The Case for Mars, page 10
All this came to pass, and more, because what I didn’t know at the time was that Griffin liked Mars Direct so much that he proceeded to brief it to incoming NASA administrator Dan Goldin, who also became a supporter. The bottom line was that when I showed up at JSC in October 1992 for a series of detailed briefings on Mars Direct, people were definitely prepared to listen.
The exploration program group at JSC listened, and they liked what they heard, but they still had concerns. They felt that my estimates of mission mass were on the light side, and they wanted a crew of six, so a more powerful booster than the Ares would be needed. Dave Weaver, the lead mission architect in the group, was also leery about making the whole mission architecture critically dependent upon Mars-based production of propellant. True, it was made before the crew that would need it left Earth, so no one would be stranded, but if the propellant production failed, the program would still be a failure. Weaver and I went into his office and got out the chalk and worked out a compromise mission architecture that answered his concerns.8 I call this plan “Mars Semi-Direct” (Figure 3.2). Instead of two launches per mission there would be three, one delivering a self-fueling Mars ascent vehicle to the surface together with a lot of equipment and supplies, one delivering an Earth return crew cabin together with a methane/oxygen chemical propulsion stage to a high orbit about Mars, and a final launch delivering a hab with the crew to the Martian surface. Now, instead of having to make enough propellant to send an Earth return vehicle directly from the Martian surface to Earth, all that would be needed would be enough to send the Mars ascent vehicle from the srface to rendezvous with the crew cabin in orbit, after which the orbiting chemical stage would push the crew the rest of the way home. The Mars ascent vehicle is light enough that if no extra cargo is sent with it, a fully fueled version could delivered to the Martian surface with a single heavy lift booster launch. Thus if insitu propellant manufacturing should fail, the program could still be saved with the aid of a fourth booster launch. I didn’t like this architecture as much as the classic Mars Direct, because limiting the application of Martian propellant production also limits its benefits. Instead of Mars Direct’s two launches and two spacecraft per mission, three of each would be required by the Mars Semi-Direct plan, and the extra launches and vehicles would make it more expensive. Furthermore, a mission-critical Mars orbit rendezvous had been introduced on the return leg. But it was clearly an extraordinary advance over previous NASA thinking, with all payloads being delivered to Mars with direct throw of the booster, no on-orbit assembly of mega-spacecraft, and long duration surface stays and use of in-situ resources starting on the very first mission. It was a compromise, but a viable one, a plan I could support. Mike Duke and Humbolt “Hum” Mandell, two relatively senior personalities at JSC, also became early and strong advocates of the Mars Semi-Direct plan, and support within JSC solidified rapidly thereafter.
In 1993, Weaver pulled together a large cross-NASA team to undertake an elaborate design study of the Mars Semi-Direct plan. I participated in this study as an advisor. Once again, with the large team in play, centrifugal tendencies were evident. Representatives of various programs tried to skew things to ensure a leading role for their systems. In dealing with this large team, Weaver was basically in the position of someone trying to herd cats. Nevertheless, the team developed a workable, if bloated, plan based on Mars Semi-Direct. This expanded version of the Mars Semi-Direct plan was then subjected to a cost analysis by the same JSC costing group that had developed the $450 billion estimate for the 90-Day Report. The analysis incorporated the development of all required technology, including the large booster (i.e., no sharing of the cost of that system’s development with a lunar exploration program was assumed), and flying three complete human missions to Mars. The bottom line: $55 billion, or one-eighth the cost of the traditional plan. In July 1994, word of this work reached Newsweek magazine and made the cover. “A manned mission to Mars?” Newsweek asked. “The technology is already in place. And at $50 billion—one-tenth of previous estimates—it’s a bargain.”
