"Yeah, you always run that program," Van told him. "But SD-SURF was written in FORTRAN way back in 1983. So SD-SURF treats the spacecraft’s surface contours as a faceted geometry. That simulation’s not entirely accurate, because you get these peaks and waves of flux and probability surfaces that are artifacts produced by granularity in the model. That’s due to the way the subroutine interrogates the ballistic limit surface . . ." Van’s voice trailed off. Hickok and Wessler were both staring at him blankly. He had completely lost them.