As if the constant battles with costumed villains were not distracting enough, Stark was continually called to testify before Senate committees, who insisted that it was his patriotic duty to turn the Iron Man technology over to the military. Little did Senator Byrd (not the long-serving senator from West Virginia), who led the investigations into the connections between Iron Man and Stark Industries realize that the secret of Iron Man’s success—the transistor—was already in the public domain. The transistor was developed by three physicists in 1947 at Bell Laboratories in Murray Hill, New Jersey—the research lab of utility Bell Telephone. In order to facilitate the adoption of this new technology, Bell Labs ran seminars for other firms interested in using transistors, instructing them in the details of the new field of solid-state physics. It’s not enough to build a better mousetrap; you must also make sure that the mice know about it!
CLOTHES MAKE THE MAN
Following his first appearance, Iron Man’s suit would undergo nearly constant modifications, both cosmetic and significant. The suit was gray in Tales of Suspense # 39, but by the very next issue, Stark decided to change the color to gold, so as to make more of an impression on women. You would think that a multimillionaire industrialist who looks like Errol Flynn (the model upon which artists based their drawing of the mustachioed Tony Stark) would not have to worry about whether his secret identity as Iron Man was attractive to the ladies, but it is presumably just such attention to detail that brought Tony Stark his success. Within a year, the suit would be redesigned again, now as a more form-fitting yellow-and-red ensemble shown in fig. 39 that, with minor variations, would persist to recent times.
The weapons that were distributed throughout the suit would also undergo near-constant upgrades. Initially Stark had “reverse magnetism” projectors in the palms of his gloves, but these were soon modified to “repulsor rays” that were essentially “force beams.” A large recessed disc on his chest housed a “variable power spot-l ight” that evolved into a “uni-beam” (I’m not really sure what this did). He originally had a radio antenna extending from his left shoulder, but improvements in wireless transmission and reception technology enabled this function to be incorporated within the body of his iron suit.
Fig. 39. Panels from a bonus section “All About Iron Man” in Tales of Suspense # 55, providing a schematic of the 1960s Golden Avenger, and a tutorial stating that the charge to power supplies feeding his transistors is depleted the more he uses them.
The armor itself is still quite heavy, even in its more flexible, streamlined form. The only way that Stark is able to walk in this iron suit, and to lift objects weighing up to several tons, is through the application of “tiny transistors within his armor which increase his power tremendously!” And he’s going to need this extra power. In order to estimate how much the armor weighs, assume that the Iron Man suit is one eighth of an inch thick and has the average density of iron, which is roughly 8 grams per cubic centimeter. The surface area needed to make the suit can be approximated by taking Tony’s trunk as a cylinder, his head as another, smaller cylinder, and his arms and legs as smaller, longer cylinders. If Tony is about six feet tall and his suit jacket is a 50 regular, then his total surface area is roughly 26,200 square centimeters. The volume of iron within his suit is found by multiplying the surface area by the armor’s thickness of ⅛ inch, or 0.32 centimeters, yielding a total volume of metal of roughly 8,400 cubic centimeters. To determine how much it weighs, we multiply this volume by the density (8 grams/cm3) and obtain 67,000 grams, or 148 pounds, excluding the weight of all of the transistorized circuitry. Tony Stark would frequently carry all of this in his briefcase (with one dress shirt covering the armor as camouflage (see Tales of Suspense # 55), except for the chest plate, of course, which he wore constantly in order to keep the shrapnel from worming its way to his heart. Consequently, simply by lugging nearly 90 pounds of armor around in this briefcase, Tony would have developed considerable upper-body and bicep strength as a side benefit of being Iron Man.
The suit’s weight leads to the question of how his jet boots enable Iron Man to fly. If the suit weighs nearly 150 pounds, and Stark himself tips the scales at 180 pounds, then his boot thrusters have to supply a downward force of 330 pounds (equal to a mass of 150 kg), just for Iron Man to hover in the air. Presumably, these jets use a chemical reaction to violently expel the reactants from the soles of his boots. As every action is balanced by an equal and opposite reaction, this downward force leads to an upward push on Iron Man, keeping him aloft. If he wants to accelerate, then his boots have to provide even more force, as only the force in excess of his weight provides an acceleration (F = ma).
