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Jack Crenshaw

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Jack W. Crenshaw is an aerospace and embedded systems engineer living in the Tampa Bay area of Florida. He has over 40 years of experience in the development of systems and software for both aerospace and industrial systems, and he did much of the early trajectory analysis work for Project Apollo. Since then, he has developed simulation, analysis, and real-time embedded systems for everything from the Space Shuttle manipulator arms to satellite tracking antennae to medical patient monitors. His specialty is the application of advanced methods of math and physics to practical use in working, real-world systems.

Crenshaw holds a Ph.D. in Physics from Auburn University. He is currently a Senior Principal Design Engineer for Alliant Techsystems, Inc., a contributing editor and columnist for Embedded Systems Programming magazine (a Miller Freeman publication), and president of Crenshaw Technologies, a consulting firm. His first book, "Math Toolkit for Embedded Systems," will be released in the fall of 1999.

His hobbies include powerboats, racing cars, electronics, and homebrewed computers. In his "spare" time, he helps raise wild and domestic orphan animals, and can usually be found at home with an opossum asleep in his shirt, or a baby chick snoozing on his shoulder.

This interview took place between March and June 1999.

Your career is one of major support of this nation's space program. How would you answer the statement by some that there are enough problems left for us to solve on Earth before we go out into Space and expend precious resources?

The question answers itself. We have already been out into Space. Even as we prepared to attempt what was arguably the greatest and most noble achievement in human history, there were those who demanded, "Why should we spend billions to bring back a few rocks from the Moon, when we could be spending that money curing cancer, cleaning up the cities, and ending poverty, hunger, and ignorance?"

After Apollo, these naysayers had their way: the manned space program has been essentially halted. Plans for Mars missions, lunar colonies, and a space station were cancelled. The Space Shuttle, originally designed to SHUTTLE people and materiel to the Space Station, now functions as the world’s most expensive launch platform for communications satellites, mainly because its true raison d'Ítre was never built.

So for the last thirty years, we’ve done it "their" way. We’ve spent literally hundreds of trillions of dollars trying to cure cancer, clean up the cities, and end poverty, hunger, and ignorance. What have we to show for it? Though great strides have been made in cancer treatment, the death rate remains essentially constant. Our cities are dirtier and more dangerous than ever, and poverty, hunger, and ignorance remain. Serious social and medical problems, such as AIDS, Ebola virus, violence, racial hatreds, and war, remain and continue to escalate.

Jesus said, "The poor will be with you always." How right he was. If we wait for all other ills of society to be cured, before we venture into space, we will remain glued into place, until we are as poor in spirit and morals as we are financially.

Could you provide us with some details about your work in the space program? I understand that you performed the trajectory analysis for the Apollo orbit to the Moon and back.

Crenshaw: All of my work on Apollo came in a frenetic four-year period, from 1959 through 1963. It was in 1959 that I began work for the Theoretical Mechanics Division at NASA, at Langley Research Center. This was just shortly after NASA was formed. Shortly after I arrived there, a paper came out of the think tank, Rand, Inc., describing a class of lunar trajectories called free-return, circumlunar trajectories – the now-familiar figure-8 paths. It was immediately obvious that this class of trajectories was the only reasonable way to go to the Moon and back. We began studying them intensely, using first a two-dimensional simulation of the restricted three-body problem, and later a 3-D, exact simulation.

In those days, we didn’t have spreadsheet programs to draw graphs for us; we had to draw them ourselves. As low man on the TMD totem pole, I got elected to plot the results of parametric studies. That task worked in my favor, though, because I gained an understanding of the physics of the problem, and the relationship between parameters, that I don’t think I would have gotten, otherwise. I wasn’t content to just make runs and plot curves; I wanted to UNDERSTAND what was going on, and I think that put us ahead of the Rand guys.

My boss and I published a paper in 1961, which was the second paper published on circumlunar trajectories. We also developed quite a number of rules of thumb, approximations, and "patched conic" methods that allowed us to study circumlunar trajectories without spending tons of money for computer time.

