Category Archives: Science: Physics, Astronomy, etc.

Boy-Girl physics humor

Girl breaking up with her boyfriend: I just need two things, more space, and time.

Atoms try to understand themselves.

Atoms build physicists in an attempt to understand themselves. That’s also why physicists build physics societies and clubs.

Boyfriend: So, what’s the other thing?

 

Robert Buxbaum. And that, dear friend, is why science majors so rarely have normal boyfriends / girlfriends.

A female engineer friend of mine commented on the plight of dating in the department: “The odds are good, but the goods are odd.”

By the way, the solution to Einstein’s twin paradox resides in understanding that time is space. Both twins see the space ship moving at the same pace, but space shrinks for the moving twin in the space ship, not for the standing one. Thus, the moving twin finishes his (or her) journey in less time than the standing one observes.

The chemistry of sewage treatment

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The first thing to know about sewage is that it’s mostly water and only about 250 ppm solids. That is, if you boiled down a pot of sewage, only about 1/40 of 1% of it would remain as solids at the bottom of the pot. There would be some dried poop, some bits of lint and soap, the remains of potato peelings… Mostly, the sewage is water, and mostly it would have boiled away. The second thing to know, is that the solids, the bio-solids, are a lot like soil but better: more valuable, brown gold if used right. While our county mostly burns and landfills the solids remnant of our treated sewage, the wiser choice would be to convert it to fertilizer. Here is a comparison between the composition of soil and bio-solids.

The composition of soil and the composition of bio-solid waste. biosolids are like soil, just better.

The composition of soil and the composition of bio-solid waste. biosolids are like soil, just better.

Most of Oakland’s sewage goes to Detroit where they mostly dry and burn it, and land fill the rest. These processes are expensive and engineering- problematic. It takes a lot of energy to dry these solids to the point where they burn (they’re like really wet wood), and even then they don’t burn nicely. As shown above, the biosolids contain lots of sulfur and that makes combustion smelly. They also contain nitrate, and that makes combustion dangerous. It’s sort of like burning natural gun powder.

The preferred solution is partial combustion (oxidation) at room temperature by bacteria followed by conversion to fertilizer. In Detroit we do this first stage of treatment, the slow partial combustion by bacteria. Consider glucose, a typical carbohydrate,

-HCOH- + O2 –> CO2 + H2O.    ∆G°= -114.6 kcal/mol.

The value of ∆G°, is relevant as a determinate of whether the reaction will proceed. A negative value of ∆G°, as above, indicates that the reaction can progress substantially to completion at standard conditions of 25°C and 1 atm pressure. In a sewage plant, many different carbohydrates are treated by many different bacteria (amoebae, paramnesia, and lactobacilli), and the temperature is slightly cooler than room, about 10-15°C, but this value of ∆G° suggests that near total biological oxidation is possible.

The Detroit plant, like most others, do this biological oxidation treatment using either large stirred tanks, of million gallon volume or so, or in flow reactors with a large fraction of cellular-material returning as recycle. Recycle is needed also in the stirred tank process because of the low solid content. The reaction is approximately first order in oxygen, carbohydrate, and bacteria. Thus a 50% cell recycle more or less doubles the speed of the reaction. Air is typically bubbled through the reactor to provide the oxygen, but in Detroit, pure oxygen is used. About half the organic carbon is oxidized and the remainder is sent to a settling pond. The decant (top) water is sent for “polishing” and dumped in the river, while the goop (the bottom) is currently dried for burning or carted off for landfill. The Holly, MI sewage plant uses a heterogeneous reactors for the oxidation: a trickle bed followed by a rotating disk contractor. These have higher bio-content and thus lower area demands and separation costs, but there is a somewhat higher capital cost.

A major component of bio-solids is nitrogen. Much of this in enters the form of urea, NH2-CO-NH2. In an oxidizing environment, bacteria turns the urea and other nitrogen compounds into nitrate. Consider the reaction the presence of washing soda, Na2CO3. The urea is turned into nitrate, a product suitable for gun powder manufacture. The value of ∆G° is negative, and the reaction is highly favorable.

NH2-CO-NH2 + Na2CO3 + 4 O2 –> 2 Na(NO3) + 2 CO2 + 2 H2O.     ∆G° = -177.5 kcal/mol

The mixture of nitrates and dry bio-solids is highly flammable, and there was recently a fire in the Detroit biosolids dryer. If we wished to make fertilizer, we’d probably want to replace the drier with a further stage of bio-treatment. In Wisconsin, and on a smaller scale in Oakland MI, biosolids are treated by higher temperature (thermophilic) bacteria in the absence of air, that is anaerobically. Anaerobic digestion produces hydrogen and methane, and produces highly useful forms of organic carbon.

2 (-HCOH-) –> CO2 + CH4        ∆G° = -33.7 Kcal/mol

3 (-HCOH-) + H2O –> -CH2COOH + CO2 +  2 1/2 H2        ∆G° = -21.9 kcal/mol

In a well-designed plant, the methane is recovered to provide heat to the plant, and sometimes to generate power. In Wisconsin, enough methane is produced to cook the fertilizer to sterilization. The product is called “Milorganite” as much of it comes from Milwaukee and much of the nitrate is bound to organics.

