Mars has always captured the human imagination, and people have long dreamed of ways of getting there. The first technically plausible Mars exploration mission concept was Wernher von Braun’s Das Marsprojekt, or The Mars Project, developed in the early 1950s. Many mission architectures have been studied and proposed since then. In 2016, SpaceX’s Elon Musk unveiled a grand vision for Mars colonization, using the company’s Interplanetary Transport System (ITS) concept.
It’s All About Propulsion
A critical factor in getting people to Mars is speed. Humans need to get there as fast as possible to streamline mission logistics and minimize exposure to hazards along the way. In the near term, conventional chemical rocket propulsion can reasonably get the job done. NASA is planning to get us to Mars in the 2030s using an architecture based on the Space Launch System and Orion crewed spacecraft, both currently in development. But some consider chemical propulsion too slow and inefficient, advocating instead the use of more exotic rocket propulsion methods such as nuclear thermal rockets and various types of ion thrusters (which powered the fictional Hermes spacecraft in Andy Weir’s novel, “The Martian”). These and many other propulsion concepts are being studied but will require further development before they are mature propulsion-technology options for human spaceflight.
To achieve the goal of colonization, unlike with previous lunar missions, it is essential to think in terms of building a sustainable transportation architecture. The Apollo program was much like an X-plane project, designed to achieve the lunar landing goal, but not to establish a reliable and enduring transportation infrastructure.
We can’t afford to do that with Mars. Realistic Mars exploration and colonization plans must go beyond the transportation problem, and they have evolved to keep pace with technological developments. Early plans assumed everything needed would be carried to Mars from Earth, which doesn’t make practical or economic sense. Mission plans such as Mars Direct, an influential plan developed by Dr. Robert Zubrin in the 1990s, pioneered the idea of in-situ resource utilization or living off the land. This idea has matured with evolving Mars exploration plans, incorporating recent technological advances such as 3-D printing, which could be used to meet needs such as base/habitat construction and spare-part fabrication.
Radiation, Gravity and Human Survival
Despite the human experience in space to date, the long-term biological effects of radiation and reduced gravity exposure are largely unknown. Astronaut Scott Kelly recently spent a year on the ISS, and by running tests comparing him to his twin brother on returning to Earth, he provided invaluable data on human health in a microgravity environment.
But humans have never spent a significant amount of time in a reduced-gravity field. The surface gravity on Mars is only about 38 percent of Earth’s gravity, and the long-term effects of living in such an environment are unknown. The ISS is largely protected from cosmic radiation by the Earth’s magnetosphere, a luxury that will not be afforded to Mars-bound travelers and colonists. Various radiation-shielding techniques are being explored and will require considerable development to provide adequate protection for long-duration human spaceflight.
Given the difficulty, expense and long duration of travel between Earth and Mars, the successful human colonization of Mars will require the creation of an independent self-sustaining biosphere. This is something that has yet to be demonstrated even on Earth. The Biosphere 2 project attempted to do this in the 1990s and failed. NASA conducts a variety of analog missions on Earth to address these challenges facing future Mars colonists.
The Human–Robotic Partnership
The ultimate success of human Mars exploration and colonization still depends on learning more about the red planet through robotic precursor missions. NASA’s robotic Mars program has been spectacularly successful, but the existing Mars fleet is aging. New missions such as the Mars 2020 Rover are in the pipeline to replace them. A number of companies — including Northrop Grumman, the prime contractor for NASA’s James Webb Space Telescope — are conducting concept studies for a potential future Mars orbiter mission. When humans are finally on their way to Mars, the human–robotic partnership will continue to play an important role. In addition to the direct support of human exploration, robot systems will be essential to the future Martian technological infrastructure, such as planetary communications and a GPS-like navigation network.