Category Archives: Hydrogen

The shutdown will drag; we will win

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In theory, both US parties are committed to a balanced budget. Both claim they’ll tax as much as they spend, and we’ll pay our debts. In practice, both parties overspend wildly, year after year. The growth in non-defense spending (pork) is particularly egregious, see graph. For fiscal 2024, the 12 month period ending Sept. 30 2024, the government spent $6.75 trillion ($6750 billion), over 20% of GDP. We took in, in taxes $4.92 Trillion ($4,920 Billion). The difference, $1830 billion, was added to the national debt, already at $34 trillion, pushing it to $36 trillion, about 100% of our GDP. The interest cost alone is $1.22 trillion per year. That’s 1/4 of our tax income.

Trump campaigned claiming he was going to balance the budget, but he has not. There were some attempts via DOGE, saving about $214 billion, but the DOGE boys were outed, attacked, and gave up. And now the Democrats have forced a shutdown, using their power to prevent additional borrowing. This leaves Trump with a tough choice, either balance the budget or accept their spending demands. The expectation is that Trump will fold: there is no way he can find $1830 billion/year. Otherwise, many of the governments 4.2 million workers will go without pay, and many important services will stop.

So far, three weeks in, Trump seems fairly successful at keeping things running while (apparently) trying to balance the budget. Even if he fails, as seems likely, we will benefit from the attempt, I think.

Some government services are guaranteed to continue despite the shutdown: Social security and the post office because they are funded separately. Similarly, the patent office, the ports, and the airports. In the past some had to shut, but Trump has raised fees so they remain open and operating.

Essential workers, including customs agents and air traffic controllers are expected to continue working with many going unpaid. Trump committed to paying active duty military and the WIC food program using money raised by new, 2025 tariffs. Tariffs are currently bringing in ~$300 Billion/ year, and so far tariffs mostly don’t affect ordinary folks, but help return manufacturing to the US. Some time soon we’ll have to pay the 800,000 necessary government workers, and also 750,000 non-necessary workers: half the Dept. of Education, most of NASA and Energy… These people are not really useless, but they are not doing anything essential to the day-to-day operation of the country.

Trump seems committed to removing many non-necessary workers. He fired 4200, bought out another 25,000 earlier this year, and has issued pre-termination notices to 75,000. A federal judge has blocked all firings as unlawful, but my sense is they are lawful and mostly beneficial. If you can’t fire non-working, un-necessary workers you can’t afford to pay, who can you fire?

I suspect the shutdown will last well into November, well past the election, and that more folks will be fired or bought out. The key November crossroads will be food stamps, SNAP. These benefits are scheduled to end November 1 baring an end to the shutdown. Normally the bill is $110 billion/year, but Trump has eliminated benefits for illegal aliens and asylum seekers, and has instituted a tougher work requirement. Democrats seem certain that Trump won’t find the money, and that he will fold. For the 11th time they scotched a bill to fund this and reopen the government. I suspect that, at the last minute, Trump will find savings, or left-over funds and will keep SNAP funded through November.

Among the new savings, Trump ended the EV subsidy last month, saving about $7.5 billion/year ($7500 x 1 million EVs), and has negotiated some reductions in drug costs. He also increased the tariff on some Chinese and Canadian goods appropriate for rectifying trade imbalance, it’s been blocked by a federal judge. He’s also cancelled some rail work and research, saving $28 billion, and cancelled $20 billion for hydrogen hubs, and 83% of USAID. Also two navy ships that were years behind schedule and billions over budget. We need the ships, but don’t have the money. So far, this saved enough to pay all military servicemen.

Beyond this, I hope he cuts Biden’s high speed rail plans: $550 Billion for fast trains, Chicago to Seattle, Detroit to Toledo, San Francisco to LA, etc. The investment is $1,500 per person in the US. The eager thinkers overseeing this would never invest their own money, but are happy to invest everyone else’s. I also hope to see the end of NASA’s SLS rocket to the moon, nice but far more expensive than Falcon. We could also cancel some F35s ($0.1 Billion each to buy, and far more to maintain). Musk suggested replacing them with drones. I don’t know that these savings are enough. I don’t know how long we can continue, but each day shut, we move closer to a balanced budget, and that’s a good thing.

Robert Buxbaum, October 21, 2025

Purifier delivered to customer for muon-catalyzed fusion

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I got my PhD in the engineering of nuclear fusion reactors (Princeton 1982). The most common version of these reactors use magnetic confinement. Rare isotopes of hydrogen are held in a magnetic bottle at 300 million °C (30 KeV), reacting to produce helium, useful energy, and a neutron. The magnetic bottle and high temperatures are necessary to overcome the repulsion between the hydrogen atoms at the distances necessary for nuclear fusion.

A customer of ours is building a different type of fusion reactor, without high temperatures or a magnetic bottle. They replace a few electrons of the hydrogen with muons — particles that are like electrons, but weigh about 207 times more. Hydrogen fusion is quickly catalyzed, as described in an earlier post. The muons recirculate to catalyze more until they decay or are trapped by an impurity, often helium. 

