For much of the 20th Century, humanity has been getting used to the idea of people traveling through space and, eventually, living and working on worlds other than Earth. During the first half of the century, pioneers like Konstantin Tsiolkovsky, Robert Goddard, Wernher von Braun and others thought and wrote about space travel and slowly worked out some of the basic technologies that would make it possible. Science fiction writers extrapolated even farther into the future and, long before anyone actually worked out the details of building a spaceship, the fiction writers put cities of the imagination on the Moon and Mars and filled the spaceways with passenger ships and cargo vessels busily engaged in interplanetary commerce. For some people, acceptance of these outlandish notions was out of the question; but, by the time Yuri Gagarin made the first spaceflight in 1961, a sizable fraction of the literate world had been exposed, at least, to the dream of space as a frontier. Although interplanetary commerce will have to wait for the 21st century, by the late 1950's the dream had become familiar enough that, when John Kennedy proposed a lunar landing as a technological feat to impress mankind, almost everyone involved - those who would do the work, those who would pay for it, and those whom Kennedy sought to impress - understood the symbolism. Here was a big, bold step into the future.
Unfortunately, Apollo was so bold a step that the pace could not be sustained. Into the late 1960's, the space community had high hopes that Apollo would lead directly to the construction of a permanent base on the Moon and, sooner rather than later, to the first voyages to Mars. Von Braun and his collaborators had sketched such projects in a series of articles published in Collier's Magazine in the early 50's; and, once the big rockets were actually being built and the first lunar landings were at hand, there were moments when it almost seemed as though the Moon Base and Mars were in reach. But it was not to be; and, indeed, hindsight suggests that, because of economic and political factors, there was no real chance of sustaining Apollo beyond a handful of landings.
The main reason why Apollo ended as quickly as it did was simply that it was very expensive. The Space Age began during a period of intense rivalry between the United States and the Soviet Union and, during the four years that led up to the Apollo decision, America was subject to one humiliation after the another. Russian leader Nikita Khrushchev had bid the political value of dramatic space "firsts" so high that, in response to the Gagarin flight, President Kennedy had to find a way of achieving a clear, unambiguous, final victory in what had become the "Space Race". What was required was an undertaking "so expensive and so difficult to accomplish" that the Russians would have little chance of keeping pace. So Kennedy committed the United States to a giant step forward. However, Apollo was so expensive and so difficult that it could not continue for very long. America's political will to win the Space Race could not be translated into political and financial support for sustained lunar operations, not to mention voyages to Mars. At its peak in 1965, the annual cost of Apollo was about 0.8 percent of the U.S. Gross Domestic Product and, as more recent history suggests, there is political support for a program only a quarter that size.
The evidence of the years since Apollo ended is that the United States and many other nations are committed to space, partly as an investment in the development of new technologies, partly in the interest of attracting talented young people to engineering and the sciences, partly in the interest of participating in the long-term economic gains that space is expected to produce, and also, in large measure, because there are few other things now within human reach that are quite so fascinating. In the United States, political support for space development currently translates into a funding of about 0.25 percent of the Gross Domestic Product. In the early 1990's, the NASA budget was about 15 billion dollars: enough to support the operation of a four-vehicle Shuttle Fleet, the development of a Space Station, and the conduct of a variety of scientific and engineering programs, but not enough to include a lunar program as well.
Clearly, it was only the extraordinary political circumstances of the 1960's that made Apollo possible. For a brief time, whatever money NASA needed to achieve the promised first landing was made available. However, once the major pieces of the Apollo engineering work were finished, funding began to shrink. The United States was willing to spend what was needed to beat the Russians; but, once the Space Race was decisively won, the country's political leaders decided that the cost of a continuing lunar program was more than the country could afford. The space budget even shrank to the point that NASA had to cancel three Apollo missions for which flight vehicles had already been built.
