Enthalpy

Senior Members
  • Content count

    3106
  • Joined

  • Last visited

Everything posted by Enthalpy

  1. Solar sails, bits and pieces

    More about the Venus flyby for the Mercury samples mission. It brings much more than I hoped. But as these computations are slippery, I may have made mistakes. Kate Davis gives an angle in relation with the asymptotic speed http://ccar.colorado.edu/imd/2015/documents/BPlaneHandout.pdf which I rearrange slightly with an escape speed at the periapsis 50m/s lost in drag need 10-10kg/m3 residual atmosphere, 0.5µm erosion about as much, and 400W/m2 a bit more. Having to atmosphere table for Venus, I made horrible scaling factors with Earth and decide the periapsis shall be at 683km over the 6052km planet's radius. The escape speed is 9825m/s there. And here's an angle-versus-speed graph for this periapsis at Venus Ariane 5eca can put 4550kg at 3475m/s above Earth's gravity, Ariane 6 hopefully too. Aimed 38° Sunwards, or outwards in an other launch window, the probe arrives at Venus with 4713m/s and 60° sunwards and forwards. Well, if Venus were in the ecliptic plane, sorry folks. The Venus flyby can give the probe 4066m/s polar speed, zero radial speed (this isn't optimized) and 2365m/s below Venus' orbital speed, so the probe's orbit is in Mercury's plane (...if Venus were in the ecliptic) and with 0.648AU semimajor axis. VenusFlybyNum.zip From there, the probe sails to Mercury's orbit, which costs roughly 10760m/s. At (mean!) 0.648AU, the sail accelerates 4550kg by 55µm/s2, so this step costs 4 years. Or a bit more, since Mercury's apsis line is not exactly in Venus' orbital plane, and so on. The rest of the mission stays the same, but with more mass. 1100kg sail leave 700kg for the bus and 2750kg as the descender starts: four times more mass than previously. The ascender has now a comfortable size, and since the electricity doesn't scale up, it brings more than 40kg samples back. Two prospectors look possible. The return path, with 1840kg, takes only 1.5 years to accelerate towards Venus. Marc Schaefer, aka Enthalpy
  2. Solar sails, bits and pieces

    My dear visionary and megalomaniac human fellows, you've probably heard about Solar sails, one attempt among many to exceed chemical rockets performance, these being inconveniently slow for hopping through our Solar system and beyond. Solar sails want to catch the light of our Sun to obtain a thrust which would indeed improve on rocket speed if the sail is big, the complete spacecraft light, and the push long enough. http://en.wikipedia.org/wiki/Solar_sail http://www.jspec.jaxa.jp/e/activity/ikaros.html http://planetary.org/ As far from the Sun as Earth is, incoming light has a pressure of 4.5µPa and reflected light as much, so accelerating any significant spacecraft mass requires sail areas at least in the square hectometre range which, to keep their own mass low enough, must be few micrometres thin - the very reasons why we still don't use Solar sails as the main propulsion of every spacecraft. Of course, I couldn't refrain from throwing a few thoughts at the engineering challenge. ===================================================================== One standard design of Solar sail has few long booms (or masts) that hold the film at its apices. The stiff parts of the sail are less long for the same film area, hence less difficult to build light. At identical boom length, a square provides the maximum area-to-length ratio, letting call the design "square sail". A pentagon loses 5% ratio, a hexagon 15%, and the drop accelerates. Though, if testing the deployment of a hectare-class sail on the ground, for which buildings limit the size, more sectors enable a bigger sail. I propose to try at a time just one sector between two booms. A continuous film can protect the payload against Sunlight, which is mandatory very near to the Sun; elsewhere we can split the film in sectors. As a wind-free building, I take a roofed soccer or rugby stadium: 100m*70m of flat lawn, where we can float or hang the booms and the film for the test. This is bigger than all Solar sails built up to 2013, and the building is still decently common. The best sector orientation on the lawn is (...with luck): Sector base parallel to lawn's diagonal for a triangular sail; Sector base parallel to lawn's length for a square, pentagon, hexagon; Sector side parallel to lawn's length for a heptagon, octagon; Sector height parallel to lawn's length for a nonagon to dodecagon and more; At some farther number, the sector's height is better parallel to the lawn's diagonal. The resulting area varies irregularly with the number of apices. 5 is a good blend. 10 is a remote optimum, with much boom length. Marc Schaefer, aka Enthalpy ===================================================================== A nice innovation on the Solar sail Ikaros is that it uses Lcd surfaces as an attitude control. That is, by making these eccentric surfaces more or less reflective, radiation pressure is controlled there, which creates a tilting moment. But Lcd have some drawbacks. They consume some electricity permanently, since the polarity must be reversed regularly to avoid wear-out. They are sensitive to sunlight, needing some protection. My proposal is to replace them on Solar sails by a thin electrochemical cell, as the one I described in EP0564012: http://www.freepatentsonline.com/EP0564012.html http://www.freepatentsonline.com/EP0564012.pdf which needs no organic material and should thus be more resistant to UV. This patent has meanwhile been granted (and should hence be available in English) and abandoned, so its technology is public and free. I never prototyped it. Making it work reversibly many times could require development. I also considered it as a thermal control surface for spacecraft. Marc Schaefer, aka Enthalpy ===================================================================== Producing 3µm polyimide film is easier than I first thought. Just take 7.5µm film and make it thinner. All right, all right, this needs further explanation. You know the machines that metallize similar films? Their big vacuum vessel encloses two huge film rolls - the source and the destination - between which the film is moved in front of an aluminium vaporizer. Pump once, metallize kilometres of film. Now, take such an existing machine, possibly a decommissioned one. Replace the vaporizing component by an etching unit - I suppose plasma etch would be fine, reasonably fast and wouldn't deteriorate the remaining 3µm thickness, as opposed to wet or gaseous etching. Adapt the pressure accordingly. And then, add thickness sensors before and after etching and build a feedback loop to control etching speed. Here you get the necessary precision that prevented thinner films from being laminated. As polyimide in this thickness range is semi-transparent to visible light, a dirt-cheap light attenuation sensor is enough. If needed, more sensors and etching units can be spread across the film's width to make the thickness uniform. You can also proceed in several steps, possibly by passing the film several times between the rolls. Add a metallic roll to stabilize the film-to-plasma generator distance if it helps. Add light shields between the plasma and the sensors, add wavelength filters, modulate the sensors' light source to protect against parasitic light. Blah blah, you already guessed all this. While this process may be too expensive for the most common uses on Earth (metallized polyester is used to wrap sweets) (and who needs 3µm film on Earth anyway) it looks really cheap for a Solar sail. Marc Schaefer, aka Enthalpy ===================================================================== An other way to make thin plastic film for the sail: Take a varnish, lacquer or similar. Pour it over a denser liquid, so the varnish floats on it and spreads. Proper amounts achieve really thin films, if the varnish takes enough time to dry. The method was used to make wing films for ultra-small model aeroplanes. Much thinner than 25µm. Polyimide varnish exists to coat high temperature transformer wires. Polyimide is dense, but some benign liquids are denser, like perfluorodecalin. To scale from 1dm2 to 1km2... Pouring and pulling continously the film to a coil as it dries can be an element of answer. Or maybe the varnish can be sprayed on an antiadhesive roll or film instead of poured on a liquid. A few crossed carbon fibres glued on the film would usefully stop the propagation of slits. I prefer the thinning machine already described, but it needs some investments. Marc Schaefer, aka Enthalpy
  3. Woodwind Materials

