Enthalpy

The ABS decides the force applied on the brake pads while braking. Passenger's life depends fully on the electronics. Dreamliner battery: several caught fire in flight, forcing to land in emergency, and no extinguisher is meant to reach them... The Airbus 380 had the same battery chemistry. Airbus' response was "we'll replace the chemistry, we can because our batteries are smaller". But is some people start to argue that the battery's size lets them overheat, I wonder if Airbus considers keeping the dangerous battery chemistry. This would not be an "error" any more, and Internet has memory.

As of mid-2013, Ariane 6 is to have two solid stages and a Vinci hydrogen stage to put 6.5 t in Geosynchronous Transfer Orbit. One or two pressure-fed liquid stages before the Vinci make my design lighter, adaptable by a factor of three, and hopefully cheap as the sailback boosters are reused: (click to magnify) Instead of crossfeed, the boosters throttle from 36bar to 20bar to lighten the helium tank and weigh dry just 114kg per ton of propellants (45.1 t propellants each). Expansion to 0.35bar brings at sea level isp=2408m/s=246s and 1335kN each, and in vacuum isp=3043m/s=310s. The fairing is estimated at 2.6t. 2,3 or 4 boosters ignite at lift-off; if using 6 boosters, two ignite after the first four are separated. At the cone that tops the central stage, each side booster shares one thrust point with the adjacent side booster, and an internal truss connects the thrust points. Fastening the boosters high reduces the bending moment on the central stage, whose skin is of extruded AA6082 panels as I describe there: http://www.scienceforums.net/topic/60359-extruded-rocket-structure/ B=20mm b=18mm a=45° resist 715kN/m without margin, or sufficient 7.6MN*m with D=3m. The central stage contains up to 28.2t of propellants depending on the lower stage(s). It weighs 2.1t empty with all equipment and adapters. The vinci brings isp=4560m/s=465s and 180kN once the side boosters are separated. The roll and insertion Verniers can burn hydrogen fed by electric pumps, or Pmdeta which enables pressure-feed. An optional added stage with the Solar rocket engine I describe there http://www.scienceforums.net/topic/76627-solar-thermal-rocket/ can start with 12.5t from low-Earth-orbit to put 7.3t in geosynchronous orbit. More explanations will come some day about how the boosters splash down and sail back to the launch pad. Marc Schaefer, aka Enthalpy

Many electric motors for fans are (asynchronous) of squirrel cage type. Their rotation speed is determined to a few % by the mains' frequency. If doubling the supply voltage, they will burn without doubt, and before having made any useful service. More voltage is possible at motors with a commutator. These serve generally where a quick rotation is needed, for instance at vacuum cleaners. A commutator motor would response to an increase voltage with a higher rotation speed, while the absorbed current would increase only if more torque is demanded (this isn't linked simply with the internal resistance) - though, this is for parallel excitation; a series or compound excitation reacts differently. Mainly the absorbed current defines the losses in a motor, so the increased voltage alone wouldn't increase directly the power losses. Though, expect the commutator to work badly at excessive speed, and be destroyed quickly: that's the weak part of these motors.

http://en.wikipedia.org/wiki/Main_belt_asteroid some asteroids have quite inclined orbits, but very few have more than 35°: http://en.wikipedia.org/wiki/File:Main_belt_i_vs_a.png Everything in the same direction: not quite. - The Oort cloud is supposedly isotropic http://en.wikipedia.org/wiki/Oort_cloud - Distant moons of Jupiter and Saturn have very inclined orbits and many are retrograde. - Some planets have a very tilted axis: Uranus 98° http://en.wikipedia.org/wiki/Uranus , others 30° The general trend is heavy and has been noticed. If for instance all planets condensed from an accretion disk around the Sun, they would naturally orbit all in the same plane and direction. Collisions are supposed to explain much of the Solar system. Asteroid orbits inclined 20° or 30° suffice for good bangs: 30° makes already 9200m/s. Comets falling from the Oort cloud have any direction, including reverse; but since Jupiter organizes the main asteroid belt very much, an initial cause would be hard to tell from the present orbits.

