Altitude Performance and Operational Characteristics of YJ71-A-7 Turbojet Engine

Altitude performance of a YJ71-A-7 turbojet engine, with afterburner inoperative, was determined in the NACA Lewis altitude wind tunnel over a wide range of flight conditions. Engine speed and exhaust-nozzle area were controlled independently during this investigation. The variation of corrected values of air flow, net thrust, and fuel flow with corrected engine speed was not defined by a single curve with changes in altitude at given flight Mach number. Changes in altitude had very little effect on minimum specific fuel consumption at altitudes up to 45,000 feet. There is one exhaust-nozzle schedule that is nearly optimum for all flight conditions. Performance calculated from pumping characteristics agreed with experimental values and can therefore be used to extend engine performance data

Effect of Inlet-air-flow Distortions on Steady-state Performance of J65-B-3 Turbojet Engine

The effects of inlet-air-flow distortions on the performance of the J65-B-3 turbojet engine were determined over a range of altitudes from 15,000 to 50,000 feet at a flight Mach number of 0.8. Radial inlet-air-flow distortions apparently do not affect the radial distribution of pressure after the first few compressor stages, while the circumferential inlet-air-flow distortion carried completely through the engine. For the distortions investigated, at rated exhaust-gas temperature and fixed-area exhaust-nozzle operation, the primary effect of the radial inlet-air-flow distortions was to reduce the engine air flow, and the primary effect of the circumferential distortion was to impose a temperature profile on the turbine, both resulting in reduction of thrust

Performance of the Components of the XJ34-WE-32 Turbojet Engine over a Range of Engine and Flight Conditions

Performance of the compressor, combustor, and turbine operating as integral parts of the XJ34-WE-32 turbojet engine was determined in the Lewis altitude wind tunnel over a range of altitudes from 5000 to 55,000 feet and flight Mach numbers from 0.28 to 1.05. Data were obtained for each of four exhaust-nozzle areas and are presented in graphical and tabular form

Performance of a turbojet engine with adjustable first-stage turbine stator and variable-area exhaust nozzle

The performance of a turbojet engine with a two-stage turbine, an adjustable first-stage turbine stator, and a variable-area exhaust nozzle was investigated at selected constant engine speeds and two simulated flight conditions. For the particular component characteristics of the engine investigated, little improvement in thrust levels of interest by use of an adjustable rather than an optimum fixed first-stage turbine stator

Fluctuations and Correlations in Lattice Models for Predator-Prey Interaction

Including spatial structure and stochastic noise invalidates the classical Lotka-Volterra picture of stable regular population cycles emerging in models for predator-prey interactions. Growth-limiting terms for the prey induce a continuous extinction threshold for the predator population whose critical properties are in the directed percolation universality class. Here, we discuss the robustness of this scenario by considering an ecologically inspired stochastic lattice predator-prey model variant where the predation process includes next-nearest-neighbor interactions. We find that the corresponding stochastic model reproduces the above scenario in dimensions 1< d \leq 4, in contrast with mean-field theory which predicts a first-order phase transition. However, the mean-field features are recovered upon allowing for nearest-neighbor particle exchange processes, provided these are sufficiently fast.Comment: 5 pages, 4 figures, 2-column revtex4 format. Emphasis on the lattice predator-prey model with next-nearest-neighbor interaction (Rapid Communication in PRE

Switchable collective pinning of flux quanta using magnetic vortex arrays

We constructed a superconducting/ferromagnetic hybrid system in which the ordering of the pinning potential landscape for flux quanta can be manipulated. Flux pinning is induced by an array of magnetic nanodots in the magnetic vortex state, and controlled by the magnetic history. This allows switching on and off the collective pinning of the flux-lattice. In addition, we observed field-induced superconductivity that originates from the annihilation of flux quanta induced by the stray fields from the magnetic vortices.Comment: PDF file 18 pages including 5 figures, accepted for publication in Phys. Rev.

The Enjoyment and Acquisition of Resources in Outer Space

In their interactions in the larger arena, states and their surrogates may be observed to employ many different types of resources as bases of power and to make claims of many varying degrees in comprehensiveness of authority and in scope and duration of control over such resources. The more important resources so employed and subjected to claim include, apart from manpower, not only the land masses, in all their protean forms, but also the oceans, air space, outer space, polar areas, rivers and so on. Some of these resources, such as the oceans, air space over the oceans, and international rivers, which experience has demonstrated to admit of a high degree of shared use by reasonable mutual accommodation, have been generally regarded as not being subject to exclusive appropriation by particular states, and the only claims which states have reciprocally honored in traditional international law have been those asserting shared access and requiring reasonable accommodation among users. Other resources, such as the land masses and closely proximate waters and air space, have commonly been regarded as admitting only in modest degree of shared use and competence, and states have reciprocally honored each other\u27s claims to a most comprehensive and continuing, exclusive competence over such resources; indeed the very conception of the contemporary state embodies, as is well known, this high degree of exclusivity in the competence of a territorially organized group. The policies followed by the general community in this allocation of resources between inclusive and exclusive authoritative control have, building upon the experience that inclusive use and competence most often achieve the greatest production and widest distribution of goods and services for the benefit of all, established a very strong presumption in favor of the inclusive control of sharable resources, with exclusive control being protected only when it can be shown to contribute most to common interest

NACA Research Memorandums

Report presenting data to determine the component and overall engine performance up to an altitude limit for the J71-A-11 (600-B36) turbojet engine. Engine operation using JP-4 fuel at Mach number 0.8 was satisfactory up to an altitude of about 60,000 to 65,000 feet, and engine operation with marginal combustion stability was maintained to an altitude of about 80,000 feet. Results regarding the altitude operating limits, component performance, overall engine performance, contribution of individual component losses to overall engine performance losses, exhaust-nozzle-area requirements, and altitude performance at rated engine conditions are provided