If
humans are going back to the Moon for real, there's need for "counterfeit"
lunar materials. Known as simulants, tons of fake lunar soil is likely needed to assure that
future explorers can sustain their stay on Earth's neighboring Moon.
Any thought of setting up
machinery that converts lunar regolith -- that's the Moon's topside "rug" of rock and dust --
into building materials, solar cells, or fuel, water and oxygen supplies -- demands
a lot of beforehand work.
A NASA-sponsored "Lunar Regolith Simulant Materials Workshop"
starts today, co-organized by the space agency's Marshall
Space Flight
Center in Huntsville,
Alabama and the Johnson
Space Center
in Houston, Texas.
The three-day gathering of experts at the Marshall
Institute in Huntsville will look into how best to make and dole out quality
made-on-Earth specimens of the Moon -- a key step before humans replant footprints on that
nearby neighborhood of a cratered world.
NASA
on notice
When U.S. President George W. Bush put NASA on notice early last
year to start a return march to the Moon, the tasks ahead involve hurling robot
missions to the Moon no later than 2008. The first extended human expedition to
the lunar surface would occur as early as 2015, but no later than the year
2020.
While renewed lunar exploration would further science, it also
calls for new approaches, technologies, and systems -- including the use of
lunar and other space resources -- to support sustained human space exploration
to Mars and other destinations.
And
that means "living off the land" - a philosophy termed In-Situ Resource Utilization, or ISRU
in NASA dialect.
ISRU is use of local,
on-the-spot materials and energy sources pulled together and processed to
support human and robotic exploration. Better to use what's around than hauling
loads of materials from Earth.
Tons of lunar simulant,
called JSC-1, were produced years ago under the auspices of NASA's Johnson Space Center,
hence the name. Made from volcanic ash of basaltic composition, JSC-1's
composition mimicked many of the attributes of lunar mare soil samples.
But now supplies are
largely gone, with some of the material even hoarded by some researchers due to
its scarceness. And as a lunar return revs up, more investigators are in need
of varying types of simulate to test out hardware and processes.
Contracts and real money
"It
is getting to be a bit like Apollo all over again," said Lawrence
Taylor, Director of the Planetary Geosciences Institute in the Department
of Earth and Planetary Sciences at the University
of Tennessee in Knoxville, Tennessee.
He is on the scientific organizing committee for this week's workshop.
"President
Bush put us on the path to human exploration to the Moon, Mars, and beyond," Taylor said. "This fever
has permeated throughout NASA and the aerospace community such that contracts
and real money - in the hundreds of millions of dollars -- are being devoted to
the return to the Moon, with the obvious desire to perform ISRU studies on
lunar simulants in preparation for settlement of the Moon."
Taylor
said that for over the last 35 years, since the first human trek to the Moon,
the Apollo 11 mission in 1969, there have been numerous engineering studies of
lunar rocks and soil. Those studies were done for a myriad of purposes, he
said, all the way from construction purposes to mineral beneficiation for
processing on the Moon for propellants.
However, with a paucity of actual lunar sample allocated for
such studies - 99 percent went to science projects -- it was necessary to use
terrestrial samples that could be considered as simulants, Taylor said.
Apples,
oranges, peaches, pears
Given that lunar soils are so unique, Taylor continued, all sorts of simulants were
concocted in past years. And while good engineering was done, it was done using
poorly designed simulant, he said.
"In particular, it was not possible to compare results
because of apples, oranges, peaches, pears for simulants. The first lunar
simulant 'MLS-1' was made because it had an approximate chemistry to Apollo 11
soil 10084, but its mineralogy and engineering properties were all off.
Subsequent attempts to duplicate grain-size distribution and glass content were
not adequate. But, this was used by many investigators, most of whom
unknowingly were not using a good simulant," Taylor stated.
Taylor
recalled that in 1991, there was a special workshop on lunar simulants that
ultimately resulted in the manufacture of JSC-1 as the soil simulant. "This had
many more of the glass content, geotechnical properties for the lunar soil, but
was a bit off in composition. But, most importantly, it was an order of
magnitude better for engineering studies than anything terrestrial before."
