Tuesday, April 14, 2015

Going to Mars: How Will We Get There and Who Should Go?

Would an all-female crew make sense on a deep space journey to Mars? Would the spacecraft rotate to simulate gravity? What's being done now to prepare for such a journey?

These were some of the questions addressed last Thursday by a panel of space scientists, writers, and engineers gathered in downtown DC to talk about the challenges of going to Mars. The discussion, called Giant Leap: The Race to Mars and Back, was organized by Future Tense, a collaboration between Slate magazine, the New America Foundation, and Arizona State University.

Phil Plait of Bad Astronomy moderated the first discussion and jumped straight in by asking what it is we need to do to get to Mars.

How Will We Get There?

One of the biggest challenges is the length of the mission—six to nine months going to Mars, perhaps eighteen months on Mars, and another six to nine months coming home for a total journey of at least two and a half years, according to Josh Hopkins, Space Exploration Architect for Lockheed Martin Space Systems.

The longest continuous time a human has ever spent in time to date is 437.7 days (1.2 years), by cosmonaut Valeri Polyakov onboard the Mir space station in the mid-1990s. Thus, some of the long-term physical and psychological effects of prolonged human space flight are still unknown.

But we do know that "your body is really efficient at getting rid of what you don't use," according to Tara Ruttley, NASA's associate International Space Station Program Scientist.

Muscle and bone density loss are well documented even on shorter journeys in microgravity, and would be a major issue for astronauts traveling to Mars. After all, they need to be able to walk when they finally arrive on the surface.

Ruttley said that major advances have been made and that bone density loss can be successfully halted by the right combination of weightlifting, treadmill time, and diet, specifically more than twice the normal amount of vitamin D. It seems that health always comes back to diet and exercise, even in space.

This effect continues to be studied, particularly with the year-in-space journey recently started by NASA astronaut Scott Kelly and cosmonaut Mikhail Kornienko. This prolonged ISS mission has the specific goal to extend our knowledge of the human condition in space so that future trips to Mars are feasible and safe.

An alternative popularized by science fiction is to remove microgravity all together and fly to Mars on a rotating ship. The centrifugal forces from the rotation would simulate the force of gravity and astronauts could walk around as normal.

Or not, as Hopkins emphasized. "Things don't drop in a straight line on a rotating platform." Astronauts would feel strong forces from changing their angular momentum as they walked in one direction and then another on a rotating spacecraft, unless the spacecraft was very, very big. The astronaut's head would also be moving at a different speed than their feet, creating a noticeable disorienting effect unless again the spacecraft was huge.

Hopkins and Ruttley both agreed that the first spacecraft that takes humans to Mars will not be a rotating platform, meaning they need to plan for the effects of long journeys in microgravity.

NASA's Orion program is currently undergoing unmanned launch tests. Combined with the upcoming Space Launch System rocket, Orion hopes to launch the first crewed mission by 2021 and eventually bring humans to the asteroids and Mars.

Astronaut Spacesuit Testing for the Orion Spacecraft. Credit: NASA/Bill Stafford

Who will be the first crew to Mars? 

It's likely to be a crew between four and six people—small enough to keep weight and life support costs reasonable but large enough for a diversity of skills and experience.

"Diversity is a really good thing on a long trip," said Kate Greene, a science writer and former crew member of the NASA-funded HI-SEAS project. This project simulations long duration Mars missions by placing crews of six in an isolated habitat in Hawaii for four months at a go. Greene was a crew member and project writer during the first 'mission' back in 2013. In last week's panel she emphasized that diversity in experience and training means that "the potential to solve problems increases significantly."

But physical diversity might raise the costs of a long-duration mission. The early Mercury, Gemini, and Apollo missions had a very narrow range of allowed heights for the astronauts, simply to keep the capsules smaller and lighter.

The space shuttle and ISS missions expanded the range of allowed heights, but this has meant additional engineering costs since a doorway or chair must be able to fit both a tall man and short woman. A future Mars mission might have to narrow the range again to keep costs low, according to Hopkins.

Greene explored the idea of an all-female crew to Mars in a Slate piece last October, based on the rates of calorie consumption and expenditure between the three men and three women in her HI-SEAS mission. The women burned less than half the calories of the men on a daily basis.

"We were all exercising roughly the same amount—at least 45 minutes a day for five consecutive days a week—but our metabolic furnaces were calibrated in radically different ways," said Greene in the Slate piece.

Weight is a big consideration on lengthy space missions and a smaller crew that consumes less food could make sense.

The panel went on to discuss the very real dangers of radiation in deep space and the issue of crew boredom on long journeys. To find out more, check out Tanya Lewis' article about the same panel on space.com.

By Tamela Maciel, also known as "pendulum"

Top image credit: NASA/JPL-Caltech/MSSS

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