Engineer Special Study of the Surface of the Moon (1960-1961)

Engineer Special Study Sheet 1: Generalized Photogeologic Map of the Moon. Please click to enlarge. Image credit: USGS.

The race to the Moon began on 17 August 1958 and the Soviet Union won. This isn't the opening line of an alternate history story; rather, it is an acknowledgment that more than one Moon race took place. The first, with the goal of launching a small automated spacecraft to the Moon, began with the liftoff of the Able 1 lunar orbiter, a 38-kilogram U.S. Air Force (USAF) probe. (It was later re-designated Pioneer 0.) Able 1's first stage, a Thor missile, exploded just 77 seconds after launch from Cape Canaveral, Florida, ending the world's first attempted lunar mission.

A month later, on 23 September 1958, the Soviet Union joined the race. A spherical Luna probe intended to impact the Moon fell victim to the failure of its upgraded R-7 booster rocket just 93 seconds after liftoff from Baikonur Cosmodrome in central Asia.

On 11 October 1958, the USAF launched Able 2, a near-copy of Able 1. It was the first lunar launch conducted under NASA auspices. The civilian space agency had opened its doors on 1 October 1958. NASA absorbed most Department of Defense space projects, though in practice the USAF and U.S. Army continued to carry out missions while interagency relations and lines of command became defined.

Able 2, later re-designated Pioneer 1, burned up in Earth's atmosphere on 13 October after its Able rocket second stage shut down early, placing it on an elliptical path that took it about a third of the way to the Moon. The Soviets launched their second Luna Moon impactor just 16 hours after the U.S. launched Able 2. The unnumbered Luna's upgraded R-7 launch vehicle exploded 104 seconds after liftoff.

And so it went, with launches from Florida and Kazakhstan alternating and failing. The Pioneer 2 lunar orbiter (8 November 1958) and another Luna impactor (4 December 1958) fell victim to premature launch vehicle shutdowns. Pioneer 3 (6-7 December 1958), the first NASA/Army Moon probe, was launched on a U.S. Army Juno II, not a USAF Thor-Able, but performed much as had Pioneer 1.

First attempt: Thor-Able 1 launches Pioneer 0 (17 August 1958). Image credit: Air Force Air & Space Museum. 

On 3 January 1959, the Soviet Union snatched victory from the jaws of defeat. Their Luna 1 impactor missed the Moon by 6400 kilometers, and so failed to accomplish its mission. It sailed on, however, becoming the first human-made object to orbit the Sun. The Soviets nicknamed it Mechta ("dream"). The U.S. Army launched the Pioneer 4 lunar flyby spacecraft two months later (3 March 1959). It failed to return images of the Moon, but repeated Mechta's feat.

Another unnumbered Luna impactor fell victim to an R-7 failure on 18 June 18 1959. Then, on 14 September 1959, on their sixth attempt, Soviet rocketeers succeeded in striking the Moon with the Luna 2 impactor. The probe struck near the center of the Moon's Nearside, the hemisphere that faces the Earth. Three weeks later (6 October 1959), Luna 3 flew 7900 kilometers over the Moon's south pole and imaged the hidden Farside hemisphere.

In a last-ditch effort to steal the Soviet Union's thunder, the USAF and NASA decided to give a planned Pioneer Venus orbiter a new mission: orbit and photograph the Moon at close range. Its mission ended 104 seconds after liftoff on 26 November 1959, when its Atlas-Able launcher lost its streamlined launch shroud and tumbled out of control.

As the first Moon race ended in Soviet victory, pressure built in the U.S. for a rematch. Though President Dwight Eisenhower had made it clear that the Department of Defense branch services should concentrate on space and rocket projects with immediate military applications, the Moon still beckoned to U.S. Army and USAF rocketeers.

The U.S. Army and the USAF studied lunar surface bases even after the creation of NASA. The Army Ballistic Missile Agency emphasized Project Horizon, a lunar fort, while the USAF worked with contractors on the SR-183 Lunar Observatory project. LUNEX was a USAF study of an early manned lunar expedition. The USAF also began lunar mapping using Earth-based telescopes.

Moon fort: Project Horizon lunar base. In this painting from 1959, a U.S. Army crew lander arrives at the landing field in the background, beyond which lies a jagged line of mountains. In the foreground, habitat modules are buried in an excavated ditch for micrometeoroid protection. Image credit: National Air & Space Museum.

The first attempt to map lunar features for scientific and engineering purposes did not, however, originate within the Defense Department. It was begun instead by Arnold Mason of the U.S. Geological Survey (USGS) Military Geology Branch in Washington, DC. According to Don Wilhelms, writing in his 1993 memoir To a Rocky Moon, the peripatetic Mason became interested in lunar geology after the 4 October 1957 launch of Sputnik 1. Mason's boss, Frank Whitmore, soon got caught up in his enthusiasm. Whitmore, incidentally, served as Secretary of the Geological Society of Washington.

Early in 1959 — soon after Luna 1 — Mason proposed to carry out an analysis of the Moon's alien terrains to determine their suitability for spacecraft landings, travel on foot and by rover, and base construction. With Whitmore's blessing, he enlisted Robert Hackman and Annabel Brown Olson of the USGS Photogeology Branch in his project. Mason became project chief, Hackman became Mason's co-author, and Olson (who, according to Wilhelms, received insufficient credit for her labors) assisted Hackman. At first, they had available only meager USGS funds. Soon after Luna 2 and Luna 3, however, the Army Corps of Engineers funded their study.

Mason and Hackman's assessment took in only the Nearside. They based their analysis on photographic plates from large telescopes on Earth, which under the best viewing conditions could (they estimated) reveal features on the moon no smaller than about a mile across. In fact, features 10 miles wide were barely discernible in most of the photographic images they used.

Their work soon drew in as consultants lunar experts Gerard Kuiper (McDonald Observatory), Eugene Shoemaker (USGS Menlo Park), and Robert Dietz (Naval Electronics Laboratory). All three supported the impact hypothesis, which stated that most of the Moon's craters are asteroid impact scars; not, as some believed, volcanic calderas. At the time, planetary astronomer Kuiper was hard at work on a USAF-funded lunar photographic atlas; Mason and Hackman would use it near the end of their study. Shoemaker, meanwhile, was busy refining a prototype lunar geologic map of the region containing the large, relatively young crater Copernicus; Hackman would later assist him with identification of lineaments in the Copernicus region.

The Army Corps of Engineers published the first edition of Mason and Hackman's four-sheet "Engineer Special Study of the Surface of the Moon" map set in July 1960. USGS published a second edition with "minor revisions" the following year.

The "Engineer Special Study" was significant in part because its Sheet 1 (top of post), titled "Generalized Photogeologic Map,” was the first major lunar map to show stratigraphic relationships: that is, it attempted to display the chronological order of the formation of the Moon's surface features. Mason and Hackman's stratigraphic system centered on the formation of the maria (Latin for "seas"), the relatively smooth, dark-hued plains that mottle the Nearside. They make up about 20% of the Moon's surface.

Mason and Hackman colored orange the heavily cratered, light-colored "pre-maria" terrain; that is, landforms that they believed were already in place when the maria formed. They colored maria yellow, while green indicated "post-maria" features; mainly young asteroid impact craters, but also features that they interpreted as being of recent volcanic origin. They used black dots to mark what they identified as volcanic cones and domes and thin black lines to mark what they thought were tectonic faults.

Their stratigraphic map, though pioneering, was too simplistic to accurately portray the Moon's history. Most of the maria basins formed at different times during the first billion or so years of lunar history, so features associated with them often overlap. An impact crater blasted into an older mare (Latin for "sea") would, for example, become a pre-maria landform by Mason and Hackman's reckoning if it became engulfed in ejecta and lava from a later basin-forming giant impact. In addition, some prominent lunar features identified as pre-maria (the Apennine Mountains, for example) should have been represented by a fourth color to signify that they are non-maria features created by the same giant asteroid impacts that excavated the maria basins.

By contrast, Shoemaker's nearly contemporaneous prototype Copernicus geology map, printed in small quantity by the USAF Aeronautical Chart and Information Center in April 1961 but never formally published, identified five stratigraphic "systems." From oldest to youngest, these were the Pre-Imbrian, Imbrian, Procellarian, Erastothenian, and Copernican systems. Even this would turn out to be simplistic, however, once robot and human explorers began to provide lunar geologists with close-up images and samples of the Moon's complex terrain.