Egg-shaped, anaerobic biosolid digestors.

Egg-shaped, anaerobic biosolid digestors, Singapore.

The hydrogen could be recovered too, but typically reacts further within the anaerobic digester. Typically it will reduce the iron oxide in the biosolids from the brown, ferric form, Fe2O3, to black FeO.  In a reducing atmosphere,

Fe2O3 + H2 –> 2 FeO + H2O.

Fe2O3 is the reason leaves turn brown in the fall and is the reason that most poop is brown. FeO is the reason that composted soil is typically black. You’ll notice that swamps are filled with black goo, that’s because of a lack of oxygen at the bottom. Sulphate and phosphorous can be bound to ferrous iron and this is good for fertilizer. Generally you want the reduction reactions to go no further.

Weir dam on the river dour. Used to manage floods, increase residence time, and oxygenate the flow.

Weir dam on the river Dour in Scotland. Dams of this type increase residence time, and oxygenate the flow. They’re good for fish, pollution, and flooding.

When allowed to continue, the hydrogen produced by anaerobic digestion begins to reduce sulfate to H2S.

NaSO4 + 4.5 H2 –>  NaOH + 3H2O + H2S.

I’m running for Oakland county, MI water commissioner, and one of my aims is to stop wasting our biosolids. Oakland produces nearly 1000,000 pounds of dry biosolids per day. This is either a blessing or a curse depending on how we use it.

Another issue, Oakland county dumps unpasteurized, smelly black goo into Lake St. Clair every other week, whenever it rains more than one inch. I’d like to stop this by separating the storm and “sanitary” sewage. There is a capital cost, but it can save money because we’d no longer have to pay to treat our rainwater at the Detroit sewage plant. To clean the storm runoff, I’d use mini wetlands and weir dams to increase residence time and provide oxygen. Done right, it would look beautiful and would avoid the flash floods. It should also bring natural fish back to the Clinton River.

Robert Buxbaum, May 24 – Sept. 15, 2016 Thermodynamics plays a big role in my posts. You can show that, when the global ∆G is negative, there is an increase in the entropy of the universe.

Of horses, trucks, and horsepower

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Horsepower is a unit of work production rate, about 3/4 of a kW, for those who like standard international units. It is also the pulling force of a work horse of the 1700s times its speed when pulling, perhaps 5 mph. A standard truck will develop 200 hp but only while accelerating at about 60 mph; to develop those same 200 horsepower at 1 mph it would have to pull with 200 times more force. That is impossible for a truck, both because of traction limitations and because of the nature of a gasoline engine when attached to typical gearing. At low speed, 1 mph, a truck will barely develop as much force as 4-5 horses, suggesting a work output about 1 hp. This is especially true for a truck pulling in the snow, as shown in the video below.

Here, a semi-truck (of milk) is being pulled out of the snow by a team of horses going perhaps 1 mph. The majority of work is done by the horse on the left — the others seem to be slipping. Assuming that the four horses manage to develop 1 hp each (4 hp total), the pull force is four times a truck at 1 mph, or as great as a 200 hp truck accelerating at 50 mph. That’s why the horse succeed where the truck does not.

You will find other videos on the internet showing that horses produce more force or hp than trucks or tractors. They always do so at low speeds. A horse will also beat a truck or car in acceleration to about the 1/4 mile mark. That’s because acceleration =force /mass: a = F/m.

I should mention that DC electric motors also, like horses, produce their highest force at very low speeds, but unlike horses, their efficiency is very low there. Electric engine efficiency is high only at speeds quite near the maximum and their horse-power output (force times speed) is at a maximum at about 1/2 the maximum speed.

Steam engines (I like steam engines) produce about the same force at all speeds, and more-or-less the same efficiency at all speeds. That efficiency is typically only about 20%, about that of a horse, but the feed cost and maintenance cost is far lower. A steam engine will eat coal, while a horse must eat oats.

March 4, 2016. Robert Buxbaum, an engineer, runs REB Research, and is running for water commissioner.

Alcohol and gasoline don’t mix in the cold

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One of the worst ideas to come out of the Iowa caucuses, I thought, was Ted Cruz claiming he’d allow farmers to blend as much alcohol into their gasoline as they liked. While this may have sounded good in Iowa, and while it’s consistent with his non-regulation theme, it’s horribly bad engineering.

At low temperatures ethanol and gasoline are no longer quite miscible

Ethanol and gasoline are that miscible at temperatures below freezing, 0°C. The tendency is greater if the ethanol is wet or the gasoline contains benzenes

We add alcohol to gasoline, not to save money, mostly, but so that farmers will produce excess so we’ll have secure food for wartime or famine — or so I understand it. But the government only allows 10% alcohol in the blend because alcohol and gasoline don’t mix well when it’s cold. You may notice, even with the 10% mixture we use, that your car starts poorly on the coldest winter days. The engine turns over and almost catches, but dies. A major reason is that the alcohol separates from the rest of the gasoline. The concentrated alcohol layer screws up combustion because alcohol doesn’t burn all that well. With Cruz’s higher alcohol allowance, you’d get separation more often, at temperatures as high as 13°C (55°F) for a 65 mol percent mix, see chart at right. Things get worse yet if the gasoline gets wet, or contains benzene. Gasoline blending is complex stuff: something the average joe should not do.

