What about this plasma physics? Will it ever amount to anything?

-Dr. Hugh L. Dryden, NASA deputy administrator, to Macon C. Ellis, Jr., head of Langley's Magnetoplasmadynamics Branch

[121] While the Hydrodynamics Division sank at Langley, a few new research fields bobbed to the surface to become potent forces in the intellectual life of the laboratory. Most notable of these was magnetoplasmadynamics (MPD)-a genuine product of the space age and an esoteric field of scientific research for an engineering-and applications-oriented place like Langley. If any "mad scientists" were working at Langley in the 1960s, they were the plasma physicists, nuclear fusion enthusiasts, and space-phenomena researchers found in the intense and, for a while, rather glamourous little group investigating MPD. No group of researchers in NASA moved farther away from classical aerodynamics or from the NACA's traditional focus on the problems of airplanes winging their way through the clouds than those involved with MPD.

The field of MPD concerned the effects of magnetic and electric fields on the motions of plasmas. A plasma, as simply defined at the time, consists of an ionized high-temperature gas. For those readers who have forgotten their high school chemistry, a gas consists of atoms and molecules that are virtually unrestricted by intermolecular forces, thus allowing the molecules to occupy any space within an enclosure. In other words, the atoms and [122] molecules are continually moving around and colliding with one another. When a sufficiently violent collision between two atoms occurs, a negatively charged subatomic particle known as an electron is knocked out of its orbit, thus resulting in a "free electron" (an electron that is not bound to an atom). Sometimes in the collision, an ion (a positively charged particle bound to the electron) is knocked free as well. At the instant these particles are released, the gas is said to be "ionized" and is called a plasma.

Considered as a whole, a plasma is electrically neutral, composed as it is of an approximately equal number of positively and negatively charged particles plus a variable fraction of neutral atoms. A plasma, however, by virtue of its charged particles, is nonetheless a conductor of electricity. Thus, as is true for any electrical conductor, the motion of a plasma can be greatly influenced, and perhaps even controlled, by electromagnetic forces.¹

By the late 1940s, the study of the motion of ionized gases in the presence of magnetic fields had become a major international focus for scientific research. The new field, which was really a subfield of the large, complicated, and still emerging discipline of "plasma physics," was known by many names: "magnetohydrodynamics," "hydromagnetics," "magneto-aerodynamics," "magnetogasdynamics," and "fluid electrodynamics."^* Generally speaking, however, the name "magnetohydrodynamics," or MHD, won out.²

But the name did not prevail at NACA Langley. There, in the years before the establishment of NASA, a coterie of aerodynamic researchers involved in plasma studies conducted in the center's Gas Dynamics Laboratory, thought that the name magnetohydrodynamics was not appropriate. The interested researchers were not concerned with water but rather with hot gases or plasmas, so they coined the term "magnetoplasmadynamics." Outside of NASA, however, magnetohydrodynamics remained the standard term.

Most work on plasmas before World War II pertained to the dynamics of upper atmosphere magnetic storms and to the phenomenon of radiant auroral displays similar to the aurora borealis or "northern lights." These studies, undertaken most notably by a British group interested in solar and terrestrial relationships led by astrophysicist Sydney Chapman (18881970), involved questions about what fueled the sun and the stars and about how the ionized gases brought about by ultraviolet radiation behaved in [123] interstellar space. In the 1920s, Chapman postulated that several geocosmic phenomena could be explained by the "differential action" of the earth's magnetic field on protons and electrons emanating from the sun. Solar activity, in Chapman's soon-to-be dominant view, influenced the terrestrial magnetic field, aurorae, the conduct of atmospheric electricity, and the earth's weather patterns.³

In 1942, Swedish astrophysicist Hannes Alfven (an eventual winner of the Nobel Prize) advanced an MHD theory of the so-called solar cycle, the periodic round of disturbances in the sun's behavior as seen in the fluctuation in the number and the area of sunspots and in the form and shape of the sun's corona. Some 10 years later, in the early 1950s, Alfven proposed an even more provocative theory. He postulated that the planets had been formed by an MHD process by which ionized gases became trapped electromagnetically and pulled inward by the sun's gravitational force, thus leaving them at certain distances from the sun. The only way to fathom the process, Alfven argued, was to work further with MHD equations.⁴

Thus, in large measure, the interest in MHD began with the modern astrophysicists. From the 1920s on, many of their most essential questions concerned MHD: What mechanisms are involved in galaxy formation? What is the nature of the magnetic fields of the sun and the other stars? How does the internal energy in hot stars convert into the kinetic energy of gaseous clouds in interstellar space? How do stars form from gas clouds? What is the origin of cosmic rays, the Solar System, the universe? The key to understanding the cosmos lay in the fathoming of MHD principles.

Revolutionary discoveries about the space environment made with the first space probes strengthened the belief in MHD's importance. On 1 May 1958, five months to the day before the NACA transition to NASA, American astrophysicist James Van Allen announced his discovery of a region of intense radiation surrounding the earth at high altitude. Data from Geiger counters aboard the first three Explorer spacecraft, the first successful American satellites, confirmed a theory that Van Allen had been working on for some time. This theory suggested that the earth's magnetic field trapped charged subatomic particles within certain regions. Experiments aboard subsequent exploratory rockets and spacecraft indicated with a high degree of certainty that more than one radiation belt in fact enveloped the earth. The intensity of the belts varied with their distance from the earth. The zone of the most intense radiation began at an altitude of approximately 1000 kilometers (621.37 miles).⁵

The discovery of what immediately came to be known as the Van Allen radiation belts inspired a wide range of fundamental new investigations. Within months, scientists around the world realized that surrounding the earth was a vitally important magnetic region of still unknown character,

shape, and dimension where ionized gases-plasmas exerted a strong force. They dubbed this mysterious region "the magnetosphere." In the exciting but highly speculative early days of magnetospheric physics, this region was....

[125] ....alternately described as "a high region of the earth's atmosphere" or as a "low or bordering region of space."⁶

Another important discovery of the space age fed the new science of magnetospheric physics: the notion of "the solar wind." This theory was first expressed by Eugene N. Parker of the University of Chicago in 1958 and later confirmed by measurements taken from Soviet Lunik spacecraft in 1959-1960 and from Explorer 10 in 1961. Parker suggested that the sun's corona, or outer visible envelope, was expanding continuously, causing streams of ionized gases to flow radially outward from the sun through interplanetary space. (The sun is, after all, a big ball of plasma.) The intensity of these plasma streams varied greatly relative to solar activity, especially solar flares. The force of these streams, or solar wind, impinging upon the earth's magnetic field created the familiar magnetic storms.⁷ By 1960 scientists possessed evidence that a plasma wind did blow continuously from the sun, and the wind clearly displayed dynamic magnetic phenomena.

The field of study that the Langley researchers had come to call MPD was growing quickly in esteem and importance, not only in the United States but also around the world. Newly conceived experiments with magnetically compressed plasmas provided scientists with an opportunity to generate and study a small sample of the solar corona in the laboratory. Scientists gathered basic data on subatomic behavior at temperatures for which no such information existed before. A major and extraordinarily exciting new age of modern physics was dawning. Scientists saw fascinating new research opportunities, and they dreamed of fantastic technological applications. Unfortunately, very few of their dreams would be realized. But in the early 1960s, that was something impossible to know.

