ITL accumulated extensive experience in understanding of the main characteristics of the simulated lunar environment factors and in design, development and manufacturing of space environmental simulators and, specifically, of lunar environmental simulators designed for high fidelity simulation of the lunar environments.
The planetary environmental simulator is the only practical approach for testing and life time evaluation of planetary exploration spacecraft materials and structures. Only in the simulators it is possible to reproduce the vacuum or planetary atmosphere conditions together with a variety of other environmental factors.
With lunar exploration activities picking up the pace, many new materials and structural elements will be used in these exploration activities on the Moon. The screening, selection and evaluation of such new materials and structures in ground simulators before they are used on the Moon will become a necessary step in full analogy of the intensive screening and characterization of materials and structural elements that were and are being developed for use in LEO and GEO environments in ground LEO simulators, for atomic oxygen effects, and in GEO simulators, for charging effects.
ITL designs and manufactures lunar environment simulators that allow physically evaluate the effects of the Lunar dust environment in conjunction with other environmental factors (ultra-high vacuum or planetary atmospheric conditions, UV radiation, thermal conditions/thermal cycling, darkness, VUV and NUV, protons and electrons) and verify the effectiveness of dust mitigation strategies and technologies for all planetary exploration surface systems. The system is designed using an integrated approach that allows using it as a universal space and planetary simulator by adding or removing space environment sources.
Technical Requirements to Lunar Simulator
The recent models of the lunar environmental simulator are based on a series of successfully developed prototypes of Lunar Environment Simulators built by ITL under contracts to the Canadian Space Agency ( Figure 1) and other International ( Figure 2) and National (Figure 3) clients or for its own use (Figure 5). The system includes a modular design consisting of a stainless-steel vacuum chamber to simulate ultra-high vacuum conditions, lunar dust particles source, UV radiation source, thermal conditions/thermal cycling in the appropriate temperature range and ability to recreate the darkness conditions present on the back side of the Moon. Other sources and additional modules could be included as required and after consultations.
Figure 1 Vacuum Lunar Dust Simulator prototype built by ITL
in accordance with the contract to Canadian Space Agency
Figure 2 Image of the Vacuum Lunar Dust Simulator built by ITL
for Lanzhou Institute of Physics, in China
Figure 3 Image of the Vacuum Lunar Dust Simulator built by ITL for McGill University in Montreal, Canada
Figure 4 Cross-sectional view of the main vacuum chamber showing a possible arrangement of all sources.
Figure 5 Image of a new design Lunar Environment Simulation Facility built by ITL
Dust particles source system
Since the dust particles source is one of the major parts of the lunar simulator, a great deal of effort was put at ITL into the design and optimization of the parameters and performance of this system. In in which a dust cloud is formed that surrounds the test object).
For laboratory-type lunar simulators only the last two types of sources, i.e. the gravitational and the agitational are general, the existing dust particle sources can be broadly divided into three major categories:
a) immersion (in which the tested object is immersed on a large bed of simulant), and
b) gravitational (with the dust simulant being distributed from above by gravitational force);
c) agitational
Based on the initial experiments with both types of sources, the agitational type lunar dust particles source was rejected for further development and a Dust Particles Source System based on a gravitational type of dust source was selected and designed. The present dust particle source includes the following main components:
– Dust Preparation System (Figure 6);
– Dust Distribution Mechanism, or Dust Cloud Forming Unit (Figure 7, Figure 8 ); and
– UV and electron Dust Charging Units.
Figure 6 General view of various models of the Dust Preparation Unit
Figure 7 Images of different models of the Dust Distribution Unit
Figure 8 Images of a Dust Distribution Unit installed inside the vacuum chamber of the Lunar Environment Simulator
Lunar dust
“Lunar regolith” describes the layer of particles on the Moon’s surface generated by meteoritic impacts, and is comparable to terrestrial volcanic ash [5]. The finest component is referred to as dust (< 100 μm).
Many properties of the lunar dust have been characterized. Lunar dust is described as a basaltic ash having a specific density of 2.9 g/cm3, an average grain radius of ~ 70 μm with roughly 10 to 20% by weight < 20 μm [5], and low electrical conductivity [6,7]. Dust on the Moon is electrified, at least in part, by exposure to the solar wind. The low electrical conductivity of the regolith allows individual dust grains to retain electrostatic charge. On the lunar dayside the electrical conductivity can increase with surface temperature and IR and UV radiation [5], a fact that needs to be taken into account for surface and dust charging processes. Many simulants of the lunar dust exist that reproduce the morphology and compositions of lunar dust. Figure 9 through Figure 11 show some of the lunar simulants.
Figure 9 Optical and scanning electron microscopy (SEM/EDS) images showing surface morphology and the composition of JSC-1AF lunar dust simulant. The upper left image shows a pile of the dust simulant from which the SEM images were obtained.
Figure 10 Secondary Electron Microscopy micrographs of OB-1 (Chenobi) lunar dust simulant
Figure 11 Optical microscopy of the LHS-1 (left image and LMS-1 (right image) lunar dust simulants
Figure 12 Sample holder with a number of different materials in process of being exposed to the MLS-1 lunar dust simulant in the vacuum lunar dust simulator (upper image) and after the experiment.
