Enthalpy

In the Zeeman effect, the external magnetic field works on both the intrinsic and the orbital magnetic momentum when available. http://en.wikipedia.org/wiki/Zeeman_effect#Example:_Lyman_alpha_transition_in_hydrogen

That would aprroximately keep the pressure at ground level as said JC, or 92 bar http://en.wikipedia.org/wiki/Venus cooling to mean 288K would bring CO2 to the limit of gas and liquid http://en.wikipedia.org/wiki/Carbon_dioxide , especially http://en.wikipedia.org/wiki/File:Carbon_dioxide_pressure-temperature_phase_diagram.svg so CO2 would be gaseous at altitude, with some liquid existing near the ground locally in colder regions. These seas could not preempt all the gas, whose pressure is needed to keep some liquid. I have no suggestion for a practical method.

2 days would be a short delay on a forum... My small contribution: 2CaO + 2Cl2 -> 2CaCl2 + O2 at room temperature, each (without 2*) heat of formation in kJ/mol is: -634.9 and 0 -> -795.4 and 0 and each entropy in J/mol/K: 38.1 and 223.1 -> 108.4 and 205.2 and each heat capacity in J/mol/K 42.0 and 33.9 -> 72.9 and 29.4 I haven't done that for two decades (have a software now for rocket combustion) and I'm not a chemist, so I hope they will jump in with the figures provided - believe them, not me.

Hi Huma, could you tell us a bit more about your project? I built Sara over 20 years ago in a club. http://www.corsud.net/leau/Micro_satellite_SARA.html Is this a paper project, or will you build it? What is the available know-how in your team: individually, and as a group? I mean practical knowledge, what have you already done? My first comments: This frequency is for amateur radio. You can use it only if your satellite is for amateur radio. It's also an ISM band but only in region 1 - improper to satellites - and anyway, data transmissions are not ISM. In some countries, for some uses, governmental agencies accept datacomms in ISM bands BUT (1) not everywhere, not always (2) improbably when this ISM band is in a radiocomm band (3) not on a satellite, whose tranmission spreads over a huge area and all around the world. So in case the purpose of the satellite is not amateur radio, you'd better go to a frequency band for satellite communications. We did the error for Sara, it raised worries. Go to you national radiocomm regulation agency, they will tell it clearly. I suggest that you practice the reception of amateur radio satellites. http://en.wikipedia.org/wiki/Amateur_radio_satellite This will tell you much more than any book. Do it before you freeze such details like 256kb/s or bpsk. The signal amplitude varies a lot, you want to detect first the carrier despite the unknown direction and the big Doppler effect - so the modulation shall adapt, like low-datarate AM first, and if the signal is strong, bpsk, quadrature, constellation. Do you need to build the transmitters and receivers? The ones on board, the ones on the ground? Buying the ground station (amateur radio bands helps then, sure) save much time, but then your modulation must be compatible. Do you want to build a complete receiver with digital signal processing? Or can you maybe buy the IF+ADC+Processing+software part, and just add the up- or downconverter to the proper frequency? Find a kit, or a detailed description in an amateur paper or book?

Once again, an idea becomes a physical law if it's in a book... In vacuum only. There is no vacuum in a normal solid, since electrons occupy all the volume. Zeolithes are one exception. Then, one should think at what a speed means when the distance between so-called emission and absorption is much less than a wavelength. And the delayed re-emission would keep the wave impedance, while dielectric materials don't. Plus, light diffusion by individual atoms can be observed directly, and it introduces no delay. Only in countries where said book is common. Elsewhere, this explanation sounds bizarre. Anyway, I didn't want to open an argument here.

Take an engine that accelerates air from 2000m/s to 3000m/s (a Vasimr is bad for that). At 20% efficiency, audacious incoming 100MW treat 8kg/s air. This pushes 8kN. Without any acceleration nor climbing, just from overoptimistic lift-to-drag = 5, it lets fly a 4t aircraft, oh good. Just for the landmark, an RD-171 rocket engine http://www.lpre.de/energomash/RD-170/index.htm burns 2393kg/s of propellants, of which 659kg/s (more than one bathtub per second) are kerosene and the rest oxygen, so the thermal power (producing much CO) is around 23GW or 17 nuclear power plants.

