In most chemical propulsion systems, heat addition occurs at near constant pressure (through there is usually some pressure drop). Advanced propulsion concepts are currently under investigation to replace the constant pressure heat addition with near-constant volume heat addition. Parts (b) and (c) are aimed at helping understand why that concept is attractive.

(a) Draw the constant pressure heating process on a T-s diagram, and show mathematically that the constant P line must be concave upward for a perfect gas.

(b) Starting at the same initial condition as (a), draw a line of constant-volume that achieves the same final enthalpy on the T-s diagram.

(c) Show mathematically how lines of constant volume must be steeper in slope than lines of constant pressure on a T-s diagram.