Mission to a mare ridge (1968)

The January 27, 1967 Apollo 1 fire undermined confidence in NASA's ability to put a man on the moon by 1970. The unmanned Apollo 4 (November 11, 1967) and Apollo 5 (January 22, 1968) missions, respectively the successful first test of the Saturn V rocket and the successful first test of the Lunar Module (LM), did much to restore faith in the U.S. civilian space agency. Two weeks after the fire's solemn first aniversary, M. T. Yates, an engineer with Bellcomm, NASA's Apollo planning contractor, completed a memorandum which demonstrated that renewed confidence. In it, he proposed a surface exploration plan for the third Apollo moon landing mission.

In keeping with the nomenclature established in Bellcomm's January 1968 Lunar Exploration Program Plan, Yates designated the mission Lunar Landing Mission-3 (LLM-3). An "early Apollo" mission, LLM-3 would include a 35-hour stay on the moon, three three-hour moonwalks by two astronauts, and surface exploration on foot no farther than one kilometer from the LM. Critical for detailed moonwalk planning would be the LLM-3 LM's ability to set down within a 200-meter-diameter circle centered on a pre-selected landing point. LLM-1 and LLM-2 would be counted as successful if they managed to touch down anywhere within an ellipse with a total area of 235 square kilometers; LLM-3's landing area would total just 0.25 square kilometers.

Yates selected as his LLM-3 landing site an area photographed by the Lunar Orbiter III spacecraft between February and October 1967. Located at 36° west, 3° south, it lay in Oceanus Procellarum directly south of the prominent ray crater Kepler. Specifically, he targeted the LLM-3 LM to a half-kilometer-wide mare ridge with a fresh, 200-meter-wide crater on top. Mare ridges are common features on the dark-hued lunar plains known individually as mare; some mare ridges are faults, where the mare crust has shifted, cracked, and rumpled, while others might indicate lava movement just beneath the surface in the past (image above). Yates expected that the crater would act as a natural drill hole, enabling the astronauts to sample material from inside the ridge.

The first moonwalk of the LLM-3 mission would see the two astronauts, designated A and B, working together to set up the Apollo Lunar Scientific Experiment Package north of their LM. The LLM-3 ALSEP would include a drill for collecting a subsurface core sample and heat flow probes for installation in the core holes. The astronauts would then move south past the LM to the rim of the crater. During the second moonwalk, astronaut B would descend into the crater while astronaut A monitored his activities from its rim. In addition to keeping an eye on his colleague, A would relay communications from B to the LM for transmission to Earth. This would be necessary, Yates wrote, because the crater rim would block B's radio signals.

In the third and final LLM-3 moonwalk, astronaut B would move westward down a short canyon to the mare floor, then would walk south along the ridge-mare contact. Astronaut A, meanwhile, would walk along the mare ridge crest to keep B in sight and again relay his radio signals to the LM. The astronauts would then meet up and return to the LM via the east rim of the crater.

No Apollo mission explored a mare ridge, and Yates's proposed radio relay technique was never used. The second Apollo lunar landing mission, Apollo 12, amply demonstrated the pinpoint landing capability Yates rightly deemed crucial by setting down near the derelict Surveyor III lander in November 1969. Apollo 14, the third successful Apollo lunar landing mission, used this capability to land near Cone Crater, a naturally occurring drill hole that permitted Al Shepard and Ed Mitchell to sample deep within the Fra Mauro Formation in February 1971.

A Lunar Landing Mission to a Mare Ridge - Case 340, M. T. Yates, Bellcomm, February 14, 1968.

Schedule constraints on manned Mars missions (1966)

In March 1966, at the height of 1960s optimism about America's future in space, Robert Riedesel and John Wall, respectively Project Manager and Chief Engineer of the Future Systems Department at Douglas Aircraft Company, presented a paper in which they discussed the constraints which they believed made a piloted Mars mission unlikely before 1981. Though the specifics have changed, in general the constraints they listed 43 years ago are the same ones faced by planners of costly space missions today.

Their first group of constraints, those related to natural phenomena in the Solar System, included the cycle of minimum-energy Mars launch opportunities and the 11-year solar activity cycle. Minimum-energy Mars launch opportunities occur every 26 months, the Douglas engineers noted. The less energy needed to reach Mars, the less propellant would be required. The less propellant required, the fewer costly heavy-lift rockets would be needed to launch Mars spacecraft hardware and propellant into Earth orbit for assembly.

Riedesel and Wall noted that not all minimum-energy opportunities are created equal; the amount of energy required to reach Mars follows a roughly 15-year cycle. Unfavorable opportunities would occur in 1977 and 1979, they wrote, then opportunities would improve in 1981 and 1984. The year 1986 would see the most favorable Mars launch opportunity since 1971.

The 11-year solar cycle would reach maximum intensity in 1981, then would decline to a minimum in 1986-1987. The potential for "giant" solar flares during solar maximum meant that astronauts traveling to Mars in 1981 would need a massive radiation shelter. Riedesel and Wall recommended that NASA launch its first Mars expedition in 1986, when the solar minimum and a highly favorable Earth-Mars transfer opportunity would coincide.