Over time, of course, economic expansion makes projects like a Moon Base more affordable and, sooner or later, we will be able to undertake a lunar program without having to spend an Apollo-like fraction of the nation's wealth. During the past century and more, the American GDP has doubled in real terms about once every twenty-five years and there is every reason to believe that growth will continue for a long time to come. Economic expansion comes largely as a result of gains in productivity and, certainly, the limits to our creative use of new machines, new processes, and new resources are nowhere in sight. As the wealth of the nation grows and, indeed, as other nations acquire spaceflight capabilities, the total level of space activities will expand - albeit with ups and downs superimposed on the overall trend - to the point that construction of a permanent lunar base will become feasible. If, for example, we assume continued investment at about 0.25% of the growing GDP and we also assume that we could conduct a space program that included both a space station and a lunar base for about 30 billion 1990 dollars, then we might see a resumption of lunar operations - preceded by a decade or more of preparatory work - in about 2015.
Of course, if the NASA budget allotment were to grow more quickly than the economy as a whole, we could build the lunar base sooner than 2015.
During the 70's, it was sometimes difficult to believe that the space program hadn't suffered a fatal setback, that some ill-defined "window of opportunity" hadn't closed. By the mid-70's, NASA's budget had stopped shrinking and, measured in constant dollar terms, even grew at a modest pace; but, after the glory years of Apollo, the increments seemed far too small to bring the Space Station, the Moon Base, and the Mars missions much closer to reality. Small increments were too easily overwhelmed by the rising costs of doing business. However, for a number of years following the 1986 Challenger accident, there was a noticeable change in the national commitment. The accident - and the public reaction to it - convinced Washington that the country wanted to spend more in order to have a respectable and productive space program; and, for a number of years after the accident, NASA received hefty, annual budget increases. More recently, the demands of social programs have come into direct conflict with the space program and, as I write these words in April 1994, there is a fierce debate raging in Washington over what has become the international space station.
The space program and its supporters have been on a financial and emotional roller coaster virtually from the beginning. The debate over funding is sure to continue until the time comes that most of our activities in space are self-supporting and public funding is no longer required. The issue at the center of the debate is, of course, the relative value of the space program and, as we have discussed, the perception of space as a technology driver - coupled with the fact that plenty of people still want to rub elbows with astronauts and plenty of kids still want to grow up to be one - generates funding at a level of about one quarter of one percent of the GDP. If the rules of the game were to change, of course, then increased levels of funding might well be in the cards. If, for example, people began to think that there was a real possibility of a substantial, near-term economic return, then new funding might well become available. The space community talks hopefully about asteroid mining, about solar power satellites, and about Helium-3 mining on the Moon but, unfortunately, they have been unable to convince anyone but the faithful that the technological risks are low enough - and the potential payoffs large enough and soon enough - to warrant spending large sums of public or private money. Alternatively, the development of significantly cheaper transportation systems would make it possible to do more at the current levels of funding and, at the same time, would make a broader array of space activities attractive. However, technical innovation is only part of the answer to cheaper transportation. Of even great importance is the ability to build many copies of a new vehicle and to fly them frequently and efficiently. That is, economies of scale are crucial and, to achieve them, we will probably have to rely on increases in space activities to produce increases in demand and, therefore, decreases in unit costs.
And, finally, we might hasten our return to the Moon if we become a bit less cynical, a bit more mindful of the old maxims about preparing for tomorrow, and, in the process, manage to rediscover our old fascination with the frontier.
We shall see.
Whatever happens over the next few decades, the obstacles in our path are almost all financial and political. Given money and a mandate, it shouldn't - but might - take more than a decade to pick up where we left off with Apollo. The simple fact that six Apollo crews landed on the Moon and brought back a treasure trove of samples, data, and experiences means that the lunar base designers will have to deal with far fewer uncertainties than did the Apollo team. However, thirty-plus years - from the end of Apollo in 1972 to a restart in, say, 2002 - is a long time and, even if we wanted to reuse Apollo-era technology, little of it is left on the shelf.
We will need to re-design much of the flight hardware and surface equipment - partly to take advantage of the engineering advances of the 70's, 80's, and 90's, and partly to prepare for a very different mode of lunar operations. Apollo was designed to meet a challenging deadline for landing a first crew on the Moon. Cargo capacities were extremely limited and none of the crews stayed for more than three days. For the lunar base era, vehicles will have to be designed so that there can be regular deliveries of supplies and equipment and in quantities sufficient that crews can stay on the Moon for months at a time and learn how to put local resources to use.
Lunar base operations will be far more complex than those that were undertaken during Apollo but, if history is any guide, by building on the Apollo experience and by taking advantage of the considerable engineering advances of the intervening years, getting ready shouldn't be as difficult or expensive as Apollo.
