Enthalpy

Radio waves used for telecomms aren't concentrated enough to be interesting - by far. It's like some kW spread over many km2. Radio beams can and do transmit power if purposely concentrated; a demonstrator was built at La Réunion. Far less efficient than wires, but sometimes you don't want wires. Photovoltaics can't work with radio waves and isn't done, because the photon energy is less than the mean temperature energy (26meV at 300K). Visible light around 2eV fits, but radio waves have 104 to 1010 times less. The proper setup is an antenna or coil coupled with a rectifier like diodes. Antennas do work a light frequency. Kraus proposed it in his book "Antennas" very long ago when the technology was completely out of reach, and few yeas ago it has been done. Diodes are still extremely bad at these frequencies so the combination is worse than photovoltaics, but antennas that concentrate light's field to smaller locations of a photovoltaic cell are claimed to have advantages. Presently, wireless power is made by magnetic fields mainly, as (1) they radiate less far hence are more acceptable (2) they show a decent efficiency (3) they are less sensitive to the surroundings (4) at least in 1989, law limited only the electric radiation. Electric field, or electromagnetic, would be possible, but to my feeling less convenient.

I don't grasp what "in floating-point notation" shall mean. There are many floating-point formats, Ieee 754 being only one of them, and I know none of them on 8 bits. Among the many possibilities: - The mantissa can be coded as 2's complement or 1's. Same for the exponent. Both conventions do exist. - The exponent can code a power of 2 or, as Ibm did long ago, a power of 16. - Some formats store the leading 1 that follows the decimal point, others don't. - The size can vay. Fps had floating numbers of 38 bits. Intel's Mmx computed on 80 bits, Pr1me on 128 bits. - Some pocket calculators and some microcontrollers had the mantissa in Bcd, the exponent as a power of 10. - The exponent can be at the beginning of the field or at the end, the signs anywhere, the bytes in reverse order.

Usb cables exist to connect two computers, I've had one, but the normal and better method is an Ethernet cable.

Hi, thanks for your interest! Yes, the Kálmán filter (and some others) is a mathematical method designed to remove noise, but it doesn't rely at all on frequency segregation. (Don't get put off by Wiki's article: signal people make everything horribly more complicated than necessary). It typically receives data from several sources, one containing mostly the desired signal and some noise, others that contain mostly the undesired noise. In a sound studio, that would be the musician's microphone, and a microphone near the climatizer. (A Kálmán filter can also remove echo, and is commonly used for that as well - not the case here). A mathematical method, fed by both data streams, identifies how the noise mixes with the signal (linearly, that's the only assumption): if expressed as a time function, how strongly for each possible delay; or as a frequency function, with what attenuation (complex or phased) the noise invades the signal for each frequency. The simplest method is a correlation. Then the filter computes how to subtract from the signal the part considered to originate from the noise source, and applies it to the signal. This is of course all digital, and is very efficient to the ear, like 40dB or even more, provided that the mixing function evolves slowly over time. This must be identified permanently, hence the filter is called "auto-adaptive". My sketch shows a tunable low-pass filter in the noise path because the noise itself is low-pass filtered by the suspension stages, so the transfer function identified by the autoadaptive filter is a low-pass. This wouldn't generally be the case; in a sound studio, the transfer function would rather be a wide-band multiple echo. With accelerometers in the ground, the measured noise mixes in a complicated way with the useful signal hence may be less good. For instance cars moving on a nearby road inject noise from varying locations, and the transfer function changes quickly, less good. Waves at a shore can be better filtred out. The advantage of accelerometers is that they fit an existing interferometer. Maybe the suspension points of the mirrors are a better location for the accelerometers. And by the way, four sensors to identify the noise direction isn't a completely standard Kálmán filter - but nearly, so the signal people shall think a bit at it. The very nice setup is with the auxiliary beam and mirrors upstream in the suspension, because this beam measures the noise precisely the same way as the main beam suffers it: same origin, orientation... and even better, the transfer function from an auxiliary mirror to a main one is extremely constant, hence can be identified with huge accuracy, which permit a very strong attenuation of noise. Here very much better than 40dB is possible. Ground noise would essentially vanish. Whether the secondary beam can be added to an existing interferometer is unclear; this may demand to rearrange the suspension, which is one extreme design in a gravitational waves detector. Maybe different detectors, not using a kilometer-long beam, can work. But for a new interferometer design, it's worth considering the scheme - even in the case that it demands small additional vacuum lines.

