Le. Thode et al., VORTEX FORMATION AND STABILITY IN A SCALED GAS-CORE NUCLEAR ROCKET CONFIGURATION, Journal of propulsion and power, 14(4), 1998, pp. 530-536
Realistic interplanetary space exploration depends critically upon the
development of a high-specific-impulse propulsion system. Previous st
udies indicate that the specific impulse of an open-cycle gas-core nuc
lear rocket (OCGCNR) might approach 3000 s, Although the OCGCNR is dec
eptively simple in concept, it will be difficult to develop in practic
e because the core is a uranium plasma that must be nearly totally con
fined. Before constructing a more comprehensive model for this engine,
there is a requirement to understand the limits of present full-scale
simulation models and recent scaled experiments. In this scoping stud
y we have used a two-dimensional, axisymmetric, finite difference code
to investigate the formation and stability of a recirculation region
observed in a scaled experiment, It has been proposed that such a reci
rculation region, or vortex, might provide improved confinement of the
uranium fuel. Our simulation results indicate that a more comprehensi
ve model must treat the rocket nozzle in a self-consistent fashion to
properly calculate the confinement of the uranium plasma. Under condit
ions that lead to vortex formation, the position of the vortex depends
upon the inlet geometry and injection velocity, the nozzle position a
nd subsonic convergence angle, the base-bleed injection rate, and turb
ulence. With a large base-bleed injection rate, a vortex forms but is
then swept away through the nozzle, a result that resolves an inconsis
tency between a full-scale engine simulation model and recent scaled e
xperiments.