Our company, REB Research, just shipped a specially made, hydrogen purifier tailored to remove the impurities in this process. Another aspect of the purifier design is that it minimizes radioactive tritium leakage, something that happens when hydrogen (tritium) diffuses through metals. We wish them all success, and wish success to our other fusion customers as well. 

Robert Buxbaum, September 30, 2025

A customer gets contract for moon mining He3

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A customer of ours, Interlune, just got a contract for any He3 they can bring back after mining it on the moon. He3 is a rare isotope of helium, used in cryogenic refrigeration, and (some) nuclear fusion reactors. It’s more common on the moon than on earth, and is expensive enough that it may make sense to mine it on the moon and bring it back. The US government has agreed to buy all of interlune’s lunar, He3 for the next ten years, ‘at the market rate.’

Our company, REB Research, comes into this because, lunar helium is found mixed with hydrogen species including HD. For prospecting, this is a problem in that He3 is easily confused with HD; they need to remove the HD to be able to determine how much He3 is in the ore. We make hydrogen extraction equipment, and were happy to supply them. It’s not a large part of our business, but we’re going to the moon because it’s ‘out there.’

Robert Buxbaum, May 29, 2025. Our site looks new; we’re moving to WordPress.

Germany’s hydrogen trains and boats almost make sense

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Germany’s green transition is a disaster. Twenty years ago, Germany had 23 nuclear power plants that generated 30% of the country’s electricity cleanly, cheaply, and reliably. These plants have all been shut by the government as part of a commitment to clean energy. What could be cleaner? Germany has switched to a mix of wind and solar, plus a significant shift to coal power. Wind and solar use a lot of land compared to nuclear, and they break down leaving fields of debris. There is now a lack of electricity to power homes and industries, and what power there is, is unreliable, due to the many dark windless days in Germany.

The lack of reliable electricity is crippling German industry now that Russian gas has been cut off. In this environment, why would the Germans order special trains and boats that burn, hydrogen that’s made from electricity and natural gas? My understanding of the reason is that, Germany sometimes has too much wind power and nothing to do with it. They plan to store this excess by making hydrogen that they can use to power their trains and boats. The cost is high, and the efficiency is poor, but the electricity is free.

Hydrogen is not as compact a fuel as gasoline, nor is it as cheap as electricity, but it’s cleaner than gas, and in some ways it’s better than battery-stored electricity. While hydrogen takes a lot of storage space relative to gasoline, high pressure helps, and the storage is cheaper than with batteries. Also, hydrogen fuel is transferred faster than electric fuels. Trains and ships are chosen for hydrogen because they are good at carrying bulky items. The transition to hydrogen is relatively straightforward with trains, since many are already powered by electricity. Hydrogen fuel cells can make the electricity on board (in theory), while avoiding the need for expensive overhead wires. The idea sort-of makes sense.

Germany’s first hydrogen train. cancelled after 1 year of poor operating.

The first German train to use hydrogen powered them with fuel cells that generated electricity. It began service in October 2022, but the fuel cells proved unreliable. Service ended one year later, October 2023, replaced by polluting diesel (see here). The Hannover line plans to replace these with battery-powered trains over the next few years. There are also plans for a hydrogen-powered ferry, but it is not clear why the ferry should prove more reliable than the train, or cheaper.

San Francisco’s hydrogen-powered ferry, $30 million, 15 knots top speed, 75 passengers, no cars. Long delayed.

In the US, the Biden administration has paid, so far, $30 million for a hydrogen ferry in San Francisco. It’s two years behind schedule and over cost, taking only 75 passengers and no cars at 15 knots, 17mph. In the US, and likely in Germany, most of the hydrogen will be made from natural gas. A better solution, I think would be to power the ferris and trains by natural gas and to store the excess electricity in land-based batteries or as land-based hydrogen for land-based fuel cells.

Germany is committed to electric trains, though, and hydrogen provides a route to power these trains with excess electricity. German customers take the train, in part, because they like them, and in part because German politicians have banned short-hop planes on competing routes, and subsidized electric trains. Yet another option to balance times of excess solar and wind power would be to subsidize electric cars, or at least allow theirs owners to trade electricity: to buy electricity when it’s cheap and resell it to the grid when demand and prices are high.

Robert Buxbaum, June 8, 2024

How I size heat exchangers

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Heat exchange is a key part of most chemical process designs. Heat exchangers save money because they’re generally cheaper than heaters and the continuing cost of fuel or electricity to run the heaters. They also usually provide free, fast cooling for the product; often the product is made hot, and needs to be cooled. Hot products are usually undesirable. Free, fast cooling is good.