Mmmh, some points are clearer. I didn't get the full picture, as the scenario seems sophisticated. 2) Has L1 an important advantage over a high Moon orbit? The gravitation energy in Earth's potential is nearly the same, it's cheaper to reach from Moon's surface which should almost compensate the departure from there, and we reach a Moon orbit faster. 2 also) The one-year orbit can be synchronized with Earth, but how often is Mercury at a suitable location? If I remember properly, Mercury's orbit doesn't resonate exactly with Earth's one, and approximations get quickly unmanageable at the scale of the Solar system. I'm carefully more pleased with the one-year orbit, which should keep compatible with Mercury's orbit inclination and with Mercury's eccentricity. Raising the apohelion to the asteroid belt is the easier part with a Solar sail. But how long does it take to lower the perihelion to Mercury? Solar sails use to navigate quicker when spiralling on almost-circular orbits. 3) I have zero worry about storing cryogens. This technology is necessary for any progress in space travel, is currently being developed, and will be available - sooner than big solar sails. I describe balloon tanks of welded steel for instance there http://www.scienceforums.net/topic/60359-extruded-rocket-structure/page-2#entry761740 insulated in space by multilayer film, and hold by polymer straps in an exoskeleton like a truss. This leaks <10W for several 10t of oxygen or hydrogen. To that tank design (also useable for a few hours in an atmosphere with some foam), add a small cryocooler, this one or an other http://saposjoint.net/Forum/viewtopic.php?f=66&t=2051&start=10#p23468 powered by solar panels. Nasa also considers powering the cryocooler by a small fuel cell fed by the propellants that evaporate: nice for missions away from the Sun. So even if it's not done up to now, principle designs are easy and the desire is there, so you'll have them. 6) I still don't grasp how the return propellants are brought to Mercury (maybe your scenario isn't still detailed there?). Are they propellants for a chemical engine, for the Solar thermal engine...? Do you need 185t preset there? Do they arrive by sail, by the Solar thermal engine, how quickly...? The return leg uses to be the hardest nut. Consider aerobraking at Earth, gravitational assistance at Venus, and maybe a combined chemical/Solar push to leave Mercury, similar to http://www.scienceforums.net/topic/83289-manned-mars-mission/#entry806615 I'll put more data about sharing the effort among the chemical and Solar thermal engines there - sometime http://www.scienceforums.net/topic/76627-solar-thermal-rocket/page-2#entry807522 If optimizing every operation, including presetting the propellants or vessel efficiently, and using new propulsion, maybe one can bring a crew back from Mercury, but it's hard. 7) Staying on Mercury during night would make life easier and need less real estate operations prior to going there, but this constraints very strongly any docking, gravitational assistance, or generally any synchronized operation. What is your choice? Still building quickly a house for daytime when landing there during nighttime?

For the same reason that the drunk man searches his keyring under the streetlight: they aren't more probably there, but he sees better. We have already exobiologists (junior and senior), with their symposiums, and even peer-reviewed papers, before Mankind possesses its first bit of knowledge on the topic. Isn't that wonderful?

The ratio of the frequencies is like 105. Is there any application that could use both?

Hello dear friends! Extreme interferometers like Ligo, Virgo, Leo600, Tama300 try to detect gravitational waves http://en.wikipedia.org/wiki/Gravitational-wave_detector and ground movements are one difficulty for them. The mirrors are suspended in several stages to insulate them, sometimes actively. In addition to suspension, I suggest to measure the ground's movements by other means, and identify by how much these movements transmit into the measure at all frequencies, then subtract this contribution as estimated from the measured ground movements and the transfer function. This so-called adaptive filter is commonly used in acoustics, one method being the Kálmán filter http://en.wikipedia.org/wiki/Kalman_filter which routinely attenuates noise sources by 40dB. In a first method, triaxial accelerometers can measure the ground movements. At least three pieces on a triangle plus one at depth (earthquakes are deep) would pick the distant noise sources' direction, which influences the effect on the interferometer. A too wide basis might be less good against near sources - perhaps. Dedicated sets of sensors can pick noise made by known sources like a machine, maybe a road. Accelerometers are straightforward hence may be used already; I didn't see them mentioned after short reading. The following one is not shown on the interferometer drawings I saw and could be new. My sketch omits the second arm, the interference components, and all refinements. I propose to add auxiliary beams between mirrors hold at an earlier stage of the suspension. These would pick ground movements almost as the main beams do, easing the cancellation, but upstream the mechanical filter hence more strongly. The auxiliary beams pick gravitational waves as well, but this contribution is strongly attenuated by the transfer function that mimics the mechanical filter. Being more shaken, the auxiliary beam is built less sensitive than the main one, by using fewer bounces, a longer wavelength... Different wavelengths would help sort out both beams; consider my filter for strong stopband attenuation http://www.scienceforums.net/topic/74445-evanescent-wave-optical-filter/ a new interferometer design like Tama300 has it easier. Marc Schaefer, aka Enthalpy