Engineer Special Study Sheet 2: Lunar Rays. Please click to enlarge. Image credit: USGS.

Engineer Special Study Sheet 3: Physiographic Divisions of the Moon. Please click to enlarge. Image credit: USGS.

In sheet 2 of the "Engineer Special Study," titled "Lunar Rays," Mason and Hackman plotted the source craters and extent of the Moon's most prominent ray systems. They correctly identified the light-hued rays as ejecta blasted out from young asteroid impact craters.

Mason and Hackman's Sheet 3, titled "Physiographic Divisions of the Moon," was their most ambitious. In it, they applied photogeologic principles pioneered on Earth to identify more than 70 different lunar terrain units.

Sheets 1 through 3 laid the groundwork (literally) for Sheet 4, on which Mason assessed in writing the landing, travel, and construction conditions in each of the physiographic regions on Sheet 3. What follows are summaries of his assessments for several regions that have been visited by spacecraft.

Luna 2 struck the southern flank of Autolycus crater in the northern part of Mason and Hackman's Apennines Region. According to Mason and Hackman's analysis, Autolycus is a post-maria impact crater, only lightly rayed, on the western edge of Mare Imbrium, in the extensive Mid Lunar Lowlands. Mason wrote that the surface in the Apennines Region is rough and blocky, so landings there would be very difficult. Movement in the region would, he judged, be the "most difficult on the [M]oon's surface, and possible only by carefully selected routes." Construction would be "very difficult because of blocky material and steep slopes."

James Irwin salutes Old Glory at Hadley-Apennine in a photograph captured by Apollo 15 Commander David Scott. The Lunar Module Falcon and the Lunar Roving Vehicle Scott and Irwin used to explore the Hadley-Apennine site glitter in the harsh morning sunlight. The surface material around Falcon is rolling and loose with few large rocks. Mount Hadley Delta, about 4000 meters tall and rounded by billions of years of small meteoroid impacts, stands behind Irwin and Falcon. Image credit: NASA.

Luna 2 was not designed to return images as it plunged toward the Moon; however, the Apollo 15 Lunar Module Falcon landed west of the Luna 2 impact site on July 30, 1971. Astronauts David Scott and James Irwin found the area to be cratered and rolling, but difficult neither to land on nor to navigate on foot or by rover. The surface material was loose to a depth of many meters. The nearby Apennine Mountains, which Mason and Hackman had envisioned as steep and jagged, turned out to have been rounded and partly leveled by micrometeoroid impacts over the nearly four billion years since their formation.

NASA's Ranger 7 probe was designed to return images of the lunar surface as it fell toward destructive impact. On 31 July 1964, Ranger 7 returned more than 4300 photos of the area between Oceanus Procellarum and Mare Nubium. 

Mason and Hackman had called the area containing Ranger 7's impact site the Riphaeus Section. It was a lowland maria divided by the highland Riphaeus Mountains. Mason judged that landing and movement would be "generally easy" if blocky isolated pre-maria highland areas and post-maria craters could be avoided.

Mind the crease: the Riphaeus Section from Sheet 3. Ranger 7 impacted the Moon southwest of the heavily degraded Fra Mauro crater, which is marked by a dashed outline at center right. Please click to enlarge. Image credit: USGS.

Construction, on the other hand, would be a challenge in the Riphaeus Section. Mason expected that, under a thin layer of loose debris, lunar base builders would find basaltic rock hard enough to prevent boring and excavation. Whereas in the Apennines Region he advised lunar base builders to avoid craters and their blocky surroundings, in the Riphaeus Section such asteroid-shattered areas would probably be the only places where digging could occur. This applied to other maria lowlands as well. 

Scientists examining Ranger 7 images found that its impact area was cratered down to the scale of inches; however, the craters were almost all eroded, with smooth floors and rims and few large rocks. Micrometeoroids had been whittling away at the terrain in the Riphaeus Section for a very long time. In tribute to Ranger 7, lunar mappers named the area where it impacted Mare Cognitum, which means "Known Sea."

Surveyor 7, the last of its series of soft landers, alighted gently on the northern flank of Tycho crater on 10 January 1968. Mason and Hackman identified the area containing post-maria Tycho as the pre-maria Macrocrater Province. Tycho, they wrote, spanned 54 miles from rim to rim. The crater's floor was 12,000 feet below its rim, which stood 7900 feet above the surrounding terrain. They noted that Tycho was the Moon's most prominent ray crater, with bright streaks extending up to 500 miles plainly visible to the unaided eye at full moon.

Closeup of Sheet 2: Tycho and the adjoining Macrocrater Province. Please click to enlarge. Image credit: USGS.

Mason judged that landing and movement would be difficult near Tycho. The latter would be possible, however, if a safe travel route could be selected in advance. Construction would be difficult because of the many large blocks embedded throughout the area.

Surveyor 7 landed blind on Tycho's flank; that is, it included no hazard-avoidance system. Through its scanning camera scientists saw that the area was indeed rougher than those that previous Surveyors had explored. They saw loose rocks, boulders, relatively steep slopes, apparent bedrock outcrops, and odd "lakes" of dark gray material, possibly cinders laid down by recent volcanism or rock melted by the colossal energies of the Tycho impact. Some of these features could have destroyed Surveyor 7 had it landed on them.

In general, however, Tycho, like the Riphaeus Section and the Apennines Region, was not as rugged as Mason had predicted. In fact, after Surveyor 7, some felt that Tycho's flank was smooth and level enough for Apollo astronauts to visit. A 1969 study based on Surveyor 7 images determined that it was too rough for rover operations, however.

Tycho's rocky flank: the view from Surveyor 7. Image credit: NASA.

In early December 1960, Mason and Hackman attended the International Astronomical Union's First Lunar Symposium at Pulkovo Observatory in Leningrad. The meeting was held in the Soviet Union in deference to that country's demonstrated lead in lunar exploration. They displayed the U.S. Army Corps of Engineers edition of the "Engineer Special Study."

Upon his return from the historic symposium, Mason presented an informal report on the trip to the January 1961 meeting of the Geological Society of Washington. Mason's boss Whitmore briefly summarized his report in the meeting minutes.

Hackman appeared as co-author on Shoemaker's April 1961 prototype Copernicus geologic map. Copernicus mapping then stalled for several years because Shoemaker had new responsibilities. He had succeeded in launching the NASA-supported Astrogeology Studies Project at USGS Menlo Park, near San Francisco, in August 1960; this became the NASA-supported USGS Branch of Astrogeology in September 1961. In addition, he was busy publishing ground-breaking papers on lunar cratering dynamics and lunar and terrestrial geologic timescales. The Copernicus map was eventually published in 1967 with soon-to-be-astronaut Harrison Schmitt and Newell Trask as Shoemaker's co-authors.

In July 1961, Hackman submitted for review what became after the "Engineer Special Study" the second published USGS lunar map: a geologic study of the Kepler region based on Shoemaker's lunar geologic mapping conventions and five-system lunar stratigraphic column. The Kepler map, published in 1962 under the auspices of the Branch of Astrogeology, was the first NASA-funded USGS lunar map to be published.

Eleven months after the Pulkovo symposium, in November 1961, Whitmore had the sad duty of informing the Geological Society of Washington of Mason's untimely death. The pioneering lunar mapper had taken his own life on 31 October 1961. He was 54 years old.

In his memoir, Wilhelms wrote that Mason committed suicide "for reasons that are not entirely clear and are undoubtedly complex, but which seem to have included non-recognition for his original and ardent pioneering of lunar studies for the U.S. Geological Survey." Pulkovo had marked the high point of Mason's lunar career: after that, Shoemaker's new program increasingly sidelined USGS lunar studies in Washington, DC.

Hackman's involvement in lunar geologic mapping was by then also drawing to a close. His steadfast refusal to leave the Washington area proved to be career limiting. Shoemaker transplanted the Branch of Astrogeology from Menlo Park to the small town of Flagstaff, Arizona, during 1963, and soon the name "Flagstaff" became synonymous with lunar and planetary mapping. Hackman completed one more map for the Branch of Astrogeology — a geologic map of the Moon's Apennines region, which was published in 1966 — but his pioneering contributions to lunar geologic mapping ceased with publication of the Kepler map.

