Enthalpy

Accelerating nearer to the Sun than Earth is would be more efficient, but if a probe must first brake for that, it gains knowingly nothing. So what if Jupiter sends the probe back to 0.3AU where it accelerates towards the terminal shock? Alas, the flyby must reduce the eastward speed and lose energy. The leg towards the Sun takes time as well. And the net result is: better than shooting from Earth directly, but not quite as efficient as leaving just by the slingshot at Jupiter. TerminationShockJupiterSun.zip Having to operate at 0.3AU in addition to 90AU, the probe becomes much harder to design. It also needs a cryocooler for the hydrogen that makes the second kick, while the simple Jupiter slingshot may conditionally live without. Are there advantages? The same launch can send an other probe in the opposite direction, after Jupiter puts it on a retrograde orbit. Nice, but it takes about 3 years more, and if waiting 5.4 years, a simple slingshot at Jupiter can target the opposite direction too. The deflection by the Sun can vary more, by adjusting the perihelion or by pushing earlier or later. My spreadsheet pushes early. Better: Jupiter can send the probe out of the ecliptic plane, up to polar solar orbits, so the probes can reach the terminal shock in any direction. My spreadsheet computes only prograde and retrograde orbits, but the tilted performance is in between. As the Sun's movement apex is far from the ecliptic plane, reaching this direction may justify the extra engineering and waiting. Saturn seems to achieve retrograde orbits better than Jupiter does, but the legs to it and back take longer. Flybys at Venus, Venus, Earth before Jupiter may save propellant and achieve better angles. I checked none. Marc Schaefer, aka Enthalpy

Of the huge speed needed to reach the Sun's termination shock at 90AU in bearable time, a slingshot at Jupiter can give 5 to 6km/s for free TerminationShockJupiterSlingshot.zip so it's time to update the suggested mission of Jul 07, 2013 http://www.scienceforums.net/topic/76627-solar-thermal-rocket/?do=findComment&comment=755396 including as well the improved script for Earth escape of Jul 27, 2014 http://www.scienceforums.net/topic/76627-solar-thermal-rocket/?do=findComment&comment=818683 The future Vega-C puts 3.1t at naturally inclined 400km Leo. Saved 50M$ over Ariane. Sunheat engines raise the apogee to 127Mm radius in less than a year, tilt as needed, end with 2391kg. An O2+H2 engine kicks at perigee to send 1888kg at escaped 4233m/s. The optimum is broad, and more speed saves volume under the fairing. 50kg of chemical engine and oxygen tank are dropped. 1838kg remain. Sunheat engines add 5km/s for 9233m/s. End with 1229kg. 300kg of hydrogen tank and sunheat engines are dropped. 1538kg remain. Sunheat engines add 8367m/s for 17600m/s versus Earth. End with 784kg. Jupiter reached in 0.8 years brings the asymptotic speed to 35km/s versus the Sun. The probe reaches 90AU in 13 years after Earth escape. The remaining 6 D=2.8m engines eject the 754kg in 17 days. They weigh 70kg and the remaining tank 140kg, leaving 574kg for the bus and the science. That's half more than previously with a cheaper launcher - or send 6* more than Vega-C with Ariane. Several smaller probes could observe the turbulence of the medium, sense it by radio transmissions, explore different directions... Jupiter can spread the probes, including out of the ecliptic plane. The probes can also leave Earth's vicinity at different dates. The concentrators can serve as antennas. Each can also collect 1W sunlight at 90AU. If relying on propoer orientation, this is more than enough heat and electricity for a probe that makes a measure and transmission per week, but is little for a parallax measurement probe. Spin stabilisation is an interesting option. Such a mission is the perfect opportunity to test the Pioneer anomaly http://www.scienceforums.net/topic/79814-pioneer-anomaly-still/ Marc Schaefer, aka Enthalpy

Here's a sketch of the Saturn flyby to join 2015 BZ509. Probes use to overfly planets forwards to get speed, but this script overflies backwards to obtain the retrograde speed. This loses speed, so the propulsion must provide more, in amounts compatible with the sunheat engine. Phi is as in the spreadsheet, Psi is the deflection as in Kate Davis' article http://ccar.colorado.edu/imd/2015/documents/BPlaneHandout.pdf The figures are one example from the spreadsheet, where the probe leaves Saturn with no sunward speed for a cheaper but lengthy strict Hohmann transfer to 2015 BZ509. Other cases can be more realistic, other choices better. Saturn has advantages over Jupiter: The probe arrives with less Eastward speed in the Sun's frame, that's more Westward speed in the planet's frame. Saturn is slower, so the probe loses less speed. The probe gains speed when falling from Saturn to BZ509. Saturn isn't synchronous with BZ509. The launch date and speed adjustments let the probe meet the asteroid, while arriving on time isn't easy with Jupiter. But Saturn moves too slowly to let pick a position, so the probe will improbably arrive at a nodal point of the asteroid's orbit. The correction may demand additional speed which the spreadsheet doesn't include. Combining the correction with the tilt kick or the arrival kick linders the cost. Mass estimates may come some day. Marc Schaefer, aka Enthalpy

