Enthalpy

To bring a payload from Low-Earth- (Leo) to a Geosynchronous Orbit (Gso), a Solar thermal rocket would use its small push all the way to save time, but this takes more performance than the usual very elliptical transfer (Gto). From an equatorial Leo (sea launch, Alcantara...) the required Delta-V is the speed difference between the low and the high orbit, if I didn't botch it. Starting from 7675m/s at 6366+400km to avoid drag, the transfer stage must add 4600m/s to achieve the 3075m/s at 6366+35798km. This costs 741m/s more than the Hohmann Gto. From other launch sites, the orbit's inclination must be cancelled. The very elliptic Gto does it at apogee where speed is small, but the continuous push lacks this possibility. Fortunately, isp=1267s absorbs this as well. Kourou reaches 5.2° inclination at Leo. To estimate the added cost, I keep the inclination over the first 2600m/s, and compensate it over the last 2000m/s needed for altitude; the side speed to cancel is 462m/s (begin) to 278m/s (if done at Gso), so I take mean 370m/s. The engines shall push flat for 2*90° per orbit, and for 2*90°, tilted as 1,11*370m/s * sin = 1000m/s (1,11 because the tilted push extends 45+45° from the optimum point). When tilted, only 91% of the thrust is equatorial, so these 1000m/s cost 1097m/s performance, and the overhead nears 97m/s, totalling 4697m/s to Gso. A Gto would waste 15m/s from Kourou's latitude. Cape Canaveral reaches 28.5° (and Tanegashima 30°), giving 3779m/s side speed at 400km and 1505m/s at height, for mean 2642m/s. Here I tilt the thrust as a cosine function over one orbit. At maximum tilt, the relative components of thrust are S and C, kept for all orbits of the transfer, which is not optimum. Only 0.5*S and nearly (1+C)/2 act as a mean, so side 2642m/s versus 4400m/s along the path leave 73.5% efficiency: the total cost nears 5986m/s and the overhead 1586m/s. This wastes even more performance than de-inclining at final altitude but saves time. The optimum is obviously elsewhere - someone with a liking for it shall investigate. I take 5700m/s. ================================================================= A Falcon-9 shall illustrate the transfer from Leo to Gso - click to view the drawing's full splendor. Starting from Cape Canaveral, the launcher puts 10,0t on a 28,5° 400km orbit. The Falcon may need reinforcement for the longer fairing. Minus the adapter, the transfer stage starts with 9350kg. To provide 5700m/s as estimated previously, it ejects 3440kg hydrogen at isp=1267s. 20 days thrust (plus some 5 days eclipse) take 10 Solar thermal engines with 4.6m concentrators. Not that huge. The balloon tank of thin steel, foam and multilayer insulation weighs 143kg. Polymer straps hold it to a truss of welded AA7020 weighing 205kg that links to the launcher and the payload. A cryocooler keeps the hydrogen liquid. Each engine weighs 100kg, of which 50kg are the concentrator and 20kg the chamber, using nickel or niobium rather than tungsten where possible. 300kg of sensors, datacomms, control and unaccounted items leave a payload of 4262kg in Gso. That's roughly twice the capacity of chemical stages. ----- Here the Solar thermal stage is expended at each launch and continues to a park orbit. It can also come back to Leo, what ESA calls a "tugboat": Reusing it saves launch mass, even though the way back needs some hydrogen; It can bring a satellite down to Leo for repair; A lighter launch mission can bring extra hydrogen for a following overweight mission; The launcher can bring the hydrogen and the satellite separately. This puts in Gso the full launcher's Leo capacity; A flexible long-range vehicle between Leo and Gso can bring resupply or remote repairs to several satellites, push aside the lost ones... Marc Schaefer, aka Enthalpy

Because I'm outdated.

Would a graphite electrode work for your water electrolysis? For my teenager experiments, it was good enough, while the drawbacks of copper were obvious. Pencils are not pure graphite, but the central electrode of a saline zinc battery is. For electrolysis, the contact area with the liquid matters a lot, hence a wire would not be my first choice. I'd pick something like a copper foil (or a printed circuit: 35µm copper on epoxy +glass fibers) plated with few µm gold.

No. The weak interaction does.