The heat of reaction is computed from a table that lists the "enthalpy of formation" (search keyword) of the compounds. This enthalpy is computed with reference to the elements in their normal state, so for the second line of the original post, it takes only the values for liquid H2O (-285.8kJ/mol) and for aqueous NaOH (find for instance the enthalpy of formation of solid NaOH (-425.6kJ/mol) and its enthalpy of dissolution). Energy for free: no, the energy needed to regenerate metallic sodium exceeds what you get from reacting it.

I wouldn't be surprised if the "iron-rich microsphere" produced by fires were iron oxides mixed with other solids. These would still qualify as iron-rich. But could we reduce iron oxides at heat in vacuum? Concentrated sunlight can make up to 5900K theoretically, and the top of an oxide heap needs no other mechanical support. That would cost vacuum but save coal - cleaner, probably not cheaper. Or copper, nickel, cobalt, molybdenum, tin, lead, which seem easier.

Last time I checked the price of batteries, they were affordable. It's more a matter of lithium availability than price, presently - hence the attempt with sodium. The battery solution works in Japan, at least as a demonstrator, to smoothen out the demand, because most nukes are stopped and the running power plants can't cover the peak demand. Wind energy is presently the cheapest renewable (cheaper electricity than from the planned EPR nuclear reactor), hence thinking for it is reasonable. A first answer is to transport electricity over big distances, from places where wind blows at the time it's needed; this costs some power lines but is long done (13GW over 800km from Itaipu, 16GW over a similar distance in Québec, and more) with small losses. In Europe, wind would always be available among Scotland, Brittany and Galicia. I don't want to smoothen out the production by using other energy sources. This would mean that (1) we still emit dioxide, while the goal should be zero (2) we would have to operate backup plants, making wind energy too expensive. The amount of electricity to be stored demands good methods. Some of them look possible, more must still be invented. Imagine one giant 5GW wind turbine that produces mean 1.5GW. Providing this power over 1 day (with interconnected regions) needs to store 130GJ. That's for instance <26,000m3 air at 500m water depth: a half-ellipsoid bubble of 10m height and 70m diameter, smaller than the wind turbine - and at the same pressure as water essentially, so it takes just a strong plastic film and good anchors to hold it down. Or it's a ring-shaped island of 290m diameter where water is 40m lower than outside, where 5m water are pumped or turbined. It looks less cheap than the air bubble, but many turbines can share one island, whose wall length increases slower than the storage area. My flywheel design is meant for 12GJ a pair (hence 10 pairs per giant wind turbine) and I estimated the cost at 570k€. http://www.scienceforums.net/topic/59338-flywheels-store-electricity-cheap-enough/ while not extremely cheap, they would be cheaper than presently building extra power plants to cover the peak demand - and are the most efficient storage method over a day. My general feeling is that hundreds and thousands of brilliant scientists invest their work, and the society many billions, to get nuclear fusion or fission reactors that won't work soon and will be expensive, while some millions would permit to store electricity at the proper scale - and the electricity source is already here. Believe me, this intellectual endeavour is an interesting and challenging one.

Once again: how big the impactor, at which velocity, to deflect what size of geocruiser? How big the launcher? Because, figure that out, these are the questions that stop the experts from answering "we know how to do". Picking their list of research directions, of which experts know they're impratical, and adding your priority sequence based on unjustified reasons, brings little.

The reverse operation is called a fuel cell and it propels several marketed cars. Neither electrolysis nor fuel cells are very efficient. 60% each is a mean value. That would not suffice, by far, as an energy storage for electricity networks. Present applications concentrate on cars or on laptops. I see a use in aeroplanes and helicopters. To store efficiently excess electricity from networks, batteries are not too bad. Almost acceptable efficiency, cost affordable. Lithium is too scarce for that use, so one Japanese university researches batteries based on sodium. Alternatives: pump and turbine water between two lakes at different heights; that has been done for decades. Or have flywheels (very efficient, looks affordable), store air under bags on the sea floor (could be affordable from my estimates), pump water out of a ring-shaped artificial island built on shallow sea floor (prototyped in Belgium, cost?). Very few methods are cheap enough. For instance voiding a stiff container at the seabed is worse than the air bags.

