Books You Should Read: IGNITION!

Isaac Asimov described the business of rocket fuel research as “playing footsie with liquids from Hell.” If that piques your interest even a little, even if you do nothing else today, read the first few pages of IGNITION! which is available online for free. I bet you won’t want to stop reading.

IGNITION! An Informal History of Liquid Rocket Propellants is about how modern liquid rocket fuel came to be. Written by John D. Clark and published in 1972, the title might at first glance make the book sound terribly dry — it’s not. Liquid rocket fuel made modern rocketry possible. But most of us have no involvement with it at all besides an awareness that it exists, and that makes it easy to take for granted.

Most of us lack any understanding of the fact that its development was the result of a whole lot of hard scientific work, and that work required brilliance (and bravery) and had many frustrating dead ends. It was also an amazingly dangerous business to be in. Isaac Asimov put it this way in the introduction:

“[A]nyone working with rocket fuels is outstandingly mad. I don’t mean garden-variety crazy or a merely raving lunatic. I mean a record-shattering exponent of far-out insanity.

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.”

At the time that the book was written and published, most of the work on liquid rocket fuels had been done in the 40’s, 50’s, and first half of the 60’s. There was plenty written about rocketry, but very little about the propellants themselves, and nothing at all written about why these specific substances and not something else were being used. John Clark — having run a laboratory doing propellant research for seventeen years — had a unique perspective of the whole business and took the time to write IGNITION! An Informal History of Liquid Rocket Propellants.

Liquid rocket propellant was in two parts: a fuel and an oxidizer. The combination is hypergolic; that is, the two spontaneously ignite and burn upon contact with each other. As an example of the kinds of details that mattered (i.e. all of them), the combustion process had to be rapid and complete. If the two liquids flow into the combustion chamber and ignite immediately, that’s good. If they form a small puddle and then ignite, that’s bad. There are myriad other considerations as well; the fuel must burn at a manageable temperature (so as not to destroy the motor), the energy density of the fuel must be high enough to be a practical fuel in the first place, and so on.

The actual process of discovering exactly what materials to use and how precisely to make them work in a rocket motor was the very essence of the phrase “the devil is in the details.” For every potential solution, there was a mountain of dead-end possibilities that tantalizingly, infuriatingly, almost worked.

The first reliable, workable propellant combination was Aniline and Red Fuming Nitric Acid (RFNA). “It had the one – but magnificent – virtue that it worked,” writes Clark. “Otherwise it was an abomination.” Aniline was difficult to procure, ferociously poisonous and rapidly absorbed through skin, and froze at an inconvenient -6.2 Celsius which limited it to warm weather only. RFNA was fantastically corrosive, and this alone went on to cause no end of problems. It couldn’t be left sitting in a rocket tank waiting to be used for too long, because after a while you wouldn’t have a tank left. It needed to be periodically vented while in storage. Pouring it gave off dense clouds of remarkably toxic gas. This propellant would go on to cause incredibly costly and dangerous problems, but it worked. Still, no one wanted to put up with any of it one moment longer than they absolutely had to. As a result, that combination was not much more than a first step in the whole process; there was plenty of work left to do.

By the mid-sixties, liquid rocket propellant was a solved problem and the propellant community had pretty much worked themselves out of a job. Happily, a result of that work was this book; it captures history and detail that otherwise would simply have disappeared.

Clark has a gift for writing, and the book is easy to read and full of amusing (and eye-widening) anecdotes. Clark doesn’t skimp on the scientific background, but always in an accessible way. It’s interesting, it’s relevant, it’s relatable, and there is plenty to learn about how hard scientific and engineering development actually gets done. Download the PDF onto your favorite device. You’ll find it well worth the handful of evenings it takes to read through it.

38 thoughts on “Books You Should Read: IGNITION!

  1. an interesting side note would be the fact that chlorine triflouride was briefly considered as an oxidizer in liquid rocketry. It didn’t take long for the “outstandingly mad” engineers to realize that using this oxidizer was TOO insane, even for them.

    1. Hilariously, the propellant community’s main objection seemed to be that there was no fuel of equivalent ferociousness and usefulness to go with it and make it worth all the other hassles.

