The report is a study of the penetration and cracking of rocks using lasers available at the Avco Everett Research Laboratory. The objectives are to obtain data on the rate of rock damage for various laser conditions and to present an analytical program to predict the temperature and stress in rocks for pointed and annular beams of radiation. The laser power outputs used thus far was from 1 to 17 kW, CW, 10.6 microns and pulsed laser power up to 1000 joules in 20 microseconds. Data was taken with sharply focused as well as defocussed beams. Data is presented for continuous irradiation as well as pulsed, pointed beams and annular radiation patterns. Three types of hard rock were tested namely: quartzite, a Rhode Island granite, and Dresser basalt. Hole penetration energy per cm of penetration was found to be independent of laser intensity over 6 orders of magnitude. The specific energy for rock removal was found to depend on the fifth root of laser intensity over the same range.
