|Where No Man Has Gone Before: A History of Apollo Lunar Exploration Missions|
LUNAR EXPLORATION CONCLUDED
Apollo 17: The Close of an Era
Following completion of Apollo 15, with 16 in the planning stages and only one mission remaining after that, one scientist expected that the process of choosing a site for the last flight would be "a dilly of an affair."72 Perhaps with that thought in mind, Rocco Petrone, Apollo program director at NASA Headquarters, started the procedure early, in October of 1971. After a site evaluation document had been circulated among selected interested scientists for their critique and response, an ad hoc site evaluation committee would meet no later than December 30 to consider site proposals and make recommendations to the Apollo Site Selection Board in early 1972.73
Actually, site selection for Apollo 17 was not as difficult as might have been expected, considering that it was the last chance for many years to obtain material and data from the moon. Preliminary review of possible sites produced a clear consensus of objectives for Apollo 17: to investigate the pre-Imbrian highlands as far as possible from the Imbrium basin; to sample "young" volcanics; to obtain photographic and remote-sensor coverage of areas not previously investigated; and to provide the best coverage for the new traverse geophysics experiments that were to go along. Application of all these considerations reduced the interesting sites to three: Taurus-Littrow, a region on the southeastern rim of Mare Serenitatis; Gassendi, a large crater on the northern rim of Mare Humorum; and (ranking a distant third) Alphonsus, previously considered as an alternative to the Descartes site. Of these three, the ad hoc site evaluation committee concluded that Taurus-Littrow was the best. It was a two-objective site (highlands and young volcanic material); it offered a reasonable contingency for a walking mission in case the lunar rover should fail; and it would provide the greatest amount of new information from the orbital sensors in the service module.74
Operational considerations, taken up at the February meeting of the site selection board, gave no site a clear advantage. Problems existed at all three, although Alphonsus, already well studied, was acceptable. At Gassendi there was a good chance that the astronauts would not be able to get to their prime objective if they had to land beyond the nominal 3-sigma ellipse. For Taurus-Littrow, detailed studies at first indicated that under "worst-case" conditions the site was unsuitable; the 3-sigma ellipse could not be fitted into it. When trajectory designers were urged to reconsider their calculations in light of the results of Apollo 15, however, they produced some less conservative numbers and the site was acceptable. With operational considerations out of the way, the board picked Taurus-Littrow because of its greater scientific potential.75
The Taurus-Littrow site was a flat-floored valley some 7 kilometers (4.3 miles) wide, a dark, bay-like indentation in the broken mountain chain on the eastern edge of Mare Serenitatis, at 20 degrees 10 minutes north latitude, 30 degrees 46 minutes east longitude. Bounded on three sides by high mountain massifs, the valley contained numerous craters of possible volcanic origin, as Al Worden had noted from orbit on Apollo 15.76
Premission data from the landing site indicated it to be geologically complex. Rock types appeared to vary in age, composition, and probable origin, and the mountains displayed structural features that might be correlated with several major landforming events. The valley floor on which Apollo 17 was to land appeared to be volcanic and thus might have originated deep within the moon. A landslide intruded on one side of the valley floor, and boulder tracks down the mountainsides added to scientists' interest in the site.77
Until early 1971 Apollo 17 had been scheduled for June 1972; in February the launch schedule was revised and both Apollo 16 and 17 were moved forward, to March and December 1972, respectively.78 The new launch date for Apollo 17 required one more launch constraint to be lifted, because Taurus-Littrow was not accessible by translunar injection (departure of the spacecraft and S-IVB from the earth parking orbit) over the Pacific Ocean. Early in the program Pacific injection was adopted as the rule, since the alternative - injection over the Atlantic - required a night launch at some times of the year. Although Atlantic injection offered an economy in fuel and thus an increase in allowable payload, the potential problems incident to a night launch (see Chapter 6) tipped the scales.79 By the time the site selection board met in February 1972, however, "the bullet had been bitten on night launches"80; experience had made those problems much less worrisome.
