Saturday Snippet: Missile pioneers and the highly explosive (and stinky) fuel for their toys

 

John Drury Clark was a temperamental and successful scientist who specialized in the development of rocket fuels after World War II.  He wrote a well-known book, "Ignition! An Informal History of Liquid Rocket Propellants", which was widely circulated.  It's very amusing, as well as scientifically interesting to those with inquiring minds.  It was long out of print, but was republished in a new edition in 2018, to the gratitude of many who remembered it.

Although a technical book, it was also written for an audience of informed lay persons, and Dr. Clark's sense of humor and irreverence at authority shone through.  Isaac Asimov, who wrote the book's Foreword, said in it:

There are, after all, some chemicals that explode shatteringly, some that flame ravenously, some that corrode hellishly, some that poison sneakily, and some that stink stenchily. As far as I know, though, only liquid rocket fuels have all these delightful properties combined into one delectable whole.

Well, John Clark worked with these miserable concoctions and survived all in one piece. What's more he ran a laboratory for seventeen years that played footsie with these liquids from Hell and never had a time-lost accident.

My own theory is that he made a deal with the Almighty. In return for Divine protection, John agreed to take the Bible out of the fiction section.

Here are a couple of excerpts from the book, describing the development of early rocket propellants.  They demonstrate that even chemically abstruse scientists do, indeed, have senses of humor . . . and that "boys and their toys" are alive and well in laboratories too!

Standard Oil of California was the first of the oil companies to get into rocket propellant research in a big way, when Mike Pino, at the company's research arm, California Research, started measuring ignition delays in the fall of 1948.

At first his work resembled that of the other workers, as he demonstrated fast ignition with dienes, acetylenics, and allyl amines ... But then Pino, in 1949, made a discovery that can fairly be described as revolting. He discovered that butyl mercaptan was very rapidly hypergolic with mixed acid. This naturally delighted Standard of California, whose crudes contained large quantities of mercaptans and sulfides which had to be removed in order to make their gasoline socially acceptable. So they had drums and drums of mixed butyl mercaptans, and no use for it. If they could only sell it for rocket fuel life would indeed be beautiful.

Well, it had two virtues, or maybe three. It was hypergolic with mixed acid, and it had a rather high density for a fuel. And it wasn't corrosive. But its performance was below that of a straight hydrocarbon, and its odor — ! Well, its odor was something to consider. Intense, pervasive and penetrating, and resembling the stink of an enraged skunk, but surpassing, by far, the best efforts of the most vigorous specimen of Mephitis mephitis. It also clings to the clothes and the skin. But rocketeers are a hardy breed, and the stuff was duly and successfully fired, although it is rumored that certain rocket mechanics were excluded from their car pools and had to run behind. Ten years after it was fired at the Naval Air Rocket Test Station — NARTS — the odor was still noticeable around the test areas. (And at NARTS, with more zeal than judgment, I actually developed an analysis for it!)

California Research had an extremely posh laboratory at Richmond, on San Francisco Bay, and that was where Pino started his investigations. But when he started working on the mercaptans, he and his accomplices were exiled to a wooden shack out in the boondocks at least two hundred yards from the main building. Undeterred and unrepentant, he ... came up with the ethyl mercaptal of acetaldehyde and the ethyl mercaptol of acetone ... The odor of these was not so much skunk-like as garlicky, the epitome and concentrate of all the back doors of all the bad Greek restaurants in all the world. And finally he surpassed himself with something that had a dimethylamino group attached to a mercaptan sulfur, and whose odor can't, with all the resources of the English language, even be described. It also drew flies. This was too much, even for Pino and his unregenerate crew, and they banished it to a hole in the ground another two hundred yards farther out into the tule marshes. Some months later, in the dead of night, they surreptitiously consigned it to the bottom of San Francisco Bay.

. . .

As for Standard of Indiana, that organization went off on a wild tangent. Apparently jealous of their sister company of California and determined to do them one better, they went beyond mere sulfur compounds, and came down hard on phosphorous derivatives ... The one they gave the greatest play was "mixed alkyl trithiophosphites," which was a mixture of, mainly, the ethyl and methyl compounds. Its virtues were those of the mercaptans ... but its vices were also those of the mercaptans — exaggerated. The performance was below that of the mercaptans, and the odor, while not as strong as those of the Pino's creations, was utterly and indescribably vile. Furthermore, their structures had an unnerving resemblance to those of the G agents, or "nerve gases", or of some of the insecticides which so alarmed Rachel Carlson. This disquietude was justified. When some of the alkylthiophosphites were fired at NARTS, they put two rocket mechanics in the hospital, whereupon they were summarily and violently thrown off the station.

. . .

Many, if not most, of the acetylenics had poor storage properties, and tended to change to tars or gels on standing. They also tended to form explosive peroxides on exposure to the atmosphere. Many of them were shock sensitive, and would decompose explosively with little or no provocation. Something like divinyldiacetylene can fairly be described as an accident looking for a place to happen. While some of them were fired successfully in a rocket ... They usually detonated on contact with the oxidizer, as several possessors of piles of junk that had originally been ignition delay equipment could testify, and did.

. . .