Although the "Engineer Special Study" remained relatively obscure — and became even more so after data from lunar spacecraft rendered much of it obsolete — it did manage to earn a small place in popular culture. Chapter 12 of Arthur C. Clarke's 1968 novel 2001: A Space Odyssey, titled "Journey by Earthlight," begins with a description of the Macrocrater Province and the crater Tycho extracted from Mason's Sheet 4 of the "Engineer Special Study."

References

"Engineer Special Study of the Surface of the Moon," Robert J. Hackman and Arnold C. Mason, Army Map Service, Corps of Engineers, July 1960.

"Engineer Special Study of the Surface of the Moon," Miscellaneous Geologic Investigations Map I-351, Robert J. Hackman and Arnold C. Mason, U.S. Geological Survey, Washington, DC, 1961.

"Memorial to Arnold Caverly Mason (1906-1961)," H. Foster, Geological Society of America Bulletin, Vol. 73, August 1962, pp. 87-90.

To A Rocky Moon: A Geologist's History of Lunar Exploration, Don E. Wilhelms, The University of Arizona Press, 1993, pp. 37-42.

More Information

Around the Moon in 80 Hours (1958)

"Essential Data": A 1963 Pitch to Expand NASA's Robotic Exploration Programs

Apollo Science and Sites: The Sonett Report (1963)

An Apollo Landing Near the Great Ray Crater Tycho (1969)

Log of a Moon Expedition (1969)

Could the Voyages in the Film and Novel "2001: A Space Odyssey" Really Happen? (Part 1)

Log of a Moon Expedition (1969)

Luděk Pešek's lunar expedition was intended to alight in Sinus Medii, a relatively flat region NASA would in fact select as an alternate landing site for early Apollo missions. In his book, Pešek generated drama by landing his eight-man crew off-course in rugged, unstable terrain between Reaumur and Flammarion. Image credit: Defense Mapping Agency/U.S. Geological Survey.

In the 1969-1973 period, the post-Apollo era of robotic planetary reconnaissance was only beginning. The National Geographic Society wanted to give its members a preview, so it turned to Luděk Pešek. Born in Czechoslovakia in 1919, Pešek was out of his home country when Warsaw Pact tanks crushed the 1968 Prague Spring. Rather than return home to tyranny, he took up residence in Switzerland and became a Swiss citizen.

Luděk Pešek's photorealistic paintings of planets and moons dominated the August 1970 and February 1973 issues of National Geographic magazine. The 1970 magazine took in the entire Solar System. It bore on its cover Pešek's painting of Saturn as seen from the moon Titan. The 1973 issue celebrated the discoveries scientists had made using cameras on the Mars probe Mariner 9, the first spacecraft to orbit another planet. The magazine included as a supplement an airbrushed map of Mars based on images from Mariner 9 and Earth-based telescopes. The map's reverse side featured Pešek's impression of the surface of Mars during a dust storm. It was probably the last great artistic rendering of the martian surface before Viking 1, the first successful Mars lander, touched down in Chryse Planitia on 20 July 1976.

Though remembered mainly as an artist, Pešek was also a writer. In 1964, as the real-life Moon Race between the Soviet Union and the United States gathered pace, Pešek penned a short novel about a lunar expedition. It was published first in the Federal Republic of Germany (West Germany) in 1967, then in the United States as Log of a Moon Expedition in 1969, a few months before the Apollo 11 Lunar Module Eagle became the first piloted spacecraft to land on the Moon.

Pešek's account now reads like alternate history. Although billed in the U.S. at the time of its publication as a book for children, it is hard to believe that Log of a Moon Expedition earned much affection from that hard-to-please audience. This might account for the fact that it is not well known today. Pešek's tale reads like a technical paper told through a first-person narrator. Though fiction, its many technical details make it fair game for discussion in this blog.

Pešek described a lunar program that began with several years of hardware development, testing in Earth orbit, and at least four precursor lunar flights. An automated sample-returner collected rocks at the proposed landing site and returned them to Earth for engineering analysis. Meanwhile, at least one automated spacecraft and at least two piloted expeditions (designated KM I and KM II) imaged the Moon's surface from lunar orbit.

Pešek considered the first piloted Moon landing to be the first step in Project Alpha, the intensive exploration of the entire Solar System by astronauts. He did not specify which country or consortium would carry out Project Alpha, nor did he provide a location for "Earth Control," the equivalent of NASA's Mission Control Center in Houston, ESA's European Space Operations Centre in Darmstadt, or the Flight Control Center near Moscow.

Spacecraft KM III. Image credit: Luděk Pešek/Alfred A. Knopf, Jr.

Pešek dispatched his lunar spacecraft, which he dubbed KM III, to Sinus Medii (Central Bay), a patch of relatively smooth, relatively flat mare ("sea") terrain at the center of the Moon's Earth-facing Nearside hemisphere. KM III was streamlined, with tail fins, short wings, a pointed nose, and at least one tail-mounted chemical-propellant rocket engine. It was designed to land upright, with its nose pointed at the black lunar sky, on "stilts" that extended from its tail fins. Each stilt ended in a large rectangular footpad.

Its pressurized cabin housed padded "anti-gravity" (acceleration) couches for eight men, a communications and meteoroid-monitoring radio/radar station, and an impressive array of stores and equipment, including at least 16 180-pound steel-shelled space suits (two for each expedition member). An airlock led from the cabin to the lunar surface.

Before KM III left Earth, three automated cargo landers landed in Sinus Medii. Designated S 1, S 2, and S 3, they set down in a triangular pattern about 15 miles wide. Fat drums about 50 feet tall with silver-and-gray dome-shaped tops, the cargo landers each contained scientific equipment, tools, sturdy electricity-powered tractors with unpressurized cabins for lunar surface transport, construction materials, a pressurized living volume stocked with air, water, and food, and, most important, 40 tons of Earth-return propellant for KM III, which would land on the Moon with nearly dry tanks. Forty tons of propellant were sufficient to launch KM III off the Moon and place it on course for Earth.

Cargo lander S2 with astronaut in open doorway for scale. Image credit: Luděk Pešek/Alfred A. Knopf, Jr.

The expedition was planned to last eight Earth days. KM III was meant to land on level ground at the center of the S 1-S 2-S 3 triangle just after lunar dawn. Pešek wrote that the expedition included enough supplies to remain on the Moon for 14 Earth days (about one lunar daylight period), but that it could not stay past lunar sunset.

This was because the landers and tractors drew electricity from batteries kept charged by dish-shaped solar concentrators. Silver dishes would focus sunlight onto a boiler containing a working fluid that would turn to gas, move through pipes to a turbine generator which would make electricity, pass through radiators to shed heat and return to liquid form, and then return to the boiler to begin the cycle again.

Pešek did not give his intrepid lunar explorers names. Instead, they had three-letter "shortwave radio" designations. CAP was the calm, stoic leader of the expedition, while DOC, the narrator, was the "documenter" and photographer. MEC was the wise-cracking mechanic and navigator, PHY the expedition doctor, and RNT the radio and TV engineer. The expedition included three scientists: GEO, a geologist; AST, an astrophysicist specializing in radiation; and SEL, a selenologist ("Moon scientist").

A lunar expedition crewmember in a Moon suit. The numeral "5" on this suit's backpack identifies its wearer as MEC. Image credit: Luděk Pešek/Alfred A. Knopf, Jr.

Murphy's Law ruled Pešek's lunar expedition. Trouble began even before KM III left Earth. The S 1, S 2, and S 3 landers landed in a triangle as planned, but its center was about 20 miles south of the intended target zone. This placed it uncomfortably close to rocky, rifted terrain between the craters Reaumur and Flammarion. Despite this inexplicable navigational error, Earth Control decided to launch KM III on schedule.

The explorers did not pilot their spacecraft during descent to the Moon. Instead, they strapped into their couches so that they could withstand KM III's rapid deceleration. The spacecraft's guidance system locked automatically onto the cargo lander homing beacons and steered it to a landing.

At touchdown, KM III automatically released a "natrium" (sodium) cloud that fluoresced in lunar dawn light, permitting Earth-based telescopic observers to confirm its location on the lunar surface.

As they waited for the sodium cloud to disperse so that they could see outside, the explorers worried that they had landed off target. Only S 1's homing beacon came in loud and clear. Their radio could not pick up a signal from S 2 and S 3's signal was very weak. In addition, the ground was less stable than anticipated: KM III had an alarming tendency to list to one side. The crew extended the landing stilt on that side to keep their spacecraft level.

