Present and future technologies to facilitate lunar composition and resource assessment with applications to lunar surface construction are presented. We are particularly interested in the construction activity associated with lunar-based astronomy. We address, as an example, the use of ground-probing radar to help assess subsurface conditions at sites for observatories and other facilities

Chua, Koon Meng

Johnson, Stewart W.

English

NASA Technical Reports Server

LPI Technical Report 92-06 33
TABLE 2. Selected X-ray escape depths ( A).
Energies (eV)
Material 30.5 72.4 91.5 151.1
10084 glass
67701 glass
ZnS
190
180
430
470
380
530
510
420
670
630
660
It is also useful to know how thick a region of the lunar surface
will be sampled by these soft X-rays. We have estimated mean
escape depths for several energies and compositions corresponding
to a mare glass, a highland glass, and ZnS using the mass attenuation
coefficients of Henke et al. [4], and present them in Table 2.
High spatial resolution combined with the thin surface layer
from which these soft X-rays arise suggests the exciting possibility
that X-ray telescopes could map lunar volcanic volatiles from orbit.
The most characteristic feature of known lunar volcanic volatile
deposits is a conspicuous enrichment in sulfur and zinc on grain
surfaces [5,6]. These Zn,S-rich surface films can be seen in SEM
images. In XPS studies [7) we have found surface Zn concentrations
higher than 5 atomic percent and have estimated a depth of at
least 100 A. Thus Apollo 17 orange glass appears to have enough
Zn and S to be seen from orbit, and it would be very surprising
if there are not other lunar regions much richer in volcanic
volatiles.
In our XPS studies of lunar regolith fines |8) we found that
a significant fraction of the iron in the outer few hundred ang-
stroms of grain surfaces was reduced to the metallic form, pre-
sumably as a result of micrometeorite vaporization and solar wind
effects. Because of the strong possibility of substantial reoxidation
of lunar material during storage, sample preparation, and analysis,
we cannot know what the reduced fraction was on the lunar
surface, but it may have been large. The M2j XPS lines and M>}VV
Auger lines of Fe++ and Fe° have different shapes and energies,
allowing them to be easily distinguished. It seems likely that the
Mi)V X-ray line will also, so the oxidation state of Fe in the regolith
might be mapped with properly chosen telescopes.
We thus suggest that, in addition to major-element mapping,
consideration be given to volcanic volatile mapping and regolith
oxidation state mapping.
This work was supported by the Rockwell Independent Research
and Development Program.
References: 111 Schmitt J. H. M. M. et al. (1991) Nature, 349,
583-587. [2) Edwards B: C. et al. (1991) GRL, 18, 2161-2164.
[3] Housley R. M. and Grant R. W. (1976) Proc. ISC 7th, 881-
889. |4) Henke B. L. et al. (1982) Atomic Data and Nuclear Data
Tables, 27, 1. [5] Butler P. Jr. and Meyer C. Jr. (1976) Proc
Apof/o Jl LSC, 1561-1581. [6] Cirlin E. H. (1978) Proc. LPSC
9th, 2049-2063. [71 More complete analysis of data in reference
[6]. [8] Housley R. M. and Grant R. W. (1977) Proc. LPSC 8th,
3885-3899.
3-17253
ASSESSMENT OF THE LUNAR SURFACE LAYER AND
IN SITU MATERIALS TO SUSTAIN CONSTRUCTION-
RELATED APPLICATIONS. Stewart W. Johnson1 and Koon
Meng Chua2, 'BDM International, Inc., 1801 Randolph Road SE,
Albuquerque NM 87106, USA, Department of Civil Engineering,
University of New Mexico, Albuquerque NM 87131, USA.
In this paper we focus on present and future technologies to
facilitate lunar composition and resource assessment with appli-
cations to lunar surface construction. We are particularly inter-
ested in the construction activity associated with lunar-based
astronomy. We address, as an example, the use of ground-probing
radar to help assess subsurface conditions at sites for observatories
and other facilities.
We feel that a multidisciplinary effort is desirable to identify
what engineering data on the lunar environment and on the lunar
soil and rock should be collected and how it should be obtained.
Johnson and Burns [1] have urged action to acquire the following
information and resolve issues indicated: (1) topographic maps of