So how do you design a heat exchanger? A common design is to weld the right amount of tubes inside a shell, so it looks like the drawing below. The the hot fluid might be made to go through the tubes, and the cold in the shell, as shown, or the hot can flow through the shell. In either case, the flows are usually in the opposite direction so there is a hot end and a cold end as shown. In this essay, I’d like to discuss how I design our counter current heat exchangers beginning a common case (for us) where the two flows have the same thermal inertia, e.g. the same mass flow rates and the same heat capacities. That’s the situation with our hydrogen purifiers: impure hydrogen goes in cold, and is heated to 400°C for purification. Virtually all of this hot hydrogen exits the purifier in the “pure out” stream and needs to be cooled to room temperature or nearly.

Typical shell and tube heat exchanger design, Black Hills inc.

For our typical designs the hot flows in one direction, and an equal cold flow is opposite, I will show the temperature difference is constant all along the heat exchanger. As a first pass rule of thumb, I design so that this constant temperature difference is 30°C. That is ∆THX =~ 30°C at every point along the heat exchanger. More specifically, in our Mr Hydrogen® purifiers, the impure, feed hydrogen enters at 20°C typically, and is heated by the heat exchanger to 370°C. That is 30°C cooler than the final process temperature. The hydrogen must be heated this last 30°C with electricity. After purification, the hot, pure hydrogen, at 400°C, enters the heat exchanger leaving at 30°C above the input temperature, that is at 50°C. It’s hot, but not scalding. The last 30°C of cooling is done with air blown by a fan.

The power demand of the external heat source, the electric heater, is calculated as: Wheater = flow (mols/second)*heat capacity (J/°C – mol)* (∆Theater= ∆THX = 30°C).

The smaller the value of ∆THX, the less electric draw you need for steady state operation, but the more you have to pay for the heat exchanger. For small flows, I often use a higher value of ∆THX = 30°C, and for large flows smaller, but 30°C is a good place to start.

Now to size the heat exchanger. Because the flow rate of hot fluid (purified hydrogen) is virtually the same as for cold fluid (impure hydrogen), the heat capacity per mol of product coming out is the same as for mol of feed going in. Since enthalpy change equals heat capacity time temperature change, ∆H= Cp∆T, with effectiveCp the same for both fluids, and any rise in H in the cool fluid coming at the hot fluid, we can draw a temperature vs enthalpy diagram that will look like this:

The heat exchanger heats the feed from 20°C to 370°C. ∆T = 350°C. It also cools the product 350°C, that is from 400 to 50°C. In each case the enthalpy exchanged per mol of feed (or product is ∆H= Cp*∆T = 7*350 =2450 calories.

Since most heaters work in Watts, not calories, at some point it’s worthwhile to switch to Watts. 1 Cal = 4.174 J, 1 Cal/sec = 4.174 W. I tend to do calculations in mixed units (English and SI) because the heat capacity per mole of most things are simple numbers in English units. Cp (water) for example = 1 cal/g = 18 cal/mol. Cp (hydrogen) = 7 cal/mol. In SI units, the heat rate, WHX, is:

WHX = flow (mols/second)*heat capacity per mol (J/°C – mol)* ∆Tin-out (350°C).

The flow rate in mols per second is the flow rate in slpm divided by 22.4 x 60. Since the driving force for transfer is 30°C, the area of the heat exchanger is WHX times the resistance divided by ∆THX:

A = WHX * R / 30°C.

Here, R is the average resistance to heat transfer, m2*∆T/Watt. It equals the sum of all the resistances, essentially the sum of the resistance of the steel of the heat exchanger plus that of the two gas phases:

R= δm/km + h1+ h2

Here, δm is the thickness of the metal, km is the thermal conductivity of the metal, and h1 and h2 are the gas-phase heat transfer parameters in the feed and product flow respectively. You can often estimate these as δ1/k1 and δ2/k2 respectively, with k1 and k2 as the thermal conductivity of the feed and product, both hydrogen in my case. As for, δ, the effective gas-layer thickness, I generally estimate this as 1/3 the thickness of the flow channel, for example:

h1 = δ1/k1 = 1/3 D1/k1.

Because δ is smaller the smaller the diameter of the tubes, h is smaller too. Also small tubes tend to be cheaper than big ones, and more compact. I thus prefer to use small diameter tubes and small diameter gaps. in my heat exchangers, the tubes are often 1/4″ or bigger, but the gap sizes are targeted to 1/8″ or less. If the gap size gets too low, you get excessive pressure drops and non-uniform flow, so you have to check that the pressure drop isn’t too large. I tend to stick to normal tube sizes, and tweak the design a few times within those parameters, considering customer needs. Only after the numbers look good to my aesthetics, do I make the product. Aesthetics plays a role here: you have to have a sense of what a well-designed exchanger should look like.