What Langley researchers, especially those involved in gas dynamics and other hypersonic investigations, did know in the late 1950s was that the time for a major change had arrived. "The space age told us to move away [from] classical aerodynamics into more modern things," remembers Macon C. "Mike" Ellis, the man who would head Langley's formal MPD effort, "and, as quickly as we could, we did."⁸ in handwritten notes made at an internal meeting of his Gas Dynamics Branch held on 18 June 1958- during the same period that plans for NASA's initial organization were being formulated in Washington-Ellis wrote, "Either we make a big change now or [we] try to make more significant contributions in aerodynamics."

a field we are a ready in and should push hard.... We should go all out to get qualified physics instructors.... We should have seminars on "space type" and reentry subjects.... We must work and plan toward ultimate "conversion" of our work when aerodynamics becomes secondary.... We must go big into the new environment of space.⁹

 

[126] Now was the time for Langley researchers to assume leadership roles in the emerging space disciplines and vigorously seek major technological applications.

Through the late 1950s, nothing had been done formally at Langley to focus the efforts of those involved in the study of MPD-related subjects. Many people at the laboratory, some of them senior engineers and research managers, did not know what MPD was or did not understand what all the fuss was about. Furthermore, nearly all of the people concerned with MPD were members of the Gas Dynamics Laboratory, so they were already grouped together and interacting regularly. Thus, for several months, even after the new space agency was established, no Langley leaders saw a need to create a new organization just for the MPD enthusiasts.

But interest in the new field kept growing. The idea that flows could get so hot that the constituents of the air would actually break down and become treatable by applying magnetic forces was extremely exciting. If airflows could be "treated" electromagnetically, they might even be controlled. That was every aerodynamicist's dream. MPD offered a sort of aerodynamic alchemy, a magical way of turning lead into gold, rough turbulent flow into smooth laminar flow, dangerous reentry conditions into pacific ones. With these glorious possibilities, MPD fostered great technological enthusiasm and attracted many able researchers who hoped to find solutions to some fascinating and very complex problems.

The study of MPD became increasingly glamourous in the late 1950s, so much so that Langley management soon understood that it should advertise the progress that Langley researchers were making in MPD studies. At each of the former NACA laboratories-Lewis, Ames, and Langley-research in MPD grew in earnest in the months just before the metamorphosis of the NACA into NASA and thereafter gained momentum.¹⁰ At the first NASA inspection in October 1959, MPD was a featured attraction. In the printed inspection program, MPD merited one of the 13 subtitled sections. Visitors on the inspection tour stopped at a special MPD exhibit. At that stop, a Langley MPD specialist stood in front of a graphic panorama of the universe and introduced his subject by saying that "the space environment is filled with manifestations of this new science." ¹¹

Above all other members of Langley's staff, Floyd Thompson, still officially the associate director, became most enthralled with the glamour of MPD. As Mike Ellis remembers, "Thompson was tremendously supportive of our effort." One of the best measures of Thompson's enthusiasm was his request that the MPD staff be "on tap" as the special attraction for major events. He "always put us on stage at the NASA inspections and when various groups of scientists came through the laboratory," Ellis [127] recalls. Thompson appreciated that work in this exciting new field of science could enhance the reputation of his aeronautics laboratory.¹² In May 1960 the same month he took over officially from Henry Reid as the Langley director, Thompson established a Magnetoplasmadynamics Branch of the Aerophysics Division. From its beginning, MPD was one of Thompson's pet projects.

The Aero-Physics Division was the natural home for Langley's MPD effort. This division was led by hypersonics specialist John V. Becker, an NACA veteran whose employment at Langley dated back to 1936 and who by the mid-195Os had become deeply involved in work related to hypersonic gliders and winged reentry vehicles. A research-minded engineer, Becker was a strong and confident division chief (he had been one since the mid-1940s, passing up several opportunities to move up to posts in senior management). He was comfortable having a research effort as esoteric and as sophisticated as MPD based in his division. Scientifically, he was quite sharp and was more than capable of appreciating the complexities of this new field of research as well as its promise for making major contributions to the space program. Through the 10-year span of the MPD Branch (1960-1970), Becker not only tolerated the many MPD enthusiasts in his division but also almost always supported their ideas.

The first and only person to be in charge of Langley's MPD Branch was Mike Ellis, an NACA veteran who was 42 years old when the branch was organized. Ellis had come to work at Langley in 1939, and over the course of his career at the laboratory, he had been involved in pioneering work on the aerodynamics of jet engines, ramjets, and supersonic inlets and nozzles. Fittingly, Ellis had worked for Eastman Jacobs and with Arthur Kantrowitz in the early 1940s, and he had heard firsthand accounts of his former colleagues' attempt to design a fusion reactor in the spring of 1938. By the late 1950s, Ellis was one of Langley's most outspoken believers in MPD's promise of technological benefits. Ellis encouraged Floyd Thompson's enthusiasm for MPD and persuaded Langley's senior staff of mostly engineers that MPD was a field of research vital to the future of NASA. When the time came to pick someone to head the new branch, Ellis was unquestionably the person for the job.

Ellis was no extraordinary "scientific brain." As an aeronautical engineer, his talents were quite respectable, but he possessed no special competency in the physics of fluids beyond his experience in aerodynamics or gas dynamics. He was always the first to admit that the complexities of plasma physics and MPD were such that "there was no way" that he personally could conduct basic MPD research. That challenge he would leave to minds more suited for it. But Ellis could bring the MPD researchers together as a unit, serve as their strong external advocate, shield them from front-office pressures, and make sure that they received the support they needed to carry out their work. "I just tried to keep my head above water," Ellis explains, "and keep....

In the 1960s, John V. Becker (left) headed the Aero-Physics Division, which was home to many of the center's highest speed, and most radical, research facilities. These included supersonic and hypersonic wind tunnels, arc-jets, and shock tubes covering a speed range from Mach 1.5 to Mach 20. Some of these facilities, such as the $6.5 million Continuous-Flow Hypersonic Tunnel (below), were the forebearers of the strange apparatuses of the MPD Branch. L-61-4064	.
.

....these 'mad scientists' from going off on too many tangents, or going mad myself." ¹³

The MPD Branch never became a large outfit. By the end of 1962, it had less than 50 total staff members: 27 professionals, 10 mechanics, 4 computers (mathematicians who helped to process and plot numerical data), and 6 secretaries. This staff was divided into four teams or sections. Plasma Applications, headed by Paul W. Huber, was the largest section, with 8 professionals. Space Physics, led by British physicist David Adamson, was the smallest with 3. Robert Hess's Plasma Physics Section had 7 professionals, and George P. Wood's Magnetohydrodynamics Section had 5. These sections (and their section heads) remained in place until the dissolution of the MPD Branch in 1970.

In addition to being small, MPD was self-contained. Whereas most of the research done in the center's branches regularly spilled over into other functioning units, most MPD work was done within the MPD Branch. A small amount of related research was done in the Flight Research Division and Full-Scale Research Division; however, most of this work concerned the development of microwave and spectroscopic diagnostic techniques. All told, the MPD work conducted outside the MPD Branch never involved more than about five researchers.