FIGURE 3.2
Mission Sequence for the Mars Semi-Direct plan. Every two years, three boosters are launched. One to deliver a crew to Mars in the hab, the others to deliver unmanned payloads consisting of a self-fueling Mars ascent vehicle (MAV) and an Earth return vehicle (ERV). When it’s time to return home, the crew transfers to the MAV and rides it to a rendezvous with the orbiting ERV, which then carries the crew to Earth. The Year 1 hab is flown to Mars without a crew, creating a reserve hab for the first piloted flight, which arrives at Mars in the Year 3 hab.
Among those who have studied the problem, there is now a consensus that an affordable, technologically do-able, politically supportable plan exists that can get humans to Mars—one with the Mars Direct concept as its basis. This is not a program for some distant future generation, but for us. It is a mission that can be designed by the engineers of today and flown by people who ar in the astronaut corps, today.
In the following chapters we’ll take a closer look at the Mars Direct plan, and see how it works, step by step and piece by piece. And what it holds not only for sending humans to Mars, but for exploration, human settlement—and even transformation of the Red Planet itself.
* * *
FOCUS SECTION—THE MARS UNDERGROUND
Sometimes a small group of individuals can shout loud enough to be heard above the din, and that’s certainly true in the case for Mars.
In the decade following the Apollo program, plans for the human exploration of Mars essentially dropped off NASA’s horizon as the agency struggled to get the Space Shuttle up and flying. Manned Mars exploration studies within the agency were virtually unheard of, but commencing in the early 1980s, the notion of sending humans to Mars started wafting through the space community due to the efforts of a small band of Mars enthusiasts who, in short order, became known as the Mars Underground. To understand where the underground began, we have to go back to 1978, the sleepy interstitial period between Skylab and the Space Shuttle. The last Apollo voyage, Apollo 18, flew in July 1975, and then not to the Moon but to low Earth orbit to dock with Russian counterparts. Previous to Apollo 18, no American had flown into space since Skylab 4, in November 1973. The Voyagers, due to inspect the gas giants at the far edge of the celestial neighborhood, had been launched the previous year. Pioneer-Venus 1 and 2 had winged off to Venus and would reach the planet at year’s end. The shuttle would not fly until April 1981. All in all, it was a fairly sleepy time in the space community, a time when fertile minds look around for something mischievous to do, like reengineering a planet. So it was that Chris McKay, then a graduate student in astrogeophysics at the University of Colorado, started up a seminar on terraforming Mars.
The seminar arose out of hallway discussions and graduate student lounge beer and bull sessions prompted by the Vikings’ dismal but intriguing findings. Mars appeared lifeless, according to Viking, but it also appeared that Mars needn’t remain that way—a bit of wisely applied planetary engineering, terraforming, could bring Mars back to the future as, once again, a warm, wet planet. Joining McKay were Carol Stoker, a fellow astrogeophysics graduate student; Penelope Boston, an undergraduate biology major and long-time friend of McKay’s; Tom Meyer, president of his own engineering firm and a friend of Stoker’s from years past; computer scientist Steve Welch; and a gaggle of others, perhaps twenty-five in all. Charles Barth, the director of the Laboratory for Atmospheric and Space Physics at the University of Colorado, acted as mentor and counselor to the group, helping them transform informal conversations into a formal seminar on “The Habitability of Mars.”
Over the course of the first semester, the seminar’s participants, with some gentle nudges from Barth, recognized that terraforming Mars was a tall order, even for graduate students. They also realized that they were theory-rich and data-poor. While entertaining and intriguing perhaps, discussions of terraforming Mars without more data would really lead nowhere. They needed more information about Mars—its present atmosphere, its past atmosphere, volatiles, resources, a multitude of items—data that human missions could collect. So, the group began to focus on near-term human missions to Mars, and eventually wrote up their findings as “The Preliminary Report of the Mars Study Group.” Barth shephernowhere. Tthe report to NASA headquarters and word soon got out that a band of graduate students and others out in Boulder were enthusiastically—and intelligently—investigating human missions to Mars as well as a new science known as terraforming, more about which to come. Some of the seminar’s members scraped money together and piled into cars for cross-country drives to various space science conferences and meetings where they would occasionally bump into others of their own “flavor,” individuals who were entranced by the Boulder group’s enthusiasm, vision, and intelligence.