The asteroid 2015 BZ509 is on a Sun orbit as big as Jupiter but retrograde, elliptic and titled https://en.wikipedia.org/wiki/(514107)_2015_BZ509 A recent study suggests that the asteroid is of extrasolar origin, the only matter known in our solar system. So shall we bring samples back from 2015 BZ509? With a reverse orbital speed around 13km/s, the task seems impossible, but the sunheat engine and a flyby at Saturn would enable it, according to my estimates. A flyby at Jupiter instead lets difficulties arise, but I didn't try hard enough: reach BZ509's orbit, synchronize with the asteroid, wait for favourable positions... A solar sail doesn't look good: at one Sun-Mercury distance it takes 18 years to tilt its orbit by 163°, and at one Sun-Jupiter distance it's not autonomous. The probe leaves Earth much faster than for a Hohmann transfer, so it arrives at Saturn in only 2.3 years with much speed in a direction mainly outwards, and passes before and above Saturn which deflects it in a reverse orbit in the same plane (tilt 180°). The minimum global speed cost puts the probe in a Hohmann transfer from Saturn to BZ509, but other options would save time. At mid-transfer, the probe corrects the orbital plane by up to 17°, which is costly, and near the asteroid it makes the final push to accompany it. The Earth-to-Saturn leg is much exaggerated in the sketch: displayed too straight, with the Earth at the wrong place. Reversing the path to come back would need a doubtful combination of positions and cost much speed, so the probe shall head to Earth directly and aerobrake despite the reverse direction. That's about 68km/s, just above the present record, wow. The path is in BZ509's orbital plane, and braking more than Hohmann needs shall let the trajectories cut an other. BZ509overSaturn.zip The spreadsheet contains my estimates. A few uncertainties remain: I computed for Saturn at perihelion or aphelion only, but this makes little difference and the flyby copes with various angles, so intermediate cases should be fine; and I computed for BZ509 at perihelion or aphelion only, but we can't wait until Saturn is at the proper place, and for BZ509 I'm not sure that the intermediate cases are as favourable as the extreme ones. More details and explanations may come some day. Marc Schaefer, aka Enthalpy

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

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

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

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

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

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.

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

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.

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

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.

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

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

I suggested on Jan 01, 2018 to produce instrument parts by metal deposition, electroless or electrolytically. Bocals (or necks) are candidates. For saxophones and low clarinets, and even more for double reed instruments like the oboe family and the basson, which are very narrow. Skilled sheet forming takes long and accuracy is a worry. Metal deposition would make accurate parts with little human monitoring. Bows for bassons, low clarinets, saxophones... are other candidates. Their complex curvature takes long to achieve from a metal sheet. Metal can be deposited on complicated patterns often series-produced by casting and destroyed after the deposition. Materials for patterns include fusible metals like lead, and also insulators like wax. Deposited metals include Ni, Cu, Co, Sn, Zn and some of their alloys, and also Ag which is praised for wind instruments. Marc Schaefer, aka Enthalpy

The pads that make tone hole covers airtight use archaic materials: leather, felt, cardboard, wax... Attempts with hi-tech stuff have consistently failed up to now, for excellent physical reasons. Register keys would be better candidates. Their small size accepts a less accurate adjustment, their stronger contact pressure and humidity favour synthetic elastomers over traditional materials. For instance at the saxophone, the pad hardens quickly at the upper register key, which then rebounds. Elastomer formulations are countless even before combining them. Perfluoroelastomers, for instance DuPont's Viton, don't rebound and resist water perfectly. Silicone rubbers rebound slightly and are less resistent. All polymers with little rebound creep over time, as far as I know and as logic tells, alas. I expect that the pads must be hard and not too thick, so adjusting their orientation must still be necessary. Marc Schaefer, aka Enthalpy