The RFNA of 1945 was hated by everybody who had anything to do with it, with a pure and abiding hatred. And with reason. In the first place, it was fantastically corrosive. If you kept it in an aluminum drum, apparently nothing in particular happened — as long as the weather was warm. But when it cooled down, a slimy, gelatinous, white precipitate would appear and settle slowly to the bottom of the drum. This sludge was just sticky enough to plug up the injector of the motor when you tried to fire it. People surmised that it was some sort of a solvated aluminum nitrate, but the aversion with which it was regarded was equaled only by the difficulty of analyzing it.

If you tried to keep the acid in stainless steel (SS-347 stood up the best) the results were even worse. Corrosion was faster than with aluminum, and the acid turned a ghastly green color and its performance was seriously degraded ... And, if my own experience is any criterion, there was a bit of insoluble matter of cryptic composition on the bottom of the drum. Acid like that might have been useful in the manufacture of fertilizer, but as a propellant it was not.

So the acid couldn't be kept indefinitely in a missile tank — or there wouldn't be any tank left. It had to be loaded just before firing, which meant handling it in the field.

This is emphatically not fun. RFNA attacks skin and flesh with the avidity of a school of piranhas. (One drop of it on my arm gave me a scar which I still bear more than fifteen years later.) And when it is poured, it gives off dense clouds of NO2, which is a remarkably toxic gas. A man gets a good breath of it, and coughs a few minutes, and then insists that he's all right. And the next day, walking about, he's just as likely as not to drop dead.

. . .

In general, everybody got respectable performances out of peroxide, although there were some difficulties with ignition and with combustion stability, but that freezing point was a tough problem, and most organizations rather lost interest in the oxidizer.

Except the Navy. At just that time the admirals were kicking and screaming and refusing their gold-braided lunches at the thought of bringing nitric acid aboard their beloved carriers; they were also digging in their heels with a determined stubbornness that they hadn't shown since that day when it had first been suggested that steam might be preferable to sail for moving a battleship from point A to point B.

So NOTS was constrained to develop a "nontoxic" propellant system based on hydrogen peroxide and jet fuel, and with acceptable low temperature behavior.

. . .

Most of the Navy work on peroxide was not directed toward missiles, but toward what was called "super performance" for fighter planes — an auxiliary rocket propulsion unit that could be brought into play to produce a burst of very high speed — so that when a pilot found six Migs breathing down his neck he could hit the panic button and perform the maneuver known as getting the hell out of here. The reason for the jet fuel was clear enough; the pilot already had it aboard, and so only an oxidizer tank had to be added to the plane.

But here an unexpected complication showed up. The peroxide was to be stored aboard airplane carriers in aluminum tanks. And then suddenly it was discovered that trace quantities of chlorides in peroxide made the latter peculiarly corrosive to aluminum. How to keep traces of chloride out of anything when you're sitting on an ocean of salt water was a problem whose solution was not entirely obvious.

And there was always the problem of gross pollution. Say that somebody dropped (accidentally or otherwise) a greasy wrench into 10,000 gallons of 90 percent peroxide in the hold of the ship. What would happen — and would the ship survive? This question so worried people that one functionary in the Rocket Branch (safely in Washington) who had apparently been reading Captain Horatio Hornblower, wanted us at NARTS to build ourselves a 10,000-gallon tank, fill it up with 90 percent peroxide, and then drop into it — so help me God — one rat. (He didn't specify the sex of the rat.) It was with considerable difficulty that our chief managed to get him to scale his order down to one test tube of peroxide and one quarter inch of rat tail.

Carrier admirals are — with good reason — deadly afraid of fire. That was one of the things they had against acid and a hypergolic fuel.

A broken missile on deck — or any sort of shipboard accident that brought fuel and acid together — would inevitably start a fire. On the other hand, they reasoned that jet fuel wouldn't even mix with peroxide, but would just float on top of it, doing nothing. And if, somehow, it caught fire, it might be possible to put it out — with foam perhaps — without too much trouble.

So, at NARTS we tried it. A few drums of peroxide (about 55 gallons per drum) were poured out into a big pan, a drum or two of JP-4 was floated on top, and the whole thing touched off. The results were unspectacular. The JP burned quietly, with occasional patches of flare or fizz burning. And the fire chief moved in with his men and his foam and put the whole thing out without any fuss. End of exercise.

The Lord had his hands on our heads that day — the firemen, a couple of dozen bystanders, and me.

For when we — and other people — tried it again (fortunately on a smaller scale) the results were different. The jet fuel burns quietly at first, then the flare burning starts coming, and its frequency increases. (That's the time to start running.) Then, as the layer of JP gets thinner, the peroxide underneath gets warmer, and starts to boil and decompose, and the overlying fuel is permeated with oxygen and peroxide vapor. And then the whole shebang detonates, with absolutely shattering violence.

When the big brass saw a demonstration or two, the reaction was "Not on my carrier!" and that was that.

It must have been an exciting time, working with what was then chemistry so advanced nobody knew what to expect.  Sadly, some of those doing the experiments didn't survive them, as the book describes.  However, a great deal of the chemistry we take for granted today was developed in those years.  Today, nobody thinks about the risks that were involved.

Peter