    Deposited metal can make corrugated walls, at a straight tube or any shape. The walls get stiffer against bending while keeping lightweight. Let's take a example tube of D=19mm, rho=10370kg/m3, E=85GPa, and e=0.2mm with the mean fibre corrugated to 1mm peak-to-peak. It weighs 2.1kg/m2 but is as stiff as if it were 0.67mm thick. Its first oval mode resonates at 7.1kHz instead of 2.6kHz for 0.45mm smooth walls twice as heavy. These walls can conduct heat oscillations over much of their thickness, in case this matters. A sandwich with a core of foam, balsa or honeycomb can't. Corrugations increase some losses, both aerothermal and by heat conduction. This is expectedly a big drawback at a flute, but an advantage for instance at The bell of clarinets, especially the bass, contralto and contrabass The bell of saxophones The entrance of the neck of saxophones The bell of adaped oboes, especially the English horn, baritone and heckelphone Marc Schaefer, aka Enthalpy
  4. Woodwind Materials

    Hello everybody! The material used for the walls of woodwind instruments, and its real, perceived, imagined or absent influence on the sound and ease of playing, has been and is the controversial matter of recurrent discussions that I gladly reopen here. The air column is the essential vibrating element of a wind instrument, the walls are not, but this is only a first analysis. The walls are commonly made of wood (sometimes cane, bamboo etc.), metal, or polymer aka plastic, which manufacturers call "resin" to look less cheap. Mixes exist too, with short reinforcement fibres or wood dust filling a thermoplastic or thermosetting resin ("Resotone" for instance). I'm confident that long graphite fibres were tried too, as fabric, mat or in filament winding. The choice results from marketing, tradition, weight and manufacturing possibilities (a tenor saxophone is too big for grenadilla parts), cost - and perhaps even acoustic qualities. ========== Plastic is a direct competitor for wood, as the possible wall thickness, manufacturing process, density, stiffness, shape possibilities, are similar. As opposed, the density of metal restricts it to thin walls made by sheet forming an assembling, but permits big parts. Manufacturers typically use plastic for cheaper instruments and grenadilla for high-end ones - some propose cheaper wood in between, possibly with an inner lining of polymer. Musicians who own a grenadilla instrument disconsider the plastic ones; I never had the opportunity to compare wood and plastic instruments otherwise identical, so I can't tell if the materials make a difference, or if grenadilla instruments are more carefully manufactured and hand-tuned, or if it's all marketing. Two polymers are commonly used: polypropylene for bassoons, and ABS for all others, including piccolos, flutes, clarinets, oboes. These are among the cheapest polymers, but 10€/kg more would make no difference. They absorb very little humidity, but some others too. More surprising, they are uncomfortable to machine: POM for instance would save much machining cost and (my gut feeling) easily pay for the more expensive material. But ABS and also PP absorb vibrations while others don't, which I believe is the basic reason for this choice. They limit the unwanted vibrations of the walls. As a polymer that dampens wall vibrations, I should like to suggest polyketone https://en.wikipedia.org/wiki/Polyketone it's known to make gears more silent than POM and PA, its glass transition is near ambient temperature, its density and Young modulus resemble ABS, it absorbs little humidity. Still not widely used, it can become very cheap. Its creep behaviour and ease of manufacturing are unknown to me, but ABS and PP aren't brilliant neither. Marc Schaefer, aka Enthalpy
  5. Solar sails, bits and pieces

