Young Men and Fire (28 page)

Albini was once telling me about one of his projects, which had primarily to do with predicting the speed of missiles, both those missiles made by others which he had only seen and those he was recommending be built. His comment at the end was that “it’s a lot easier to predict the speed of a missile than that of a wildfire.” Generally, he said, “it’s easier to predict the behavior of objects made by man than natural objects.” Having lived long enough to absorb a considerable number of lumps and bumps from whatever hovers around outside under the name of “nature,” I said to him, “That shouldn’t have surprised you.”

“No,” he said, “it didn’t. Long ago a science teacher told me, ‘The universe, she is a bitch.’” Several times since, I have thought about this sentence. It’s probably right.

W
HEN WE FIRST SAT DOWN
at the long conference table in the lobby, I was puzzled about what I must have done long ago that had led me in retirement to a confrontation with two mathematicians and two wind tunnels. Some of the explanation had to be personal. As a boy I had to confront dangers of the forest that ever since have left me dreaming I am on a fire-line and the fire is about to jump the line and will if I wake up, so I try not to. My wife’s ashes, scattered
on the mountain she named after herself, undoubtedly direct me back to the scene of the great tragic forest fire falling in her line of vision if she can still see me. It is probably less important that when I first saw the Mann Gulch fire it was still burning through rocks like snakes on fire. In my dream from which I cannot quite awake I still sometimes see a deer with all its hair burned off except what rims its eyelids. There is no use trying to eliminate all that is personal in order to be scientific. The long conference table at which the four of us sat was big enough to take in everything and long enough to seat eighteen or twenty. Perhaps the empty spaces had been reserved for the dead Smokejumpers and Gisborne. They belonged there but were never there, but they were never far away.

Although I have had few school courses in science, I have always tried hard to be accurate with facts. In my family we were expected to be, and, in addition, I found that being accurate with facts was a kind of game and I liked to play it. Later, when I came to know some great scientists, I found that to them science was a kind of game on a grand scale. The game Laird and I hoped to play with the mathematicians was to match our analysis of the fatal race between men and fire with their mathematical study of the same race. If nothing else, the results might tell us whether the Smokejumpers had much of a chance against this fire. Critics have always talked loosely about this or that tragedy being “inevitable,” but I seldom thought any of them were, and I also thought it would make a lot of difference to everyone involved if this tragedy was.

Mathematicians are very clear writers, as one should expect; their only prose weakness, also to be expected, is that they write for each other. So it turned out to be helpful to have figured out ahead of time what some of their main plays were going to be, because then it was not necessary to know, at least immediately, the meanings of all the words. As theoreticians, they start by finding it odd that, although men had been fighting fire long before they knew how to light one, they haven’t formed a theory of why it spreads. I thought this odd myself
and oddly applicable to me, so I made an effort to learn about some of the first mathematicians to take up this problem. Evidently, W. R. Fons in 1946, basing his work on a theory that a spreading fire is in fact a series of ignitions, was the earliest to make a mathematical model of a fire. All the other mathematical modelers of fire whom I read also started by looking for a definition of fire spread never before given, and they ended with a definition which, when reduced to its main simplistic terms, says that a spreading fire is a series of little fires. Just so we wouldn’t glide by the center of this analysis with a few simplistics of mine, I asked Albini if he would write down an explanation of the process of fire spread for me and anyone who ever reads about the Mann Gulch fire:

As the fuel burns at a point just ignited, it releases the energy that the plant has gathered from the sun and stored up as plant tissue. The tissue decomposes as it is heated by the fire (called “pyrolyzing”), releasing combustible gases that burn as a free flame. This in turn heats the remaining solid matter to drive off more combustible gas…. Much of the heat is carried away as hot gas, up into the smoky buoyant plume above the fire. But much, too, escapes as radiant energy from the bright flame, returning to the form in which it was released from the sun and captured by the living plant. In the form of radiation, the energy flees with the speed of light and travels in straight rays until absorbed by matter. When it is absorbed, this energy raises the temperature of the matter which has captured it. Fine, dry plant components very near the flame are thus heated very quickly to the temperature at which they must decompose, giving off combustible gases that are in turn ignited by the nearby flame. In this way fresh fuel is added to the fire, to replace that just consumed in the flame. So the fire spreads.