In terms of organizational genealogy, the MPD Branch grew from a narrow stem. With the exception of Adamson, and a trio of his colleagues from a space physics group in the Theoretical Mechanics Division, all the original members of the MPD Branch came from the Gas Dynamics Laboratory. The guru of MPD studies in this lab was Adolf Busemann. Throughout [130] the 1950s, Busemann had inspired engineers with his provocative theories and experimental ideas. At Langley on 22-23 September 1958, the German aerodynamicist even chaired an important interlaboratory meeting on MHD. Ninety-three people attended the meeting, which featured 6 speakers from Ames, 4 from Lewis, and 11 from Langley and was organized into three sessions-plasma acceleration, arcjets, and ion beams. Busemann gave a 20 minute talk on the theory of alternating-current (AC) plasma acceleration. This two day scientific meeting, held one week before the changeover to NASA, was the precursor of much larger conferences on MPD sponsored by NASA on almost an annual basis into the mid-1960s.¹⁴

Among the scientists working in MPD at Langley were several Germans. Like many other scientific institutions around the country, Langley had received a handful of German scientists who were part of Operation Paperclip, the U.S. Army intelligence operation that brought captured German rocket scientists and engineers to work for the U.S. government at the end of World War II. Busemann and two other outstanding researchers, Karlheinz Thom and Goetz K. H. Oertel, came to Langley through Paperclip. Both Thom and Oertel moved from Gas Dynamics to George Wood's MHD Section of the new MPD Branch. Both men stayed at Langley for several years before eventually taking posts at NASA headquarters.

At least 10 German scientists came to Langley as part of a postdoctoral program funded by NASA but sponsored by the National Academy of Sciences. This program, which was totally divorced from the normal civil service procurement system, enabled NASA to obtain talented people as Resident Research Associates (RRAs) without going through the normal hiring procedures of the civil service and without regard for NASA's personnel ceilings. In 1968, for instance, 6 of the 39 professionals in the MPD Branch were RRAs.¹⁵

Langley's MPD group attracted other foreign scientists. These included Dr. Marc Ferx, a French nuclear scientist who spent a few years at Langley in the mid-1960s and did some outstanding theoretical work. Feix was nominally assigned to Hess's Plasma Physics Section, but he actually worked with various people throughout the branch, especially with the Space Physics Section under David Adamson. Adamson had first worked at Langley at the end of World War II on an exchange program from the Royal Aircraft Establishment in Farnborough, England.¹⁶ After the exchange, Adamson went home to England, but soon returned to Langley.^**

In the 1960s, the researchers of the MPD Branch were the most highly educated group of people at Langley. The MPD Branch enjoyed the....

L-62-8122

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L-65-1110

.....academic mystique of having by far the highest percentage of advanced degree holders. At one point MPD had eight employees with earned doctorates, seven others at the Ph.D. dissertation stage, and virtually all of its younger people working toward advanced degrees.^***

Compared with other research groups at Langley, the MPD enthusiasts participated in more international scientific conferences; had more contacts with consultants, important scientific committees, and advisory groups outside Langley; monitored more research contracts; and received more distinguished visitors. Senior management asked MPD researchers to occupy center stage during NASA inspections and to escort distinguished guests into their Frankensteinian laboratories, which were filled with plasma accelerators, MPD-arc fusion reactors, powerful electrical supplies, spectrometers, microwave diagnostic instruments, and other bizarre apparatuses. Even to other engineers, this equipment was strange and unidentifiable. Understandably, their peers considered the Ph.D.'s and other 'mad scientists' of MPD a prestigious group. ¹⁷

[132] But the prestige could last only if Langley's MPD work proved deserving; the proof lay in conducting outstanding research programs and producing meaningful results. When the MPD Branch was formed in 1960, Langley researchers saw three particularly promising applications for MPD research. First, they hoped to accelerate gases to very high speeds to study and solve the reentry problems of intercontinental ballistic missiles (ICBMs), spacecraft, and transatmospheric or aerospace vehicles such as the North American X-15 rocket plane and the U.S. Air Force proposed X-20 DynaSoar boost-glider. The potential for these applications explains in part Langley's commitment to the small-scale but significant program of research and development of various plasma accelerators.

Second, the MPD experts at Langley hoped to develop prospective applications of MPD for spacecraft propulsion and power generation systems They were confident that electric or ion rockets would be the space propulsion system of the future. If humankind was to go to Mars or some other planet in a reasonable travel time, such radical sorts of propulsion systems would be required. Therefore, the centers for NASA's major propulsion efforts (especially Lewis in Cleveland and Marshall in Huntsville) must begin studying the ion and plasma devices that might someday offer to rocket technology the extraordinarily high specific impulses required for such faraway missions. Most definitely, the design and operation of these rockets would require the use of MPD principles. ¹⁸

Third, Langley's MPD specialists realized that if controlled thermonuclear fusion was to become a practical source for the volume generation of electricity, much more about the subject would have to be learned. Beginning in the late 1950s, the Atomic Energy Commission had begun conducting MPD research with the production of electric power in mind. Branch Head Mike Ellis also believed that "the eventual energy source will be thermonuclear fusion" and that "the development of this energy source most likely will depend upon fundamental discoveries in the field of magnetoplasmadynamics." ¹⁹

The promise of the field was indeed wonderful. But the promise of wonderful or even revolutionary findings and applications could sustain the new MPD group at Langley for only so long. At some point, MPD studies had to produce. The reality was, as John Becker later put it, "Of all the efforts we had, it was the most sophisticated and probably the least likely to succeed. We shouldn't have expected as much from it a8 we did."²⁰

Concern for the problems that the ICBM encountered during reentry flight prompted Langley researchers to begin the study of MPD in 1958 The physics of the unique conditions of the hot ionized flow around the missile's nose during reentry demanded special attention. Space vehicles [133] when reentering the atmosphere quickly became covered with electrically charged particles These particles formed a "plasma sheath" behind the bow shock Researchers hoped that an application of electric and/or magnetic fields to the plasma sheath could affect the airflow in desirable ways; for example' it could reduce the heat transfer to the nose. The most direct effect of the plasma sheath, however, was that radio transmission from the vehicle during reentry was not possible for obtainable radio frequencies. The plasma caused a period of "radio blackout."

To solve these problems, researchers at Langley had to simulate reentry conditions in the laboratory. This would require some new and unusual research equipment; conventional wind tunnels would not do the job. Small hypersonic tunnels, made possible by the development of high-temperature heat exchangers and high-speed nozzles and operated on an intermittent basis for flow durations of only seconds to no more than a minute, permitted studies of some forces during reentry, but not all and not some of the most important.

Several university, industrial, and government research groups had made significant advances in the acceleration of hot ionized gases by the late 1950s. Some of these advances involved the arcjet, a novel apparatus for aerodynamic testing that could heat a test gas (usually nitrogen, helium, or air) to temperatures as high as 20,000° Fahrenheit (F). In essence, the arcjet was a primitive electric rocket engine.²¹ In May 1957, five months before Sputnik, NACA Langley began operating a pilot model of its first experimental arcjet. Installed in Room 118 of the center's Gas Dynamics Laboratory, it was an "Electro-Magnetic Hypersonic Accelerator Pilot Model Including Arc-Jet Ion Source," with a test section size of a minute 7 x 7 millimeters and gas temperatures ranging between 10,000° and 12,000°F.²²

Fundamentally, the arcjet was just another hot-gas wind tunnel, which heated the gas electrically (typically using 100,000 kilowatts) to high temperatures in a low-velocity settling chamber, and then expanded it quickly through a tiny nozzle to supersonic velocities. No translational electric or magnetic forces acted on the gas in this conventional arcjet. The gas was simply being heated by an electrical discharge. Most of the charged particles in this high-temperature discharge recombined in the cooling process that occurred during expansion.

In 1962, Langley tried a slightly different but companion arcjet facility known as the hotshot tunnel. This hybrid, invented in the mid-195Os by engineers at the U.S. Air Force's Arnold Engineering Development Center in Tullahoma, Tennessee, combined the basic features of an arcjet with those Of a new type of wind tunnel known as an impulse tunnel. In this tunnel an explosive release of energy created high pressures and temperatures in the test gas.²³ In practice Langley's hotshot mostly missed the mark. To generate the very high heat, its operators had to resort to exploding a piece of copper through the tunnel circuit, thus the name "hotshot." The material....

