8. The implications of vehicle traction on the Moon for mining operations
Simplified Force Diagram for a Conventional Mine Shovel
The cutting force of a shovel is a function of hoist line pull, crowd effort, and front-end geometry. A large machine weight is needed to provide horizontal resistance to slippage during digging.
Courtesy of J. D. Humphrey, Dresser Industries
Traction is an important operational aspect of most vehicles. It is particularly important for vehicles that need to exert large horizontal forces; e.g., for excavating, loading, and hauling. Many types of mining equipment are very dependent on the development of adequate traction. This equipment includes excavation equipment such as bulldozer-mounted rippers and scrapers, front-end loaders, shovels, and drills, especially those for drilling angled or horizontal holes.
Comprehensive studies have been performed of vehicle traction on the Moon (among them, Karafiath 1970a,b; Nowatzki 1972). Even though these have addressed the operations of primarily small, lightweight roving vehicles, they provide fundamental insight into the traction of larger, heavier lunar mining vehicles. Moreover, experience with the lunar Rovers has provided an operational record by which to validate the traction models and predictions made for them.
Traction deserves attention because it is a major force needed for many mining operations. Because it is a function of gravity and of friction, the latter affected by vacuum, it will be affected by the space environment. Considerable experience is available to guide further research into this aspect of lunar mining.
9. Moon excavation technologies
This is an example of a good muck pile, well-fragmented and largely remaining in one heap. Loading would be much more time consuming if the rock were widely dispersed, as it might be by conventional blasting in a low-gravity environment, without air resistance. The loading machine must have sufficient traction (created by both friction and weight) to be able to push the loading bucket into the muck pile.
Lunar mining may involve the removal of various types of ground, ranging from massive solid rock to loose, granular soils. This possibility suggests the need to investigate a range of material- removal technologies. It may be desirable, at this early investigation stage, to distinguish between the fundamental mechanics underlying the technologies and the technologies themselves. Both will be affected by operations on the Moon, but in different ways.
a. Hard rock excavation mechanics
It is possible that vacuum might affect blasting performance, although it may not be a significant factor in low-permeability rock, at least at greater depths. The breakage induced by blasting is usually attributed in part to seismic effects and in part to gas pressure effects. Presumably gas pressure effects could attenuate much faster in a space environment than on Earth. This could affect fragmentation and almost certainly would affect heave and throw; i.e., rock movement.
Potential impacts of low gravity on mechanical excavation have been discussed under topic 1. Drastically different excavation technologies are summarized by Maurer (1980), and they deserve intense scrutiny for lunar applications.
b. Soft ground excavation mechanics
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Curator: Al Globus
NASA Responsible Official: Dr. Ruth Globus
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