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This paper explores some of the many considerations which enter into the choice of a specific spacecraft propulsion system for a particular application. The environment and its influence on propulsion requirements are discussed in general terms, characteristics of several propellant combinations are presented and an example of a typical ambitious mission is used. ...A general conclusion is that the state of the art of spacecraft propulsion technology must advance on a broad front in the time period prior to project definition in order to provide the technological options which allow significant optimization of the complete project propulsion system. ...A general conclusion is that the state of the art of spacecraft propulsion technology must advance on a broad front in the time period prior to project definition in order to provide the technological options which allow significant optimization of the complete project propulsion system.

Mars landing vehicle descent propulsion is discussed in the light of the constraints of the mission, the environment, and the interfacing functions. ...The presence of a largely undefined, tenuous atmosphere is shown to produce a great variability of initial and boundary conditions for the propulsion phase of descent. The mission provides numerous subtle constraints of formidable importance to the propulsion implementation. ...The mission provides numerous subtle constraints of formidable importance to the propulsion implementation. The current requirement for prelaunch, in-situ, thermal sterilization is paramount among these.

THE NUCLEAR turboelectric ion propulsion system operates as follows: 1. A nuclear reactor supplies thermal energy to a vapor boiler. 2. ...Electric propulsion systems can be used in a wide variety of space missions, including satellite sustainers, lunar cargo transport, and interplanetary missions.*

This paper reviews a recent internal study by Pratt & Whitney to define the optimum propulsion system characteristics for a commercial transport designed to fly at Mach 0.95. The impact on aircraft gross weight of propulsion cycle characteristics such as bypass ratio, overall pressure ratio, turbine temperature, nacelle weight, and drag as well as the important criteria of noise is reviewed. ...The impact on aircraft gross weight of propulsion cycle characteristics such as bypass ratio, overall pressure ratio, turbine temperature, nacelle weight, and drag as well as the important criteria of noise is reviewed.

An aircraft propulsion system for Mach .6 flight is being developed which utilizes two turboshaft engines driving a pusher propeller through driveshafts and a combining gearbox.

The program is being conducted at Rocketdyne, a division of North American Rockwell Corporation, under the sponsorship of the Air Force Rocket Propulsion Laboratory under Contract F04611-67-C-0116. This paper summarizes the accomplishments of the program to date, and describes the engine system and its possible application to the orbit-to-orbit shuttle (OOS).

This makes atomic energy attractive for aircraft propulsion, where it could combine high performance with large payload and long range. Chief obstacles in design of an atomic aircraft engine are development of light-weight shielding against deadly radiations; adequate cans to retain radioactive fission products; a pile capable of operating at high temperature and high thermal stresses; and a safe, flexible control mechanism.

These crew safety requirements impose many unusual constraints that are not required in launch vehicle or unmanned propulsion system designs. These requirements and their effects on design and operation are discussed and the systems operational experience on Apollo models are presented.

This paper will identify some of the primary propulsion integration problems for high performance aircraft at transonic speeds, and demonstrate several methods for reducing or eliminating the undesirable characteristics, while enhancing configuration effectiveness.

This paper presents the results achieved during the first year of this Atlas Propulsion Diagnostics Program and discusses the goals, approach, and accomplishments of the effort.

The continuing requirement for weapon systems capable of efficient operation over a wide range of altitude, Mach number, and power setting emphasizes the importance of propulsion system off-design performance. This paper illustrates the effect of installation losses on this off-design performance and considers some of the limits on usable performance imposed by stability considerations.

General Electric is conducting a Propulsion Study for NASA as part of the Small Transport Advanced Technology (STAT) program. The General Electric CT7 is used as the current modern turboprop engine baseline.

The prop-fan propulsion system is being investigated as part of the NASA Aircraft Energy Efficiency program which includes both analytical studies and experimental tests.

It is compared with the chemical rocket and the nuclear turboelectric ion propulsion system. In developing the concept for this low-power rocket, NASA engineers concentrated on attaining low weight and high hydrogen temperature, and on solving problems concerned with automatic control and operation of high-temperature reactors.

A unique propulsion system is being developed for the Space Shuttle Orbiter utilizing airbreathing engines to provide a means for horizontal flight testing and ferrying the Orbiter within the contiguous United States. ...The airbreathing engine arrangement which has resulted, while employing conventional propulsion subsystems, still possesses installation problems because of the low ground clearance.

There are future military and commercial propulsion requirements, however, where the anticipated market may not be sufficiently large or firm to provide the basis for a new development, for example, a medium size commercial or military STOL aircraft.

A method that exploits certain properties of a recirculating gas has been investigated as a means of achieving a sustained accelerative vector force without either the expulsion of mass from or a reaction against an external mass by the accelerated body. A theory of operation is presented that defines the capabilities and limitations of the method, and which has resulted in functioning prototypes. The prototype devices require only a source of electric power and a means of cooling to achieve an internally generated, externally measurable accelerative vector force that is sustained for as long as power is supplied to the device.