Blog All Dog-eared Pages: Ignition! by John D. Clark

I found this in my drafts in the recent blog revamp. “Ignition! An Informal History of Liquid Rocket Propellants” by John D. Clark is book I keep recommending to people. For something that sounds dry and technical, it’s actually really enjoyable and readable.

I think I stopped making notes as I was too engrossed in it. However, hopefully these notes will pique your interest and you’ll visit this Hackaday post which has a link to an online version.

Page xii

For I have discovered that [the professional rocket engineer] is frequently abysmally ignorant of the history of his own profession, and, unless forcibly restrained, is almost certain to do something which, as we learned fifteen years ago, is not only stupid but is likely to result in catastrophe.

Page 14

The discovery of hypergolicity was of major importance. Running a rocket motor is relatively easy. Shutting it down without blowing something up is harder. But starting it up without disaster is a real problem.

Page 59

By the time these groups were finished (all of the work was published by 1955) there was nothing worth knowing about nitric acid that hadn’t been nailed down. Thermodynamics, decomposition, ionetics, phase properties, transport properties, the works. Considering the difficulties involved in working with such a miserable substance, the achievement can fairly be classified as heroic.

Page 73

All this sounds fairly academic and innocuous, but when [chlorine trifluoride] is translated into the problem of handling the stuff, the results are horrendous. It 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.

Page 162

The job of the [test methods] committee was to examine all the methods used, to pick out those which gave more or less reproducible results, or to talk people into developing such methods, then to standardize these, and finally to try to persuade the people in the field to use those methods.

Page 163

[the OM drop weight tester] was, and is, quite a satisfactory instrument once you got used to its little foibles. For instance, it has to be on a really solid foundation if you hope to get reproducible results. We ended up with the instrument bolted to a three-foot square of three-inch armor plate, which was in turn bolted to a six-foot cube of concrete which rested on bedrock —granite. That way, it worked fine.

Page 165

But detonation traps aren’t always the complete answer. We discovered that when, in the summer of 1960, we tried to fire a 10,000-pound thrust Cavea B motor. We didn’t have Mike’s trap at that time, so we inserted a battery of sixteen 0.25-inch loop traps in the line. Well, through a combination of this and that, the motor blew on startup. We never discovered whether or not the traps worked —we couldn’t find enough fragments to find out. The fragments from the injector just short-circuited the traps, smashed into the tank, and set off the 200 pounds of propellant in that. (Each pound of propellant had more available energy than two pounds of TNT.) I never saw such a mess. The walls of the test cell—two feet of concrete—went out, and the roof came in. The motor itself—a heavy, workhorse job of solid copper— went about 600 feet down range. And a six-foot square of armor plate sailed into the woods, cutting off a few trees at the root, smashing a granite boulder, bouncing into the air and slicing off a few treetops, and finally coming to rest some 1400 feet from where it started. The woods looked as though a stampeding herd of wild elephants had been through.