There have been a few news items about satellite launches and the like recently. This weekend it was SPACEX’s successful delivery to the ISS and its un-successful attempt to land part of the rocket on a floating platform. At the end of January the news will be about the (hopefully successful) attempt to launch  the SMAP mission: a new sort of satellite to monitor soil moisture.

The fact that this stuff is still news is a reminder that launching rockets into space is not entirely routine and continues to be very difficult. Rocket Science is hard (and the otherwise-splendid Shania Twain was wrong to be unimpressed by it). This point is also made by one of the most interesting and entertaining books that I have read over the last year: Ignition!, by John D. Clark. Unfortunately, the book is in that annoying state of limbo where it is long out of print, but the copyright has not expired. It is therefore hard to find a physical copy, but the book can not be legitimately put onto the web; you won’t find it on Project Gutenberg, for example. There are various unauthorized electronic copies circulating on the web: if you google for “Clark Ignition” you may well find one. Just don’t say that  I sent you.

Some idea of the tone of the book can be inferred from the opening paragraph:

The dear Queen had finally gone to her reward, and King Edward VII was enjoying himself immensely as he reigned over the Empire upon which the sun never set. Kaiser Wilhelm II in Germany was building battleships and making indiscreet remarks, and in the United States President Theodore Roosevelt was making indiscreet remarks and building battleships. The year was 1903, and before its end the Wright brothers’ first airplane was to stagger briefly into the air. And in his city of St. Petersburg, in the realm of the Czar of All the Russias, a journal whose name can be translated as “Scientific Review” published an article which attracted no attention whatsoever from anybody.

The book goes on in this vein to describe the history of rocket propellants, from Tsiolkowsky’s un-noticed article to the early 1970s, at which point we had landed on the Moon. Possibly the most famous passage is that describing the properties of Chlorine trifluoride (ClF3). If, like me, your chemistry goes no further than the first year of University you might be surprised that such a molecule even exists. It does, though. John Clark writes:

[Chlorine trifluoride] is, of course, extremely toxic, but that’s the least of the problem. It is hypergolic with every known fuel, and so rapidly hypergolic that no ignition delay has ever been measured. It is also hypergolic with such things as cloth, wood, and test engineers, not to mention asbestos, sand, and water –with which it reacts explosively. It can be kept in some of the ordinary structural metals — steel, copper, aluminum, etc.  — because of the formation of a thin film of insoluble metal fluoride which protects the bulk of the metal, just as the invisible coat of oxide on aluminum keeps it from burning up in the atmosphere. If, however, this coat is melted or scrubbed off, and has no chance to reform, the operator is confronted with the problem of coping with a metal-fluorine fire. For dealing with this situation, I have always recommended a good pair of running shoes.

Note that two chemicals which are hypergolic will catch fire and burn spontaneously  when brought into contact with each other. I learned this a few years ago in the process of writing a paper describing observations of the water left in the atmosphere by large rocket launches. The Russian Proton heavy launcher uses a hypergolic fuel/oxidiser pair, unlike the Space Shuttle, which burned liquid oxygen and liquid hydrogen. On the subject of fuels to go with liquid oxygen, Dr. Clark writes:

… we did some studies for Princeton, using LOX and pure USP type drinking alcohol — not the denatured stuff. The only difference we could find was that it evaporated a lot faster than denatured alcohol when a sailor opened a drum to take a density reading. We had some very happy sailors while that program was going on.

A final item of interest is his description of the early days of scientific computing

And there is one disconcerting thing about working with a computer–it’s likely to talk back to you. You make some tiny mistake in your FORTRAN language — putting a letter in the wrong column, say, or omitting a comma — and the [IBM] 360 comes to a screeching halt and prints out rude remarks, like “ILLEGAL FORMAT,” or “UNKNOWN PROBLEM,” or, if the man who wrote the program was really feeling nasty that morning, “WHAT’S THE MATTER STUPID? CAN’T YOU READ?” Everyone who uses a computer frequently has had, from time to time, a mad desire to attack the precocious abacus with an axe.

Computers have changed a great deal more than rockets in the years since 1972; the laptop I write this on has about 1000 times more memory than a typical IBM 360 But they can still provoke that violent urge.

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