Tony would frequently need to travel from his Stark Industries plant on Long Island to Avengers Mansion in the heart of Manhattan, a distance of approximately fifty miles (as the Golden Avenger flies) in a time of ten minutes. This corresponds to an average speed of 300 mph, which is nearly half the speed of sound! (In the film Ironman, he dueled with fighter jets traveling at least twice that fast!) Ignoring the energy that Shellhead must expend to push the air out of the way as he travels at this speed, this implies that for a kinetic energy (½)mv2 at this speed, his armor requires at least 1.37 million kg-meters2/sec2 of energy. When Iron Man needed to travel great distances, he would eschew the boot jets and make use of motorized roller skates that were built into his boots. Not only would it be more fuel efficient, since energy does not have to be expended counteracting gravity to keep Shellhead in the air, but whenever he is decelerating, he can use the rotational energy and an alternator to recharge his internal batteries, as in an automobile. In this way, Tony Stark anticipated recent hybrid-engine automotive technology.
In the seventies, Iron Man had gone green, and his armor was now coated with a thin layer of solar cells, enabling him to recharge whenever he was in direct light. The energy from the sun on an average day in the United States is roughly 200 kg- meter2/sec2 per second over an area of 1 meter2. We have just calculated the surface area of the Iron Man suit to be 26,200 centimeters2, which means that the amount of energy per second striking Iron Man is 262 kg-meter2/sec2 (at any given moment only half of his available surface area can be facing the sun) while his jet boots require an expenditure of power of more than a million kg-meter2/sec2. If the solar cells are 50-percent efficient in converting the energy of the sun into stored energy in Tony’s battery packs (and most commercially available solar cells have a conversion efficiency of only about 10 percent), Iron Man would need nearly three hours to soak up enough sunlight for this one trip. We have considered neither the energy needed to run the suit’s internal air-conditioning unit (pushing air out of the way at 300 mph will make any person inside a metal suit a tad sweaty), nor whether he has to fire his repulsor rays during the flight. In the normal course of a typical day in the life of Iron Man, he will expend energy much faster than he can recharge his storage batteries using solar cells.
To give the writers of the Iron Man comic credit, their concern with mechanisms for Tony Stark to recharge his armor’s storage batteries implies recognition of the Principle of Conservation of Energy. From his very first appearance in Tales of Suspense # 39, it was always acknowledged that running the mechanized Iron Man suit required large amounts of energy and that the greater his expenditure of power, the faster the drain on the energy reserves he might carry on his person. Not only was a ready supply of electrical energy necessary to animate his jet boots and activate the servo-motors that enabled him to move in the suit and that increased his strength, but his chest plate needed electrical energy as well in order to protect his heart from the shrapnel he carried with him ever since that fateful day in Vietnam. The 1960s Iron Man would occasionally have to drag himself dramatically along the ground after a particularly energy-exhausting battle, searching for an electrical outlet in order to recharge his battery reserves.
Even after he made the transition to solar-powered battle armor, Stark’s suit could run dry in an em
ergency. In Iron Man # 132, Tony drained every last erg of energy (one erg is one ten millionth of a kilogram-meters2/sec2) from his suit in an exciting, no-holds-barred battle with the Incredible Hulk. Tony focused all of his suit’s stored energy into one final punch, and accomplished what had previously been impossible: Iron Man knocked the Hulk unconscious. But the cost to Stark was high. With absolutely no power to move his suit, Stark was trapped, unable to move within his now rigid shell of armor. To make matters worse, the protective covering over his eye and mouth slits had been engaged, to shield Stark from a previous explosion. Tony therefore faced suffocation once the air contained in the suit was used up. It would take all of the following issue for Ant Man, forcing his way in through the exhaust port in Iron Man’s boot jet, to travel the length of the armor, avoid the suit’s internal protective mechanisms, and disengage the faceplate’s protective covering.