Music instruments are passionating, so go on! Music instruments are the very difficult part of acoustics. Everything else is trivial in acoustics. Fun: with deep knowledge for acoustics, if you read patents from instruments makers, you can guess that they have better knowledge of acoustics than most academic researchers. They often claim "experimental discovery by chance" where chance is highly improbable and excellent knowledge must have guided them. Beware this Wiki article contains gross mistakes, about the 11th harmonic in tune or the effect of the vents. Beware also that sound quality does not result from harmonics, because sound is not periodic, and this is a fundamental quality of instruments. A musical sound can not be synthesized from harmonics, hence neither explained. The old Helmholtz made this mistake long ago, and since then almost everyone propagates it. One physics group in a Britanny university investigated this 20+ years ago, but it's too little known, and nearly everything remains to understand here.

Which means exactly that your life depends directly on the electronics and software that controls the ABS. If that software plays crazy, it can stop braking altogether. Or it can let your car slip when you need ABS action. You don't know under which circumstances they chose this battery chemistry and decided not to encase it. Maybe the battery manufacturer believed to have solved this issue. Remember the time when lithium batteries caught fire in laptops? This seems to be over. Possibly the environment of an aeroplane has raised a failure mode that wasn't known on terrestrial uses. Again, I find your style presumptuous. You ignore the context that brought the trouble, propose a very doubtful explanation, seem to imagine that engineering can run without surprises, and claim "they shouldn't make planes". That's hard.

One candidate to resist corrosion by vapour at 2400K is ZrO2 stabilized with Y2O3. For conductivity and if possible, zirconia should only cover a metal like tungsten or tantalum. If 2400K are sustainable, expansion from 2000Pa to 1Pa brings isp=3591m/s=366s. Main belt comets orbit rather at 3.1AU, some with a small inclination; only 6 bigger are known up to now, many more are expected. Spiralling from there to Mars takes (my mistake) 7210m/s, leaving 1/7.45 of the initial mass. The lower temperature reduces the heat leaks, but scaling only by the isp, and at mean 2.11AU from Sun, thirty D=4.7m engines eject 18g/s=1558kg/day vapour, or 2846t over 5 years, which would leave 441t near Mars with little inert mass. Sixty D=12m engines from an SLS fairing would deliver over 10 years 11500t water near Mars. The D=80m pond is 2.3m deep. Several thousand tonnes water boiled in few dm3 must be very pure to avoid scaling. Do it as you can. --------------- Some uses and engines need water, others oxygen and hydrogen, still others just hydrogen. At Mars, the same thirty D=4.7m concentrators can power turbines to produce 137kW electricity if pessimistic http://saposjoint.net/Forum/viewtopic.php?f=66&t=2051 of which 60% efficient electrolysis splits 0.29mol/s=450kg/day. The whole 440t take 2.7 years, resulting in 49.2t hydrogen. A cryocooler to keep the propellants liquid is described in the same linked topic. Whether water, only hydrogen, or as well oxygen are wanted, I find that transporting ice from the main belt by ejecting vapour takes fewer concentrators than making hydrogen at the main belt. --------------- At Mars or Earth, propellants brought from outer space are better kept near the planet than landed: the lighter crew or payload shall join the heavier propellants. An elliptic orbit, a high orbit or a Lagrange point are candidates, as is known. Marc Schaefer, aka Enthalpy

