The Aerospace Laboratories: 50 Years of Science in Support of National Security Space
The Aerospace Laboratories: 50 Years of Science in Support of National Security Space
Much of the history of Aerospace can be gleaned from the stories of the laboratories, which have been abuzz with activity in support of national security space since the founding of the corporation in 1960.
The founders of Aerospace—particularly the first president, Ivan Getting—believed that a strong scientific capability was needed to help the corporation fulfill its mission to “aid the U.S. Air Force in applying the full resources of modern science and technology to achieving continuing advances in ballistic missiles and space systems.” When the corporation was founded in June 1960, more than 200 members of the technical staff transferred from Space Technology Laboratories (STL) to Aerospace. Some of these scientists and engineers would form the core of the Aerodynamics and Propulsion Laboratory and the Plasma Physics Laboratory. The transfer also involved laboratory facilities in Building H (later renamed Building 130) and Building F (Building 120) of what was then Area A of the Los Angeles Air Force Station. In the fall of 1960 and the spring of 1961, the Space Physics Laboratory, the Materials Sciences Laboratory, and the Electronics Research Laboratory were also formed and housed in Buildings 120 and 130 and some nearby office trailers. Chalmers Sherwin, an expert in radar technologies and a physics professor at the University of Illinois, became the first vice president of the Laboratories Division.
The Tough Job of Getting Started
Developing laboratory research and technology activities in the midst of the formation of the corporation was challenging. Hiring staff was a priority, and travel to university campuses for recruiting often involved employees who had themselves been hired just a few months earlier. What was The Aerospace Corporation? What were the technical programs? These were common questions asked by students and faculty. Soon, new hires from university campuses near and far, as well as from industry, began arriving in the laboratories.
Only Building 130 and a small portion of Building 120 were configured as laboratory space, with the associated infrastructure—adequate power, water, fume hoods, and ventilation. Modifying buildings that were not designed to house laboratories was a never-ending struggle. Power was a particularly vexing problem. Successive additions of electrical power circuits created bizarre grounding configurations, ground loops, and a noisy electromagnetic environment. There were also embarrassing incidents when leaks from experiment cooling systems on the first floor of Building 120 caused water to cascade down onto Air Force offices below. This was definitely bad for Aerospace/Air Force relations! Moreover, procurement of laboratory equipment was initially governed by arcane rules that required elaborate justifications to the government, which caused immense frustration for the staff.
Despite these difficulties, morale was high. The work was challenging and exciting—right at the frontiers of science and technology—and generally perceived as vital to the security of the nation.
Evolution of the Aerospace Laboratories
The character and focus of the laboratories evolved in response to broader changes at Aerospace over the years. The Laboratories Division initially consisted of five organizations—the Plasma Physics Laboratory, the Aerodynamics and Propulsion Laboratory, the Electronics Research Laboratory, the Materials Sciences Laboratory, and the Space Physics Laboratory (these names changed slightly over time). Originally, the division also included Project West Wing as well as Technology Development Program Support, which assisted the Air Force in managing technology development in industry. In 1968, the Plasma Physics Laboratory was dissolved, and a new organization, the Chemistry and Physics Laboratory, was created. In the 1980s, in response to the need for greater expertise in information technology, the Computer Science Laboratory was created.
In the early days, the federal budget included a line item (649D) for Aerospace. Support for research and experimentation (R&E), technology development, systems planning, and foreign technology work (Project West Wing) were all drawn from this line item. Total research funding in the 1960s and 1970s consisted of R&E plus MOIE (Mission Oriented Investigations and Experimentation) and the Aerospace Sponsored Research Program. In retrospect, research was generously supported. For example, in 1967 the total funding for laboratory research was the equivalent of about 204 of today’s staff technical effort (STE). This level of support enabled the development of strong technical programs within the laboratories. The downside was that the laboratories operated, to a degree, in isolation from the remainder of the corporation and were viewed as expensive.
In the early 1970s, Aerospace was freed from congressional constraints prohibiting the construction of buildings and had accumulated sufficient financial resources to begin the planning of a modern laboratory located on Aerospace property. Much had been learned from the difficult experience of adapting Buildings 120 and 130, and the staff pitched in with great enthusiasm. The result was A6, a complex consisting of a central building surrounded by four laboratory pods. Operations moved to the new facilities and the leased Building D1 in 1976. In recognition of Ivan Getting’s role in creating Aerospace and his lifelong dedication to fostering science and technology, the A6 complex was named after him. Modernization and expansion of the A6 facilities continued over the years, and an addition was completed in 1983. A fifth laboratory pod was completed and occupied in 2010.
Over time, research funding in the laboratories decreased, mainly due to the decline and ultimate elimination in 1977 of the 649D line item. By 1983, research funding had fallen to about half of what it had been in 1967. The laboratories became, over time, much more involved in supporting the Aerospace program offices using their diagnostic and analytical capabilities. They also supported the corporation’s ventures into what is now called civil and commercial work. In short, the laboratories became invaluable partners to the Aerospace program offices, first in El Segundo and later at other locations such as Chantilly, Virginia.
As the focus shifted toward increasingly applied work, the distinction began to blur between the work done in the laboratories and the work done by the Engineering and Technology Group (ETG). This convergence, combined with the decline in the Aerospace ceiling that began in 1990, prompted efforts to reduce costs through consolidation of activities. At the same time, the word “laboratory” became politically incorrect, and a question that had dogged Aerospace since its inception—”Why does Aerospace have laboratories?”—resurfaced again in full force. Hence, Laboratory Operations became Technology Operations, and the laboratories were reorganized as “technology centers.” The Chemistry and Physics Laboratory and the Aerophysics Laboratory were dissolved, while the Computer Science Laboratory was transferred to the Computer Systems Division in ETG. Three organizations, the Electronics Technology Center, the Mechanics and Materials Technology Center, and the Space Environment Technology Center, emerged. In 1999, concern about the word “laboratory” had abated, and the organizations reverted to being called laboratories. In 2007, Laboratory Operations was renamed the Physical Science Laboratories (see sidebar, Technical Programs).
