NASA Ames Research Center
ADVENTURES WITH APOLLO
(Prepared in 1994 for the 25th Anniversary of the Apollo 11 Lunar Landing) Proud partners in the Apollo adventure, researchers at the NASA Ames Research Center embodied a long-standing work ethic of research and pure science. Those dedicated men and women offered their contributions to the Apollo effort quietly and without fanfare. While public attention focused on the spectacular events - lunar launches and the charismatic personalities of the space-suited NASA astronauts - Ames researchers in their ordinary work clothes and thoughtful expressions gathered the knowledge needed for success and tested their conclusions with painstaking precision. This behind-the-scenes approach in no way diminished the importance of the center's support in two key areas of the Apollo Project: technology development and scientific research. In the area of technology development, Ames contributed
a design that defined the Apollo's shape, thus making it possible for the spacecraft's safe reentry into the Earth's atmosphere. In scientific research, Ames scientists analyzed samples of rock and soil taken from the Moon, analyzed lunar craters, and measured and studied lunar magnetic properties. Ames also supplied critical astronaut training through the use of its simulators and other center facilities. The people at Ames were deeply committed to the Apollo quest. In fact, 'the whole country was caught up in it," says Palmer Dyal, currently (in 1994) Ames Deputy Director for Space Research. "There was a distinct feeling at Ames and throughout NASA to make things work. Our primary goal in selecting talent for the space program was simply to find the best. We were intent on ensuring success through the sheer intensity of our work, which was apparent even on weekends - when you could find the parking lots at Ames over half full." The payoff to this commitment was a mission that left us with both a legend and a legacy. Now, when we talk about Apollo, we cannot help but mention the way it changed forever how we look both at the Moon and the Earth. No longer can we look at the Moon without knowing that people from Earth once walked there. No longer can we think of our own planet Earth without being reminded of the photographs taken from the distant viewpoint of the Moon - showing Earth without political or economic boundaries and seen instead as a shimmering blue marble enveloped by a thin skin of life-sustaining atmosphere. No longer can we think of Earth without reflecting on the delicate balance of elements needed to ensure our own life and the lives of all that inhabit our planet.
Planning for a Round-trip
From the outset, Apollo missions were intended to be round trips. When President Kennedy in 1961 mandated NASA to send an American to the Moon before the end of the decade, he emphasized, 'and return him safely." This posed two problems: not only to launch a rocket out of Earth's atmosphere, but also to design a craft that could safely reenter the atmosphere from an orbital inclination. In the early days of space travel, the concept of returning a spacecraft to Earth presented a formidable problem. In fact, some prominent thinkers of the time were ready to conclude that reentry might not be feasible because of a so-called thermal barrier, or wall of heat, through which supposedly none of our spacecraft could travel. They believed that the ship would reenter Earth's atmosphere with meteoric speed and, like a meteor, would burn and be destroyed before reaching the Earth's surface. It was at Ames that the reentry problem was solved. The blunt-body concept, developed out of the inspired studies of H.J. Allen, was supplemented and further developed by A.J. Eggers, and D.R. Chapman. These Ames researchers showed that for almost every reentry of an object into Earth's atmosphere, convective heating would be minimized by a blunt configuration. Atmospheric air would, in fact, still be heated as it crossed the bow shock wave. But as the air rapidly swept around the object, most of the energy would harmlessly heat the air at a distance from the body, through action of the strong bow shock wave. Meanwhile, energy associated with friction heating would trail behind in a very hot wake and very little of that heat would remain on the blunt-nosed vehicle. That blunt-body shape, with the aid of companion research on thermal protection systems and materials (when applied first to ballistic missiles, and then to the Mercury, Gemini, and
Apollo crew capsules), solved the thermal barrier problem. Precisely which blunt-body configuration was best? Alvin Seiff, former Chief of the Vehicle Environment Division and the Supersonic Free Flight Branch at the Ames Research Center, says, 'We used the Free Flight Facilities here at Ames to test models of proposed spacecraft at the actual velocities at which they would enter the atmosphere. We thus were able to create in the laboratory the parameters of flight. Those studies led to the serendipitous discovery by my colleague Thomas N. Canning that the best shape for retaining a laminar (low heat transfer) boundary layer is a nearly flat front face. This led to the use of such a shape on the Mercury, Gemini, and Apollo capsules." Seiff and his research associates contributed to all of NASA's astronaut flight programs, including Apollo, and to planetary programs which followed. They provided
detailed analyses on flight stability and radiative heating, in addition to identifying configurations which could maintain laminar boundary layers for reduced heating. In their studies, they were able to observe the test model and the interactions between its shape and the atmosphere, its static stability (or ability to maintain its nose forward in flight), its lift and drag forces during flight, and its radiative heating (or transfer of heat to the body from white-hot gases enveloping it). The blunt-body concept has even influenced the design of the Space Shuttle. When the Orbiter ends its mission in low-Earth orbit, its position at a very high angle of attack presents the entire blunt-face underside of the Orbiter to the on-rushing air. After the Orbiter survives the interval of maximum heating, the angle of attack is reduced; thus, in the landing phase, the Orbiter can be maneuvered like an airplane.