---------- This is what CPropepShel tells for 150:100 ratio: ---------- CHAMBER THROAT EXIT Pressure (atm) : 10.000 5.770 1.000 Temperature (K) : 1457.033 1368.268 1154.265 Isp (m/s) : 590.32222 1150.08875 Isp/g (s) : 60.19611 117.27641 CH4 7.3695e-006 9.3720e-006 1.6197e-005 CO 2.4772e-001 2.3932e-001 2.1335e-001 CO2 1.2421e-001 1.3140e-001 1.5630e-001 H 1.3607e-006 5.4951e-007 3.6607e-008 HCN 5.8517e-007 3.6625e-007 8.0481e-008 HNCO 2.4423e-007 1.4515e-007 2.7267e-008 H2 1.9358e-001 2.0207e-001 2.2809e-001 HCHO,formaldehy 2.4321e-007 1.4586e-007 2.7891e-008 HCOOH 3.4249e-007 2.0335e-007 3.8719e-008 H2O 2.3380e-001 2.2644e-001 2.0140e-001 K 3.2801e-004 1.5684e-004 1.6416e-005 KCN 1.9045e-006 9.0327e-007 8.1268e-008 KH 9.2841e-007 2.8737e-007 0.0000e+000 KOH 4.2806e-003 2.1437e-003 2.4746e-004 K2 1.4977e-008 0.0000e+000 0.0000e+000 K2CO3 4.8300e-006 2.2049e-006 1.7207e-007 K2O2H2 1.0039e-004 3.5809e-005 1.3074e-006 NH3 2.1401e-005 1.7850e-005 9.2672e-006 N2 9.9170e-002 9.9173e-002 9.9178e-002 OH 4.0358e-008 1.0771e-008 0.0000e+000 Condensed species K2CO3(L) 9.6771e-002 9.7993e-002 0.0000e+000 K2CO3(b) 0.0000e+000 0.0000e+000 9.9049e-002 ---------------------- and for the optimum 197:100: ---------------------- CHAMBER THROAT EXIT Pressure (atm) : 10.000 5.821 1.000 Temperature (K) : 1673.300 1598.166 1380.030 Isp (m/s) : 591.87466 1169.40976 Isp/g (s) : 60.35442 119.24661 CH4 4.2282e-008 3.6128e-008 2.5866e-008 CO 1.7677e-001 1.7145e-001 1.5293e-001 CO2 1.6845e-001 1.6933e-001 1.7586e-001 COOH 9.4129e-009 0.0000e+000 0.0000e+000 H 1.0385e-005 6.5103e-006 1.1699e-006 HCN 1.2019e-007 7.5784e-008 1.6679e-008 HCO 1.7593e-008 0.0000e+000 0.0000e+000 HNCO 1.2569e-007 7.5346e-008 1.4125e-008 H2 9.2749e-002 9.8295e-002 1.1769e-001 HCHO,formaldehy 7.9391e-008 4.8660e-008 9.7228e-009 HCOOH 2.6167e-007 1.5544e-007 2.8789e-008 H2O 2.9234e-001 2.9100e-001 2.8275e-001 K 3.6727e-003 3.2278e-003 1.5141e-003 KCN 1.4064e-006 9.3495e-007 1.9852e-007 KH 1.0393e-005 6.4167e-006 9.2099e-007 KO 3.3645e-008 1.2641e-008 0.0000e+000 KOH 4.1552e-002 3.4130e-002 1.3626e-002 K2 9.7556e-007 5.4702e-007 4.3780e-008 K2CO3 6.0504e-005 4.7093e-005 1.4805e-005 K2O 3.4613e-008 1.4916e-008 0.0000e+000 K2O2H2 1.6017e-003 1.1131e-003 2.2933e-004 NH3 4.3591e-006 3.3794e-006 1.5265e-006 NO 3.2116e-008 1.2385e-008 0.0000e+000 N2 1.2353e-001 1.2353e-001 1.2353e-001 OH 1.5730e-006 7.4935e-007 5.1560e-008 Condensed species K2CO3(L) 9.9253e-002 1.0369e-001 1.1572e-001 so: - 197:100 would have been more efficient, but that little sugar would make the solid brittle. - same reason at launchers. Less polybutadiene would have improved performance. - CO is about as abundent as CO2, even at the optimum ratio. - Much unburnt H2 is left as well - typical for hot combustion.

Twice the radius and the mass would mean that the planet's density decreases with size. If you take a similar composition and "compactness", hence density, then gravity increases like the radius. Small asteroids and small moons are known to be fluffy, with density well below ice.