What is suggested here? David Charles Hahn collected radioactive materials in a setup that had zero chance of becoming a reactor. The Liquid Fluoride Thorium Reactor Corporation was founded by a different person. Some companies have begun small, it does not imply that beginning small brings success. Already the size hence cost of a reactor does not fit a single person; Fermi had a university with him. What's sure: a pressure lobby exists for liquid fluoride thorium reactors. As such reactors have clear drawbacks (explode as a bomb if hit by a bigger kinetic energy penetrator - still need uranium reactors) and few chances to bring something useful, the goal of their proponents must only be to draw taxpayer's money for their "research".

High frequency spindles for machine tools shall offer the highest angular speed for a given torque or power. Even if not required simultaneously, bigger maximum speed and torque from the same motor let the spindle accommodate more varied tool diameters - but this demands a higher possible linear speed from the motor. For instance the TCV-2 from Peronspeed illustrates it: http://www.peronspeed.it/scheda1.asp?idserie=6 for 10kW and 40,000rpm, the motor's gap of D=64mm (drawing there) runs at 134m/s already, so its stainless sleeve must be the limit, and winding graphite fibres instead, or a thin long steel sheet, improves it. Would friction stir welding benefit from higher speeds? This paper investigates 24,000rpm: http://www.niar.twsu.edu/researchlabs/ajt_presentations/Widener%20-%20Paper%2038%20-%20Presentation.pdf to reduce the forces. Marc Schaefer, aka Enthalpy

Crank. Any security breach in a small reactor is as dangerous as in a big one, so the security cost cannot be downsized, making small reactors meaningless. We have no significant uranium deposits to replace coal. It's under 1 to 100. Thorium reactors don't exist. No single one has ever run. Thorium reactors would need plutonium to start but don't produce it, so each thorium reactor would need several uranium reactors. In other words: they can't exploit a significant amount of thorium, because the available 235U limits them. The same marginal gain is already obtained in VVER by burning recycled plutonium supplemented with some thorium. At least it needs no new reactor. You should check the effect of a kinetic energy weapon on a fast neutron reactor. Prompt critical with tons of fissile material, instead of kilograms in a plutonium bomb. Meaningless claims about LFTR work better in a non-scientific forum.

Conformal mapping works (sometimes) in 2D, that is when the electrodes run parallel to an other with a uniform section over an infinite extension. I dreamt about an extension to 3D, didn't find how to begin with that (quaternions? Their differential calculus remains to be invented), and gave up; I haven't heard about someone succeeding in this attempt. More generally, zero method succeeds on real existing shapes. Algebraic solutions have been found for spheres, bifilar cables... But for a resistive canal in the ground, every attempt is futile, Boussinesq as much as the others. Either model the canal very grossly with a simple shape, or go to computers and finite elements. ===================================== Phase connected to the canal ground: there is no limit to the extension of the current except Earth's size. Some (small) current will flow farther than the position of the return electrode, which is probably the next transformer making your 120Vac and its grounding electrode. Though, we can try to estimate the distance where the injected current is less harmful. Imagine that the current spreads uniformly on a hemisphere (not realistic, but simple) up to the distance of the return electrode (and decreases faster beyond that distance). Let's say that 1mA in 1dm2 is not immediately deadly for humans (but painful, and harmful over time for living organisms), then 100A must spread uniformly in 1000m2 or 13m radius. Non uniform conductivity like the canal can make it worse. And anyway, little predictable conditions (like a conductive body and a dry soil) must let take huge margins. Worse conditions exist when a medium or high voltage cable has fallen to Earth. People can get killed by walking on the ground, due to the potential gradient. First-aid workers learn to abandon victims of high-voltage until switched off and forbid access to avoid more victims. Bolt impacts also can kill through the potential gradient in the soil.

Water combines uneasily with electricity. Even when water doesn't short the current path, one always gets corrosion from the voltage drop. De-ionized water leaks little electricity but corrosion introduces ions quickly. The pressure drop is not trivial at all. It can be estimated from experimental curves, taking all bends into account, plus some magic like the tube smoothness, the inlet shape... This will require to invest some learning time (knowledge reusable in the future). Usable books are scarce, because most ones tell only the scientific-looking tensors and differential equations which lead to nothing, but very few ones give the ugly empirical equations and curves that are poorly justified and take pages and pages. If you read German (I haven't seen it translated), one perfect book is: Technische Fluidmechanik, from Herbert Sigloch

I have absolutely nothing against 3g acceleration (starting from an airplane carrier is similar) nor 500km/h by ground effect (the Soviet Ekranoplane did it over water). Pitch stability is passive, with a front and an aft wings. 3g is out of proportion with 500kh/h. Aeroplanes reaching Mach 2 accelerate at 1g+. What I doubt is how it shall turn. Ground effect wings must keep near the ground, and then you can't roll the bike to turn. It would take big vertical surfaces to turn, but check the minimum radius for, say, 3g at 500km/h: impossible in a street for instance. To determine a wing size, take a known Ekranoplane http://en.wikipedia.org/wiki/Ekranoplane and scale the area as the mass divided by the square of the speed. Wings for subsonic flight, and especially for ground effect, are straight.