Solubility of dry alcohol (ethanol) in gasoline. The solubility is worse at low temperature and if the gasoline is wet or aromatic.

Solubility of alcohol (ethanol) in gasoline; an extrapolation based on the data above.

To estimate the separation temperature of our normal, 10% alcohol-gasoline mix, I extended the data from the chart above using linear regression. From thermodynamics, I extrapolated ln-concentration vs 1/T, and found that a 10% by volume mix (5% mol fraction alcohol) will separate at about -40°F. Chances are, you won’t see that temperature this winter (and if you you do, try to find a gas mix that has no alcohol. Another thought, add hydrogen or other combustible gas to get the engine going.

Robert E. Buxbaum, February 10, 2016. Two more thoughts: 1) Thermodynamics is a beautiful subject to learn, and (2) Avoid people who stick to foolish consistency. Too much regulation is bad, as is too little: it’s a common pattern: The difference between a cure and a poison is often just the dose.

How to help Flint and avoid lead here.

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As most folks know, Flint has a lead-poisoning problem that seems to have begun in April, 2014 when the city switched its water supply from Detroit-supplied, Lake Huron water to their own source, water from the Flint River. Here are some thoughts on how to help the affected population, and how to avoid a repeat in Oakland county, where I’m running for water commissioner. First observation, it is not enough to make sure that the source water does not contain lead. The people who decided on the switch had found that the Flint river water had no significant content of lead or other obvious toxins. A key problem, it seems: the river water did not contain anticorrosion phosphates, and none, it seems, were added by the Flint water folks. It also seems that insufficient levels of chlorine (hypochlorite) were added. After the switch, citizens started seeing disgusting, brown water come from their taps, and citizens with lead pipes or solder were poisoned with ppb-levels of lead. There was also an outbreak of legionaries disease that killed 12 people. It was the legionaries that alerted the CDC to the possibility of lead, since it seems the water folks were fudging the numbers there, and hiding that part of the problem.

Flint water, Sept 2015, before switching back to Lake Huron.

Flint water after 5 hours of flushing, Sept 2015, before switching back to Lake Huron.

The city began solving its problem by switching back to Detroit-supplied, Lake Huron water in October, 2015. Beginning in December, 2015, they started adding triple doses of phosphate to the wate. As a result, Flint tap-water is now back within EPA standards, but it’s still fairly unsafe, see here for more details.

There has been a fair amount of finger-pointing. At Detroit for raising the price of water so Flint had to switch, at water officials ignoring the early signs of lead and fudging their reports, at other employees for not adding phosphate or enough chlorine, and at “the system” for not providing Flint’s government with better oversight. My take is that a lot of the problem came from the ignorance of the water commission, and it’s commissioner. We elect our water commissioners to be competent overseers of complex infrastructure, but in may counties folks seem to pick them the same way they pick aldermen: for a nice smile, a great handshake, and an ability to remember names. That, anyway, seems to be the way that Oakland got its current water commissioner. When you pick your commissioner that way, it’s no surprise that he (or she) isn’t particularly up on corrosion chemistry, something that few people understand, and fewer care about until it bites them.

Flint river water contains corrosive chloride that probably helped dissolve the lead from pipes and solder. Contributing to the corrosion problem, I’m going to guess that Flint River water also contains, relatively little carbonate, but significant amounts of chelating chemicals, like EDTA, in 10s of ppb concentration. EDTA isn’t poisonous at these concentrations, but it’s common in industry and is the most commonly used antidote for lead poisoning. EDTA extracts lead and other metals from people and would tend to contribute to the process of extracting lead and iron oxide from the pipes surface into the drinking water. With EDTA in the water, a lot of phosphate or hypochlorite would be needed to avoid the lead poisoning problem and the deadly multiplication of disease.

Detroit ex-mayor Kwame Kilpatrick has claimed that both Flint water and Detroit water were known to be poisoned even a decade before the switch. I find these claims believable given the high levels of lead in kids blood even before the switch. Also, I note that there are areas of Detroit where the blood-lead levels are higher than Flint. Flint tested at the taps in a way that fudged the data during the first days of the poisoning, and I suspect many of our MI cities do this today — just to make the numbers look better. My first suggestion therefore is to test correctly, both at the pipes and at the taps; lead pipes are most-often found in the last few feet before the tap. In particular, we should test at all schools and other places where the state has direct authorization to fix the problem. A MI senate bill has been proposed to this effect, but I’m not sure where it stands in the MI house. It seems there are movements to add lots of ‘riders’ and that’s usually a bad sign.

Another thought is that citizens should be encouraged to test their private taps and helped to fix them. The state can’t come in and test or rip out your private pipes, even if they suspect lead, but the private owner has that authorization. The state could condemn a private property where they believe the water is bad, but I doubt they could evict the residents. It’s a democratic republic, as I understand; you have the right to be deadly stupid. But I’ll take my own suggestion to encourage you: If you think your water has lead, take a sample and call (517) 335-8184. Do it.