    General figures about the thermal design for the Mercury samples mission. Far from Mercury but at 0.307AU (Sun-Earth distances), sunlight is 14480W/m2 strong. It heats to 300K a perpendicular second-surface mirror that absorbs a=0.03 of it and emits e=0.95 infrared from one side. Shaded areas are cold. Staying close to Mercury's noon area at 600K (700K are reported) and parallel to it, an ideal flat area absorbing infrared from both faces but no sunlight attains 505K=+232°C, a conducting sphere too. The probe's outer faces should survive >600K but can't cool the equipment when facing Mercury. A possible design puts several cooling faces at the probe body and makes a thermal contact (by a fluid or a deformation) with the coldest one at each time, when it doesn't face Mercury nor directly the Sun. At 60° incidence but emitting from a single side, a second-surface mirror reaches 300K. Averaging with Mercury's night side helps a lot, especially at the batteries. Active steering of cooling surfaces is less reliable. The probe doesn't need a general fridge cooling cycle. ---------- A thin polyimide film for the sail (arbitrary a=0.3 e=0.9 both sides) facing the Sun reaches survivable 454K=+181°C and radiates infrared to the probe's body but from a limited solid angle. Choose well the polymer deposited after the metal. Cooling the telescopic booms is difficult. ---------- The solar cells could populate sparsely a Sun-facing area. If they're transparent to the near-IR (a=0.7), cover 1/4 of the area, the rest offering a=0.03 and e=0.95, and both panel's faces emit (e=0.95), sunlight alone heats to 436K=+163°C, 600K Mercury in the back 550K=+277°C shortly. A single emitting face must be less populated. Few mm thick aluminium foil spreads the heat of small 20mm*20mm cells without heatpipes. Wide bandgap cell semiconductor is the obvious choice. The soft bond with the support conducts heat away easily but must resist the peak temperature. ---------- The surface of Mercury is still hot when the Sun sets. 200h night cool very roughly 0.2m soil whose surface gets chilly but is blasted clear by the landing engines, so insulating the prospector's bottom seems better. Deep soil probes would come warm. ---------- De-orbiting and landing on Mercury consume about 4.3km/s, taking off and navigating to the orbiter 4.0km/s. Two stages of hydrogen and oxygen shall do it. The descender starting with 700kg burns 0.94+0.14kg/s at 30bar to push 5kN in 1*D0.6m. Including 2.2g/s in the 15kW 8kg fuel cell, the Isp=4622m/s=471s lands 276kg, of which 50kg are abandoned, so the unpolluted crawler+ascender weigh 226kg. Minus the crawler with instruments but plus the samples, the ascender takes off with 100kg to meet the orbiter with 42kg only, leaving maybe 10kg for the packaged samples. Check my lightweight boxes http://www.scienceforums.net/topic/85103-mission-to-bring-back-moon-samples/?do=findComment&comment=823276 Multiple prospectors look hard. The Earth reentry capsule must stay with the orbiter. A heavier and slower mission injected to Venus flyby by the launcher would be much better. Without the descender+crawler+ascender, the return leg isn't as long. Hydrogen needs active cooling at least at the ferry-orbiter. I won't detail the easier oxygen, and as mass at the ferry and the descender is easier, I concentrate on the crawler+ascender. 7.5kg hydrogen for the ascent plus 5.0kg for mean 50W over 70 days fit in D=0.75m. Polymer belts holding the tank leak negligible heat, but from the 300K surrounding ascender, 50 plies of e=0.02 multilayer insulation leak 300mW. A cryocooler, third-Carnot efficient from 20K to 250K, uses mean 12W, rather with stronger intermittent runs and a mechanical separation at idle; its heat dump operates in Mercury's shade, when awaiting the orbiter as well. Or let the hydrogen evaporate at the crawler+ascender. 300mW evaporate 4.2kg over 70 days, so the fuel cell taking hydrogen mainly gaseous would keep the liquid cold. That's marginal with the present figures but feasible at a bigger prospector. I wouldn't burn methane in the engines and crack it for electricity. Lose 20% mass at the descender, 20% at the ascender, double the oxygen+fuel consumption for electricity, add complexity and mass. Marc Schaefer, aka Enthalpy
  6. Woodwind Fingerings

    Here's an other mechanism that responds to the closed-to-open transition in the direct holes to close some consequent holes. As opposed to the sketch on Jan 14, 2018, lateral axles carry the direct covers or rings, while the transition shafts run at the centre. This is easier at the oboe family and parents, as the fingerings I proposed on Jun 03, 2018 need only 5 transition shafts that can make concentric pairs. The sketch displays only two transition shafts acting each on two consequent covers arbitrarily spaced. Here the axles of the resultant covers are at the sides. The pairs of register keys are not displayed; articulated at the sides, they may be slightly simpler than on the Jan 14, 2018 mechanism. The rest is about as complicated, so silence, ease of adjustment, assembling and fabrication can decide. Marc Schaefer, aka Enthalpy
  7. Woodwind Fingerings

