ACTUATOR, METHOD, AND SYSTEM

An actuator, including a housing having a flow conduit therethrough, a pressure balanced poppet disposed in the housing, initially preventing flow through the housing, and a heat evolving composition disposed to move the poppet by fluid heating to cease preventing flow through the housing upon ignition of the heat evolving composition. A method for actuating a tool, including igniting the heat evolution composition, heating a fluid located between the poppet and the housing, driving the poppet to move with the heated fluid, and flowing fluid through the housing. A borehole tool, including the actuator, a tool member disposed in the tool and movable by the fluid flowing through the housing, the movement of the tool member changing an operational condition of the tool. A borehole system, including a borehole in a subsurface formation, a string in the borehole, the actuator disposed within or as a part of the string.