NASA’s Ames Research Center:
Contributions to Flight and Planetary Science

Note from the Editors: This issue’s lead article is the ninth in a series of reports describing the history and current activities of the planetary research facilities funded by NASA and located nationwide. This issue features NASA’s Ames Research Center, which has led NASA in conducting world-class research and development in aeronautics, exploration technology, and science since 1939. — Paul Schenk and Renée Dotson

This year marks the 80th anniversary of NASA’s Ames Research Center, situated in the heart of California’s Silicon Valley. Before the advent of both NASA and Silicon Valley, Ames was already evolving as a special place where state-of-the-art facilities and world-class talenIcing t melded to produce cutting-edge research in aerodynamics, thermodynamics, and simulation.

Basic and applied research have been cornerstones of Ames since it was founded in 1939 as an expansion of the facilities that the National Advisory Committee for Aeronautics (NACA) established at Langley Memorial Aeronautical Laboratory, now NASA’s Langley Research Center. Ames has always had a cadre of theorists, engineers, machinists, and computers (from humans to supercomputers) that have collaborated to solve the most urgent and interesting problems related to flight.

Flight, of course, requires some kind of an atmosphere. When taken metaphorically, an atmosphere provides an artful organizing theme to tie together all the different facets of research and the independent, expert, and sometimes eccentric, characters of the researchers themselves who have made Ames what it is over the years — the “atmosphere” of Ames as a place. When taken literally, an atmosphere is that immense, life-sustaining, gaseous ocean at the bottom of which we live and find refuge from the hazards of the space beyond Earth. After all, the first “A” in NASA is “Aeronautics,” and there is no way to get from Earth to space without passing through our atmosphere, just as there is no way to land on another world without passing through its own, however tenuous, otherworldly atmosphere. Atmospheres and the need to understand and adapt our technology to their structures, their behaviors, and their underlying physics have permeated much of the work at Ames.

NASA's Ames Research Center

Aerial image of NASA Ames Research Center. Credit: NASA.

Even though atmospheres are far from the whole story, the diverse areas of expertise at Ames today, from entry systems and aerosciences to cost-effective space missions, intelligent and adaptive systems, advanced computing and IT systems, air traffic management, astrobiology, life science, and space and Earth science, have sometimes evolved in concert with one another and, at other times, independently of one another. The interests of research leaders and their teams often accounted for the disciplinary shifts between the research fields.

When NASA succeeded the NACA in 1958, planetary science was hardly a leading justification for that shift, but NASA would soon develop strength in the field, and Ames played an integral role from the beginning. What follows are some key highlights from Ames’ past and present that have made — and continue to make — Ames the indispensable node it is within NASA and throughout the expanded networks of planetary science and space technology.

Ames Before NASA

Before NASA, there was supersonic flight. And before supersonic flight, there were problems affecting aircraft that ranged from icing to engine buffeting, all of which resulted from interactions with the aircraft and our atmosphere.

Icing studies were already underway at Langley and the leader of that effort, Lewis Rodert, brought that research to Ames and conducted it out of the first research building to open here. Aircraft were modified to collect data pertinent to the issue, and the results informed early solutions in thermal deicing that were built into a number of Allied aircraft during the war. Rodert would win the Collier Trophy for this research.

After the war, Rodert moved on to the NACA’s third laboratory, now NASA’s Glenn Research Center. Further pursuing the icing research into evermore refined and practical applications was not the cutting-edge theoretical work that was already dominant, and would continue to dominate, the work at Ames. There were also limitations to what sorts of icing conditions could be produced in wind tunnels.

Things getting cold proved to be a much less persistent issue of interest than having to deal with things getting hot and turbulent. Before the end of the war, there were already plans for expanding supersonic tunnel design. Ames had a supersonic tunnel with a 1 × 3-foot (30 × 91-centimeter) test section, but newer tunnels would be required to accommodate larger models and to get around other limitations that the dimensions imposed.

The new supersonic tunnel that was built proved incapable, initially, of operating in the transonic regime. Charles Hall, a longtime Ames researcher who will reappear in this story, led the modifications to the 6 × 6-foot (183 × 183-centimeter) supersonic tunnel to make it operational continuously from Mach 0.65 to Mach 2.2. The tunnel enabled basic research that resulted in the development of innovations such as the conical camber and improved understanding of vortex flows.

