By early 1969 JPL had sketched the practical requirements of spacecraft design and launch trajectories for variants of an outer-planet survey, and was even using its dazzling vision as a recruiting device. James Long summarized the options for a multiple-year, multiple-mission reconnaissance, concluding that such a scheme was feasible as well as “a timely—virtually unique—opportunity for exploration.” Within the year William Pickering was promoting the Grand Tour through American Scientist. Throughout, there were two selling points: one, that the cost of going to the outer planets was essentially the same as going to Jupiter alone, since the critical added velocities came from Jupiter’s gravitational assist; and two, that the alignment of the planets was, from a programmatic perspective, providential. There was every incentive not only to seize the “superwindow” offered but to make as complex a mission as possible in order to magnify that opportunity, perhaps including orbiters and landers. What the Viking mission would do on Mars, the Grand Tour could do across the solar system.25
In this, the first of its journeys, Voyager had achieved a breakthrough by means of a shift in reference frames, and that is exactly what Voyager has continued to do throughout its long trek. The process started at its conception, by seeing a hypothetical spacecraft differently, and it will end by forcing us to see ourselves differently. But as William James once put it, “truth happens to an idea.” Gravity assist happened when Mariner 10, launched in 1973, swung around Venus and Mercury exactly as predicted. The scheme worked, shaving rocket fuel loads as much as 70 percent. A spacecraft could reach the outer planets and still be sentient, if not fully ambulatory.
The primary propulsion system for Voyager was, in the end, intellectual. It was the idea of the Grand Tour.
It seemed irresistible. Both the scientific community and the American media seized on the scheme. By 1971 the Space Science Board had endorsed the proposal; NASA lent approval for further studies, and JPL had plunged into a flurry of inquiries. Here was the scotched Mars Voyager resurrected. Here was a dazzling prospect for technological challenge and first-order exploration. Here was promised a marker in the centuries-long saga of exploration. The last time this planetary conjunction had appeared, Alexander von Humboldt was halfway through his monumental trek across South America; before that, Jan Carstensz had just navigated around Australia’s Gulf of Carpentaria, finding nothing of worth, and Plymouth Plantation had settled in New England, still looking eastward, and more intent on the reformation of the Old World than westward to the colonization of a New; and before that, Portugal had barely passed Cape Verde, still stutter-stepping toward the Renaissance’s Great Voyages. By the next conjunction, 2153, the planets would have been explored singly. The exploration of the solar system for the first time could happen only once. A Grand Tour could do that.
Enthusiasm was keen: opportunity seemed like inevitability. How could anyone oppose such a fabulous conception? By 1977, when the ideal launch window would appear, the technology, the managerial skills, the instrumentation, and the hands-on experience of navigating probes through interplanetary space would be sufficient. Were the launch window to come five years earlier, those means would not have existed, and had they arrived five years later, the opportunity might have been lost. It was inconceivable that anyone might deny the Grand Tour its call to destiny.
Studies boomed, not least because the options for surveying the outer planets, especially if two spacecraft were launched, were surprisingly rich. Three combinations particularly intrigued planners. One was a three-planet mission to Jupiter, Uranus, and Neptune. Another three-planet mission targeted Jupiter, Saturn, and Pluto. The last version was a four-planet mission to Jupiter, Saturn, Uranus, and Neptune. Each mission would involve multiple launches. It was even possible, if barely, to imagine a flotilla of missions that would collectively sample all of the outer planets with reasonable completeness.26
Meanwhile, on July 31, 1969, only fifteen days after Apollo 11 landed on the Moon, Mariner 6 entered orbit around Mars, followed five days later by Mariner 7, offering for the first time an effort to synchronize two simultaneously exploring spacecraft. To observers it seemed that a Grand Tour had to follow. Nothing else could claim anything like its cachet. It remained only to select the most savory of the potential offerings and then render it into a machine to cross the solar system, even though neither the technology nor launch vehicle for such an enterprise existed, nor the political determination to go. JPL’s preference was for a program built around a new vehicle, a spacecraft more durable, expansive, and autonomous than the Mariner series, and one that could survive a hostile decade in space. This required, among many features, a computer that could undertake on its own some routine testing and repairs, and an energy system not dependent on sunlight. The new vehicle, called Thermoelectric Outer Planet Spacecraft (TOPS), promised to be as expensive as it was daring. The Grand Tour deserved nothing less.
By 1970 NASA had formally assigned an Outer Planets Grand Tours program to JPL, which endowed a Grand Tour Project Office, which commenced to sort through the preliminary studies and announced a call for proposals for the scientific package. Estimated costs ranged from $750 million to $900 million, a prince’s ransom at the time. Still, the Office of Management and Budget (OMB) liked it as an expression of national prestige, and approved some funding for planning. On March 7 President Nixon declared unequivocally for a Grand Tour, with preparations to begin in 1972. By summer some five hundred scientists had submitted proposals for what would be a dozen experimental slots. But in some respects, the winnowing hardly mattered. Where so little was known, everything was there to be learned. JPL petitioned NASA headquarters for a formal authorization, and NASA approved, contingent on congressional funding.27
THE GRAND TOUR OPPOSED
Yet what excites some can cause in others an allergic reaction. The Grand Tour unexpectedly rallied a grand alliance to oppose it. The usual motives came into play, from squabbling over money to disciplinary jealousies, some reasons honorable, some petty. The bottom line was, what the cold war gave, it could also take away, by proposing competitors eager for the same government funds and stature. Nor was the space community united. What seemed to true believers a juggernaut providentially aligned with the stars appeared to others more like Oliver Wendell Holmes’s rickety “one-hoss shay.”