When the shadowy landscape around KM III became visible outside the viewports, it was unfamiliar. No elevated surface features should have been visible, yet there was a 190-foot-tall hill a few hundred yards to the north and a taller ridge beyond that. They named the former Revelation Hill. As the gravity of their predicament became clear, they dubbed the latter Disappointment Ridge.

First, however, CAP and DOC donned their cumbersome armored Moon suits and took humankind's first small steps on another world. Pešek wrote that, when they shook hands outside KM III, they felt as though they were "congratulating mankind." They then inspected KM III's landing stilts. All were sunk into the rock deeper than expected. On the side toward which their spacecraft listed, the stilt was extended to half its total length.

Soon after CAP and DOC climbed back inside KM III, Earth Control confirmed that the same navigational error that had affected the cargo landers had caused their spacecraft to land at least 20 miles southwest of its target. This placed KM III entirely outside the triangle formed by the cargo landers. S 3, most northerly of the three, was out of reach at a distance of at least 35 miles.

The expedition got to work. They injected "oxycrete," a specially constituted lunar concrete, under the deeply sunken landing stilt to shore up KM III. Next, they set up a 15-foot-diameter solar concentrator near KM III to charge its batteries. They also erected a 130-foot-tall radio-relay tower atop Revelation Hill to extend their radio range. When they did, they picked up S 2's signal.

The cargo lander was just five miles away and apparently in good condition, but it was beyond Disappointment Ridge, on the far side of a jagged rift up to 65 feet wide and 150 feet deep. The rift, which began close to Reaumur crater, ran for many miles, often through rugged terrain, so could not be circumvented.

The path to S 1, on the other hand, appeared mostly clear, though the lander was about 17 miles away from KM III. A three-man sortie party consisting of DOC, RNT, and AST set out on foot to retrieve S 1's tractor so that the expedition could begin to transfer Earth-return propellant stored in tanks inside the lander to KM III.

Unfortunately, the terrain was not as easily navigated as expected. The sortie party became trapped in a labyrinth of small craters and rifts. After hiking at least 20 miles, they were still more than five miles from S 1. Uncertain that they could reach S 1 in time to refill their Moon suit oxygen tanks, they reluctantly turned back toward KM III.

On the way home, the radio signal from KM III abruptly stopped. The party feared the worst — that the spacecraft had fallen over or suffered some other sudden calamity.

AST's Moon suit oxygen system then malfunctioned, so that he became exhausted and had to be carried. The trio abandoned a large camera and other equipment. Fearing for the lives of his companions, AST begged to be left behind, too.

Fortunately, DOC spotted a signal flare on the horizon. Shortly after that, the sortie party resumed radio contact with KM III. The main radio transmitter had been down for four hours; repair had been slowed by RNT's absence.

Soon after the exhausted sortie party returned to KM III, the expedition abandoned all thought of scientific research so that its members could concentrate on saving themselves. This was discouraging to all the expedition members, not only the three scientists.

Pešek displayed his artistic bent when he described the shadows the glaring Sun cast on the lunar surface as it climbed toward the zenith, then began its slow fall toward the horizon and eventual nightfall at the KM III landing site. He described the effect the lengthening shadows had on the crew's morale as their expedition became a desperate race against time.

To help ensure that the KM III crew could reach at least one cargo lander, Earth Control hurriedly dispatched two backups designated S 4 and S 5. After flights lasting 70 hours, they alighted south of KM III on the same side of the rift and ridges as the piloted lander. This should have made them easy to reach; however, they landed in terrain even more treacherous than that separating KM III from S 1 and S 2.

Meanwhile, Pešek's brave crew climbed and found a pass through Disappointment Ridge, then found places where they could enter the long rift and, after hiking some distance along its rocky, shadowed floor, climb out on its far side using ropes. They marked their way with red metal disks mounted on rods. At last reaching S 2, they activated its living quarters and unloaded tractor TK 2.

They were plagued by Moon suit oxygen regulators that had functioned flawlessly during tests on Earth and in Earth orbit, but which failed inexplicably whenever they passed into cold shadow on the Moon. The curious malfunction was at first life-threatening — it allowed exhaled carbon dioxide to build up in the suits, which probably accounted for AST's difficulties during the unsuccessful hike to S 1 — but through trial-and-error the crew made the oxygen regulator problem a mere persistent annoyance.

AST and CAP suffered injuries that left them unfit for heavy work, and all the men suffered rashes and sores from wearing their Moon suits for far longer than originally planned. As they hiked and labored for long hours, they were obliged to try to sleep in their suits on the lunar surface.

DOC was part of the three-man team that reached S 5 after a grueling hike through 10 miles of boulders and steep hillocks. They barely managed to unload tractor TK 5 before S 5 tilted on unsteady ground and toppled into an "abyss" beneath the lunar surface. Soon after their close brush with catastrophe, DOC called the Moon "a world of death" that could "not be underestimated for a minute."

Nevertheless, retrieval of TK 5 marked a turning point for the Moon explorers. Availability of TK 5 on the same side of the rift as KM III permitted the crew at last to devise a plan for refueling their spacecraft.

They would load 650-pound, six-foot-long propellant tanks from S 2 onto TK 2 by hand and transport them to the rift, then transfer the tanks to buckets hanging from an aerial tramway intended originally for unspecified selenological studies. After the tramway carried the propellant tanks over the rift, they would load them onto TK 5 for the slow, slippery climb over Disappointment Ridge to KM III.

TK 2 and TK 5 could each carry up to 20 propellant tanks at a time, and the tramway buckets could move 20 tanks across the rift in one hour. Twenty tanks had a mass of about 6.5 tons, so about six trips were required to transfer from S 2 the 40 tons of propellants KM III needed for return to Earth.

The challenges did not end - TK 2 became stuck, a rain of meteoroids damaged KM III's solar concentrator, the aerial tramway nearly collapsed into the rift and had to be moved, and KM III began again to list to one side as propellants filled its tanks - yet Pešek's intrepid lunar explorers won through. With the glaring Sun touching the horizon and small features of the landscape casting long shadows, KM III lifted off with just hours to spare.

It is worth noting that, in some respects, Pešek's lunar expedition plan in Log of a Moon Expedition resembles the Lunar Surface Rendezvous (LSR) Apollo mission mode the Jet Propulsion Laboratory (JPL) proposed in 1961-1962. Pešek's plan was, however, on a much larger scale. LSR aimed to accomplish Apollo lunar landings using technology derived from JPL's automated Surveyor soft-lander, which was under development at the time.

A robot lander transfers the last of three solid-propellant rocket motors to the Earth-return crew capsule lander using the extendible bridge truss method. The first lander to reach the site, equipped with a homing beacon and a TV camera, sits in the background at upper right. The cargo lander at lower left has transferred its rocket motor and withdrawn its extendible bridge truss, as has another cargo lander out of view to the right. Image credit: Jet Propulsion Laboratory/NASA.

In the LSR mode, several automated landers would touch down on the Moon tens of feet apart before any humans arrived. The first lander to reach the chosen landing site would carry science instruments, a TV camera, and a homing beacon.

After engineers and scientists used its data to certify the site as safe for further landings, a series of Surveyor-derived cargo landers would arrive. Three or four would each carry as cargo a solid-propellant rocket motor. After the last landed successfully, another lander, this time carrying an unmanned pressurized Earth-return crew capsule, would touch down at the site. The capsule would include seating for up to three astronauts, an Earth-atmosphere reentry heat shield, and parachutes.

Controllers on Earth would guide a small rover as it collected each solid-propellant rocket motor in turn and attached it to the lander bearing the crew capsule. Alternately, they would extend a bridge truss from each cargo lander in turn to transfer the solid-propellant motors. The rover method was considered more likely to succeed.

After JPL's lander/crew capsule combination was ready, an identical crew capsule on a Surveyor-derived lander would depart Earth bearing up to three astronauts. It would slow its descent by firing solid-propellant rocket motors identical to those attached to the lander/crew capsule on the Moon. With help from homing beacons, it would then use chemical-propellant vernier rockets to land near the waiting lander/crew capsule.

Following touchdown, the astronauts would transfer to their ride home and ignite its solid-propellant rocket motors to begin their return to Earth. Nearing Earth, they would cast off the lander and spent rocket motors and position their capsule for reentry.

Sources

Log of a Moon Expedition, Luděk Pešek, Alfred A. Knopf Publishers, 1969.