At the time, we weren’t thinking of Project Apollo. In fact, I had never heard of it. We had plans to send a "Brownie" camera around the Moon before 1965, using NASA’s solid-state, Scout research vehicle. When Scout’s projected payload at the Moon went from a few hundred pounds, through zero and negative, those plans were abandoned. However, the effort left us more than ready for Apollo when it came along.

Next, I began studying the problem of steering the spacecraft, i.e., midcourse corrections. We were all pretty dismayed by the great sensitivity of the circumlunar trajectory to errors in initial conditions, and we knew the accuracy of the Scout boost guidance was orders of magnitude too low. Midcourse guidance would be essential. To my knowledge, my work on that topic was one of the earliest done, though I suspect the fellows from MIT, like Richard Battin, were studying the same problem. In fact, it was Battin’s seminal work, seeking a midcourse correction scheme for Apollo, that helped make the Kalman filter practical.

During this time, I also discovered a family of trajectories that were relatively insensitive to injection errors. These trajectories had a nominally vertical reentry. You see, for orbits as highly elliptical as translunar orbit, the perigee is almost totally a function of the angular momentum. The requirement that we return with essentially the same angular momentum as the original orbit implies that the passage past the Moon should not alter that momentum. To achieve this result requires very tight guidance.

The required angular momentum, translated to velocity at the distance of the Moon, works out to be around 600 f/s. This should not be altered if we expect to achieve the kind of grazing entry required for a manned mission. Suppose, however, that we design an orbit that leaves the Moon with zero velocity. Then it should reenter the Earth, with a vertical entry – fatal for astronauts, but not for instruments. Even if our errors impart as much as 600 f/s of unplanned velocity, we will still enter the Earth’s atmosphere and land, somewhere. If you don’t care where, this peculiar class of trajectories allows one to fly to the Moon and back, even with the crude guidance of the old Scout. Of course, the mission never flew, so the trajectory is now nothing more than a footnote to space history. But an interesting one, nevertheless.

In 1961 I moved to General Electric in Philadelphia, where they had landed a study contract for Apollo, and were also planning to bid on the hardware contract. I was responsible for all the generation of nominal trajectories for those efforts. I did similar stuff for lunar missions that never flew, or flew with radically altered plans; the names of projects Surveyor and Prospector come to mind.

I think I did some of my very best work at GE. Generating a lunar trajectory is not easy. The problem is a two-point boundary-value problem, complicated by the fact that both points (the launch and return sites) are fixed on a rotating Earth, and we have the "minor" midpoint constraint that the trajectory come somewhere near the Moon. We quickly learned that simply trying to guess at suitable launch conditions was a hopeless venture. Therefore a large part of my energies went into building quite a number of patched-conic approximations, programs to solve the complicated spherical trig, front-end and back-end processors, and "wrappers" for GE’s N-Body program. My crowning achievement was a fully automated program that required only the barest minimum of inputs, such as the coordinates of the launch and landing points, plus a few other things such as year of departure, lunar miss distance, and lighting conditions at both the Moon and Earth reentry. The program would then seek out the optimal, minimum-energy trajectory that would meet the constraints.

I was also asked to study the problem of returning from the Moon to the Earth. Thanks to my experience with approximate methods, I knew exactly how to do this: Give the spacecraft a tangential velocity of about 600 f/s, relative to the Moon. From that desired end, it’s fairly easy to figure out what sort of launch one needs at the Moon’s surface. We generated quite a number of trajectories, both approximate and exact, that effected the Moon-to-Earth transfer. As far as I know, they were the first such studies ever done.

During this same period, I was developing a method for computing nearly parabolic orbits. The classical two-body theory upon which all approximate methods are based has three distinct solutions, depending upon whether the orbit is elliptic, parabolic, or hyperbolic. The equations for the elliptic and hyperbolic cases all go singular for an eccentricity of one. Unfortunately, that’s exactly the kind of orbits involved in translunar missions. It drove both the computers and their programmers crazy, trying to solve problems so close to a singularity. I developed a set of power series solutions based on Herrick’s "Unified Two-Body Theory." Though Herrick’s original formulation was unsatisfactory (his functions required two arguments), it was a rather short step to replace them by new functions that used only one argument. Between 1961 and 1963, I published quite a number of papers on these functions, most of them internal to GE and widely distributed within NASA. I was also busily putting them to work in trajectory generators. Unfortunately for me, I never managed to get credit for them; you’ll find them today in Astrodynamics texts, called the Lemon-Battin functions.