Another suggestion, perhaps the easiest and most important, is drink bottled water for now, and if you feel you’ve been poisoned, take an antidote.  As I understand things, the state is already providing bottles of imported water. The most common antidote is, as I’d mentioned, EDTA. Assuming that Flint River water had enough EDTA to significantly worsen the problem, the cheapest antidote might be Flint River water, assuming you drew it in lead-free pipes and chlorinated sufficiently to rid it of bugs. If there is EDTA it will help the poisoned. Another antidote is Succinic acid, something sold by REB Research, my company. As with EDTA it is non-toxic, even in fairly large doses, but its use would have to be doctor- approved.

Robert E. Buxbaum, January 19-31, 2016. I hope this helps. We’d have to check Flint River water for levels of EDTA, but I suspect we’d find biologically significant concentrations. If you think Oakland should have an engineer in charge of the water, elect Buxbaum for water commissioner.

Highest temperature superconductor so far: H2S

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The new champion of high-temperature superconductivity is a fairly common gas, hydrogen sulphide, H2S. By compressing it to 150 GPa, 1.5 million atm., a team lead by Alexander Drozdov and M. Eremets of the Max Planck Institute coaxed superconductivity from H2S at temperatures as high as 203.5°K (-70°C). This is, by far, the warmest temperature of any superconductor discovered to-date, and it’s main significance is to open the door for finding superconductivity in other, related hydrogen compounds — ideally at warmer temperatures and/or less-difficult pressures. Among the interesting compounds that will certainly get more attention: PH3, BH3, Methyl mercaptan, and even water, either alone or in combination with H2S.

Relationship between H2S pressure and critical temperature for superconductivity.

Relation between pressure and critical temperature for superconductivity, Tc, in H2S (filled squares) and D2S (open red). The magenta point was measured by magnetic susceptibility (Nature)

H2S superconductivity appears to follow the standard, Bardeen–Cooper–Schrieffer theory (B-C-S). According to this theory superconductivity derives from the formation of pairs of opposite-spinning electrons (Cooper pairs) particularly in light, stiff, semiconductor materials. The light, positively charged lattice quickly moves inward to follow the motion of the electrons, see figure below. This synchronicity of motion is posited to create an effective bond between the electrons, enough to counter the natural repulsion, and allows the the pairs to condense to a low-energy quantum state where they behave as if they were very large and very spread out. In this large, spread out state, they slide through the lattice without interacting with the atoms or the few local vibrations and unpaired electrons found at low temperatures. From this theory, we would expect to find the highest temperature superconductivity in the lightest lattice, materials like ice, boron hydride, magnesium hydride, or H2S, and we expect to find higher temperature behavior in the hydrogen version, H2O, or H2S than in the heavier, deuterium analogs, D2O or D2S. Experiments with H2S and D2S (shown at right) confirm this expectation suggesting that H2S superconductivity is of the B-C-S type. Sorry to say, water has not shown any comparable superconductivity in experiments to date.

We have found high temperature superconductivity in few of materials that we would expect from B-C-S theory, and yet-higher temperature is seen in many unexpected materials. While hydride materials generally do become superconducting, they mostly do so only at low temperatures. The highest temperature semiconductor B-C-S semiconductor discovered until now was magnesium boride, Tc = 27 K. More bothersome, the most-used superconductor, Nb-Sn, and the world record holder until now, copper-oxide ceramics, Tc = 133 K at ambient pressure; 164 K at 35 GPa (350,000 atm) were not B-C-S. There is no version of B-C-S theory to explain why these materials behave as well as they do, or why pressure effects Tc in them. Pressure effects Tc in B-C-S materials by raising the energy of small-scale vibrations that would be necessary to break the pairs. Why should pressure effect copper ceramics? No one knows.

The standard theory of superconductivity relies on Cooper pairs of electrons held together by lattice elasticity. The lighter and stiffer the lattice, the higher temperature the superconductivity.

The standard theory of superconductivity relies on Cooper pairs of electrons held together by lattice elasticity. The lighter and stiffer the lattice, the higher temperature the superconductivity.

The assumption is that high-pressure H2S acts as a sort of metallic hydrogen. From B-C-S theory, metallic hydrogen was predicted to be a room-temperature superconductor because the material would likely to be a semi-metal, and thus a semiconductor at all temperatures. Hydrogen’s low atomic weight would mean that there would be no significant localized vibrations even at room temperature, suggesting room temperature superconductivity. Sorry to say, we have yet to reach the astronomical pressures necessary to make metallic hydrogen, so we don’t know if this prediction is true. But now it seems H2S behaves nearly the same without requiring the extremely high pressures. It is thought that high temperature H2S superconductivity occurs because H2S somewhat decomposes to H3S and S, and that the H3S provides a metallic-hydrogen-like operative lattice. The sulfur, it’s thought, just goes along for the ride. If this is the explanation, we might hope to find the same behaviors in water or phosphine, PH3, perhaps when mixed with H2S.