Man-to-the-Moon and Return Mission Utilizing Lunar-Surface Rendezvous, Technical Memorandum No. 33-53, P. Buwalda, W. Downhower, P. Eckman, E. Pounder, R. Rieder, and F. Sola, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, 3 August 1961.

"Man-on-the-Moon and Return Mission Utilizing Lunar-Surface Rendezvous," J. Small & W. Downhower, Jet Propulsion Laboratory; paper presented at the American Rocket Society Lunar Missions Meeting Held in Cleveland, Ohio, 17-19 July 1962.

Ludek Pesek: Space Artist (http://www.ludekpesek.ch/index.php - accessed 10 April 2018).

More Information

Space Race: The Notorious 1962 Proposal to Launch an Astronaut on a One-Way Trip to the Moon

Plush Bug, Economy Bug, Shoestring Bug (1961)

Around the Moon in 80 Hours (1958)

Mission to the Mantle: Michael Duke's Moonrise (1999-2009)

This NASA image of the gibbous Moon by photographer Lauren Harnett includes an intruder — the International Space Station (ISS) (lower right). The Moon, last visited by humans in December 1972, is about 384,400 kilometers away; ISS, permanently occupied since November 2000, is about 1000 times nearer Earth.

A casual glance at the Moon's disk reveals signs of ancient violence. Nearside, the lunar hemisphere we can see from Earth, is marked by gray areas set against white. Some are noticeably circular. The Apollo expeditions revealed that these relatively smooth basalt plains are scars left by large impactors — comets or asteroids — that pummeled the Moon more than 3.5 billion years ago. These gray areas cover about 20% of the lunar surface. They are concentrated on the nearside, the lunar hemisphere that faces the Earth.

An Earth-based observer cannot view the largest and oldest giant impact basin because it is out of view on the Moon's hidden farside. South Pole-Aitken (SPA) Basin is about 2500 kilometers wide, making it perhaps the largest impact scar in the Solar System. Lunar Orbiter data revealed its existence in the 1960s, though little was known of it until the 1990s, when the U.S. Clementine and Lunar Prospector polar orbiters mapped surface chemistry over the entire Moon. Their data showed that the basin floor probably includes material excavated from the Moon's lower crust and upper mantle. In the first decades of the 21st century, laser altimeters on the U.S. Lunar Reconnaissance Orbiter (LRO) and Japanese Kaguya spacecraft confirmed that SPA includes the lowest places on the Moon.

Lunar hemispheres centered on the Moon's highest point (left) and lowest point (right). Both occur in the Moon's Farside hemisphere and are believed to be associated with the excavation of the South Pole-Aitken Basin perhaps 4 billion years ago. On this U.S. Geologic Survey topographic map, blue indicates low areas and gray and black indicate high areas. 

South Pole-Aitken (SPA) Basin with major features labeled. The 140-kilometer-wide crater Antoniadi includes a 12-kilometer-wide unnamed crater, the floor of which is more than nine kilometers below the mean lunar radius (the lunar equivalent of Earth's sea level). It is the lowest point on the Moon. Image credit: NASA/DSFPortree.

Michael Duke, a retired NASA Johnson Space Center geologist with the Colorado School of Mines, participated in both Apollo and 1990s lunar explorations. In 1999, Duke was Principal Investigator (PI) leading a team that proposed a robotic SPA sample-return mission in NASA's low-cost Discovery Program. To fit under Discovery's mission cost cap of $150 million (in Fiscal Year 1992 dollars), Duke's team proposed "the simplest-possible mission" — a single lander with no sample-collecting rover, a lunar-surface stay-time of just 24 hours, and a low-capability lunar-orbiting radio-relay satellite (needed because farside is not in line-of-sight radio contact with Earth). Believing that these limitations added up to a high risk of mission failure, NASA rejected the 1999 Discovery proposal.

In 2002, however, the National Research Council's planetary science Decadal Survey declared SPA sample return to be a high scientific priority and, at the same time, proposed a new class of competitively selected medium-cost missions. The latter marked the genesis of NASA's New Frontiers Program, which originally had a cost cap per mission of $700 million.

The New Horizons Kuiper Belt Object (KBO) flyby mission was already under development when NASA created the New Frontiers Program. NASA gave New Frontiers a highly visible first mission by adopting New Horizons into the program. Selection of the KBO mission came to be regarded as the first New Frontiers proposal cycle, though it included no competition. NASA had taken a similar approach when it made Mars Pathfinder its first Discovery Program mission in 1992.

Geologist Michael Duke in 2004. Image credit: NASA.

Duke's team immediately began to upgrade its SPA proposal for the second New Frontiers proposal cycle. In October 2002, Duke described the new SPA mission design at the 53rd International Astronautical Federation Congress (the Second World Space Congress) in Houston, Texas. To avoid tipping off competing New Frontiers proposers, his paper provided only limited technical details.

Duke argued that the SPA sample-return mission could collect ancient deep crust and mantle rocks without a costly rover. Clementine and Lunar Prospector had shown that at least half of the surface material in the central part of SPA was native to the basin, so stood a good chance of having originated deep within the Moon.

Furthermore, Apollo demonstrated that any lunar site is likely to yield a wide assortment of samples because the Moon's low gravity and surface vacuum enable asteroid impacts to widely scatter rock fragments. The Apollo 11 mission to Mare Tranquillitatis, for example, found and returned to Earth rocks blasted from the Moon's light-hued Highlands. Duke proposed that the SPA sample-return lander sift about 100 kilograms of lunar dirt to gather a one-kilogram sample consisting of thousands of small rock fragments. These would have many origins, but a large percentage would be likely to have originated in the Moon's deep crust and mantle.

A SPA sample-return lander sifts lunar dust in quest of small fragments of lower crust and upper mantle material. The gray dome mounted sideways on the right side of the lander, above the sample arm attachment point, is the sample-return capsule for carrying a one-kilogram sample through Earth's atmosphere. Image credit: NASA.

NASA rejected the Discovery SPA mission in part out of concern for lander safety. Duke noted that, with the New Frontiers Program's $700-million cost cap, the SPA sample-return mission could include two landers. This would provide a backup in case one crashed. He pointed out, however, that automated Surveyor spacecraft of the 1960s had found the Moon to be a relatively easy place on which to land even without the benefits of 21st-century hazard-avoidance technology. Two landers would also increase the already good chance that the mission could collect samples representative of the basin's earliest history.

A $700-million budget would also enable a relay satellite "more competent" than its bare-bones Discovery predecessor. It might be placed in a halo orbit around the Earth-Moon L2 point, 64,500 kilometers behind the Moon as viewed from Earth. From that position, the satellite would permit continuous radio contact between Earth and the landers. A satellite in lunar orbit could remain in line-of-sight contact with both the landers and Earth for only brief periods.

NASA had argued that a single day on the Moon provided too little time to modify the SPA Discovery mission if it suffered difficulties. The SPA New Frontiers mission would, therefore, remain on the Moon for longer. Duke noted, however, that stay-time would probably be limited to the length of the lunar daylight period (14 Earth days) because designing the twin landers to withstand the frigid lunar night would boost their cost.

In February 2004, Duke's mission — christened Moonrise — became one of two SPA sample-return missions proposed in the second New Frontiers proposal cycle. In July 2004, NASA awarded Moonrise and a Jupiter polar orbiter called Juno $1.2 million each for additional study. In May 2005, the space agency selected Juno for full development.

Juno's selection did not end proposals for SPA Basin sample-return, though it did mark the beginning of the end of Duke's involvement. In the third New Frontiers proposal cycle, which began in 2009, a Jet Propulsion Laboratory/Lockheed Martin/Washington University in St. Louis team led by Brad Jolliff, Duke's deputy PI in the 2003-2004 cycle, proposed a SPA Basin mission called MoonRise. In 2011, the SPA sample-return mission was again selected as a New Frontiers finalist, but it lost out in the final selection to the OSIRIS-Rex asteroid sample-return mission. MoonRise was not selected as a finalist in the 2017 New Frontiers cycle.

Sources

"Sample Return from the Lunar South Pole-Aitken Basin," M. Duke, Advances in Space Research, Volume 31, Number 11, June 2003, pp. 2347-2352.

"NASA Selects Two 'New Frontiers' Mission Concepts for Further Study," D. Savage, NASA Press Release 04-222, NASA Headquarters, 16 July 2004.