In 1963 I spent nine months at GE’s Daytona Beach facility, studying the problem of how to abort from the lunar mission. At first glance, you might think nothing much can be done; once zooming towards the moon, you’re pretty much committed to continue. However, out near the Moon, the velocity relative to the Earth is rather low, and you have tons of available fuel for maneuvering, thanks to the need to enter and exit lunar orbit. Therefore, it’s theoretically possible during some portions of the mission to simply turn around and head back for Earth. In other phases, you can lower the trip time quite a bit, by accelerating either towards the Moon (to hasten the swingby) or towards the Earth. In my studies, I discovered yet another class of returns, in which you make no attempt to slow down, but simply deflect the velocity downwards enough to graze the Earth’s atmosphere. Aerodynamic braking does the rest.

All these abort modes ended up designed into the missions and programmed into the Apollo flight computers. Two of them – accelerating towards the Moon on the way out, and towards the Earth on the way back – were used to reduce the life-critical flight time during Apollo 13. If you watch the movie of the same name, you’ll hear discussions of Fast Return and Free Return trajectories, both of which I had a hand in designing.

Resonance: What was the most advanced computer used during Apollo? How does it compare with today's PCs?

Crenshaw: Most of our work was done on the IBM 70x series, from 702 through 7094. Later in the Apollo era, we had Univac 1108’s and 1110’s, and the CDC 6600. None of them, of course, could hold a candle to the modern PC with Pentium processor. I think their cycles times were all around a microsecond, which is equivalent to a 1 MHz clock speed; not even up to the smallest microprocessor of today. Memory was via magnetic cores, which were even slower. The IBM’s had a maximum of 32K RAM (but 36-bit words, not bytes). Nevertheless, the later processors, notably the Univacs and CDCs, were no slouch. Both had hardware floating point and long word lengths (CDC’s words were 60 bits long), so one could do some serious number crunching.

Despite their low performance, on paper, we got a lot of work out of those old machines. For those used to waiting 15 seconds for a Windows spreadsheet to even load, it’s difficult to imagine how much work a 1MHz computer can do when it’s running full tilt in machine language, not encumbered by bloated software, interpreted languages, and a GUI interface. I’m old enough to remember, and look back on those days wistfully.

Resonance: At the beginning of the Apollo program, where did you think we would be by the year 2000, lunar cities? Martian cities?

Crenshaw: Absolutely – all of the above. At the time Apollo was well along, it was tacitly assumed that we’d press right on to Mars. The trajectories were already designed, as was the booster, NASA’s Nova. It never occurred to us that the beginning was also the end. We never anticipated the Vietnam war, the Beat Generation, Flower Children, and the anti-science backlash.

I recall, in history class, reading about the huge gap – over a century – between Columbus’ discovery of the New World in 1492, and the first permanent settlement at Jamestown, in 1610. I could never understand the reasoning. Having discovered such a vast and rich natural resource, why would people wait a century to use it? Now, in hindsight, I guess I understand: Priorities change. If anybody had told me, back around 1964, that we’d have a similar hiatus after Apollo, I would have thought them completely mad.

We are now 30 years past the Armstrong-Aldrin moonwalks of 1969. What feelings do you have when you view the films of the Apollo astronauts walking on the Moon?

Crenshaw: Mostly sadness. It seems to me such a terrible waste. The Apollo launch complexes, built at such huge costs, sit on Cape Canaveral, slowly decaying back into dirt. Our abilities to repeat the feat get worse with every passing year. Worst of all, all that incredible effort, all that hard-earned knowledge, all those careers spent learning the skills, all those marriages, careers, and even lives sacrificed for the goal to make Apollo a success, are mostly gone. Most of us who worked on Apollo are either dead, retired, or senile now. The knowledge is gone, possibly forever. I’m one of the lucky ones; I was young enough when Apollo began to still be able to remember how to do it. Even so, too few remain who do. If, today, we were given another Presidential mandate to return to the Moon in another eight years, I don’t think we’d have a snowball’s chance in Hell of doing it. Even if we simply tried to build another Apollo/Saturn V system, with no changes at all, I still don’t think we could do it. Apollo brought together thousands of the country’s best minds, all concentrating on a single goal. It’s the kind of thing that comes along only rarely in history.

