Table: rocket_sfc
Columns: engine_type
scenario
sfc_in_lb_lbf_h
sfc_in_g_kn_s
specific_impulse_s
effective_exhaust_velocity_m_s

Question: What is the specific impulse for the engine with a scenario of sr-71 at mach 3.2 (wet)?
SQL: SELECT "specific_impulse_s" FROM rocket_sfc WHERE "scenario" = 'sr-71 at mach 3.2 (wet)'