Yes, in the proton-proton cycle, strong interaction attracts two protons together; most often they separate again (which is in favour of an "equilibrium" and an equation of state), sometimes the "di-proton" becomes a deuteron by weak interaction, that is beta plus emission. That's at least what Wiki tells. A di-proton has never been observed, as far as I know. Maybe one proton must undergo the beta decay at the same time as it fuses with the other proton. Beta before should be excluded since it would require several billion K. In the formation of a neutron star in contrast, (negative) electrons are absorbed to make neutrons, while in the proton-proton cycle according to Wiki, a positron is emitted; the mass balance differs a lot. There, the strong force can't be the main cause, since atoms heavier than lead are radioactive even with the best possible proportion of neutrons; gravity provides the energy. No, the strong force alone doesn't produce nuclei past iron approximately. Gravity provides the energy, but to make a neutron star, it needs the weak interaction to produce neutrons. If I get it properly (take with care), light electrons take more room than heavy neutrons. As nearly all nuclear reactions that provide net energy are exhausted, the star's (largely radiative) equilibrium is lost and the star collapses. The but-last reactions would still have fuel but they don't burn stably.

Ceramic coatings are used on metals, for instance to improve the resistance against corrosion, so the melting point is not the only criterion. Additionally, alloys are limited far before their melting point, especially by creeping; nickel superalloys for instance can be used to 700°C or 900°C only, and iron alloys even less.

I happily read you agreement that software has full control over present ABS car brakes. Which removes the objections against electric actuators to replace hydraulic ones, since software already controls hydraulic actuators, in aeroplanes as well. Fireproof case: I prefer this to a lithium battery supposed to be safer. Your style is incredibly presumptuous. You probably have only press reports, come with a bizarre theory about big batteries - though they've been around for years - and allege the companies working on it can't solve it and must not be trusted. Fact is that engineering comes with surprises, be it errors, unknown terrain or plain bad luck. Aeroplane manufacturers are not "willing" to risk your life: they're just surprised by where and how problems occur. Aeroplane accidents can be deadly, yes. So is electricity - which you probably use to write here. Risks don't suffice to reject changes. In case you're suggesting that Boeing willingly ignored the risk of this lithium battery chemistry: Airbus had chosen the same on the 380... Airbus have changed the chemistry since the batteries caught fire on the Dreamliner. I wish they encased them, in addition.

This is a typical hot reaction. Combustions in air tend to make CO2 because 80% nitrogen cool the flame a lot. Not so with pure oxygen, nor with oxygen-rich reactants like KNO3. Heat decomposes CO2 partially, so the reaction makes both CO2 and CO. The best proportion, that brings enough oxygen to produce favourable CO2 but not excessive O2, is not really accessible to hand computation. More energetic reactions would also decompose H2O. Software exists because of that. You can try RPA and Propep: http://www.propulsion-analysis.com/downloads.htm http://www.dark.dk/download (seems 404, search alsewhere for CPropepShell) From CPropepShell, taking with no good reason 10 atm in the chamber and 1 atm down the nozzle, I get 197:100 mass nitrate:sucrose, with 0.15*CO for 0.18*CO2 down the nozzle. A higher chamber pressure allows more oxidizer. I suppose the fabrication process limits the proportion of nitrate. That's true for big launchers as well.

pH=11 means 10-3 mol OH- per litre. 59,000 L water contain 59 mol OH-, to be neutralized by 59 mol of pure HCl or 2.15kg. If 33% is a mass concentration, it takes 6.5 kg, or about 6 L. pH=9 or 10-5 mol OH- per litre needs you to neutralize with 1% accuracy, but the pH=11 measure isn't so accurate, so you need to mix and monitor the pH during the operation. If your pond is made of concrete, and if this has made pH=11 (which needs a good reason!), the pH may drift further over time and when the neutralization is conducted. Just wait until John Cuthber passes by. If I botched that, he will let it notice.

Hi Alinoroozi, welcome here! Don't worry for the language: English isn't my native one neither - but I'm happy that we share a language. The main reason is that, due to the finite age of the Universe (some 14 thousand million years), we see only a finite part of it (14 thousand million light-years radius), from which light has had enough time to arrive to us. The rest is too far, and its light hasn't reached us up to now. An other important contribution is that, because distant galaxies fly away from us, their light shifts to the red and infrared, and loses power in that shift.

