August 08, 2005
Monday Musing: Rocket Man
It has never been fully clear to me why rocket science has become such a popular trope for intellectually challenging activity. Brain surgery makes more sense to me as a metaphor (as in, "It ain't brain surgery, you know!") since it is rather obviously very intricate, requires dexterity in addition to knowledge, decades of training, etc. On the other hand, at least on the surface, what could be simpler than a rocket? Take a cylinder, fill it with a flammable material, leave one end open, and set that end on fire. The expanding burning material will escape out the end, pushing the rocket in the opposite direction by Newton's third law. That's it. (A bullet could be considered a small rocket, I suppose.) Moreover, say you are going to the moon in your rocket: all you need to do to calculate the correct trajectories, orbits, etc., is Newtonian mechanics from a few hundred years ago. You needn't worry about electro-magnetic or nuclear forces, just good old gravity. There are no quantum or relativistic effects to be taken into account, no superconductivity, nothing fancy. A bit of chemistry (for the fuel) and classical phycics will do just fine. Of course there's a bit more to it, but it must be the irresistably romantic vision of our sailing starward into space that gives rockets their public fascination, however superficial. (Please, no phallo-Freudian explanations in the comments area.)
Quick, name a famous rocket scientist! Did you think of Robert Goddard? That's good. Yes, Goddard has come to be known as the "father of modern rocketry." Who else? Maybe Wernher von Braun? Yep, he's the German guy responsible for the V1 and V2 rockets before eventually settling in the United States and developing many of America's cold war-era ICBMs, so he has a bit of a mixed reputation here, at least morally speaking. (I suppose inspiring Thomas Pynchon to write Gravity's Rainbow also counts as a sort of achievement!) If you can think of any others, you're doing a lot better than most people. Rocket science hasn't made too many individuals famous, the way, say, quantum physics has. There aren't many popular books about it either. So, today, I'm going to give you a third name to remember: Arch Chilton Scurlock.
Full disclosure: for years, one of my dearest friends (and my wife's maid-of-honor at our wedding) has been Margy Scurlock, Arch's youngest daughter, and through her I also knew Arch and his charming wife Nancy. (My wife Margit and I spent our wedding night in Arch's amazingly beautiful suite at the Pierre Hotel in New York City. Thanks again, Margy!) True to the stereotype (despite my puzzlement over it) of rocket scientists, he was one of the brightest, most vivacious, and genuinely interesting men I have met. Not only was Dr. Scurlock personally responsible for some of the most astounding advances in rocketry in the 20th century, he was also a remarkably astute businessman, and has even been called the Bill Gates of his day. But let me try to tell his story chronologically.
Arch Scurlock was born in 1920 in Beaumont, Texas. His father served as the district attorney of Jefferson County. His maternal grandfather was senator Horace Chilton (Dem-Texas), whose own grandfather was Thomas Chilton, anti-Jacksonian congressman from Kentucky in the 1830s. Despite this distinguished political background, Arch found that his own passion was science, and he obtained a bachelor's degree in chemical engineering and physics from UT Austin. He excelled in college, and was even named "best all-around intramural athlete" in his senior year. (He is supposed to have had a "lightning squash game," but I never had a chance to play him. Apparently he wasn't too bad at boxing either.) He went on to MIT and received a master's degree and then a Ph.D. in chemical engineering. I seem to remember that he once told me that he also held a master's degree in meteorology from the University of Chicago. In any case, during WWII, Arch was a Navy meteorologist and also flew reconnaissance missions in the South Pacific.
After the war, Dr. Scurlock joined Engineering Research Associates in Arlington, Virginia. This was a company staffed mainly by cryptographers who had broken the "Purple Cypher," the main Japanese code during the war. William C. Norris, who later founded Control Data Corporation, was also there at the time. The company had a contract from the Office of Naval Research to study ram jets, pulse jets, and solid and liquid propellents. After a short while there, on January 24, 1949, Dr. Scurlock founded the Atlantic Research Corporation (ARC--yes, the first three letters of his name) with $1,000 in capital, and a three-month research contract from Princeton University. ARC would soon become one of the fastest growing science and engineering companies in the world, eventually responsible for the production of dozens of types of rockets (including the Minuteman, the Tomohawk Cruise Missile, and the TOW, Maverick, and Stinger missiles). The company also diversified into very disparate fields, such as producing the inflators for automotive airbags. ARC's main innovations and work, however, was in producing solid rocket fuels. Dr. Scurlock could be called the father of solid rocketry. (The space shuttle, for example, has one liquid fuel tank, and two solid rocket boosters.)
