. They are not mainstream, but legitimate attempts.

It is well known, but not by every musician: several notes on the Boehm flute use an imperfect combination of open holes which hamper the emission or the intonation. Here are two examples of good notes, high E and high G. Following Obukhov where one note marked with a × is half a tone higher, the lowest line shows what notes a given tonehole can emit. On the flute they are nearly harmonic and have a pressure node at this tonehole's location, or more accurately, little below. High E and G open two properly located toneholes, which could each emit the desired note, and this reinforces the air column's resonance. It also spoils the unwanted modes of both individual toneholes, so that only the desired note resonates well. 3 and 4 being relatively prime in these examples, the next good resonance would be an octave higher, on modes 6 and 8. If a flute has no split E mechanism, the tonehole emitting G# remains open for high E and makes it logically less stable. Due to mechanical couplings meant for other notes on the Boehm flute, several notes use imperfect combinations of open holes. The high F# leaves open the tonehole for Bb and harmonics, half a note lower than the correct tonehole for B, making the high F# less stable than its neighbour F and G. The high G# opens the tonehole for C and harmonics, instead of the lacking tonehole for C#, so the high G# uses to be badly low. On most instruments, the high G# can't be fully corrected by the musician, who gets accustomed to play it out of tune. This is what flutists should test at an instrument. Play legato repeatedly the high F-F#-G-F#- as pianissimo as possible, check when the F# disappears: it tells how difficult the instrument is on demanding détaché, fast, piano sequences. Play legato repeatedly the high G-G#-A-G#- without any lip correction, or simple intervals like Eb-Ab, and check the intonation: usually very poor. Play legato repeatedly the medium and high C-C#-D-C#- without any lip correction, and check the intonation by the index tonehole misused by the Boehm flute for C#. And of course, try the lowest notes forte and the highest ones pianissimo, but this doesn't result from mere hole combinations. The explanation above is only a first analysis. Even the flute's huge toneholes are inductive hence placed too high. Opening sereval holes for the third octave shifts the notes higher. Makers of Boehm flutes adjust the toneholes' size and position ("scale") to improve the imperfections. But as each hole influences several notes, the adjustment is nontrivial and needs compromises. About every flute today uses the (1972) Cooper scale, improved by Bennett. Its high A, despite opening the ill-placed tonehole for G#, is stable and in tune. Its high F# is in tune but imperfectly stable, its high G# is badly low, and both C# depend on each model. The New Cooper Scale is allegedly better. I tried at a Paris repair shop the single only flute perfectly in tune because the expert had shifted the toneholes himself, but the low notes were weak. I tried around 2003 a new wooden flute by Yamaha with the "Type 4 scale" or its predecessor, which offers the strongest low notes ever and whose intonation is excellent, but soloist will supposedly dislike its soft tone. So while better scales than Cooper-Bennett exist for the Boehm flute (wake up!), this tinkering is by nature limited and implies trade-offs. Further gains can result from small or big changes to the Boehm system. Cooper had continued to experiment. For instance, he added at the thumb the missing C# tonehole. I ignore what mechanical couplings he foresaw and haven't tried such an instrument. By making the eight high toneholes independent, my fingerings never open the wrong one, and hopefully avoid all trade-offs. The scale adjustments must be done again from scratch. Marc Schaefer, aka Enthalpy

Hi Sensei and all, oxygen comes from the air, yes. This is what makes hydrogen much lighter than kerosene. Agreed with 51g/s oxygen needing some 0.2m3/s air. But this is little, especially in an aircraft where air moves already. Take 20m/s under the rotors, it's a D=0.1m intake. An other logic is that the helicopter uses car fuel cells, which get enough air when used in a car. The helicopter has 6 cells instead of 1, and it suffices that each cell has an intake as big as on a car.

