A steady state planar solid oxide fuel cell (P-SOFC) based system operating on desulfurized JP-8 fuel was modeled using Aspen Plus simulation software for auxiliary and mobile power applications. An onboard autothermal reformer (ATR) employed to reform the desulfurized JP-8 fuel was coupled with the P-SOFC stack to provide for H-2 and CO as fuel, minimizing the cost and complexity associated with hydrogen storage. Characterization of the AIR reformer was conducted by varying the steam to carbon ratio (H2O/C) from 0.1 to 1.0 at different AIR operating temperatures (700-800 degrees C) while maintaining the P-SOFC stack temperature at 850 degrees C. A fraction of the anode recycle was used as the steam and heat source for autothermal reforming of the JP-8 fuel, intending to make the system lighter and compact for mobile applications. System modeling revealed a maximum net AC efficiency of 37.1% at 700 degrees C and 29.2% at 800 degrees C ATR operating temperatures, respectively. Parametric analyses with respect to fuel utilization factor (U-f) and current density (j) were conducted to determine optimum operating conditions. Finally, the P-SOFC based system was compared with a previously published [1] tubular solid oxide fuel cell based (T-SOFC) system to identify the relative advantages over one another. (C) 2013 Elsevier B.V. All rights reserved.