MARS DIRECT (c) Robert Zubrin & Chris McKay Here's how the Mars Direct plan works. At an early launch opportunity - 1999, for example - a single heavy lift booster with a capacity equal to that of the Saturn 5 used during the Apollo program is launched off Cape Canaveral. It uses an upper stage to throw a 40 tonne automated payload onto a trajectory to Mars. Arriving at Mars eight months later, the payload vehicle aerobrakes into orbit around Mars, and then lands with the help of a parachute. This payload is the Earth Return Vehicle (ERV). It flys out to Mars with its two methane/oxygen propulsion stages unfueled. In addition, it carries six tonnes of liquid hydrogen cargo, a 100 kilowatt nuclear-reactor mounted in the back of a methane/oxygen-driven light truck, a small set of compressors along with an automated chemical processing unit, and a few small scientific rovers. On landing the truck is telerobotically driven a few hundred meters away from the site, and the reactor is deployed to provide power to the compressors and chemical processing unit. The hydrogen brought from Earth can be quickly reacted with the Martian atmosphere, which is 95 percent carbon dioxide (CO2) gas, to produce methane and water. This eliminates the need for long term storage of cyrogenic hydrogen on the planet's surface. The methane so produced is liquefied and stored, while the water is electrolysed to produce oxygen, which is stored, and hydrogen, which is recycled through the methanator. Ultimately these two reactions (methanation and water electrolysis) produce 24 tonnes of methane and 48 tonnes of oxygen. Since this is not enough oxygen to burn the methane at its optimal mixture ratio, an additional 36 tonnes of oxygen is produced via direct disassociation of Martian carbon dioxide. The entire process takes ten months, at the conclusion of which a total of 108 tonnes of methane/oxygen bipropellant will have been generated. This represents a leverage of 18 to 1 of Martian propellant produced compared to the hydrogen brought from Earth needed to create it. The ERV requires 96 tonnes of the bipropellant for fueling, leaving 12 tonnes available to support the use of high powered chemically fueled, long range ground vehicles. Large additional stockpiles of oxygen can also be produced, both for breathing and for turning into water by combination with hydrogen brought from Earth. Since water is 89% oxygen (by weight), and since the larger part of most foodstuffs is water, this greatly reduces the amount of life support consumables that need to be hauled from Earth. In 2001, following the successful completion of the vital propellant production on Mars, two more boosters lift off the Cape and throw their 40 tonne payloads towards Mars. One of the payloads is a fuel-factory/ERV, just like the one launched in 1999. The other is a habitation module containing a crew of four, a mixture of whole food and dehydrated provisions sufficient for three years and a pressurized methane/oxygen ground rover. On the way out to Mars, artificial gravity can be provided to the crew by extending a tether from the habitat to the burnt-out booster's upper stage, and spinning the assembly. Upon arrival, the crew's craft drops the tether, areobrakes and lands at the 1999 landing site where a fully fueled ERV and fully characterized and beaconed landing site await it. With the help of such navigation aids, the crew should be able to land right on the spot. But, even 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 landing and rendezvous at site number one is successful, the second ERV will land several hundred kilometers away to start making propellant for a 2003 mission, which in turn, will fly out with the additional ERV to open up Mars landing site number three. Thus, every other year two heavy lift boosters are launched, one to land a crew, and the other to prepare a site for the next mission. WITH AN AVERAGE LAUNCH RATE OF JUST ONE BOOSTER PER YEAR, WE CAN PURSUE A CONTINUING PROGRAM OF MARS EXPLORATION. This is only about 10 percent of the U.S. launch capability, and is clearly affordable. In effect, the dog sled approach removes this dogsled approach removes the human Mars mission from the realm of mega-fantasy and reduces it to practice as a task of comparable difficulty to that faced in launching Apollo missions to the Moon. The crew will stay on the surface for one-and-one-half years. Unlike conventional Mars mission plans based upon orbiting motherships with small landing parties, no-one has been left in orbit, vulnerable to the hazards of cosmic rays and zero-gravity living. Instead, the entire crew will have available to them the natural gravity and protection against cosmic and solar radiation afforded by the Martian environment, so there is no strong motive for a quick departure. The mobility afforded by the ground vehicles will allow the crew to accomplish a great deal of surface exploration. With a 12 tonne surface fuel stockpile, they have the capability for more than 25,500 kilometers traverse before they leave. At the conclusion of their stay, the crew return 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 for human exploration. Such is the basic Mars Direct plan. By taking advantage of the most obvious local resource available on Mars - its atmosphere - the plan allows us to accomplish a human 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 the cost of the Space Exploration Initiative by an order of magnitude and advance the schedule for the human exploration of Mars by a generation. Purists may object that Mars Direct doesn't go completely native. After all, the plan brings the reactor's energy, the ERV's hydrogen and part of the crew's food from Earth. On the other hand, while Amundsen may have lived of caribou and travelled by dogsled, he did his hunting with modern rifles and brought skies (a uniquely Norwegian innovation) along too. Its necessary to be practical. Utilization of Martian resources beyond the freely available carbon dioxide "caribou" will come in the course of larger scale bases and settlements.