Therefore, when Dodge spoke of a solid “wall of flame” behind him, 250 to 300 feet deep, he was speaking figuratively as a poet, as most of us do. What was behind him were hundreds of thousands of little fires multiplying so fast that only a computer could keep up with them.

I had to walk around this explanation of the process of the spread of wildfire several times before going on, because
everything ahead comes from it. The mathematical analysis of wildfire requires a structure of thought, not just some close observations of smoke and flame, and this structure is spoken of as a “philosophy” by the mathematicians. As a philosophy it has a center from which everything flows, and the center is a definition and the definition turns out to be this explanation of fire spread. If a spreading fire is a bunch of little fires becoming many more little fires, then a lot of counting has to be done to make a study of it. Think of what a lot of counting of a lot of pine needles had to be done to come to the following conclusion:

These equations show that the rate of spread in our ponderosa pine needle fuel beds decreased by 4.23 percent for each 1-percent increase in fuel moisture. Rate of spread in white pine needle fuel beds decreased by 4.55 percent for each 1-percent increase in fuel moisture. If the effect of moisture remains linear as moisture content increases, the ponderosa pine needles would not sustain a rate of spread at a fuel moisture of 24 percent in the still air environment. Similarly, the limit for white pine needles would be 22 percent. (Richard Rothermel and Hal E. Anderson, “Fire Spread Characteristics Determined in the Laboratory,” U.S. Forest Service Research Paper)

It also helps to remember what this definition looks like when it is in operation in the Fire Lab: a wind tunnel with a computer nearby. What you don’t see is what is installed inside the computer—the structure of thought being outlined here, including of course as its centerpiece the quantitative definition of the spread of wildfire. “Facts” Laird and I gave the mathematicians about the Mann Gulch fire that seemed worth considering would be given to the computer, which would consider them within the structure of thought it had been given. I suppose it is something like a creamery—a lot of things are churned around in it, and some are supposed to rise to the top as butterfat.

As the structure of thought has, as its centerpiece, a definition, so the definition of the spread of wildfire has fuels as its centerpiece. In the analysis of fire spread with fuels at the
center, fuels are first analyzed as particles, some of the most important factors being their size (“the ratio of surface area to volume”), heat of combustion, and ash content. Nothing is more important about the arrangement of particles than their compactness, with the limitations of being so close together as to stop a fire or so far apart as not to let it get started. Once started, however, these combustibles are “whipped,” “smothered,” or “kept alive” by such environmental factors as the wind velocity, the slope of the ground, and the moisture content. Just from knowing that usually the height of the forest fire season in Montana is August, when it is hot, dry, and windy, we know something of the varying influence these forces can have on any fire or sector of it.

The pioneers of fire research, including Gisborne himself, had proceeded on the assumption that the science of fire spread could be discovered by repeated trial burns using fuel samples gathered from all over the country. Two big flaws appeared in this method that kept it from producing accurate science or useful information. As discussed before, it did not produce “controlled experiments” with built-in assurances that what was meant to be tested was in fact being tested and hence could be repeated and used as data for statistical inferences. Another difficulty was that, unless you have some good idea of what you are looking for and how to find it, you can approach infinity with nothing more than a mishmash of little things you know about a lot of little things—certainly with nothing that could have been put in a hand calculator and dropped with Wag Dodge into Mann Gulch to avert his tragedy.

It is at this point that “fuel models” become necessary and make their appearance. They are fashioned roughly like ready-made suits of clothes. It’s a case of picking the fuel model you think will come closest to fitting, having a few adjustments made in the sleeves and shoulders and always in the legs, putting the model and the adjustments in the calculator, and watching the predictions come out almost instantly, usually with a margin for error. But mathematical tailors improve
with practice, this experiment the four of us were conducting being something of a test as to how much.