The above calculations are fine for the simple case where ∆THX is constant. But what happens if it is not. Let’s say the feed is impure, so some hot product has to be vented, leaving les hot fluid in the heat exchanger than feed. I show this in the plot at right for the case of 14% impurities. Sine there is no phase change, the lines are still straight, but they are no longer parallel. Because more thermal mass enters than leaves, the hot gas is cooled completely, that is to 50°C, 30°C above room temperature, but the cool gas is heated at only 7/8 the rate that the hot gas is cooled. The hot gas gives off 2450 cal as before, but this is now only enough to heat the cold fluid by 2450/8 = 306.5°. The cool gas thus leave the heat exchanger at 20°C+ 306.8° = 326.5°C.

The simple way to size the heat exchanger now is to use an average value for ∆THX. In the diagram, ∆THX is seen to vary between 30°C at the entrance and and 97.5°C at the exit. As a conservative average, I’ll assume that ∆THX = 40°C, though 50 to 60°C might be more accurate. This results in a small heat exchanger design that’s 3/4 the size of before, and is still overdesigned by 25%. There is no great down-side to this overdesign. With over-design, the hot fluid leaves at a lower ∆THX, that is, at a temperature below 50°C. The cold fluid will be heated to a bit more than to the 326.5°C predicted, perhaps to 330°C. We save more energy, and waste a bit on materials cost. There is a “correct approach”, of course, and it involves the use of calculous. A = ∫dA = ∫R/∆THX dWHX using an analytic function for ∆THX as a function of WHX. Calculating this way takes lots of time for little benefit. My time is worth more than a few ounces of metal.

The only times that I do the correct analysis is with flame boilers, with major mismatches between the hot and cold flows, or when the government requires calculations. Otherwise, I make an H Vs T diagram and account for the fact that ∆T varies with H is by averaging. I doubt most people do any more than that. It’s not like ∆THX = 30°C is etched in stone somewhere, either, it’s a rule of thumb, nothing more. It’s there to make your life easier, not to be worshiped.

Robert Buxbaum June 3, 2024

Ferries make more sense than fast new trains.

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Per pound mile of material, the transport cost by ship is 1/4 as much as by train, and about 1/8 as much as by truck. Ships are slower, it is true, but they can go where trucks and trains can not. They cross rivers and lakes at ease and can haul weighty freight with ease. I think America could use many more ferries, particularly drive-on, fast ferries. I don’t think we need new fast rail lines, because air travel will always be faster and cheaper. The Biden administration thinks otherwise, and spends accordingly.

Amtrak gets $30 Billion for train infrastructure this year, basically nothing for ferries.

The Biden administration’s infrastructure bill, $1.2 Trillion dollars total, provides $30 Billion this year for new train lines, but includes less than 1% as much for ferries, $220 million, plus $1B for air travel. I think it’s a scandal. The new, fast train lines are shown on the map, above. Among them is a speed upgrade to the “Empire Builder” train running between Chicago and Seattle by way of Milwaukee. I don’t think this will pay off — the few people who take this train, takes it for the scenery, I think, and for the experience, not to get somewhere fast.

There is money for a new line between Cleveland and Detroit, and for completion of the long-delayed, and cost-over-run prone line between LA and San Francisco. Assuming these are built, I expect even lower ridership since the scenery isn’t that great. Even assuming no delays (and there are always delays), 110 mph is vastly slower than flying, and typically more expensive and inconvenient. Driving is yet slower, but when you drive, you arrive with your car. With a train or plane, you need car rental, typically.

New Acela train, 150 mph max. 1/4 as fast as flying at the same price.

Drive-on ferries provide a unique advantage in that you get there with your car, often much faster than you would with by driving or by train. Consider Muskegon to Milwaukee (across the lake), or Muskegon to Chicago to Milwaukee, (along the lake). Cleveland to Canada, or Detroit to Cleveland. No land would have to be purchased and no new track would have to be laid and maintained. You’d arrive, rested and fed (they typically sell food on a ferry), with your car.

There’s a wonderful song, “City of New Orleans”, sung here by Arlo Guthrie describing a ride on the historic train of that name on a trip from Chicago to New Orleans, 934 miles in about one day. Including stops but not including delays, the average speed is 48 mph, and there are always delays. On board are, according to the song, “15 restless riders, 3 conductors, and 25 sacks of mail.” The ticket price currently is $200, one way, or about as much as a plane ticket. The line loses money. I’ve argued, here, for more mail use to hep make this profitable, but the trip isn’t that attractive as a way to get somewhere, it’s more of a land-cruise. The line is scheduled for an upgrade this year, but even if upgraded to 100 mph (14 hours to New Orleans including stops?) it’s still going to be far slower than air travel, and likely more expensive, and you still have to park your car before you get on, and then rent another when you get off. And will riders like it more? I doubt it, and doubt the speed upgrade will be to 100 mph.