One last issue, I guess, is what is this high temperature superconductivity good for. As far as H2S superconductivity goes, the simple answer is that it’s probably good for nothing. The pressures are too high. In general though, high temperature superconductors like NbSn are important. They have been valuable for making high strength magnets, and for prosaic applications like long distance power transmission. The big magnets are used for submarine hunting, nuclear fusion, and (potentially) for levitation trains. See my essay on Fusion here, it’s what I did my PhD on — in chemical engineering, and levitation trains, potentially, will revolutionize transport.

Robert Buxbaum, December 24, 2015. My company, REB Research, does a lot with hydrogen. Not that we make superconductors, but we make hydrogen generators and purifiers, and I try to keep up with the relevant hydrogen research.

Why are glaciers blue

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i recently returned from a cruse trip to Alaska and, as is typical for such, a highlight of the trip was a visit to Alaska’s glaciers, in our case Hubbard Glacier, Glacier bay, and Mendenhall Glacier. All were blue — bright blue, as were the small icebergs that broke off. Glacier blocks only 2 feet across were bright blue like the glaciers themselves.

Hubbard Glacier, Alaska. Note how blue the ice is

Hubbard Glacier, Alaska. My photo. Note how blue the ice is

What made this interesting/ surprising is that I’ve seen ice sculptures that are 5 foot thick or more, and they are not significantly blue. They have a very slight tinge, but are generally more colorless than glass to my ability to tell. I asked the park rangers why the glaciers were blue, but was given no satisfactory answer. The claim was that glacier ice contained small air bubbles that scattered light the same way that air did. Another park ranger claimed that water is blue by nature, so of course the glaciers were too. The “proof” to this was that the sea was blue. Neither of these seem quite true to me, though there seamed some grains of truth. Sea water, I notice, is sort of blue, but isn’t this shade of blue, certainly not in areas that I’ve lived. Instead, sea water is a rather grayish similar to mud and sea-weeds that I’d expect to find on the sea floor. What’s more, if you look through the relatively clear water of a swimming-pool water to the white-tile bottom, you see only a slight shade of blue-green, even at the 9 foot depth where the light you see has passed through 18 feet of water. This is far more water than an iceberg thickness, and the color is nowhere near as pure blue and the intensity nowhere near as strong.

Plymouth, MI Ice sculpture -- the ice is fairly clear, like swimming pool water

Plymouth, MI Ice sculpture — the ice is fairly clear, like swimming pool water

As for the bubble explanation, it doesn’t seem quite right, either. The bubble size would be non-uniform, with many quite large resulting in a mix of scattered colors — an off white– something seen with the sky of mars. Our earth sky is a purer blue, but this is not because of scattering off of ice-crystals, dust or any other small particles, but rather scattering off the air molecules themselves. The clear blue of glaciers, and of overturned icebergs, suggests (to me) a single-size scattering entity, larger than air molecules, but much smaller than the wavelength of visible light. My preferred entity would be a new compound, a clathrate structure compound, that would be formed from air and ice at high pressures.

An overturned ice-burg is remarkably blue: far bluer than an Ice sculpture. I claim clathrates are the reason.

An overturned ice-burg is remarkably blue: far bluer than an Ice sculpture. I claim clathrates are the reason.

Sea-water forms clathrate compounds with natural gas at high pressures found at great depth. My thought is that similar compounds form between ice and one or more components of air (nitrogen, oxygen, or perhaps argon). Though no compounds of this sort have been quite identified, all these gases are reasonably soluble in water so that suggestion isn’t entirely implausible. The clathrates would be spheres, bigger than air molecules and thus should have more scattering power than the original molecules. An uneven distribution would explain the observation that the blue of glaciers is not uniform, but instead has deeper and lighter blue edges and stripes. Perhaps some parts of the glacier were formed at higher pressures one could expect that these would form more clathrate compounds, and thus more blue. One sees the most intense blue in overturned icebergs — the parts that were under the most pressure.

Robert Buxbaum, October 12, 2015. By the way, some of Alaska’s glaciers are growing and others shrinking. The rangers claimed this was the bad effect of global warming: that the shrinking glaciers should be growing and the growing ones shrinking. They also worried that despite Alaska temperatures reaching 40° below reasonably regularly, it was too warm (for whom?). The lowest recorded temperature in Fairbanks was -66°F in 1961.

Why I don’t like the Iran deal

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Treaties, I suspect, do not exist to create love between nations, but rather to preserve, in mummified form, the love that once existed between leaders. They are useful for display, and as a guide to the future, their main purpose is to allow a politician to help his friends while casting blame on someone else when problems show up. In the case of the US Iran-deal that seems certain to pass in a day or two with only Democratic-party support, and little popular support, I see no love between the nations. On a depressingly regular basis, Iranian leaders promise Death to America, and Death to America’s sometime-ally Israel. Iran has acted on these statements too, funding Hezbollah missiles and suicide bombers, and hanging its dissidents: practices that lead it to become something of a pariah among its neighbors. They also display the sort of nuclear factories and ICBMs (long-range rockets) that could make them much bigger threats if they choose to become bigger threats. The deal just signed by US Secretary of State and his counterpart in Iran (read in full here) seems to preserve this state. It releases to Iran $100,000,000,000 to $150,000,000,000 that it claims it will use against Israel, and Iran claims to have no interest in developing multi-point compression atom bombs. This is a tiny concession given that our atom bomb at Hiroshima was single-point compression, first generation, and killed 90,000 people.

