*Richard Wolkomir / DISCOVER / AUG 89 / 77:81*

* Fifty miles outside Trinity, New Mexico, the spot where the first atomic bomb was detonated, mangled warplanes -- ancient B-36's, B-57's, and F-86's -- lie strewn across the desert floor.  From the looks of things the aircraft were intact when they arrived, but since then something has done them serious damage.
On a road to the east, where the town of Socorro sits on the bank of the Rio Grande, a van bounces along in the dust, carrying four men in hard hats.  The van disappears into the mountains; a siren wails; wails again a few minutes later; and then:
In far-off Socorro the resounding blast shakes California Street, the town's main drag.  But nobody pays it any mind; they're all quite used to it.  This sunbaked community and adjacent mountain test site are home to the New Mexico Institute of Mining & Technology, where they have a simple mission in life: blow up things.  The institute is the nation's leading facility for explosives research.
* Actually, the institute houses two facilities.  The oldest, which test munitions and armor for the military, is the Terminal Effects Research & Analysis Group.  An offshoot of World War II ordnance research, the Terminal Effects Group was settled at Socorro in 1949, at a site made attractive by its desert emptiness and the proximity of the White Sands Missile Range and the Air Force Weapons Laboratory.  This is what created the aircraft graveyard: the jets were targets used to measure the damage caused by specific munitions.
The other facility, the Center for Explosives Technology Research, does less warlike work.  This branch of the institute was set up in 1983 to develop industrial and commercial applications of explosives.  Every month they set off dozens of explosions, ranging from popgun bursts to ground-shaking
eruptions. It's early morning, but materials scientists Marc Meyers and Naresh Thadhani have already begun preparing the day's explosion.  Parking their van outside the Big Eagle firing bunker, a thick-walled concrete structure buried in the side of a mountain, they begin unloading wires, fuzes, bomb cases.  Today's experiment is a relatively routine one: using a volatile mixture known as ANFO -- a combination of ammonium nitrate and fuel oil -- they will try to transform a mix of powders into a solid superconducting ceramic.
[ED: According to a certain voluble redneck I happen to know, this is roughly the explosive used in the OKC bombing -- you mix nitrate fertilizer with diesel until it has the consistency of toothpaste ... not that I'd want to try such an experiment myself, by any means.  I recall stories of a cargo ship carrying nitrate fertilizer that leveled a Gulf Coast town during World War II when it caught fire and its diesel tanks ruptured.]
Traditionally, superconducting powders are fused into ceramics in powerful presses or ovens.  The high temperatures are necessary for the powders to fuse, but if they overheat, the ceramic can break down and lose its superconducting properties.  The process is also slow; the powders must be pressed or baked repeatedly.  Explosives, however, can do the job in a few millionths of a second.  When the charge is detonated, the shock wave moves through the powders at more than 11,000 feet per second, squeezing the grains together violently.  The surfaces of the grains melt and fuse, but the interior of each stays solid.
Big Eagle is jammed with equipment, but the experiment Meyers and Thadhani rig up appears home-built.  A copper capsule a few inches long is filled with superconducting powders and set on a plate.  Around the capsule the two men place a section of black plastic pipe, which they fill with 4 pounds of ANFO. The stuff looks like coarse sand and smells of fuel oil.  Meyers and Thadhani then attach a detonator and run a cable to the bunker.
They return to the bunker and close the door, sound the warning siren twice, and then press a button to send 2500 volts to the detonator.  There is a flash of light, a loud thud, a shower of black debris -- and all that is left is the twisted copper cylinder.
Thadhani emerges to poke at the still-hot cylinder.  "The last time we tried this, we used 8 pounds of ANFO," he says.  "But the intense pressure generated by the explosion caused the ceramic to crack.  This time we used only 4 pounds." The contents of the cylinder will be taken back to the lab to be analyzed and fine-tune the technique.
* There are thousands of types of chemical explosives -- familiar ones include black powder, TNT, and ANFO -- and they typically involve fusing oxygen-nitrogen compounds with hydrogen-carbon compounds.  When the two are confined together and excited by heat or shock, the nitrogen breaks its electron bonds with the oxygen; then the free oxygen mingles with the carbon or hydrogen, instantly forming intense heat, water vapor, and other gases.
"An explosion's pressure can reach several million pounds per square inch," says Fred Sandstrom, an explosion specialist who is involved in the superconductor studies.  A single kilogram of TNT delivers about 5000 megawatts of power for a split second.
The earliest recorded explosives were devised by Byzantine Greek alchemists in the 7th century; they found that a nasty brew of pitch, naptha, sulfur, and petroleum would burst violently when ignited.  The mix was known as Greek fire; the empire's military used it to defend Constantinople from invading Saracens.
Greek fire was an unstable and inconvenient explosive.  Around the year 1000 AD the first really usable explosive -- black powder -- was invented.  It is not known for certain who discovered that a mixture of potassium nitrate (saltpeter), sulfur, and charcoal gets violent when lit, but most scholars credit the Chinese, who used it in fireworks and signals.  The new mixture found its way into cannons, muskets, and bombs.
The next big breakthrough came in 1846, when an Italian chemist named Ascanio Sobrero added glycerol to a mixture of nitric and sulfuric acids and nearly killed himself in the resulting explosion.  Sobrero decided that the stuff he called nitroglycerine was too dangerous and tried to keep it a secret.  He failed; Sweden's Nobel family obtained the formula and began manufacturing it as "blasting oil" for mining.