The most universal concern was cost, which was serious and might go ballistic despite close attention. Even before Apollo 11, NASA’s budget was fast ebbing, and the commitment to the space shuttle threatened to become (and did become) a fathomless fiscal sinkhole. Apollo 16 and 17 were canceled. President Nixon decided, along with NASA strategists, that the future belonged with the space shuttle, an American Concorde, which could also quell industry unrest over the cancellation of a supersonic transport (SST). There was not enough in the Treasury to support both robotic Grand Tours and human-steered SSTs, much less fight foreign wars and finance a Great Society. Besides, the political calculations were overwhelming. The shuttle meant thousands of jobs; an outer-planets spacecraft, prime work for a thousandth as many voters. The reality was what Harris “Bud” Schurmeier, a key JPL manager and prime mover behind the embryonic Voyager mission, blandly said it was, that “planetary exploration has inevitably been insignificant on a national scale, low on the agenda, small in the budget.” Start-up funds for the Grand Tour were slashed to $10 million from a requested $30 million.28
The funding might be finessed. A single mission, even if expensive, might be easier to sell than five, each of which offered tempting political targets. But what threatened to fatally compromise the Grand Tour was intramural fighting among space scientists. A Grand Tour was big science that risked alienating academic little science, and it was a big-budget item that competed directly with a big-budget item craved by astronomers: a space telescope. Those groups whose research did not extend to the outer planets or who were not slated to join the eleven science teams on the spacecraft offered tepid support, or became hostile, viewin
g the funds lavished on the Grand Tour as siphoning precious monies that might go to their own projects. There was already a big-science mission on the boards, the reincarnation of Mars Voyager into Viking; and the search for life on Mars seemed likely to muster broader enthusiasm from both the scientific community and public than mapping the magnetosphere of Uranus.
Even enthusiasts for outer-planet exploration could legitimately doubt whether now was the proper time, or a Grand Tour the proper means. The NAS Space Science Board had conducted a major study in 1965. While urging NASA to think beyond the Moon, the board had concluded that an intensive study of Jupiter was a better bet than far-ranging flybys; and that if missions to the other gaseous planets were feasible, single shots were a more conservative hedge than a romantic Grand Tour. NASA then constituted an Outer Planets Working Group, with representatives from all its field centers that had an interest in the scheme, and again the consensus favored parsing the Grand Tour into more manageable excursions or crafting a compromise in which two missions would each tour three of the outer planets—all this on the grounds that the engineering was more likely to succeed and the richer returns would be more widely distributed among planetary scientists (a narrower version of the jobs argument) .29
In June 1969 NASA invited the Space Science Board to reconsider. The Board reconfirmed its belief that “study of the outer solar system” was a “major objective of space science” and that the community was “eager and excited.” It urged that NASA increase the fraction of its budget devoted to planetary exploration, that Pioneer-class spacecraft lead the endeavor, and that Jupiter be the first object of outer-planet missions, with a mix of Grand Tour projects to follow if funding proved adequate. But it also reasserted its original position that the Grand Tour should be not one but several missions. Specifically, it argued for five, all of which would either target Jupiter or use it for gravity propulsion. The JPL scheme was deemed at or beyond the limits of engineering expertise. It was risky, its success uncertain, and its costs extreme.30
The Grand Tour’s promised payoff, while glamorous, seemed meager compared to what might be done by other means, and worse, its unstanched costs threatened to bleed space science dry. (By now Voyager had become a surrogate for criticism of Viking, which was further along in its development and much more costly.) The SSB nearly recommended outright termination. After discussions with the OMB, NASA returned to what was becoming the default setting: two missions launched over two or three years to reach two or three planets. Had the Grand Tour been a launched missile, with its wobbly path so badly out of trajectory, it would have been blown up. It was kept, although its woes seemed an unsavory augury for what became Voyager. Meanwhile, the SSB, while sanctioning planetary exploration as a “major objective,” recommended halving the funding level, thus taking away with one hand what it gave with the other. The SSB urged more near-Earth activity and, led by astronomers, wanted an orbiting telescope. If robotic spacecraft could do science that humans couldn’t, then a telescope could do much of that science without the robots. The proposal in effect sought to sever science from exploration.31
Other critics, led most visibly by James Van Allen of the University of Iowa, protested the magnitude of the NASA investment in crewed programs to the detriment of robotic missions; the former did no science worth mentioning, and given a fixed (or inflation-ablated) budget, a sharp tilt toward manned space flights, in a kind of bureaucratic sheet erosion, would drain funds away from all the rest. (With no specific appropriation for the shuttle, NASA had to absorb internally its development costs, which escalated from $12.5 million in 1970 to $78.5 million the next year.) This promised to scrap everything that could not fit into the shuttle’s bay. The opposition to crewed programs spurred a counter-protest against robots, and gave NASA critics overall additional arguments against both programs . 32