potential observatory sites (e.g., 10-cm contours over an area 1 km
in radius); (2) detailed boulder sizes and counts over the same
area; (3) surveys (e.g., by radar, microwave, or other means) for
subsurface boulders over critical areas where foundations and
excavation are desired; (4) surveys of depth-to-bedrock (with
suitable definition and characterization of bedrock); (5) trenching
and bulldozing experiments to establish energy requirements and
depth limitations of these operations; (6) drilling and coring exper-
iments (with energy consumption and depth limitations clarified);
(7) force-vs. -depth cone penetrometer measurements to be used
for siting settlement-sensitive telescope structures; (8) trafficabili ty
measurements including establishing energy consumption, slope-
climbing capabilities, and formation of ruts or depressed surfaces
by repeated traverses of unprepared surfaces; and (9) electrostatic
charge measurements.
This listing has grown out of discussions with Dr. W. David
Carrier III of the Lunar Geotechnical Institute and others. The
list will vary somewhat depending on requirements for lunar-based
facilities and operations. Johnson et al. [2] have noted that it is
necessary to start now to develop the concepts and technologies
for the next generation of space-based telescopes. A successor for
the Hubble Space Telescope could be either -in high Earth orbit
(HEO) or on the Moon. To properly assess the merits of these
suggested future telescopes, technology development for lunar as
well as HEO telescopes should now be pursued so that properly
informed decisions may be made. Part of the technology devel-
opment requires improved understanding of engineering properties
of lunar surface and subsurface materials and dust behavior. John-
son and Wetzel [3) note that the success of a large lunar-based
telescope will depend on an appropriately engineered structure,
a suitable interface (foundation) with the lunar regolith, and a
carefully thought-out construction process. Johnson and Burns 1 1 ]
have discussed the technology development required for large
lunar telescopes and lunar optical/UV/lR synthesis arrays. They
encourage the community to plan early lunar-bound payloads and
surface operations to advance the knowledge and understanding
required for building large telescopes on the Moon after the year
2000. Examples of key technologies for large lunar observatories
that we feel deserve attention early in the program to return to
the Moon are
https://ntrs.nasa.gov/search.jsp?R=19930008064 2020-03-24T07:24:24+00:00Z
34 Neu> Technologies for Lunar Resource Assessment
1. Geotechnical (e.g., soils, excavation, foundations, and use
of in situ materials for shielding).
2. Mitigation of detrimental effects of the environment (e.g.,
dust, thermal, primary and secondary impacts of micrometeoroids,
radiation, and vacuum). This area includes obtaining a better
understanding of the dust and debris environments above and on
the surface of the Moon.
3. Approaches to use in construction on the Moon (e.g., ex-
travehicular activity, robotics, telepresence, assembly aids, con-
nectors). The appropriate choices can be made only with adequate
knowledge of the surface conditions and variability.
4. Contamination/interference control and restoration pro-
cesses. May vary with chemistry and mineralogy.
5. Performance of optical and related systems and charge-
coupled devices (CCDs) on the Moon. CCDs deserve particular
attention with respect to shielding requirements against cosmic
and solar flare radiation. Shielding will probably be with in situ
materials requiring excavation and placement at desired densities.
6. Test and evaluation techniques for lunar observatory systems
and construction approaches to validate approaches before return-
ing to the Moon. Depends on devising appropriate simulation of
lunar conditions.
We anticipate that the initial telescopes on the Moon will be
small automated instruments that have already been shown to
be feasible by existing Earth-based robotic telescopes. These early
telescopes will not only establish the viability of telescopes on the
lunar surface, but will also perform excellent extended observa-