Iranian intercontinental ballistic missile, several stories high, brought out during negotiations. Should easily deliver nuclear weapons far beyond Israel, and even to the USA.

Iranian intercontinental ballistic missile, new for 2015. Should easily deliver warheads far beyond Israel -even to the US.

The deal itself is about 170 pages long and semi-legalistic, but I found it easy to read. The print is large, Iran has few obligations, and the last 100 pages or so are a list companies that will no longer be sanctioned. The treaty asserts that we will defend Iran against attacks including military and cyber attacks, and sabotage –presumably from Israel, but gives no specifics. Also we are to help them with oil, naval, and fusion technology, while leaving them with 1500 kg of 20% enriched U235. That’s enough for quick conversion to 8 to 10 Hiroshima-size A-bombs (atom bombs) containing 25-30 kg each of 90% U235. The argument in favor of the bill seems to be that, by giving Iran the money and technology, and agreeing with their plans, Iran will come to like us. My sense is that this is wishful-thinking, and unlikely (as Jimmy Carter discovered). The unwritten contract isn’t worth the paper it’s written on.

As currently written, Iran does not recognize Israel’s right to exist. To the contrary, John Kerry has stated that a likely consequence is further attacks on Israel. Given Hezbollah’s current military budget is only about $150,000,000 and Hamas’s only about $15,000,000 (virtually all from Iran), we can expect a very significant increase in attacks once the money is released — unless Iran’s leaders prove to be cheapskates or traitors to their own revolution (unlikely). Given our president’s and Ms Clinton’s comments against Zionist racism, I assume that they hope to cow Israel into being less militant and less racist, i.e. less Jewish. I doubt it, but you never know. I also expect an arms race in the middle east to result. As for Iran’s statements that they seek to kill every Jew and wipe out the great satan, the USA: our leaders may come to regret hat they ignore such statements. I guess they hope that none of their friends or relatives will be among those killed.

Kerry on why we give Iran the ability to self-inspect.

Kerry on why we give Iran the ability to self-inspect.

I’d now like to turn to fusion technology, an area I know better than most. Nowhere does the treaty say what Iran will do with nuclear fusion technology, but it specifies we are to provide it, and there seem to be only two possibilities of what they might do with it: (1) Build a controlled fusion reactor like the TFTR at Princeton — a very complex, expensive option, or (2) develop a hydrogen fusion bomb of the sort that vaporized the island of Bimini: an H-bomb. I suspect Iran means to do the latter, while I imagine that, John Kerry is thinking the former. Controlled fusion is very difficult; uncontrolled fusion is a lot easier. With a little thought, you’ll see how to build a decent H-bomb.

My speculation of why Iran would want to make an H-bomb is this: they may not trust their A-bombs to win a war with Israel. As things stand, their A-bomb scientists are unlikely to coax more than 25 to 100 kilotons of explosive power out of each bomb, perhaps double that of Hiroshima and Nagasaki. But our WWII bombs “only” killed 70,000 to 90,000 people each, even with the radiation deaths. Used against Israel, such bombs could level the core of Jerusalem or Tel Aviv. But most Israelis would survive, and they would strike back, hard.

To beat the Israelis, you’d need a Megaton-size, hydrogen bomb. Just one Megaton bomb would vaporize Jerusalem and it’s suburbs, kill a million inhabitants at a shot, level the hills, vaporize the artifacts in the jewish museum, and destroy anything we now associate with Israel. If Iran did that, while retaining a second bomb for Tel-Aviv, it is quite possible Israel would surrender. As for our aim, perhaps we hope Iran will attack Israel and leave us alone. Very bright people pushed for WWI on hopes like this.

Robert E. Buxbaum. September 9, 2015. Here’s a thought about why peace in the middle east is so hard to achieve,

It’s rocket science

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Here are six or so rocket science insights, some simple, some advanced. It’s a fun area of engineering that touches many areas of science and politics. Besides, some people seem to think I’m a rocket scientist.

A basic question I get asked by kids is how a rocket goes up. My answer is it does not go up. That’s mostly an illusion. The majority of the rocket — the fuel — goes down, and only the light shell goes up. People imagine they are seeing the rocket go up. Taken as a whole, fuel and shell, they both go down at 1 G: 9.8 m/s2, 32 ft/sec2.

Because 1 G ofupward acceleration is always lost to gravity, you need more thrust from the rocket engine than the weight of rocket and fuel. This can be difficult at the beginning when the rocket is heaviest. If your engine provides less thrust than the weight of your rocket, your rocket sits on the launch pad, burning. If your thrust is merely twice the weight of the rocket, you waste half of your fuel doing nothing useful, just fighting gravity. The upward acceleration you’ll see, a = F/m -1G where F is the force of the engine, and m is the mass of the rocket shell + whatever fuel is in it. 1G = 9.8m/s is the upward acceleration lost to gravity.  For model rocketry, you want to design a rocket engine so that the upward acceleration, a, is in the range 5-10 G. This range avoids wasting lots of fuel without requiring you to build the rocket too sturdy.