Organizational rearrangements and name changes of the laboratories came and went over the years, but the mission remained the same—to provide the best scientific input to the tasks of planning, developing, and operating national security space systems. It is not possible to do justice to all of the technical work done in the laboratories over the course of 50 years—at times, the laboratories employed more than 500 people—but this article will nonetheless present some of the highlights. Here follows a look at the laboratories themselves and some of the more intriguing research they pursued.
Rocket Science, Reentry Physics, and High-Power Chemical Lasers
Understanding the launch and reentry of ballistic missiles—flow fields, vehicle dynamics, heat transfer, propulsion—drove much of the early research in the Aerodynamics and Propulsion Laboratory. Research was conducted in a variety of facilities. The dynamics of maneuverable reentry vehicles was investigated in a shock tunnel. One investigation involved lifting reentry bodies designed to return astronauts from an orbital laboratory—forerunners of the space shuttle. Chemical rate coefficients associated with the nonequilibrium flow in rocket nozzles and reentry flow fields were investigated in low-density shock tubes. Laboratory contributions included seminal papers defining the nonideal performance of low-pressure shock tubes—information needed to deduce chemical kinetic rate data. Related work in chemical kinetics and environmental chemistry—a harbinger of today’s environmental research—was also carried out. Aerodynamics and heat transfer research was conducted through an electrically heated arc tunnel, which was used to provide a continuous flow of high-enthalpy gas for investigating ablative reentry heat-shield materials and related technology.
During the 1960s, the Aerodynamics and Propulsion Laboratory emphasized efforts to develop advanced test facilities. At that time, no arc tunnel facility in the United States was able to simultaneously replicate the high pressure and high enthalpy generated in the nose tip region of the slender, high-speed reentry vehicles then under development. In response to this limitation, laboratory personnel decided to use radiation from a high-power CO2 dynamic laser (which was in the early stages of development elsewhere) to investigate ablation in a high-pressure cold gas flow. The facility provided the high heating and pressure encountered by slender reentry vehicles. An experimental investigation of CO2 lasers was undertaken in the arc tunnel facility.
At this time, serendipitously, some staff members in the same laboratory were studying hydrogen fluoride (HF) laser radiation, which appeared in a narrow region behind a shock wave moving in a shock tube containing a dilute H2/F2 mixture. A collaboration between the two groups ensued, leading to the invention of the continuous wave (CW) hydrogen fluoride/deuterium fluoride (HF/DF) chemical laser, first demonstrated in the arc tunnel facility in May 1969.
Ultimately, the use of laser radiation to investigate reentry ablation did not prove useful, but it did lead to the invention of the high-power HF/DF laser. Power levels up to 10 kilowatts were achieved in the 1970s by Aerospace scientists. The TRW Systems Group in Redondo Beach, California, subsequently received U.S. Air Force contracts to build higher-power HF/DF lasers. Using a scaled-up version of an Aerospace design, TRW achieved 100 kilowatt power levels. This was followed by the MIRACL device, which achieved megawatt power levels; it is believed to be the highest power CW laser of any type.
Rocket Plume Phenomenology
Learning how to detect hostile rocket launches from space was a driving motivation in the early 1960s. A space-based global surveillance system would complement the ballistic missile warning radars already deployed and provide a “second phenomenology” for detection of launches, thus minimizing possible false alarms. Such a space-based launch detection system, when viewing Earth, would have to contend with background radiation from Earth’s atmosphere. Early spaceborne experiments developed by Aerospace flew on low-altitude polar-orbiting satellites measuring Earth’s background in the infrared (IR) as well as in the ultraviolet (UV).
As concepts for surveillance systems evolved, the expertise of laboratory personnel in the areas of combustion chemistry, flowfield physics, and radiation transport was increasingly employed to interpret observations of rocket plume radiation. Much of the initial work involved modeling. Aerospace scientists contributed through validation to the development of early plume radiation models sponsored by the DOD and also developed specialized analytical models to address newly discovered rocket plume phenomena. Models were also applied in the system engineering stages of future systems to improve performance and cost efficiency.
Subsequently, a broader program of laboratory measurement and field observations evolved in the Chemistry and Physics Laboratory (and later the Space Science Applications Laboratory) to support the expanding requirements of missile surveillance and defense programs. These studies included measurements of the optical properties of plume particulates, laser-induced fluorescence measurements of vibrationally excited plume gases, investigations of the UV and IR radiation from plume gas interactions with the atmosphere, and low-pressure flame measurements of afterburning chemistry. In the 1990s, concerns over the impact of launch activity on stratospheric ozone prompted laboratory scientists to develop models for the reaction of rocket exhaust gases with ozone. Unique measurements were performed to confirm reaction mechanisms, and a series of Air Force/NASA sampling missions was planned to measure ozone depletion within actual rocket plume wakes in the stratosphere. The airborne sampling missions continue today, with an added focus on potential rocket plume effects on global warming.
In the 2000s, a new capability was integrated with the model development and benchtop experimental work. Field observations of rocket launches at Vandenberg Air Force Base and of static engine tests at Edwards Air Force Base were initiated with a large suite of radiometers and spectrometers, some developed originally for astronomical observations and some built by laboratory personnel to acquire unique plume data.
The combination of fundamental laboratory measurements, field measurements on real rocket systems, and model development created a comprehensive rocket-plume chemistry and radiation program that supports a wide array of Air Force and Missile Defense Agency (MDA) surveillance, defense, and environmental programs.