I hope I may be forgiven feeling a bit of personal loss as well. I devoted some good years to the effort of learning how to steer a rocket to the Moon and back safely. I still have that knowledge (much of which was never written down – we were too busy doing, to write) rattling around in my head. Over the last 30 years, I’ve hoped someone would ask me again to show them how to do it. No one has.

Resonance: Can you understand why some of the men who walked on the Moon chose very different occupations after their return to Earth? The most famous of these is Alan Bean who is now an accomplished painter.

Crenshaw: Well, after you’ve walked on the Moon, what do you do for an encore? Surely nothing else can compare to it for lifetime achievement. So you end up at age 40 or so, realizing that nothing else you do in your life is ever going to compare to that single week. I think that sort of feeling is what got Buzz Aldrin down. It’s a hard trick to top. Different people have different ways of dealing with that feeling; some of them healthy, some not so. Some, like John Glenn and Frank Borman, chose to set new, equally challenging goals. Others, having been through the high-stress, high-risk part of their lives, chose to sit back and take life easy. In the end, I think that, having viewed the Earth rising over the Moon’s horizon, it would be completely impossible to view one’s life on Earth quite the same as before. The experience must surely induce the ultimate mid-life crisis.

Resonance: Are you optimistic about manned space exploration in the next century?

Not immediately, but eventually. Sadly, I don’t think it will come in what’s left of my lifetime.

Sooner or later, I expect some future generation will manage to recover the same kind of enthusiasm we had. We grew up on science fiction novels and B movies, in a period close enough to World War II and its postwar optimism, to have retained that wide-eyed, the-future-is-unlimited attitude. Today’s youth are growing up on Star Trek, Star Wars, and exotic movie special effects. I’m hopeful that some day, they’ll manage to regain the gee-whiz enthusiasm that a spacefaring society needs.

I certainly see precious little of that attitude today, however. Today the world is too complex and dangerous, and people are entirely too focused on their own needs and wants, not enough on the future. Look at the wars and rumors of wars, the country’s internal battles over things like abortion, gay rights, civil rights, liberal vs. conservative agendas, etc., etc. Look at the polarization between races, between haves and have-nots. Look at hate crimes, school shootings, rampant drug abuse, AIDs, and all the other writhings and sufferings this country is currently undergoing. The current focus of this country is on social change and Political Correctness. I don’t see that changing any time soon, and I can’t see us regaining the will to go to space, until it does.

Resonance: You are described as the resident math guru for the company Embedded Systems Programming. What sort of work do you do there?

Crenshaw: I write a monthly column on embedded systems software issues, concentrating on those related to the application of heavy-duty math processing in real time. In a sense, the stuff I’m writing for ESP is much the same kind of thing that I did for NASA: Bring the power of advanced methods to bear on practical problems.

I also write occasional articles for the same magazine, as time permits. In the past, I’ve done articles on compiler construction, on vector and matrix math, on calculus and numerical methods, on control systems and filters, and on Fourier, Laplace, and Z-transforms. I have a couple of articles currently in the works, on Chebyshev polynomials and other error minimization methods, and on Kalman filters.

 Resonance: You are an expert on operating systems and compilers. Could you describe for us what are some of the key issues to be resolved in operating systems design? Compiler design?

Crenshaw: I guess I don’t see myself as, or claim to be, an expert in either area. I learned compilers mainly because they fascinate me. The idea that a mere human could write something as wonderful as a language translator struck me as near-magical. I tried for years to understand how they worked, reading every book I could find. But I never seemed to be able to break through the special language and notation that compiler texts feature. Finally, I did manage to break through the fog, and I was so excited, I wanted to tell everyone what I’d learned. I began a tutorial which still floats around the net, though it sort of bogged down around Chapter 16. Again, priorities change.

