Earlier this month, NASA released a road map outlining how it will approach the historic mission aimed at sending mankind to Mars. Join us as we take an in-depth look at the plan, and the technological challenges that must be overcome if the agency is to undertake humanity's next step in its race to the stars.

At first glance, the incremental road map could be mistaken as overly cautious in nature, but we have to take a step back and view the endeavor through a wider scope. As a species we only (relatively) recently achieved the power of flight. Since then advances in aviation and then aerospace have occurred at an astonishing rate, leading to us placing men on the Moon and finally establishing a long-term presence in low-Earth orbit (LEO).

The problem is, putting a man on the Moon is nothing like extending the domain of human spaceflight to another planet. As it stands, we are aware of countless trials and technological hurdles that must be overcome, but the true challenges are the unknowns that will inevitably rear their ugly heads as we walk down the difficult path ahead.

Infographic outlining NASA's roadmap to Mars(Credit: NASA)

Technological difficulties aside, the agency must keep the astronauts healthy, and assess the behavioral and psychological effects such a journey would have on the crew. One of the key mental aspects for the crew will be dealing with the extreme isolation from Earth in a confined space, in the knowledge that should the worst happen, there is no abort option, and the nearest help is millions of miles away.

With this in mind NASA's newly-released road map heavily emphasize independence, reliability, in-situ use of resources and automation as a means of mitigating the risks of a manned mission, and its reliance on the home world. NASA has split its road map into three distinct phases – Earth Reliant, Proving Ground, and Earth Independent.

Earth Reliant

The first leg of NASA's journey has already been operational for nearly 15 years. The moment that mankind sent astronauts and cosmonauts to the ISS back in November 2000, we began the incremental process of learning how to keep human beings alive in space for prolonged periods of time. This is the key element to the agency's Earth Reliant phase, which will unfold aboard the ISS.

Man's time in LEO has taught us that we require effective exercise regimes, drugs and equipment to prevent muscle and bone wastage, as well as a myriad of other unpleasant side effects synonymous with operating beyond Earth's nurturing atmosphere.

The ongoing year long mission of Scott Kelly and Mikhail Kornienko in LEO will significantly advance our relatively infantile knowledge regarding the effects of microgravity on the human body and mind. This line of research is vitally important to improving the resilience of astronauts for a mission to Mars that could last as long as 1,100 Earth-days.

Beside the crew health aspect of the Earth Reliant phase, NASA is testing and developing a wide variety of components for the later, more ambitious phases of the journey to Mars. The agency plans to utilize the space station's unique microgravity environment to advance radiation shielding technology, in-situ 3D printing of tools, the capabilities of the next generation of EVA spacesuit, and many other elements necessary to reduce Earth reliance.

Proving Ground – cislunar space

Early in the next decade, NASA, as part of an international effort, plans to extend its operations to cislunar space – an orbital region around the Moon that represents the ideal proving and staging ground for a deep space mission. Here NASA can field test elements of a Mars mission in the knowledge that it would take mere days to return a crew to Earth in the event of an emergency.

Transportation and habitation are at the top of NASA's list of priorities for operations in cislunar space. The agency will assess the performance of its next generation Orion spacecraft and Space Launch System (SLS). Unlike commercial crewed spacecraft, such as Space X's Crew Dragon and Boeing's Starliner, Orion is being developed with the sole purpose of operating beyond LEO.

Over the course of the Proving Ground section of the journey to Mars, Orion will be responsible for keeping the crew safe during launch, transporting them to a long term orbital habitat in cislunar space, and finally protecting the astronauts from the intense heat of re-entry.

The launch stage for operations in cislunar space will be powered by the first iteration of the SLS, known as Block 1. NASA plans to roll out two upgrades to the SLS – Block 1B and Block 2, the latter representing the most powerful launch vehicle constructed so far, with a maximum thrust 20 percent greater than that of the Saturn V rocket that first launched mankind to the Moon.

Block 1 of the SLS recently completed its Critical Design Review, a vital stage in the design process before proceeding to full-scale production. The first outing of Orion and the SLS is currently slated for 2018, although this is subject to delay.

While operating in cislunar space, NASA hopes to develop and test a cutting edge Solar Electric Propulsion (SEP) system geared toward the efficient transportation of habitat and cargo spacecraft between Earth and the Red Planet. The tech would differ considerably from most conventional space exploration thrusters, utilizing solar power to accelerate ionized propellant in order to create thrust.

The resulting engine would be incredibly low powered, but capable of running for months or even years at a time, gradually picking up speed. Furthermore the fuel required to power the SEP thrusters, known as xenon, takes up only 50 percent of the mass for the equivalent fuel of a chemical engine, allowing for significant savings on launch mass that could then be devoted to equipment and supplies.