Even before NASA, however, Ames was not simply a world-class collection of wind tunnels. A complimentary and exceedingly practical, quick, and economical method of research was employed to collect transonic data that helped validate the supersonic area rule, a theory developed at Ames by Robert T. Jones, the American inventor of the swept wing. That method involved simply dropping models, often full scale, with their instrumentation from aircraft aloft. Rocket-boosted model tests would have been more expensive and time-consuming.

Harvey Allen

H. Julian “Harvey” Allen in 1957 in front of the 8 × 7-foot (244 × 213-centimeter) Supersonic Wind Tunnel test section. A blunt body model mounted in the test section is ready for testing. Credit: NACA.

As the 1950s progressed, plenty of rockets were being tested for their flight properties, and re-entry conditions proved to be a major obstacle to protecting the intended nuclear warhead cargo. The pointed nose cone shapes that worked so well aerodynamically at certain speeds could not withstand the thermodynamic heating that resulted from re-entry speeds at higher Mach numbers.

To solve the re-entry problem, a counterintuitive solution was proposed and developed by Ames’ most eccentric character and Smith DeFrance’s succeeding director, the chief of the Ames Theoretical Aerodynamics Section, H. Julian “Harvey” Allen. Allen’s blunt body concept addressed the fact that at re-entry speeds, thermodynamics became more important than aerodynamics. A blunt tip changed the bow shock wave in a way that shifted the heat away from the body’s surface out into the surrounding atmosphere, be it a capsule containing a warhead or, eventually, an astronaut.

Ames in the Apollo Era

The blunt body concept has remained an enduring innovation, as the concept continues to be applied to entry probe design today. Throughout the 1960s, the Mercury, Gemini, and Apollo capsule shapes were all tested in Ames’ facilities and refined as a result. In addition to thermal protection system research and heat shield testing, Ames also developed navigation systems, designed flight simulators, built magnetometers deployed on the Moon, and analyzed lunar samples to look for signs of life.

Along with Johnson Space Center, Ames was the only other NASA facility to analyze Apollo 11 samples in 1969. The Lunar Biological Laboratory contained a clean room — an integral part of the semiconductor industry — that was specifically designed and built to look for signs of life in the lunar samples. The Ames scientists in the Life Detection Systems Branch comprised a team of chemists, biologists, and microbiologists (about a third of whom were women) who tested 300 different environments using 10 petri dishes for each environment.

Those 3000 petri dishes were monitored for any signs of life. Of course, no signs of life have ever been detected, but the experience gained in Vance Oyama’s lab would later inform the Viking mission to Mars. For Viking, the biology team would be led by Ames’ Harold P. Klein, and Oyama served as the principal investigator for the gas exchange experiment.

Apollo benefitted from Ames’ expertise without redefining Ames as a center. As the Apollo-era budgets ebbed, the Center continued to advance the state-of-the-art in the cutting-edge fields that had pre-dated Apollo, while branching out into life sciences and the space sciences.

The Planetary Atmosphere Experiments Test (PAET)

Validation of the blunt body concept and stability testing of various re-entry capsule designs took place in the Ames hypervelocity free flight facility. Prototypes for the facility had been constructed in 1958 and 1961, achieving re-entry speeds with models launched into a counter-flow of gas in a shock tunnel.

One of the leaders of that research and technological development, Alvin Seiff, had designed a supersonic free flight tunnel at Ames that opened in 1948. By the 1960s, Seiff and David Reese, the Assistant Chief of the Vehicle Environment Division, had been considering how an entry probe could be used to determine atmospheric structure.

Seiff’s key insight was to invert the whole approach to hypervelocity aerodynamic research. Rather than determining the aerodynamics of a body traveling through known atmospheric conditions, how could a body of known aerodynamics be used to determine the atmospheric conditions? The solution would open up other worlds, literally, to the study of their atmospheres during probe entry. The result was the Planetary Atmosphere Experiments Test (PAET), a project that Reese managed through its design, development, and fabrication at Ames.

Planetary Atmosphere Experiments Test

A view looking down into the top of the completed Planetary Atmosphere Experiments Test (PAET) engineering model showing the details of the assembly’s components and wiring harness. Credit: Charlie Lonzo.

The PAET probe was outfitted with accelerometers, pressure and temperature sensors, a mass spectrometer, and a radiometer. The radiometer measured emission from the shock layer of the probe. Once fabrication of the PAET spacecraft was complete, it was loaded onboard a plane in May 1971 and sent to Wallops Station in Virginia for launch.

