Magnetorheological fluid controlled mud pulser

An apparatus for generating a pressure pulse in a column of circulating fluid, the apparatus comprising:

• a first rotating member disposed in the column of circulating fluid;
• a chamber containing an electroactive fluid isolated from the circulating fluid;
• a second rotating member attached to said first rotating member and at least partially contained within said chamber of electroactive fluid;
• a magnet proximate to said chamber of electroactive fluid and switchable between first and second states so as to apply a field to the electroactive fluid in the first state and not apply a field to the electroactive fluid in the second state.

An apparatus for generating pressure pulses in a column of circulating fluid, the apparatus comprising:

• a housing adapted for communicating the circulating fluid therethrough;
• a first body in said housing and adapted for rotation in the circulating fluid;
• a chamber in said housing and enclosing an electroactive fluid;
• wherein said chamber is isolated from the circulating fluid;
• a second body in said housing and connected to said first body;
• wherein said second body is at least partially disposed within said chamber and has an outer surface in contact with said electroactive fluid;
• and
• a magnet switchable between a first state applying a field to the electroactive fluid and a second state not applying a field to the electroactive fluid.