NASA Facts: MoonRise - A Sample-Return Mission From the Moon's South Pole-Aitken Basin, NASA Facts, JPL 400-1408, June 2010.

"MoonRise: Sample Return from the South Pole-Aitken Basin," L. Akalai, B. Jolliff, and D. Papanastassiou; presentation to the International Planetary Probe Workshop, Barcelona, Spain, 17 June 2010.

Personal communication, B. Jolliff to D. Portree, 3 March 2018.

More Information

Peeling Away the Layers of Mars (1966)

An Apollo Landing Near the Great Ray Crater Tycho (1969)

Catching Some Comet Dust: Giotto II (1985)

Lunar GAS (1987)

Robot Rendezvous at Hadley Rille (1968)

Unmanned Lunar Roving Vehicle (ULRV). Image credit: Bendix/NASA.

In May 1968, Bellcomm planners Noel Hinners, Farouk El-Baz, and A. Goetz described a unique post-Apollo mission to the Apennine Front-Hadley Rille region of the Moon. Had it flown, the mission would have seen a melding of manned and automated lunar exploration, potentially yielding results greater than either astronauts or exploring machines could achieve on their own.

Hinners, El-Baz, and Goetz invoked an Extended Lunar Module (ELM) capable of bearing 750 pounds of payload to the Moon's surface. During the crew's first venture outside the ELM, they would rendezvous with a waiting Unmanned Lunar Roving Vehicle (ULRV).

The wheeled ULRV, with a mass of between 1,500 and 3,000 pounds, would have landed some 500 kilometers from the Apennine Front-Hadley Rille ELM site some time earlier. Under guidance from controllers on Earth, it would then have made its way to meet the astronauts, all the while beaming TV images of its surroundings to Earth, charting the Moon's gravity and magnetic fields, leaving behind Remote Geophysical Monitor instrument packages, and collecting rock samples. The ELM astronauts would retrieve the ULRV rock samples for return to Earth.

Numbers are explained in the text. Image credit: Aeronautical Chart and Information Center.

The Bellcomm planners proposed four candidate traverse routes for the ULRV (map above). For route 1, the automated rover would land in the Sulpicius Gallus region of southwest Mare Serenitatis and strike north through an area of north/south-trending rilles (canyons) and dark, thus possibly volcanic and young, surface material. The lunar Apennine Mountains would dominate the western horizon as the ULRV rolled northward, gradually entering a region with lighter and older surface materials.

At the contact between Mare Serenitatis and Mare Imbrium, the rover would turn west, then south, so the Apennines would dominate its eastern horizon. The ULRV would pass through hills made up of rocks of the Fra Mauro Formation, which was widely interpreted as ejecta from the immense ancient impact that excavated Mare Imbrium.

Finally, the route 1 rover would carefully pick its way across steep-sided Hadley Rille (also known as Rima Hadley) and park close to the planned post-Apollo ELM landing site south of the crater Hadley C. The Bellcomm researchers declared 10-kilometer-wide Hadley C to be a "probable maar" — that is, a surface feature produced when rising magma comes into contact with subsurface ice or water, generating a steam explosion.

Route 2 would see the ULRV land south of the crater Alexander in northern Mare Serenitatis. The rover would strike southwest toward the Mare Serenitatis-Mare Imbrium contact through a region of hummocky Highland rock units, including probable examples of the Fra Mauro Formation. The route would cross dark materials (possible young volcanics) and light materials (possible rays from young impact craters) before it turned south to follow the same path to the ELM site as the Route 1 ULRV.

The ULRV for traverse route 3 would land in southern Mare Imbrium west of the "ghost" crater Wallace, an ancient impact crater mostly submerged by flowing lava in the distant past. The rover would trundle eastward across a bright ray from the young large crater Copernicus, than pass through a crater chain to reach Wallace's subdued, ancient rim. Once there, it would strike out northeastward across eastern Mare Imbrium, then over the Apennine Bench (a possible volcanic ash or flow deposit), before crossing Palus Putredinis to Hadley C and the planned ELM landing site.

Route 4 would begin at a ULRV landing site in central Mare Imbrium, in an area with many fresh-looking wrinkle ridges. The ULRV would surmount one such ridge on its way to the north rim of the large smooth-floored crater Archimedes. After cautiously picking its way through the boulders and crevasses near the crater's rim, the ULRV would turn southwest through a region of exposed bedrock, then would cross hummocky Fra Mauro Formation hills and Palus Putredinis before parking near the ELM site.

The Bellcomm planners identified routes 1 and 2 as having the greatest potential for increasing geophysical understanding of the Moon. In addition, route 1 would pass through terrain similar to that observed at Littrow, another candidate post-Apollo landing site, possibly freeing the proposed Littrow ELM mission to explore elsewhere on the Moon. The Littrow site was located on the eastern side of Mare Serenitatis.

Hadley C landing site and traverses. Numbers and colors are explained in the text. Image credit: Defense Mapping Agency Topographic Center/NASA/DSFPortree.

Hinners, El-Baz, and Goetz noted that, in addition to collecting a diverse suite of samples along its 500-kilometer traverse path, the ULRV might be used to survey the ELM landing site, which would be located on the Hadley Rille rim at 26° 52′ North, 3° 00′ East (marked by the red star on the Hadley C landing site map above). The ULRV survey might eliminate the need for high-resolution orbital photography of the area. The rover might also act as a landing beacon for the ELM and serve as a radio relay for the astronauts exploring the site, which would include many places where they might pass behind hills and into trenches, out of line-of-sight radio contact with the antennas on the ELM.

Hinners, El-Baz, and Goetz noted other operational challenges of the Apennine Front-Hadley Rille ELM site. The most important involved lighting. The ELM would approach the site from the east with the Sun behind it, pass over the Apennine Mountains, then descend almost vertically on the west side of the range. As it descended, it would plunge suddenly into shadow cast by the mountains. On some landing dates, the astronauts might touch down in darkness lit only by sunlight reflected off the Hadley C rim and other features beyond the shadow; on other dates, they would emerge from shadow into dazzling sunlight just before touchdown.

The scientists were convinced, however, that the scientific benefits of their ELM site would outweigh these operational difficulties. They wrote that

This site is important among those proposed in that it may provide access to a major portion of lunar history. . .Such access comes from over 1 km of vertical relief resulting from the combination of the Apennines Mountains scarp, the rim of the Imbrium Basin[,] and the rille. . .This historical sequence may run from materials that constitute original lunar crust to relatively young materials derived from that crust. The oldest crustal materials in the area, possibly exposed in the lower part of the Apennine Front to the east of the proposed landing area, should provide data bearing directly on the problems of the primary physical and chemical composition of the Moon and thus, indirectly, of the Earth.

The scientists noted that the Manned Spacecraft Center in Houston, Texas, had established as a ground rule that only a single Extravehicular Activity (EVA) could take place on the first and last days of a lunar landing mission. The first three-hour EVA (1 and purple on Hadley C site map) of the Apennine Front-Hadley Rille mission, on landing day, would see the astronauts walk to the parked ULRV to retrieve the samples it had gathered during its traverse. They would also work together to assemble and point at Earth the umbrella-like S-band antenna, inspect the ELM's exterior for any damage incurred during descent and landing, deploy "staytime extension equipment" (for example, a small solar array for generating supplemental electricity), and unstow the mission's twin 180-pound Lunar Flying Units (LFUs).

Lunar Flying Unit concept art. Image credit: North American Aviation/NASA.

NASA and its contractors had studied the LFU, a small, rocket-powered hopper, for several years by the time Hinners, El-Baz, and Goetz made it a critical part of their Apennine Front-Hadley Rille mission (see "More Information" below). If all went as planned, the ELM would land with close to 1,000 pounds of propellants remaining in its descent stage tanks.

At the start of the first EVA of day 2 (2 and green on Hadley C site map), the astronauts would spend 30 minutes pumping into each LFU 300 pounds of propellants from the ELM. They would also load LFU #1 with cameras and film, geologic tools including a 25-pound hand drill for collecting sample cores, and sample containers.

Astronaut #1 would then fly LFU #1 3.3 kilometers to his first stop, the Apennine Front-mare contact, where he would spend one hour collecting up to 25 pounds of samples, including cores drilled to a depth of 10 feet. He would then fly two kilometers to the top of the Apennine ridge, about 500 meters above the ELM. He would spend an hour there collecting another 25 pounds of samples.