I’m fascinated by the low end of compilers: The Tiny C’s Small C’s, and assembler/compiler hybrids. It’s amazing how much can be done with a very small, perhaps inefficient, but still eminently usable, compiler. I have little or no interest in building the world’s most complex and efficient optimizer. I think I know basically how one would do so, but I simply don’t care. In terms of the smaller compilers, I’m a great adherent of the KISS principle (Keep It Simple, Sidney). There’s entirely too little of that going around, lately.

In operating systems, most of my experience has been with the kinds of real-time OS’s and schedulers that we built into flight computers. In that world, the key consideration is to make the OS absolutely as small, fast, and bulletproof as humanly possible. Flight processors are always pushed right to the limits; If we put bigger and faster CPU’s in them, someone will come along with more complex algorithms that need to be solved in the same time. The OS always has to take a back seat to the real work that’s to be done. Its job is strictly to manage the resources, schedule events, handle interrupts, and otherwise stay out of way.

I still believe that this is the way an OS should be written. Unfortunately for us, several generations of OS experts have grown up using Unix, a system designed to be run in time-share mode, non-real time, using ASR-33 teletypes as the user consoles. The influence of Unix continues to this very day, in most non-Windows workstations as well as in Linux. I’d like to see a new OS, built more around the real-time rather than the time-share paradigm.

A wise man once said, "Any idiot can design a Rolls-Royce. It take a genius to design a VW." There are only so many things an OS, even a GUI-based OS, needs to do. It must handle events, manage shared resources, and keep multiple tasks from walking on each other. When an OS has an interface involving hundreds, even thousands, of system calls, something’s wrong. The KISS principle has long since disappeared from view.

Resonance: Where do you see computational power heading in the next decade? Are computers of the type depicted in science fiction, such as Star Trek, a near-term reality?

Crenshaw: Actually, science fiction has traditionally underestimated what computers can do. Many years ago, space jockeys of science fiction stories still steered their craft by the seat of their pants. Any computers available were seen as the giant mainframe, often with the answers (numeric, of course) printed out on a paper tape. Very few sci-fi stories really anticipated the advances that we have made, even today. Few writers are sufficiently gifted to foresee what the future holds. Stanley Kubrick was one of the few who got it right, with the HAL 9000.

Resonance: Can you tell us what project(s) you are currently working on?

Crenshaw: Not really. I’m doing work related to defense, helping think up better and more reliable ways to blow people up. I can’t really say much more than that. For the past few years, I worked on medical electronics, helping to develop a new patient monitor for hospitals. That job was both challenging and fascinating, but in the end the high pressure and short deadlines got me down. No one can sustain such a pace forever.

Resonance: Did you read science fiction as a youngster? And who were your favorite writers, of science fiction as well as of other genres?

Crenshaw: Absolutely. I read Astounding Science Fiction (later Analog) voraciously, even including John Campbell’s witty, thought-provoking, if somewhat wacky editorials. I had so many favorites, I hardly know where to start. Clarke and Heinlein and Asimov, obviously. Asimov’s robot and Foundation series were/are without peer. There were many, many other favorite authors, most of whose names I now forget. I’ve enjoyed Ann McCaffree’s series on dragons, but of course there’s precious little science in them.

I don’t read much SF anymore. Used to be, SF writers were roundly (and justifiably, except for Asimov) accused of writing flat characters, of being so involved with science gimmicks that they failed to develop their characters and plots. Today, it seems to me that too many SF writers concentrate so hard on being literary that there’s no room for science.

Resonance: What are some of your skills that permitted you to succeed as a scientist and then a software designer?

Crenshaw: First and foremost is curiosity. I guess I’m a born engineer/scientist, because I performed my first experiment at about age two. I started taking toys and clocks apart about age four, and was getting them back together again, and working, by age six. I’ve always wanted to know everything about everything. It really bothers me to discover that someone else knows how to do something I can’t, and I won’t rest until I understand – I mean, really understand, it, at its most fundamental levels. If there’s any one thing I think distinguishes me from others my age, I think it’s that I’ve never lost that gee-whiz, wide-eyed sense of wonder at discovering something new to me.