Some years later Alfred Nobel invented the less volatile substance he called dynamite, named for the Greek "dynamis", or "power".  By mixing dynamite with a porous, siliceous material, he created a compound he could drop, hammer, or even burn without causing it to explode.  When subjected to the strong percussive shock of a blasting cap, however, it delivered as powerful an explosion as pure nitroglycerine.
Dynamite was the first really convenient explosive and proved so popular that Nobel was publicly labeled the "merchant of death"; he established the Nobel prize to help uphold his family's dignity.  After dynamite came the deluge; there are as many as 20,000 different explosives today.  Many are variations on black powder or TNT.  Many are entirely new compounds.
* There is still plenty of work on improving explosives for use in warfare, but the Center for Explosives Technology Research remains focused on more constructive applications.  In the same labs where the superconducting work is being done, Thadhani shows off a small square of metal, a lightweight laminate composed of 15 alternating layers of aluminum foil and piano-wire mesh with an unusually high strength-to-weight ratio.
To create the composite, the researchers stack thin layers of foil and mesh until they have a sandwich that's a quarter to half-inch high.  On top of that they place a metal sheet called a flyer plate; and on top of that they place a layer of powdered ANFO.  Only the upper surface of the explosive is exposed to the air; since the shock wave of the explosion moves faster through the solid material below than through the air above, when the ANFO blows, it blows mostly downward.  This causes the flyer plate to compress the layers into a single, fused unit.
The new material could be used for armor or lightweight aerospace structures. It can be manufactured much more readily and cheaply than other laminates, most of which are either liquified and poured into molds or welded together in hot presses.  There is no need for clean production facilities, either; the blast vaporizes the metal between the layers, scouring impurities out of the edges.
Explosive manufacturing sometimes requires a more focused blast, however, and a device called an explosive plane wave lens is required, which delivers a hammer-blow shock in just one direction.  Essentially the lens is a plate topped by a disk of explosive and then two-layer cone of explosive material; a solid inner cone molded out of a relatively slow-blowing explosive, and an outer layer of faster-burning material.  The two cones allow the explosive to burn evenly; if the entire cone was made of the same explosive, the outer parts -- with farther to travel -- would take longer to combust than the inner part, and the charge at the bottom would not be detonated at one time.
Thadhani and his colleagues are using the explosive lens to build industrial diamonds of unsurpassed quality.  Natural diamonds are formed from carbon under pressure for eons in deeply buried rock; an explosive lens can be used to generate the same or greater pressures for a short period of time. The researchers pack diamond powder into square-inch stainless-steel capsules and then pack the capsules into a metal holder.  An explosive lens is used to subject this assembly to a million times the air pressure at sea level.  The results are big polycrystalline industrial diamonds, half an inch in diameter and 85% as hard as natural diamonds, a record for artificial diamonds. "They're dark and ugly," says lab manager Ed Roy, "but they're perfect for industrial jobs like slicing metals."
Another project at the center involves explosive welding; studies have shown that if two pieces of metal are driven into each other by an explosive blast, they will form a weld far superior to that obtained with a welding torch. "Ordinary welding," says the center's assistant director, Pharris Williams, "leaves microscopic gaps that can lead to oxidation and corrosion.  With explosion welding, the materials interlock so snugly that corrosion isn't possible."
Explosive welding is now being used in the construction of nuclear power plants; explosive plugs are fitted into pipes and then detonated, sealing tiny leaks.  The method is also being used in Europe for welding rails for high-speed trains.
Yet another application of explosives is of course mining.  "Say you've discovered a lode of coal under a hundred and 150 feet of earth, sandstone, and shale," says Roy.  "Ordinarily, you'd have to dig it all up with bulldozers.  But newer compounds can put out more heave over a longer period of time.  This can expose millions of tons of coal and keep a mining company busy for months."
* Despite these interesting applications, most of the facility's focus is not on building bigger bangs, but on making safer ones.  For example, explosives are often used to clear sand-blocked oil channels at the bottoms of deep wells, but the temperatures 15,000 feet below the ground are often enough to detonate the charges before they reach their proper objective, causing more harm than good.  The center hopes to correct this problem by developing "insensitive" explosives.
"An insensitive explosive," says Roy, "is essentially a buffered explosive. We've developed a way to bond a plastic compound to each crystal of an explosive material.  This services to stabilize the explosive chemically, physically, and thermally.  Insensitive explosives go off only when you want them to go off."
The military is of course busy in this field as well.  "A Navy ship may be filled with missiles, aircraft, and fixed ammunition," says Roy.  "That's a very dangerous vessel.  If it takes a hostile strike, an entire ordnance magazine can be set off.  As a result, the military has its own drive on to develop insensitive explosives.  What they learn they're transferring to us, and what we learn we're transferring to them."
"We're working on explosives that don't accidentally do anything," says the center's director, Per-Anders Persson.  "Some already have the qualities of a block of wood unless they're detonated by a charge of the right size and power." He is interested in developing "smart" detonators -- fuzes with silicon smarts that won't fire unless given a code sequence that is unlikely to occur by accident.
Persson was recently summoned to help diagnose what went wrong at a Nevada chemical plant where an explosion in the spring of 1988 killed two people, injured more than 100 others, and destroyed a substantial portion of a key ingredient used in the space shuttle's solid fuel.  His role in this has helped drive another one of the center's efforts: finding ways to store volatile materials for long periods with minimum risk.
"We're learning how to handle these materials better and feel safer around them," says chemist Jimmie Oxley.  To Oxley, the explosives are merely tools. "I once had my students analyze the energy in a Snickers candy bar; it turned out to be equal to a couple grams of TNT," she says.  "The only difference between the dynamite and the candy is that the dynamite releases its energy a little faster."

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