Apparatus for and methods of rethermalizing a package of refrigerated or frozen food are disclosed. The first vortex is of fuel and combusted gases such that said fuel and combusted gases spiral away from a fuel inlet end towards an exhaust nozzle or gas outlet end of the reaction chamber. The walls cooperate to form a socket having an opening on the bottom, for receiving and closely fitting about the upper end portion of the ladder. The processing unit is also configured to cause the flight control unit to adjust a position of the flight control surfaces to minimize the error. One embodiment includes an aperture plate having at least elongated apertures and is moved between at least first and second positions that define different ion beam profiles. The wheel arch comprising an electrical circuit embedded within or installed on a surface of the wheel arch.