At the main belt asteroids, Dawn observes the surface of Ceres and Vesta, other probes passing by have imaged half a dozen small bodies more, and telescopes give optical spectra from the surface of whole bodies. https://en.wikipedia.org/wiki/Asteroid_belt A mission to analyze them in situ and bring samples back would benefit to science, potentially to the extraction or production of propellants for farther trips, and hypothetically to the extraction of precious metals brought back to Earth. A return trip passing by many main belt objects needs a huge delta-V and a decent thrust made possible by the sunheat engine. It begins like the asteroid mining mission here above: an Ariane 5 or Atlas V 551 delivers the oversized 18.5t craft in orbit. Solar, chemical and solar pushes put the probe in transit to the main belt - 10.5t because the first target orbit in the Vesta family is at 2.35AU only but inclined 6.7°. Pushing 4560m/s there, in 132 days with 8 engines, leaves 7.3t at the first asteroid. Venus flybys may improve. The asteroids' actual "osculating" orbital elements look pretty random, but Kiyotsugu Hirayama saw that Jupiter lets them fluctuate. He computed "proper orbital elements" as mean values, and then the asteroids make clearer families supposed to result from shattered bigger bodies. https://en.wikipedia.org/wiki/Asteroid_family Sampling a few bodies in each family, plus some outside all families, seems a good plan. I estimate the mission delta-V based on the mean "proper" orbital elements, but the actual "osculating" elements differ much, so among hundreds of family members, a wise and well equipped mission planner would pick more favourable ones. To evaluate individual transfers, which can't await the best date to change the orbit inclination, I combine quadratically the polar component of the speed difference with only half of the ecliptic component and leave the other half untouched. Stopping at intermediate objects is for free, and because I've been pessimistic above, I neglect the orbit fine-tuning and the operations near each object. A well chosen set of target objects would change radically the mission duration and delta-V. The unoptimized sketched tour costs 10 693 m/s from Vesta to Eumonia families, leaving 3.1t there. Landing on bodies up to km size is for free and a spring lets lift off. Ask someone else how to analyze, scoop, dig, bore samples there. A Yag pumped by concentrated sunlight and a hydrogen gun shall perform remote analyses at bigger objects. I already described light samples boxes and sealing apparatus there http://www.scienceforums.net/topic/85103-mission-to-bring-back-moon-samples/?do=findComment&comment=823276 The science instruments can be discarded before heading to Earth, one optional hydrogen tank there too or a bit earlier, the structural truss early if possible. The craft brakes within the asteroid's orbital plane by 4724m/s in two kicks well spread over two revolutions in order to synchronize itself with the Earth and makes a 200m/s fine tune. Other transfers would be faster. If nothing has been discarded, this leaves 2.1t heading to Earth for aerobraking, say over Antarctica. The insulated cooled tanks, the structure and the engines shall weigh 0.9t, equipments 0.3t, experiments 0.3t, leaving 0.6t for the reentry capsule(s); dropping unneeded mass early would increase that. The 600kg comprise 29% structure, 21% heat shield, 13% parachutes, 7% boxes and 30% = 180kg samples from dozens of asteroids all over the main belt. Marc Schaefer, aka Enthalpy

Many companies and groups have flown drones and quadcopters from a fuel cell and hydrogen stored as a compressed gas or a liquid, as you guessed. As one example, Energyor Technologies Inc. from Montreal flew a quadcopter for nearly 4 hours in 2015 - videos available on the Internet. They imagined oilfield operations, powerline inspection... as their first customers. But build a bigger hexacopter (October 05, 2013 here), and this flight duration is fantastic for rescue and search operations. ---------- The explosion hazard with liquid hydrogen isn't as critical as I had believed, at least in air. Arthur D. Little Inc. experimented it in 1960 https://www.youtube.com/watch?v=7bFJK5kU_UQ https://www.youtube.com/watch?v=RNzjksIImb8 The first video shows from 2min50 to 6min18 spillages of 1 to 5000 gallons ignited late, and in the open air they didn't detonate, but deflagrated instead. Other questions were investigated, for instance the evaporated spillage remains close to the ground over 200m and propagates a flame over 100m. But with liquid oxygen (second video), detonations do occur, said to be less bad than with kerosene.

I'd suggest to listen to the TV in English. Try the BBC, CNN and the others. In the news, they speak out clearly, it helps. Differentiate the accents. If you learned with Texan teachers and listen to a Scots, it's perfectly normal that you need time to get accustomed. Pick a dictionary that details the pronunciation of the words. Learn to read the bizarre symbols and use these indication for every new word. Failing to understand spoken English may (or not) result from imperfect pronunciation on your part. In that case, train it by reading texts loudly with the help of the dictionary. You could choose online newspapers as the texts, to waste less time in that training. In case your mothertongue has no stresses (French, Japanese and few more), first get fully convinced that stresses and rhythm are vital both to speak and understand English properly. And if your mothertongue is anything but English, also get fully convinced that spelling and pronunciation are just decoupled in English - you must learn both for each word.

When estimating which material withstands a high temperature, the main property is its vapour pressure, not its melting point, because refractory materials use to evaporate too quickly rather than melt. This limits to some 3000K with tungsten, and quite a bit less with the best ceramics despite their higher melting point. Unless air or some gas is present, in which case corrosion (or call it oxidation or whatever you want) is often a much harder limit, and other materials like tantalum may be less bad then. Ar, Kr, Xe, halogens like in light bulbs put no further limit, but air does. So: what plasma temperature? Is active cooling possible? And so on.