For a Printed Circuit Board? The only one in use is iron perchloride, FeCl3. It should be pre-warmed slightly (like 35°C) for speed, and stirred to achieve a uniform etch rate. It makes horrible spots on clothes (wear an overall) but is little corrosive and harms skin not too much - though, it does etch copper, something not obvious, and doesn't etch the underlying epoxy. Other mishmashes would etch copper but have drawbacks, like dissolving epoxy or the fingers. Fun: with accomplices, we used 35kg or perchloride to etch away a 2kg aluminium tube that had given its shape to our graphite-epoxy tube. Aluminium let the perchloride boil so it spurted from the tube and we poured it in again. That operation was dirty for good.

It's the weak interaction that transforms electrons and protons into neutrons to make a neutron star, whose density results from the density of neutrons. Gravitation doesn't achieve this density; it only makes the electron absorption more probable than the electron emission.

In any tokamak, laser, magnetized target, striction fusion, it's heat that supplies the energy to overcome electrostatic repulsion, and not the macroscopic EM field. Heat is reasonable, because nuclei hit or near-hit an other many times, so the energy invested in their speed has some chances to make a fusion and be useful. In contrast, accelerating nuclei to collide them once or a few times by bombardment would give a probability of fusion far too low. The macroscopic magnetic field in a Tokamak only serves to keep the plasma together so the invested heat really serves. To do so, the macroscopic field can act on the nuclei over a macroscopic distance: it's the energy that counts, not the force, giving the advantage to the bigger scale. Widdekind, you underestimate other people once again. Sakharov was not a moron, you know. Tokamaks may have other drawbacks, like the radioactive pollution resulting from neutron multiplication needed to breed tritium, but they do fuse nuclei. And by the way, so does any fusor, built by amateurs using easy fields http://en.wikipedia.org/wiki/Fusor What do you mean by "overcome strong nuclear force"? The strong force uses to be attractive, at least at the time scale of a thermal collision. And what is a "relativistically compact object"?

More questions... I imagine that mass does not change quickly, nor does a single mass accelerate or oscilate - only two or more bodies can interact and they keep their center of mass inmobile in this process. This is why gravitational waves are not dipolar (which would have corresponded to: the single mass oscilates between right and left) but quadripolar, resulting from the generating masses alignment changing between aligned and transverse as seen from the observer. The wave's frequency is also twice the masses' orbital frequency. Is that any reasonable? Keeping the analogy with EM waves for want of understanding gravitation, I figure that masses close to an other or moving slowly create a near-field quadripole that decreases as 1/R3, which is not called a wave (is it?) and does not propagate. In addition, because gravitation propagates at a finite speed, when the masses move quickly enough as compared with gravitation's propagation time, the "phase difference" prevents the 1/R2 terms to fully cancel out, and a significant power is radiated as 1/R2 which is then called a wave. Does this make sense? I've seen a formula for the radiation by a pair of stars with a speed well below c. But is the power radiated by an ultrarelativistic object known? Several detectors in service have seen no wave up to now. Is that normal? Have attenuation processes been proposed for gravitational waves? Have methods been proposed for humans to create our own detectable gravitational waves? I mean, not the rotating bars which produce a near-field only - no, a real far-field wave, even if far means just 10m away. Thank you!

Aeroplanes use to fly higher to be fast. Racing is at low altitude for the show and because pylones mark the base distance. I could imagine that, as piston engines give more power with denser air, the penalty of higher resistance is less crucial for them.

To my meager knowledge, plants have converters for red and for long blue light. Removing the infrared from the Solar spectrum may avoid excessive heat. Adding short blue or violet would bring only trouble if the last converter is for long blue. More: it's possible that both the red and long blue receiver must operate to sustain the plant's metabolism, in which case the red light can't be removed. It would be a surprise if plants, who have been there for long and evolve quickly, were not optimum for Sunlight as it is. Let's see what more knowdegeable people mean. Some plants grow industrially under artificial light, so the answer must be known.

