In the early 1960s, Werner Von Braun and others recognized the need for a n
uclear rocket for sending humans to Mars. The great distances, the intense
radiation levels, and the physiological response to zero gravity all suppor
t the concept of using a nuclear rocket to decrease mission time. These sam
e needs have been recognized in later studies and, especially, in the Space
Exploration Initiative in 1989. One of the key questions that has arisen i
n later studies, however, is the ability to test a nuclear rocket engine in
the current societal environment. Unlike the Rover/Nuclear Engine for Rock
et Vehicle Applications programs in the 1960s, the rocket exhaust can no lo
nger be vented to the open atmosphere. As a consequence, previous studies h
ave examined the feasibility of building a large-scale version of the Nucle
ar Furnace Scrubber that was demonstrated in 1971. We have investigated an
alternative that would deposit the rocket exhaust along with any entrained
fission products directly into the ground. The subsurface active filtering
of exhaust concept would allow variable-sized engines to be tested for long
times at a modest expense. A system overview, results of preliminary calcu
lations, and current status of a proof-of-concept demonstration are present
ed.