Can fusion arrive soon enough?

 kw: book reviews, nonfiction, science, controlled fusion, renewable energy

Could this power our future?

This is the inside of a Tokamak, a bagel-shaped magnetic "bottle", as the temperature in the plasma (the violet stuff) is ramping up toward 100 million degrees or so, a temperature needed to trigger fusion between deuterium and tritium nuclei.

The Star Builders: Nuclear Fusion and the Race to Power the Planet, by Arthur Turrell, is a hopeful progress report of sorts, on the one near-renewable energy technology that just might secure the future of the human species on earth.

I expect that the technology will soon drop the adjective "nuclear", and just be called "fusion" or "fusion energy", because of intense public antipathy towards all things nuclear, based on hyped-up fears of future disasters such as those at Three Mile Island, Chernobyl, and Fukushima. Maybe we can invent a new adjective to distinguish between "fusion" meaning fusion energy, and other uses of the word, such as "Asian fusion", for eclectic Eastern cuisine, and "The fusion of enlightenment and entertainment", the purview of media host Glenn Beck.

The recipe for sustaining energy-producing fusion reactions is simple. For any type of nucleus, or pair of nuclei, a specific combination of temperature and pressure is needed to initiate the fusing of nuclei into bigger ones, and there is a well known function that relates the amount of fusion energy produced, per kg of "stuff", at any combination of pressure and temperature increase beyond that threshold. As Dr. Turrell describes, the "easiest" reaction is between deuterium (hydrogen with a nucleus containing one proton and one neutron) and tritium (hydrogen with a nucleus containing a proton and two neutrons). In the conditions a Tokamak is aiming for, with a pressure of a few millibars (about 1/100 atmospheric pressure), the threshold temperature is 150 million K (=150 million °C, minus 273, a trifling amount we can ignore; also equal to about 270 million °F).

It might seem trivial to work with a low pressure like that, but the issue is not pressure, but the consequences of searingly hot plasma touching the materials of the "bottle", such as the metal walls of a Tokamak. Consequence 1: the metal boils. Consequence 2: the plasma cools off, quenching any fusion reaction. Result: the device won't make energy, and it may be destroyed.

Thus, there are three ways to keep the plasma "in the bottle": magnetic confinement, inertial confinement, or gravitational confinement. Gravitational confinement is what every star uses to keep its fusion engine working.

A star with a mass of at least 0.075 that of the Sun, or about 25,000 times the mass Earth, has a dense enough core, at a high enough temperature, for about one in a trillion collisions between two hydrogen nuclei (protons, with no neutrons at all), to fuse into a deuteron (a deuterium nucleus), absorbing an electron (or kicking out a positron) in the process to convert one proton to a neutron. Deuterons more readily fuse with more protons to produce tritons (tritium nuclei) and then again to form helium nuclei (also with the absorption of another electron or ejection of a positron). The threshold temperature is several million K, at a pressure of a few million atmospheres.

On Earth, gravitational confinement is out, so magnetic or inertial methods must be used. The Tokamak is one kind of magnetic "bottle", and is currently favored as the most likely to "work." A version called the Spherical Tokamak, shaped more like an apple than a bagel, is described and may wind up working better. Current research is aiming to deal with huge amounts of instability that occur when you try to keep a superhot plasma "in the bottle."

Inertial confinement is based on methods that compress a pellet of fusible material by a factor of a hundred or so (in diameter; a million-fold in volume), which pushes the temperature to millions of degrees, and any fusion that is going to happen is completed in a few billionths of a second. Nothing works that fast except laser light.

The National Ignition Facility (NIF) uses the world's most powerful laser system, 192 lasers that create about 400 megajoules of infrared energy. A megajoule is a million watt-seconds, or 278 watt-hours. A "shot" begins with a pulse, 20 nanoseconds long, in 192 beams, with a total of 53 kilowatt-hours of energy. The light is up-converted twice to become about 2 megajoules of UV light, still compressed into 20 ns, which gets focused into two tiny openings, each a little bigger than a pinhole, at the ends of a barrel-shaped gold capsule called a hohlraum, that contains a fuel pellet (hydrogen isotopes at the center of other layers). This deposit of an incredi-jillion watts per square whatever, on the inside surface of the hohlraum, produces X-rays that compress the fuel pellet. Fusion has to happen in one or two ns, while inertia keeps the pressure in the now-compressed capsule at some unimaginable number of gigabars (billions of atmospheres) of pressure, at millions of degrees. NIF was built for research. A power plant using the technology would have to drop a fuel pellet every few seconds (and that consumes a lot of gold), for years and years, to be a commercial energy-producing reality. After every shot at NIF it takes days to repair damage caused by the immense power of the lasers.  Yeah, I'd say the odds are pretty long…

As of the writing of Star Builders, a Tokamak has achieved 67% of "ignition", and NIF has hit 3%. Commercial power production requires not just ignition, not just break-even (power out = power in), but 10x to 100x of break-even. What if running a 500 MW power plant consumed 400 MW? The remaining 100 MW that could be sold will be costly indeed, and there will be an incredible waste heat problem. A 500 MW fusion plant must consume no more than 1% to 10% of its own energy.

