February 9, 2005
Safe and Sound on the Red Planet: Part I
Every 2 years from 2001 to 2011, with the dates dictated by launch windows, another spacecraft, launched by NASA and/or NASA's international partners, is intended to visit Mars. How can astronauts best cope with the dangers to human space travel so far from home?
Astrobiology Magazine -- The National Research Council was tasked with evaluating the risks of landing humans safely to work on Mars. Their report highlights a number of unique aspects in transit to the red planet, as well as once humans step out onto the surface. In this first of two parts summarizing some key points, their report touches on the logistics of traveling to a site and then driving around the neighborhood.
Every 2 years from 2001 to 2011, with the dates dictated by launch windows, another spacecraft, launched by NASA and/or NASA's international partners, is intended to visit Mars. Some spacecraft will orbit the planet, while others will land on the Martian surface.
The NASA Mars Exploration Program Office (within the NASA headquarters Office of Space Science) has established the Mars Exploration Program/Payload Analysis Group (MEPAG), consisting of more than 110 individuals from the Mars community, with representatives from universities, research centers and organizations, industry, and international partners.
The MEPAG participants propose the objectives, investigations, and measurements needed for the eventual exploration of Mars, focusing on four principal exploration goals. These goals fall under four broad categories:
- Life determine if life ever arose on Mars.
- Climate determine the climate on Mars.
- Geology determine the evolution of the surface and interior of Mars.
- Prepare for the eventual human exploration of Mars.
While there is currently no funded human mission to Mars, nor even a baseline reference human mission, one of the goals of the MEPAG is to ensure that sufficient information is developed in a timely manner to support such a mission, once it has been funded.
What measurements must be made on Mars prior to the first human mission? These measurements would provide information about the risks to humans so that NASA scientists and engineers can design systems that will protect astronauts on the surface of Mars.
How can robotic exploration missions sent to Mars aid NASA in assessing the risks to astronauts posed by possible environmental, chemical, and biological agents on the planet? Of critical importance is whether it will be necessary to return Martian soil and/or air-borne dust samples to Earth prior to the first human mission to Mars to assure astronaut health and safety.
Sending astronauts to the Red Planet, having them land, conduct a mission on the surface, and then return safely to Earth will be an enormous undertaking.
A long-stay mission would require that astronauts spend 16 to 20 months in orbit around Mars or on the surface, with total mission duration being 21/2 to 3 years. On a short-stay mission, astronauts would be able to remain in orbit around Mars or on the surface for only 30 to 45 days before they would have to embark on the return journey to Earth. If they stayed longer, Earth and Mars would move out of optimum alignment and the return to Earth would require an excessive amount of propellant.
Unless provisions can be made to counter the microgravity environment (by means of exercise protocols or by inducing artificial gravity) and harsh radiation conditions in space, the potential negative effects on health of the longer transit time (short-stay mission) may be prohibitive.
Once the astronauts are on the Martian surface, there are a variety of operational scenarios that could be conducted by NASA. The simplest would be that astronauts land and never leave a stationary habitat. The most complex scenario could include astronauts using large, pressurized rovers to travel long distances from a base habitat to conduct extravehicular activities (EVAs).
Even though there is no baseline mission defined for human missions to Mars, it is likely that rovers of some form will be used to perform functions critical to the safety of the astronauts. For example, human assistant rovers may carry life support equipment, while others robots, such as slow-moving scientific rovers, will likely perform mission-critical functions.
On the human missions to Mars, rovers will need capabilities far beyond what is currently planned. Human assistant rovers would have to be able to keep pace with an astronaut walking on the surface of Mars, to operate for a long time, to have an extended range, and to navigate rough terrain quickly.
These needs would be especially important for a long-stay mission, where there might be many hundreds of astronaut EVAs that would require a robotic assistant to traverse hundreds of kilometers over the course of the mission. Such human assistant rovers would require kilowatts of continuous electric power during the EVA. Compact sources of power at that capacity do not exist today.
Vehicles using standard wheels can typically roll over objects one-third the diameter of the wheel being used. This suggests that if human transport and scientific rovers will use 1-meter wheels, the mission planners will need to know the distribution of rocks one-third of a meter and larger in the landing and operation zone. Imaging rocks this size requires a pixel resolution of 10 cm.
NASA should map the three-dimensional terrain morphology of landing operation zones for human missions to characterize their features at sufficient resolution to assure safe landing and human and rover locomotion.
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