HE FIGHTS AND FIGHTS WITH REPULSOR RAYS
Of all of Iron Man’s weapons, the most effective are his “repulsor rays,” which are fired from discs on the palms of his armored gloves. Back in his first appearance in Tales of Suspense # 39, the first version of this glove-based repulsion weapon was a “reverse magnetism” ray used to fight his way out of Wong Chu’s prison camp. Wong Chu’s guards, finding that small-arms fire bounced harmlessly off the iron suit that the intruder wore, responded by preparing to shoot bazookas and throw grenades at the Yankee invader. Fig. 40 shows that as they fetch the heavy weaponry, Tony takes the time to “reverse the charge on this magnetic turbo-insulator and use a top-hat transistor to increase its repelling power a thousandfold!” As the rays are emitted from his hand, deflecting the weapons, he exclaims, “There! Reverse magnetism—it works like a charm!” In fact, it would have to work like a charm, because there’s no way it could work using solid-state physics.
Fig. 40. Iron Man, in his first appearance in Tales of Suspense # 39, fights his way out of a Vietnamese prison camp using a top-hat transistor and a “magnetic turbo-insulator.”
There’s only one aspect of the scene summarized above that is physically correct, and that involves the “top-hat transistor.” There is no such thing as a “magnetic turbo-i nsulator”; this is just technobabble. The “turbo” modifier is just to make these insulators sound cool. There are magnets that are nonmetallic—that is, they are electrical insulators, but still generate a large magnetic field—and devices called “top-hat transistors” do indeed exist. They are so named because they look like small cylinders, about the size of pencil erasers (this was back in the early 1960s, long before the microminiaturization of transistors enabled millions of such devices to be fabricated on a chip measuring only a few millimeters on each side), with a small disc at their base at which the electrodes extended, and this makes them look a little like the top-hat playing piece in a Monopoly game set. The panel showing Tony Stark employing such a device to amplify the current to his “magnetic turbo-i nsulator” is physically plausible. But the second-to-last panel, in which he then employs said device to deflect the grenades and bazooka shots using “reverse magnetism” is not.
While every electron, proton, and neutron inside every atom has an intrinsic magnetic field, the natural tendency of magnets to line up north pole to south pole has the effect of canceling out the magnetism of most atoms. Any magnetic field that Iron Man would create using a powerful electromagnet in the palm of his glove would only be effective if: (1) the grenades being tossed at him were for some reason already magnetized and (2) they were all perfectly thrown so that their north poles were all pointing in the same direction and (3) the magnetic field created by Iron Man’s hand was also oriented so that the north pole was directed toward the incoming grenades and not the south pole, which would have the effect of accelerating the weapons toward him. It is unlikely that Tony Stark could always count on his opponents to cooperate with suitably magnetically oriented weapons.
Iron Man’s reverse magnetism ray actually has a better chance of working on nonmagnetic objects! Recall our discussion in Chapter 19 concerning Magneto and the phenomenon of diamagnetic levitation. Unlike metals such as iron or cobalt, for which the internal atomic magnetic fields align in the same direction, many materials, including water, are diamagnetic. In this case, when they’re in an external magnetic field, the atomic magnets orient themselves to oppose the applied field. Thus, the very process of trying to magnetize the object leads to a repulsive force. Iron Man’s reverse magnetism could repel objects, but only if they were diamagnetic, and it would not work on many metallic objects that are either ferromagnetic or paramagnetic (which align with an applied field). Magneto creates these large magnetic fields through his mutant power, but Iron Man must do it the old-fashioned way, using electromagnets (similar to the one constructed by Superboy in Chapter 18). As Iron Man does not carry around with him an electrical dynamo like the one used by Superboy, a few shots of this reverse magnetism ray would drain his batteries faster than a fight with the Hulk. Furthermore, the recoil of such weapons is considerable. When supplying a large force against a target, they will induce an equal and opposite force against the gun and the shooter holding it. Tony Stark was clever to build his repulsor rays into his gloves. By locking the servo-motors that enable his armored arms to move, his iron suit provides a large and rigid inertial mass to take up the recoil whenever he fires this glove-based weapon.