During the spring of 1980, McKay and Boston crossed paths with Leonard David at an American Astronautical Society meeting in Washington, D.C. David had spent the past few years arranging student forums on space exploration and had heard about the Boulder crew. The three hit it off fairly quickly and what started as a chat about Mars exploration ended with David suggesting that some effort ought to be made to hold a conference on human Mars exploration. This was something of a novel idea, as twenty-something graduate students usually didn’t organize and host planetary exploration conferences, but adopting something of a “Why not?” attitude (they really didn’t have anything to lose), a cluster of Mars devotees, began some low-key planning. McKay, Boston, Welch, Meyer, Stoker, and Roger Wilson, another University of Colorado student, started working on a list of possible topics to be addressed and possible speakers. Via some graduate student guerrilla methods, they ran off a hundred or so copies of a conference announcement and bundled them off for distribution. Much to everyone’s surprise, calls started coming in, both from those who wanted to attend and from researchers interested in delivering papers. Deriving the forum’s name from a seminal article entitled “The Case for Humans on Mars” that Viking scientist Ben Clark had written in 1978, in late April, 1981, the Boulder group hosted the first “Case for Mars” conference.
It was a small conference—just one hundred or so people eventually attended—but to the organizers, these were legions. Before the conference, the Colorado group felt more or less alone in the wilderness. There were not many, they thought, who had the interest and know-how to undertake a serious study of humans-to-Mars missions. But now here they were, in the midst of their conference with presentations on resource utilization, life support on the Martian surface, propulsion options. It was heartening, thrilling, indeed liberating to know that there were others who shared their passion. Leonard David had arrived from Washington with a bundle of red buttons. Imprinted on the buttons, below a Case for Mars logo (depicting a DaVinci-style human figure inside the ancient astrological symbol for Mars), were the words “Mars Underground.” A short note accompanied each button, stating that the wearer was now a member of the “Mars Underground,” an ad hoc collective of Mars aficionados (“tightly knit but loosely woven”), and that the button should be worn discreetly, under the lapel, or perhaps inside the coat. Over the course of four days, numerous workshops, and a slew of presentations, the Mars Underground formulated plans for the human exploration of Mars: the whys and wherefores of the program; precursor missions to the human missions; mission profiles; and rosters of surface activities for explorers. Not a bad result from a conference conceived and organized by a bunch of graduate students.
The conferences have continued, one every three years, each building on what preceded and reflecting the character of the times. The second conference, in 1984, resulted in a complete end-to-end design for a Mars mission that d.& members used as the basis for a two-hour presentation on Mars exploration they delivered at NASA headquarters and other NASA centers. The 1984 conference was also notable in that it drew to the group people of greater political influence, such as former NASA administrator Thomas Paine. In 1985, President Reagan appointed Paine to head the blue-ribbon National Commission on Space, who then proceeded to guide it to a recommendation that the United States make the establishment of a human outpost on Mars the thirty-year goal of the space program. The White House responded to the report by setting up the “Code Z” organization and “Pathfinder” programs at NASA headquarters, to respectively plan mission strategies and develop the key technologies required for human expansion to the Moon and Mars. It was these organizations that formed the insider network which provided the policy input for Bush’s call for a Space Exploration Initiative in July 1989.