PAET launched from Wallops on Sunday, June 20, and splashed down near Bermuda within 15 minutes. Its entry speed was 6.6 kilometers per second (4 miles per second), high enough to require the rocket boost supplied by NASA’s Scout rocket. The Scout was NASA’s only solid rocket with orbital capability at the time, so the days of dropping a test probe from an airplane or even a high-altitude balloon like so many previous and successful aerodynamics tests would not have sufficed. The launch had been delayed two days because of antenna issues that the USS Vanguard sustained after encountering rough seas during its participation providing telemetry for an earlier Mariner launch. All the PAET’s systems functioned as designed and the payload continued to send data for over an hour as it floated, but it sank before the USS Vanguard arrived to retrieve it. Retrieval would have been a nice benefit, but it was never a requirement for the mission.

Not only did the mission give practical feedback about the behavior of the instruments under true atmospheric entry conditions, but the data the PAET returned overlaid beautifully with meteorological data from conventional soundings. Especially successful was the atmosphere structure determination, which returned a temperature profile accurate to within 1°C (34°F) over long stretches of the 80 kilometers (50 miles) in altitude from which it started recording.

PAET proved that a probe could enter an atmosphere while collecting data at planetary re-entry speeds, transmit that data before impact — but after emerging from the communications blackout phase of entry — and that researchers could then use that data to reconstruct an atmospheric profile. This validation on Earth led to its application in the planetary atmospheric entries carried out by Pioneer Venus, multiple Mars entries starting with both Viking landers, the Galileo probe to Jupiter, and the Huygens probe to Saturn’s moon Titan.

In concert with such practical, economical, and scientifically rich instrumentation at Ames was the equally important theoretical research into planetary atmospheres. Of the many talented scientists in the field, James Pollack deserves special recognition.

James Pollack

Pollack spent over 20 years at Ames until succumbing to a form of cancer at age 55. A researcher whose work embodied the connections to be drawn and the insights to be gained through the study of atmospheres and planetary science — and their humbling and profound influence on our understanding of Earth — Pollack was involved with every major planetary mission from Mariner 9 through Cassini, which launched three years after Pollack passed away in 1994.

He was the “P” in the famous “TTAPS” paper, “Nuclear Winter:  Global Consequences of Multiple Nuclear Explosions,” published in Science in 1983. At the time, Pollack was the chief scientist of the Ames Climate Office, a position he held from 1978 to 1984. For the publication, fellow Ames scientists Brian Toon and Thomas Ackerman contributed their expertise on cloud microphysics, climate, and radiation. Richard Turco, working for defense contractor R&D Associates, was the lead author. Carl Sagan was the “S.”

James Pollack

Dr. James Pollack of the Ames Theoretical Studies Branch. Credit: Wade Sisler.

Pollack had met Sagan at the University of California, Berkeley, when he was completing a master’s degree in physics while Sagan worked as a postdoctoral researcher. Their overlapping interests sparked a collaboration that would continue for the rest of their lives. After completing his master’s degree, Pollack became Sagan’s first graduate student at Harvard, where he completed his doctorate. Sagan’s own thesis had focused on Venus and, while at Harvard, Pollack’s doctoral thesis investigated the greenhouse effect in Venus’ atmosphere.

They were close collaborators and at the same time polar opposites in many respects. Sagan became a wildly popular communicator of science and pursued a broad array of research interests over the course of his career, while Pollack maintained a dedicated focus to planetary science and became renowned only within particular segments of the scientific community.

By the late 1960s, Pollack was looking forward to returning to northern California when Raymond Reynolds, the chief of the Theoretical Studies Branch, hired Pollack, who then began his career at Ames in 1970. Reynolds and Pollack both shared interests in the greenhouse effect and the atmosphere of Jupiter.

Pollack contributed to a number of fields within planetary science over his career. He advanced and refined models of greenhouse heating using data returned from Mariner 5 and Venera 4. He studied aerosols and their effect on the climate, developed numerical models for the physics underlying planetary formation of the gas giants, and contributed to the general circulation model that would become the Mars Global Climate Model.

He developed a reputation for seeing the big picture, and for providing cogent insights and suggestions to his colleagues. While not a computer scientist, Pollack supported the computer coding work through incredibly detailed handwritten notes to the programmers. His relationship with his own desktop workstation produced an amusing anecdote. Apparently unaware that his e-mail messages could be deleted, years of messages took up enough disk space that it led to trouble with his computer account. It’s worth considering the photo of Pollack at the computer in light of such a story, seeing someone completely at ease with physical theory, numerical theory, and even the associated algorithms, while remaining endearingly clueless about clearing out an inbox.

