Characterization of Aerospace Vehicle Performance and Mission Analysis Using Thermodynamic Availability

Abstract

The fundamental relationship between entropy and aerospace vehicle and mission performance is analyzed in terms of the general availability rate balance between force-based vehicle performance, available energy associated with expended propellant, and the overall loss rate of availability, including the vehicle wake. The availability relationship for a vehicle is analytically combined with the vehicle equations of motion; this combination yields the balance between on-board energy rate usage and rates of changes in kinetic and potential energies of the vehicle and overall rate of entropy production. This result is then integrated over time for a general aerospace mission; as examples, simplified single-stage-to-orbit rocket-powered and air-breathing missions are analyzed. Examination of rate of availability loss for the general case of an accelerating, climbing aerospace vehicle provides a powerful loss superposition principle in terms of the separate evaluation and combination of loss rates for the same vehicle in cruise, acceleration, and climb. Rate of availability losses is also examined in terms of separable losses associated with the propulsion system and external aerodynamics. These loss terms are cast in terms of conventional parameters such as drag coefficient and engine specific impulse. Finally, rate losses in availability for classes of vehicles are described.

2D Flow Field Analysis by the Exergetic Method

“…Several authors have used this concept in order to evaluate the external aerodynamic behavior of flight vehicles [12][13][14][15]. One of most recent formulations is the one proposed by Arntz [3]: an exergy approach well suited for the analysis of CFD simulations and valid for compressible and incompressible flows.…”

Exergetic Drag Characteristic Curves

“…Several authors have used this concept to evaluate the external aerodynamic behavior of flight vehicles [13][14][15][16].…”

Detonation Engine Performance Comparison Using First and Second Law Analyses

“…With the given information for these performance cases, the wake exergy generation can be found by using either a rate balance equation or a control volume analysis. 3,22 Equation 12shows the exergy rate balance equation that can be written for the so-called flying engine with the entire specific thrust equation. Using this exergy rate balance equation shows that maximum performance indeed occurs at Ψ ≈ 2.3.…”

“…One proposed metric that has been used extensively in other industries is the exergy analysis method, 1 whereby all losses to aircraft can be quantified using entropy and the Second Law of thermodynamics. 2,3 Exergy (also known as availability) analysis can be used to maximize the work output of aircraft over the varied conditions in a total mission. It can also be described as a method to minimize entropy production of a cycle.…”