Electric Propulsion Test and Evaluation
Electric thrusters have grown in importance as a means of adjusting the orbit of a spacecraft. While low in thrust compared to the rocket engines that propel launch vehicles, these electric propulsion systems provide a long, steady thrust that is important for constellation operations.
The Aerospace laboratories have been a central force in electric thruster test and evaluation since 1989, when the company’s Advanced Propulsion Diagnostic Facility became operational. The cylindrical test chamber measured 2.4 meters in diameter by 4.8 meters long and was equipped with an integrated molecular-velocity analyzer that could quickly obtain the velocity distributions of individual plume species. At the time, it was a unique instrument in the electric propulsion community.
Important projects in the early years included studies of a 1-kilowatt arcjet. Detailed measurements were made of thrust, plume dissociation fraction, rotational and vibrational temperatures, molecular velocity, and emission characteristics. These measurements were made with various propellants and for multiple operating points.
During a three-year period starting in 1992, Aerospace conducted an intensive test and evaluation of a British ion engine, eventually flown on the Artemis communications satellite. In addition to quantifying basic electrical and flow parameters, Aerospace was able to evaluate the thrust-vector direction and magnitude, grid deformation during operation, beam divergence, plasma density, plasma potential, electron temperature, ion charge distribution, ion velocity distribution, xenon neutral density, metal erosion rates, UV and visible emission, radio-frequency (RF) and microwave emission, IR emission, component temperature, microwave phase shift, and surface modification of spacecraft materials. This resulted in the most comprehensive set of evaluation tools for an ion engine anywhere in the world, and was a vital factor in establishing a baseline for ion propulsion in military communications satellites.
The length of the Advanced Propulsion Diagnostic Facility chamber was doubled in 1999 (to ~10 meters). Meanwhile, Aerospace was developing the world’s finest capability for measuring electromagnetic compatibility. These and other enhancements enabled Aerospace to perform plume particle, contamination, and electromagnetic compatibility measurements on low- to medium-power systems with a fidelity that often exceeded what could be performed elsewhere. In the last decade, Aerospace has evaluated most of the advanced electric thruster systems in the world.
The first operational use of electric propulsion by the Air Force Space and Missile Systems Center (SMC) was greatly facilitated by the test facility and electric propulsion knowledge acquired over the preceding decade.
Development of Composite Materials
The Aerospace Material Sciences Laboratory was a leader in the development of composite materials in the 1970s. Composite materials couple the characteristics of fibers—such as carbon—imbedded within a matrix of another (or the same) material. An ongoing interest in developing advanced reentry vehicles led to studies within the laboratory of advanced materials concepts. Researchers, through studies of the carbon phase diagram, discovered new allotropic forms of carbon. This was key to the development of carbon-carbon composites, whose properties were particularly desirable in high-temperature, high-pressure environments. Such composites were ultimately used in reentry vehicle nose tips as well as rocket nozzles and thermal protection systems for high-speed vehicles like the space shuttle. Their low coefficient of thermal expansion also made them suitable for components such as spacecraft antennas that required high dimensional stability. The laboratory also invented methods of infiltrating liquid metals into fiber bundles. This led to the development of metal-matrix composites, including graphite reinforcement of aluminum, magnesium, and other metals.
Composite materials technology blossomed in subsequent years, eventually transitioning from the research and development environment to the commercial sector so that today, such commonplace items as golf clubs and bicycle frames are made of composites.
Early in the history of Aerospace, it became clear that preflight detection of flaws in launch vehicle hardware was essential—but also important was the ability to reconstruct the causes of failure through a postmortem forensic science and engineering capability.
Accordingly, Aerospace developed critical capabilities in nondestructive evaluation (NDE). These capabilities played a crucial role in, for example, the rapid recovery of launch capability following the Titan 34D-9 launch failure on April 4, 1986, at Vandenberg and the April 1, 1991, Titan IV solid rocket motor upgrade test firing explosion at Edwards.
Over the past 40 years, Aerospace NDE researchers have been deeply involved in monitoring critical components of launch vehicles and satellites, reviewing contractor test and analysis data, and participating in the development and application of NDE methods at contractor facilities.
New NDE capabilities have also been developed. Examples include the flash thermographic methods used to inspect bonds between solar cells and their substrates and enhanced ultrasonic techniques for inspecting solid rocket motors. The Aerospace NDE laboratory is a state-of-the-art facility with capability for all the mainline NDE techniques including, radiography, ultrasonics, thermography, eddy-current testing, acoustic emission monitoring, shearography, microwave inspection, and enhanced visual methods.
Space Environment Research
Best known is the degraded performance of electronics caused by the effects of long-term exposure to radiation—but lesser-known effects can also cause serious consequences. Some of these are caused by particles energetic enough to penetrate vehicle shielding, while others are rooted in the presence of less-energetic charged particles. For example, electrostatic charging and discharge cause problems on spacecraft, and ionospheric variability causes problems with the propagation of radio signals. In low Earth orbit, further difficulties stem from the neutral gas environment, including variable drag and materials degradation caused by the presence of reactive gas species.
Aerospace first began conducting satellite investigations of the space environment in 1961. The research programs at the time were broadly focused on three areas: energetic space radiation, the upper atmosphere, and the active sun. The goal was to understand the little-known environment in which space systems must operate, so research centered on making and understanding appropriate measurements of the space environment (see sidebar, The San Fernando Observatory).
The 1962 high-altitude U.S. nuclear test Starfish dramatically demonstrated that artificial changes in this environment could also affect space assets. During this test, high-energy fission-product electrons became trapped and formed a new radiation belt around Earth. The failures of several satellites were attributed to the products of the Starfish test. Spurred by these events, Aerospace carried out many scientific investigations of the space radiation environment. Aerospace radiation models from this era were used to estimate the radiation environment for a variety of orbits. Their descendants, AE8 and AP8 (“A” stands for Aerospace), are the industry standards used today.