Lake Express, 30 mph across Lake Michigan

Ferry travel tends to cost less than train or plane travel because water traffic is high volume per trip with few conductors per passenger. At present, there are only two ferryboats traveling across Lake Michigan, between Michigan and Wisconsin, Milwaulkee to Muskegon. They are privately owned, and presumably make money. The faster is the Lake Express, 30 mph. It crosses the lake in 2.5 hours. Passenger tickets cost $52 one way, or $118 for passenger and car. That’s less than the price of an Amtrak ticket or a flight. I think a third boat would make sense and that more lines would be welcome too. Perhaps Grand Haven to Racine or Chicago.

Route of the Lake Express. I’d like to see more like this; St. Joseph to Milwaukee say, and along Lake Erie.

Currently, there are no ferries across Lake Erie. Nor are there any along Lake Erie, or even across Lake St. Clair, or along the Detroit River, Detroit to Toledo or Toledo to Cleveland. These lines would need dock facilities, but they would have ridership, I think. New York’s Staten Island ferry has good ridership, 35,000 riders on a typical day, plus cars and trucks. In charge are roughly 120 engineers, captains and mates, one employee for every 300 passengers or so. By comparison, Amtrak runs 300 trains that carry a total of 87,000 passengers on an average day, mostly on the east coast. These 300 trains are run by 17,100 employees as of fiscal year 2021, one employee for every 4 passengers. Even at the slow speeds of our trains the cost is far higher per passenger and per passenger mile.

The Staten Island ferry is slow, 18.5 mph, but folks don’t seem to mind. The trip takes 20 minutes, about half as long as most people’s trips on Amtrak. There are also private ferry lines in NY, many of these on longer trips. People would take ferries for day-long trips along our rivers, I think. Fast ferries would be nice, 40 mph or more, but I think even slow ferries would have ridership and would make money. A sea cruise is better than a land cruise, especially if you can have a cabin. On the coal-steam powered, Badger, you can rent a state-room to spend the night in comfort. Truckers seem to like that they cover ground during their mandatory rest hours. The advantage is maximized, I think, for ferry trips that take 12 hours or so, 250 to 350 miles. That’s Pittsburgh to Cincinnatti or Chicago to Memphis.

New York’s Staten Island ferry leaves every 15 minutes during rush hour. Three different sizes of boat are used. The largest carry over 5000 passengers and 100 cars and trucks at a crossing.

A low risk way to promote ferry traffic between the US and Canada would be to negotiate bilateral exemption to The Jones Act and its Canadian equivalent. Currently, we allow only US ships with US crews for US travel within the US.* Cabotage it’s called, and it applies to planes as well, with exemptions. Canada has similar laws and exemptions. A sensible agreement would allow in-country and cross-country travel on both Canadian and US ships, with Canadian and/or US crew. In one stoke, ridership would double, and many lines would be profitable.

Politicians of a certain stripe support trains because they look futuristic and allow money to go to friends. Europeans brag of their fast trains, but they all lose money, and Europe had to ban many short hop flights to help their trains compete. Without this, Europeans would fly. There is room to help a friend with a new ferry, but not as much as when you buy land and lay track. We could try to lead in fancy ferries going 40 mph or faster, providing good docks, and some insurance. Investors would take little risk since a ferry route can be moved**. Don’t try that with a train.

In Detroit we have a close up of train mismanagement involving the “People Mover.” It has no ridership to speak of. Our politicians then added “The Q line” to connect to it. People avoid both lines. I think people would use a ferry along the Detroit river, though, St. Claire to Wyandotte, Detroit, Toledo — and to Cleveland or Buffalo. Our lakes and rivers are near-empty superhighways. Let’s use them.

Robert Buxbaum, January 2, 2024. *The US air cabotage act (49 U.S.C. 41703) prohibits the transportation of persons, property, or mail for compensation or hire between points of the U.S. in a foreign civil aircraft. We’ve managed exemptions, though, e.g. for US air traffic with Airbus and Embraer planes. We can do the same with ferries.

** I notice that it was New York’s ferries, and their captains, that rescued the people on Sullenberger’s plane when it went down in the Hudson River — added Jan. 6.

Hydrogenation, how we’ve already entered the hydrogen economy

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The hydrogen economy is generally thought to come in some distant future, where your car (and perhaps your home) runs on hydrogen, and the hydrogen, presumably, is made by clean nuclear or renewable solar or wind power. This is understood to be better than the current state of things where your car runs on dirty gasoline, and your home runs on coal or gas, except when the sun is shining bright and the wind is blowing hard. Our homes and cars can not run on solar or wind alone, although solar cells have become quite cheap, because solar power is only available in the daytime, basically for 6 hours, from about 9AM to 3PM. Hydrogen has been proposed as a good way to store solar and wind energy that you can’t use, but it’s not easy to store hydrogen — or is it? I’d like to suggest that, to a decent extent, we already store green hydrogen and use it to run our trucks. We store this hydrogen in the form of Diesel fuel, so you don’t realize it’s hydrogen.

