Nuclear Propulsion Systems Research Articles

Orbital experimentation for advancing cryogenic technology.

Problem areas within cryogenic chemical and nuclear propulsion systems for space missions, noting available technology and limitations

On the radiation slip between absorbing-emitting regions with heat sources

SOME practical systems in which regions with sharply differing properties and energy sources are exchanging radiation are being extensively studied. Examples are “seeded” layers with flow and the various gaseous-core nuclear propulsion systems. Examination of these situations show that a discontinuity in temperature may exist in certain cases at the boundary between the regions. This is analogous in some ways to the often-noted temperature jump at the boundary ofa gas abutted by a solid surface [l-3]. Such slips occur only where radiation is considered independent of conduction or where very low densities are present in the gas.

Dynamics of Clustered Nuclear Engines

A short review is presented of investigations concerning clustering of multiple identical solid core nuclear engines in a polygon arrangment, for space propulsion. A unique aspect of nuclear engine clustering is the coupling between reactors due to the exchange of neutrons which propagate transients within the system. A method has been developed at Douglas for evaluating the reactivity coupling effect for various reactor types and cluster arrangements. The results are in good agreement with available experimental data. An analog model of a clustered nuclear propulsion system has been used for simulating the operating cycle, with emphasis on the inherent control offered by the presence of hydrogen in the reactor. Coupling effects during transients, including start-up, abnormal reactivity perturbations, and an engine-out event are the major points of interest.

A transpiration-cooled nozzle as applied to a gas-core nuclear propulsion system

The use of mass injection through a porous wall as a cooling technique for axisymmetric nozzles is investigated. The effect of homogeneous mass injection on the heat transfer in a turbulent, compressible boundary layer is analyzed, using an integral-momentum approach. Approximate formulations of the gaseous thermal radiative and recombination energy contributions are included in the analysis. Coolant requirements are determined for a conical nozzle associated with a 106 Ib-thrust gas-core system operating at a 300-atm chamber pressure. Hydrogen is assumed to be used for the propellant and coolant. Chamber temperatures range from 7500° to 20,000°R, and wall temperatures range from 2000° to 3000°R. The degradation of specific impulse, which is a result of expelling the coolant at a lower total temperature than that in the chamber, is found to be as high as 9% at 20,000°R for a wall temperature of 2000°R.

Highlights in Unconventional Nuclear Power and Propulsion Systems

The paper surveys several unconventional concepts of nuclear power and propulsion systems which have been proposed during recent years. The unconventional aspects of these concepts reside partly in their indicated performance capability and partly in the scanty discussion they received thus far by other workers in the field. It is the objective of this survey to bring these proposals to renewed attention and discussion among those concerned with progress in space power and propulsion systems. Beside the magneto hydro dynamics (MHD) accelerators, also included are electro gas dynamics (EGD) and fusion propulsion concepts whose indicated performance characteristics warrant a closer scrutiny because of their potential attractiveness for the future aerospace transportation systems.

Economy in Government Contracting. Atomic Energy Commission Experience

President Johnson has pledged that the executive branch be administered with the utmost thrift and frugality; that the Government will get a dollar's value for a dollar spent; and that the Government will set an example of prudence and economy.' Heads of departments and agencies, responding to this pledge, are undertaking affirmative action to carry out this request-including the initiation of cost reduction programs, the de-emphasis of cost-type contracting, and the re-emphasis of fixed-price and incentive-type contracting. Accordingly, there is occasion to examine carefully the experience of the Atomic Energy Commission (AEC) with regard to economy in contracting, and particularly in regard to the use of various forms and methods of contracting. In evaluating various forms and methods of contracting, there must be considered the whole of contracting used by the agency and indeed the organization and functions of the agency as a whole. What is desirable for one type of system may not work well for another; similarly, one form of contract may work well for one type of function or operation but may not work very well for another. In very broad terms, the AEC is responsible for a program of manufacturing fissionable material and atomic weapons; developing nuclear propulsion systems for naval vessels; conducting research and development aimed at improved weapons, more efficient production, generation of useful power from atomic energy, utilization of radioactive material for medical, biological, and health purposes; and regulating the peaceful uses of atomic energy. Thirteen Field Offices carry out the atomic energy program under the general direction and supervision of the AEC Headquarters office. Most AEC work is accomplished by contractors. There are more than I35,000 persons working directly in the program, of which approximately 7,0oo are AEC employees. The rest work for our contractors. At present, the AEC investment in plant, equipment, and real estate is approximately eight billion dollars, and operating costs are at an annual level of approximately $2.7 billion. These government-owned facilities are managed and operated for the AEC by contractors. Our operating contractors comprise a variety of industrial, academic, and not-for-profit organiza-

