Generally, the shaft would rotate with a drill bit at the bottom. But, it seems in the case of Superdeep Borehole, they developed a new mechanism to rotate only the drill bit at the bottom of the shaft[1]. They pumped pressurized "drilling fluid"[2][3] down the shaft to spin the drill bit.
Comments
Generally, the shaft would rotate with a drill bit at the bottom. But, it seems in the case of Superdeep Borehole, they developed a new mechanism to rotate only the drill bit at the bottom of the shaft[1]. They pumped pressurized "drilling fluid"[2][3] down the shaft to spin the drill bit.
[1]http://www.ritchiewiki.com/wiki/index.php/Kola_Superdeep_Bor...
[2]http://www.supertightstuff.com/03/18/featured/kola-superdeep...
[3]http://www.damninteresting.com/the-deepest-hole/