Some years ago, Dr. Scurlock invited a few of Margy's friends to the 21 Club for her birthday. Over pre-prandial drinks, I asked him for an example of something interesting that he had discovered in rocketry. He thought about it for a bit, ordered another drink, then with characteristic modesty said, "Many discoveries in science are accidental. You are looking for one thing, and find another. Think of Alexander Fleming's discovery of Penicillin. I'll give you a small example from my field." He then went on to describe one of the ways in which he solved the problem of burn-rates in solid rocket fuel.
Let me now, in turn, try to explain to you what he told me: the total energy stored in the fuel of a rocket is known as its impulse, and is measured in pound-seconds. This means X pounds of thrust delivered for Y seconds. So, for a fuel formulation that delivers 10,000 pound-seconds of impulse, this could mean a thousand pounds of thrust for 10 seconds, or 100 pounds of thrust for 100 seconds, etc. The problem was that the fuel they were working with at the time, something called Arcite, does not burn fast enough to produce the required thrust. In other words, they needed to increase the thrust (pounds) and decrease the burning time (seconds) for Arcite. While thinking about the problem, Dr. Scurlock and others were doing some preliminary measurements of flame temperatures of various propellent formulations in the laboratory. They were using thermocouples (bi-metallic filaments) embedded in the fuel grains to do this. Now, the way that a rocket fuel grain burns is this: once ignited, the flame at the end melts the solid fuel just behind it, which then ignites in turn, melting the fuel behind it, etc. What Dr. Scurlock noticed was, that the fuel was burning faster with the thermocouple wires embedded in it. He immediately realized that if he inserted a wire made of a material which conducts heat well, like copper or silver, say, into the middle of the rocket grain, then this wire will conduct heat from the flame to the material behind it much faster, melting and igniting it. What results is a cone shape, with the point of the cone pointing inwards along the wire toward the unburned fuel. It would look something like this:
Notice that while normally the area of the fuel which is burning is a circle at the end with an area of ΠR2, with the embedded wire it is a cone shaped area with a much larger surface. Suppose the cone extends inwards into the fuel to a length twice the diameter of the rocket. Then, in terms of the radius, R, of the rocket cylinder, the surface area of the burning cone shaped area of the fuel would be:
Surface Area = ΠR sqrt (R2 + (2D)2) = ΠR sqrt (R2 + (4R)2) = ΠR sqrt (17R2) = ΠR2 sqrt (17)
Since the square root of 17 is between 4 and 5, the surface area of the fuel that is burning at a given time in this way is 4 to 5 times greater than without the embedded wire. And indeed, after experimenting with various materials and configurations, Dr. Scurlock was able to achieve burn rates five times faster than before, which is what they needed for the Arcite fuel. By the way, the cone is just molded into the fuel grain at the beginning, allowing high thrust right from ...3, 2, 1, ignition. Such are the little breakthroughs and increments with which even rocket science is normally done.
The December 5, 1960 issue of U.S. News and World Report reported the upcoming inauguration of JFK, remarking that he "moves into the White House at 43 to replace a president aged 70," and then moved on to note that the young are replacing the old in business as well, like Arch Scurlock, age 40, who "heads the fast-growing Atlantic Research Corporation in Alexandria, Virginia, a major producer of solid fuels for space vehicles." In 1968, Dr. Scurlock went on to form Research Industries, a venture capital firm which invested in small startup companies in the aerospace, defense, and textile industries, including Halifax Corporation, an engineering firm in Virginia. Dr. Scurclock's obituary in the Washington Post notes that "At his death, he was chairman and chief executive of Research Industries and board chairman of Halifax. He had seen Halifax through rough moments, including a scandal in the late 1990s involving a former controller who pleaded guilty to embezzling millions from the company." Arch Chilton Scurlock died on December 9, 2002, aged 82. Knowing how much I admired him, Margy passed along various personal items of his to me as mementos, including the hand-tailored blue suit he is wearing in the profile picture above (by a weird coincidence, we happened to be the exact same size), and this globe which he kept on his desk. He is missed.
I think I'll give Elton John's old lyricist Bernie Taupin the last word:
And I think it’s gonna be a long long time
Till touch down brings me round again to find
I’m not the man they think I am at home
Oh no no no I’m a rocket man
Rocket man burning out his fuse up here alone
Have a good week!
[Note: I got much information about Arch and ARC from Philip Key Reily's book The Rocket Scientists.]
My other recent Monday Musings:
Francis Crick's Beautiful Mistake
The Man With Qualities
Special Relativity Turns 100
Vladimir Nabokov, Lepidopterist
Stevinus, Galileo, and Thought Experiments
Cake Theory and Sri Lanka's President
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