"It is imperative that the materials upon which the
engineering studies are performed have a close resemblance to the lunar rocks
and soils," Taylor
remarked. "It is not possible, or smart, to not know exactly how the properties
of your earth-bound experiments directly relate to the lunar materials."
Why not free up all those specimens brought back from the
Moon by the six landing crews of Apollo in the 1969 - 1972 timeframe?
If you want to get a first-hand appraisal of the Apollo
keepsake collection of lunar materials, ask somebody that has gone the
distance. In this case, talk to Harrison "Jack" Schmitt, an Apollo 17 moonwalker
and geologist.
"Certainly, the real stuff should be made available for
specialized tests and to provide 'ground truth'", Schmitt advised. "I would
recommend that NASA convene a special outside working group to review the
inventory of lunar regolith from the six sites and then create a long-term plan
for its use in tests by the outside community, always preserving some for tests
of new ideas up to the time we clearly will be getting more."
Note
of caution
Schmitt said that his private sector interest in resource
production on the Moon, for example, needs more information on the detailed
geotechnical properties related to the design of mining and processing
machines.
Using the "real deal" Apollo specimens would be helpful in many tests, Schmitt said.
But he also added a note of caution.
"The main problem with this Apollo material is that it no
longer is in extremely hard vacuum and has not been for thirty-three-plus
years. Also, the samples and fractions taken from it for analysis have been
agitated by handling and splitting and have lost significant amounts of solar
wind volatiles," Schmitt explained.
Schmitt said the main problem with simulants will be
the lack of any of the ubiquitous nanophase iron particles found in
returned regolith samples, as well as being present in "agglutinates" -- a common particle
type in lunar sediment.
Agglutinates consist of small rock, mineral, and glass
fragments which are bonded together with glass. "Now, it may be possible to
simulate the environment that creates and distributes the nanophase iron for
small amounts of simulant," he added.
The University of Tennessee's Taylor
also sees need for performing tests with actual Apollo lunar samples. However,
every effort must be made to perform all the necessary experiments on suitable
lunar simulants. Furthermore, efforts must be made to miniaturize, as much as
possible, the nature of the experiment so that the feedstock of materials is
held to a minimum, he said.
Extraterrestrial homecoming
There are many new and innovative
ideas to assure that returning to the Moon in the 21st century will
be far more than a "flags and footprints" type of extraterrestrial homecoming.
"The issue is one of reliability...preparing and evaluating
the technologies properly ahead of time...before they are launched," said Laurent
Sibille, lead scientist for space resources utilization at BAE Systems
Analytical Solutions, a contractor at NASA's Marshall Space
Flight Center.
Sibille said the workshop is devoted to establishing
requirements for the production and distribution of terrestrial analogs of
lunar regoliths. Those analogs would become the accepted source material
standards for research and development efforts on space resources utilization
technologies. The current lack of available and commonly accepted simulant
materials hampers research progress and often renders studies and performance
comparisons of technologies inconclusive, he suggested.
For example, Sibille recalled that simulated lunar soil
proved valuable in helping engineers design, build and test the Apollo lunar
rover. That four-wheeled manually controlled, electrically powered moon buggy
was driven by astronauts on Apollo 15, 16, and 17.
"The main issue is that we're aiming to develop a set of
materials for everybody to use...to actually come to a credible consensus,"
Sibille said.
Family
of customers
"We've got
a whole family of customers out there," said NASA's Ron Schlagheck, ISRU and
materials science program manager at Marshall
Space Flight
Center. Without creating
an agreed to standard family of simulants "we're going to have arguments 'till
the cows come home on what the outcomes of these technology research projects
will be over the years to come," he said.
Schlagheck
and Sibille said that
this week's workshop is to help NASA Headquarters grapple with priorities in
terms of the type of simulants needed quickly and how best to produce them to
move lunar activities into high gear. Also the meeting will identify other
simulant types that would be needed in later years.
A need for tons of lunar simulant is foreseen, Sibille said,
but whether there's need for ten tons or a thousand tons, "that we don't have
an answer for as yet."
"There's need for more than grams or a few pounds," Schlagheck concluded.
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