Much of the oil in the United States these days comes from tar sands and shale. It doesn’t flow well at room temperature, and is too heavy and gooey for normal use. We could distill this crude oil and use only the light parts, but that would involve throwing away a huge majority of the oil. Instead we steam reform it to gasoline, ethylene and other products. The reaction is something like this, presuming an input feed of naphtha, C10H8:

C10H8 + 2 H2O –> C7H8 + C2H4 + CO2.

The C2H4 component is ethylene. We use it to make plastics. The C7H8 is called toluene. It is a component of high octane gasoline (octane rating about 114). The inventor of the process, Eugene Jules Houdry claimed to have won WWII for the allies because his secret process (Houdryflow catalytic cracking) allowed high production of lots of gasoline of very high octane, giving US and British planes and trucks higher mpg than the Germans or Japanese had. It was a great money maker, but companies can make even more by adding hydrogen.

Schematic of the hydrocracking process, from the US energy information agency

Over the last 2-3 decades, refineries have been adding catalytic hydrogenation processes. These convert high octane aromatic products, like toluene to low -octane diesel and jet fuel. These products sell for more. Aromatic toluene is exposed to hydrogen at about 500°C and 300 psi (20 bar) to produce heptane, an excellent diesel fuel with about 7% more energy content than toluene per gallon.

C7H8 + 4H2 –> C7H16.

Diesel fuel sell for about 20% more than gasoline per gallon, in part because of the higher energy content, and because Diesel engines are more efficient than gas engines. What’s more, toluene expands as it’s converted to heptane. One gallon of toluene converts to 1.16 gallons of heptane. As a result hydrogenation adds about 40% to the sales price per molecule. Refineries have found that they can make significant money this way if they can buy cheap hydrogen. Over the last few years, several refineries in Norway and Texas (high sun and wind areas) have added hydrogenators along with electrolysis units to produce the cheap hydrogen when no one needs the unwanted electricity generated when supply exceeds demand. Here is an analysis of the thermodynamics of this type of hydrogen generation.

Robert Buxbaum, May 11, 2023

Rotating sail ships and why your curve ball doesn’t curve.

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The Flettner-sail ship, Barbara, 1926.

Sailing ships are wonderfully economic and non-polluting. They have unlimited range because they use virtually no fuel, but they tend to be slow, about 5-12 knots, about half as fast as Diesel-powered ships, and they can be stranded for weeks if the wind dies. Classic sailing ships also require a lot of manpower: many skilled sailors to adjust the sails. What’s wanted is an easily manned, economical, hybrid ship: one that’s powered by Diesel when the wind is light, and by a simple sail system when the wind blows. Anton Flettner invented an easily manned sail and built two ships with it. The Barbara above used a 530 hp Diesel and got additional thrust, about an additional 500 hp worth, from three, rotating, cylindrical sails. The rotating sales produced thrust via the same, Magnus force that makes a curve ball curve. Barbara went at 9 knots without the wind, or about 12.5 knots when the wind blew. Einstein thought it one of the most brilliant ideas he’d seen.

Force diagram of Flettner rotor (Lele & Rao, 2017)

The source of the force can be understood with help of the figure at left and the graph below. When a simple cylinder sits in the wind, with no spin, α=0, the wind force is essentially drag, and is 1/2 the wind speed squared, times the cross-sectional area of the cylinder, Dxh, and the density of air. Multiply this by a drag coefficient, CD, that is about 1 for a non-spinning cylinder, and about 2 for a fast spinning cylinder. FD= CDDhρv2/2.

A spinning cylinder has lift force too. FL= CLDhρv2/2.

Numerical lift coefficients versus time, seconds for different ratios of surface speed to wind speed, a. (Mittal & Kumar 2003), Journal of Fluid Mechanics.

As graphed in the figure at right, CL is effectively zero with sustained vibrations at zero spin, α=0. Vibrations are useless for propulsion, and can be damaging to the sail, though they are helpful in baseball pitching, producing the erratic flight of knuckle balls. If you spin a cylindrical mast at more than α=2.1 the vibrations disappear, and you get significant lift, CL= 6. At this rotation speed the fast surface moves with the wind at 2.1 times the wind speed. That is it moves significantly faster than the wind. The other side of the rotor moves opposite the wind, 1.1 times as fast as the wind. The coefficient of lift lift, CL= 6, is more than twice that found with a typical, triangular, non-rotating sail. Rotation increases the drag too, but not as much. The lift is about 4 times the drag, far better than in a typical sail. Another plus is that the ship can be propelled forward or backward -just reverse the spin direction. This is very good for close-in sailing.

The sail lift, and lift to drag ratio, increases with rotation speed reaching very values of 10 to 18 at α values of 3 to 4. Flettner considered α=3.5. optimal. At this α you get far more thrust than with a normal sail, and you can go faster than the wind, and far closer to the wind than with any normal sail. You don’t want α values above 4.2 because you start seeing vibrations again. Also more rotation power is needed (rotation power goes as ω2); unless the wind is strong, you might as well use a normal propeller.