In talking about work for the Apollo mission, Howard Goldstein, Chief Scientist of Ames Thermosciences Division, says, 'Once the blunt-body shape was decided upon, development could begin on the thermal protection materials and systems that would be required to protect the spacecraft from burning up during atmospheric entry." Many approaches were considered to solve this difficult problem. The approach finally chosen was an ablative heat shield. Ablation is a process by which the heat shield material is consumed by burning and vaporization, thus absorbing the intense heat created by air passing through the vehicle bow shock during atmospheric entry. Ablating materials were developed using the results of studies by Ames researchers Morris W. Rubesin, Constantine Pappas, John Howe, and other researchers at Ames in the late 1950s. They showed that surface transpiration was extremely effective in reducing both skin friction and
aerodynamic heating. The theoretical analyses were followed by experimental programs using Ames high-temperature wind tunnels demonstrating that transpiration could indeed be used to protect against aerodynamic heating and to quantify the effort. Materials that use passive transpiration cooling - ablation - were then adopted for the heat shields produced in the 1960s for nearly all NASA entry vehicles including Apollo. The heat shield materials, developed by industry, were analyzed and tested in Ames arc jets by John Lundell, Roy Wakefield, Nick Vojvodich, and others, in the 1960s. This research made major contributions to the design of the Apollo thermal protection system. 'The work on ablating materials and further studies on glassy meteorites called tektites," says Goldstein, 'led to a research program on the ceramic tile materials that currently are being used on the Space Shuttle Orbiter. Ames developed many of the heat shield
materials and performed a major part of the arc jet testing that made the reusable Space Shuttle Orbiter possible. As a result of the research starting with Apollo, Ames is now a world leader in development of thermal protection materials and systems technology."
On the Moon
After arriving on the lunar surface, one of the astronauts' chief tasks was to measure the Moon's mineral and chemical composition, its internal temperature, and its magnetic and electrical nature. To accomplish this, the Ames Research Center developed the Lunar Surface Magnetometer, an instrument built specifically to study the magnetic and compositional characteristics of the Moon. Four Apollo flights (12, 14, 15, 16) carried magnetometers and placed them in four separate sites from which lunar measurements could be taken. Four stationary and two portable magnetometers were developed. Each of the four stationary observatories contained a small computer that was programmed to automatically survey the site in which it was placed. The two portable magnetometers were placed on the two Lunar Rovers to measure magnetic fields during overland excursions on the lunar surface during Apollo 15 and 16.
Much about the history and physical state of the Moon has been revealed by these measurements. Two types of magnetic fields were measured by the magnetometers: permanent fields, indicating the presence of fossil magnetic materials and transient fields, indicating electric currents now moving deep inside the Moon's interior. Although the first measurements of the Moon's permanent magnetic field did not reveal an overall two-pole pattern of magnetism similar to that of the Earth's, they did reveal a stronger magnetic field than was expected. It was guessed that at some time in the Moon's past either the Moon possessed a strong magnetizing field itself or it was immersed in one. In addition, it was confirmed that the Moon was a solid mass and did not have an internal Earth-like dynamo. (Earth's dynamo is created by the slightly faster movement of the Earth's molten core inside the planet's more slowly moving outer crust.) Instead, these measurements showed that the Moon's magnetic field
resulted from local variations in the lunar composition and would vary from place to place on the surface. The Moon's transient magnetic fields were shown to be induced by changes associated with the solar wind. In addition, while the lunar surface magnetometer was measuring these fields, promising methods were discovered for exploring other Moon-like bodies, such as Mars. Captured for later study were measurements of the interior electrical conductivity and temperature profile of the Moon, its magnetic permeability and iron content, and the lunar field interactions with the solar wind. Results from these measurements led to the development of an orbiting satellite for mapping the permanent lunar magnetic fields and opened a new field of research for studying remnant fields on other magnetized bodies in our solar system.