Centre at 0 (zero) km depth according to the Chinese seismic service CENC https://guardian.ng/news/3-5-magnitude-quake-rattles-north-korea-near-nuclear-test-site/ https://www.cnbc.com/2017/09/23/north-korea-earthquake-suspected-explosion-china-says.html http://www.thestar.com.my/news/regional/2017/09/23/china-experts-say-34quake-hits-nkorea-in-suspected-explosion/ http://www.arabnews.com/node/1166141/world (by the way, the epicentre is by definition at the surface, over the centre) And USGS gives an uncertain depth -from the Guardian paper linked above): "The depth is poorly constrained and has been held to 5 km by the seismologist," USGS said in a statement.

On 23 September 2017, two USAF B1-B bombers flew in international airspace along North Korea's limits. They have 57t load capacity, maybe not in one chunk https://en.wikipedia.org/wiki/Rockwell_B-1_Lancer#Specifications_.28B-1B.29 On the same 23 September 2017, an earthquake of magnitude 3.5 happened in North Korea. This was 2.5 magnitudes less, or 180 times less energetic https://en.wikipedia.org/wiki/Moment_magnitude_scale than the magnitude 5.0 tremor caused by the 10kt explosion on 06 January 2016 https://en.wikipedia.org/wiki/January_2016_North_Korean_nuclear_test so it would correspond to an explosion of 56t of TNT. The raw figures and computations are inaccurate, hence the 57t vs 56t must not be over-interpreted. The nuclear tests were carried underground, which causes a bigger shake than a surface explosion. Air-breathing bombs are more powerful against soft targets than the same mass of TNT but I expect an even smaller tremor from them. Big kinetic impactors or bunker breakers would produce a strong shake. Did you see Kim Jong Un since then? I've only heard of the North Korean foreign affairs minister telling "America has declared war to us".

Why the launch cost per kg is significant: If a mission shall return materials to Earth, this needs propellants in big amount. Maybe they can be found locally, raw or processed, but maybe not. Asteroids containing metals usually don't have organics nor water, until some discoveries change that opinion. Up to now, few "main belt comets" are known, only at the outer edge of the main belt, not necessarily where interesting minerals are. Some "near-Earth" objects are more accessible to our rockets, but there are few of them, which reduces the chances of finding interesting ore there, and water isn't expected so near to the Sun. The main belt objects are at around 2.8AU from the Sun; just coming back from there costs 4.9km/s at the asteroid, and is free if braking in Earth's atmosphere. Our best oxygen-hydrogen rockets eject gas at 4.6km/s, so bringing pure precious metal (not ppm ore!) from there would need more than 2kg propellants for 1kg treasure. Depending on the script, the propellants must first be brought there, which costs much more than 8kg propellants for 1kg treasure. At 40k$ per kg of gold and 5k$ per kg of payload in low-Earth orbit, the numbers are unfavourable as is. But humans may have better ideas: Maybe near-Earth objects contains interesting materials after all. Or the goal isn't to bring them back to Earth but use them locally. We may have more efficient propulsion: http://www.scienceforums.net/topic/76627-solar-thermal-rocket/?do=findComment&comment=1014780 or electric propulsion, but the thrust is faint. Or solar sails; I see how to build them in hectare area http://www.scienceforums.net/topic/78265-solar-sails-bits-and-pieces/?do=findComment&comment=857978 maybe someone finds a means for the necessary square kilometres. Gravitational assistance can help, but it makes no miracle for the asteroids. Or we find or produce propellants locally. This depends on what prospector missions find. These too would dearly need a better propulsion. Launch costs can shrink with bigger launchers (Falcon 9 Heavy announces lower costs) or with reused launcher parts. Plus everything I didn't think at but other humans will. More likely, a combination of several points may bring the economics into the reasonable area in the future.

A team tries to break the 1991 record for human-powered boat record http://www.bbc.com/future/story/20170921-how-fast-can-a-watercraft-powered-by-humans-go this time propelled by vertical movements of the sustaining foil used like a flipper. On the newspaper's pictures at least, the foil's pillar has a crude connection to the foil's extrados, which must spark cavitation, ventilation and stalling. My suggestion would be to provide a fastening behind the trailing edge or even at the intrados, and let the pillar rise behind the trailing edge as I sketched here on June 04, 2012. I suppose a strong V shape isn't useful against cavitation at 20 knots, but it can give some pitch stability.

These codewords are used mainly by secret services and are not specific to politics. I've identified a few hundreds, mainly in French, but they use to be very similar at least within the Nato. Macaron = Emmanuel Macron Puissance = Nicolas Sarkozy Mythique = François Mitterrand Humble = pope Francis Consacré = pope Benedict XVI Pèlerin = pope John Paul II Dédié = Vatican (or catholic church?) Impressionnant = the Press Concerne = big company Malade (sick) = spook been caught Borderline = cross the border Parcours du combattant = sending troops Petit poucet = repatriation Chapeau (hat) = Israel (or the Jews?) Eldorado = Argentina Bonanza = Chile Etc etc etc You're welcome.