    Hello dear musicians, music lovers and everyone! I'd like to describe fingerings for music instruments with tone holes (which almost means woodwinds) and the associated mechanics. My goals for these fingerings are: Open all holes below the height-defining one, at least on the two first registers; Have no difficult key nor sequence of notes; Not need to close a hole and open an other simultaneously, at least on the two first registers. That's a difficulty of the flute; Need few tone holes regularly spaced and reasonable mechanics; But I don't primarily address the ease or possibility to disassemble the instrument. 1) and 4) make the sound quality more even and let build an instrument with better intonation. To achieve that, my very own personal proposal (... other people have proposed so many!) is: Give one half-tone to the index, middle finger and ring finger of each hand, to cover the upper part of all registers; Continue lower by approximately 4 half-tones with the little fingers. Each has the full set of keys like on the Boehm clarinet; Continue even lower by approximately 5 half-tones with the thumbs. Each has the full set of keys too; Trills near a register limit are made by the little fingers or thumbs, so the registers must overlap. No extra tone hole. Have register keys at the thumbs. Preferably, each thumb has the full set of register keys. The third register and above can't be common to all instruments: an additional register key suffices for some, others need cross fingerings, still others have extra tone holes. One finger for each of the highest six holes make cross fingerings more flexible. Expect differences among the instruments at the two first registers too. The thumbs, being agile in two directions, are the best fingers to operate several keys - bassoon players can confirm. The full set of keys at right and left little fingers is very convenient on the Boehm clarinet, where musicians alternate the notes among the hands. I propose to generalize it to the thumbs, both for lower notes and register keys. Drawings to come should make it clearer. They take me a little time. Marc Schaefer, aka Enthalpy
  8. Solar sails, bits and pieces

    More speeds and delays for the Mercury samples mission. Still not quite accurate. A cheaper launcher like Vega-C can put the probe on a 400km Earth orbit (or higher for the drag), preferibly polar 6h-18h. The sail then adds 7675m/s in spiral to escape in some lengthy 7 years. But if a mid-heavy launcher injects the probe in Venus transfer, the mission saves time. I have still no firm data about a Venus slingshot, so I take arbitrary 1.5km/s backwards from Venus' speed. The resulting trajectory is elliptic (but Mercury's orbit is too) with 0.66AU mean radius, from where the sail brakes to mean 0.39AU in only 1.8 year. The flyby can even more usefully tilt the orbit to Mercury's plane. This estimate in inaccurate, but 4 years saved on each leg is a lot - or the mission can be heavier and land on more sites. I had computed an elliptic capture at Mercury, but the probe will rather spiral down. Twice the Delta-V but for 2/3 of the time, same duration hence. A 1100kg D=203m sail isn't agile (2*106kg*m2), even at Mercury (30.4µPa incoming pressure). Two 100m2 on-off control surfaces at 45° provide 0.2N*m. The peak angular acceleration is 100nrad/s2, so a sine oscillation of peak pi/4 takes a period of 5h (and 32h at Earth). Compare with 2h orbit around Mercury: the sail can only rotate regularly around itself, and the controls steer slowly this rotation or drift the orbital plane to follow the Sun's direction. On a 6h/18h orbit, the sail can stay at 45° to sunlight. Or the sail can rotate by 180° per equatorial orbit to push flat away from the Sun at one point and show its profile at the opposite point. Consequently, don't expect the sail to cast shadow on the bus. The Sun's tidal force is strong on Mercury orbit and might let a sail's adequate orbital plane rotate to catch the prospector rising back from the surface. Or not. I didn't check. From a Venus slingshot, the probe would reenter Earth's atmosphere at 11.5km/s while a spiral transfer without slingshot (+4 years) lets brake the probe to 7.9km/s around Earth (+7 years). The lighter heat shield doesn't justify it to my eyes. Marc Schaefer, aka Enthalpy
  9. Woodwind Fingerings

    In the automatic cross-fingering clarinet system I proposed here on Jan 07, 2018, opening the left index cover is already a closed-to-open transition: with an implicit direct hole just above, always closed. This transition does open consequent holes for the 5+3 and 9+5 modes. Some fingerings in the upper first 12th open the left index cover, on Jan 07 as on May 10. This would open the two highest consequent covers, contrary to both sketches, and emit the wrong note. In one possible correction, an added register button closes only the two highest consequent covers and serves at the low end of the upper first 12th. This button must be accessible together with the low F/C button. Marc Schaefer, aka Enthalpy
  10. Solar sails, bits and pieces