So it was that Apollo 17 was scheduled to leave the Cape at 9:38 p.m. EST on December 6, 1972.81 From August 8, when the launch vehicle was moved to the pad, preparations went well. Some minor hardware problems cropped up but were handled without delaying the schedule. Launch day was bright and warm; the temperature was in the mid-80s at midafternoon. All looked well for the last Apollo mission until 30 seconds before launch, when the automatic sequencer - the oldest and most reliable piece of automation at the launch complex - shut the system down. The first launch delay in the Apollo program caused by failure of equipment amounted to 2 hours and 40 minutes while Cape and Marshall Space Flight Center engineers worked around the malfunction. At 12:33 a.m. Eastern Standard Time on December 7, command module America and lunar module Challenger were off for Taurus-Littrow.82 Flight controllers made up the lost time during the translunar coast.83
America and Challenger entered lunar orbit on schedule and all preparations for landing went smoothly. After the two spacecraft separated, Cernan and Schmitt took a spectacular photograph of their landing site. Three hours later Cernan powered up Challenger for its descent. It touched down within 200 meters (650 feet) of its targeted landing point amid a field of craters at 3: 15 p.m. EST on December 11.84
For the next 75 hours Cernan and Schmitt conducted the longest, and in many ways the most productive, lunar exploration of the Apollo program. During three trips from their base they laid out the surface experiments, drove the lunar rover about 36 kilometers (22 miles) in all, ranging as far as 7.37 kilometers (4.5 miles) from Challenger, and collected roughly 243 pounds (110 kilograms, of soil and rock samples along with more than 2,000 documentation photographs.85
Like their predecessors, Cernan and Schmitt were somewhat constrained by the preplanned sequence of activity. Still, before they left the lunar module and while unloading the Rover and the surface experiments, Schmitt found time to give Houston's back-room scientists both large- and small-scale descriptions of the landing area and the surface under his feet.86 Schmitt found the environment in the landing area "superb" for observation: the lighting was excellent and the rock surfaces generally clean, and he found little difficulty in distinguishing mineralogical and textural differences. For the most part he based his decisions on taking samples on visually detectable differences or similarities.87
Besides collecting and documenting samples, on their traverses the explorers laid out explosive charges for a seismic profiling experiment (the charges would be set off after they left), took readings on a portable gravity meter at various points along the route, and set up an instrument to measure electrical properties of the lunar surface. At the site for the surface experiments package they drilled two 2.54-meter (8.3-foot) holes for heat-flow sensors, took a deep core sample, and set up the geophones (detectors) for the seismic profiling experiment.88 The first excursion was largely taken up by these chores.
After an overnight rest and a discussion with Houston concerning plans for sampling, Cernan and Schmitt set out on their second trip to collect specimens from boulders along the lower slopes of the South Massif and to sample the lighter-colored soil that overlay the western part of the valley. It was a long trip - an hour by rover to the first major sampling stop - and would stretch their life-support systems almost to the limit. The last couple of kilometers up the slope taxed the rover, too, but it brought them to their objective in fine style. Schmitt took samples from three boulders which, as best he could tell, had come from layers visible farther up the South Massif.89
The obviously interesting features of their first site prompted Houston to lengthen their stay there and cut some time from later stops. On their way back they stopped to take an unscheduled reading on the traverse gravimeter and sampled soil at a couple of crater rims, one of which drew considerable attention. During routine examination of the surface around the crater called "Shorty," Schmitt suddenly called out, "Oh, hey - wait a minute - . . . There is orange soil!" Cernan confirmed it. "He's not going out of his mind. It really is." While looking for the limits of the orange deposit, Schmitt remarked, "if there ever was something that looked like fumarole alteration, this is it."90 He was excited because orange soil (characteristic of oxidized iron, at least on earth) indicated volcanic activity, probably recent, a feature not previously discovered on the moon. While Houston kept reminding them they were almost at the limits of their walk-back capability - time was running out - they dug a trench, took a core sample and several scoop samples, and took photographs. Then they mounted the rover to head back to Challenger. Schmitt talked about his discovery all the way back.91
The last sampling trip of the Apollo program was a traverse to the foot
of the North Massif, where they found two large boulders that had
obviously rolled down from outcrops higher on the mountain; their tracks
were visible in the soft soil. After covering 12 kilometers (7.5 miles)
and picking up 63 samples (137 pounds, 62 kilograms), Cernan and Schmitt
returned to the lunar module.92 Schmitt
picked up a symbolic rock sample in honor of a group of foreign students
touring the United States; it would be divided up to provide samples for
each country represented. Then Ceman unveiled a plaque on
Next day, December 14, they blasted off to join America in lunar orbit. As television audiences on earth watched, the rover TV camera, directed from Houston, followed their ascent stage until it was out of sight, then slowly scanned the now-deserted lunar surface.95 The awareness that no living person was around made the scene all the more impressive. It was almost possible to hear the silence.
After hooking up with the moon-circling command module, Schmitt and Cernan transferred their samples and data. America still had a day's work to do, completing the photographic and remote-sensing work that Ron Evans had been doing while his crewmates were on the surface. Their work completed, the crew of Apollo 17 left the moon with a blast from their service propulsion engine at 8:42 p.m. EST on December 16. A routine transearth coast brought them back to a landing about 300 kilometers (200 miles) east of Pago Pago at 2:25 p.m. EST on December 19, 1972.96 Apollo's exploration of the moon, "one of the most ambitious and successful endeavors of man,"97 was over.
While scientists awaited the samples from Taurus-Littrow, editorial
writers offered varying evaluations of the lunar exploration project.
Perhaps the bitterest farewell to Apollo was expressed by William Hines,
syndicated Chicago Sun-Times columnist, who had opposed the
project from the start: "And now, thank God, the whole crazy
business is over."98 The
Christian Science Monitor cautioned that "Such
technological feats as going to the moon do not absolve people of
responsibilities on earth."99 The
New York Times decided that "Man's entire perspective
on the universe and on his place in it has been radically changed. Man
evolved on the earth, but he is no longer chained to it."100 Time magazine noted that after
the magnificent effort to develop the machines and the techniques to go
to the moon, Americans lost the will and the vision to press on.
