Electromagnetic Energy Assisted Mechanical Drilling and its Applications in Space Exploration
- Paper number
IAC-11,A3,2.P,3,x9697
- Author
Mr. Alexandre Burelle, McGill University, Canada
- Year
2011
- Abstract
Drilling holes is an operation common to industrial and construction work. Conventional mechanical drills achieve this through the cutting and shearing of the material, energy being provided through the rotation of a drill bit and through gravity. Drawbacks of these drills include intense noise as well as the production of dust and vibrations. Radiation can also be used to bore holes through the thermal and ablation effects of lasers, but is a relatively expensive option which is typically reserved for specialized applications requiring a high level of precision. Electromagnetic energy assisted drills combine the precision and cleanliness of a laser with the cost effectiveness of a mechanical one. By focusing the beams from a magnetron, the apparatus producing microwaves in the eponymous kitchen appliance, it is possible to cause molecular motion by migration of ionic species and rotation of dipolar species in electromagnetic energy absorbing materials, which heats them up. The rise in temperature has been observed to decrease thermal conductivity and increase dielectric losses in many materials such as concrete, silicon, ceramics, rocks, glass, plastic, wood and bone. Higher dielectric losses translate in the absorption of more microwaves, which adds up in an effect known as thermal runaway. Some materials have been brought to their melting point with the use of concentrated microwaves. In such cases, little mechanical energy is required to create the excavation. In the case of rock, high temperatures, even if not surpassing the melting point, can ease mechanical drilling through the induction of cracks due to tensile failures caused by thermal dilatation of the rock. As this ultimately brings down the unconfined compressive strength of the rock, energy requirements for drilling are reduced. Potential applications include exploratory drilling on the Moon and other celestial bodies where gravity forces are low, energy is limited and where less wear on the drill bit translates to longer missions for rovers or other exploration vehicles charged with coring rock or soil samples for analysis. Electromagnetic energy was found to efficiently raise temperatures in carbon and metal oxides as well as metal sulfides, but most silicates, carbonates and sulfates do not heat well due to low dielectric losses. However, the use of electromagnetic energy assisted mechanical drills is generally better in rocks presenting differential thermal expansion and has the potential to have worthwhile applications in various mineralogical settings.
- Abstract document
- Manuscript document
(absent)