    2. I like the part on that where it was thought it could safely be stored in stainless steel containers, until it showed that the non-oxidizing properties of stainless steel allowed the Chlorine Trifluoride to slowly etch its way through. By the time a cask of it split open and the stuff ate through several feet of a concrete floor and the gravel below, they had several tank cars of the stuff to deal with.

      The best tank materials to hold it proved to be ordinary metals. Carefully prep the tank with Fluorine to produce an oxide film on the surface and it could contain Chlorine Trifluoride. Just don’t scratch the coating!

  2. It’s a good book and the writing style is amusing and informative. Even if your not super into chemistry, it’s written in a way that still makes a good story without needing to understand the details(but you also get the details if you want them:).
    He’s got a little bit of an ego and it comes through but being one of a small group of people who got to do a bit of everything it’s deserved. Plus if you write a book, you get to big note yourself a little. :)
    My only disappointment is that it wasn’t written about 5-10 years later when the secret acts and such expired and could be published as well as the final stage of liquid fueled development that has basically stalled compared to those days.

      1. I also liked his description of how ignition delays of different substance combinations were measured and how the test setups ran the entire spectrum of complexity. “The simplest tester consisted of an eyedropper, a small beaker, and a finely calibrated eyeball”

      1. I’ve self published (not through Amazon) five books that I’ve written. If the rights to publish it in hard cover were clear and there were no legal obstacles it might take a week or so to make it available, but no more than that.
        It’s really no big deal once you’ve been through it a couple of times.

    1. Yeah, I noticed this when editing the article. Was thinking “why didn’t he link to the hardcopy”.

      This is a really great thing about the digital age — you would have waited ages for inter-library loan if you wanted to read this but many more people can benefit since it’s available online. I wish this was true for all books but that’s another can of worms (just ask Google about their effort to digitize everything).

  3. “The combination is hypergolic; that is, the two spontaneously ignite and burn” — some fuels were hypergolic- others were just cryogenic and difficult to store— Though it’s interesting to note all the poisonous rocket parts downrange of the Baikonur Cosmodrome in Kazakstan due to nasty fuels.

  4. I like all the stuff on using boron in rocket fuels. It makes an ideal addition due to its high mass which increases the specific impulse, unfortunately every attempt at using any compound containing boron failed due to it gunking up the combustion chamber and/or throat of the test engines, often to the point of choking it off completely and causing the engine to explode or (best case) just stop working due to being clogged with sticky goo.

    If boron could be tamed as a rocket fuel additive, that would be very useful to present day space launches. Hydrogen’s problem as a fuel is it’s so light, which is why rockets require so much of it. A heavier fuel with the same energy potential would require smaller and lighter tanks.

    Part of what Clark worked on was fuels for military aircraft missiles. The fuels needed to have a high energy density in order for missiles to be small enough for an airplane to carry *and* for the missile to have a useful range *and* the fuel had to be safe (enough) to handle *and* it had to be stable for long term storage in a range of temperatures from below freezing to soaking in hot sun.

    Solid fuels for air to air missiles are so much more convenient. Freezing isn’t a problem because the fuel is supposed to be solid. It doesn’t have to be stored in tanks or pumped and it can sit there in a missile hanging under a wing for months without a problem. Not going to corrode a hole in a tank then spill across the ground.

    1. later they figured that it would be even better if the missiles didn’t have to carry all its working mass and air augmented rocketry was born.

      there is of course some confusion surrounding modern missiles but a few have directly admitted to using air augmented rockets, specifically the meteor used by sweden.

  5. I don’t know about the rest of you but just the name Red Fuming Nitric Acid has about the same sense of safety as Angry Penis Eating Spider, I guess rocket chemists had to be a little crazy. By they way do the Russians still use Angry Penis Eating Spiders in their rockets?

  6. I’m lucky enough to have had a hard copy GIVEN TO ME(!!!!) a few years back. I’ll leave it for my kids to auction off on FutureBay. The story on pp 28-29 is an absolute scream; “Howard Streim opened his mouth to protest, but as he said later, ‘I saw that dog-eating grin on Doc’s face and shut it again,…’ ” The final treatment of the table had me laughing hard enough to bring tears.

  7. Been meaning to read this for a while. Anybody know if there are any audiobook versions available? I have an hours drive into work where I like a good audiobook to listen to. I had a google but couldn’t come up with anything.

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