Detecting a transmitter is much easier than receiving properly the data. It can be done by integrating over much time the cross-correlation of signals from two receivers. Imagine that we barely receive 100 bit/s from a distant probe through 40m antennas. Integrating the correlation over 10,000s (...not obvious, needs to compensate movements etc, but usual in radioastronomy) and you detect signals 1,000 times fainter, which improves the range by 30. In the favourable direction, banal human technology would detect said probe not at 15 light-hours but 21 light-days. Then, 0.5km2 antennas multiply the range by 20, or 1 light-year with current human possibilities. Any hint to the technology they have, at 5 light-years? Though, Voyager wouldn't be the strongest transmitter of Mankind.

Again the same old story... Widdekind, you need to understand that the weak interaction transforms protons and electrons to neutrons. The strong force doesn't. ----- An attractive strong interaction could maybe have been treated to the plasma's equation of state as a corrective Van der Waal's force is in gas... but: why? - Our Sun takes 10 billion years to fuse hydrogen to helium, and only through indirect processes. Not by shocks between protons. Now consider how many shocks per second for a proton in the Sun: what can be the significance of this correction? - Fusion is generally not reversible. It creates new species like 3He or n. This is a strong contrast with molecular shocks. One couldn't use such a fusion as a corrective pressure for 2H. - More generally, an evolutive interaction has not its place in an equilibrium equation. The star is not at nuclear equilibrium, which would be a chunk of iron. Fusion is essentially a dissipation mechanism; helium won't give hydrogen back if you lower the pressure, even at Sun's temperature. Only non-nuclear interaction define a plasma equation of state.

Phonons have their usefulness in crystals to define curves of E versus p and deduce how they interact with electrons or change the interaction of photons and electrons. As well, some phonons in crystals have a huge frequency, making individual ones more interesting. In air, where sound speed is essentially constant, frequency is low and electrons not so interesting, why use quantum mechanics and define phonons? The classical description has the fabulous advantage of being understandable and useable - QM less so...

As humans also contain much of diamagnetic water, it would work - BUT it's a matter of size and power. https://en.wikipedia.org/wiki/Diamagnetism (the frog) https://en.wikipedia.org/wiki/Magnetic_levitation#Diamagnetism www.youtube.com/watch?v=2FvWtEdY4sE(water free surface deformed by a permanent magnet) For the frog, they had 16T... JPL levitated mice later. All these are in the many-MW area, which explains why teams choose small objects or beings.

A wider core would increase the flux for the same saturation induction, yes, and this would avoid to increase too much the number of turns. Ultimately, it would have allowed to use Permalloy in a transformer core. But we don't desire it! We want small transformers, because laminations and copper have a price, and transformers are always too heavy. What designers desire is a higher induction at saturation. We want a small core so the copper windings are short hence dissipate less. (The rationale as well is shortened here, but it's the proper direction and ultimate reason). A wider and longer core dissipates more due to its volume, lessening the advantage of Permalloy. Incidentally, the permeability defines the reactive current (the magnetizing current) that passes the primary when the secondary delivers no current; this reactive current is not directly a dissipation in the transformer, but it has drawbacks. The power losses in the core relate instead with the material's hysteresis (which Permalloy would be good as well) and laminations' eddy currents (3% silicon in transformer iron is as good as much nickel). One excellent reason against Permalloy is that nickel is expensive. Silicon in transformer iron is cheap.

Hydrogen is the propellant that improves the exhaust speed over chemical reactions, but the Solar thermal engine accepts other propellants. Water at 2400K can give some 3000-4000m/s ejection speed, depending on the dissociation allowed by the chamber pressure - and if available in space, it enables big scenarios where the in-situ propellant needs no lengthy preparation. Corrosion is a serious worry, hence the 2400K. If metals don't survive hot vapour, ceramics may: MgO and ZrO2, with 100K less? Tantalum hafnium carbide? Imagine that we find main-belt comets of the proper size and clean enough http://en.wikipedia.org/wiki/Main-belt_comet they can refill a spacecraft's tank after a simple purification - faster and lighter than electrolysis. A part of the icy object can fuel the Solar rocket to bring the rest (or a different asteroid) to a remote location. To a Lunar orbit: too easy now with the Solar thermal engine! "Think big" means again: manned Mars mission. To a Martian orbit or Mars' surface, for more ambitious uses. Granting the engine some time enables a scale more pleasant than our present space tinkering. Take thirty 4.7m concentrators that fit in one launch: at mean 2 AU, each ejects 40kg/day vapour at 4030m/s, or together 2,200t in 5 years. As the travel from the main belt to Mars takes 4820m/s, it leaves 1000t water at Mars. That's a swimming pool of 2m*50m*10m. Enough to refill a rocket there to return to Earth, possibly after separation into hydrogen and oxygen. Or to grow vegetables? Mars' gravitation is only 30 times ice's heat of fusion, so chunks of some proper size may aerobrake and reach the ground but cause limited damage. Sixty 12m concentrators fit in one SLS fairing. These would bring in 10 years 26,000t water to Mars, or 5m*D80m: that's a pond. A duly megalomaniac inventor (salut Guy Pi) proposed to veer a comet off course and smash it on Mars for terraforming; still not quite the proper size, but it's a first step. Marc Schaefer, aka Enthalpy