During the 1960s, the U.S. Air Force supported almost all Aerospace missions and instruments. A significant exception was an energetic particle instrument included on ATS-1, a NASA spacecraft in geosynchronous orbit. Aerospace instruments made the first measurement of the radiation environment in this operationally critical orbit.
During the 1970s, there was a change in focus for Aerospace research: electronic components based on new technologies were found to be much more susceptible to radiation than their predecessors. Effects due to single particles penetrating electronic components (single-event effects) were discovered, and deleterious effects from spacecraft charging to kilovolt potentials were commonplace. SCATHA (Spacecraft Charging at High Altitudes) and CRRES (Combined Release and Radiation Effects Satellite) were two investigations sponsored jointly by the Air Force and NASA to address these problems. Aerospace played an integral role in these missions, which took place during a time of growing support for the civil space program.
The SCATHA satellite was launched in 1979 and operated for nearly 10 years. It provided the measurements that form the basis for current spacecraft charging characterizations and the charging-related specifications for the design and construction of spacecraft that must survive in the near geosynchronous radiation environment. The data are still used to gain new understanding of the space environment and its interactions with spacecraft systems.
The CRRES project goals were to measure the near-Earth radiation environment and its effects on microelectronics and other spacecraft components, as well as to perform chemical releases in the near-Earth environment. Aerospace was in charge of systems engineering and oversaw the program for the Air Force. CRRES was launched into a geosynchronous transfer orbit in 1990. It was the first major science mission to the outer Van Allen radiation belt in a decade. The CRRES mission garnered an unparalleled set of measurements, which have since formed the cornerstone of current understanding of the radiation belts and their impact on space systems.
During the 1980s and 1990s, Aerospace increasingly looked to the civil space program to improve its understanding of the space environment. It was clear that a sustained course with multiple investigations was necessary. Two notable projects at the time were the Polar and SAMPEX missions. Polar was part of a larger effort to gain understanding of the solar-terrestrial regime as a connected physical system through which energy and matter flow from the sun into and through Earth’s magnetosphere. Polar was launched in 1996 and returned useful data for more than 12 years. Much has been learned about the space environment as a result, and Aerospace hardware produced key insights about how charged particles are energized and transported throughout the magnetosphere.
SAMPEX was the first of NASA’s small explorers. It was designed to measure fluxes of energetic charged particles in the magnetosphere, with an emphasis on the populations that cause single-event effects. The University of Maryland led the mission, and Aerospace built some of the hardware, assisted with engineering the instrumentation, and analyzed the measurements. The mission was launched in 1992 and is still providing useful data. The SAMPEX team made many discoveries, and its long span of measurements provides a vivid illustration of extreme variability in the space environment.
More recent NASA missions that have included Aerospace contributions include the Radiation Belt Storm Probes mission, which will use two spacecraft with identical instruments to explore the dynamics of the radiation belts under extreme magnetic storm conditions. Aerospace is contributing to the development of a suite of instruments to measure the energetic particle environment. NASA has also hosted a pair of sensors for the National Reconnaissance Office (NRO) on this mission, and Aerospace is providing the hardware. Thus, the mission is another partnership between NASA and national security space, and Aerospace is involved on both sides of the project.
Another current project is NASA’s Magnetospheric Multiscale mission, which will send four spacecraft through regions of the magnetosphere in which a phenomenon called magnetic reconnection occurs. The spacecraft will probe the fundamental physics of this phenomenon, and Aerospace will produce one of the components of the instrumentation. This basic research will help improve understanding of how charged particles are energized and transported in the space environment.
Aerospace’s involvement in space environment measurement now approaches the half-century mark. From modest beginnings flying instruments aboard low Earth orbit satellites, the program has encompassed experimentation covering virtually all of near-Earth space and has yielded valuable results.
Upper Atmospheric Research
Earth’s upper atmosphere is a dynamic fluid exhibiting substantial spatial and temporal variability at altitudes that interest operators of low altitude space systems. Variations in atmospheric density, if not taken into account, can cause ephemeris variations well beyond required accuracy limits.
Aerospace’s Space Sciences Laboratory initiated studies of the upper atmosphere leading to improved density models. This research consisted of measurements of atmospheric density, composition, and energy input into the atmosphere by instruments flown aboard satellites with perigees well below 100 nautical miles, as well as by experiments carried aloft by sounding rockets. This experimental work was backed by theoretical studies and analysis.
Air Force satellites carried Aerospace experiments aloft initially as secondary payloads in the 1960s and 1970s. Meanwhile, a primary research mission named OV1-15 was developed by Aerospace. This comprehensive atmospheric research mission was configured to measure atmospheric density, composition, and energy input globally over the altitude ranges of interest. The orbit of this spacecraft had a perigee of 94 nautical miles.
Three NASA satellites also carried Aerospace experiments into low-perigee orbits from 1973 to 1975. Aerospace also developed a unique concept to sense atmospheric density from orbit remotely without the need to dip deeply into the atmosphere. This could conceptually provide real-time information on atmospheric density variations on a global scale. A prototype of this experiment was flown aboard a Defense Meteorological Satellite Program (DMSP) spacecraft in 1979.
Aerospace also participated in the Polar Ionospheric X-ray Imaging Experiment (PIXIE) flown on NASA’s Polar spacecraft in 1996. PIXIE is a remote-sensing global monitor of high-energy electrons that precipitate into the ionosphere and atmosphere from the magnetosphere, contributing to the energy input into these regions.
Results from these missions, coupled with measurements by other organizations and analyzed by Aerospace theorists, led to improvements of atmospheric density models and improvement in low-altitude satellite navigation accuracy.
Spacecraft Surface Research
The effects of contamination on space systems have been studied at Aerospace for more than 40 years. This interest was born out of the inconsistent and unpredicted performance of spacecraft thermal control systems.