I did read the post, and that's exactly why I ask and re-ask: What power? How? which, because engineering is all about figures, means: How much power do you need? How do you transmit that much mower? and also: how much thrust do you need, how much does the Vasimr provide? As a side question: what sort of ions can the Vasimr use? Does it accept oxygen? To be clearer, your suggestion fails at this. But I had preferred to formulate it as a question. Many attempts want to breathe air when at "low" speed (for a launcher) and altitude, then switch to a normal rocket. I dislike them all, because (1) They cumulate several technologies, hence cumulate the worries (2) A medium rocket weighs 600t at lift-off, an A380 400t. All wheeled and winged attempts need to be huge hence heavy, take giant runways, possibly fly very fast at take-off with all associated drawbacks. (3) The speed they bring is small! Mach 6 is only 2km/s, launching just to low-Earth orbit needs like 9km/s. The remaining 7km/s are uncomfortably much for a single rocket stage, even more so if the air-breathing stage isn't separated, while two-stage rockets reach Leo easily. (4) The commercial business is Geosynchronous transfer orbit (or even geosynchronous orbit). 2.5km/s aren't attainable by an airbreathing plus a rocket stage, while several launchers do it in two stages. Reusing the lower stage will work with standard rockets. (5) Imagine the airbreathed 2km/s come for completely free: this gains only a factor of 2 on the launching mass. Launch costs result from complexity in design and operation, not from kerosene amounts. Rockets can't afford the same development effort as airliners. (6) But reusing an already developed aircraft as a carrier is more sensible. Only for a small launcher, with a small gain, the interesting part being to launch from the Equator without paying a spaceport. The tiny Pegasus already needed a B-52; a MiG-21, F-4 Phantom or SR-71 would carry nothing. I understand Skylon as a technically very interesting attempt at a faster airliner, disguised as a launcher because Esa is only a space agency as opposed to Nasa. Presently, their take-off speed bans them from commercial airports and airlines.

Ô Hprime, did you find a way to let Excel compute with arbitrary or extended precision? Up to now, I observed only 16 digits accuracy from Excel, that isthe normal accuracy of 64 bits floats. A 0.25 difference would then limit the comparison to numbers like 2.5e15, that is, the 87 first members of the sequence. You may compute some more terms if using an approximation for (3/2)n-2k, through [(3/2)n/2k-1]*2k, where you assimilate ex-1 to x. Though, this game too will stop early. ---------- Also, you wrote "I have no computing power", but if your Excel runs on Windows, you must have JScript and VBScript available. Type a .js file with text editor, launch it. Similar to C, with typing less annoying than C++ (and 64 bits precision from what I've seen, unles a multiprecision library exists) http://wsh2.uw.hu/index.html Excel can also be programmed in VBA (visual Basic for applications). Besides Maple and similar algebraic programmes, you could write your own programme in Lisp, which has built-in arbitrary precision and rational numbers. Some Lisp interpreters are free or demos, but I don't remember which one I used among CLisp CormanLisp LispWorks (the personal edition has a heap size limit, bad for this use) there are many more. You could check Lush as well, this one is free (for Linux or for Cygwin on Windows) but I didn't try it http://2.lisp-lush-development.lisptalks.info/ http://sourceforge.net/projects/lush/files/

What power? How?

When pumping lasers with sunlight, say at a Europa mission, my filter might also direct to the lasing ledium only the useful wavelengths, to limit heating; it must be inserted where light is parallel. A good 200mm mirror would concentrate light to a 100mm spot from 20km altitude - if only the pulsed laser produced a perfect beam. 150W mean optical power evaporate Europa's surface thanks to the short pulses. If analyzing the shallow surface isn't enough, one could build a hydrogen gun on the space probe, to shoot dense bullets like 1g at 3km/s. These will penetrate deeper in ice, and the probe can shoot 10,000 of them of varied composition to map the moon. Marc Schaefer, aka Enthalpy