Some schedule constraints were based on needed experience. Before engineers could develop a piloted Mars spacecraft, they would need more data on the martian environment and the effects on humans of long exposure to weightlessness. Riedesel and Wall expected that the planned Voyager automated Mars probe and astronaut stays on board an Earth-orbiting space station would provide the necessary data as early as 1973. They cited Apollo development experience when they estimated that Mars spacecraft development would require at least seven years after the needed data became available. This would mean that the first Mars expedition could set out no earlier than the 1981 launch opportunity.

Economics would also constrain the piloted Mars mission schedule. Riedesel and Wall cited published Mars program cost estimates ranging from $40 billion to $100 billion. Their own cost estimate - $62 billion - included the cost of automated precursor probes, an Earth-orbiting space station, a heavy-lift rocket more powerful than the Saturn V, and eight piloted missions leading to one piloted Mars landing. They assumed that NASA's budget would remain at its Apollo peak of about $5 billion per year, with $3 billion going to piloted spaceflight. They concluded that, if astronauts were to reach Mars in the 1980s, then either a "major increase" in the space agency's budget or "a less expensive approach to interplanetary exploration" would be necessary.

Finally, piloted Mars exploration faced political constraints. Riedesel and Wall predicted that, if President Lyndon B. Johnson were re-elected in 1968, then he would have little incentive to commit funds and political capital to a piloted Mars program that would not succeed until long after he left office. The Mars program might start when Johnson's successor took office in January 1973. The new president might, however, find no personal benefit in championing a Mars expedition, for even if he initiated it immediately after he took office, it would leave Earth for Mars no earlier than the 1981 launch opportunity, after his second term had ended in January 1981.

If, on the other hand, President Johnson were not re-elected in 1968, then his successor could initiate the automated Mars probe and space station programs in 1969 with a good chance of seeing them succeed before his second term ended. Commitment to a piloted Mars expedition would probably have to wait until another president took office in early 1977, however. Given the time required for hardware development, this would postpone launch of the first U.S. piloted Mars expedition until at least 1984.

"Scheduling Constraints on Manned Exploration of Mars," Robert Riedesel and John Wall, A Volume of Technical Papers Presented at the AIAA/AAS Stepping Stones to Mars Meeting, pp. 99-106; paper presented in Baltimore, Maryland, March 28-30, 1966.

NASA's future on the eve of the fire (1966)

The Lunar Exploration Working Group (LEWG) was one of five groups NASA established in February 1966 "to examine the objectives and systems associated with a number of mission areas and document these findings in the form of a set of candidate program options covering the next 15 to 20 years." The LEWG and its companions (Earth Applications, Biosciences, Astronomy, and Planetary Exploration) were part of the on-going debate over NASA's post-Apollo future, which had begun almost as soon as President John F. Kennedy assigned the agency the goal of an American on the moon by the end of the 1960s (May 25, 1961).

Resolving the debate became increasingly important as Apollo's culmination approached. As the LEWG completed its November 1, 1966 report for NASA, the Apollo 1 crew of Virgil Grissom, Ed White, and Roger Chaffee (bottom image above, left to right) continued their training at Kennedy Space Center in preparation for launch into Earth orbit. Apollo 1, the first piloted test of the three-man Command and Service Module (CSM) spacecraft, was expected in late December 1966, about two months after the LEWG completed its report, and the first lunar landing attempt was expected to follow about a year after that.

Faced with a ballooning Federal budget deficit - largely the result of escalating U.S. military involvement in Indochina - President Lyndon Johnson's Bureau of the Budget projected little funding for post-Apollo lunar hardware before Fiscal Year 1973. Acknowledging this, the LEWG stated that its report represented "neither policy nor firm intent." It quickly added, however, that the document showed "the firm belief. . .that an effective lunar exploration plan can result from careful matching of scientific objectives with capabilities of unmanned systems and Apollo derivatives within a reasonable budget." The LEWG described a four-phase program spanning 1968-1980, which it said would be "structured to permit uninterrupted exploration of the Moon in the post-Apollo period. . .consistent with sound scientific rationale and fiscal responsibility."

Phase I of the LEWG's plan would span 1968-1975. NASA had logged two Surveyor soft landing missions (one of which, Surveyor 2, had failed) and one Lunar Orbiter mission by the time the LEWG turned in its report. The agency planned five more Surveyors and four more Lunar Orbiters before the first Apollo landing in 1968. Such "Block I" automated missions were primarily designed to seek out potential landing sites in the "Apollo Zone," the nearside equatorial region routinely accessible to Apollo spacecraft.

The years 1968-1969 would see three Apollo lunar landings ). Two astronauts would spend from 18 to 36 hours on the moon, venturing on foot no farther than one kilometer from their Lunar Module (LM) (see 1966 image at the top of this post). A third astronaut would orbit the moon in a CSM. Mission accomplished, the moonwalkers would lift off in their LM's ascent stage, rendezvous and dock with the CSM, and return to Earth.