Surfaces exposed to the vacuum of space and solar and particulate radiation undergo changes that can alter the thermal balance of the spacecraft. Add to that the spacecraft’s own emitted “body odor,” which condenses on spacecraft surfaces, and the surface properties change even more.
In the 1970s, the SCATHA spacecraft was used to test the hypothesis that thermal control radiators were degraded by molecular film contamination. The source of the contamination was hypothesized to be the spacecraft’s own nonmetallic materials outgassing in the vacuum of space. Contamination-sensing instruments aboard SCATHA demonstrated that second surface mirrors (used for thermal control) achieved long life if spacecraft body vents were directed away from sensitive optical surfaces. This ground-breaking work altered fundamental spacecraft design, materials selection, and materials processing to minimize the effects of contamination.
In the mid-1980s, motivated by the observation that thermal control coatings (particularly white paints) degrade in space, the laboratories developed capabilities for studying the effects of space radiation on materials. The plan was to build capability for exposing multiple large samples of spacecraft surface materials to conditions derived from the actual mission environment. The approach was to marry existing (or Aerospace-developed) space environment models to actual exposure conditions. The plan was executed, and a world-class testing facility was developed and has now been extensively used for more than a decade to test materials slated for use in space. In many instances, what was thought to be good material was found, when tested, to have properties that would not meet mission requirements. The results obtained by this testing facility have affected numerous programs over the years, as materials slated for spacecraft thermal control, power generation, and surveillance have been tested for mission life performance.
Studies of Space Materials Survivability
During the height of the Cold War, there were serious concerns that nuclear or laser weapons might be used against U.S. national space assets. The Materials Sciences Laboratory participated in underground nuclear testing of materials’ response to weapons effects and performed high-energy laser testing on materials to ascertain their susceptibility. One result was the development of simulated space environmental testing to better understand how exposure to Earth’s radiation belts could affect materials. A 1985 outcropping of this research was the development of a thin-film optical coatings effort for research on techniques to make spacecraft optics and thermal control materials more likely to survive such attacks. The work initially focused on survivability, but was soon found to apply to the many spacecraft applications that needed improved performance from thin film coatings.
Since those early days, this group of scientists has participated in research and program support activities that have touched upon all aspects of thin film coatings for SMC and NRO spacecraft, including mirrors, filters, beam splitters, and solar rejection coatings for optical sensors, coatings for solar-cell cover glasses, and rigid and flexible thermal control materials. The group has built a number of custom thin-film deposition systems and pioneered several techniques for process automation that help enable the deposition of highly complex multilayer coatings needed for advanced spacecraft applications. Aerospace has also developed an extensive characterization facility that includes spectrophotometry, ellipsometry, scatterometry, and accelerated and long-duration environmental testing of thin films. Aerospace expertise accumulated over decades of work in this field has influenced how filters are designed and produced for a number of spacecraft and helped resolve anomalies found in optical systems during ground test or on-orbit operations.
In the early 1960s, electronics technology was driving toward ever shorter wavelengths for communications and radar applications—a trend that ultimately evolved into laser and fiber-optic communication. The centerpiece of the Aerospace work in millimeter-wave technology was a 15-foot-diameter radar/radioastronomy dish, operating at 100 gigahertz, mounted on the roof of Building 120.
The rooftop also housed control rooms as well as data reduction and data analysis electronics. A target/receiver facility was located atop the Palos Verdes Hills some 12 miles away.
Research using this facility involved astronomical studies of the sun, moon, and planets as well as experimentation on high-resolution radar concepts. The moist El Segundo environment was not optimal for radioastronomy studies at short wavelengths because absorption of radiation by atmospheric water vapor is substantial. Aerospace therefore acquired a site at Cerro Gordo, California, high in the Inyo Mountains, not far from Death Valley. This high-altitude site had only a minimal overhead moisture content and was potentially quite promising for astronomical observation. The vision was to establish an astronomical observatory there, possibly with support from the National Science Foundation; however, the National Science Foundation decided instead to build an observatory in the Andes of Chile.
The acquisition of the Cerro Gordo site and travel by Aerospace employees to establish the (minimal) facilities there gave rise to the legend that Aerospace owned an “executive retreat” in the mountains. The legend resurfaces every now and then!
The radio telescope atop Building 120 performed another important role: the guidance and tracking capability was used as a laser beacon for satellite calibration. The chemical laser facility was located in Building 130, just across the parking lot. Laser energy was transmitted via periscopes and mirrors across (and well above!) the parking lot to the rooftop of Building 120 and then up into space to calibrate and evaluate the performance of space systems, among these the Defense Support Program. The laser beacon facility has been reestablished with the completion of the A6 E pod in 2010.
Solar X-ray Astronomy
In parallel with ground-based research of solar activity, the Space Sciences Laboratory carried out measurements using instruments flown aboard rockets and satellites. The focus was on x-ray astronomy of the sun. X-ray emission from active regions on the solar surface is a manifestation of energetic solar plasma processes, which were thought to be related to (and possible precursors of) damaging particulate solar cosmic ray bursts. This experimental program relied on unique x-ray spectrometers developed by the laboratory and flown on Air Force satellites such as OV1-10 and OV1-17 in the 1960s. Rockets launched from White Sands and Kwajalein Atoll with similar instrumentation complemented the satellite-based measurement program. Of particular significance was the Aerospace x-ray spectrometer, one of the principal payloads flown on the Air Force Space Test Program satellite P78-1 launched in 1979. This payload, as well as the earlier measurements, returned fundamental information about atomic and thermodynamic processes in the solar atmosphere.
Aerospace scientists also participated in the research on solar activity carried out aboard the NASA Skylab mission in 1973 and 1974. The x-ray telescopes aboard Skylab, built by NASA, returned time-lapse x-ray images of the sun that showed the development of complicated solar plasma structures and solar active regions. One of the astronauts on Skylab, Ed Gibson, subsequently joined Aerospace as a member of the technical staff, continuing the research he first began during his time aboard Skylab.