Already an "oops"... Back from Mars in 80 days needs 9622m/s asymptotic speed there. As well, the optimum share expects 1927m/s asymptotic speed from the chemical engine, and because it means only 1.7% more start mass, I request even 2927m/s from it. Then, the Solar stage provides 6695m/s, starts at 36.1t and expels 15.0t, still using 44 ten-meter concentrators. The chemical departure stage provides 2241m/s at the 200km, 3454m/s Mars orbit, by burning 23.9t; one or two RL-10B shall push the initial 61.7t. Reentering Earth's atmosphere at 17643m/s versus ground still holds, but this implies 4.0G downforce, or combined 5.6G if the drag equals the lift. The wing area is reasonable, since the chosen altitude tunes it. --------- I've found no good way to leave Mars with the Solar engine only. Lagrange points take weeks to reach at Mars or Earth. An elliptic Martian orbit is easier to reach and leave from Earth, but its orientation is too costly to change and differs between arrival and departure; it's also hard to reach from Martian surface, unlikely in one stage. A high circular Martian orbit is even farther from the surface; that's a backup design. A short trip without aerobraking at Earth would be difficult even with the Solar engine. --------- A trip slightly longer would save much mass. Maybe my shield setup or an other permits it: http://www.scienceforums.net/topic/80982-shield-astronauts/ If a leg lasting 180 to 200 days becomes acceptable, then the same 9622m/s asymptotic speed at Mars departure enable to pass at 0.85 to 0.65 AU from the Sun between Mars and Earth, and this permits to stay 31 to 212 days on Mars instead of two years, as computed with NonHoMarsInwardsOpposition2.xls there http://www.scienceforums.net/topic/83284-non-hohmann-to-mars/#entry807661 One can save mass for the short stay option as well: with 7000m/s asymptotic speed to leave Mars, the leg takes 220 days to stay 17 to 52 days on Mars. It all depends on shielding. Marc Schaefer, aka Enthalpy

An interesting option is to go nearer to the Sun between Earth and Mars. On this portion, the vessel has a higher angular speed than both Earth and Mars; properly done, it permits to lead Earth when arriving at Mars, and then the crew can stay shortly on Mars during the planets' opposition, instead of waiting two years there. Because this option adds a portion to the Earth-Mars trip, the travel is longer. The necessary performance would also be much for chemical engines. This spreadsheet for Excel, Gnumeric... is to evaluate such a trip - sorry for the mess. Here one shall choose the perihelion and the speed there; the spreadsheet determines the speeds at Earth and Mars, and the travel and stay times. NonHoMarsInwardsOpposition2.zip Marc Schaefer, aka Enthalpy

Yes, I realized that meanwhile. Thanks for explaining, I don't have to do it by myself.

The sunlight concentrators can fulfill more purposes at Europa or elsewhere: As the reflector of a high-gain datacomm antenna. To concentrate sunlight on an electricity generator: http://saposjoint.net/Forum/viewtopic.php?f=66&t=2051 To pump with sunlight a laser, maybe Cr:Nd:YAG. The laser beam might evaporate points of Europa's surface for remote analysis. To pump a laser that transmits data. Consider my filter at the receiver at Earth http://www.scienceforums.net/topic/74445-evanescent-wave-optical-filter/ Marc Schaefer, aka Enthalpy ==================================================================================== Here's how a chemical engine and the Solar thermal one can share the performance to escape a planetary orbit and achieve an asymptotic speed, with more details than http://www.scienceforums.net/topic/76627-solar-thermal-rocket/#entry754921 A chemical engine can provide a brief kick near a planet which brings much asymptotic speed according to Oberth http://en.wikipedia.org/wiki/Oberth_effect the optimum share is when a relative variation of the begin-to-end mass provides the same speed variation from both engines, including the multiplying factor by Oberth effect. isp=465s for the hydrogen+oxygen RL-10B and heirs, isp=392s for a kerosene+oxygen engine for GTO and escape missions http://www.scienceforums.net/topic/73571-rocket-engine-with-electric-pumps/page-2#entry772828 give an optimum share at 4298m/s (18.3km2/s2) and 3530m/s above Earth's gravity, 1934m/s and 1589m/s above Mars', but: This neglects all inert masses. Two-stage launchers prefer less. This optimum is very broad. 1934+500m/s from Mars loses 0.4% mass overall, 1934+1000m/s 1.7% - room for other constraints or preferences. Marc Schaefer, aka Enthalpy