OPTIMIZATION CONSIDERATIONS OF ELECTRICAL SPACE ENGINES

OPTIMIZATION CONSIDERATIONS OF ELECTRICAL SPACE ENGINES

Stability and control of nuclear rocket propulsion

A systems treatment of the dynamic behavior of nuclear rocket propulsion systems is presented. This simplified analysis does represent the basic ideas of more detailed computer studies. Nuclear reactor systems for space propulsion are much faster than conventional reactor systems which complicates the controls problem. (The dynamics of chemical systems have been simpler in nature due to their speed of response.) One attractive solution, which uses the propellant reactivity, is discussed.

Correlation of Hydrogen Heat Transfer in Boiling and Supercritical Pressure States

The use of hydrogen as a working fluid in both chemical and nuclear propulsion systems necessitates convective heat transfer information over a broad range of fluid states. Current heat transfer correlation schemes available in the literature are discussed in terms of their applicability to hydrogen heat transfer. Similarities in the subcritical and supercritical (pressure) heat transfer mechanisms and associated experimental data are reported. Summarized are correlation schemes formulated from heated tube data which apply to: 1) film boiling of liquid hydrogen; 2) hydrogen at supercritical pressure just above and below critical temperature; and 3) low temperature hydrogen (150 to 250 deg R) above the critical pressure. Parts 1 and 2 have required correlation schemes that depart from the conventional convective pipe flow concepts. It does appear that the conventional pipe flow heat transfer theory can be applied to part 3. (auth)

Reliability Limitations on Electronics for Nuclear Propulsion and Space Power Systems

Although a large amount of data is available on the temperature and radiation effects on electronic components, it does not contain the necessary engineering information that can be found for the more conventional space electronics design. For nuclear applications, the electronics designer needs information on a much greater number of components because of the wide range of temperature and radiation environments. A coordinated development and reliability program should be started now to assure the usefulness of nuclear propulsion and space power by providing the necessary reliable components and the engineering design information required to design the electronic equipment.

Radiation Levels Governing Nuclear Roce Ground Instrumentation

A rocket vehicle with a nuclear propulsion system assumes the environment of the reactor: specifically, the high intensity neutron and gamma radiation fields. The rocket system considered here is a booster-type vehicle of approximately 1.25 million pounds. Reactor power requirements for the specified mission and the necessity of minimum shielding result in a neutron flux in excess of 6 × 1013 n/cm2-sec ten meters from the reactor core, and a gamma flux of approximately 1015 ?/cm2-sec at the same distance. The environment at the launch site is affected by intense gamma radiation from the reactor during reactor run-up, hold-down for systems check, and also for a short time after lift-off. In addition, there will be fission product release resulting in ground contamination, and gamma radiation in the air both vicinal to and remote from the launch site. Assuming that the reactor and booster vehicle are to be recovered, activation radiation induced in the structure, and fission product release from the shutdown reactor must be evaluated. The requirements for instrumentation around a nuclear rocket launch site are, indeed, many and diverse. The demands upon a monitoring and measurement system are constant at all times, and during nuclear operations are severe. Although the magnitudes of nuclear radiations shown here are prodigious, the problems presented by them are not insurmountable. This paper analyzes the various radiation environments, and outlines on-site and off-site radiation instrumentation requirements.

EXPERIMENTAL PROGRAM FOR A PLASMA PINCH SPACE ENGINE

EXPERIMENTAL PROGRAM FOR A PLASMA PINCH SPACE ENGINE