Demonstration of a pulsing liquid hydrogen/liquid oxygen thruster

Successful operation of a pulsing liquid hydrogen/liquid oxygen attitude control propulsion system thruster (1250 lb sub f) at cryogenic inlet conditions while maintaining high specific impulse and low impulse bit capability was demonstrated. Significant technical advances and departures from conventional injector design practices were necessary in order to achieve an operable thruster. These advancements were achieved through extensive analyses of heat transfer and injector manifold priming that established the baseline feasibility for an actual hardware design. The primary subject of this paper is the result of experimental evaluation of the 45 R hydrogen inlet temperature injector concept. The test matrix consisted of 66 hot firing tests in a heat sink thrust chamber

Ultra-Low-Power Superconductor Logic

We have developed a new superconducting digital technology, Reciprocal Quantum Logic, that uses AC power carried on a transmission line, which also serves as a clock. Using simple experiments we have demonstrated zero static power dissipation, thermally limited dynamic power dissipation, high clock stability, high operating margins and low BER. These features indicate that the technology is scalable to far more complex circuits at a significant level of integration. On the system level, Reciprocal Quantum Logic combines the high speed and low-power signal levels of Single-Flux- Quantum signals with the design methodology of CMOS, including low static power dissipation, low latency combinational logic, and efficient device count.Comment: 7 pages, 5 figure

Evaluation and demonstration of the use of cryogenic propellants /oxygen/hydrogen/ for reaction control systems. Volume 2 - Experimental evaluations and demonstration Final report

Evaluation and demonstration of cryogenic propellant /oxygen-hydrogen/ use for spacecraft reaction control system

Crystal-field splittings in CeX (X= N, P, As, Sb, Bi) compounds

The unusual and interesting physical properties of rare earth intemetallic compounds have their origin in the combination of strongly correlated 4f states and their hybridization with the conduction electron sea, which gives rise to their complex low temperature Kondo behavior. In particular, Ce compounds are very sensitive to the crystalline and chemical environment, as compared to other rare earth systems. The interaction of the 4f state with the conduction band plays an important role in the determination of the different magnetic, structural and transport properties of these systems. Among the cerium compounds, those of the type CeX, which crystallize in the rock salt structure, exhibit extremely unusual magnetic properties. By making use of the mixed LDA-NCA calculation technique we analyse the crystal-field splittings of CeX compounds (X=N, P, As, Sb, Bi). The obtained ab-initio hybridization functions are taken as imputs to calculate the crystal-field splittings within NCA (non crossing approximation) and the tendencies are contrasted with experiments. KEY WORDS: Highly correlated systems, crystal fields, p-electron.Comment: 8 pages, 2 figure

Trailing Edge Noise Reduction by Passive and Active Flow Controls

This paper presents the results on the use of porous metal foams (passive control) and dielectric barrier surface plasma actuations (active control) for the reduction of vortex shedding tonal noises from the nonflat plate type trailing edge serration in a NACA0012 airfoil previously discussed in Chong et al. (AIAA J. Vol. 51, 2013, pp. 2665-2677). The use of porous metal foams to fill the interstices between adjacent members of the sawtooth can almost completely suppress the vortex shedding tonal noise, whilst the serration effect on the broadband noise reduction is retained. This concept will promote the nonflat plate type serrated trailing edge to become a genuine alternative to the conventional flat plate type serrated trailing edge, which is known to have drawbacks in the structural stability, aerodynamic performances and implementation issues. For the plasma actuators, configuration which produces electric wind in a tangential direction is found to be not very effective in suppressing the vortices emanated from the serration blunt root. On the other hand, for the plasma configuration which produces electric wind in a vertical direction, good level of vortex shedding tonal noise reduction has been demonstrated. However, the self noise produced by the plasma actuators negates the noise benefits on the tonal noise reduction. This characteristic illustrates the need to further develop the plasma actuators in a two pronged approach. First is to increase the electric wind speed, thereby allowing the plasma actuators to be used in a higher free jet velocity which naturally produces a larger level of jet noise. Second, the self noise radiated by the plasma actuators should be reduced

Coherent Dipole Modes for Multiple Interaction Regions

In the Large Hadron Collider (LHC) two proton beams of similar strength will collide at several interaction points. For a single interaction point it is known that the head-on collision of two equally strong beams with the same betatron tune, excites two coherent dipole modes whose frequencies are different from the frequencies of oscillation of individual particles in the beam. Because of this frequency difference Landau damping does not act on the dipole modes and the beams can be unstable. In this paper we extend these studies to several interaction points and explore the possibility of cancellation of the dipole coherent modes by carefully adjusting the phase difference between the beams from one collision to the next. We also study the collision of the two beams with LHC optics V 6.1. Special attention should be paid to coherent resonances that are excited due to local phase advance correlations. It will be shown also that a tune split of 0.03 between the two beams suppresses these coherent dipole modes

A Prototype ATM Network for Real Time Control of the LHC

The LHC accelerator aims at injecting, accelerating and colliding beams with very well controlled beam parameters (e.g. momentum, orbit, tune and chromaticity). This is a non-trivial task since the super conducting main bending magnets will generate field errors with dynamic effects that may result in beam loss. To overcome this problem, real time control of beam parameters via the Power Converters has been proposed. This requires site wide deterministic communication of control data. In this paper we will outline some aspects of a prototype deterministic network for the LHC with a core based on ATM (Asynchronous Transfer Mode) communication technology