Xiangwu Zeng

Geotechnical Properties of JSC-1A Lunar Soil Simulant

For the success of planned missions to the moon in the near future, it is essential to have a thorough understanding of the geotechnical behavior of lunar soil. However, only a limited amount of information is available about geotechnical properties of lunar soils. In addition, the amount of lunar soils brought back to Earth is small. To help the development of new regolith moving machines and vehicles that will be used in future missions, a new lunar soil similant JSC-1A has been developed. A group of conventional geotechnical laboratory tests was conducted to characterize the geotechnical properties of the simulant, such as particle size distribution, maximum and minimum bulk densities, compaction characteristics, shear strength parameters, and compressibility.

Geotechnical Properties of NT-LHT-2M Lunar Highland Simulant

Future lunar explorations require a thorough understanding of the geotechnical properties of lunar soils. However, the small amount of lunar soil that was brought back to earth cannot satisfy the needs. A new lunar soil simulant, NU-LHT-2M, has been developed to simulate lunar regolith in the lunar highlands region. It is characterized to help the development of regolith-moving machines and vehicles that will be used in future missions to the moon. The simulant’s particle size distribution, specific gravity, maximum and minimum densities, compaction characteristics, shear strength parameters and compressibility have been studied; and the results are compared with the information about lunar regolith provided in the Lunar Sourcebook.

Calculation of Excavation Force for ISRU on Lunar Surface

Accurately predicting the excavation force that will be encountered by digging tools on the lunar surface is a crucial element of in-situ resource utilization (ISRU). Based on principles of soil mechanics, this paper develops an analytical model that is relatively simple to apply and uses soil parameters that can be determined by traditional soil strength tests. The influence of important parameters on the excavation force is investigated. The results are compared with that predicted by other available theories. Results of preliminary soil tests on lunar stimulant are also reported.

Geotechnical Properties of GRC-3 Lunar Simulant

AbstractGeotechnical properties of the lunar regolith are critical parameters in the design of equipment for in situ resource utilization (ISRU) on the Moon. It is imperative to simulate the geotechnical behavior of the lunar soil properly in the development of such equipment. Soil strength depends on the preparation method as well as the properties of the granular raw material. To execute the many small- and large-scale equipment tests planned for ISRU, it is necessary to develop a simulant that is inexpensive and can be produced in large quantities. This paper presents the methodology behind developing such a lunar-like geotechnical soil, GRC-3, and compares the properties of this soil with those of lunar regolith. The results show that particle size distribution, specific gravity, bulk density, and shear strength parameters for several preparation protocols are similar to that of lunar soil. Therefore, GRC-3 can be used in future large-scale experiments to predict the performance of ISRU equipment on t...

Experimental Measurements of Excavation Forces in Lunar Soil Test Beds

A series of experimental tests were performed with the aim of reproducing the in-situ geotechnical measurements conducted on the Surveyor lunar missions. An excavation and bearing test rig was set up that provided controlled high force actuation, and high resolution force and position measurement capabilities. Emphasis was placed methods of repeatable soil bin preparation. A replica of the returned Surveyor III excavator scoop, which is also identical to the Surveyor VII scoop, was fabricated and used in the test setup. Bearing forces using the replica model are compared with the Surveyor VII data. The forces and performance of a flat blade excavator and the SMSS in Nevada sand and JSC-1a lunar simulant are examined.

Developing a Lightweight Martian Soil Simulant for a High-Sinkage Mobility Test

AbstractThe geotechnical properties of Martian soils are critical parameters in predicting and simulating soil behavior with regard to vehicle performance on Mars. In preparation for manned or robotic missions to Mars, surface vehicles must be tested on terrains that represent the mechanical characteristics of the Martian ground. This paper presents the development of a lightweight simulant and its preparation method to emulate the mechanical properties of Martian soil for high sinkage mobility tests. A geotechnical testing program was developed to measure specific gravity, particle size distribution, bulk density, compression indices and shear strength. The simulant can achieve the typical Martian regolith density range, which is approximately 38% of that on earth. This is of particular importance because strength parameters of granular materials, which characterize the plastic behavior of soil samples in sinkage tests, are controlled by the effective confining pressure, which itself is induced by gravity.

Measurement of Small Cohesion of JSC-1A Lunar Simulant

AbstractBecause of the difficulty of applying low, effective confining pressure in a triaxial test, the reported small cohesion of JSC-1A lunar simulant from past research is neither accurate nor reliable. To develop an effective way to measure the cohesion parameter, a new method was adopted and demonstrated. As the value of the critical height of a vertical cut is proportional to the cohesion of a soil, the cohesion of JSC-1A simulant was obtained through simple calculations based on the critical height measured. Footprint demonstrations were also used to illustrate the existence of cohesion in JSC-1A simulant, in a comparison with the photograph of footprints of astronauts on the Moon. A group of critical height tests was conducted to obtain the cohesion of lunar simulant JSC-1A for a range of densities from 1.61 to 1.96 g/cm3. It was found that the cohesion of JSC-1A simulant varies in the range from 0.0 to 1.1 kPa, in an approximately linear relationship with the soil density.

Generation of Fine Particulates in Packed Granular Bed in the Carbon Dioxide Removal Assembly (CDRA)

One of the most pressing mic ro -gravity issues related to air revitalization systems is the generation and migration of fine particulates downstream of a reactor bed. It has been reported that particulate fines caused the failure of desiccant/adsorbent beds in maintaining a vacuum dur ing desorb cycles as well as causing Carbon Dioxide Removal Assembly (CDRA) selector valves to experience transition problems. There are five possible sources for the generation of these fine particulates: they may exist in the initial Zeolite material, th ey may be produced during compaction of the Zeolite bed, they may be generated during transportation of the bed, they may result from the increased stresses indu ced by the high level of acceleration during the launch of a rocket or space shuttle, and they may be caused by the breakup of particles resulting from thermal stresses during a space flight. The identification of the main sources of the fine particulates so as to provide a basis for engineering countermeasures, and an effective non -intrusive techni que that can continuously monitor the health status of the CDRA system are essential to the future extraterrestrial exploration missions of NASA. This paper reports the results of a study on the generation of fine particles under different stress level s an d stress cycles. Particle size analyses were conducted to determine the contents of fines in the Zeolite material before and after the application of different stress intensities and cycles. In addition, we are making an effort to develop a non -intrusive t echnique that can be configured for real -time health monitoring of the CDRA system using wave velocity measurement.