    Bringing samples back from Mercury looks feasible with the sizes and masses described here on Aug 25, 2013 and followings. A sail of 10 sectors and 3.25hm2 tilted by 45° to the Sun's direction pushes 105mN at 1AU (Sun-Earth distance). Weighing 1100kg plus 1300kg for the bus and the science, it accelerates by 44µm/s2 here. Starting just escaped from Earth, with 29.8km/s speed around the Sun, it takes 5.5 years to spiral in the ecliptic plane to 0.387AU, the mean Sun-Mercury distance. Mercury's orbit is tilted by 7° so its 47.4km/s have a 5.8km/s polar component. Combining this quadratically with half of the 17.6km/s spiral delta-V result in 19.3km/s need, or 10% more, lengthening the travel to 6.0 years. Mercury's elliptic orbit needs little performance more. The return leg takes as long. The launcher injecting the craft towards Venus for a braking slingshot there would save much time, with the sail operating only near the Sun. Same for the return path. I won't detail this option now; later maybe perhaps, or not. Capture by Mercury and orbit lowering is trivial. A low orbit with 4km/s escape and 2830m/s orbital speeds takes 1170m/s to join. 290µm/s2 at 0.387AU acting 1/3 of the time achieve it in 138 days. There, a 900kg prospector (or several smaller ones if possible) separates and lands on the night side. It gets electricity from liquid oxygen, hydrogen and fuel cells. 100W for 50 days (less than 88 days, one local night) at 50% power efficiency consume 64kg propellants. 100W shall feed the experiments and sampling activities, transmissions and housekeeping, and is enough to keep the probe lukewarm. The prospector uses also oxygen and hydrogen to descend to the surface and to climb to the orbit, all from the same superinsulated balloon tanks described elsewhere. Details later maybe, or not. Mercury rotates by 1 turn in 58.6 days versus the distant stars, so in 50 days it turns by 180-26.4°. The prospector can't regain the same orbital plane unless we restrict the landing site to the equator. Though, the orbiting sail can change its plane meanwhile: turning 2830m/s by 26.4° costs 1305m/s which, at 470µm/s2 (900kg less) acting 1/3 of the time, is achieved in 96 days. The prospector shall wait in orbit before descending or after climbing. Raising the apoapsis for the manoeuvre and lowering it afterwards may speed it up. More orbit changes permit several landing sites at different longitudes. After the symmetric return leg, a capsule brings the samples to Earth's surface. Marc Schaefer, aka Enthalpy
  11. Woodwind Fingerings

    The system of May 14, 2018 for the oboe and similar has two direct and two consequent holes at some positions, too much for saxophones or tárogatók, for oboes probably too. So here's an automatic cross-fingering system where the direct and consequent holes don't overlap. The diagrams now represent both consequent holes per position, and the colour of a consequent hole tells how far it is from the closed-to-open transition of the direct holes that enables to open it: Purple for a consequent hole 9 positions higher than an open direct hole that follows a closed one. The pressure nodes are 3 and 5 quarterwaves from the reed away, including the corrections for a conical bore. Yellow for 7 positions, 2 and 3 quarterwaves. Green for 5 positions, 3 and 4 quartewaves. Turquoise for 4 positions, 4 and 5 quarterwaves. Now we see that the green holes, stopping at Eb, leave room for purple holes that open a precious second consequent hole at the four highest notes. The highest G position is but higher than the saxophone's F# palm key and fits well within the oboe's body. The turquoise holes, stopping at D, leave room for yellow holes that stabilize the high notes of the third register. Purple and yellow holes serve for one note each and can adjust the intonation and emission. Some green and turquoise holes emit also the higher first register; two notes for one hole is easier than on most existing woodwinds. Most closed-to-open transitions act on 3 or 4 consequent holes now, so one shaft soldered with each consequent hole is unreasonable. Better one shaft per transition position, and contacts that let each shaft close the proper consequent holes. The 5 shafts can make concentric pairs. Register buttons close consequent covers too. This combines with the closed-to-open transitions at the direct covers. Mode 5 closes the yellow and green covers. Mode 4 closes the purple, yellow and turquoise covers. Mode 3 closes the purple, green and turquoise. Mode 2 closes all consequent covers (but opens one or two register holes). The upper mode 1, for B, C, C# and trill D, close the purple, yellow and the highest turquoise cover. The new fingerings open four adjacent holes there, excellent for the oboe. The lower mode 1 closes all consequent covers and register holes. The register buttons move register covers too. There can be two for the long mode 2. As I prefer to double all register buttons for the right and left thumbs, automatic register covers for mode 2 aren't important. Each register button acts on consequent covers in both columns. It does need some hardware. Each direct cover can close two consequent covers and open two more, so spring force should be well tuned, more so on instruments with big holes. Each register button can move three consequent covers. ========== Now the modes don't overlap any more, so extra keys make the trills (in red here under). Modes 5, 4 and 3 extend two semitones lower for the trills. Trill holes, not related with the transition mecanism and possibly moved by the pinkies, replace the missing consequent holes. Working for 2 or 3 adjacent semitones, they can destroy perfectly the unwanted modes, but can't contribute much to the wave reflection nor the intonation. Rather holes too narrow and too high giving imperfect brightness and intonation. Sounding a semitone lower is an option. Experiments shall decide. On obvious position is where the consequent holes end, to prolong the modes 5, 4 and 3 with the same key. A second one should reside where the purple holes end, to stabilize the mode 5. Mode 2 extends one tone lower easily and mode one a semitone higher naturally. A-B in the upper mode 1 neds a trill key, maybe the lower key for modes 5, 4 and 3 if it's not too dull, or a different one, or several holes. The upper mode 1 uses alternate fingerings for the trills, which would open only 2 or 3 adjacent holes, but using a lower trill key helps there. The register holes must work meanwhile but not the consequent covers. This may need additional register buttons, which can also open the trill keys. ========== The trill key(s) that serve to stabilize extended modes apply also to the clarinet system described on Jan 07, 2018. I believe the automatic cross-fingering system here does not apply to the flute, because it uses plethoric tone holes that increase the losses. Check instead my system of Jul 02, 2017 and following http://www.scienceforums.net/topic/107427-woodwind-fingerings/?do=findComment&comment=999590 Modes 1 to 5 do not suffice for the bassoon's range. It would need more columns of consequent holes, which get really complicated. With two holes per position now, the system may fit a saxophone including the tubax, a tárogató probably. Lower instruments have a wider range, so the English horn and baritone oboe would benefit from automatic cross-fingerings even better than a soprano oboe. Same for the sarrusophones and rothphones. Marc Schaefer, aka Enthalpy
  12. Solar sails, bits and pieces