...that then made its way through the test section was a mixture of hot air and vaporized copper, a very unsatisfactory medium for aerodynamic testing. The facility remained active into the 1970s, but the amount of useful work accomplished in it was quite limited.

Another facility for reentry testing that was developed in the late 1950s was the shock tube. Fundamentally, this was an impulse tunnel, distinguished from a hotshot mainly by the way in which energy was added to the test gas. According to a formal definition of the time, a shock tube was "a relatively long tube or pipe in which very brief high-speed gas flows are produced by the sudden release of gas at very high pressure into a low-pressure portion of the tube." The idea was to generate a normal planar (that is, Iying in one plane) shock wave and send it through a gas at a speed 20 to 30 times the speed of sound, [and] thus heating the gas behind the normal shock to an extreme temperature.²⁴

Langley's first shock tube began operation in the Gas Dynamics Laboratory in late 1951. By the end of the NACA period, three more shock tubes were put to work at the laboratory; they produced temperatures between 10,500° and 15,000°F, attained speeds of Mach 8 to Mach 20, and had [135] running times of 0.001 to 0.002 seconds.²⁵ Researchers believed that experiments with these devices would yield much knowledge, even though everyone involved with shock-tube work conceded that "it was a very tough area of research." Contending with flows that lasted for only a few thousandths of a second and that required a considerable amount of special instrumentation was "a fantastic problem." How were researchers "to get answers out of something like that?" ²⁶ Still, those passionate about high-velocity flows and high-temperature gases at Langley put great faith in the shock tube. The facility was used for much basic research including studies of shock waves generated by atomic bomb blasts.

Through the transition period of 1957 and 1958, researchers at the lab continued to seek new ways to accelerate hot plasmas to the tremendous velocities of reentry flight. In a method devised by Langley MPD enthusiast George Wood, a hot gas was fed into a tube, then the body force of crossed electric and magnetic fields was used to accelerate the gas to the point where a mixture of disassociated, high-enthalpy flow would reproduce the very high Mach numbers of hypersonic flight. At NASA's First Anniversary Inspection in 1959, Langley engineers demonstrated a crude version of Wood's crossed-field plasma accelerator. It produced a flash of light, a loud bang, a startled audience, and a belief in the promise of major new scientific findings.²⁷

Nearly everyone was excited by the potential of plasma accelerators. When John Stack first heard about the facility, he exclaimed, "This is great!" Stack felt that Langley should call the device something grand; he proposed the awe inspiring name, the "Trans-Satellite-Velocity Wind Tunnel."²⁸

Given the limited performance of Wood's early version of the experimental accelerator, such a pretentious name would have been a poor choice. As part of a guided tour for top officials from NASA headquarters in late 1959, Langley hoped to show off the radically new plasma acceleration device. Almost comically, it did not work. One embarrassed Langley engineer who watched the demonstration remembers, "We all sat around expectantly while Dr. [Adolf] Busemann explained the system. Then Busemann went over and threw the switch." Unfortunately, only "a little stream of red-hot particles sort of 'peed out' the end of this tube. It was a complete washout. Busemann just giggled and said, 'Well, we have a problem.' " ²⁹

The concept behind Wood's crossed-field plasma accelerator was sound: it was an application of a 130-year-old theory of electromagnetic force that had been expressed by Ampere in the 1820s. Langley researchers kept fiddling with the pilot model until in 1960 they successfully demonstrated its feasibility Having done so, they continued research on larger, more powerful versions of the device. One version, the 20-megawatt plasma accelerator, was completed in 1966 at a cost of more than $1 million. With this facility, the MPD Branch planned to achieve more accurate simulation of the reentry conditions of both manned and unmanned vehicles. Shakedown testing in the accelerator continued until 1969, when political pressures applied by the....

George P. Wood (right), head of MPD's Magnetohydrodynamics Section, developed Langley's earliest crossed-field plasma accelerator. The accelerator section of the 20-megawatt plasma accelerator facility is shown below. Note the many electrodes for furnishing the high-energy electric field.	.	L-62-8047
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L-66-1913

L-63-3361
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L-65-8509	.	In this April 1963 photo, MPD lab technician Charlie Diggs regulates the flow of a test gas in an early 10-kilowatt test version of Langley's Hall-current plasma accelerator (above); over his left shoulder sits a Polaroid camera for photographing an oscilloscope. In November 1965, an unidentified technician (left) wears goggles to protect his eyes against the intense light in a later coaxial version of a Hall-current plasma accelerator. In the test section, one can see the very bright, high-velocity plume from the MPD arcjet exhausting into a vacuum tank.

---

[138] ...Nixon administration forced an abrupt halt to the accelerator's pioneering work. Whether the machine would have ever completely panned out, no one can be sure.

In NASA's report on the last tests made in this device, published in 1971, George Wood and his colleagues pointed out that an exit velocity of 30,176 feet per second had been achieved, which was a remarkable 81 percent of the facility's computed capacity of 37,064 feet per second. According to the NASA report, the crossed-field accelerator "appears to be the largest and highest velocity nonpulsed linear plasma accelerator" to attain "an operable status."³⁰ An experimental facility with this record must be called a success.

While trying to work out the kinks in Wood's crossed-field accelerator design, Langley's MPD experts conceived several other methods for accelerating plasmas. One of these methods, which was not pursued very far, they called "microwave cavity resonance." The major alternative, however, was known as the "linear Hall-current accelerator." This type of plasma accelerator was based on a principle of electrical polarization and current generation laid out by the American physicist Edwin H. Hall in the 1920s and 1930s. The facility used a constant rather than intermittent interaction of currents and magnetic fields across a channel to accelerate a steady flow of plasma.

Beginning in the late 1950s, a small group of Langley researchers led by Robert V. Hess, an applied physicist from Austria who had come to work for the NACA in 1945, began pursuing two major variants of the Hall accelerator: the MPD arc and the so-called linear Hall accelerator. Throughout the 1960s, Hess and his associates refined these versions of the plasma accelerator, thus making extensive experimental and theoretical studies of the physics and overall performance of their devices. Although they successfully demonstrated the efficiency of the MPD arc and linear Hall accelerator and made several important findings relating to the manner in which oscillations and instabilities in plasma could develop into turbulent flows, MPD researchers were never able to simulate reentry conditions or the interaction between the solar wind and the geomagnetosphere, and they would never realize meaningful applications in space propulsion. As was the case with the other MPD experimental facilities mentioned, the linear Hall-current accelerator possessed limitations that Hess and his colleagues could not eradicate. By the late 1960s, Hess and others in MPD shifted the focus of their work with these accelerators to the potential application of gas lasers.³¹

In the late 1950s, the Langley MPD group found a stopgap method of generating a plasma in the laboratory. This method involved the production of a hot flame fueled by the combustion of cyanogen gas and oxygen.

