If a single person were to die in service, then there would only be a lump sum, either to the estate or to someone who had been nominated. Neither scheme pays out if there is no dependant, apart from the lump sum. The amount of that lump sum is a calculation based on the amount of salary they were paid and how much service they'd already accrued. For example, in AFPS 05, the death-in-service lump sum is four times salary.
On March 26th, 2009. See this statement in context.