Apollo's detractors, said Time, were
72. Bruce R. Doe to Homer E. NewelL, Oct. 18, 1971.
73. Petrone to multiple addressees, "Apollo 17 Site Selection," Oct. 28, 1971.
74. N. W. Hinners to Capt. W. T. O'Bryant, "A.S.S.B. Minutes," March 23, 1972; O'Toole, "Moon Landing Site Chosen For the Last Apollo Flight," Washington Post, Feb. 17, 1972.
75. Hinners to O'Bryant, "A.S.S.B. Minutes"; idem, "Apollo 17 Site Selection," in Apollo 17 Preliminary Science Report, NASA SP-330 (Washington, 1973), pp. 1-1 to 1-5; John R. Sevier, interview, Apr. 24, 1986.
76. T. McGetchin and J. W. Head, "Lunar Cinder Cones," Bellcomm paper, Aug. 4, 1972; Apollo 15 Preliminary Science Report, p. 25-17.
77. OMSF, "Mission Operation Report, Apollo 17 Mission," report no. M-933-72-17, Nov. 8, 1972; "Apollo 17 Site Selection," NASA Release 72-44, Feb. 16, 1972; Harrison H. Schmitt, "Apollo 17 Report on the Valley of Taurus-Littrow," Science 182 (1972):681-90; Apollo 17 Preliminary Examination Team, "Apollo 17 Lunar Samples: Chemical and Petrographic Description," ibid. pp. 659-72.
78. McDivitt to multiple addressees, "Apollo launch dates," Feb. 22, 1971.
79. John O. Cappellari, ed., "Where on the Moon? An Apollo Systems Engineering Problem," Bell System Technical Journal 51(5) (May-June 1972): 1033-45.
80. Hinners to O'Bryant, "A.S.S.B. Minutes," Feb. 11, 1972; Petrone, TWX to McDivitt, subject: "Apollo 13 March Launch Window," Dec. 4, 1969; Gilruth, TWX to Petrone, subject: "Night Launches," Jan. 28, 1970.
81. McDivitt to multiple addressees, "Apollo 17 Landing Site," Feb. 23, 1972.
83. Apollo 17 Mission Report, p. 1-1.
84. Ibid., p. 3-2.
85. Ibid., pp. 1-1 to 1-2; Schmitt, "Apollo 17 Report on the Valley of Taurus-Littrow."
86. MSC, "Apollo 17 Technical Air-to-Ground Voice Transcription," Dec. 1972 (hereinafter cited as "17 Air-to-Ground"), tape 76A, pp. 4-8, tape 77A, p. 34, 39-41. This transcript is paginated by tape number; tape numbers run sequentially in three series, A, B, and undesignated, corresponding to communication with the lunar module (A) and the command module (B) when the two were separated, and with the command module when all three crewmen were aboard before and after separation (undesignated).
87. Schmitt, "Apollo 17 Report," p. 682.
88. Apollo 17 Mission Report, pp. 4-5 to 4-11.
89. 17 Air-to-Ground, pp. 91A/1-94A/25; Apollo 17 Mission Report, pp. 10-15 to 10-16; Apollo Field Geology Investigation Team, "Geologic Exploration of Taurus-Littrow: Apollo 17 Landing Site," Science 182 (1973):672-80.
90. 17 Air-to-Ground, pp. 96A/8-96A/10.
91. Ibid., pp. 96A/11-96A/55.
92. Apollo 17 Mission Report, pp. 10-16 to 10-17.
93. Ibid.; 17 Air-to-Ground, pp. 112A/20-113A/1.
94. 17 Air-to-Ground, pp. 113A/1-3.
95. "Apollo 17 at Taurus-Littrow," NASA EP-102, p. 30.
96. Apollo 17 Mission Report, pp. 3-2, 12-4, 12-5.
97. Ibid., p. 1-3.
98. William Hines, "End of a crazy business," Chicago Sun-Times, Dec. 21, 1972. Hines went on to castigate the Apollo project from concept to execution, and concluded by quoting Max Born, Nobel laureate in physics, who had said in 1958 as the "space race" began, "Intellect distinguishes the possible from the impossible; reason distinguishes the sensible from the senseless. Spaceflight is a triumph of intellect and a tragic failure of reason."
99. Christian Science Monitor, Dec. 21, 1972, cited in Astronautics and Aeronautics, 1972: Chronology of Science, Technology and Policy, NASA SP-4017 (Washington, 1974), p. 440.
100. New York Times, Dec. 14, 1972, cited in Astronautics and Aeronautics, 1972, p. 429.
101. Time, Dec. 11, 1972, cited in Astronautics and Aeronautics, 1972, p. 424.