Thrust augmentation is usually needed for a short time period at (1) takeoff, (2) climb, (3) combat, and (4) high speed performance. Thrust augmentation allows us to avoid using a bigger (and heavier) engine that would penalize the performance of the aircraft when the additional thrust is not necessary. In other words, instead of utilizing a heavier and more powerful engine whose maximum power is only needed for a short period of time, it is often better to use a smaller engine that produces the required short-duration thrust by power augmentation. This section presents three methods of thrust augmentation: (1) water injection, (2) afterburning, and (3) inter-turbine combustion.

So far in this book, the emphasis has been on the role of psychological constraints on individual decision makers. In many areas of political science, however, theories deal with interactions between states or within a government bureaucracy, not the multitudes who live within a nation’s borders. The literature, in other words, treats states as unitary actors. In nearly every case of national level decision making, however, we see very interesting dynamics when we look a little closer. We review the challenge presented by principal-agent problems that are common in large and complex organizations such as national governments. BPS helps us understand a host of these influences on state level decision-making, including domestic public opinion, bureaucratic norms and practices, organizational constraints, advisory group structures, and the dynamics of group decision-making, including groupthink and polythink.

Theories of democracy all insist on some basic conditions in order for citizens to hold their elected officials accountable. One of the first ones to mention is an openness to new information about the world that might influence beliefs about a politician’s performance, character, intelligence and the like. In recent decades, BPS has discovered that this basic assumption is regularly violated. Citizens and elites often resist new and credible information in favor of their existing beliefs and viewpoints even when they would greatly benefit from updating those stands. In this chapter, we review a related set of theories captured under the umbrella of motivated reasoning that attempts to understand why, exploring the role of cognitive dissonance, self-esteem, and group identity in shaping individuals’ goals when processing information. While the field has no concrete answers yet, we at least have begun to estimate the often dire consequences of arguing from our existing attitudes to our perceptions of the world – top-down processing – instead of the other way around.

Combustion is the process that heats the working fluid in a jet engine. Combustion is a particular chemical reaction that has the following specific characteristics: (1) it is exothermic, (2) it is a fast oxidation of the combustion mixture, and (3) it is associated by light emission. The majority of chemical reactions take place in the flame, which is the region where the oxidation is visible.

Let us consider the forces that act on a small parcel of fluid in a fluid flow. There are two types:

1. 1. External or body forces, these may be due to gravity or external electromagnetic fields. They exert a force per unit volume on the continuum.

2. 2. Surface or stress forces, these are forces, molecular in origin, that are applied by the neighbouring fluid across the surface of the fluid parcel.

This chapter presents a thermodynamic analysis of various types of jet engines. The general thrust equation, introduced based on simple reasoning in , is derived using a rigorous approach based on mass and momentum conservation equations. The performance parameters needed to evaluate propulsion systems are presented next. The Brayton cycle, the ideal cycle of a jet engine, is then discussed. The assumptions of the Brayton cycle are gradually relaxed, and the real cycles of turbojet, turbofan, turboprop/turboshaft and ramjet engines are subsequently presented.