The driving force is always at right angles to the perceived wind, called the “fair wind”, and the fair wind moves towards the front as the ship speed increases. Controlling the rotation speed is somewhat difficult but important. Flettner sails were no longer used by the 1930s because fuel became cheaper and control was difficult. Normal sails weren’t being used either for the same reasons.

In the early 1980s, there was a return to the romantic. Famous underwater explorer, Jacques Cousteau, revived a version of the Flettner sail for his exploratory ship, the Alcyone. He used aluminum sails, and an electric motor for rotation. He claimed that the ship drew more than half of its power from the wind, and claimed that, because of computer control, it could sail with no crew. This claim was likely bragging, but he bragged a lot. Even with today’s computer systems, people are needed to steer and manage things in case something goes wrong. The energy savings were impressive, though, enough so that some have begun to put Flettner sails on cargo ships, as a right. This is an ideal use since cargo ships go about as fast as a typical wind, 10- 20 knots. It’s reported that, Flettner- powered cargo ships get about 20% of their propulsion from wind power, not an insignificant amount.

And this gets us to the reason your curve ball does not curve: it’s likely you’re not spinning it fast enough. To get a good curve, you want the ball to spin at α =3, or about 1.5 times the rate you’d get by rolling the ball off your fingers. You have to snap your wrist hard to get it to spin this fast. As another approach, you can aim for α=0, a knuckle ball, achieved with zero rotation. At α=0, the ball will oscillate. It’s hard to do, but your pitch will be nearly impossible to hit or catch. Good luck.

Robert Buxbaum, March 22, 2023. There are also Flettner airplane designs where horizontal, cylindrical “wings” rotate to provide high lift with short wings and a relatively low power draw. So-far, these planes are less efficient and slower than a normal helicopter. The idea could bear more development work, IMHO. Einstein had an eye for good ideas.

Hydrogen transport in metallic membranes

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The main products of my company, REB Research, involve metallic membranes, often palladium-based, that provide 100% selective hydrogen filtering or long term hydrogen storage. One way to understand why these metallic membrane provide 100% selectivity has to do with the fact that metallic atoms are much bigger than hydrogen ions, with absolutely regular, small spaces between them that fit hydrogen and nothing else.

Palladium atoms are essentially spheres. In the metallic form, the atoms pack in an FCC structure (face-centered cubic) with a radius of, 1.375 Å. There is a cloud of free electrons that provide conductivity and heat transfer, but as far as the structure of the metal, there is only a tiny space of 0.426 Å between the atoms, see below. This hole is too small of any molecule, or any inert gas. In the gas phase hydrogen molecules are about 1.06 Å in diameter, and other molecules are bigger. Hydrogen atoms shrink when inside a metal, though, to 0.3 to 0.4 Å, just small enough to fit through the holes.

The reason that hydrogen shrinks has to do with its electron leaving to join palladium’s condition cloud. Hydrogen is usually put on the upper left of the periodic table because, in most cases, it behaves as a metal. Like a metal, it reacts with oxygen, and chlorine, forming stoichiometric compounds like H2O and HCl. It also behaves like a metal in that it alloys, non-stoichiometrically, with other metals. Not with all metals, but with many, Pd and the transition metals in particular. Metal atoms are a lot bigger than hydrogen so there is little metallic expansion on alloying. The hydrogen fits in the tiny spaces between atoms. I’ve previously written about hydrogen transport through transition metals (we provide membranes for this too).

No other atom or molecule fits in the tiny space between palladium atoms. Other atoms and molecules are bigger, 1.5Å or more in size. This is far too big to fit in a hole 0.426Å in diameter. The result is that palladium is basically 100% selective to hydrogen. Other metals are too, but palladium is particularly good in that it does not readily oxidize. We sometime sell transition metal membranes and sorbers, but typically coat the underlying metal with palladium.

We don’t typically sell products of pure palladium, by the way. Instead most of our products use, Pd-25%Ag or Pd-Cu. These alloys are slightly cheaper than pure Pd and more stable. Pd-25% silver is also slightly more permeable to hydrogen than pure Pd is — a win-win-win for the alloy.

Robert Buxbaum, January 22, 2023

Comparing Artemis SLS to Saturn V and Falcon heavy

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This week, the Artemis I, Orion capsule splashed down to general applause after circling the moon with mannequins. The launch cost $4.1 Billion, and the project, $50 Billion so far, of $93 Billion expected. Artemis II will carry people around the moon, and Artemis III is expected to land the first woman and person of color. The goal isn’t one I find inspiring, and I feel even less inspired by the technology. I see few advances in Artemis compared to the Saturn V of 50 years ago. And in several ways, it looks like a step backwards.