Here' a bassoon system evolved from Oct 22, 2017. It keeps two keys for each front finger acting at different phalanges, and one key per half-tone, but spreads the hands' action according to the bassoon's joints: The left thumb opens three or more high side holes at the wing joint; The left front fingers' proximal or middle phalanges open four side holes at the wing joint; The right front fingers' proximal or middle phalanges open four side holes at the boot; The right fingers', including the thumb's, distal phalanges close five side holes at the boot; The left front fingers' distal phalanges close four side holes at the long joint; The left thumb closes two side holes at the bell. The boot is one hole longer than usual, both wings are correspondingly shorter, and the bell with optional two covers can ease the transport. Movements pass only to the bell cover(s), and maybe to the register key(s) if the right thumb moves them. This improves a lot over my previous attempt. The keys are quite simpler than for a Heckel system and hopefully more silent. The resulting fingerings seem easier now. Cross-fingerings still let move many fingers, but the actions for individual notes are healthier. A bassoon and its small side holes won't follow the sketched flute logic, but if the intervals between open holes are kept, for instance if the instrument sounds all cross-fingerings a semitone higher, then the simple fingerings are kept and only shifted. With narrow side holes at locations differing from the Heckel system, this system needs a redesign of the instrument, lengthy to tune properly since the adequate cross-fingerings are still unknown. It can be worth it as the keys are simple and enable very uniform and perfect hole combinations. Marc Schaefer, aka Enthalpy

Here I compare the payload mass in geosynchronous orbit with electric versus sunheat engines. ----------- Ariane 64 and Hall ----------- Fakel's Spt140D has been used on Eutelsat 172b http://www.fakel-russia.com/images/content/products/fakel_spd_en_print.pdf and Ariane VA237 put it on the usual GTO: 250km*35706km*6°, from where a 1465m/s short kick would achieve Gso. This Hall thruster offers Isp=1770s=17360m/s and 0.29N from 4500W, so the 3550kg satellite's 13kW (end-of-life?) solar panels feed 3 engines for 0.87N or 245µm/s2. 4714m/s spiralling from Leo would need 8.5 months, and even longer for heavier satellites, but in 4 months the Hall thrusters achieved Gso from Gto. To save delays, the apogee pushes are very long hence inefficent. Let's say they must provide 1.2*1465=1758m/s: the payload is 0.90* as heavy once in Gso. Scaling up to 11500kg in Gto for Ariane 64, 1108kg xenon are consumed, plus 83kg for a bigger tank, and 85kg for 10 Hall thrusters. This leaves 10220kg in Gso for the satellites and a dual launch adapter. Other transfer orbits would improve. The long pushes raise the apogee too, so a lower one is better. A perigee higher than 1000km would reduce the risk of collisions. A mid-high circular orbit would let the electric satellite spiral to Gso. Ariane 6's user's manual gives masses to these orbits. But as long as chemical satellites buy half-launches, Ariane will target the usual Gto, maybe Gso (5000kg there). ------------ Falcon 9 and Hall ----------- The outdated but documented Falcon 9 v1.0 put 4536kg to Gto 185km*35786km*28.5°, from where a short 1826m/s kick achieves Gso. Let's take 2191m/s with Hall thrusters: the payload weighs 3998kg in Gso, minus 40kg tank and 34kg thrusters, that's 3924kg in Gso. ---------- Ariane 6 and sunheat ---------- As estimated on Apr 15 & 19, 2018, Ariane 64 and a sunheat stage would put 13.1t at Gso in 3 months or less. This 2880kg or 28% improvement over Hall thrusters starting from Gto is worth 25M$, plus the saved delay. Ariane 62 and a sunheat stage would put 6.1t at Gso in 2 months, that's 1251kg or 26% better than Hall thrusters. Worth 18M$ or 20M$, the price of upgrading to Ariane 64. The transfer time is one month for 360kg or 120kg less payload. ---------- Falcon 9 and sunheat ---------- Falcon 9 v1.0 put 10000kg at 400km*28.5°, from where I estimate imprecisely to 5552m/s the cost to spiral to Gso and suppress the inclination simultaneously. This leaves 6396kg at Gso, of which 1016kg are the dry sunheat stage (282kg/t as for Ariane) and 5380kg the payload at Gso in 2 months. That's 37% heavier than Hall thrusters, a bigger advantage because Gto in two stages is demanding. At 56M$ per launch (?) the gain is 21M$. Marc Schaefer, aka Enthalpy