Nice to see you again! Could you detail where the water and cryogens come from, to fill the departure stage and capsule at L1? Sent from Earth, or mined from the Moon and sent from there? And why electrolyse water instead of sending the separate propellants? Do I understand that the departure stage goes to the transfer orbit using its sail, the capsule with a chemical engine, and after joining both the sail brakes both at Mercury? Did you consider a single vessel that departs Earth chemically and brakes by sail at Mercury? Earth departure takes "only" asymptotic 7533m/s (circular, coplanar Hohmann...), or 5537m/s from Leo, still reasonable - not optimum, but safer as it avoids docking far from Earth. Did you consider a slingshot at Venus? Several ones permit presently to put 1t at Mercury starting an Atlas or Delta from Earth. I still haven't tried to estimate the benefit, but a single slingshot at Venus must be key to a manned mission. Delta-V and mass estimates at each stage would be nice, since this is a hard nut for Mercury. Braking duration by sail also - I understand this is a prospective scenario for which the sail does not need to exist today, and Mercury is a good place for a sail. Is the Mercury habitat brought with the crew, preset in orbit, preset on the surface, buit there from local materials...? Shall the crew stay during daytime? And: how does the crew come back? Accelerate by sail, slingshot at Venus, aerobrake at Earth? Not necessarily very heavy, but the harware must be at Mercury. Is it the same vessel as for the first leg?

Potassium doesn't disappear as it's "used up" by plants. Living plants store some and release it when dead. More: from satellites, we know Mars' surface composition only. From the depth, we know very little - the possible presence of frost, through radar mapping.

- Keep as much of the leaf blower as possible, assemble some refractory bricks, put coal, you have a forge or an iron smelter. - Aerate water basins, produce trouts. - Build a model aeroplane or boat. - Propel a pirogue. - Couple a water pump, fight floods. I suppose Acme meant: lack of electricity in your house.

The other component is moisture in the case of cyanoacrylate glue.

Hi, I have big doubts about 1600°C at the boiler. It can be a flame temperature. A decent boiler won't attain that, among others because steel wouldn't resist it. To avoid tar and soot, you could first try to obtain a complete combustion before the products reach the boiler. That is, put the boiler away from the flame (easy to try with a candle), and if needed inject air in two steps : first to regulate how much fuel burns, then to finish burning it completely.

Glues are extremely varied and so are their hardening processes. Some harden by evaporating the solvent, for instance through the thickness of glued papersheets. Others harden by a chemical reaction, including with ambient humidity.

What you begin with depends on the kind of understanding you seek, but the introductions to QM that avoid maths tend to be very misleading and much more complicated than they should. So yes, if you don't have yet the background for linear algebra and waves, I suggest to begin with them. They're already significant chunks of knowledge, are useful by themselves, and are interesting per se. Whether you should learn alone or through high school science course is a matter of taste. Acoustics doesn't apply to general QM (just to phonons) but it's a simple wave, simpler than electromagnetics. Propagation guided by a cable would be even simpler. Some "experiment kits" (websearch keywords) exist for radio, for optics and for electromagnetics, they're often excellent - I haven't seen any for acoustics nor QM. They give an insight that differs from books and is often more useable. The are an excellent basis to a future course, and they're fun.

Hi Shreyasshree, while QM is certainly fascinating, it's possible that you find it discouraging, or that your efforts are less rewarded than they deserve, in the case that you try to learn QM before having some background. Depending on how easy you're already with this background, it would be a good idea to start with it, so that your time spent on QM (later if necessary) is more profitable and enjoyable. Linear algebra (vector spaces, linear operations and all that goes with them). Fluent is needed. Waves. Fluent as well. You may start with acoustics, go on with optics. Signal processing is very helpful. Or antennas. Or possibly detailed knowledge of diffraction aspects in optics, but this uses to be less complete than signal processing. Electromagnetism, at least some, would be useful. Well, I suppose there are many different paths to learning QM. It takes years to get a somewhat clear picture of it, so you can perhaps begin with an incomplete background (...don't know what yours is) and add more elements of comprehension over time. I'd suggest not to read the introductions for the general public - the ones that want the explain using analogies. These analogies simplify nothing, are confusing and misleading. Avoid as well the philosophical approaches of duality and the like, which bring only useless complexity. Don't waste time with historic introductions, because QM was long misunderstood, including by physics heroes, so don't learn their mistakes only to un-learn them. Go straight to the proper up-to-date formulation, with the maths.

That's a good use of waste heat available at moderate temperature from the engines on ships. Faslan wanted to boil seawater at room temperature by vacuum only, and while this would work, my bet is that it's less convenient than heating, which is in turn far less good than reverse osmosis. How old is this Navy's technology: older than widespread reverse osmosis? Presently on big merchant ships, the part of the heat not transformed into work by the internal combustion engine powers a steam turbine, so the final waste heat has a low temperature, and these combined cycle engines (well over 60% efficient, wow) must coexist better with reverse osmosis.

