Sunday, October 4, 2015

Book Review: Hypersonic Airbreathing Propulsion

William H. Heiser and David T. Pratt
Hypersonic Airbreathing Propulsion
Washington, D.C.: American Institute of Aeronautics and Astronautics, 1994
Category: Aerospace Engineering

Rating: 5-Stars

This is one of those engineering texts that I wish they had had when I was in school.  Heiser and Pratt's Hypersonic Airbreathing Propulsion picks up where John Bertin's Hypersonic Aerothermodynamics leaves off, extending the basic concepts of hypersonic fluid dynamics to explore how they impact the operation of the propulsion system.  This volume explores the unique operating conditions and physics behind combined-cycle engines, as well as ramjet and scramjet operation.

The challenges of these flight conditions are unique to high speed flight.  Inlet losses that might have been tolerable for a "supersonic" aircraft at Mach 2, can become unacceptable to an aircraft at Mach 5.  A combustion system that was ruled by questions of mixing, burner efficiencies and minute pressure losses in subsonic combustion, becomes challenged by chemical kinetics and the brief residence time during supersonic combustion.  Moreover, even if these obstacles can be addressed, the supersonic combustion process is subject to the risk of thermal choking - wherein the addition of heat energy actually reduces the the Mach number of the flow, threatening to choke the burner and introduce a normal shock wave that could be catastrophic to the aircraft and engine.

For those who have been privileged to have explored this region of flight, or even for those who might hope to one day have that experience, this textbook is a doorway into the challenges of this unique design space.

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