tions during the long lunar nighr to test models of active stars
and galaxies, and do all-sky CCD surveys in the ultraviolet and
infrared using a Schmidt wide-field telescope to complement the
important sky survey done at Mount Palomar. We conclude that
attention must be given to instrumenting these small telescopes
in innovative ways to obtain information that will help find
answers to unknowns in the areas listed above. We suggest that
there are excellent opportunities to use the early landers to
investigate the behavior of the soil under load, determine the
extent of dust movement (e.g., levitation) associated with the
passage of the lunar terminator, and place bounds on disturbances
associated with vehicle operations on the Moon. Creative uses
of information obtained from many innovative approaches may
be used to help make lunar-based telescopes a reality.
For example, ground-probing radar has many terrestrial appli-
cations (e.g., in-assessing pavement layer thicknesses in highway
engineering applications, in determining the location of fissures
in the dry lake bed at the Edwards Air Force Base shut t le landing
site, and at Meteor Crater, Arizona, in investigations of the ejecta
blanket). We propose to use this technology on che'Moon in
conjunction with other techniques such as penetrometers, borings,
and core recovery to ascertain needed subsurface soil and rock
properties. The goal is to minimize the use of labor-intensive
subsurface sampling required during site investigations on the
Moon and to improve approaches to assessing in situ lunar con-
struction materials.
References: [1] Johnson S. W. and Burns J. O. (1991) Pro-
ceedings of the Common Lunar Lander Workshop, NASA, Houston.
[2] Johnson S. W. (1992) Proceedings of Space 92, American Society
of Civil Engineers, New York. [3] Johnson S. W. and Wetzel J. P.
(1992)j. Aerosp. Eng.. 5.
AN IN SITU TECHNIQUE FOR ELEMENTAL ANALYSIS
OF LUNAR SURFACES. K. Y. Kane and D. A. Cremers, CLS-
4, Mail Stop J567, Los Alamos National Laboratory, Los Alamos
NM 87545, USA.
An in situ analytical technique that can remotely determine
the elemental constituents of solids has been demonstrated. Laser-
Induced Breakdown Spectroscopy (LIBS) is a form of atomic
emission spectroscopy in which a powerful laser pulse is focused
on a solid to generate a laser spark, or microplasma. Material in
the plasma is vaporized, and the resulting atoms are excited to
emit light. The light is spectrally resolved to identify the emitting
species.
LIBS is a simple technique that can be automated for inclusion
aboard a remotely operated vehicle. Since only optical access to
a sample is required, areas inaccessible to a rover can be analyzed
remotely. A single laser spark both vaporizes and excites rhe sample
so that near real-time analysis (a few minutes) is possible. This
technique provides simultaneous multielement detection and has
good sensitivity for many elements. LIBS also eliminates the need'
for sample retrieval and preparation preventing possible sample
contamination. These qualities make the LIBS technique uniquely
suited for use in the lunar environment.
LIBS has been demonstrated using several different types of
samples at distances between 4 and 18 m. Analyzed samples include
simulants of Apollo mission Moon rocks, Mauna Loa basalt sam-
ples, and rock powder reference standards. An example of the
spectra obtained with this technique using an Apollo Moon rock
simulant is presented in Fig. 1. The presence of several elements
such as aluminum, calcium, iron, magnesium, silicon, and t i tanium
is clearly evident.
A portable LIBS instrument has been field tested with good
preliminary results. An exposed tuff face was interrogated by the
laser spark at a distance of approximately 18 m in bright sunlight.
Spectra obtained at this distance displayed very strong emission
Mg(II )
i
2800 2900 3000 3100 3200 3300
Ti(II)
/ Mg(l)
I I I
3400 3500 3600 3700 3800 3900
3900 4000 4100 4200 4300
Angstroms
4400
Fig. 1. Laser spark spectra of an Apollo Moon rock simulant in a vacuum
chamber at a distance of approximately 10 m.


Assessment of the Lunar Surface Layer and in Situ Materials to Sustain Construction-related Applications

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