It is already the case, for a long time: http://en.wikipedia.org/wiki/Anti-lock_braking_system the driver provides the pressure (my mistake) whose use is fully controlled by software. Same for airliners since the A320 in 1984: http://en.wikipedia.org/wiki/Fly-by-wire software decides everything and overrides the pilot's inputs in many modes. If electronics and (gasp!) software are already in the loop, I do prefer to stay with power electronics and electric actuators than make the final step with hydraulics - where it's possible. I used both for crash-test technology, and too often to our taste, hydraulics was unreplaceable. About the battery's defects, I strongly doubt the explanation is "too big elements". Much bigger batteries have already been operated. But knowing that some lithium chemistries have already caught fire in laptops, I'd have strongly favoured others, or to the very least I'd have encased the elements from the beginning. Certification should have demanded it as well. Serious worries in a new plane design? Sure. Other planes, not all as innovative as the Dreamliner, have had more.

Radioastronomy works at huge distances, including at frequencies around Voyager's transmission, so the medium is not a limit. But the power received is certainly one.

Reliability can't be inferred from impressions of complexity. It's really a matter of observation, and hydraulics do fail. To become half-way reliable, they need intense and regular maintenance, and they still fail. Do you believe the airliner pilot creates hydraulic pressure with his feet? I regret the disappointment... He acts on sensors, other sensors observe the position of the control surfaces, and in between, a computer tells a servovalve what flow to send to the actuator. Worse: on present airliners, the pilot's action doesn't determine the position of the control surfaces. The pilot tells the computer what the plane is supposed to do, and the computer deduces the action on the control surfaces. It's much the same with car brakes. Since the ABS, the driver acts on a sensor, a computer decides what to do. In this context, an electric actuator introduces no more software and electronics than a hydraulic one.

The outline of the future Ariane 6 has been chosen recently, with two solid stages and one hydrogen: explosive, highly flammable, polluting, and if hydrazine provides the roll control, carcinogenic and toxic. Criticism is easy, art is difficult, so here's an alternative with oxygen and Pmdeta. Click the sketch to magnify The last stage has electric pumps as described here previously. The two first "sailback" stages are pressure-fed and reused as I describe there http://saposjoint.net/Forum/viewtopic.php?f=66&t=2554 Liquids lighten the launcher, even without hydrogen, and with pumps only at the small upper engine. To put 4.1t on geosynchronous orbit (or 6.8t on transfer) from the Equator: The last stage begins 2000m/s before Low-Earth-Orbit with 26.4t composite, burns 20.8t (or 18.1t) at 60bar expanded to 335Pa for isp=394s, ending 3953m/s (or 2457m/s) above Leo. 1560kg dry mass include batteries for the pumps, balloon tanks, an aluminium truss, sensors, control, transmissions. The second stage provides 4100m/s by burning 88.5t at 36bar (throttled to 18bar at the end) expanded to 0.081bar for isp=341s. The composite begins with 125.3t; stage dry mass is 9.9t with steel tanks, helium, engines, paraglider and the rest. The first stage provides 3400m/s by burning 398t at 36bar (throttled to 18bar) expanded to 0.47bar; isp=303s in vacuum and 254s at sea level. The composite begins with 569t; stage dry mass is 44.6t. Marc Schaefer, aka Enthalpy