    2010 TK7 is an Earth's Trojan, the first discovered and presently only known one https://en.wikipedia.org/wiki/2010_TK7 http://communications.uwo.ca/trojanasteroid/downloads/pdfs/NatureLetterFinal3-preprint.pdf orbiting the Sun in 1 year, 60° before Earth - but with 20.89° inclined orbit and with 0.809AU perihelion, 1.190AU aphelion (AU = Sun-Earth-distance ~149.6Gm). A visit should bring interesting science, for instance to compare its composition with Earth. Alas, the inclined orbit is costly to reach. Wiki cites 9.4km/s from Earth's orbit to our Trojan's one; this depends on the script. Just tilting an elliptic 0.809/1.190AU orbit would cost 9.7km/s, ouch. Chemical propulsion in a direct shot would divide the mass by roughly exp(3)=20 when arrived there, bad idea. Combining with Earth's escape as Oberth effect makes no miracle. Jupiter can tilt the orbit as it did for Ulysses, but going there costs time and 5.6km/s if not provided by Venus and Earth, braking at our Trojan too. I won't check if Earth and Venus flybys provide the inclination better than Jupiter does. The sunheat engine and its 12.4km/s ejection speed would divide the mass by less than 3 at destination, less bad. ---------- With the size and booms described in this thread on Aug 25, 2013 and Mar 15, 2015, a solar sail tested on Earth brings a probe there in a decade, takes samples back, with no lost mass. We're getting somewhere. Having 10 sectors tested individually on a rugby pitch, the sail is 3.25hm2 big, and at 1AU and 45° to the light's direction, it pushes 105mN outwards and perpendicularly. The sail with booms, film and shrouds weighs 1100kg estimated as previously, the bus and science are granted 900kg, so the transverse acceleration is 52µm/s2 at 1AU. Some unspecified launcher shall put the 2t above Earth's gravity; polar speed by Oberth effect would save delays. Tilting the orbit can be done only around the apsis of the destination, so it takes twice as long: not 9500m/s by 52µm/s2 but 11.6 years at 1AU. This goes faster if nearer to the Sun. Orbital speeds increase as R-0.5 but the sunlight's pressure hence acceleration as R-2. Spiralling for 2 years, the craft can be at 0.763AU, where tilting takes 7.7years. The dumb sum would be the same, but as the sail tilts and lowers or raises the orbit at the same time, the optimized combination saves maybe 2 years for 10 years to our Trojan, less with the launcher's help. ---------- At 2010 TK7, the probe makes pictures, remote analyses, and takes samples. Rather a small craft separated from the sail, probably the same the re-enters Earth's atmosphere. A hollow tethered harpoon pulls samples from many locations to the not landing craft? Someone else shall think at it. The Earthlings' sail is as big as the target body. Delicately megalomaniac, isn't it? ---------- The return trip is easier because the capsule with the samples aerobrakes in Earth's atmosphere, so the transfer orbit can remain tilted. Raising the perihelion to about 1AU to slow the craft down to cross Earth after about 1 year would cost only 1.5km/s around the aphelion in an operation lasting 1.3 year, so the aphelion would be lowered a bit too. The apsis line outside the ecliptic plane is more complicated to imagine but costs as little. The return leg fits in 2 to 3 years. The cost to the elliptic orbit is small and adds quadratically to the tilting cost, that's why I neglected it in the leg to our Trojan. The capsule brakes from 15km/s in the atmosphere and lands with parachutes. Only the capsule limits the samples' mass. Check my lightweight boxes http://www.scienceforums.net/topic/85103-mission-to-bring-back-moon-samples/?do=findComment&comment=823276 Marc Schaefer, aka Enthalpy
  13. One sensible candidate criterion to determine if a material is prone to galling is if heat increases its coefficient of friction. This increase would let the temperature and friction power diverge locally if the pressure and speed suffice. Or if heat increases the friction too steeply, possibly in comparison with the heat capacity. And the increase may apply to the already hot material. I have no data about this, which is the main difference with the previous rejected criteria. Marc Schaefer, aka Enthalpy
  14. Woodwind Fingerings

