Variable conductance heat pipes from the laboratory to space

Heat pipes were developed which can be used as (1) a variable conductance link between a heat source and sink which provides temperature stability; (2) a feedback control mechanism that acts to directly maintain the source at a constant temperature; (3) or as a thermal diode that allows heat to be transferred in one direction only. To establish flight level confidence in these basic control techniques, the Ames Heat Pipe Experiment (AHPE) was launched in August 1972 and the Advanced Thermal Control Flight Experiment (ATFE) is scheduled for launch in May 1973. The major efforts of the technology development, initial flight results of the AHPE, and ground test data of the ATFE are discussed

Heat pipes for spacecraft temperature control: An assessment of the state-of-the-art

Various heat pipe temperature control techniques are critically evaluated using characteristic features and properties, including heat transport capability, volume and mass requirements, complexity and ease of fabrication, reliability, and control characteristics. Advantages and disadvantages of specific approaches are derived and discussed. Using four development levels, the state of-the-art of the various heat pipe temperature control techniques is assessed. The need for further research and development is discussed and suggested future efforts are projected

Asymptotic solution of a model for bilayer organic diodes and solar cells

The current voltage characteristics of an organic semiconductor diode made by placing together two materials with dissimilar electron affinities and ionisation potentials is analysed using asymptotic methods. An intricate boundary layer structure is examined. We find that there are three regimes for the total current passing through the diode. For reverse bias and moderate forward bias the dependency of the voltage on the current is similar to the behaviour of conventional inorganic semiconductor diodes predicted by the Shockley equation and are governed by recombination at the interface of the materials. There is then a narrow range of currents where the behaviour undergoes a transition. Finally for large forward bias the behaviour is different with the current being linear in voltage and is primarily controlled by drift of charges in the organic layers. The size of the interfacial recombination rate is critical in determining the small range of current where there is rapid transition between the two main regimes. The extension of the theory to organic solar cells is discussed and the analogous current voltage curves derived in the regime of interest

A comprehensive computer program for predicting solar cell performance

Comprehensive computer program for predicting solar cell performanc

Glassiness in a model without energy barriers

We propose a microscopic model without energy barriers in order to explain some generic features observed in structural glasses. The statics can be exactly solved while the dynamics has been clarified using Monte Carlo calculations. Although the model has no thermodynamic transition it captures some of the essential features of real glasses, i.e., extremely slow relaxation, time dependent hysteresis effects, anomalous increase of the relaxation time and aging. This suggests that the effect of entropy barriers can be an important ingredient to account for the behavior observed in real glasses.Comment: 11 Pages + 3 Figures, Revtex, uufiles have been replaced since figure 2 was corrupted in the previous submissio

Incommensurate magnetic ordering in Cu2Te2O5X2Cu_2 Te_2 O_5 X_2 (X=Cl,Br) studied by neutron diffraction

We present the results of the first neutron powder and single crystal diffraction studies of the coupled spin tetrahedra systems {\CuTeX} (X=Cl, Br). Incommensurate antiferromagnetic order with the propagation vectors {\bf{k}_{Cl}}\approx[0.150,0.422,\half], {\bf{k}_{Br}}\approx[0.158,0.354,\half] sets in below $T_{N}$=18 K for X=Cl and 11 K for X=Br. No simple collinear antiferromagnetic or ferromagnetic arrangements of moments within Cu${}^{2+}$ tetrahedra fit these observations. Fitting the diffraction data to more complex but physically reasonable models with multiple helices leads to a moment of 0.67(1)$\mu_B$/Cu${}^{2+}$ at 1.5 K for the Cl-compound. The reason for such a complex ground state may be geometrical frustration of the spins due to the intra- and inter-tetrahedral couplings having similar strengths. The magnetic moment in the Br- compound, calculated assuming it has the same magnetic structure as the Cl compound, is only 0.51(5)$\mu_B$/Cu${}^{2+}$ at 1.5 K. In neither compound has any evidence for a structural transition accompanying the magnetic ordering been found

Comment on "Deuterium--tritium fusion reactors without external fusion breeding" by Eliezer et al

Inclusion of inverse Compton effects in the calculation of deuterium-deuterium burn under the extreme conditions considered by Eliezer et al. [Phys. Lett. A 243 (1998) 298] are shown to decrease the maximum burn temperature from about 300 keV to only 100--150 keV. This decrease is such that tritium breeding by the DD --> T + p reaction is not sufficient to replace the small amount of tritium that is initially added to the deuterium plasma in order to trigger ignition at less than 10 keV.Comment: 6 pages, 1 tabl

Rocket study of the X-ray background

The X-ray optical detection system flown on Aerobee 17.08 is described in detail, and the preliminary results of the 24 June 1971 flight are discussed. The optical design, fabrication and parabolic nature of the mirrors, effective aperture of mirror array, and X-ray detectors are considered. Preliminary analysis of data from the flight confirms the extended nature and complex structure of the X-ray source in Virgo. A core of X-ray emission is indicated which is approximately 0.5 deg in diameter and surrounded by an emitting region at least 2 deg across. The Virgo source spectrum is observed to have few low energy photons

An exactly solvable toy model that mimics the mode coupling theory of supercooled liquid and glass transition

A toy model is proposed which incorporates the reversible mode coupling mechanism responsible for ergodic-nonergodic transition with trivial Hamiltonian in the mode coupling theory (MCT) of structural glass transition. The model can be analyzed without relying on uncontrolled approximations inevitable in the current MCT. The strength of hopping processes can be easily tuned and the ideal glass transition is reproduced only in a certain range of the strength. On the basis of the analyses of our model we discuss about a sharp ergodic-nonergodic transition and its smearing out by "hopping".Comment: 5 pages, 2 ps-figures, inappropriate terms replace