If you access the compressor, its shape and noise should tell you much, doesn't it?

Fun, because not only chemists have this thought. It's even more obvious when reading the doc: no description of capabilities, no explanation for use, only a list of menu actions - with zero introduction nor a single synthetic paragraph, according to programmers' habits. And guess what, even electronic engineers say "again a programmer's design". Sure! But beyond that... - You need a broad technical background to develop anything - The diplomas define just a small part of one's knowledge and capabilities - Having used varied instruments, preferibly in different labs with different goals and working habits, matters most.

One may call a few autists savant, it does not need savants to be autistic. Eccentric does not mean mad. "Many of" and "commonly accepted"? This is not part of a logic, but of an attempt to mislead the readers. About all the "logic" of you message is twisted. And autists are a small minority, including on this forum. Sorry for professionals who look for new customers, sorry for the year of autism.

My answers to some points evoked here - sorry to be late... Interstellar travel does not exist, not even as a proof-of-concept, because we have no propulsion for it. A manned travel to Mars for instance would take under 100 days. Take submarine crews for that, they usually don't get crazy when confined over this lapse. Radiation pressure is 4.5µPa near Earth. This is 68µN on a 4.4m dish. It's the very reason why we don't use it every day for space transport. 2N by my Solar thermal rocket is unconveniently little, but usable for some missions. That said, I do like Solar sails, but we still need comfortable solutions for hectares and square kilometers of sail. I will not detail how to unfold and control the concentrators. This is not new technology; spacecraft designers do it better than I, for cases already much more difficult than the engine I describe. Multi-meter telescopes in space make pictures limited by diffraction, far below the micron. A concentrator that focusses Sunlight to make heat is nowhere as difficult. Its accuracy compares rather with a radio dish antenna, both in shape and pointing, for which a standard carbon honeycomb is perfect. The thrust must be arbitrarily orientable versus Sunlight. From Earth to Mars for instance, the craft would accelerate perpendicularly to the Sun's direction, but decelerate strongly Sunwards. Other missions have still other needs. In short: steer in all directions. If it simplifies other parts, especially the chamber, an added mirror (1-1.5% light loss, little mass, limited cost) is perfectly welcome. Steering without excessive optical aberration is nothing obvious, and I'm happy that my three mirrors show it's feasible, though optics designers will find better combinations. Any spacecraft will cumulate several concentrators (a reasonable number for some missions and designs) so the craft will control its attitude from independent orientation of individual engines.

You don't get a sunburn under clouds.

Instruments are very often developed by users. Including user companies. Especially innovative instruments. Not just in chemistry. It seems that knowing the use, or the need, is more important than knowing how to fulfil it.

This is how the chamber could be made, I believe - new developments always bring surprises. Hot parts are of tungsten alloy. Spark machining shall make the many thin deep shapes, and an electron beam weld the parts. Click to magnify the image. and the front view: The Sun's virtual image (D=38mm, 20kW and 18MW/m2 from 4.4m concentrators) enters the heater's cavity (40mm) with 1:1.85 convergence. The heater absorbs light and transfers heat by conduction to hydrogen in channels. 63µK*m2/W through tungsten and <37µK*m2/W through hydrogen drop only 130K at the heater's beginning, with ~1.3MW/m2 absorbed there and 60% reflected. At depths where direct and reflected light have dropped, helical fins in the cavity increase the absorption, and a converging cone as well. The bottom finishes gently to heat the hydrogen with little drop. The heater's outer stern would radiate much (2800K and e~0.32) but the regenerator's inner face reflects it (a=0.02). The absorbed fraction (~1500W) pre-heat hydrogen by 520K. A ruminator surrounds the incoming light cone to absorb much of the light emitted through the cavity's inlet and transfer it to hydrogen (+1060K): of 4380W from a 40mm blackbody, an infinite cone would catch 3320W, but 340W less if truncated to D=200+38mm (sketched shorter). The nozzle's throat (22mm) and upper divergent emit >1320W light; cooling regeneratively the lower divergent would save much of it. The regenerator holds the chamber and nozzle by the less hot hydrogen inlet, and the regenerator itself holds by its cool hydrogen feed. Wall conduction (~800W at the cavity's mouth) thus pre-heats the hydrogen. Marc Schaefer, aka Enthalpy

And you'd have noticed very distinctly if you were inhaling chlorine, well before a dangerous brief concentration. Yuk, cough.

Do you have a source for this claim? Toluene and xylene replace benzene to avoid causing cancer.