The P78-1 satellite met a spectacular end. In 1985, it was the target of the first and only U.S. antisatellite weapons test, conducted well after the scientific goals of the spacecraft had been reached. The test was successful, and P78-1 was no more! Aerospace, thus, had a role both in the creation and demise of P78-1. The antisatellite program was managed by an Aerospace/Air Force team.
Advanced Microelectronics Research
In the late 1970s, Aerospace personnel became concerned about the availability of radiation-tolerant microelectronics for space. At that time, the space market was too small to interest commercial vendors of integrated circuits (ICs). Consequently, the manufacture of radiation-tolerant ICs was likely to be a niche market, with significantly different processing procedures than for mainstream ICs. Therefore, in 1980, the Aerospace board of trustees authorized development of the Very Large-Scale Integration (VLSI) facility at Aerospace, with a five-year commitment of support.
The VLSI facility was constructed in one of the laboratory pods in the A6 complex. A corner of the pod was retrofitted for a cleanroom environment and outfitted with the equipment necessary to fabricate silicon-based ICs at the 2-micron scale, which was then state-of-the-art. The goals of this effort were to fabricate 2-micron silicon-based ICs with processes optimized for radiation tolerance as well as performance. This would allow Aerospace to attract and hire world-class staff with interests in semiconductor fabrication and allow them to hone their skills in the critical area of radiation tolerance.
Construction of the VLSI facility was completed in 1984. In the early 1990s, it became clear that to stay even with technology advancements in the IC arena, it was necessary to move to the 1-micron processing mode. Furthermore, the path forward would be evolutionary, moving to the 0.5 and 0.35 micron scale, and onward with continuously decreasing transistor feature size for as long as possible.
During that process, the number of processing steps would increase from ~100 at the 2-micron scale to the more than 1000 necessary for current ICs. Moreover, it was evident that the development of fabrication lines to process ICs at those small feature sizes was going to become an exponentially expensive process. Thus, Aerospace abandoned the idea of a prototype development facility for radiation-tolerant ICs in the early 1990s.
At the same time, efforts were being made to develop capabilities for fabricating semiconductor devices using new growth techniques—e.g., molecular beam epitaxy and metal-organic chemical vapor deposition—that allowed fabrication of multilayer structures, including heterostructures and quantum wells. The goal was to fabricate state-of-the-art devices such as microwave transistors, laser diodes, and quantum-well IR photodetectors, all components of potential interest to national security space programs. However, the fabrication techniques involved the use of arsines and phosphines that are quite toxic. The resulting safety issues associated with the development of these systems caused at least a two-year delay in safety approval before the systems could be used. This part of the VLSI effort produced quantum-well photodetectors, IR detectors, GaAs, microwave FETs, and laser diodes, and as a serendipitous byproduct, helped recruit outstanding scientific talent. The ongoing safety concerns and the associated costs were factors that led to the termination of this effort.
Along with concerns about costs and safety, there was growing consensus at Aerospace that the corporation would be most effective by focusing on diagnostics and characterization of microelectronic parts rather than development of new processes and fabrication of parts. Consequently, Aerospace dropped the VLSI facility and the advanced device fabrication efforts.
Since that time—the mid-1990s—microelectronics efforts in the laboratories have focused on testing, diagnostics, and characterization. Aerospace has invested significantly in diagnostic tools and techniques such as scanning Auger microscopy, scanning electron microscopy, transmission electron microscopy, focused ion beam instruments, real-time x-ray imaging, and others. These are used extensively to support failure analysis and anomaly investigations.
The VLSI facility is now operated as the Nanoelectronics Research Facility, enabling small-scale scientific and engineering research into test structures and prototypes. These are fabricated using low-cost methods that allow investigation of approaches to improve the reliability and radiation tolerance of nanoscale microelectronic and optoelectronic devices. This niche area works well for Aerospace and its customers.
Microelectromechanical Systems and Picosatellites
In the early 1990s, engineers and scientists within the Space Materials Laboratory (formerly the Materials Science Laboratory) considered the use of microelectromechanical systems (MEMS) for space applications and the possibility of subkilogram satellites. Starting in late 1998, they built a tethered pair of 1 3 4 inch picosatellites. These were placed into orbit in February 2000. They were, and still are, the smallest active satellites ever put into orbit.
The initial PicoSat effort evolved into the DARPA-funded program that launched a pair of 4 4 5 inch nanosatellites in 2002 and another pair in 2006. Aerospace scientists and engineers have advanced the nanosat/picosat technology by developing systems, subsystems, and payload pico/nanosatellites. They have built and launched three 10 10 10 centimeter Cubesats and a 5 5 10 inch nanosatellite to monitor solar array degradation. Three more Cubesats are under development.
Testing and research of space batteries started in the mid-1970s to help resolve issues with nickel cadmium (NiCd) satellite batteries. There were new materials that were used in making NiCd cells, and sound methods were needed to assess and test them (for example, variations in the nylon separator were later found to greatly reduce life). At the same time, space mission durations were increasing, and developers needed ways to verify battery life. Work soon began on nickel hydrogen (NiH2) cells designed to replace NiCd cells.
The Aerospace battery lab was started from scratch in terms of facilities, equipment, and personnel. The emphasis was (and still is) on research to understand the key processes in battery cells and on testing to accurately simulate mission conditions. Cell research focused on understanding the relationships of the electrochemical, chemical, and physical process in the solid, liquid, and gas phases. Individual computer control of each test allowed accurate simulations of orbital electrical load and thermal conditions and ease of varying test parameters. Work on spacecraft battery applications focused on the nickel electrode—the limiting electrode for both NiCd and NiH2 cells. In the early 1980s, work with silver zinc and nonrechargeable lithium batteries was started to support launch vehicle programs.
