Aero Fact: Nozzle Expansion Ratio
Nozzle exit-to-throat area ratio controls exit pressure; over/under-expansion reduces efficiency off-design.
By AircoreDynamics •
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1 min read
Definition: Expansion ratio Ae/At sets exit pressure; off-design, over/under-expansion reduces efficiency.
Physics insight: Thrust peaks when Pe ≈ Pa; over-expansion can cause shocks and separation.
Example: Vacuum nozzles are inefficient at sea level; staged solutions mitigate.
F ≈ ṁ V_e + (P_e - P_a) A_e
Rules of thumb: Optimize average efficiency across the mission profile.
Common pitfalls: Underestimating structural vibration/shock loads.
References: Sutton; Huzel & Huang