The third Case for Mars conference accelerated the trend, with Carl Sagan giving the keynote address to an audience of over a thousand people, including a substantial representation of the international press. I had first heard about the Mars Underground after Case for Mars II, and along with more than four hundred other out-of-town technical types, went to Case for Mars III to participate in some of the nearly two hundred presentations and sixteen workshops. The two-volume set of papers arising out of Case for Mars III outlines strategies for Mars exploration that touch upon both the technical requirements as well as public policy and political requirements for transforming the vision into a reality. By the fourth conference in 1990 (and held, as always, in Boulder) what had a decade earlier been nearly verboten to speak of in NASA—humans to Mars—had become the current president’s stated long-term goal in space. Carol Stoker, who was in charge of the conference scheduling, had attended a private Mars Direct pitch at NASA’s Ames Research Center in California, and liked the plan. She gave the bully pulpit at the opening plenary session to David Baker and me to present Mars Direct to the assembled Mars Underground. The next day, news that a low-cost manned Mars mission plan was now on the table appeared in the Boston Globe and dozens of syndicated papers.
Mapping the trajectory of a spacecraft is a relatively straightforward business, bounded only by the laws of physics. Mapping the trajectory of an idea through a political system, on the other hand, can be a dicey business. There were many reasons why George Bush stood on the Air and Space Museum’s steps in 1989 and declared Mars to be a necessary destination for human exploration, but I have no doubt that the Case for Mars conferences and the small group of individuals who form the core of the Mars Underground were instrumental in positioning a human journey to Mars as an attainable, realistic goal for the United States space program. The conferences provided the cauldron for a brew of ideas, all of which served to heighten the profile of human missions to Mars and all of which energized the community of Mars researchers and enthusiasts. For an organization where membership is defined by enthusiasm and effort rather than a spot on a membership roll or a card carried in a wallet, the Mars Underground and the Case for Mars conferences have to be credited with having influence far beyond their modest size.
It is in honor of their efforts that I have chosen the title of this book.
4: GETTING THERE
FAST MISSIONS AND GOOD MISSIONS
In planning a long journey, you firs choose a route and a mode of transportation. So it is with Mars.
Many believe a voyage to Mars is impossible because the Red Planet is so far away from Earth. Until such time as radically more advanced types of space propulsion become available, they argue, the trip will simply take too long. Let’s take a look at this objection.
Mars is indeed far away. At its closest approach, when it stands directly on the opposite side of the Earth from the Sun (a condition that ancient astrologers, with their geocentric world view, described as an “opposition,” of which more anon) it never gets nearer than 56 million kilometers, or 38 million miles. At its farthest, when it stands behind the Sun as seen from the Earth (what the ancient astrologers called a “conjunction”), it lies about 400 million kilometers distant. (See Figure 4.1.) Now, no propulsion system is even on the drawing boards that can push directly away from the Sun and perform the transit between Earth and Mars in a straight line when the two are in opposition. This is because a spacecraft leaving Earth possesses the velocity of the Earth, some 30 kilometers per second (km/s), and thus, unless massive amounts of propellant are expended to alter course, the spacecraft will continue to circle the Sun in the same direction as the Earth. In fact, as the German mathematician W. Hohmann discovered in 1925, if you want to go easy on the gas, the best time to travel from Earth to Mars occurs when the two planets are in conjunction; at their maximum distance from each other on opposite sides of the Sun. (See Figure 4.2.) This is the easiest way to go, because if you take this path you can travel along an ellipse which is tangent to the Earth’s orbit at one end, and tangent to Mars’ orbit at the other, thus minimizing the course change which is required for the spacecraft to depart or rendezvous with each. You can deviate from such a flight plan if you wish, but the more you do, the harder your propulsion job, and the costlier your mission. But even if you do decide to pour on some extra gas to cut corners and avoid the full Hohmann transfer, roughly speaking you’ll likely need to traverse at least 400 million kilometers along some curving arc to get from Earth to Mars. Four hundred million kilometers. That’s a lot. In contrast, the Earth’s Moon is “only” 400,000 kilometers away. So to get to Mars, you’ll have to travel a thousand times farther than the Apollo astronauts did when they voyaged to the Moon. It took three days for the Apollo spacecraft to make a one-way lunar transit. Will it take 3,000 days, eight years, to reach Mars?
