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- It's no secret that sending humans to Mars poses many
risks for the health of astronauts, whose bodies must endure months and
years outside the normal gravity of Earth. But exploring beyond orbit entails
a less obvious danger to space travelers, according to a report from the
National Research Council due for release soon. The same microgravity which
affects the way an astronaut's blood flows can also alter -- and potentially
disable -- mechanical systems crucial to a long-duration crew's survival
operate.
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- The study, a pre-publication version of which was made
available to SPACE.com, urges NASA to begin an extensive research program
to understand how everything from power generators to waste systems will
work in a largely gravity-free environment. And the group led by Purdue
University engineer Raymond Viskanta also warns that NASA's current efforts
are poorly coordinated and duplicative, which poses a stumbling block to
developing the systems necessary to ensure a safe arrival and stay on another
planet.
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- Travelers, as well as equipment on a Mars trip must endure
the microgravity between planets, followed by intense gravity levels during
landing and, finally, the martian gravity which is less than half that
of Earth. And both humans and equipment must be protected from the surface
pressure of 6 to 10 millibars -- far less than the average 1,000 on Earth
-- as well as surface temperatures far below freezing. Much of NASA research
into long-duration travel has centered on Spacelab and Mir space station
data on the effects of microgravity on the human body.
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- But microgravity also would have profound effects on
welding, the operation of wicks in thermal pipes used to disperse excess
heat and the way liquids are stored in cryogenic tanks -- all critical
components of any interplanetary expedition. While some of microgravity's
unique effects offer innovations -- the growth of crystals, for example
-- the same effects pose tremendous engineering challenges that must be
researched thoroughly, the report states.
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- Foremost among these is the way fluids and materials
flow in space. Most earthbound power systems, for example, use a two-stage
process -- liquid water, then steam in a steam-powered plant, for example
-- to move mass, momentum and energy. Such systems depend in part on gravity.
Fluids tend to separate on Earth, with the heavier ones falling and the
lighter ones rising, while in space this is not the case. Aboard the space
shuttle and space station, NASA uses single-phase rather than multi-phase
systems to avoid this problem, but for longer missions multi-phase systems
are desirable because they are more efficient. "The lack of phase
separation in microgravity has severely compromised a range of promising
technologies" for long-term expeditions, ranging from propulsion to
sanitation, the Viskanta panel states.
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- The team therefore urges NASA to sponsor research developing
and examining models that predict the flow of fluids and gases in multi-phase
systems in the microgravity of space and the low gravity of places like
Mars.
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- Fire is a constant fear aboard any closed system, whether
it be a submarine or space station or Mars-bound spacecraft. But combustion
also is affected by gravity, and "flame structure is drastically altered
from the upward convective form in Earth gravity to a quiescent spherical
form" in space. This, the panel warns, has profound implications for
how fire can be predicted and fought. Flammability of materials is different
in space, flames can smolder in exotic ways, and flames spread quite differently
-- all areas that require study.
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- To take into account all of these effects, "a directed
program of experimental and analytical research will be required,"
the panel states. But better management as well as lab work is necessary,
the study adds. Panel members had "considerable difficulty" gathering
data for the study given NASA's organization, in which "outstanding
research efforts in some centers were either poorly communicated to groups
at other centers or [were] duplicated by efforts of those other centers."
The Viskanta panel complains that "territoriality" among the
centers "has been allowed by senior management to develop, and even
to accelerate." That fact will make it hard to implement the panel's
recommendation for a sweeping research program, according to the report.
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- Eugene Trinh, who heads NASA's microgravity program,
praised the panel's report as a comprehensive blueprint, but added that
he did not expect to request major new funding in the near future. Only
about $3 million to $4 million goes to studying human exploration out of
a budget of nearly $110 million, he added. He added that he is not aware
of problems among NASA centers.
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