Ifhumans 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 thatfuture explorers can sustain their stay on Earth's neighboring Moon.
Any thought of setting upmachinery 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 -- demandsa lot of beforehand work.
A NASA-sponsored "Lunar Regolith Simulant Materials Workshop"starts today, co-organized by the space agency's MarshallSpace FlightCenter in Huntsville,Alabama and the JohnsonSpace Centerin Houston, Texas.
The three-day gathering of experts at the MarshallInstitute in Huntsville will look into how best to make and dole out qualitymade-on-Earth specimens of the Moon -- a key step before humans replant footprints on thatnearby neighborhood of a cratered world.
When U.S. President George W. Bush put NASA on notice early lastyear to start a return march to the Moon, the tasks ahead involve hurling robotmissions to the Moon no later than 2008. The first extended human expedition tothe lunar surface would occur as early as 2015, but no later than the year2020.
While renewed lunar exploration would further science, it alsocalls for new approaches, technologies, and systems -- including the use oflunar and other space resources -- to support sustained human space explorationto Mars and other destinations.
Andthat means "living off the land" - a philosophy termed In-Situ Resource Utilization, or ISRUin NASA dialect.
ISRU is use of local,on-the-spot materials and energy sources pulled together and processed tosupport human and robotic exploration. Better to use what's around than haulingloads 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'scomposition mimicked many of the attributes of lunar mare soil samples.
But now supplies arelargely gone, with some of the material even hoarded by some researchers due toits scarceness. And as a lunar return revs up, more investigators are in needof varying types of simulate to test out hardware and processes.
Contracts and real money
"Itis getting to be a bit like Apollo all over again," said LawrenceTaylor, Director of the Planetary Geosciences Institute in the Departmentof Earth and Planetary Sciences at the Universityof Tennessee in Knoxville, Tennessee.He is on the scientific organizing committee for this week's workshop.
"PresidentBush put us on the path to human exploration to the Moon, Mars, and beyond," Taylor said. "This feverhas permeated throughout NASA and the aerospace community such that contractsand real money - in the hundreds of millions of dollars -- are being devoted tothe return to the Moon, with the obvious desire to perform ISRU studies onlunar simulants in preparation for settlement of the Moon."
Taylorsaid 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 oflunar rocks and soil. Those studies were done for a myriad of purposes, hesaid, all the way from construction purposes to mineral beneficiation forprocessing on the Moon for propellants.
However, with a paucity of actual lunar sample allocated forsuch studies - 99 percent went to science projects -- it was necessary to useterrestrial 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 wereconcocted in past years. And while good engineering was done, it was done usingpoorly designed simulant, he said.
"In particular, it was not possible to compare resultsbecause of apples, oranges, peaches, pears for simulants. The first lunarsimulant 'MLS-1' was made because it had an approximate chemistry to Apollo 11soil 10084, but its mineralogy and engineering properties were all off.Subsequent attempts to duplicate grain-size distribution and glass content werenot adequate. But, this was used by many investigators, most of whomunknowingly were not using a good simulant," Taylor stated.
Taylorrecalled that in 1991, there was a special workshop on lunar simulants thatultimately resulted in the manufacture of JSC-1 as the soil simulant. "This hadmany more of the glass content, geotechnical properties for the lunar soil, butwas a bit off in composition. But, most importantly, it was an order ofmagnitude better for engineering studies than anything terrestrial before."
"It is imperative that the materials upon which theengineering studies are performed have a close resemblance to the lunar rocksand soils," Taylorremarked. "It is not possible, or smart, to not know exactly how the propertiesof your earth-bound experiments directly relate to the lunar materials."
Why not free up all those specimens brought back from theMoon by the six landing crews of Apollo in the 1969 - 1972 timeframe?
If you want to get a first-hand appraisal of the Apollokeepsake collection of lunar materials, ask somebody that has gone thedistance. In this case, talk to Harrison "Jack" Schmitt, an Apollo 17 moonwalkerand geologist.
"Certainly, the real stuff should be made available forspecialized tests and to provide 'ground truth'", Schmitt advised. "I wouldrecommend that NASA convene a special outside working group to review theinventory of lunar regolith from the six sites and then create a long-term planfor its use in tests by the outside community, always preserving some for testsof new ideas up to the time we clearly will be getting more."
Schmitt said that his private sector interest in resourceproduction on the Moon, for example, needs more information on the detailedgeotechnical properties related to the design of mining and processingmachines.
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 nolonger is in extremely hard vacuum and has not been for thirty-three-plusyears. Also, the samples and fractions taken from it for analysis have beenagitated by handling and splitting and have lost significant amounts of solarwind volatiles," Schmitt explained.
Schmitt said the main problem with simulants will bethe lack of any of the ubiquitous nanophase iron particles found inreturned regolith samples, as well as being present in "agglutinates" -- a common particletype in lunar sediment.
Agglutinates consist of small rock, mineral, and glassfragments which are bonded together with glass. "Now, it may be possible tosimulate the environment that creates and distributes the nanophase iron forsmall amounts of simulant," he added.
The University of Tennessee's Tayloralso sees need for performing tests with actual Apollo lunar samples. However,every effort must be made to perform all the necessary experiments on suitablelunar simulants. Furthermore, efforts must be made to miniaturize, as much aspossible, the nature of the experiment so that the feedstock of materials isheld to a minimum, he said.
There are many new and innovativeideas to assure that returning to the Moon in the 21st century willbe far more than a "flags and footprints" type of extraterrestrial homecoming.
"The issue is one of reliability...preparing and evaluatingthe technologies properly ahead of time...before they are launched," said LaurentSibille, lead scientist for space resources utilization at BAE SystemsAnalytical Solutions, a contractor at NASA's Marshall Space Flight Center.
Sibille said the workshop is devoted to establishingrequirements for the production and distribution of terrestrial analogs oflunar regoliths. Those analogs would become the accepted source materialstandards for research and development efforts on space resources utilizationtechnologies. The current lack of available and commonly accepted simulantmaterials hampers research progress and often renders studies and performancecomparisons of technologies inconclusive, he suggested.
For example, Sibille recalled that simulated lunar soilproved valuable in helping engineers design, build and test the Apollo lunarrover. That four-wheeled manually controlled, electrically powered moon buggywas driven by astronauts on Apollo 15, 16, and 17.
"The main issue is that we're aiming to develop a set ofmaterials for everybody to use...to actually come to a credible consensus,"Sibille said.
"We've gota whole family of customers out there," said NASA's Ron Schlagheck, ISRU andmaterials science program manager at Marshall Space Flight Center. Without creatingan agreed to standard family of simulants "we're going to have arguments 'tillthe cows come home on what the outcomes of these technology research projectswill be over the years to come," he said.
Schlagheckand Sibille said thatthis week's workshop is to help NASA Headquarters grapple with priorities interms of the type of simulants needed quickly and how best to produce them tomove lunar activities into high gear. Also the meeting will identify othersimulant 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 havean answer for as yet."
"There's need for more than grams or a few pounds," Schlagheck concluded.