Advanced Lunar Orbiter and Surveyor missions would follow the three Apollo flights. The LEWG proposed that five Block II Lunar Orbiters photograph the entire lunar surface between 1969 and 1971, and that ten Block II Surveyors land between 1970 and 1975, possibly visiting sites too remote and perilous for piloted landings. Block II Surveyors might carry automated rovers. Between 1972 and 1974, three Block III Lunar Orbiters would chart surface topography and composition, perhaps employing high-resolution film cameras. Exposed film might be recovered for return to Earth by astronauts spacewalking from Apollo CSMs. The LEWG proposed that Lunar Orbiters serve also as radio relays for landings in the lunar farside hemisphere, the side of the moon not visible from the Earth.

Phase II, spanning 1970 to 1973, would encompass NASA's planned Apollo Applications piloted lunar flights. NASA set up the Saturn-Apollo Applications (SAA) Office in August 1965. Within a year, SAA became known as the Apollo Applications Project (AAP). AAP was to include Earth-orbital space station missions and advanced lunar missions building on technology developed for the Apollo lunar program. The LEWG recommended one AAP lunar mission per year, each requiring two Saturn V launches. The first Saturn V of each mission would launch an LM Shelter and a CSM with two astronauts on board. The LM Shelter would include supplies and exploration gear in place of ascent systems. Using controls on board their CSM, the orbiting astronauts would remote-pilot the LM Shelter to a landing, then return to Earth.

The second Saturn V would then place three astronauts, a CSM, and an LM Taxi on course for the moon. Two astronauts would land near the LM Shelter in the LM Taxi and make it their base camp for 14 days of exploration. They would drive up to eight kilometers from the landing site on a 1000-pound Local Scientific Survey Module (LSSM) rover. Mission accomplished, the astronauts would return to the LM Taxi, lift off in its ascent stage to rejoin their lonely colleague on board the orbiting CSM, and depart lunar orbit for Earth.

The LEWG recommended three Phase III "Mobile Exploration" expeditions in 1974-1976, each requiring one standard Saturn V and one uprated Saturn V. The uprated rocket would place a new-design L-II landing stage with a camper-like MOBEX rover on top on course for the moon. The L-II's rocket motors would place MOBEX in lunar orbit, then would ignite again for descent and landing. After touchdown, the 9.9-ton rover would automatically unload from the L-II. The standard Saturn V would then launch three astronauts to lunar orbit. They would shut down their uprated CSM and descend in an uprated LM Taxi to land near the MOBEX, which would trundle up to meet them under remote control from Earth.

After mothballing their lander and checking out the MOBEX, the three explorers would set out on a loop traverse. Possible routes would include the 780-mile "Northwest Cloverleaf," which would take in the prominent craters Kepler and Aristarchus, and the 840-mile "East Loop," which would include Copernicus crater and the Carpathian Mountains. The LEWG envisioned frequent stops lasting several days, during which the astronauts would drill for samples, set out instrument packages, and explore using an LSSM. Ninety days after landing, the astronauts would return to and reactivate their LM Taxi, lift off in its ascent stage, dock with and reactivate the orbiting CSM, and return to Earth.

The fourth and final phase of the LEWG plan would see three missions spanning 1977 through 1980, each requiring three uprated Saturn V launches. The venerable Apollo LM and CSM spacecraft would be retired in favor of a Direct Ascent lander - that is, one which would transport its crew directly to the moon and back with no rendezvous and docking in lunar orbit.

The first uprated Saturn V of each Phase IV mission would launch a MOBEX and an L-II landing stage to the moon. The second would launch an unpiloted, two-deck Lunar Laboratory Module (LLM). Delivering the heavy LLM to the moon would require an L-I course correction/lunar orbit insertion stage in addition to the L-II. The third uprated Saturn V would launch the Direct Ascent lander with six astronauts on board. They would ride in a modified Apollo Command Module (CM) lacking a docking mechanism.

In addition to the CM and L-I and L-II stages, the Direct Ascent lander would include an L-III stage for launching the CM directly back to Earth from the moon's surface. To trim development costs, the L-I, L-II, and L-III stages would have a similar design, though L-II would have landing legs, and L-III would use storable propellants in place of the liquid hydrogen/liquid oxygen propellants in L-I and L-II.

The LEWG's LLM habitat would be based on a design for a Mars spacecraft Mission Module, while the modified CM would be based on the Earth-return vehicle for piloted Mars flyby missions. The LEWG hoped that sharing technology with NASA's planetary program would cut costs. The six astronauts would live in the Temporary Station for up to 180 days while taking their MOBEX on two or more long traverses.

The LEWG anticipated that the MOBEX could be the most difficult design challenge, so targeted its development to begin before 1969. L-II landing stage development would begin soon after. Development for Phase IV would commence by 1974, with a Direct Ascent lander test flight occurring in 1977. Each Phase III mission would cost $650 million, while one Phase IV mission would cost $1.2 billion. Total cost for all four phases would come to about $20 billion.

Lunar Exploration Program Plan, Lunar Exploration Working Group, NASA, November 1, 1966.