Pollack put the Ames supercomputers to work. Drawing upon his earlier work on Venus and the greenhouse effect, Pollack further developed radiative transfer algorithms that astronomer Allen Grossman and physicist Harold Graboske had applied to the evolution of low mass stars.

Pollack also drew upon Ames’ strength in airborne astronomy. Continuing the study of the clouds of Venus in early 1971, Pollack connected with Fred Witteborn, chief of the Astrophysics Branch at Ames. This led to airborne observations of Venus onboard an Ames Learjet in the summer of 1972 using an infrared telescope. The observations indicated that the venusian atmosphere contained sulfuric acid in high concentrations.

Artist’s concept of Pioneer 10 crossing the asteroid belt

Artist’s concept of Pioneer 10 crossing the asteroid belt. Credit: Rick Guidice.

It was an exciting time for planetary science. Pioneer 10 had launched in the spring of 1972, followed by Pioneer 11, both of which were managed at Ames. And with the success of the PAET and the lobbying efforts of Ames’ Director Hans Mark, NASA transferred the program that would become Pioneer Venus to Ames from Goddard. Charlie Hall, the manager of Pioneers 10 and 11, led that program as well, which sent two separate vehicles — an orbiter and a bus containing four entry probes — to the planet, both of which launched in 1978.

Pioneers 10 and 11

From 1965 to 1968, as human spaceflight attracted much of the attention that NASA received, a series of spin-stabilized satellites, identical in their basic design, carried various combinations of instruments into heliocentric orbit that measured solar wind and cosmic rays, magnetic fields, and cosmic dust. Those economical spacecraft, Pioneers 6 through 9, were managed at Ames and became the first spacebased solar weather monitoring network.

The next two missions to receive numerical designations, Pioneers 10 and 11, were also spin-stabilized and became the first two of only five spacecraft that have been sent on trajectories that have, or eventually will have, carried them out of the solar system. Pioneer 10 became the first to cross the orbit of Mars, pass through the asteroid belt, and reach the planet Jupiter. There, in 1973, its suite of instruments powered by radioisotope thermoelectric generators sent back the first data and images from the vicinity of the gas giant before its slingshot around the planet carried it out on its historic path. Pioneer 11 soon followed and was sent even closer around Jupiter and on to Saturn. Pioneers 10 and 11 were truly pioneers in every sense of the word, beginning the so-called “grand tour” of the outer planets, which culminated with the breathtaking imagery that Voyagers 1 and 2 would capture of not just Jupiter and Saturn, but also Uranus and Neptune, before eventually overtaking the Pioneers on their respective journeys.

Underscoring the momentous nature of the spacecraft leaving our solar system, Sagan spearheaded the effort to have the Pioneer plaques affixed to the craft. The amount of information about humanity carried onboard such a craft would soon be increased even more with the creation of the Voyager records.

Pioneer 10

Pioneer 10 interstellar plaque positioned on the spacecraft. Credit: NASA.

The Pioneers were both scientific and cultural achievements. The manager of the Pioneers, Charlie Hall, was known for conducting stand-up meetings because “people don’t talk so long when their feet get tired.” That reason was mentioned in Jupiter Odyssey, a 1974 documentary film about Pioneer that was but one example of how Pioneer was recognized in media.

The intersection between media and science was particularly evident in the Pioneer Image Converter System (PICS), developed by L. Ralph Baker of the University of Arizona. PICS allowed for a real-time display of the spin-scan images returned from the photopolarimeter and included a video signal. That signal, after creation of a synthetic green image of Jupiter from the scientifically more interesting red and blue channels that were simultaneously recorded by Pioneer 10, could be broadcast over television. In recognition, the San Francisco chapter of the National Academy of Television Arts and Sciences presented the Governors’ Award to Ames “for its outstanding contributions to the Science of television technology for its work on Pioneer 10 and the Jupiter remote telecast December 3, 1973.” So in addition to the scientific laurels Pioneer received, it also collected an Emmy.

