Thermal modeling of coring and drilling operations for solar system exploration applications
Abstract/Contents
- Abstract
- Heat created at a drilling site by the motion of a rotary-percussive coring system is a highly problematic, yet unavoidable consequence of geologic sample acquisition. This heat is particularly hazardous in the dry drilling techniques to be used for Mars sample return (MSR) and missions to the Solar System's moons, since heat has the capability of altering material composition or evolving compounds of interest, including water. In addition, sublimation of any ice contained in the rock or soil formation could cause vapor deposition onto cooler areas of the bit, permanently freezing the bit in the borehole and potentially leading to mission failure. A thermal model capable of predicting temperature profiles throughout the geologic formation and bit is an essential tool in creating drilling schedules that minimize both damage to samples and risk to system hardware. This investigation uses a series of drilling and coring tests, performed with a prototype MSR sampling system, to gather thermal data on a suite of solar system analog materials across a variety of atmospheric and starting thermal conditions. The materials and conditions were chosen to emulate rock types and conditions found on Mars and potentially on Jupiter's Moon Europa. The data is used to verify the accuracy of a finite element model specifically designed for this application. The model may be used to prevent rock or cuttings temperatures from reaching threshold values by predicting necessary pauses and/or power reductions. The average error of the model in predicting temperature profiles is 6.83%, with the errors of only two of eighteen tests exceeding 10%. A number of important relationships are found using the thermal profiles provided by the model. A linear relation between unconfined compressive strength (UCS) and maximum core temperature is developed, with decreased rock starting temperature leading to an increase in rock core temperature change. Maximum core temperature is dependent on system specific energy, defined as the ratio of energy consumption to rock volume excavated by the bit; rock parameters; operational parameters; and bit geometry by a simple power law. Energy transmission efficiency into the rock by a percussive bit is found to increase linearly with UCS and is also dependent on rock ambient pressure due to the subsequent changes in friction. Cuttings temperatures are identified by the model, which aids in the construction of sample acquisition schedules.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2013 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Szwarc, Timothy Justin |
|---|---|
| Associated with | Stanford University, Department of Aeronautics and Astronautics. |
| Primary advisor | Cantwell, Brian |
| Primary advisor | Christensen, R. M. (Richard M.) |
| Primary advisor | Hubbard, Scott, 1948- |
| Thesis advisor | Cantwell, Brian |
| Thesis advisor | Christensen, R. M. (Richard M.) |
| Thesis advisor | Hubbard, Scott, 1948- |
| Thesis advisor | Pollard, David D |
| Thesis advisor | Zacny, Kris |
| Advisor | Pollard, David D |
| Advisor | Zacny, Kris |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Timothy Justin Szwarc. |
|---|---|
| Note | Submitted to the Department of Aeronautics and Astronautics. |
| Thesis | Thesis (Ph.D.)--Stanford University, 2013. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2013 by Timothy Justin Szwarc
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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