Other than waste heat, other wastes represent an area where fusion energy excels. Current nuclear fission power plants produce radioactive waste, which must be safely stored or disposed of. Nuclear fusion, on the other hand, does produce some radioactive waste, but only in very small amounts, comparatively. Any nuclear process releases lots of neutrons, but a fusion plant can be built of materials that either don't absorb many neutrons or do not become radioactive by doing so.

The big question is this: How soon will any of these schemes be ready for prime time? From that point, how long will it take to build a few thousand power plants, worldwide, to take over electricity generation from coal (still #1 worldwide), natural gas, oil, and all the rest. I'd include windmills in that, because they aren't really renewable; they are an arcane way of turning electricity in one place into steel, aluminum and other materials, and using wind to recover most (but NOT ALL!) of the original energy used to make the windmill, until the windmill must be replaced.

The only energy technology that is (only since about 2010) renewable over its life cycle: Solar-electric panels. But this has big drawbacks, the biggest being, the Sun shines only half the day. Battery storage is still too costly and its energy density is too low, to make much of a dent in the problem.

Dr. Turrell is optimistic. To him, we are dramatically under-invested in fusion research. If throwing money at the problem could speed it up, so a facility somewhere achieves commercially-ready fusion power by 2024, that would be great, but could we then ramp up fast enough to save ourselves from the climate change that is growing around us?

Disclaimer: I know "warming" is in part human-caused. I am not convinced it is an absolute negative. The impact will be negative in some places, and positive in others. Bet on it.

But can we grow fusion power enough to stop making carbon dioxide completely? Can we do it fast enough to avert a climate crisis? Not without making more use of fission energy, while the research is completed and fusion (when it arrives) gets rolled out worldwide. The sideboards on my estimate of the time frame are between 2040 and 2140...or later. A lot is still not known. Interesting times are ahead! This book will be a useful reference in years ahead.

Digging In

 kw: book reviews, nonfiction, biology, paleontology, burrowing, trace fossils

Are we still cavemen, somewhere deep inside us? Some folks are. The people who live in a certain part of Cappadocia certainly are, if not cave dwellers, certainly burrow dwellers. The soft volcanic stone in the area is easily dug. Several thousand people live in underground, or within-rock, dwellings. Some of these unique burrow-houses, along with churches and other public places, were carved in the rock as long ago as 300 AD.

Does this make humans the largest burrowing animals? Actually, that distinction belongs to grizzly bears, as we read in The Evolution Underground: Burrows, Bunkers, and the Marvelous Subterranean World Beneath Our Feet, by Anthony J. Martin.

Dr. Martin is an ichnologist, a scientist who studies trace fossils: fossilized tracks, trails, and burrows made by animals. His book shows how knowledge of the ways animals have trod on, dug into, and tunneled underground have created the natural environment. For example, a motto in his field is, "Without animals that tunnel and poop, there would be no mud." Geological forces tend to mix clay and silt and organic sludge into larger-grained sediments. Animals that tunnel within those sediments are frequently like earthworms and marine worms, that ingest the "dirt", digest the organic part, and defecate pellets of the remaining mineral bits mixed with mucus, typically onto the surface (look for little piles of pellets near wormholes after a rainstorm). These pellets glomp together into "mud". (Yes, Virginia, dirt is mostly silt and clay mixed with animal poop and poop eaten and re-pooped. Now, don't you want to wear gloves when you garden?)

It is likely that ants plus termites make up more than half of the total mass of all animals. And they are nearly all inveterate tunnellers. How far back did "bioturbation" (the stirring of the sediment by animals) begin? The book has a tentative answer: Around 541 million years ago, or a little before, during the transition from the Ediacaran Period to the Cambrian Period.