Second is that KISS philosophy I mentioned. I tend to do things one step at a time, and write software one module at a time. The reason has nothing to do with someone’s latest methodology. It’s more a case that I’m well aware of my own limitations. I know that if I make things too complex, I won’t remember, later, what they’re doing inside. In my opinion, lots of other software developers could do with a touch more of the same humility. I write copious notes to myself, almost as though I were writing for someone else, and I do things in VERY small steps. I’m a big believer in the notion of prototyping and incremental development, adding only the absolute minimum complexity necessary to solve the problem.

I believe that the universe is, at its heart, both simple and understandable. It always makes me nervous when a given discipline turns out to be difficult and confusing. It makes me think that we still don’t understand it yet. Whenever I’m faced with a new problem, I believe it’s time well spent to figuratively circles around it, poking and prodding here and there, until I find the soft spot that leads to the simplicity hidden within it. No matter how thorny and complex a problem seems to be, I’ve found, without exception in over 40 years, that such a soft spot always exists. It’s just a matter of looking at things from the right perspective.

The great race car designer, George Miller, when asked the secret of his jewel-like and highly successful designs, said "Simplify, and add lightness." I build my software like that.

 Resonance: What were some of your other interests?

Crenshaw: Three things: I’m a Christian, and also a scientist (but not a Christian Scientist). I’m fascinated by the relationship between the two, and somewhat dismayed that scientists and theologians spend more time arguing with, rather than learning from, each other. I’m a firm believer in the power of reason and rational thought, and the structure that science has given to the universe. However, I’ve had enough contact with things supernatural – things that can’t be explained by Maxwell’s equations – to be thoroughly convinced that there’s Something Else Out There. In my time I’ve seen science go from not even understanding how the Sun stayed hot, or what was inside a living cell, to being able to explain the function of that cell in the greatest detail. The more we learn, however, the more we realize how little we know. There are those, I know, who still believe, like the scientists of the 19th century, that some day all would be made clear; that science would have the answer to every question. Today, I believe that thought is mere wishful thinking, and I don’t think there are many competent physicists who aren’t acutely aware of the limitations of their own craft. I’m encouraged by recent discoveries, in astrophysics, biochemistry, geology, and archaeology, that seem to suggest that perhaps the Book of Genesis got it all right, after all. With the death of gradualism and the recent rise to respectability of catastrophism, I think we’re on the verge of a great new paradigm in both science and theology.

Second thing: I rehab baby animals, both wild (when I can) and domestic. It all began some years ago, when a baby bird fell through the AC duct into my office. I ended up taking the bird home, where my daughter and I raised it. This was long before I knew one was supposed to have a license to do such things. That one event opened a floodgate, and I’ve been raising baby critters ever since. My favorites are opossums and bluejays … both fascinating animals and great companions. More recently, I’ve discovered that licensing thing, and since I’m not able to stay home to get a license, I content myself with helping out as a volunteer where I can, and raising domestic ducks and chickens. Most nights, I can be found with a baby chick or duckling asleep in a box beside my bed, and more than a few times, asleep cuddled under my armpit or chin. My wife, fortunately, is an understanding soul.

Lastly, I love motor racing. I rode my first motorcycle at age 12, entered my first competition at age 13, and had built my own racing car by age 19. I love to race, still, though I haven’t done so for years. I try to never miss an Indycar or Formula 1 race.

Resonance: What are the roles of art in society? Does art do something for society that cannot be done by anything else? How are art and science intertwined? Does science have a role in art? And what about the role of art in science?

Crenshaw: Over the years, I’ve noticed that the art of a given society is a reliable mirror of the society’s values. The Roaring 20’s was a decadent time, and the popular songs, movies, Broadway plays, and literature of the period reflect that decadence. In the 40’s, the nation was at war, and the songs and other art reflect a society with purpose, courage, and commitment. I leave it to you to decide what the Rap songs of today, or the popularity of certain artists and authors, say about the health of our society.