The Bellcomm planners explained that materials blasted from "depths of several tens of kilometers in the Moon" by the Imbrium impact might be draped over the sites he visited. These would, they argued, "offer our best chances to examine 'primitive' planetary materials which have not been affected by later planetary differentiation processes."

Astronaut #2, meanwhile, would deploy the 280-pound Apollo Lunar Scientific Experiment Package (ALSEP) near the ELM. He would stand by LFU #2 to rescue Astronaut #1 in the event that LFU #1 failed on top of the ridge, which would lie just beyond the five-kilometer “walk-back limit” of the Apollo space suits. Assuming, however, that LFU #1 gave no trouble, Astronaut #1 would fly 5.2 kilometers back to the landing site and join Astronaut #2 inside the ELM for lunch and rest.

To begin the second EVA of mission day 2 (2 and blue on the Hadley C site map), Astronaut #1 would board LFU #2 and fly 3.2 kilometers west of the ELM to the bottom of Hadley Rille. Astronaut #2, meanwhile, would walk to a point on the Rille rim within sight of both Astronaut #1 and the ELM. He would collect up to 25 pounds of samples and serve as a radio relay linking Astronaut #1 to the ELM and, through the ELM, to Earth.

After 1.5 hours of sampling the shadowed floor of Hadley Rille, Astronaut #1 would fly LFU #2 4.8 kilometers to the Hadley C rim. He would spend 30 minutes sampling, then would fly back to the ELM. At no point would Astronaut #1 pass beyond the Apollo suit walk-back limit, so Astronaut #2 would have no need to stand by LFU #1 to mount a rescue.

The fourth and final EVA of the Apennine Front-Hadley Rille mission (4 and yellow on the Hadley C site map) would occur on departure day. After loading LFU #1 with propellants, Astronaut #1 would fly 2.5 kilometers west of the ELM to two sets of crater pairs. After 30 minutes of sample collection, he would fly 1.5 kilometers to a crater on the Hadley Rille rim, where he would again sample for 30 minutes. Finally, he would fly three kilometers to a “promontory” on the Rille rim, sample for 30 minutes, and fly 1.4 kilometers back to the ELM.

Astronaut #2, meanwhile, would "conduct local investigations" close by the ELM, "adjust ALSEP experiments," and prepare samples for return to Earth. After returning to the ELM, Astronaut #1 would assist Astronaut #2. After packing up about 100 pounds of samples, they would lift off in the ELM ascent stage, leaving behind the LFUs and other equipment.

They would also leave behind many of the samples they had collected. Hinners, El-Baz, and Goetz noted that, while the ULRV would collect some unspecified (but probably large) quantity of unique samples during its 500-kilometer traverse and the astronauts might collect about 200 pounds of samples, the ELM ascent stage could carry only 100 pounds of payload into lunar orbit. This meant that the sample packing process would mostly involve hurried screening, with the majority of the samples collected during the mission being thrown away. They also noted that their EVA schedule was very tight, so that mission success would depend "on everything going with clockwork precision during the crowded EVA periods."

To solve these problems, they proposed that the ELM for the Apennine Front-Hadley Rille mission be upgraded to permit a 1,000-pound science payload, a four-day surface stay, and 200 pounds of returned samples. This would, among other things, enable addition of a walking traverse to the Apennine Front-mare contact and introduction of a 400-pound Advanced ALSEP. Additional stay-time would permit more care to be taken in selecting samples for return to Earth; at the same time, doubling the returned sample weight would make sample screening less critical.

Apollo 15 Lunar Roving Vehicle. Image credit: NASA.

Apollo 15, the first of three advanced J-mission Apollos NASA flew in 1971-1972, landed at 26° 8′ North, 3° 38′ East, about 30 kilometers northeast of the Hinners, El-Baz, and Goetz ELM landing site, on 30 July 1971. The site, close to where Hadley Rille turns sharply toward the northwest, is farther from the mountains than the Hadley C site, eliminating lighting problems. The LM Falcon remained on the surface for nearly three days. Astronauts David Scott and James Irwin had at their disposal no LFU; the concept, though much studied, had gained little traction, in large part because of Astronaut Office opposition.

In place of the LFU, Scott and Irwin traversed their landing site using a 460-pound four-wheeled Lunar Roving Vehicle (LRV). They drove almost 28 kilometers during three periods of space-suited surface activity, the longest of which lasted seven hours and 13 minutes. Falcon's ascent stage lifted off from Hadley-Apennine on August 2 with a cargo of about 170 pounds of lunar samples.

Apollo 15 was the fourth of six successful manned lunar landings. By the time it flew, budget cuts and policy changes had caused NASA to truncate Apollo and abandon plans for post-Apollo lunar exploration. In an editorial published the day after Falcon's ascent stage left the Moon, The New York Times pointed to the mission's many achievements and reminded its readers that manned lunar exploration was set to end with Apollo 17. A "vast and complex technology developed at a cost of billions of dollars over the last decade is being abandoned even as its vast potentialities are being demonstrated," the paper lamented.

Sources

A Preliminary ELM/Unmanned LRV Mission Plan for the Apennine Front-Hadley Rille Area – Case 340, N. Hinners, F. El-Baz, and A. Goetz, Bellcomm, Inc., 31 May 1968.

Astronautics & Aeronautics 1971, NASA SP-4016, NASA, pp. 217-218.

More Information

"A Continuing Aspect of Human Endeavor": Bellcomm's January 1968 Lunar Exploration Program

Rocket Belts and Rocket Chairs: Lunar Flying Units

Apollo's End: NASA Cancels Apollo 15 & Apollo 19 to Save Station/Shuttle (1970)

The Spacewalks That Never Were: Gemini Extravehicular Planning Working Group (1965)

An Apollo Landing Near the Great Ray Crater Tycho (1969)

Splat! Tycho crater (lower center) is the the most prominent bright surface feature in this NASA image of the full Moon. Linear rays originating at the crater can be traced outward for hundreds of kilometers.

Of the seven automated Surveyor spacecraft NASA launched to the Moon between May 1966 and January 1968, only the last, Surveyor 7, aimed for a target selected specifically for its scientific value. Surveyors 2 and 4 failed, while Surveyors 1, 3, 5, and 6 soft-landed at flat mare (basalt plain) sites in the "Apollo Zone," the near-equatorial band readily accessible to piloted Apollo Lunar Module (LM) spacecraft. The successful Apollo Zone Surveyors performed valuable scientific investigations, but their main purpose was to image their landing sites and test surface bearing strength to help assure mission planners that the lunar terrain was smooth and stable enough to permit Apollo astronauts to land safely.

Surveyor 7, by contrast, aimed for the rugged northern flank of Tycho crater, one of the most prominent features on the Moon's Earth-facing nearside hemisphere. The 85-kilometer-wide asteroid impact scar, centered at 43° south latitude in heavily cratered highlands terrain, is surrounded by an extensive system of bright rays best viewed when the Moon is full. The rays are made up of ejecta blasted out when Tycho formed about 110 million years ago. As ejecta fell back onto the Moon, it stirred up more material, generating a ray cascade extending up to 1500 kilometers from Tycho.

Surveyor 3 (above) served as a pinpoint landing target for Apollo 12 astronauts Charles Conrad and Alan Bean in November 1969. During their second moonwalk, they stopped by the derelict lander to collect parts and take pictures for engineering analysis. Surveyor 7 resembled Surveyor 3, but included noticeable differences; most obvious was the addition of the deployable alpha-scattering instrument. Image Credit: NASA.

Hand-laid mosaic of images from Surveyor 7 illustrating the rocky, rolling nature of the terrain north of Tycho. Image credit: NASA/USGS.

Surveyor 7 lifted off from Cape Kennedy atop an Atlas-Centaur rocket on 7 January 1968. It landed on 10 January at 40.9° south latitude, 11.4° west longitude, just 2.5 kilometers from its intended target and 30 kilometers from Tycho's rim, on the ejecta blanket surrounding the crater.

Less than an hour after touchdown, the three-legged, solar-powered lander returned the first of more than 21,000 images it would beam to Earth. Some of these were stereo pairs, enabling scientists to precisely locate the many varied rocks and boulders visible in the field of view of Surveyor 7's scanning camera. Other images were assembled into panoramic mosaics that show lunar landscape features up to 13 kilometers away from the lander.