The Ediacaran Period, from 635 to 541 million years ago (mya) is named for a region in Australia where these unusual soft-bodies fossils were first found. In this image the scale bars are either 1/2cm (black) or 1cm (white). The best analysis of the environment of these animals, or proto-animals, is of quiet seabeds with a surface composed of bacterial mats, which sometimes humped up into stromatolites, which originated about two billion years earlier. None of these critters had shells or teeth, and they seem to have fed on the waste products of the bacteria and perhaps a little bit on the bacteria themselves. It seems they did not feed on each other; there were no predators yet.

They apparently did not have the wherewithal to dig into or under the bacterial mats. At the very end of this period, transitional animals called the Small, Shelly Fauna (SSF) appeared, and they did begin to dig in. They also seem to have fed on the soft-bodies feast around them, because the "softies" soon vanished.

The SSF quickly gave way to the animals of the Cambrian Period, from 541 to about 485 mya, which were shelled creatures such as the beloved trilobites, but included all modern phyla plus a number of phyla that have gone extinct. Here we see a trilobite and a blastozoan (distant relative of sea stars).

The book has quite a chapter on the trackways left by trilobites, and the confusion that sometimes results when other many-legged creatures leave tracks that look similar at first glance.

Cambrian animals didn't just leave tracks in the bottom. Burrowing as a lifestyle seems to have begun among nearly all phyla during the Cambrian Period.

Why burrow? For some, food is found there (ask any mole or earthworm). Protection and privacy: it is easier to defend eggs and babies when they are in tunnels or bunkers or burrows. Making babies is safer in a burrow also; the blissful couple is less likely to be interrupted. There are actually birds that tunnel to protect their eggs and young.

The creatures that survived the "big five" extinctions were mostly burrowers. This is seen on a small scale in a description that begins Chapter 9, "Viva La Evolución: Change Comes from Within". Pocket gophers that happened to be in their tunnels during the Mount St. Helens eruption of May 18, 1980, found their tunnel mouths buried under loose ash, through which they had to tunnel upwards to attain the new surface of the ground. They did so, in large numbers, all over the area that was devastated and incinerated by the nuée ardent ("glowing cloud") of superheated gas and melted glass that roared off the mountain. 57 humans that were within around a 10 mile radius of the volcano died. Thousands of pocket gophers, including some very much closer to the mountain, were safe in their dens and emerged to repopulate the area with their own mini-population explosion.

Chapter 8, "Rulers of the Underworld", surveys the breadth of kinds of animals that live literally underfoot, from ants to armadillos, and some that are (or were) a bit too big to be literally underfoot, such as the giant ground sloths that left tunnels you can almost drive a car through in parts of South America.

A major theme of the book, found in most chapters, is that the diggers all around us are ecosystem engineers. The gopher tortoise is a superstar of ecosystem engineering. These middlin-sized tortoises tunnel industriously, making spaces not only for themselves, but for about 400 species of animals that get the opportunity to dwell in those spaces, or in side tunnels off of them. A foot-long tortoise makes a one-entrance tunnel 5-15 meters long, going as deep as 3 meters, to an enlarged den. If you were to excavate a well-used tunnel, however, you would find numerous side tunnels made by mice and toads, also by dung beetles and other insects. The tortoises move tons of earth about, and areas with many burrowing animals in general are well-aerated because they are to well-perforated! The constant digging and mixing means we live amidst an extensively re-worked landscape…or, at least, those of us who live outside cities.

Even in my suburban area, a typical shovelful of garden soil contains one or two dozen earthworms (multiply by the thousands of square feet in my yard). There are also the burrows and tunnels of mice, voles, camel crickets, and a dozen species of ant.

It's good to be reminded, or enlightened, regarding the many uses of the underground and the wildlife that inhabits and creates it. A thoroughly enjoyable book.

Pardon me for continuing with a criticism or two; you can stop reading here if you prefer. The points below don't diminish the value or enjoyment of the book.

More and more I find myself wishing authors and publishing houses would make more and better use of copy editors and proofreaders. A spell-checker is only 10% of the task. Some examples:

• On page 142 I found this in a description of the impact of the asteroid that wiped out the dinosaurs 65 million years ago: "The impact…instantly converted its potential energy into kinetic energy…". Hardly! The rock was moving about 30 km/s, and that's all kinetic energy. It was converted, first to thermal energy (melting and evaporating rock and ocean water), and then to more kinetic energy of the "splash stuff", molten rock lobbed halfway around the planet. The copy editor needs to know some physics.
• The word "had" was omitted from a phrase that should have read, "…cobbles of sandstone that had fallen off the slope…" Page 148.
• Faulty math: the statement that ants probably outweigh humans (true), is followed up by "one million ants per person". Hmm. I weigh just under 100 kg, or 100,000 grams. One millionth of my weight is 100 mg. I suspect a 100 mg ant would be a fearsome critter! Large (12mm) carpenter ants weigh 20-30 mg; maybe the colony's queen approaches 50 mg. The average worker ant of all species weighs about 2 mg, so it would take 50 million ants to balance me on the scales. Page 226.
• The author in one place states that a hectare is 100 square meters, but a hectare is actually 100 meters squared, or 10,000 square meters (107,639 sq ft). That is 2.471 acres. I found a few places (p. 235 is one), where the ratio is reversed, indicating that the author (or someone he quoted) calculated 2.5 hectares per acre. That's quite different from both 100 sq m and 10,000 sq m.

To be honest, these complaints total half a page; out of a 400-page book, that isn't bad. I like Dr. Martin's writing.

Science Fiction is Growing Up

 kw: book reviews, science fiction, anthologies, short stories

This image doesn't illustrate any of the stories in The Best Science Fiction of the Year: Volume 6, edited by Neil Clarke. I stumbled across the picture and it appealed to me. It isn't lost on me that everyone except the girl is in an environmental suit. Is it for the sake of the cheesecake? Or just a broad hint that this is on Earth, in some future time? I surmise the latter.

Of the 32 stories in The Best, for most, whether they take place on Earth isn't relevant. The ones I liked best presented new takes on writing from the viewpoint of The Other. "Exile's End", by Carolyn Ives Gilman, portrays two viewpoints equally deftly, that of an Ordinary Human (or a descendant thereof) and a descendant of humans who took to the stars so long ago that they are quasi-alien, and have a culture almost beyond the grasp of OH's. Crossing that divide is the crux of the story. "Tunnels" by Eleanor Arnason presents sympathetic aliens, including one who partners with the human protagonist because, as it tells her, "You saw me. You asked my name."

"Sinew and Steel and What They Told" by Carrie Vaughn presents a human so seriously modified (but all inside) it's hard to think he's still human. At the core, he is human, which makes all the difference in the end.

I am a musician who appreciates fine instruments. The luthier in "An Important Failure" by Rebecca Campbell spends a lifetime gathering the right tone woods and structural woods to make a violin, the first in centuries to compare on an equal basis with the famous violins of the 17th Century such as Amati and Stradivarius. In the author's view the secret to the fine sound of violins of this era is the climate, which was unusually cold for a century or two, producing trees with exceptionally fine grain. Even with the finest woods, it takes a violin about a century of frequent play to achieve its greatness. The milieu of the story is a warmer world that just doesn't grow fine-grained wood any more.

"Red_Bati" by Dilman Dila is the story of a robot dog with the body type of a red basenji. This dog has sufficient AI to create a "ghost" of a beloved human, as a companion, and to take over a spaceship (sorry for the spoiler). The author is one of several Desi (Indian subcontinent) authors in this volume. I found their stories particularly evocative.

Perhaps a quarter of the stories have a warmer Earth in their background. While I don't agree that "global warming" will proceed as far as the dire predictions of the IPCC, nor that its effects will be all bad, this is one area of speculation that richly rewards the investigation and mental experimentation that makes science fiction so great. "Textbooks in the Attic" by S.B. Divya sets the rich, in high-ground walled enclaves, against all others, in their flooded world, struggling to reinvent antibiotics while books that didn't get moved to attics fast enough rot away.

Science fiction before about 1965 was mostly of the "gee whiz" variety, though many great writers such as Arthur C. Clarke and Lester Del Rey wrote with much more sophistication. But many of my early favorites were the Lensman series and stories such as Venus Equilateral by George O. Smith, stories more about technology, with characters that were rather two-dimensional.

Later, as the "sexual revolution" got under way, triggered by court rulings that "porn is in the eye of the beholder", authors of all stripes, but particularly science fiction authors, went hog-wild. Most science fiction for the next generation seemed to be extended wet dreams, mainly by male authors airing their most erotic fantasies. I didn't read hardly any science fiction for many years, except to "check in" from time to time to see if it was wearing off. By about 2000 much had worn off, and writers were again exploring themes of greater breadth and wider interest. When I started this blog in 2005, I was again reading science fiction regularly, but only as about 10% of my "intake"; most of my reading for many years has been nonfiction, and most of that on scientific subjects. If you peruse this blog, you'll note quite a variety of subjects.

I am glad to note that I skipped only two stories in The Best, and that because of egregious violence, not overdone eroticism. I can again say, after reading most of the stories in this volume, "I am glad I read that."