While “reverse magnetism” may not be physically practical, hand-held pulsed-energy weapons have begun to make the transition from comic-book fantasies to military research facilities. Certainly these weapons cannot be the same “magnetic repulsors” as Iron Man uses, for the reasons argued above. The energy needed to generate a magnetic field large enough to deflect an object using only diamagnetic repulsion is so large that it would be more effective to employ conventional weaponry. Nevertheless, “pulsed” energy systems are under active development by the military. By generating a large voltage inside the weapon that can be rapidly discharged in a thousandth of a second, the power (change in energy per time) can be quite high. This electromagnetic pulse, if directed at a target, would deposit this energy in a localized region faster than the heat could be safely dissipated away. High-intensity laser beams delivered in extremely brief pulses are used in physics laboratories to nearly instantaneously melt a small region of a solid’s surface, and in principle the same process could be employed in an offensive capability. The big drawback is once again the energy requirements of such a weapon. If one must carry a miniature power plant around in order to fire such a pulsed energy weapon, the element of surprise in any combat situation would be lost.
SOLID STATE PHYSICS MADE EASY
What is a transistor? What is this electronic device that, at least according to Stan Lee, is endowed with miraculous abilities that enable Iron Man to successfully fend off the Mandarin, the Crimson Dynamo, and Titanium Man? A short answer is that transistors are valves that regulate the flow of electrical current through a circuit. Such answers are easy to remember, but they tell us nothing about how transistors actually function. The first question we should address is: What exactly is a semiconductor, which is neither a metal nor an insulator? We hear a great deal about how we are living in the “Silicon Age,” but what is so special about silicon? In the next few pages I will try to condense more than fifty years of solid-state physics as I answer these questions.
Silicon is an atom, a basic element of nature, just like carbon, oxygen, or gold. A silicon atom’s nucleus has fourteen positively charged protons and (usually) fourteen electrically neutral neutrons, and to maintain charge neutrality there are fourteen negatively charged electrons surrounding the nucleus. These electrons reside in the “quantum- mechanical orbits” that, as discussed in chapters 21 and 22, arise from the wavelike nature of all matter. The possible “electron orbits” are specific for each element, and determine the allowed electron energies.
Quantum mechanics enables us to calculate, via the Schrödinger equation, the allowed “orbit
s” of the electrons in an atom, and knowing how many different possible orbits an electron can have in an atom is like knowing the number and arrangement of chairs in a classroom (stay with me here; this classroom metaphor is going to be useful in explaining metals, insulators, and semiconductors). The chairs only represent possible or virtual classes; it is not until the students enter and take their seats that the class is real. If only one student comes in and takes a seat, this is like having only one electron in a possible quantum- mechanical orbit. We would call this class hydrogen, in analogy with the atom that has only one electron in its neutral, stable form. If there were two students sitting in the class, we would have helium, fourteen students would make up silicon, and so on. The first students to enter the class take the seats at the front of the room, close to the blackboard, in our hypothetical example. The last students to enter take seats near the back of the auditorium, far from the blackboard (where the positively charged nucleus will be). This arrangement, with the closest seats filled by students, describes the lowest-energy configuration. For a carbon atom with six electrons, the closest orbits are occupied. If the carbon atom gains some energy, say, from absorbing light, some of its electrons will then occupy higher-energy orbits (seats farther from the front).
Whether a material is a metal, a semiconductor, or an insulator depends on the energy separation between the highest level filled with an electron and the nearest available unoccupied level. In the classroom analogy, the solid can be thought of as a very large auditorium with many rows of seats, provided by the constituent atoms that make up the material. There will be an empty balcony that contains an equal number of seats. If the electrons sitting in the lower-energy orchestra seats77 are to conduct electricity when a voltage is applied across the solid, then they gain extra energy. But they can move only to a higher energy if there is an empty state for the electron to be promoted into (recall the discussion of quantized energy levels in Chapter 21). The electrical properties of any solid are determined by the number of electrons residing in the lower orchestra seats and the energy separation between the lower occupied seats and the next empty ones in the balcony.
The Physics of Superheroes: Spectacular Second Edition Page 32