Today, Aerospace has the most respected space battery lab in the country, and it supports essentially all national security space and launch vehicle programs. A combination of extensive and often unique laboratory capabilities are used to probe issues at the component, cell, battery, and power subsystem levels. These capabilities include a range of materials analysis tools and battery-specific nondestructive and destructive physical analysis tools, such as an in situ probe of liquid levels in operating NiH2 cells and a probe of cross-sectional electrode porosity. High-fidelity cell models that include all processes known to influence performance are available to help find causes of failures and to predict performances under a range of operational and storage conditions.
Highly experienced staff coordinate the research, testing, and modeling efforts. Direct impacts from the battery work for national security space include identification of a number of root causes of battery and cell failures, qualification of batteries for several programs, a number of extensions of storage life limits to save launch schedules and replacement battery costs, prevention of a number of launch delays, and extension of orbital battery life. The same type of work on space batteries has been requested by civil and commercial programs, and an effort has begun for a commercial electrical vehicle application.
Atomic Clock Research
The GPS concept was originated by Ivan Getting and brought to fruition by the first Air Force program director of GPS, Brad Parkinson, in the 1970s. GPS requires accurate timekeeping available only from atomic clocks onboard the satellites. Atomic clocks had evolved over time from huge instruments suitable only for use on the ground to relatively small devices compatible with space vehicles. However, the technology of spaceborne atomic clocks was still novel in the 1970s, and hence risky for space applications. Reduction of that risk was imperative.
In the mid-1970s, an atomic clock measurement and evaluation facility was created in the Electronics Research Laboratory to study the electronics packages of the clocks under development in industry. This capability evolved to also include the physics packages themselves—the cesium and rubidium atomic clocks. This capability, established in the Chemistry and Physics Laboratory, soon proved its value. Early failures of rubidium atomic clocks aboard the Block I GPS spacecraft were attributed to the loss of rubidium in the discharge lamps. A lamp-aging test was set up in the laboratory, and eventually, Aerospace proposed a physics-based, predictive model of rubidium consumption in the lamp and used it to establish appropriate minimum beginning-of-life fills of rubidium.
In the meantime, contractors had been developing and testing a space-qualified cesium-beam atomic clock thought to promise superior performance. Around 1983, it became clear that the signal used to lock the frequency of the clock output to the atomic transition used as a reference was steadily decreasing, and it was not clear whether (and how) that signal loss would affect clock performance. Aerospace built a dedicated cesium-beam apparatus, which demonstrated that the atomic beam signal loss was due to degradation of the last stage of the electron multiplier that supplied the signal, with little impact on clock performance.
During the mid-1980s, researchers on the Milstar program realized that quartz crystal oscillators onboard the spacecraft would not maintain the required time and frequency accuracy under certain scenarios, and concluded that the only way to meet those requirements was to fly atomic clocks. The Milstar program office asked Aerospace to support the clock development effort. One of the first actions was to share with contractors the results of investigations on minimum rubidium lamp fills, resulting in significant schedule and cost savings to the Air Force.
Through its investigation on the fundamental physics of atomic clocks, Aerospace developed the ability to accurately simulate an atomic clock’s frequency output, including all the noise processes actually found in atomic clocks. That ability also benefitted the Milstar program: Aerospace built a first-principles numerical simulation of the entire Milstar timekeeping system (space and ground segments) that was used in the 1990s by Aerospace, the contractor, and the government to validate approaches and detect and correct insufficiencies.
Since the 1990s, research in the Electronics and Photonics Laboratory has focused on using diode lasers to develop novel atomic clock technologies. This activity has investigated laser-pumped rubidium cell clocks as well as clocks using coherent population transfer techniques, which do not require microwave cavities and thus enable a great reduction in clock size. Novel clock technologies are now under investigation, which might lead to an all-optical ultraminiature atomic clock. Such an atomic frequency standard promises to do away with many of the problems affecting current compact atomic clock technologies.
Results of the atomic clock activities carried out in the laboratories have been regularly published in the scientific literature and presented in technical meetings. Aerospace is now a recognized leader in the field, chairing such meetings as the Precise Time and Time Interval (PTTI) Systems and Applications Meeting in 2008, as well as the IEEE International Frequency Control Symposium in 2007 and 2008. In 2008, Aerospace sponsored the prestigious 7th International Symposium on Frequency Standards and Metrology jointly with the Jet Propulsion Laboratory.
The challenges of maintaining low friction and wear in space were recognized in the early years of the space program, but spacecraft lifetimes were often limited by other subsystems. By the mid-1970s, however, it became clear that work in the area of tribology (the science of friction, wear, and lubrication) was needed to enable longer and more complex space missions; thus, research in this area began in the Aerospace laboratories.
One of the earliest lubrication tests at Aerospace conducted on mechanisms and bearing systems involved life testing of a despun mechanical assembly for the Defense Satellite Communication System (DSCS II), which began in the mid-1970s. This greatly enhanced understanding of the liquid lubrication of low-speed systems in vacuum. (When the laboratories moved to the newly opened A6 facility in 1976, the DSCS II despun mechanical assembly was moved across Aviation Boulevard in fully operating condition so as not to interrupt the tests!) In the 1980s, Aerospace conducted studies for the Operational Line Scanner for DMSP. A change in ball bearing design revealed that the silicone lubricant was decomposing and limiting the life of these systems. Aerospace compared the performance of potential replacement lubricants and recommended a new synthetic hydrocarbon oil, a polyalphaolefin. The new bearing-lubricant combination increased the operating life of the Operational Line Scanner by a factor of two or more. The longevity of the DMSP constellation owes much to this lubricant’s performance. Similar tests on GPS subsystems showed the general superiority of synthetic oils in space systems.