The graphic below compares the Artemis I SLS (Space Launch System) to the Saturn V. The SLS is 10% lighter, but the payload is lighter, too. It can carry 27 tons to the moon, while the Saturn V sent 50 tons to the moon. I’d expect more weight by now. We have carbon fiber and aramids, and they did not. Add to this that the cost per flight is higher, $4.1 B, versus $1.49 B in 2022 dollars for a Saturn V ($185 million in 1969 dollars). What’s more there was no new engine development or production, so the flight numbers are limited: Each SLS launch throws away five, space shuttle engines. When they are all gone, the project ends. We have no plans or ability to make more engines.

Comparison of Apollo Saturn V and Artemis SLS. The SLS has less lift weight and costs more per launch.

As it happens, there was a better alternative available, the Falcon heavy from SpaceX. The Falcon heavy has been flying for 5 years now, and costs only $141 million per launch, about 1/30 as much as an Artemus launch. The rocket is largely reusable, with 3D printed engines, and boosters that land on their tails. Each SLS is expensive because it’s essentially a new airplane built specially for each flight. Every part but the capsule is thrown away. Adding to the cost of SLS launches is the fuel; hydrogen, the same fuel as the space shuttle. Per energy it’s very expensive. The energy cost for the SLS boosters is high too, and the efficiency is low; each SLS booster costs $290M, more than the cost of two Falcon heavy launches. Falcon launches are cheap, in part because the engines burn kerosine, as did the Saturn V at low altitude. Beyond cost hydrogen has low thrust per flow (low momentum), and is hard to handle; hydrogen leaks caused two Artemis scrubs, and numerous Shuttle delays. I discussed the physics of rocket engines in a post seven years ago.

This graph of $/kg to low earth orbit is mostly from futureblind.com. I added the data for Artemis SLS. Saturn V and Falcon use cheaper fuel and a leaner management team.

It might be argued that Artemis SLS is an inspirational advance because it can lift an entire moon project in one shot, but the Saturn V lifted that and more, all of Skylab. Besides, there is no need to lift everything on one launch. Elon Musk has proposed lifting in two stages, sending the moon rocket and moon lander to low earth orbit with one launch, then lifting fuel and the astronauts on a second launch. Given the low cost of a Falcon heavy launch, Musk’s approach is sure to save money. It also helps develop space refueling, an important technology.

Musk’s Falcon may still reach the moon because NASA still needs a moon lander. NASA has awarded the lander contract to three companies for now, Jeff Bezos’s Blue Origin, Dynetics-Aerodyne makers of the Saturn V, and Musk’s SpaceX. If the SpaceX version wins, a modified Falcon will be sent to the moon on a Falcon heavy along with a space station. Artemis III will rendezvous with them, astronauts will descend to the moon on the lander, and will use the lander to ascend. They’ll then transfer to an Orion capsule for the return journey. NASA has also contracted with Bezos’s Blue origin for planetary, Earth observation, and exploration plans. I suspect that Musk’s lander will win, if only because of reliability. There have been 59 Falcon launches this year, all of them with safe landings. By contrast, no Blue Origin or Dynetics rocket has landed, and Blue Origin does not expect to achieve orbital velocity till 2025.

As best I can tell, the reason we’re using the Artemis SLS with its old engines is inspiration. The Artemis program director, Charlie Blackwell-Thompson is female, and an expert in space shuttle engines. Previous directors were male. Previous astronauts too were mostly male. Musk is not only male, but his products suffer from him being considered a horrible person, a toxic male, in the Tony Stark (Iron Man) mold. Even Jeff Bezos and Richard Branson are considered better, though their technology is worse. See my comparison of SpaceX, Virgin Blue, and Blue Origin.

To me, the biggest blocks to NASA’s inspirational aims, in my opinion, are the program directors who gave us the moon landing. These were two Nazi SS commanders (SS Sturmbannführers), Arthur Rudolph and Wernher Von Braun. Not only were they male and white, they were barely Americanized Nazis, elevated to their role at NASA after killing off virtually all of their 20,000, mostly Jewish, slave workers making rockets for Hitler. Here’s a song about Von Braun, by Tom Lehrer. Among those killed was Von Braun’s professor. In his autobiography, Von Braun showed no sign of regret for any of this, nor does he take blame. The slave labor camp they ran, Dora-Mittelbau, had the highest death rate of all slave labor camps, and when some workers suggested that they could work better if they were fed, the directors, Rudolph and Von Braun had 80 machine gunned to death. Still, Von Braun got us to the moon, and his inspirational comments line the walls at NASA, Kennedy. Blackwell-Thompson and Bezos are surely more inspirational, but their designs seem like dead ends. We may still have to use Musk’s SpaceX if we want a lander or a moon program after the space shuttle’s engines are used up. As Von Braun liked to point out, “Sacrifices have to be made.”

Robert Buxbaum, December 21, 2022. Here’s a bit more about Rudolph, von Braun, the Peenemünda rocket facility, and the Dora-Mittelbau slave labor camp. I may post photos of Von Braun with Hitler and Himmler in SS regalia, but feel uncomfortable doing so at the moment. I feel similarly about posting links to Von Braun’s inspirational interviews.