Artist impression of a Solar Electric Propulsion (SEP) system in action(Credit: Analytical Mechanics Associates)

NASA plans to utilize an advanced version of the system to pre-place resources, landers, habitats and more conventionally-powered Mars ascent vehicles (MAV) on the Red Planet years ahead of a manned mission. The agency asserts that the thrusters could be reused on further missions after refueling, thus creating a more sustainable deep-space presence.

NASA is also considering the potential of utilizing a hybrid spacecraft boasting both SEP and chemical thrusters. Such a spacecraft would begin its journey to Mars from a lunar distant retrograde orbit, using thrust from the upper stage of an advanced SLS launcher and targeted burns from its conventional thrusters to supplement the SEP engines, with the effect of cutting down Mars transfer periods for manned missions when compared to SEP only spacecraft.

Many of the technologies pioneered by NASA during the Earth Reliant and Proving Ground phases of the roadmap will be field tested via the agency's planned Asteroid Redirect Mission (ARM), which will leverage the Orion spacecraft, an SLS launcher and SEP technology. The ARM mission, scheduled for launch in 2020, will also present the agency with an opportunity to observe the performance of next generation EVA suits, assessing how they stand up to a spacewalk and contact with the captured asteroid boulder.

In order to maintain a long-term presence in cislunar space, NASA and partners are planning to deploy an advanced habitation module. Based on technologies pioneered aboard the ISS, the modular habitat will allow NASA to mature environmental systems designed to keep astronauts safe over the course of their months-long journey to Mars.

Many of the lessons learned from operating the ISS will inform the design of advanced habitat modules(Credit: NASA)

Before being able to actually send a crew to Mars, the agency would have to demonstrate that the habitat had advanced environmental monitoring systems, adequate consumables storage, high-reliability avionics and exercise facilities capable of staving off the detrimental effects of microgravity.

One of the principal dangers facing astronauts during Mars' transit is exposure to deep-space radiation. Ordinarily we are shielded by Earth's magnetic field, but in deep space no such protection exists. Prolonged exposure to radiation, galactic cosmic rays and solar particle events can heighten risks of cancer and suppress an astronaut's immune system.

The radiation can also pose a danger to ship systems, as was the case with NASA's Dawn spacecraft in September last year, when a high energy radiation particle struck the probe as it was approaching the dwarf planet Ceres, forcing it to enter a safe mode. On a manned journey to Mars the effects of such an event could mean death for the crew, making a tried and tested radiation shield an essential component of the transportation habitat.

Scientists and engineers will also test how the habitat's systems respond to use after a prolonged period of dormancy. It will be built with standardization in mind, allowing NASA and partners to add modules and improve capabilities as operations require.

Earth Independent

The final stage of NASA's journey will represent the culmination of decades of experience in space exploration by both human and robotic pioneers, allowing the mission to operate with an unprecedented degree of independence from Earth.

Generations of robotic explorers have characterized Mars, granting us insights regarding what can be expected by a manned mission, and what resources could be used to keep human visitors alive. The first astronauts on Mars will be required to harvest local resources, converting them into water, fuel, building materials and of course, oxygen.

The importance of in-situ resource conversion cannot be understated. For example, NASA expects that the fuel needed to operate a 35 metric ton MAV would account for more than half of its mass. If the agency can develop a way to process Martian resources in order to create the necessary fuel, placing the MAV on the Martian surface becomes a much easier prospect.

Artist impression of the Mars 2020 rover(Credit: NASA)

However, while potential resources on Mars have been discovered, we have yet to test methods of converting them into actionable materials. With missions such as NASA's Mars 2020 rover, it is hoped to bridge this gap. Alongside a scientific suite designed to search for ancient life on the Martian surface, the 2020 rover will carry a resource utilization module designed to test a method of generating breathable oxygen from the Red Planet's tenuous atmosphere.

The final selection of a landing spot for the eventual manned mission will depend on observations made by the host of robotic explorers now present on the Red Planet, and those scheduled for insertion over the coming years.

Many aspects of the final phase of the mission are still uncertain due to the inherently unknown nature of operating on another planet for the first time. For example, once we get the habitats and equipment in Mars orbit, how do we then safely deploy them? NASA has had success lowering the Curiosity rover onto the surface of the Red Planet via a "sky crane," but this seems an unlikely solution for future missions.

The problem here, as is often the case with space exploration, is mass. Curiosity weighed in at under 1 metric ton. By contrast, NASA estimates that the modules and supplies required to make a manned mission viable would require several 20-30 metric ton payloads. This is but one of many challenges faced by the agency as it attempts to innovate its way to the Red Planet.

Other hurdles that must be addressed include the design and testing of a MAV to return astronauts to a transportation habitat in orbit around Mars, and an upgrade to the current communications systems.

The road map outlined by the agency represents an incremental yet extremely flexible plan to reaching the Red Planet. NASA states that its path avoids locking itself into an uncompromising architecture, instead favoring a direction that could be adapted to suit the needs and challenges discovered along the way.

Source: NASA (PDF)

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