The current focus is on developing and testing solid lubricants and antiwear materials, evaluating synthetic oils and greases formulated with different additives, screening lubricant candidates, and developing life-prediction tools. The state of the art has advanced to make mission lives of 10 years and longer routine, but the bar continues to be raised in terms of performance and life requirements. The use of the latest scientific tools—such as atomic force microscopes to study surface chemistry, topology, and friction on the molecular and atomic scales—in concert with theoretical methods to evaluate surface chemistry, are leading to an ever increasing understanding of the fundamental interactions that drive the performance of tribological materials.
The Computer Sciences Laboratory was created in the mid-1980s in recognition of the increasingly important and diverse role that computer systems were playing in space programs. Initial research focused on computer program verification and mission assurance, and was later broadened to include computer networks, communications protocols, trusted systems, parallel computing, and intelligent systems. The laboratory pursued a combination of new research and application of these technologies. The work in trusted systems expanded over time to provide major support to the National Security Agency in its effort to define methods and perform evaluations of computer and network security products.
Based on the similarity of their tools and goals, the Computer Sciences Laboratory was merged with the Computer Systems Division within ETG in 1991.
The Future Beckons
The threats to U.S. security have evolved since the Cold War days. There have been dizzying technological advances, most of which were not predicted. What will the Aerospace laboratories be working on in the future? Here are some predictions made by the 2010 staff:
Electronic devices will shrink to the molecular level. Moore’s Law will finally “hit the wall” as electronic devices are fabricated out of individual molecules. Also, the fabrication of microelectronic devices will exploit the mimicry of biological systems (hierarchical self-assembly). Aerospace laboratories will therefore have more “quantum mechanics” and will need to develop unique microanalytical tools to characterize and assess devices at these dimensions. Moreover, the rise of synthesis via self-assembly will result in new interdisciplinary research activities that marry chemistry and biology.
The wave properties of atoms will be exploited to create a new detection paradigm. When atoms are cooled by lasers to extremely low temperatures, their wave properties become experimentally observable, allowing for the fabrication of atom-wave interferometers. Future gravimetry using atom-wave interferometers will provide for airborne or spaceborne characterization of gravitational anomalies with unprecedented sensitivity for underground structure detection. As they did in the related field of atomic clocks, the Aerospace laboratories will play a leadership role in this new, disruptive technology.
Quantum computing and quantum cryptography will become a reality. Quantum information processing is based on a two-state quantum system (qubit), which can be prepared in a coherent superposition of both states and, thus, can simultaneously be a “0” or “1.” Aerospace will play an important role in finding qubit realizations that are robust and can be easily scalable to large numbers of qubits.
There will be disruptive advances in power generation and storage. As the era of fossil fuel consumption draws to a close, national security space will be the beneficiary of dramatic technological advances in power generation, storage, and distribution. Power beaming systems will be deployed, and the development of space nuclear power systems will be revived. At the same time, “conventional” space power technologies will become increasingly driven by commercial development, analogous to the development of commercial microelectronics during the past two decades.
Ultrashort pulsed lasers will create a suite of new applications for national security space. Besides high-bandwidth optical communication (10–100 Gb/sec), the future will see new target recognition techniques, terahertz waveform generation, and revolutionary capabilities in adaptive frequency synthesis and waveform generation over an unprecedented frequency range. The chemical physicists at Aerospace will play a dominant role in the development and exploitation of these technologies.
Moore’s law will be applied to the fabrication of inexpensive, agile space systems. As Moore’s law and the voracious appetite of consumers has transformed centralized computing and analog systems into the interconnected world of the 21st century, this trend will lead to the rapid evolution of distributed microsatellites and nanosatellites that exceed the functionality of large centralized spacecraft. Aerospace chemists, physicists, and materials scientists will confront the challenges of developing spacecraft with dimensions on the order of 1 centimeter and distributed spacecraft systems from 100 meters to 50,000 kilometers in size.
As these predictions indicate, the Aerospace laboratories will continue to play a vital role in supporting national security space, which will see a growing need to “think big by thinking small.” The success of the Aerospace laboratories has been based on the ability to attract some of the keenest minds in the country—individuals who are always looking over the horizon to find the best way to apply their talents to incredibly challenging, interdisciplinary problems. As devices continue to shrink to the atomic level, the role of the physical sciences in the space business will only grow, and the discussion will be dominated by those who can speak the language of the fundamental laws of physics and apply that knowledge to the challenges of perfecting national security space systems.
What began in modest buildings on the Los Angeles Air Force Station 50 years ago has evolved into an experienced, agile team of dedicated scientists working in modern facilities—scientists who are eager to define and embrace the future. Ivan Getting would indeed be proud!
The author thanks the many people who contributed material and insights for this article, all of whom are part of this history of the Aerospace laboratories. These include Bern Blake, Jim Clemmons, Ron Cohen, Mike Daugherty, Joe Fennel, Gary Hawkins, Henry Helvajian, Warren Hwang, Bernardo Jaduszliwer, Bruce Janousek, Eric Johnson, Munson Kwok, Mike Meshishnek, Hal Mirels, Steve Moss, Dee Pack, Bill Riley, Hugh Rugge, Joe Straus, Gary Stupian, and Carl Sunshine. Andrea Miller was particularly helpful in finding historical material.
Aviation Week and Space Technology, (Aug. 7 and 14, 1961).
R. A. Becker, Space Physics at the Aerospace Corporation (The Aerospace Corporation, El Segundo, CA, 1969).
I. A. Getting, All in a Lifetime: Science in the Defense of Democracy (Vantage Press, New York, 1989).
The Orbiter, Vol. 16, No. 9 (The Aerospace Corporation, Sept. 16, 1976).
H. Helvajian and S. W. Janson, Small Satellites: Past, Present, and Future (The Aerospace Press, El Segundo, CA, and AIAA, Reston, VA, 2008).
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