As an example, we might note that, between 1937 and 1945, von Braun and his coworkers spent approximately 2 billion US Wartime dollars designing and testing the V-2 rocket for the German Army. Although the V-2 wasn't much more effective than the Russian-designed Scud missiles fired by Iraq during the 1991 Persian Gulf War, the cost of developing the V-2 was surprisingly close - in inflation adjusted dollars - to the cost of developing the Apollo Saturn V. In addition to the intrinsic expense of developing any new technology, one very important cause of the high cost of V-2 development was the simple fact that, at the time, there was no practical way to make more than a few basic measurements on any one test flight. When something went wrong - as it inevitably did in the years before engineers could use computers and sophisticated ground-test facilities to check out subsystems ahead of time - a series of test flights had to be conducted to pin down the source of a problem and to verify a fix. In all, the von Braun team conducted several hundred test launches, most of them spectacular failures. Twenty-five years later, when von Braun's team was designing the Saturn V, engineering design procedures and the art of telemetry had advanced to the point that only fifteen test flights (ten Saturn I's, three Saturn IB's, and only two Saturn V's) had to be conducted before the vehicle could be certified as safe enough to carry a human crew. Significantly, despite the enormous increase in complexity over the V-2, all of the test flights were successful; and, as well, the constant-dollar development cost was only about fifty percent greater than what Germany had spent on the V-2. Time brings new technologies and fresh insights and makes difficult engineering tasks far more tractable, as is graphically demonstrated that the U.S. Space Shuttle launched in 1981 carried a crew. There were no unmanned test flights. Going back to the Moon should be easier than going the first time - assuming that we don't choke the space program on red tape.
As I said at the beginning of this epilogue, for much of the 20th Century humanity has been getting used to the idea of people traveling and working and, eventually, settling in space. For fully a fifth of that century, we have been slowly sifting through the things that we learned as a results of Apollo and, in the long run, it may be that we needed time to think about it all. Because of the extraordinary circumstances of the Cold War, Apollo was undertaken on a crash schedule and, as Arthur C. Clarke suggested in an essay published during the week of Apollo 11, we had made such a great leap into space during the 60's that we needed a time of "consolidation", a period in which to assimilate the new technologies and the new perspectives. We needed to understand what it was we had done and what we had learned. Had the space program developed more along the lines that von Braun outlined in the early 50's, by the time we were ready to go to the Moon, the program might have reached a stage of relative maturity comparable to, say, the state of aviation in the post-Lindbergh/Earhart years. As with the early stages of the Air Age, the Space Age was bound to have had a period of public fascination with "firsts". But once that phase had passed and the space program had settled down to a more-or-less orderly program of development, it might have been possible, then, to think of a lunar program as a natural next step - a lunar program complete with plans for a permanent research station of the Antarctic type and, most importantly, complete with modest expectations and a commitment to the long haul.
Instead, the first lunar landing came only eight years after Gagarin and, because it had all been so expensive, few saw a point in continuing. Most people were thinking in the short term - about firsts and about races and about oldest rocks - and not about the long-term value of the Moon. Lunar operations were too expensive to continue, so why think about the long term?
Eventually, we will go back to the Moon to build a permanent base and to begin the crucial task of learning how to "live off the land" and, later on, develop products and industries that will make lunar operations self-supporting. And, if Apollo was, perhaps, a step taken out of sequence, the important point is that we did have six successful landings and accumulated a wealth of samples, data, and experiences.
Because of Apollo, we know what most of the Moon is made of and have developed some ideas about how lunar materials could be put to use - first as a way of making lunar base operations more efficient and less expensive and, then, as raw materials for the construction and operation of space-based industries. And we know, as well, some of the tricks and some of the pitfalls involved in getting work done on the Moon.
We have a great deal to learn and great deal to do. But we have been to the Moon and can put that experience to good use as we prepare, sooner or later, to go back.
Note added 7 September 2006: Since 1994, NASA's budget has kept pace with inflation, but not with growth in the US Gross Domestic Product. In FY 2005, NASA received 0.13 percent of GDP.
Readers interested in the development of lunar resources should consult Course Notes prepared by a University of Wisconsin team that includes Apollo 17 Astronaut Jack Schmitt.