There were twenty-six years between the first scientific concept of the spread of wildfire and its general availability as a field of thought with practical applications (the result in 1972 of Rothermel’s
Mathematical Model for Predicting Spread and Intensity of Fire in Wildland Fuels
). Seven years later Robert Burgan of the Fire Lab developed a hand-held calculator program that could predict fire spread in the field. When thought has moved from general concept and definition to practical application in the field, thought has taken shape and become a field of thought.

At the time of our talks around the conference table in the lobby, thirteen models of different forest fuels were ready for use in the field: three for grasses, four for shrub, three for timber, and three for slash. As for environmental factors influencing burning fuels, coefficients have been developed to measure their effects on fire behavior. A coefficient shows the relationship between two factors. Here, for example, is one that Rothermel had already established and that will certainly be transferred back to Mann Gulch for a scientific as well as a simple human understanding of its tragedy: “The percentage increase in the spread rate [one factor of a fire] varies in proportion to the square of the percent slope [an environmental factor influencing the fire].” This is a tragic statement; it was very steep where they died.

N
EAR HERE A CHANGE STARTED
occurring in our procedure around the long conference table. The grammatical structure of our sentences changed places across the table. It had started with flurries of interrogative sentences ending with rising inflections from Laird’s and my side, which were followed in a much lower key by a patient monotone of declarative sentences from the mathematicians, who knew
they would have to repeat and explain their answers. The first movement of this grammatical structure was expressive of Laird’s and my attempts to get into our heads, however fleetingly, what had been solidly installed in the computer, a “philosophy of wildfire.” But as the grammatical structure veered around, Rothermel and Albini were asking the questions, still patiently, and Laird and I were giving the answers, still flutteringly with a hurried exchange of nondescript prose before one of us uttered the agreed-upon answer. Much of this would be put back in the computer to be combed over by what the computer knew about fire spread. I believe the trade name for this is “input,” a name I suppose one has to accept for an aftereffect of fire. But it also is to be taken as a sign that we were nearing the final step back to Mann Gulch—getting its exact “facts” in order to pick the right fuel models and sets of environmental factors and then make the adjustments needed for a “close fit.”

Many times just the practical problems of gathering accurate data on local fire conditions can be as difficult and complex as the mathematics that follows. In this quest to seek for scientific as well as human causes of a tragedy, the speed of the wind was very important, so it is not a diversion to consider here the kind of information we tried to dig up and relate there at the conference table in order to determine the probable wind velocity (or velocities) that powered the fire on its tragic course. The data we needed came from three different sources: official weather reports, testimony of those present at the fire or closely connected with it, and our general knowledge about the behavior of winds on large fires, especially on fires that are blowups. We knew from the dispatcher at the Missoula base and from survivors that air conditions at the time the plane left Missoula were turbulent and that the plane ride to the gulch was so rough that one jumper became too sick to jump and the others felt ill; that the wind velocity at the gulch was so great that the plane dropped its cargo from an unusually high altitude to avoid entering the narrow, windswept canyon; and that the cargo when dropped was scattered
over an unusually large area and took a fatally long time to collect. We knew the official wind velocity at Helena at the approximate time of the tragedy (at six o’clock in the evening it was nineteen miles per hour), but Helena is more than twenty-five miles away, on the side of a wide valley, whereas Mann Gulch is a narrow notch that connects with the twisted canyon of cliffs of the Missouri where winds are compressed and are often substantially higher. From our common experience with forest fires, we knew long before Mann Gulch that big fires add to their own wind velocity by the whirling motion set up when cooler air rushes into the lower part of the fire to replace the hotter, lighter air that has risen and escaped. We knew from several sources that this particular fire was a blowup, with fire whirls throwing burning cones and branches across the gulch and starting spot fires that soon were racing upgulch toward the crew.