From Airborne Science to Virtual Institutes

In 2015, as the New Horizons probe was passing by Pluto, Pluto passed between the line of sight from Earth to a distant star. This occultation was visible from the Southern Hemisphere and was captured by the Stratospheric Observatory for Infrared Astronomy (SOFIA), the only observatory in existence capable of positioning itself anywhere around the globe and above the vast majority of water in our atmosphere, a necessary capability for conducting infrared astronomy.

SOFIA is only the most recent example in a long line of airborne and infrared astronomy that dates back to at least the 1960s. While the advent of planetary spacecraft in the 1960s was a major development in planetary science, the concurrent developments in airborne capabilities have been indispensable, too.

Airborne science at Ames has looked both up into deep space and down to our planet below, enabling decades of research open to scientists from around the world. SOFIA’s predecessor, the Kuiper Airborne Observatory (KAO), was enabled because of the success that earlier platforms had achieved. And the success of the KAO led to its ultimate retirement in order to support the development of SOFIA.

Airborne observations were also a part of the Stardust mission’s re-entry. Stardust had passed through the tail of Comet Wild 2, collecting dust samples (as well as cosmic dust samples along the way), and returned those samples to Earth at the fastest re-entry speed of any spacecraft, almost twice the re-entry speed of the PAET.

Those samples, and the science surrounding their study, are indicative of the broader, interdisciplinary, and cross-pollinating nature of research that the figurative atmosphere of Ames provides. From lunar science to astrobiology, Ames has led the development of “virtual institutes,” which bring together researchers across disciplinary, geographical, and organizational separations that have historically restricted the flow of scientific communication and hindered collaboration.

Ames Today

In September of this year, astronomers using data from the Hubble Space Telescope detected water vapor in the atmosphere of exoplanet K2-18b. This exoplanet is one of thousands now known to exist in our galaxy thanks to the Kepler spacecraft, a mission for which Ames’ Bill Borucki served as the principal investigator.

Meanwhile, other promising developments are underway much closer to home. Over this summer, more than 200 employees of the U.S. Geological Survey (USGS) have been moving in at Ames in the NASA Research Park section of the campus. Both NASA and the USGS share a mandate to observe, study, and understand Earth.

This new co-location of scientific talent should enable some potentially very significant occasions for cooperation. There are opportunities for jointly developed tools for future satellite missions, as well as opportunities to enhance scientific returns through connecting USGS ground station data collection capabilities with spacebased observations, just as airborne observations have helped calibrate spacebased observations in the past.

And just as the PAET probe proved a capability on Earth for use on other worlds, so too may the resulting collaborative efforts between these agencies result in future methods and technologies that could be deployed throughout the solar system. It is only with the help of agencies such as NASA and the National Oceanic and Atmospheric Administration (NOAA) that the USGS can get into our atmosphere above ground level. Once up there, there are plenty of opportunities to study biology and geology aloft, which will only enrich work in other fields like astrobiology and the study of extremophiles.

Additionally, two NASA spacecraft currently in development — the Mars Helicopter Scout, which will accompany the Mars 2020 rover, and Dragonfly, a rotorcraft octocopter that will fly to various landing points on Titan — are the firsts of their kind that will take airborne science to other worlds. Ames is playing a role in each of these missions.

As we just celebrated the 50th anniversary of Apollo, its legacy is still with us. The Moon remains a promising and exciting source for scientific research today and Apollo samples are still contributing to that research. Just this year, NASA announced nine teams that have been selected to receive pristine samples returned from Apollo that have been stored untouched at Johnson Space Center. The Ames team will study their sample to investigate how exposure to the environment of space affects the surface of the Moon, often called “space weathering.” Since lunar science is so intimately tied to our understanding of how Earth formed, this research and the USGS co-location could present a unique opportunity for refining our understanding of Earth’s cosmic history while advancing the science and technology that supports Earth-monitoring.

Ultimately, our knowledge of Earth is a subset of planetary science. The enduring value of Ames as a Center is due in no small part to its ability to forge connections that support cutting-edge research and the development of our understanding of our place in the cosmos.

Suggested Further Reading

For the most recent overview of Ames history, see:
Bugos G. E. (2014) Atmosphere of Freedom:  75 Years at the NASA Ames Research Center. NASA SP-2014-4314, National Aeronautics and Space Administration, NASA History Office, Washington DC.

For a more detailed account of James Pollack’s work and reminiscences from colleagues who worked with him, see:
Marlaire R. D. (2017) James B. Pollack and NASA’s Planetary Missions:  A Tribute. NASA SP-2017-632, National Aeronautics and Space Administration, Washington DC.