Here's a more detailed mass estimate of the sunheat stage for Ariane 6. Computed to break at 2.2MN*m (6.4t on A62) or 8.6MN*m (13.7t on A64) and to work at 1.5atm (boiling 2K warmer than 1atm). The truss is cold at A64. kg kg 190 360 290µm or 370µm steel balloon with brazed seams 74 94 22mm or 17mm foam for 1000s after trickle hydrogen removed 61 76 25 or 19 plies of 13µm MLI for additional 7 idle days in vacuum 10 20 Polymer straps holding the balloon 250 700 Welded truss of Di=80mm e=1,4mm AA6082 or Di=98mm e=2,6mm AA7022 no 83 Upper short insulating truss of Di=116mm e=4,4mm glass fibre epoxy no 0 Lower insulating truss already thrown away 120 180 4 or 6 engines 20 30 Engines' deployment and orientation no 0 Shell already thrown away 100 100 Equipment if not in the spacecraft 30 30 1.5 remaining separation belts 50 50 Undetailed ---------- 905 1723 kg dry stage 282 and 254kg per ton of propellant is heavy but would improve at a lighter space probe. The 5* denser couple with oxygen would scale it as 56 and 51kg/t, outperforming the projected Esc-B. I wouldn't be surprised if Ariane 6, whose manual tells masses landed on the Moon, uses the already suggested insulation stack http://www.scienceforums.net/topic/60359-extruded-rocket-structure/?do=findComment&comment=761740 At the A62's truss, tubes of isogrid AA7022 would improve over smooth AA6082. At the A64's truss, tubes of isogrid Ti-Al6V4 would improve over AA7022, be weldable, and could replace the glass fibre trusses too. Everywhere, balloons and trusses made of graphite composite would be half as heavy, and the walls of graphite tubes could be a balsa sandwich to save more mass. These sandwich tubes could replace the glass fibre trusses too. The throwaway windshield shells are already described http://www.scienceforums.net/topic/60359-extruded-rocket-structure/?do=findComment&comment=764231 Marc Schaefer, aka Enthalpy

An ion thruster would accelerate itself and its solar panels enough. Geosynchronous telecom satellites weigh about 4 to 7 tons in Gto, or 2.5 to 5 tons in Gso. Their 15kW take a few 100kg panels, but the claimed 150W/kg would take just 100kg, so there is margin. Fakel's Spt140D takes 15kW/N so the absolute limit would be 10mm/s2, enough for most missions. For the sunheat engine, this limit or factor-of-merit is 2.4N/30kg or 80mm/s2. This comparison is more important farther from the Sun. The hardest limit to ion propulsion is the cost of the solar panels.

The first user's manual for Ariane 6 is published and it details preliminary performance to varied orbits, nice. Once put on low-Earth-orbit by Ariane 6, heavier satellites can attain the geosynchronous orbit using sunheat engine. The sunheat stage would spiral from 400km 6° to 35800km 0°. This costs 4700m/s, 500m/s more than a Hohmann transfer, but saves a year. With Ariane 62, the fairing can house the 3.2t hydrogen and the payload. This brings no higher stresses on the previous stages, but needs trickle hydrogen under the fairing at pre-launch. The satellite owner can operate the sunheat stage, use the existing sensors and electronics. I take 120kg of structural tank per ton of hydrogen, 4 engines of 17kg for 2 months transfer, 100kg equipment if the launch company operates this stage. With Ariane 64 (or for missions of higher energy), 6.8t hydrogen need a tank outside the fairing and probably common to both customers. This suggests operation by the launch company. The stresses on the previous stages increase. I take 120kg of structural tank per ton of hydrogen, 6 engines of 17kg for 3 months transfer, 100kg equipment. Marc Schaefer, aka Enthalpy

Many telecom satellites use presently electric thrusters to raise the perigee from the transfer to the geosynchronous orbit. To achieve it in 4 to 7 months but save solar panels, the thrusters eject more propellant but slower than the Vasimr cited on Aug 19, 2017. For instance the Hall thruster PPS-1350-G in the table there https://en.wikipedia.org/wiki/Ion_thruster achieves 90mN at 1660s=16.3km/s from 1.5kW. This makes the solar panels 0.35* as huge as previously. The visual comparison with the sunheat engine becomes :

A direct comparison of the French (narrower) bassoon and the Heckel system (wider bore): https://www.youtube.com/watch?v=IIKc_1iCxMQ this time by the same musician. Very few people play both systems, as both are complicated and they differ enough to fool one. The video doesn't tell if the musician uses the same reed on both instruments - I suppose he does. Though, the narrower French system would take a smaller reed, which makes the sound softer. Anyway, the conclusion stands.