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 moon.
Setting up the 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 will demand a lot of work beforehand.
A NASA-sponsored “Lunar Regolith Simulant Materials Workshop” starts Monday, co-organized by the space agency’s Marshall Space Flight Center in Huntsville, Ala., and the Johnson Space Center in Houston.
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 President Bush put NASA on notice early last year to start a return march to the moon, the scheduled tasks involved 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 will further science, it also will call 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. 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.”
During the 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, Taylor said, all the way from construction purposes to mineral beneficiation for processing on the moon for propellants.
However, with a paucity of actual lunar samples 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," he said.
“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 earthbound 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 firsthand appraisal of the Apollo keepsake collection of lunar materials, ask somebody who 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 33-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 that 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.
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 a 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 10 tons or 1,000 tons, “that we don’t have an answer for as yet.”
“There’s need for more than grams or a few pounds,” Schlagheck concluded.