Abstract
A cryogenic system is described for boring a small-diameter hole through various materials including rock, soil and stone. It employs a valveless technique in a borehead where cryogenic fluid fills at least one pulsejet which has proximal and distal ends. The cryogenic fluid is frozen into a plug near the distal end, acting as a valve. Cryogenic fluid just distal to the frozen plug is rapidly heated by thermal units causing it to become a rapidly-expanding gas bubble.
Inventors
Robert A. Spalletta