Among the features most intriguing to lunar scientists were so-called "lakes" of relatively dark material. They lay in depressions and had relatively flat surfaces. Curving, branching trenches etched many of these small dark plains. Some scientists interpreted the lakes as signs of recent volcanic activity, the "holy grail" of 1960s lunar exploration.

Tycho, its ejecta blanket, and the Surveyor 7 landing site as imaged by NASA's Lunar Reconnaissance Orbiter (LRO). The spacecraft entered lunar polar orbit in June 2009. The ejecta surrounding the crater partly covers and "blurs" lunar surface features that existed before Tycho was formed. Image credit: NASA.

In keeping with its science-focused mission, Surveyor 7 carried more scientific apparatus than any of its predecessors. Besides its camera, the lander carried an alpha-scattering device for determining the composition of rocks and dirt and an arm-mounted digger. The former had flown previously on Surveyor 5 and Surveyor 6; the latter on Surveyor 3.

At first, the alpha-scattering device failed to deploy, but flight controllers were able to direct the digger to push it down into contact with the lunar surface. They later used the arm/digger to position the alpha-scatterer on a rock and in a trench the digger had excavated. They found that the surface material at Surveyor 7's highlands landing site contained more aluminum than did that at the mare sites the other Surveyors explored.

Controllers were unable to place the alpha-scatterer in contact with boulders on a low ridge near Surveyor 7, some of which might have been blasted from kilometers below the lunar surface by the Tycho impact. They were far beyond the digger's 1.52-meter maximum reach. Nor were controllers able to move the instrument to the dark material of the lakes, the nearest of which lay about a kilometer from the lander. When the Surveyor 7 mission ended on 21 February 1968, much was known about its complex landing site, but much else remained mysterious.

Lunar Orbiter image of the Surveyor 7 landing area. The two dotted lines originating at the Surveyor 7 ("S.VII") touchdown point indicate the limits of the field of view of the lander's scanning camera. North is toward the top. Prominent in the right half of the image is a dark lake-like feature, the "shore" of which is located about a kilometer away from Surveyor 7. Image credit: NASA.

The lakes and the tantalizing variety of rocks near Surveyor 7 caused some lunar scientists to call for an Apollo mission to the site. It was far outside the Apollo Zone, but could be reached during certain times of year if conservative Apollo mission rules were relaxed.

In August 1969, less than a month after Apollo 11, the first piloted Moon landing mission, U.S. Geological Survey (USGS) scientists worked with Bellcomm, NASA's Apollo planning contractor, to rough out the surface portion of an Apollo Tycho mission. It would begin with a pinpoint LM landing a kilometer southeast of Surveyor 7.

The pinpoint landing would be required if the astronauts were to follow the geologic traverse routes the Bellcomm/USGS team planned. The LM descent stage would carry enough propellants to enable the Tycho mission crew to at least partly compensate if their LM missed its designated touchdown point. This was deemed an especially important capability because the Apollo 11 LM Eagle had landed off course at the edge of its landing ellipse.

On the basis of Surveyor 7 and Lunar Orbiter V images, the Bellcomm/USGS team judged that the Tycho site was too rocky for a jeep-like lunar rover to navigate. They suggested that the astronauts explore on foot within an operational radius of about 2.5 kilometers centered on their LM.

Proposed new "constant volume" hard suits tougher and more flexible than the mostly fabric Apollo suits would, they anticipated, make possible speedy hikes over rugged terrain. The new suits would also permit the astronauts to operate on the surface for up to seven hours at a stretch. They would spend 54 hours at the Tycho landing site, providing enough time for three seven-hour traverses.

LRO image of the Surveyor 7 landing area. Please refer to the previous image for a scale bar. The arrow points to the derelict lander, which is just visible because of the shadow it casts on the surface. Technology advancement means that the image is sharper than the previous Lunar Orbiter image: individual boulders about the size of the lander are clearly seen, as are details of the lake-like melt "pond" and small impact craters. Image credit: NASA.

The Bellcomm/USGS team planned that, during Traverse I, one astronaut would deploy an Apollo Lunar Scientific Experiment Package (ALSEP) about 1.1 kilometers east of the LM. The ALSEP would include a passive seismometer. In addition to establishing a "far southern" station in the Apollo seismic network, the instrument would exploit natural moonquakes and asteroid impacts to chart Tycho's subsurface structure. The ALSEP might also include a heat-flow experiment to help scientists determine whether volcanism had occurred recently at the site, a laser retroreflector, a magnetometer, and a gravimeter.

The other astronaut, meanwhile, would walk along the low ridge visible from Surveyor 7 and sample the boulders there. The two moonwalkers would then meet up and return to the vicinity of the LM. Traverse I would total about 3.5 kilometers.

During Traverse II, at about 6.25 kilometers the longest of the Tycho mission moonwalks, the astronauts would strike north together to the "shore" of a prominent kilometer-wide dark lake. They would photograph and sample the branching trenches, then walk to a point 2.6 kilometers from their LM to sample "dark flow dome material." On the way back to the LM, they would visit Surveyor 7 to collect samples of lunar materials it had examined and salvage parts of the robot lander for engineering analysis.

The final traverse of the Apollo Tycho mission would see the astronauts walk south about 1.3 kilometers to sample another dark lake, then travel a further 1.4 kilometers to sample subsurface material exposed by a small fresh impact crater. They would then hike half a kilometer to a raised "flow levee" surrounded by "late smooth flow materials." Traverse III would total 5.25 kilometers. In all, the astronauts would walk 15 kilometers and collect between 100 and 200 pounds of samples during their three moonwalks.

The Bellcomm/USGS team acknowledged that the Tycho site presented challenges beyond its position outside the Apollo Zone. It was rugged and undulating, so the astronauts were likely to lose line-of-sight contact with the radio antennas on their LM as they walked. The LM would relay signals from their space suit radios, so they might temporarily lose radio contact with Earth. In addition, the site had not been imaged from orbit at the same high resolution as other candidate Apollo sites.

The team suggested that, if no high-resolution orbital images of the site could be obtained and if this continued to be considered a major drawback, then the Apollo Tycho mission could land closer to Surveyor 7. Though doing so would enable a landing in a well-characterized area, it would create its own problems. The most serious of these would be to place much of the Traverse III loop beyond the planned 2.5-kilometer operational radius of the mission's moonwalks.

This map of the landing sites of all the successful Surveyors shows how far south Surveyor VII landed. No other spacecraft has soft-landed so far from the lunar equator. Image credit: NASA.

During 1970, in the aftermath of the near-disastrous Apollo 13 mission, NASA engineers, mission planners, managers, and astronauts, never enthusiastic about the Tycho site proposal, rejected the region as too rugged for a safe Apollo landing. Some scientists were, however, not easily deterred: they continued to sing the site's praises as late as 1972.

They pointed to the fact that Surveyor 7 had successfully landed without the precise terminal guidance an astronaut would provide. They hoped that Apollo 16 or 17 might be diverted to Tycho. In the end, however, no Apollo mission visited Surveyor 7, leaving to it the honor of the highest-latitude/farthest-south landing site of any spacecraft that has soft-landed on the Moon.

The dark lake-like features observed near Tycho are known today to be patches of melt material that flowed and was thrown outward from Tycho during its explosive formation, not signs of recent volcanic activity. Impact melt flows are found inside and around many large young impact craters. Melt flow features are rare close to older craters because the steady rain of micrometeoroids and small asteroids that strikes the Moon splinters them into dust and boulders and gradually renders them indistinct.

Sources

Surveyor VII: A Preliminary Report, NASA SP-173, NASA Surveyor Program Office, May 1968.

Surveyor Program Results, NASA SP-184, Surveyor Program, NASA, 1969.

"Tycho - north rim," H. Masursky, G. Swann, D. Elston, and J. Slaybaugh, 14 August 1969 (revised 15 August 1969).

Memorandum, J. Slaybaugh to J. Llewellyn, "Tycho Rim Engineering Evaluation - Case 320," Bellcomm, Inc., 28 August 1969.

To A Rocky Moon: A Geologists' History of Lunar Exploration, Don E. Wilhelms, The University of Arizona Press, 1993, pp. 242, 287, 312.

More Information

"Essential Data": A 1963 Pitch to Expand NASA's Robotic Exploration Programs

If an Apollo Lunar Module Crashed on the Moon, Could NASA Investigate the Cause? (1967)

"A Continuing Aspect of Human Endeavor": Bellcomm's January 1968 Lunar Exploration Program