Why go to Mars?
NASA’s vision statement is inspiring: “To reach for new heights and reveal the unknown, so that what we do and learn will benefit all mankind.” The drive to explore embodies a very human desire that drives us to want to venture into the unknown, to find what is beyond the next hill and understand it. This drive is life-affirming. Some hypothesize that a variant of a gene called DRD4-7R drives our curiosity and generates the desire to explore and take risks along with the imagination and ingenuity to successfully achieve these desires.
All civilizations seek to achieve greatness and build monuments to be left to subsequent generations as high-water marks of their value. This desire has left us with the Pyramids, the Great Wall, the Panama Canal, the Parthenon, the steam engine, railroads, skyscrapers, the automobile and airplane, and even cave paintings. Each wonder, each innovation, says that its people were here with their hearts, minds and hands. Great achievements advance the human condition and establish markers of important technical advances.
We are no different today. Over the last 60 years we have broken free of the gravitational bonds that have anchored us to planet Earth. Our satellites have visited all the planets, asteroids and some comets too. And though we have achieved many exciting innovations since the moment a flag was planted on the Moon over 40 years ago, the Apollo landing remains the pinnacle of our achievement.
Going to Mars will be no small task
There are enormous affordability issues associated with conducting any Mars mission, whether manned or unmanned. Mission planners for manned voyages must craft a means to safely send and return astronauts while confronting the usual array of potential life-threatening failure scenarios of spacecraft systems. The logistics footprint for the spacecraft and crew must be sized just right — consumables must be brought aboard the spacecraft, stored and transported, shepherded precisely by the crew as it travels to and from the red planet, and must operate and survive extremely long-term exposure to hazardous and unforgiving space environmental factors:
- Radiation can cause cell death and mutation.
- Microgravity and weightlessness can cause health problems including bone loss of 1 percent per month; fainting spells after re-entering the gravitational field; cognitive problems, including Alzheimer’s-like symptoms; loss of muscle mass and muscle atrophy; inability to retain proper blood pressure in readapting to gravity; and cardiovascular effects, such as arrhythmia and atrophy.
- Isolation can have negative effects.
We need to find ways to reduce the time it takes to get to Mars to reduce these exposures and minimize their effects on the human body. Mars requires less energy per unit mass (propulsion) to reach from Earth than any planet except Venus. Using a Hohmann transfer, a trip to Mars would require approximately nine months. Modified transfer trajectories can be used to cut the travel time down to seven or even six months. These trajectories are made possible by using incrementally higher amounts of energy and fuel. Modified trajectories are now the standard means for sending robotic rovers to Mars for scientific missions.
Shattering the travel time to Mars to less than six months would require exponentially increasing amounts of propellant, and as a result total system weight would need to increase. Sadly, these increased weight requirements are mission breakers, as they are not feasible with today’s chemical rocket technology.
Travel in less than six months could be achieved with advanced spacecraft propulsion technologies. These technologies have the potential to cut the trip times down to about 60 to 90 days at close approaches. Use of a nuclear fusion approach that emits little radiation from the spacecraft propulsion system could enable Earth-Mars planetary transits of less than 60 days. Of course, such fusion-enhanced vehicles would demand the construction and use of large spacecraft given the systems needed to make them operate. The resulting vehicle could be bigger than the international space station, which totals about 400 metric tons.
Constant-acceleration propulsion techniques such as solar sails or ion drives could also present tremendous opportunities. Such propulsion subsystems could permit passage times from Earth to Mars at close approaches on the order of several weeks to a few months. While these technologies look feasible, they are limited in terms of the power per unit area and power per unit mass to make them effective for human transit. Their use would be best optimized for an efficient use of propellant (or, in the event that there is no propellant, with a solar sail) for cargo or prepositioning resource missions.
Once the crew gets to Mars orbit, it still needs to get down on to the planet. Entry, descent and landing is complicated and presents an immense technical challenge. The Jet Propulsion Laboratory (JPL) has spent many years and has learned from early failures using its best minds to achieve success on entry, descent and landing, and given its unique experience I expect that any successful mission to attempt travel to Mars will inevitably involve JPL’s problem solvers.
When the crew gets to the surface, it must be equipped to survive. Humans have already explored natural settings on Earth that match most conditions on Mars. For example, the highest altitude reached by a manned balloon ascent, a record set in the recent Red Bull challenge, is 38,969 meters. The pressure at that altitude is about the same as it is on the surface of Mars. And the extremes of cold in the Arctic and Antarctic match all but the most extreme temperatures on Mars. The truth is, however, that Mars is basically a deadly place for humans. The atmosphere is 95 percent carbon dioxide, and there is almost no oxygen.
Fortunately, the martian environment poses some interesting pluses:
- Mars’ gravity is 38 percent of Earth’s.
- With an axial tilt, Mars has seasons.
- Mars has an atmosphere, though it is only 0.7 percent of Earth’s. That would provide some measure of protection from solar and cosmic radiation.
- There are no standing bodies of water on Mars but it has water ice.
And finally, the crew must leave the surface and return home as quickly and safely as possible to minimize exposure risks. With even the minimal gravity on Mars, it still is far more difficult to get off the surface than it was to get off the surface of the Moon. Mars missions could be enhanced if dependable fuel sources can be located on the planet. That would drive a solution on how much fuel the space vehicle would have to carry. While some have proposed a one-way trip to Mars, it is not likely that governments would participate in such ventures.
Colonizing Mars would pose daunting challenges, so attempting colonization should not be a first step. As with the early Moon excursions, we first should go to Mars, orbit it and return safely to Earth. Once we are confident that return can be achieved on a regular basis, the next step should be to send people there, to land on Mars to assess and explore, and bring them back safely to Earth. Next, we need to have visitors begin to build sustainable infrastructure on the planet and return. Finally, and only then, when infrastructure is in place, should we even think of colonizing Mars.
Getting a human on the surface of Mars should be a U.S. national goal. The value we would get from such an endeavor would far exceed the fruits of the accomplishment itself. We would inspire a generation and build a deep technical infrastructure that would last for years, and, like the Apollo generation, this would provide the fuel to grow other parts of our society. Yes, we need to fix the economy and solve the myriad of earthbound challenges we have, but we should also start a conversation about going to Mars as a global endeavor since it is not likely the Unites States, or any single nation, will be able to afford this alone. This does not need a huge commitment at first. We should start by addressing the technical challenges, so NASA needs to find seed money to start defining the solutions to these difficult problems.
Assuming Congress and the Obama administration were to agree to embark on a Mars mission, the mission still would have to be sustained through successive Congresses and administrations. However, NASA and elected leadership changes with time, and as a result space agenda priorities have whipsawed so that nothing save for the robotic missions have stayed on course. We need to find a way to keep a constant vision through leadership changes.
Finally, we need to make sure that we don’t make going to Mars the end of our hopes, as happened at the end of the Moon race. The human spirit needs whatever the next challenge will be reaching out higher and farther. What we leave behind will serve as our monuments to be left to subsequent generations.
Thomas D. Taverney is senior vice president at SAIC and a former vice commander of U.S. Air Force Space Command. He submitted this article as an individual.