Re science and art: I think to a degree they’re inseparable. Take a good look at some of the hardware built for physics experiments, and you’ll often find things built with far more beauty than is absolutely necessary for their purpose. We all share a sense of beauty, and the degree to which we achieve it in our work says something about us.

Of course, the argument still rages in the software world, as to whether programming is an art or a science. I think it has to be recognized as a little bit of both. If you look at the history of ground-breaking software, you’ll find that almost all of it – Unix, CP/M, VisiCalc, WordStar, Turbo Pascal, etc., were written either by one person or a very small group. And they did it more as a matter of personal pride than of profit. Recently, I’ve been talking with other old-timers about the "good old days" of the CP/M User’s Group. Folks were writing software for the public domain then, before the notion of shareware was ever thought up. If you look inside some of that code, you’ll find absolute art, as well as craftsmanship. Those people spent way more time than was either needed or justified, just because they wanted the software to be right. Again, a George Miller quote: "When it looks right, it is right." To me, there can be no doubt that this software is art.

Once my team was asked to evaluate a number of Pascal compilers. We got copies of the source files for each compiler, and each team member reviewed one the listings. One of them told me she couldn’t bear to study her assigned compiler anymore, because reading it gave her a headache.

That compiler was rejected, on the grounds that "It gives Rosemarie a headache." It was no mistake; that compiler turned out to be a dismal failure.

Resonance: Your training was as a physicist, your Ph.D. in physics from Auburn University. Do you follow some of the current research that may have an impact on space propulsion? Do you have any thoughts on any of the futuristic "faster than light" ideas being investigated?

Crenshaw: I’ve tried to keep up over the years, though it’s been a long time since I solved Maxwell’s or Schroedinger’s equations. I’m fascinated by the recent theories, such as string theory, that postulate a large number of unseen dimensions in our universe. I’ve always suspected that atomic particles might be sort of like vortices in some higher-dimensional space, and this model fits the observations as well as any.

Particle physics, on the other hand, leaves me completely cold. It strikes me entirely too much like the "epicycles upon epicycles" structure of Ptolemaic astronomy. I suspect that we are missing something very fundamental in this area – something that needs another Einstein to uncover.

Einstein was, obviously, a brilliant scientist. But he was also a very practical one. He had that uncanny, and all too rare, ability to see the underlying simplicity hiding within a seemingly complex problem. He could almost have been quoting George Miller when he said, "Simplify as much as possible, but no more." If you look at his great contributions, you’ll find that, underneath all the math, there’s a model of astonishing simplicity.

I cherish my time at Auburn. My major professor, and the Physics Department Head, was Dr. Howard E. Carr. He was a physicist of the old, Faraday-and-Maxwell, get-in-the-lab-and-get-dirty, mold. He designed and built the Uranium separators for the Manhattan Project’s Oak Ridge facility. He later did a lot of the early, practical work with op-amps and analog computers. He once had an engine failure while in the desert, en route from White Sands back to Alabama. Alone in the desert, he crawled under the car and replaced the rod bearing with a section of leather cut from his belt. The leather "bearing" not only got him home, it remained in the car until he sold it years later. That’s my kind of physicist. There’s not many around anymore, these days.

I do believe that we’re poised on the brink of some great new discoveries in Physics, the kind of discoveries that require an Einstein to uncover. I think it reasonable to assume that these new discoveries will change science and society every bit as much as Einstein’s theory, or Maxwell’s equations (leading to radio) did. What bothers me about the current crop of theoretical physicists is that, brilliant as they are, their theories seem to be getting more complex, not simpler. And there seems to be little or no way to test the new theories in a laboratory. I’m afraid we might be missing something fundamental. I can’t see these scientists fixing cars using pieces of their belts. We could use more Einsteins and Carrs.

I suspect that when we really, really understand how the laws of nature work, FTL drives, time travel, anti-gravity, you name it, will all fall out. That’s a long ways off, though.

Resonance: What are your thoughts on the strategic defense initiative? Is it technically feasible in the near-term, and is the idea strategically sound?