For NASA moon rockets, a = 0.2G approximately at liftoff increasing as fuel was used. The Saturn V rose, rather majestically, into the sky with a rocket structure that had to be only strong enough to support 1.2 times the rocket weight. Higher initial accelerations would have required more structure and bigger engines. As it was the Saturn V was the size of a skyscraper. You want the structure to be light so that the majority of weight is fuel. What makes it tricky is that the acceleration weight has to sit on an engine that gimbals (slants) and runs really hot, about 3000°C. Most engineering projects have fewer constraints than this, and are thus “not rocket science.”

Basic force balance on a rocket going up.

Basic force balance on a rocket going up.

A space rocket has to reach very high, orbital speed if the rocket is to stay up indefinitely, or nearly orbital speed for long-range, military uses. You can calculate the orbital speed by balancing the acceleration of gravity, 9.8 m/s2, against the orbital acceleration of going around the earth, a sphere of 40,000 km in circumference (that’s how the meter was defined). Orbital acceleration, a = v2/r, and r = 40,000,000 m/2π = 6,366,000m. Thus, the speed you need to stay up indefinitely is v=√(6,366,000 x 9.8) = 7900 m/s = 17,800 mph. That’s roughly Mach 35, or 35 times the speed of sound at sea level, (343 m/s). You need some altitude too, just to keep air friction from killing you, but for most missions, the main thing you need is velocity, kinetic energy, not potential energy, as I’ll show below. If your speed exceeds 17,800 m/s, you go higher up, but the stable orbital velocity is lower. The gravity force is lower higher up, and the radius to the earth higher too, but you’re balancing this lower gravity force against v2/r, so v2 has to be reduced to stay stable high up, but higher to get there. This all makes docking space-ships tricky, as I’ll explain also. Rockets are the only way practical to reach Mach 35 or anything near it. No current cannon or gun gets close.

Kinetic energy is a lot more important than potential energy for sending an object into orbit. To get a sense of the comparison, consider a one kg mass at orbital speed, 7900 m/s, and 200 km altitude. For these conditions, the kinetic energy, 1/2mv2 is 31,205 kJ, while the potential energy, mgh, is only 1,960 kJ . The potential energy is thus only 1/16 the kinetic energy.

Not that it’s easy to reach 200 miles altitude, but you can do it with a sophisticated cannon. The Germans did it with “simple”, one stage, V2-style rockets. To reach orbit, you generally need multiple stages. As a way to see this, consider that the energy content of gasoline + oxygen is about 10.5 MJ/kg (10,500 kJ/kg); this is only 1/3 of the kinetic energy of the orbital rocket, but it’s 5 times the potential energy. A fairly efficient gasoline + oxygen powered cannon could not provide orbital kinetic energy since the bullet can move no faster than the explosive vapor. In a rocket this is not a constraint since most of the mass is ejected.

A shell fired at a 45° angle that reaches 200 km altitude would go about 800 km — the distance between North Korea and Japan, or between Iran and Israel. That would require twice as much energy as a shell fired straight up, about 4000 kJ/kg. This is still within the range for a (very large) cannon or a single-stage rocket. For Russia or China to hit the US would take much more: orbital, or near orbital rocketry. To reach the moon, you need more total energy, but less kinetic energy. Moon rockets have taken the approach of first going into orbit, and only later going on. While most of the kinetic energy isn’t lost, it’s likely not the best trajectory in terms of energy use.

The force produced by a rocket is equal to the rate of mass shot out times its velocity. F = ∆(mv). To get a lot of force for each bit of fuel, you want the gas exit velocity to be as fast as possible. A typical maximum is about 2,500 m/s. Mach 10, for a gasoline – oxygen engine. The acceleration of the rocket itself is this ∆mv force divided by the total remaining mass in the rocket (rocket shell plus remaining fuel) minus 1 (gravity). Thus, if the exhaust from a rocket leaves at 2,500 m/s, and you want the rocket to accelerate upward at an average of 10 G, you must exhaust fast enough to develop 10 G, 98 m/s2. The rate of mass exhaust is the average mass of the rocket times 98/2500 = .0392/second. That is, about 3.92% of the rocket mass must be ejected each second. Assuming that the fuel for your first stage engine is less than 80% of the total mass, the first stage will flare-out in about 20 seconds. Typically, the acceleration at the end of the 20 burn is much greater than at the beginning since the rocket gets lighter as fuel is burnt. This was the case with the Apollo missions. The Saturn V started up at 0.5G but reached a maximum of 4G by the time most of the fuel was used.

If you have a good math background, you can develop a differential equation for the relation between fuel consumption and altitude or final speed. This is readily done if you know calculous, or reasonably done if you use differential methods. By either method, it turns out that, for no air friction or gravity resistance, you will reach the same speed as the exhaust when 64% of the rocket mass is exhausted. In the real world, your rocket will have to exhaust 75 or 80% of its mass as first stage fuel to reach a final speed of 2,500 m/s. This is less than 1/3 orbital speed, and reaching it requires that the rest of your rocket mass: the engine, 2nd stage, payload, and any spare fuel to handle descent (Elon Musk’s approach) must weigh less than 20-25% of the original weight of the rocket on the launch pad. This gasoline and oxygen is expensive, but not horribly so if you can reuse the rocket; that’s the motivation for NASA’s and SpaceX’s work on reusable rockets. Most orbital rocket designs require three stages to accelerate to the 7900 m/s orbital speed calculated above. The second stage is dropped from high altitude and almost invariably lost. If you can set-up and solve the differential equation above, a career in science may be for you.