MPD physicist Bob Hess was an intense researcher and bibliophile. He combed the current technical and scientific literature for ideas that might prove useful to his and his colleagues' work. Proficient in German and French as well as English, he was able to keep abreast of scientific ideas along several fronts. With his desk piled high with papers, Hess ferreted out the best notions, and massaged them for his own creative uses. ^**** In 1957, Hess came across a reference to a new experimental device at the Research Institute of Temple University in Philadelphia. This device produced an extremely hot flame by burning oxygen with cyanogen, a colorless, flammable, and poisonous gas, sometimes formed by heating mercuric cyanide. After reading about the cyanogen flame experiment, Hess hit on an idea for adapting the flame to create a hot plasma for simulating the space reentry environment. By feeding oxygen and cyanogen gas into a combustion chamber and igniting the mix, the researchers at Temple were producing a flame of more than 8000°F This was one of the hottest flames scientists had ever produced. What would be the result, Hess mused, if a potassium vapor that ionized easily at that temperature was added to the combustion chamber? Would [140] this create a jet of hot gas that reproduced the extremely ionized plasma conditions of missile reentry?

On 1I June 1957, Hess and his boss in the Gas Dynamics Laboratory, Macon C. Ellis, Jr., visited Temple University to discuss the details of producing a cyanogen-oxygen flame and to inquire about the feasibility of adding an easily ionizable alkaline material, potassium or perhaps cesium, to the flame. The key people to whom they spoke were Dr. Aristid V. Grosse, director of the Temple Research Institute, and Charles S. Stokes, who was in charge of the cyanogen flame program. Grosse and Stokes agreed that "the great stability of the combustion products" made them "well suited" for an addition of an ionizer such as potassium; they told the Langley visitors that they themselves had recognized this in one of their early reports, perhaps in the one that Hess had read. However, they had not made quantitative estimates of the electron densities or followed up on the idea in any way. They wondered whether the addition of potassium might not exert a cooling effect that would somewhat diminish the density of electrons. Hess, however, had already made the estimates and knew that the density of the electrons in the seeded cyanogen flame would be sufficiently high (about 10¹⁶ per cubic centimeter) to compensate for any temperature-reducing reactions.³²

At Langley, Paul Huber with the help of the facilities engineering group quickly designed a cyanogen flame apparatus, and the funding for its construction was approved. By the time the NACA became NASA, the device had been operating for several months. As expected, the first major test program conducted in Langley's alkali-metal-seeded, cyanogen-oxygen flame explored how flow-field conditions near an ICBM nose prevented the transmission of radio signals back to earth. Researchers in the Gas Dynamics Laboratory working with Joseph Burlock of IRD mounted a transmitting antenna in front of a nozzle that bathed the antenna in the hot cyanogen gas jet. Instruments then measured the rate at which the transmitter lost its signal power.

The early MPD test program demonstrated the feasibility of creating and controlling the highly ionized plasmas representative of the extreme dynamic conditions of spaceflight and reentry. The program also showed that certain simplified theoretical methods could be used to calculate the loss of electronic communication with a vehicle during reentry of a vehicle from space. If plasma conditions around the vehicle could be estimated with reasonable accuracy, researchers then would be able to predict the expected radio power loss. This was critical information for trips in and out of space by guided missiles, aerospace planes, and manned and unmanned spacecraft. Led by the outstanding theoreticians Calvin T. Swift and John S. Evans, who worked in the Plasma Applications Section under Paul Huber, MPD researchers at Langley continued to make significant contributions throughout the 1960s. On the problems of transmitting radio signals to and from reentry vehicles, no group inside or outside of NASA came to speak with more authority.³³

The MPD program was particularly valuable to the little known NASA project RAM. Initiated too late to help in the communications blackout problems of the Mercury and Gemini capsules, the purpose of Project RAM was to support the Apollo program. Many of the project's results proved inconclusive, and most of the hoped-for technological fixes, for example, the use of higher radio frequencies and the timed injection of small sprays of water into the hot gas envelope surrounding a reentering spacecraft, were judged too problematic for use in Apollo. However, MPD specialists at Langley did learn how to predict the flow-field characteristics of a reentering spacecraft more accurately, and their work led to viable schemes for alleviating or "quenching" part of the plasma sheath so that some level of effective radio communications to and from a reentering vehicle could occur.³⁴ Experience gained in the MPD reentry experiments of the 1960s eventually aided in projecting the reentry conditions of the Space Shuttle.

Not all of Langley's MPD work sought such direct technological applications as Project RAM. Some of the more fruitful research efforts fell into the realm of basic science and represented what MPD Branch Head Ellis de scribed in a February 1962 briefing to the Langley senior staff as "examples of keeping research alive on a reasonable scale without solid, specific applications or even the guarantee of applications!"³⁵ One such effort that made significant contributions was a barium cloud experiment designed for exploration of the interaction between the solar wind and the earth's magnetic fields.

Although a continuous outpouring of plasma appeared to emanate from the sun (i.e., the solar wind), this plasma by virtue of its high conductivity did not seem to penetrate the earth's strong magnetic field; instead, the solar wind flowed around the earth's field, forming a huge cavity. Sensitive magnetometers aboard some of the first Soviet and American spacecraft provided useful information about the disposition of the magnetic fields within this cavity; however, many questions about the arrangement of the field lines remained unanswered. Conservative estimates of the volume of the cavity placed it at about 60,000 times the volume of the earth. Langley's interested MPD experts knew that it was "going to be a formidable task indeed to map such an extensive field by point to point samplings."³⁶ Little was known about the shape of the cavity on the nightside of the earth, and indeed astrophysicists had suggested that the cavity was in fact open and that the earth's magnetosphere had a tail extending out some several "astronomical units."^*****

These were only some of the complications stirring the "intellectual stew" over the magnetospheric cavity. Other concerns stemmed from evidence that the magnetic field lines of the earth were linked at least partially with those of the interplanetary field, which in turn were entrained in the solar wind. If so, tangential stresses and drag forces in the realm of space affected motions within the magnetosphere in addition to those imparted by the earth's own rotation, which were themselves unknown.³⁷

At Langley, these cosmological matters were of particular interest to the small group of theoretically inclined researchers working in the MPD Space Physics Section under David Adamson. Beginning in late 1963, the Adamson group began to seriously consider a novel experimental technique by which scientists could use an artificially ionized plasma "cloud" as a space probe. As Adamson explained at the time, the principle of the cloud was rather simple.

[143] If a charged particle is projected into a magnetic field, it spirals along a magnetic field line, remaining tied to that field line until it is dislodged by colliding with another particle. Picture then a cloud of charged particles, sufficiently dispersed at a sufficiently great altitude that collisions can be ignored. The individual particles will be tied to the field lines, and motions of the cloud perpendicular to the field lines will be inhffiited. Of course, the cloud can and will diffuse along the field lines, and as it does so will serve to define the shaping of those field lines to which it is frozen. Moreover, if the magnetic field lines are themselves in motion, this motion, too, will be imparted to the cloud.³⁸

Only three requirements were placed on the cloud: it had to be fully ionized, the ionized atoms had to show resonance lines in the visible portion of the spectrum, and it had to be visible to observers on earth.

The notion of an ionized cloud was not new. For several years, research groups around the world had been experimenting with chemical releases as a means of exploring the nature of the upper atmosphere. For the most part, the creation of such artificial clouds was done by launching a sounding rocket carrying on its nose a payload of pyrotechnic constituents mixed with alkali metals. At the proper altitude in the upper atmosphere, a canister carrying the payload would be ejected. The temperature of the canister's contents would rise thousands of degrees and then escape explosively to form a colorful vapor whose atoms would glow blue violet in the sunlight. The result was a bright and rather beautiful space cloud, a sort of instant aurora, which could be seen quite distinctly by an observer watching from the nightside of the earth. Highly responsive magnetometers and spectroscopes could then be used to analyze the physics of what happened when a body of charged particles exploded in the outermost realms of the earth's atmosphere and at the fringes of space.

