Tethered artificial gravity system requires two objects swinging around a mutual center of gravity. For Mars Direct, the Hab (on the right) is counterbalanced by the spent upper stage (on the left).
The propellant production having been successfully completed, in late 2011 two more boosters lift off the Cape and throw their forty-tonne payloads toward Mars. One of the payloads is an unmanned fuel-factory/ERV just like the one launched in 2009, the other is a habitation module carrying a crew of five, a mixture of whole food and dehydrated provisions sufficient for three years, and a pressurized methane/oxygen-powered ground rover. On the way out to Mars, artificial gravity can be provided to the crew by extending a tether between the habitat and the burnt-out booster upper stage, and spinning the assembly.
Upon arrival, the manned craft drops the tether, aero-brakes, and lands at the 2009 landing site, where a fully fueled ERV and fully characterized and beaconed landing site await it. With the help of such navigational aids, the crew should be able to land right on the spot; but if the landing is off course by tens or even hundreds of kilometers, the crew can still achieve the surface rendezvous by driving over in their rover. If they are off by thousands of kilometers, the second ERV provides a backup. However, assuming the crew lands and rendezvous as planned at site number one, the second ERV will land several hundred kilometers away to start making propellant for the early 2014 mission, which in turn will fly out with an additional ERV to open up Mars landing site number three.
Thus, every 26 months two heavy lift boosters are launched, one to land a crew, and the other to prepare a site for the next mission, for an average launch rate of just one booster per year to pursue a continuing program of Mars exploration. This is only about ten percent of the U.S. launch capability, and is clearly affordable. In effect, this "live off the land" approach removes the manned Mars mission from the realm of mega-fantasy and reduces it in practice to a task of comparable difficulty to that faced in launching the Apollo missions to the Moon.
The crew will stay on the surface for one and a half years, taking advantage of the mobility afforded by the high-powered chemically driven ground vehicles to accomplish a great deal of surface exploration. With a twelve-tonne surface fuel stockpile, they have the capability for over 24,000 kilometers worth of traverse before they leave, giving them the kind of mobility necessary to conduct a serious search for evidence of past or present life on Mars—an investigation key to revealing whether life is a phenomenon unique to Earth or general throughout the universe. Since no one has been left in orbit, the entire crew will have available to them the natural gravity and protection against cosmic rays and solar radiation afforded by the Martian environment, and thus there will not be the strong driver for a quick return to Earth that plagues alternative Mars mission plans based upon orbiting mother-ships with small landing parties. At the conclusion of their stay, the crew returns to Earth in a direct flight from the Martian surface in the ERV. As the series of missions progresses, a string of small bases is left behind on the Martian surface, opening up broad stretches of territory to human cognizance.
Such is the basic Mars Direct Plan. In 1990, when it was first put forward by a Martin Marietta team led by this author, it was viewed as too radical for NASA to consider seriously, but over the ensuing years, with the encouragement of former NASA Associate Administrator for Exploration Mike Griffin and NASA Administrator Dan Goldin, the group at Johnson Space Center in charge of designing human Mars missions decided to take a good hard look at it. They produced a detailed study of a Design Reference Mission based on the Mars Direct Plan, but scaled up about a factor of two in expedition size compared to the original concept. They then produced a cost estimate for what a Mars exploration program based upon this expanded Mars Direct Plan would cost. Their result: $50 billion, with the estimate produced by the same costing group that assigned a $400 billion price tag to the traditional cumbersome approach to human Mars exploration embodied in NASA's 1989 "90 Day Report." If scaled back to the original lean Mars Direct Plan described here, the program could probably be accomplished for $20 billion. This is a sum that the United States or Europe or Japan could easily afford. It's a small price to pay for a new world.
In essence, by taking advantage of the most obvious local resource available on Mars—its atmosphere—the plan allows us to accomplish a manned Mars mission with what amounts to a lunar-class transportation system. By eliminating any requirement to introduce a new order of technology and complexity of operations beyond those needed for lunar transportation to accomplish piloted Mars missions, the plan can reduce costs by an order of magnitude and advance the schedule for the human exploration of Mars by a generation.
Exploring Mars requires no miraculous new technologies, no orbiting spaceports, and no gigantic interplanetary space cruisers. We can establish our first small outpost on Mars within a decade. We, and not some future generation, can have the eternal honor of being the first pioneers of this new world for humanity. All that's needed is present-day technology, some nineteenth-century industrial chemistry, a solid dose of common sense, and a little bit of moxie.
But history is not a spectator sport. Things happen because people make them happen. In 1998 an international organization called the Mars Society was formed. Its goal: Make humans-to-Mars a reality. We do public outreach, political work, and private exploration initiatives of our own. The first of these projects was to establish a Mars Arctic Research Station. Despite adverse weather, a failed paradrop, and a construction crew mutiny, this simulated human Mars exploration base was successfully built in the high-Arctic polar desert on Canada's Devon Island during the summer of 2000. If you want to find out more about what we are up to, you can look us up on our Web site at www.marssociety.org. Or write to: Mars Society, Box 273, Indian Hills, CO 80454.
The cause of the new world needs all types, from poets to pilots. Whether you are a McGee or a Townsend, a Rebecca or a Gwen, Mars needs you.
Join us.
On to Mars.