If someone can propose a film as the concentrator, I have absolutely nothing against, sure! Sunlight must be concentrated from a D=4.57m reflector to a focus like d=20mm. While heating does not need an optical quality reflector, it does need a resulting Sun disk nearly the minimum size - if not, the too big hydrogen heater would lose more power through its radiation. I couldn't think of a film setup accurate enough, hence the ultra-thin nickel with stiffeners, as for dish antennas. Deployable film reflectors exist for radio dish antennas, but their wavelength is less demanding. I also like that 4.57m concentrators (or 10m launched by the SLS) allow to test individual engines on Earth in existing vacuum chambers. The heater has about the same 2800K as the filament of a light bulb and radiates almost as effectively... It loses only a fraction of the incoming light power because the Sun is even hotter - but for this comparison to hold, the thermal design must be optimized. That's the aim of my reflective-coated regenerator insulated by vacuum and of my ruminator. As well, optimum operation at Jupiter makes an imperfect heater at Earth, for instance. Either have two specialized heaters, or optimize for the more demanding location, and cut-out the excess sunlight. For Jovian missions, I found the acceleration near Earth quick enough. ---------- A nuclear thermal engine heats and expels hydrogen just like my Solar thermal engine does. The Solar has born advantages to achieve a higher Isp: - It can use just tungsten because no neutronic properties are required. Hotter hydrogen is faster. - At 2800K and only 30mbar, 23% of the injected H2 split into H, absorbing much more heat from a limited temperature. During the expansion, a good fraction of this heat converts to kinetic energy. This was not considered in ESA's design. A reactor would also try to push strongly, and the corresponding chamber pressure prevents hydrogen dissociation. The pressure is constrained by the expansion possibility. In my present design, the mean free path at the exhaust is a few time smaller than the nozzle diameter, so hydrogen behaves like a gas. Less expansion would waste heat not converted to kinetic energy, while more chamber pressure would reduce the dissociation and the isp. I had failed this estimation previously (2010) when I got isp~2200s. A "boosted" operation mode, where more hydrogen gets heated by as much sunlight, increases much the thrust and wastes little isp. It seems useful during certain operations, but at least for the trips around all equatorial Jupiter or Saturn moons, I found no advantage to it. For a capture by Mars or Mercury maybe, since one m/s is worth more near to the planet than far away. I too believe that my engine is rather easy to develop, but as an old engineer, I know well enough that a convincing system design is just the requisite before running into the worries of development.

No relationship. Information theory calls it "entropy" by analogy. And anyway, the increase of entropy applies under certain conditions.

Hey Squared2, nice to see you here!

I did not claim nor even suggest anything. Why suppose so much? Not having the knowledge to make my own opinion about it, I try to stick to a strictly neutral approach, and I hoped my question was neutral as well. I wanted to know how strong the signals were supposed to be from reasonably probable events in our vicinity, and if this strength would be detectable by the existing instruments.

The amount of uranium on Earth limits the producible electricity to much less than oil, gas or coal - sunlight and wind being limitess. Geothermal energy needs no storage. Solar thermal energy stores heat for nighttime or bad weather since years. For wind electricity, batteries would be more or less affordable and for sure small, with a Japanese univerity developing sodium batteries instead of less abundent lithium. Though, I expect other methods will replace batteries with better efficiency and at lower cost: flywheels, underwater air bags, artificial ring islands. http://www.energyharvestingjournal.com/articles/compressed-air-energy-storage-00003358.asp?sessionid=1 http://www.renewableenergyworld.com/rea/news/article/2013/01/belgium-plans-to-build-island-to-store-excess-wind-energy For my cost estimates, running fewer fossil fuel power plants at constant full power, helped by flywheels to smoothen the demand out, would already save money. http://www.scienceforums.net/topic/59338-flywheels-store-electricity-cheap-enough/

You mix the possible waves around a nucleus with the stationary ones. Only the stationary waves, the orbitals, have a well-defined energy, but an electron can have a different shape, which then evolves over time. If the electron is trapped in the atom, it is a weighed sum of orbitals. That weighed sum is a solution to Schrödinger's equation, because the equation is linear. The real difference is "stationary". A weighed sum of orbitals having different energies is not an orbital, because their exp(i2pi*E/h) lets the phases rotate at different speeds, so the sum will strengthen or weaken at places varying with time. The electron moves then, and radiates. In most atoms and molecules, the electrons are stable and fill the lowest obitals. But for instance during the absorption or emission of a photon, electrons are a mix of several orbitals, and their energy is uncertain. The 'proper' functions, or keep the badly translated 'eigen' if you wish, are the orbitals. These are not the only possible shapes of an electron around a nucleus; they are the stable ones.