The world leaders in developing the tricky optical cloud technique were the West Germans, specifically a group of experimental astrophysicists in the Gaerching Laboratory of the Max Planck Institut in Berlin. The leading figures in the development of what came to be known as "the barium bomb" were Dr. Ludwig Biermann and his associate Dr. Riemar Lust. In 1951, Biermann had anticipated Parker's discovery of the solar wind by hypothesizing that a comet's tail, which always points away from the sun, was being pushed by streams of solar particles. He spent the rest of the decade looking for an experimental means by which to prove his theory. By the late 1950s, the Biermann group had developed a technique for the creation of an artificially ionized cloud in the upper atmosphere. By 1964, although the existence of the solar wind was by then taken for granted, the same group was ready to use more powerful rockets to deploy the first of these clouds in space.

Biermann and Lust used a payload of barium inside their canisters. In their opinion, a mix of copper oxide and barium (a soft, silver-white, metallic element obtained when its chloride was decomposed by an electric current) [144] was most desirable because it ionized at a reasonable temperature and even in modest concentration could produce clouds visible to observers on earth. In the early 1960s, French sounding rockets fired from the Sahara began carrying West Germany's barium payloads into the upper atmosphere as part of a research program sponsored by the newly founded European Space Research Organization (ESRO). NASA's space scientists naturally knew about the European program, and some of them thought, like Biermann and Lust, that the barium cloud technique could be adapted for experimental use in space.³⁹

In the summer of 1964, Bob Hess traveled to Feldafing, near Munich, Germany, to participate in an international symposium on the diffusion of plasma across a magnetic field. At this meeting, Hess spoke with Biermann about the barium cloud technique. The interest of the West Germans in the experiment was different from that of Langley's MPD Branch. The Germans wanted to release barium in the streaming solar wind outside the magnetosphere in the hope of learning more about the formation of comets; the NASA researchers sought to explore the magnetosphere itself. Nevertheless, the interests were similar enough to make Biermann and Hess agree that some measure of international cooperation would be useful.

Upon his return to Langley, Hess wrote a letter to NASA's Space Sciences Steering Committee. Founded in May 1960 by the head of NASA's Office of Space Sciences and Applications (OSSA), Dr. Homer Newell, this committee consisted of NASA officials and leading academic scientists in the field. Their duty was to advise NASA on its space science program and evaluate proposals for scientific experiments on NASA missions. In his letter, Hess summarized the observational possibilities of plasma clouds as magnetospheric probes and proposed that NASA devise a cloud experiment, which perhaps could be done with the cooperation of Dr. Biermann and the West Germans. Instead of launching the barium from inside a rocket, Hess suggested that the makings for the plasma cloud be released from inside the MORL that NASA was planning, "where the advantages of longer observation of the plasma cloud and of a wider choice of materials are offered as compared with observation from the ground through the atmosphere."⁴⁰

The space scientists at NASA headquarters were interested in the general idea, but plans to proceed progressed slowly through 1965 and 1966. Other space science experiments more directly supportive of the Apollo lunar landing program, like the Surveyor and Lunar Orbiter programs, received the highest priority. Still, the MPD Branch in conjunction with the appropriate program officers at NASA headquarters, as well as with the technical support of the Applied Materials and Physics Division at Langley, continued to plan for the cloud experiment. From Wallops Island, NASA would launch an explosive canister atop a high-altitude rocket.^****** Early on, [145] Langley researchers thought that the canister should contain a combustible mixture of cyanogen-oxygen with cesium; however, with input from Lust's team in Germany, they finally chose a barium payload. At the appropriate altitude in space (the rocket would not go into orbit), the canister would detonate and out would float the ionized particles which would form the space cloud. The cloud would last several minutes to more than one hour during which it would reflect radio waves and could be viewed from a location on earth in the sun's shadow.

The general scientific purpose of the cloud would be to serve as "a ready means of discerning on a large scale the topology of the earth's [magnetic] field and of determining magnetospheric motions." However, Langley's MPD group felt that the cloud might also be used as an aid in tracking high-altitude vertical sounding rockets or even vehicles (hopefully not Soviet) bound for the moon. It could be used as a form of visible tracer, not altogether unlike the use of certain metallic elements (often barium) and radioactive isotopes fed into the stomach or injected into the blood as tracers for X-ray diagnosis of cancer and other diseases.⁴¹

Eventually, NASA gave the go-ahead for the barium cloud-in-space experiment. The approval was in part politically motivated; NASA wanted to encourage international cooperation, at least in certain noncritical space endeavors, and especially with the democratic nations of western Europe. In June 1965, representatives of the Max Planck Institut approached NASA with a proposal for a joint barium cloud experiment involving German payloads and NASA launches from Nike-Tomahawk and Javelin rockets. The following month, NASA and West Germany's Federal Ministry for Scientific Research signed a memorandum of understanding calling for cooperation in a program of space research on the earth's inner radiation belts and aurora borealis. According to the memorandum, NASA would provide a Scout booster for the launch of a German-made satellite into polar orbit by 1968, with the results of the experiment to be made available to the world scientific community. Pursuant to another memorandum of understanding between the two nations (signed in May 1966), the two research agencies would then proceed with investigations of cometary phenomena, the earth's magnetosphere, and the interplanetary medium through studies of the behavior of high-altitude ionized clouds.⁴²

Four months later, on 24 September 1966, in a joint effort with the Max Planck Institut, NASA launched a four-stage Javelin sounding rocket from Wallops Island to check its canister-ejection technique, and on the next day, again from Wallops, launched a Nike Tomahawk rocket which released a mixture of barium and copper oxide. The second "shot" only reached 160 miles, whereas the desirable altitude for a barium cloud release was 3 to 5 earth radii. Nonetheless, the experiment was successful. For hundreds of miles up and down the Atlantic coast, three distinct clouds were visible. NASA and West German scientists photographed the clouds in an effort to track and measure electric fields and wind motions in the upper atmosphere.

[146] The results of both launches caused quite a public stir. Some residents along the coast reported sightings of brilliant UFOs, and some motorists became so fascinated by the brightly colored clouds that they ran off the road.

What came to be known formally as the MPI (Max Planck Institut)/NASA Magnetospheric Ion Cloud Experiment was the next step in the two parties' cooperative investigation. Proposed formally by the Germans in February 1967, the joint experiment was not approved by NASA until December 1968. According to the final agreement, the Germans would provide the barium payload, two ground observer stations and data analysis NASA would furnish the rocket, conduct the launch from Wallops Island and provide tracking and communications services.⁴³

Despite a fatal explosion on 5 October 1967, at the Downey, California, plant of North American Rockwell, which was caused by a mishandling of finely divided barium mixed with Freon, the barium cloud experiment eventually proved a great success.⁴⁴ On 17 March 1969, a barium cloud 1865 miles long, lasting some 20 minutes, and visible to the naked eye, formed at an altitude of 43,495.9 miles (69,999.87 kilometers). Heos I a "Highly Eccentric Orbiting Satellite" belonging to ESRO, carried the cloud-producing canister into space. Instrumented observation of this and subsequent plasma cloud-in-space experiments revealed the motions of the earth's magnetic field lines, including those influencing the aurorae; demonstrated other plasma effects in space; helped scientists to correlate these motions and effects as a function of solar flares; and generally allowed world astrophysicists to model the geomagnetosphere more accurately. All the barium cloud shots generated considerable public concern and interest and were widely announced in advance in the press.