Learning from the Lunar Soil
Exciting work was accomplished by analyzing the lunar materials returned to Earth. Ames was one of two NASA centers (together with Johnson Space Flight Center) to have created a Lunar Receiving Facility, Harold Klein, then director of Ames Life Sciences Division, recalls his role in helping to convince NASA to build such a facility at Ames, saying, 'whereas the facility at JSC was concerned with identifying and isolating materials because of harmful elements, we (at Ames) were less interested in harmful elements and more in the overall composition of lunar materials, especially organic compounds." Studies of this type required a very, very clean laboratory, and Ames scientists found many uses for the unique analysis facility. They painstakingly observed the biology and carbon chemistry of lunar samples to see if these items contained living materials and conclusively determined that lunar soils did not contain life. That finding, while not
a surprise to researchers, nevertheless prompted a whole new set of questions: Why is there no life? What kind of carbon chemistry occurs in the absence of life? What can we learn from this to better understand our own Earth? Later, they discovered that lunar soil was being bombarded by micrometeorites and by the solar wind (a stream of atomic particles ejected by the Sun). Such a bombardment precluded the existence of a soil chemistry dominated by life, as it is on Earth; but it left the lunar soil with a carbon chemistry dominated by the energetic interactions of the Sun, the Moon, and cosmic debris. In fact, the Moon's environment was found to be so sharply different from Earth's that their discoveries have helped to describe the chemistry of a 'nonbiosphere." This in turn has helped us better understand Earth's biosphere, both its origins and requirements. Having built the Lunar Receiving
Facility for analysis of the lunar materials, Ames used the facility again a decade later to test the concepts and equipment for the Mars Viking mission. Klein recalls that 'by the time the Viking mission came along, we received lunar materials to use as a control substance for developing tests for Viking equipment. We had already built the analysis facility, so we were logically in a position to use it to test equipment for Viking" The facility was also an important component when conducting studies about meteorites. Still driven by the search for life elsewhere in the solar system, researchers could satisfy this drive while using laboratories of the Lunar Receiving Facility.
When the Apollo missions had been completed, a total of 12 astronauts had walked on the lunar surface and had made six overland excursions in the Lunar Rovers. The American Space Program had accumulated more than 340 hours on the lunar surface and had carried back to Earth more than 840 pounds of lunar rocks and soil. The missions had also answered a fundamental compelling question: Was any life on the Moon? Although the findings were disappointing to some of us, scientists had long suspected the Moon's inability to support life. The tireless work of the dedicated men and women at the Ames Research Center supported many aspects of the Apollo mission, and in some areas it enabled the entire mission's success. To attempt a summary of the many legacies left by the entire Apollo mission would be futile. For the legacy Apollo gave to Ames, it is clear that the center's involvement in developing the blunt-body concept created opportunities for
studies of missions to the planets Mars, Venus and Jupiter. Two such missions, Viking to Mars and Pioneer Venus, performed in the 1970s with great scientific return, made intensive use of Ames research concepts as well as the participation of Ames scientists. The Galileo Probe, due to arrive at Jupiter December 7, 1995 (this document was published in 1994), for example, is a blunt-body probe that will explore the atmosphere of Jupiter. It will make measurements while entering the atmosphere (at 4.5 times the speed that Apollo traveled on its return to Earth). Galileo will take its measurements while descending into the atmosphere on a parachute to a depth where the pressure is more than 10 times that at Earth's sea level. Ames study of heat shields put the center in a pivotal position for work on thermal protection for the Space Shuttle. Other important work at Ames on lunar samples gave the center a logical role in conducting similar
studies for Martian samples. But perhaps the greatest legacy of the Apollo mission, not only to Ames, but the entire country, is the drama of a small group of humans striving as a team for success, while the world watched. All those who played a part in the Apollo effort can be proud to have participated in one of the most important events of the 20th century. -end-
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