A rocket engine has sea-level specific impulse 210 s, throat area 0.005 m², characteristic velocity 1900 m/s and chamber pressure 50 bar. With g = 9.8 m/s², find sea-level thrust in kN, to 1 decimal place.
Characteristic velocity is $c^*=p_cA_t/\dot m$. Hence mass flow is $\dot m=(50\times10^5)(0.005)/1900=13.1579$ kg/s. Sea-level thrust follows from $F=I_{sp}\dot m g=210(13.1579)(9.8)=27078.95$ N = 27.1 kN. The specified sea-level impulse already includes the sea-level pressure effect.
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