Aside from fascinating the public, this experimental probing of the near-earth environment of space also led researchers to explore what was believed to be the great potential value of magnetospheric data for understanding and perhaps even controlling the earth's weather. Although the energies in space were recognized to be small compared with those in the atmosphere, those researchers interpreting the results of the barium cloud experiment raised the possibility that even small disturbances of inherently unstable regions in space could trigger significant behavior in large regions around the earth.

The few people outside Langley who remember the barium cloud research program believed NASA left most of the interpretation of the results to the Germans. In truth, as the NASA reports on the program demonstrate, Langley's space physics group moved ahead very quickly to interpret the data, "scooping" the preeminent Germans by first reporting and explaining in full many of the essential findings.⁴⁵

NASA Langley planned to participate in at least one follow-on barium cloud test in 1974 or 1975. The purpose of this proposed test was to shape the barium charge along a magnetic field line, then time the discharge to coincide exactly with the passage of an unmanned satellite having a very high-frequency (VHF) receiver aboard. The receiver would measure the [147] cyclotron radiation from the electrons circling the field line. The test did not take place, however, because of the lack of support in the OSSA at NASA headquarters.⁴⁶

Astrophysics was not the only driving force behind the explosion of MPD research in the 1950s. Another inciting factor was the quest for atomic energy. After World War II and the dawn of the atomic age, many physicists had begun exploring ways to confine plasmas magnetically in a new sort of nuclear reactor based not on fission but on fusion. Such projects were designed to explore the potential of generating thermonuclear power. Many researchers and institutions believed this was the pot of gold at the end of the MPD rainbow.

In 1951 the four-year-old U.S. Atomic Energy Commission initiated a secret project known by the code name "Sherwood"; its ambitious objective was the controlled release of nuclear energy through stable confinement of plasmas at an extremely high temperature. Interestingly, the strategy behind Project Sherwood was not to build a scientific and technical base for advanced fusion experiments; rather, the goal was to immediately develop a working technology. Researchers were "to invent their way to a reactor," so to speak, just as the scientists and engineers through a crash effort had built the first atomic bomb. Such was the mood of optimism and enthusiasm over the human capacity for solving any problem, however monumental, in the wake of the successful Manhattan Project.⁴⁷

Many of the devices developed during Project Sherwood served as advanced research tools. Although highly varied in their designs, almost all the facilities tried, with only partial success, to produce fusion reactions through some type of magnetic containment of a plasma. By the 1950s, scientists knew that a thermonuclear reactor would require a reacting gas with a temperature of at least 1,000,000,000 kelvin (K). Because containment of such an extraordinarily hot gas by solid walls seemed impossible, many plasma physicists believed that the only way to contain the gas was by powerful magnetic forces. Further work in MPD became vital.

At Langley, as elsewhere, researchers turned to the sun (a giant fusion reactor) to find the answers. In Langley laboratories, the MPD group worked on designing facilities that would simulate the activity of the solar corona. George Wood's MHD Section built several highly experimental devices to study solar physics; however, none of them yielded the secret of thermonuclear power.

Consider, for example, George Wood's first highly experimental facility for the basic study of solar-coronal physics, the one megajoule theta-pinch. [148] "The pinch" used a powerful, one-million joule^******* discharge of direct-current (DC) electricity along a single-turn coil to generate a strong longitudinal magnetic field. Wood's section hoped that an interaction of this high-density current with its own magnetic field would cause a contained column of plasma (that is, a molten conductor) to self-contract and become pinched even tighter and perhaps even to rupture itself momentarily, thus producing a controlled fusion reaction.

First explained in a theoretical paper by American physicist Willard H. Bennett in 1934, the application of this self-focusing pinch effect had become a basic mechanism of plasma and plasma-containment research worldwide in the 1950s. Langley's MPD enthusiasts (notably MHD's Nelson Jalufka) naturally wanted to get involved. Unfortunately, research in the Langley pinch facility, as in all other reactors of the time designed to generate controlled nuclear fusion, did not lead to fundamental breakthroughs It did, however, make some solid contributions to the literature.⁴⁸

Another device that perhaps did not live up to all expectations but nonetheless succeeded in fundamental respects was Langley's Magnetic Compression Experiment. In the early 1960s, Karlheinz Thom, Goetz Oertel, and George Wood devised an experimental apparatus capable of generating a multimillion-degree kelvin plasma for simulation of the solar corona and for studying the processes that produce highly ionized atoms in the corona. Completed in 1965 at a total cost of roughly $2 million, the apparatus consisted of a one-megajoule capacitor bank (a device for storing electrical energy) plus a straight narrow tube that produced a theta-pinch. Experiments conducted with this device led to some significant results on the spectral lines of highly ionized gases like deuterium and argon, and members of Wood's MPD group published several papers on the experiments into the late 1960s. Well after the dissolution of the MPD branch in 1970, the facility was still operating, thanks largely to the support of Karlheinz Thom, who had moved to a position of partronage in the OSSA at NASA headquarters. Thom was able to keep the Magnetic Compression Experiment alive by relating its research more directly to astrophysics, thereby circumventing a policy of the Nixon administration against basic research in the highly speculative energy field of thermonuclear fusion.⁴⁹

A third important fusion research effort of the MHD Section involved the plasma-focus research facility. Although the stated purpose of this facility (whose operation dates to the mid-1960s) was to simulate and study the physics of solar flares, its real purpose from the outset was to explore [149] the possibilities of fusion.^******** Essentially, the plasma-focus apparatus was a coaxial arrangement wherein a sheet of electrical current was created by a high-energy discharge from a powerful capacitor bank. The current sheet traveled down a ring-shaped (annular) channel designed around a central anode (positive electrode) and collapsed by virtue of its own self-induced magnetic field into a high-density plasma.

Several researchers in Wood's MHD Section became deeply involved in experiments with the plasma-focus facility, and although their work did not produce the boundless energy of nuclear fusion, it cannot be called a failure; rather, the effort, which was extensive, turned out to be important and lasting. Between 1968 and 1985, Langley researchers published no less than 81 papers based on their experiments in the plasma-focus facility; only 7 of these papers were written between 1968 and 1970, when the MPD Branch was still functioning. Clearly, the research did not end with the formal dissolution of the branch. In this collection of papers authored or co-authored by the members of the former MPD Branch are significant offshoots from the initial purpose of the experiments. These offshoots include exploration of space-based lasers both for direct conversion of solar energy and for early "Star Wars" designs. In the late 1970s, the plasma-focus facility received national and international attention and acclaim by producing more neutrons per experimental "shot"-1019 fusion neutrons from a deuterium plasma-than had been produced by any other fusion experiment to date in the United States. By placing enriched uranium at the end of the anode, researchers were even able to get 1010 fissions, which was another remarkable result.⁵⁰

These achievements signified that Langley's general fusion-related re search rated near the top of the American scientific effort by the early 1980s. Langley's work was equal to similar pioneering efforts by Winston H. Bostick at the Stevens Institute of Technology in New Jersey and G. R. Mather at Los Alamos National Laboratory in New Mexico. Of course, the chronology for this work extends beyond the period that is the focus of this book; however, the relevance of the research carried on by the MPD Branch of the 1960s extended to these significant follow-on efforts.

Although the promise of MPD remained high into the late 1960s, its mystique was slowly dissipating. In a briefing to new Langley Director Edgar M. Cortright in 1968, Mike Ellis had to admit that "a large part of the glamour of moving into plasma physics that existed ten years ago is now over and we feel that hard-headed research is now the order of the day.''⁵¹

Ten years had passed, and the ambitions of the first exhilarating moments of the spaceflight revolution had been moderated by the mounting frustrations of trying to achieve significant research results in what was proving to be a much more illusive area of research than anticipated. "The field was just so incredibly complicated," Mike Ellis remembers, "that to make a really significant contribution that would apply to some great problem just became increasingly hard." ⁵² The deeper the Langley researchers and others plunged into the MPD field, the more they realized how difficult contributing to any applications would be.