Crenshaw: Actually, I've ALWAYS thought it was sound. I know David Parnas and many others have said that something that complex can't be made to be reliable. However, the intent was never to make it complex in the first place. If you can do one thing well, doing it again, 1499 more times, isn't much more difficult. I could never quite understand why they felt it had to have "irreducible complexity." In concept, it's pretty straightforward: Look at a collection of incoming warheads, try to decide how best to shoot them down, then do it. Seems rather straightforward to me.

Resonance: Speaking to a young person of about 13-14 years old, just entering High School, what advice would you offer?

Crenshaw: You know, schools don’t have to teach kids things. Look at a two- or three-year-old. They’re constantly asking, "Daddy, what … why … how?" They’re information sponges – they soak up every scrap of data they can get their hands on. I learned long ago that the challenge, for a child, is to get through public school without having one’s desire to learn totally destroyed. Unfortunately, I’m afraid that feeding kids data is not very high on educator’s priorities, these days.

So my advice to kids would be, never let them grind you down; always keep that sense of wonder and discovery. Don’t let them take that away from you. I do think that kids should learn as much math as humanly possible. It’s math that makes all other science and engineering possible. It’s a great pity that we teach it so poorly.

Resonance: What do you consider to be a good first programming language for a teenager to learn?

Crenshaw: Pascal, definitely. There is no second place.

 Resonance: If you were having a discussion with any living person, who would it be and what might some of your questions be?

Crenshaw: Wow, that’s a tough one. A few years ago, I would have chosen one of my all-time heroes, Richard Feynman. Lacking him, I’d like to talk to Stephen Hawking or Murray Gell-Mann. Unfortunately, I think both of them have egos much too large to discuss things with me.

My role model remains Dr. Carr, who is still alive. I think maybe I’d just ask him to give me a complete core dump, while we’re both still able.

Resonance: What do you do in your free time? Do you have a few favorite web sites?

Crenshaw: Free time? There’s free time? Lately, getting four hours sleep a night while I’m finishing a book, it’s hard to remember what free time feels like.

In reality, I tend to cuddle with my wife, ducks, and chickens in any free time. Or we watch favorite movies (gotta see the new Star Wars!). I used to do a lot of tinkering with electronics, both analog and digital, and am currently in the process of building up a new lab (the computers, incidentally, will have not one single software product from Microsoft). Ditto for tinkering in my workshop. I recently bought a new house with a huge garage, which I’m converting to a workshop.

What will I build? Whatever I want to. Nobody can tell me what to do, or what not to, in my own labs.

I don’t do much web-surfing; the information flow rate is still too low for me. Maybe when we get two-way video cable …

Resonance: Could you tell us about the book you just finished writing and what the series is about?

Crenshaw: The series is pretty much a collection of my columns. It's called "Math Toolbox for Programmers," and will be available this fall from R & D Books. We expect three volumes in the series.

Resonance: If you could solve just one of this nation’s/world's problems, which one would it be?

Crenshaw: Hatred. I’m very concerned in the amount of anger, and hostility, and hatred flying around these days, both nationwide and worldwide. We seem to be becoming more and more polarized, on more and more issues and into more and more special interest groups. Currently, we see in Kosovo the same kind of ethnic hatreds that spawned the Holocaust. I grew up in Montgomery, Alabama, but I haven’t see the kinds of tension between the races we have now, since the days of bus boycotts and school desegregation.

Unfortunately, the Political Correctness movement and liberal politics tend to exacerbate and exploit tensions and animosities between groups, rather than ease them. Everybody seems to belong to one or another minority group, and everyone is being told that whatever bad has happened to them is someone else’s fault. I see that as an ominous sign of impending trouble. I’d like to plead, as did Rodney King, "Can’t we just all get along?"

This country could use another Apollo program; something to rally behind, and work together with a common purpose. It would be great if we didn’t need things like wars, cold or hot, depressions, natural disasters, or other calamities to force us to stop bickering, work together, and be neighborly. Unfortunately, we do seem to need such things. Our track record of getting along during times of prosperity is not good. Better a new Space Initiative, than another war.