Now, you might wonder about the exhaust speed I’ve been using, 2500 m/s. You’ll typically want a speed at lest this high as it’s associated with a high value of thrust-seconds per weight of fuel. Thrust seconds pre weight is called specific impulse, SI, SI = lb-seconds of thrust/lb of fuel. This approximately equals speed of exhaust (m/s) divided by 9.8 m/s2. For a high molecular weight burn it’s not easy to reach gas speed much above 2500, or values of SI much above 250, but you can get high thrust since thrust is related to momentum transfer. High thrust is why US and Russian engines typically use gasoline + oxygen. The heat of combustion of gasoline is 42 MJ/kg, but burning a kg of gasoline requires roughly 2.5 kg of oxygen. Thus, for a rocket fueled by gasoline + oxygen, the heat of combustion per kg is 42/3.5 = 12,000,000 J/kg. A typical rocket engine is 30% efficient (V2 efficiency was lower, Saturn V higher). Per corrected unit of fuel+oxygen mass, 1/2 v2 = .3 x 12,000,000; v =√7,200,000 = 2680 m/s. Adding some mass for the engine and fuel tanks, the specific impulse for this engine will be, about 250 s. This is fairly typical. Higher exhaust speeds have been achieved with hydrogen fuel, it has a higher combustion energy per weight. It is also possible to increase the engine efficiency; the Saturn V, stage 2 efficiency was nearly 50%, but the thrust was low. The sources of inefficiency include inefficiencies in compression, incomplete combustion, friction flows in the engine, and back-pressure of the atmosphere. If you can make a reliable, high efficiency engine with good lift, a career in engineering may be for you. A yet bigger challenge is doing this at a reasonable cost.

At an average acceleration of 5G = 49 m/s2 and a first stage that reaches 2500 m/s, you’ll find that the first stage burns out after 51 seconds. If the rocket were going straight up (bad idea), you’d find you are at an altitude of about 63.7 km. A better idea would be an average trajectory of 30°, leaving you at an altitude of 32 km or so. At that altitude you can expect to have far less air friction, and you can expect the second stage engine to be more efficient. It seems to me, you may want to wait another 10 seconds before firing the second stage: you’ll be 12 km higher up and it seems to me that the benefit of this will be significant. I notice that space launches wait a few seconds before firing their second stage.

As a final bit, I’d mentioned that docking a rocket with a space station is difficult, in part, because docking requires an increase in angular speed, w, but this generally goes along with a decrease in altitude; a counter-intuitive outcome. Setting the acceleration due to gravity equal to the angular acceleration, we find GM/r2 = w2r, where G is the gravitational constant, and M is the mass or the earth. Rearranging, we find that w2  = GM/r3. For high angular speed, you need small r: a low altitude. When we first went to dock a space-ship, in the early 60s, we had not realized this. When the astronauts fired the engines to dock, they found that they’d accelerate in velocity, but not in angular speed: v = wr. The faster they went, the higher up they went, but the lower the angular speed got: the fewer the orbits per day. Eventually they realized that, to dock with another ship or a space-station that is in front of you, you do not accelerate, but decelerate. When you decelerate you lose altitude and gain angular speed: you catch up with the station, but at a lower altitude. Your next step is to angle your ship near-radially to the earth, and accelerate by firing engines to the side till you dock. Like much of orbital rocketry, it’s simple, but not intuitive or easy.

Robert Buxbaum, August 12, 2015. A cannon that could reach from North Korea to Japan, say, would have to be on the order of 10 km long, running along the slope of a mountain. Even at that length, the shell would have to fire at 450 G, or so, and reach a speed about 3000 m/s, or 1/3 orbital.

No need to conserve energy

Earth day, energy conservation stamp from the 1970s

Energy conservation stamp from the early 70s

I’m reminded that one of the major ideas of Earth Day, energy conservation, is completely unnecessary: Energy is always conserved. It’s entropy that needs to be conserved.

The entropy of the universe increases for any process that occurs, for any process that you can make occur, and for any part of any process. While some parts of processes are very efficient in themselves, they are always entropy generators when considered on a global scale. Entropy is the arrow of time: if entropy ever goes backward, time has reversed.

A thought I’ve had on how do you might conserve entropy: grow trees and use them for building materials, or convert them to gasoline, or just burn them for power. Under ideal conditions, photosynthesis is about 30% efficient at converting photon-energy to glucose. (photons + CO2 + water –> glucose + O2). This would be nearly same energy conversion efficiency as solar cells if not for the energy the plant uses to live. But solar cells have inefficiency issues of their own, and as a result the land use per power is about the same. And it’s a lot easier to grow a tree and dispose of forest waste than it is to make a solar cell and dispose of used coated glass and broken electric components. Just some Earth Day thoughts from Robert E. Buxbaum. April 24, 2015