Locomotives can be of two types: diesel-electric and electric. The main components of a diesel-electric locomotive are the diesel engine, electric transmission equipment, auxiliary generating apparatus, traction motor blowers, traction motors, electrical controls, batteries, and braking systems. To measure performance of a diesel-locomotive, rail horsepower, engine indicated horsepower, drawbar horsepower, thermal efficiency, and adhesion are all important. As of the date of the book’s publication, diesel-electric locomotives dominate the market in the US, whereas electric locomotives have seen very limited use. The higher efficiency of diesel-electric locomotives and their ability to haul heavy cars make them a preferred choice for companies, even though many electric locomotives rely on the traction motors identical to those utilized on diesel-electric locomotives. Freight cars can have a variety of forms, with the most popular being box cars, covered hopper cars, open-top hopper cars, high-side gondola cars, bulkhead flat cars, tank cars, container cars, flat cars, depressed-center flat cars, and Schnabel cars. The efficiency of all freight cars usually depends on the quality of standard design components, such as suspension and wheel set, and some special-purpose components, such as coupler cushioning, lading restraint, covered hopper discharge gates, and coupling systems. As to passenger train sets, the most popular among them are diesel multiple units, electric multiple units, electric locomotive-hauled units, and diesel locomotive-hauled units. Depending on the application – subway, railway, street railway – passenger equipment can be heavy rail and light rail. In any case, the movement of locomotive vehicles is impossible without the track. Basic track structure consists of rail, tie plates, cross ties, fasteners, ballast, and subgrade. The distance between centers of the mainline track varies from state to state, but is never shorter than 3.6 meters. For a vehicle to be capable of moving on the track, vehicle-track interaction must exist. This interaction depends on how successfully the locomotive can overcome inherent and incidental resistance at the driving-wheel-rail interface.
Marine vehicles come in different platforms. The most common are displacement hull forms (used in catamarans and submarines), planing hull forms (used in yachts, racing craft and coastal patrol boats), and high-performance ships used for commercial and military purposes in the rogue seas. The platform notwithstanding, all vessels are kept afloat by a buoyant force, which is “equal to the weight of the volume of water displaced” (Tracy 40). The ability of a vessel to accomplish its mission is called seaworthiness. The seaworthiness of a particular vessel is contingent on its structure, stability, sea-keeping, resistance, and powering requirements. The constraints that marine engineers face are numerous. The most common and tricky can be divided into three categories: physical constraints related to the geometry of the hull forms, dynamic constraints related to the interaction of vehicles with the marine environment, and environmental constraints related to the discharge of refuse from the marine vehicles. The mission of the propulsion system is to integrate the power generator mover, the propulsor, the transmission and other shipboard systems with the vehicle’s hull to propel the vehicle as a sustained speed and ensure maneuvering capabilities. The choice of propulsion plants is usually limited to diesel engines, steam turbines and gas turbines, but they can be employed in various combinations. Among the most popular propulsors – the most important component of a vessel, perhaps – are screw propellers, vertical-axis propellers, controllable-pitch propellers, and water jets. Conventional propulsion is, however, insufficient to operate high-performance ships. This area of the industry is being constantly developed, as new supercargo ships require higher speed and cargo capacity.
Aeronautics is “the science and art of flight that includes the operation of heavier-than-air aircraft” (Jenkins 59). Aircraft are designed to operate in the standard and upper atmospheres. The standard atmosphere extends to 1,000 kilometers above the surface, while everything that that is above this altitude is the upper atmosphere. When an airfoil – that is, a structure with the curved surfaces used in wings, fins and tail-planes – is moved through the air, subsonic aerodynamic forces come into play. Once in the air, the quality of an aircraft is judged by its control, stability and flying qualities. A great deal depends on the prowess of a pilot, but the aircraft’s design is even more important. For example, an airplane is considered statically stable if airframe moments tend to return it to its original attitude after a disturbance. Unlike many other types of aircraft, “helicopters derive lift, propulsion force and control effect from adjustments in the blade angles of the rotor system” (Jenkins 72). When an aircraft travels at a subsonic, transonic or supersonic speed, shockwaves – that is, thin regions of the air through which physical properties of the air change – form on the air.
Stanford Fleeter commences the subsection on jet propulsion and aircraft propellers with a discussion of Newton’s laws of motion, which form the theoretical basis for all methods of propelling a body. Unlike in propeller propulsion, the propulsive matter during jet propulsion is ejected from within the propelled body in the form of the high-speed jets. To enable jet propulsion both within and beyond the earth atmosphere, there must be an exhaust jet with no atmospheric air. Jet-propulsion engines can be either air-breathing (ramjet engines and turbojet engines) or rocket (chemical rocket engines, nuclear heat-transfer rocket engines, and electric rocket engines). The propulsion element in any jet-propulsion engine is the exhaust nozzle. The speed at which energy is supplied to the exhaust nozzle is called the propulsion power. The thrust power (PT), as calculated in the equation below, is the speed at which the propulsion system does useful work. The function of the rocket motors in most applications is to produce a large thrust for a limited period. The mission of the aircraft propeller is to convert the torque – that is, the force that causes bodies to spin around an axle – supplied to it by an engine into the thrust for propelling an air vehicle.
PT = FV0
Astronautics is the science of designing, constructing and operating interplanetary and interstellar aircraft. The Shuttle thermal protection systems, consisting of several layers of insulation, are of paramount importance for this type of aircraft. Another big difference from other types of aircraft is that it takes extreme forces to propel a space vehicle from the launch pad, which presumes specific engineering solutions. Although launched by an external force, space vehicles have their own propulsion systems, which provide the maneuverability, range and speed of the vehicle. In the orbit-, lunar- and interplanetary-flight mechanics, engineers need to pay attention to the effects of the sun, planets and their moons on the transfer trajectories, for this can be decisive in the operation of the space vehicles. For example, those vehicles that penetrate the atmosphere of other planets need to be designed in such a way that they dissipate their energy before landing to avoid unpredicted mishaps. Regardless of their mission, all space vehicles need to be designed to maintain their angular orientation in space for successful operation. To this end, mechanics must properly set control, stability and attitude dynamics in a vehicle. When selecting materials for the aerospace applications, where demands are higher, the most commonly sought properties include density, elasticity, resistance to fatigue damage, strength-to-weight ratio, toughness at operating temperatures, and weldability. Depending on the environments of application, other properties and factors may be considered. In the high-pressure oxygen systems, for example, ignition-resistant materials are required. Regardless of the operational environments, all space vehicles need to have reliable shielding that can forestall shocks emanating from the impinging debris. Space vehicles are available in a variety of structures to satisfy the requirements of a specific mission. Among the most inflatable space structures for human habitation, for example, are portable hyperbaric chambers and TransHabs. To sustain human life in a space vehicle, engineers have to find solutions to the problem of replenishing the human-consumed substances on board and controlling the conditions of the environment.

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