    The flute with Boehm system uses the ring finger to play the F# so two adjacent holes vent it. This makes E-F# and F-F# slurs more difficult and nearly precludes trills with standard fingerings. The alternate fingerings open a single hole at the main transition, making a dull and flat note. I propose here to add one button for all these F# trills. The idea is immediate enough that it may well exist already. In the usual construction, any of the three next lower covers close the "F#" cover (which emits G when open), whose shaft runs within the tubes of all three keys, with three transmissions to the shaft. The added button acts on the shaft to close the G emitting cover and is pressed by the right ring finger, so two holes are open below the transition, and even a third one when playing F#, which changes about nothing. The best position for the new button is already taken by an other trill key. I've drawn them next to an other, but the new button can also reside close to the little finger or beyond the "D" cover (which emits E when open). The construction is obvious and improves 5 trills. Good workshops can add it to existing instuments. ---------- Optionally, the new button can close an articulated G# cover too for easy and clean F#-G# trills. The present alternate fingering makes G# dull and flat by opening a single hole at the main transition. Modern saxophones close the G# cover by the "F#" cover (which emits G when open), some clarinets too, but the Boehm flute can't because notes in the third octave need the open G# while some lower covers are closed. The new button would the close the articulated G# in addition to the "F#" cover for easy trills. Then, the new key must differ from the "F#" key, with a transmission between them. That way, the three covers that close the "F#" cover don't close the G# cover, and the third octave functions normally. The transmission to the G# cover is not sketched. ---------- The complete solution to trills and all fingerings is the one I described on Jul 02 and Aug 06, 2017 http://www.scienceforums.net/topic/107427-woodwind-fingerings/?do=findComment&comment=999590 http://www.scienceforums.net/topic/107427-woodwind-fingerings/?do=findComment&comment=1005747 but here the added button keeps the usual fingerings and exact set of holes, avoiding to relearn and redesign the instrument. Marc Schaefer, aka Enthalpy
  15. Molecule Diffraction Setup

    Hello you all! Experiments are built to observe the wave nature of ever heavier objects. It was done around 1999 with C60 fullerene at the Vienna Center for Quantum Science and Technology, short description there www.univie.ac.at/qfp/research/matterwave/c60/ from which this sketch is adapted: I resembles what one expects from a diffraction setup, but the wavelength differs from optics, hence so do the distances, grating's period, fringes separation. The light beam is strong and concentrated to ionize the molecules on its path, and a detector senses the charges, around 1 to 100 per second. The description doesn't detail all subtleties. Science has progressed meanwhile, as interferences were obtained with heavier objects like proteins, but the experiment with fullerenes remains admirable. ==================== Maybe some improvements can be brought to similar experiments ? At least on the sketch, the oven resembles a barrel with a hole. A true and good nozzle would expand and cool the fullerene better, to obtain a narrower velocity distribution. Authentic De Laval, at least down to a pressure where the mean free path is smaller than the divergent. The narrow throat may need special fabrication. Seek a high pressure ratio, by a big oven pressure if needed. Try optionally to mimic the gas temperature at the nozzle's walls. Heat the fullerene after it sublimates, before the expansion. This shall limit its condensation during the expansion. Add a gas to the fullerene in the oven to make the expansion more efficient? Argon, methane… Problem: I don't know how to remove the gas from the beam. Maybe the detector can discriminate the fullerene from the gas? Add mechanical choppers on the path, especially near the collimation slits, to keep only the fullerene molecules with nearly the mean velocity. You lose some beam intensity but improve the diffraction pattern. Use a mechanical speed to impart the 200m/s or more. Up to 500m/s are easily accessible to a rotating disk of metal, more with carbon fibres. Heat the fullerene very little, just enough for slow sublimation at the rotating part. The emission is more in the plane, so less heat achieves the same beam intensity, and the speed is more uniform. Use microphones as detectors. The kinetic energy is 6kT at 300K, so cold microphones are better. With a piezoelectric or piezoresistive material, with micromachined silicon or with electrets, you can cover an area with microphones, so the experiment is faster than by scanning the diffraction pattern area. I feel microphones easier than the power laser too. Marc Schaefer, aka Enthalpy
  16. Molecule Diffraction Setup

    Nozzles are long known as sources of molecular beams, and moving sources too are known. As one example, the 1969 PhD thesis by Les Sterling Sheffield: https://oaktrust.library.tamu.edu/handle/1969.1/154986 The noise was around kT, but distributed mainly around the resonance frequency, leaving less noise in the useful band. Typical dimensions then were squares like 100µm wide, and reducing to 2µm would be easy now, at least for the lithography. The 10mm height would be covered by several (many) microphones probably.
  17. Woodwind Fingerings

    On Oct 02, 2017 I drew for the third G# the only fingering that works on my horrible flute. Normal instruments use that one: which is less stable than G and A for the reasons already explained.
  18. Woodwind Fingerings

    The system of May 05, 2018 for oboe and similar can have more consequent holes to ease the emission of the highest notes by cumulating the modes 5, 4 and now 3. Some actions by the register buttons must be split: when playing the upper low register, the closed-to-open transition can open a consequent hole a major third higher (5/4), but the consequent holes a sixth higher (5/3) are opened only to play the highest register. To reach a written high D, the system needs a consequent hole corresponding to a G. This is but higher than a saxophone's F# palm key and fits on an oboe's body. Where the direct and consequent holes overlap, the body is badly overcrowded. Some sort of sketch may come - hopefully. Marc Schaefer, aka Enthalpy
  19. Woodwind Fingerings