Not helping you, but for my personal information: - Why do you add KCl? I understand the conductivity may increase, but this would be wasted current, which only moves unwanted species. Or? - What's special with Sn plated on carbon? Sn foil is available and cheap, so how does plating improve?

No six electrons available at an oxygen atom, because six electron pairs (the others coming from the bonded atoms) would not fit on favourable orbitals. For simple atoms like oxygen, molecular orbitals explain the simple idea of valence, where oxygen has the valence 2. One example is given there, I suppose simpler and more general explanations exist elsewhere: http://en.wikipedia.org/wiki/Triplet_oxygen You could also play some time with the idea that reactions use to occur between already formed molecules like O2, not between isolated atoms like O. This has many important consequences, useful to grasp.

I'm not quite sure pharmacy alcohol is made undrinkable. It's just a matter of cost: pharmacies sell it too expensive to compete against taxes on drinkable alcohol, so there's no need for tax collectors to taint it. An other reason is that being used on the skin, pharmacy alcohol should better contain no poison - and methanol is a poison, I mean, worse than ethanol.

Boiling by low pressure takes essentially the same energy as boiling by high temperature, that is, an awful lot - and in a less convenient form. Reverse osmosis is hugely better than boiling, because it separates only the salts from the water, while boiling separates the water molecules from an other, which takes much more energy since water molecules and more abundent, and is useless when one produces liquid water. In a somewhat smarter operation, heat (typically from sunlight) boils some salty water at a higher pressure, and the condensation of (salt-free) vapour releases heat that is used a second time to boil more salty water at a less high pressure, and so on one dozen times. But even with cheap Solar heat and this reuse scheme, it's more expensive than reverse osmosis. http://en.wikipedia.org/wiki/Reverse_osmosis

http://en.wikipedia.org/wiki/Cathode_ray#Description Energetic electrons strike the matter, excite electrons which emit light when de-exciting.

I've not invested time in the protection of life against ionizing radiation. I checked the protection of electronic equipment for my satellite, but the requirements differ a lot. The mission I propose, with its more efficient engines, travel in 80 days to and from Mars, which is a partial answer to the radiation worry. I've also suggested to put a narrower shield only in the direction of the rays source, to reduce the emission of secondary rays, and save mass. There: http://www.scienceforums.net/topic/80982-shield-astronauts/ The Solar thermal engine using hydrogen as a propellant, the tank can be a better shield. Anyway, engineering without numbers is nothing, and I've put no figures on that. The 80 days travel was a desire by Nasa resulting from this radiation concern. I considered opening a thread here to ask for data. If you have some information, you could put it on the forum. I suppose the topic deserves a specific thread, as it's vast.

--------------- Launcher --------------- I suggest there a flexible and hopefully cheap launcher design for the manned Mars mission http://www.scienceforums.net/topic/65217-rocket-boosters-sail-back/#entry814958 its reused "sailback" first stage fits naturally a mission needing three or five launches. I like to deploy the sunlight concentrators before leaving Earth orbit with a chemical engine. Referring to the sketch in the linked message, the launcher's previous stage can hold the Earth departure composite higher, say at its tanks; after separation, the concentrators can deploy, and if the chemical engine was over them, it can fire freely. Zenit has rolls to guide a narrow and long stage separation. Good ideas should be copied. ----- Preset equipment: combine solar and chemical propulsion ----- I had suggested that a chemical engine may save mass at planetary escape or capture for using better the Oberth effect. Here are figures. Descent to a 3390+400km Martian orbit from 59970km apoapsis (48h period) takes 1249m/s provided by the Solar engine. Capture from asymptotic 2649m/s to the eccentric Martian orbit needs 831m/s, provided by an RL10-B. Escape Earth to asymptotic 2945m/s from an eccentric orbit with 127300km apogee (48h period) takes 673m/s from one or two RL10-B. Ascent to 127300km apogee from a circular 6366+400km needs 2897m/s provided by the Solar engine. The Solar engine contributes 4146m/s at isp=12424m/s*90% (because its pushes are long), the RL10-B 1504m/s at isp=4565m/s. The same tanks and engines make the whole transfer: I take 100kg/t of propellants for them together. To preset 62t on a low Martian orbit, this scheme needs 139t on Leo instead of 159t and replaces some hydrogen by denser oxygen. The fairing's sketch at the linked launcher description supposes this improved scheme. Marc Schaefer, aka Enthalpy

A competition in Australia does it with (very purposely built) cars. These cars are rather large, very optimized (wheels as good as a bicycle, streamlining far better), and they run through sunny Australia at good speed. Extrapolating from this, I doubt a bicycle without a hull, with a smaller area, and in a more cloudy climate, would perform well. What you can do is have a battery-helped bicycle, a big solar panel at home, and charge the battery there from Sunlight instead of mains electricity. Have two batteries if you drive during the day.