Scientists have explored the possibility of a manned mission to Mars since 1952, with successful orbital and rover missions providing better understanding of conditions. However, the challenges of a long journey, psychological tolerance, cosmic ray exposure, and payload weight reduction must be overcome. There are currently no solid plans for a manned mission to Mars in the near future, but it may happen by 2037.
Scientists have seriously explored the possibility of a trip to Mars since at least 1952, when Wernher von Braun published his influential book Das Marsprojekt. Since then, there have been several highly successful orbital and rover missions, allowing reconnaissance of Mars and a much better understanding of conditions there, paving the way for a potential manned mission.
At the same time, the success of probe missions has led some scientists to question the wisdom of a dangerous and costly manned mission. In any case, there are currently no solid plans for a manned mission to Mars in the near future, although the US Vision for Space Exploration mentions the possibility of travel to Mars after 2020. In this article we look at some of the issues facing they may need to be addressed before travel to Mars is feasible.
Mars’ distance from Earth ranges from 36 million miles to over 250 million miles, the greatest variation in distance Earth has to any planet. The average distance is about 140 million miles, 1.5 times longer than the distance between Earth and the Sun. About every two years, Earth gets relatively close to Mars, about 50 million miles. By comparison, the distance from Earth to the Moon is only about 236,000 miles (380,000 km), over 200 times shorter. If the journey from Earth to the Moon takes about three days, then a spacecraft of similar speed traveling to Mars would take at least 600 days (1.6 years). This transit time is typical of space probes launched to Mars so far.
Spending more than three years with a small crew – probably just three or four, in a cramped spacecraft – can push the limits of human psychological tolerance. This surpasses the isolation experienced by nuclear submarines, which can spend months underwater in cramped quarters, but not years. To make this situation more tolerable, the astronauts would need some form of entertainment to make the journey without killing each other. Internet access is one possibility (although there would be a significant delay due to long distances) and virtual reality programs are another. To travel to Mars in a realistic way, this challenge must be overcome.
Another major concern with the trip to Mars is the level of cosmic ray exposure for such a long mission. However, a few adverse health effects from stays of a year or more on low-Earth orbit space stations indicate that this may not be as serious a problem as originally thought.
Because the journey is so long, any manned mission to Mars would require a significant amount of food and water on board and an efficient means of recycling the water after it has passed through the body. Otherwise, the vessel’s payload would be prohibitively expensive. A Martian spacecraft would not only need to carry its passengers, their equipment, food, oxygen and water, but the fuel needed to launch from Mars and accelerate back to Earth on the return journey. This leads to unprecedented weight requirements significantly beyond anything attempted in space missions thus far.
If all the technical challenges can be overcome, humans will eventually visit Mars. The use of nuclear-powered spacecraft would be one approach to the challenge of propulsion and payload weight reduction. However, it could be a while before astronauts travel to Mars: one clue suggested a date of 2037.
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