The deeper concern,thoughonly implied, wasto question whether science needed spacecraft at all. For the present it did, as the SSB observed. Several fields of interest—the kind that the International Geophysical Year had pursued in the upper atmosphere of Earth—had “no known alternative to the techniques of direct observation near, or within, the object of investigation.” The only way to put an instrument in such proximity was with a spacecraft. But if other means became available, they might well, from the perspective of science, be superior. One could dispense with spacecraft as robotic spacecraft did with astronauts.33
Even within NASA, competition was keen. The agency was a forced merger of institutions that had their own traditions, goals, and styles, and that were avid to contest against one another. So long as money had been ample, every research group and every facility could get something that it wanted; but when choices had to be made among them, a competitive scramble resulted among institutions, among projects, among personalities, among ideas, among visions of what “space,” “science,” and “exploration” meant. This held even as NASA’s head, James Fletcher, insisted that no such internal trade-offs existed (no one believed him) and that the space science community had to unite behind all programs. “Science” by itself had “very little political support,” he noted, but “space” meant “technology, applications, and political prestige” (all of which was marginally more acceptable). Regardless, the space science community fissured, and that chasm split the larger space lobby.34
The crunch came in 1971. The NAS Space Science Board met for an intensive study seminar in early August, argued again to bolster NASA’s planetary program, reaffirmed a 1970 study that established priorities for space research, and concluded that regular or even intermediate funding was not sufficient for Grand Tour missions “without jeopardizing the Planetary Explorers [Pioneer] and key programs of the other scientific disciplines.” The 1971 session also folded in recommendations from the President’s Science Advisory Committee. For the outer planets, it urged as a priority a Jupiter study by “Pioneer-level technology.” The JPL ambition for a Grand Tour with a new spacecraft found support only if NASA received its “HIGHER budget program”—an improbable outcome. Still, the SSB supported development of TOPS-class spacecraft and an enhanced Titan rocket to launch it; and it introduced the prospects for “satellite imaging,” which it thought might “constitute the most solid justification for [a] Grand Tour.” The intellectual returns from remote moons, however, could not outflank the staggering expenses and the aroused alliance of rivals within NASA and the space-science community.35
A body in shock pools blood from its outer limbs to its vital organs; so, too, with bureaucracies. Congress had not backed Nixon’s rhetoric with real money. NASA redirected the flow of funds from the outer planets to near-Earth activities and to that most Earth-like planet, Mars. Like the tall poppy that gets cut down, the high-visibility Grand Tour was a tempting target—something almost everyone liked in principle but few were willing to sacrifice for. NASA decided that its institutional future lay with humans in space. In December 1971 Administrator James Fletcher wrote the Office of Management and Budget that NASA would cancel the Grand Tour. In January 1972 that announcement became public.36
THE GRAND TOUR REVIVED
The Grand Tour was dead. Its spirit, however, proved harder to kill, and it quickly transmigrated into another avatar.
Within ten days, JPL proposed an alternative. It would scale back the full-bore Grand Tour into paired visits to Jupiter and Saturn. It would adapt the proven Mariner spacecraft rather than, Viking-like, invent a new one from scratch such as TOPS. It would pare costs from $900 million to $360 million. It would co-opt critics from the start, particularly enlisting support from the SSB and OMB. And it would, with sly ambiguity, allow for the option of tweaking the second flight to swing past Saturn and rendezvous with Uranus and perhaps Neptune. The metempsychosis was complete. The Grand Tour had become Mariner Jupiter/Saturn 1977 (MJS 77).37
NASA accepted the proposal in June and signed a formal project agreement in December, assigning Bud Schurmeier as project manager and assembling
a Science Steering Group. JPL began reorganizing immediately. Even this furled-sail mission went far beyond anything attempted to date, not only geographically but technologically and administratively. (Pickering insisted that “something more than ‘organized arm waving’ ” was needed to ensure confidence that a spacecraft could even survive to a “far planet encounter.”) Just getting to Saturn was tricky enough: the projected three-and-a-half-year voyage was six times longer than any that had flown. The most advanced power source would last only a year; sensitive equipment had to endure the hazards of interplanetary and near-planetary space, ranging from micrometeorite bombardment to saturated radiation; and navigating a spacecraft through rings, radiation belts, and moons while adjusting sensor platforms demanded an unprecedented choreography of commands. Communications could barely handle a trek to Venus or Mars, and while improvements were expected, the distances were too great to rely on human judgment during crises, which meant a spacecraft would have to analyze and repair itself. Some technology had to be new, not simply adapted. Some could be expected to need correction based on the Pioneer 10’s encounter with Jupiter in 1973 and Pioneer 11’s encounters with Jupiter and Saturn in 1974 and 1979, respectively. The whole science selection process had to be renewed, which was certain to revive ill feelings. And while everything had to be done on schedule and on budget, nothing done should inherently prevent a reincarnated full-bore Grand Tour.38
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