Because they could not find clear applications for most of their research, the sights of the MPD enthusiasts changed gradually over the course of the 1960s. In terms of simulating the reentry conditions, which was the practical application driving so much of the MPD effort in its early years, neither Langley's arc-jets, nor its plasma accelerators, nor any other new facility ever succeeded in generating on the ground a flow of high-temperature air that corresponded to actual flight conditions. And, by the late 1960s, NASA knew that a spaceflight program could do well without having that capability. As John Becker of Aero-Physics explains,

we learned everything that we could in an airstream that was way too cool, and then we corrected wherever we needed to for the effects of the temperature, by calculation, by studying the effects of temperature in adequate facilities, and then adding that to what we already knew it was a partial simulation, but the corrections were good enough to design successful hardware.⁵³

In other words, much of what MPD researchers had been trying to do just proved unnecessary.

The primary motivation for many who had joined the MPD field had been the hope of controlled thermonuclear fusion. Anybody and everybody in the scientific community who was connected to plasma physics had the dream of inventing the final device that would allow controlled fusion, or at least they hoped to contribute in some direct way to its eventual design. But by the late 1960s, the lack of progress in the field clearly indicated that any practical technology based on fusion (other than an atomic bomb or nuclear warhead) was still a long way off.⁵⁴

At the dawn of the space age, NASA's MPD enthusiasts at Langley and elsewhere had also believed that nuclear-powered rockets, ion rockets, and other advanced space propulsion systems might be just around the corner....

....and that with them astronauts would soon be shooting off for Mars and other faraway places. As the decade passed, the idea of the nuclear rocket fell by the wayside and was for all practical purposes killed when NASA planning for a manned Mars mission was put to an abrupt halt in 1970 by President Nixon. The value of exploring the potential of electric propulsion systems aIso diminished. Mike Ellis remembers the impact of the presidential policy on his own work: "In early 1970, I was told to cease working immediately on a paper I was preparing for formal presentation on the proposed manned mission to Mars. The paper, on which I was working with Walter B. Olstad and E. Brian Pritchard in the Aero-Physics Division, was all ready for rehearsal. But then word came down from Washington, and I was told not even to breathe the notion of a manned Mars mission." ⁵⁵

As their lofty aspirations were forced down to earth, the MPD enthusiasts shifted their focus and began to look for other objectives. A group in the Plasma Physics Section, for example, started to explore the potential of gas lasers. Under the direction of Bob Hess and his associate Frank Allario, this new area of interest grew into a sustained field of intense research at NASA Langley. By the early 1970s, this effort provided some information basic to the eventual development of the plasma cutting torches and plasma metal-definition apparatuses that have since come to dominate the metals field.⁵⁶

[152] In 1970, Edgar Cortright as part of his major reorganization of the center dissolved the MPD Branch and put most of its people and many of their facilities under a new Space Sciences Division headed by William H. Michael. Aware of MPD's practical limitations, Mike Ellis did not complain about his branch's dissolution, nor did any other member of his staff.^********* Cortright was somewhat familiar with the MPD field from his days as a researcher at Lewis laboratory and from his management experience in the OSSA at NASA headquarters, so he did not criticize MPD's work or refer to it in any way as a failure. John Becker, who had supported his MPD Branch for nearly a decade, best sums up Langley's view of MPD: It was "a field that we had to explore in detail because of the great promise. The fact that it didn't yield any earth-shaking new things is not our fault. It's just the way nature turned out to be."⁵⁷

Never before in the history of applied basic research at Langley had a field of study promised so much, yet delivered so little. But the "mad scientists" of MPD were not mad in their pursuit; they were just different from the "normal" body of researchers at Langley, who searched for practical solutions and did not stray into matters of fundamental cosmological importance. The MPD group's commitment to basic scientific research was in fact quite sensible. At a time when NASA had an increasingly strong political mandate for research that was "relevant" to the technological objectives of space projects, the "mad scientists" of MPD maintained a broader and more fundamental interpretation of relevant research.

Mike Ellis would always feel that MPD's interpretation was the proper one and that the urgency of project work had deteriorated the status of basic research at Langley. Project work so dominated the agency in the late 1960s that all work, even basic research such as that conducted by the MPD Branch, was judged by the black-and-white criteria for project success. Results must be quickly achieved and immediately applicable. The results of Langley's MPD work were neither. Mike Ellis puts the experience in perspective: "It is certainly true that we didn't produce any earth-shaking results or great breakthroughs. Not many efforts do."⁵⁸

^** In 1958, in support of Assistant Director Eugene Draley's initiative to advertise Langley's (then largely alleged) expertise in space science, Adamson composed an excellent paper on the principles of gravity . According to some experts, this paper, which NASA published, turned out to be "one of the best papers ever written" on the subject, as well as one of the most quoted. (Ellis audiotape, Nov 1991. author's transcript, p 18.)

^*** Ironically, neither Wood, head of the MHD Section, nor Hess, head of the Plasma Physics Section, held a Ph.D. Wood completed all the course work toward a doctorate in the early 1930s, but because of the Great Depression he had to go to work before receiving his degree; Hess graduated from the Vienna Institute of Technology and had taken graduate courses in fluid mechanics and thermodynamics at MIT in the late 1930s, but he also did not possess an advanced degree.

^**** For example, in 1945 Hess found an overlooked British translation of German aerodynamicist Dr. Adolf Busemann's seminal 1937 paper on sweptwing theory. Hess found it in the Langley Technical Library, where his future wife, Jane, would someday serve as the head librarian and assist him greatly with his search for references, and he passed it on to colleague Robert T. Jones. This was just prior to Jones's final revision of a confidential NACA paper in which Jones would report his independent discovery of the advantages of wing sweep for supersonic flight.

^***** An astronomicaI unit is usually defined as the mean distance between the center of the earth and the center of the sun, i.e., the semimajor axis of the earth's orbit, which is equal to approximately 92.9 X 1,000,000 miles or 499.01 light seconds.

^****** The type of rocket was yet to be determined. Ultimately, several sounding rockets, as well as Langley's multipurpose Scout rocket, would be used.

^******* A joule is equivalent to one watt-second.

^******** A much earlier piece of equipment for plasma research at Langley known as "the diffusion inhibitor" was developed to pursue thermonuclear power. In 1938, Langley researchers Eastman N. Jacobs and Arthur Kantrowitz tried to confine a hot plasma magnetically and thereby achieve a controlled thermonuclear reaction. Although NACA management quickly stopped the unauthorized research, the preliminary experiments attempted by Jacobs and Kantrowitz in their toroidal (or doughnut shaped) chamber represent not only Langley's first flirtation with the basic science later leading to MPD studies but also the first serious effort anywhere in the world (and three years before the Manhattan Project) to obtain energy from the atom. For a complete account of the Jacobs Kantrowitz fusion experiment of 1938, see James R. Hansen, "Secretly Going Nuclear," in American Heritage of Invention & Technology (Spring 1992) 7:60 63.

^********* Ellis himself, however, did not move into the new Space Sciences Division; instead, he became one of the assistant chiefs (and later associate chief) of John Becker's Aero Physics Division. Paul Huber, head of the Plasma Applications Section, became head of Aero-Physic's Propulsion Research Branch, which worked on hypersonic scramjets.

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