A hot fluid expansion engine has a plurality of actuator modules arranged in a star configuration around a central shaft. Each module includes a drive piston defining a working chamber of variable volume in the first enclosure; a movable displacement piston subdividing a second enclosure into a low temperature chamber of variable volume and a high temperature chamber of variable volume with the high temperature chamber communicating with a unit of a fluid heater device and the low temperature chamber communicating with the working chamber; and a fluid circulation circuit extending between the fluid heater device and the working chamber. The drive piston and the displacement piston of each actuator module are connected to the central shaft via respective first and second eccentric transmission devices suitable for imparting reciprocating motion in translation to each of the pistons with a phase lag of 90.

An alternative heat source for an internal combustion engine with an elongated compartment with first and second ends, a directed energy device capable of sending a pulse of photonic energy to a focal point within the first end of the compartment, an intake allowing for the entry of a gas into the the elongated compartment, an exhaust allowing for the exit of the gas from the elongated compartment, and a piston capable of moving within the elongated compartment between the first and second ends. The pulse of photonic energy at the focal point heats the gas and causes a corresponding expansion of the gas in the elongated compartment, driving the piston toward the second end of the elongated compartment, where the piston movement can be translated into motive force. The same principle can work with a rotary chamber, or a dual chambered linear system.