    The bocal can have register holes at the English horn, the baritone oboe, the bassoon, and similar. Just as an illustration: Only the bassoon has a register hole presently, and very close to the joint. Holes closer to the reed help emit the highest notes.
  20. Such reasoning is a misunderstanding and misuse of the theory of evolution. Let's apply the same wrong reasoning to other decisive advantages: If intelligence existed, it would be a huge advantage to humans and animals, so the evolution would have generalized it. Wrong reasoning. If toolmaking existed, it would be a huge advantage to humans and animals, so the evolution would have generalized it. Wrong reasoning. If flying existed, it would be a huge advantage to humans and animals, so the evolution would have generalized it. Wrong reasoning. The same reasoning is wrong about mind reading.
  21. Woodwind Fingerings

    At the top of the oboe's first mode, four open adjacent consequent holes are better than two as suggested on May 05, 2018. It can be done as well with the clarinet's keyworks proposed on Jan 07, 2018. It's less necessary on the clarinet, as two of its wider tone holes vent the first register rather well. It complicates the fingerings of more notes, and makes more trills approximative. Two open holes would be made wider than four, and maybe put higher. This influences the intonation and stability of the modes 3+5 and 5+9, important decision criteria. Marc Schaefer, aka Enthalpy
  22. I'm happy to see that you agree with me: selective pressure doesn't necessarily suppress a mutation that is a huge drawback. Nor does it generalize one that looks like a huge advantage. So be wary of misinterpretations of genetics and evolution. They don't make good reasoning help. Many people understand the selective pressure as a way to keep within the theory of evolution a sense of perfection that belonged to a Creation. That's a mistake. The individuals, the species, the biosphere are not perfect nor optimized.
  23. Woodwind Fingerings

    You're absolutely welcome! Fingering charts aren't easy to read. What I find difficult is to imagine whether one fingering system is better than an other. When having an actual instrument in the hands, one can make an opinion after trying for some time, but even then, putting aside the habits takes an effort: "Of course the usual system is convenient, you just need to train it enough". The Obukhov notation here makes the charts much clearer but is unusual. A note written with an X is a semitone higher. They correspond to the piano's black keys. I used to play the violin, the piano, the saxophone, the flute, the contrabass tuba and the bassoon but stopped all when I moved to a hotel in Munich. I will play the winds again some time.
  24. Woodwind Fingerings

    Here are automatic cross-fingerings for octave-overblowing woodwinds: They seem good for the oboe family and sarrusophones, rothphones; Interesting for saxophones and tárogatók, especially with wide natural range like the tubax; But insufficient as is for the bassoons and the flutes, sorry folks. The keyworks and transmissions resemble much the one I proposed for the clarinet http://www.scienceforums.net/topic/107427-woodwind-fingerings/?do=findComment&comment=1032187 and next so since a drawing of the keys can come here later and maybe, the reader could refer there instead. As for the clarinet: The instrument has "direct holes" controlled by the hands, and "consequent holes"; A mechanism detects the position of the closed-to-open transition at the direct holes; The direct holes can reside alternately at right and left to simplify the mechanism; The closed-to-open transition(s) and some register keys control the open consequent hole(s) if any; Each position along the tube can host several consequent holes to simplify the mechanism. The octave-overblowing instruments have fewer covers than the clarinet and other intervals between the transitions and the open consequent holes: their cross-fingerings can reinforce the modes 3+4 or 4+5 for instance. Here's an example of fingerings: The direct holes are drawn blue when closed. The hands may be elsewhere. The consequent holes are drawn green when closed. In this example: The second and third modes result from register holes only, as on the oboe; The mode 3+4 opens one consequent hole at a fourth over the first open direct hole; The mode 4+5 does it at a major third; At the top of the first mode, a register key combination opens the consequent holes at both a fourth and a major third over the transition. Two adjacent open consequent holes shall suffice for trills and swift sequences. At normal pace, the musician closes one extra direct cover to open two adjacent consequent holes more for intonation and timbre. All modes can extend by one or two semitones for trills. Like the Boehm clarinet does at the pinkies, I'd duplicate at both thumbs the four or more register buttons and the buttons for the lowest notes. Each register hole controls 7 or 6 semitones plus trills. Provide something to carry the instrument at the palms. A single consequent hole open is little for the oboe and insufficient for the flute, the bassoon, probably the soprito http://www.scienceforums.net/topic/107427-woodwind-fingerings/?do=findComment&comment=1020912 and next More consequent holes could help the modes 2+3, 5+6, 4+5+6, 5+6+8... but not simplify the keys. Assembling isn't easy. I'd prefer transmissions to the register holes and to the low covers, and locate on the same joint the consequent holes and the direct holes that control them. Marc Schaefer, aka Enthalpy
  25. Woodwind Fingerings

    At last message's bassoon system, it may well be better to swap the phalanges' roles: Use the distal phalanges (finger tips) the open the higher tone holes, and use the proximal or middle phalanges to close the lower tone holes. The upper register, whose fingerings need more movements, uses then mostly the finger tips, which are a bit more agile. The keys become simpler too. At one hand or the other, the distal and proximal buttons must cross an other; this is easier at the boot, where the tenor and bass branches are never separated. ---------- The "alternate fingerings" in the previous diagram show extreme cases. So many lone open holes aren't needed usually. The right index catches two buttons for several notes. I wouldn't put an extra button for that, but experience decides. The front fingers don't jump between buttons in the system I propose, huge advantage. ---------- Hi DrP, thanks for your interest! I come back soon. Marc Schaefer, aka Enthalpy