3,793 research outputs found
Propellant transfer: Attached depot
Propellant transfer at an attached depot involves: (1) resupply tankers (dedicated launch from the ground or scavenging from the external tank) to resupply the depot; (2) depot storage and supply tanks (attached, free-flyer, or tethered) from which liquid hydrogen and liquid oxygen are transferred to fill the space-based OTV; and (3) the space-based OTV which is resupplied with cryogens from the depot. Liquid storage and supply, thermal control, and transfer/resupply requirements for an attached depot are listed, and technologies defined. The specific fluid management elements and approaches for an attached depot are enumerated. The cryogenic fluid management facility (CFMF) shuttle attached-payload test bed, scheduled for a mid-1988 first launch, is expected to provide much of the needed technology
String theory on and the symmetric orbifold of Liouville theory
For string theory on AdS with pure NS-NS flux a complete set of DDF
operators is constructed, from which one can read off the symmetry algebra of
the spacetime CFT. Together with an analysis of the spacetime spectrum, this
allows us to show that the CFT dual of superstring theory on for generic NS-NS flux is the symmetric
orbifold of Liouville theory. For the case
of minimal flux (), the Liouville factor disappears, and we just obtain
the symmetric orbifold of , thereby giving further support to a
previous claim. We also show that a similar analysis can be done for bosonic
string theory on .Comment: 33+10 page
Strings on
String theory on with pure NS-NS flux and minimal flux through one of the two 's is studied from a world-sheet perspective. It is shown that the
spacetime spectrum, as well as the algebra of spectrum generating operators,
matches precisely that of the symmetric orbifold of in the large limit. This gives strong support for the
proposal that these two descriptions are exactly dual to one another.Comment: 25+23 page
Multiple jet study data correlations
Correlations are presented which allow determination of penetration and mixing of multiple cold air jets injected normal to a ducted subsonic heated primary air stream. Correlations were obtained over jet-to-primary stream momentum flux ratios of 6 to 60 for locations from 1 to 30 jet diameters downstream of the injection plane. The range of geometric and operating variables makes the correlations relevant to gas turbine combustors. Correlations were obtained for the mixing efficiency between jets and primary stream using an energy exchange parameter. Also jet centerplane velocity and temperature trajectories were correlated and centerplane dimensionless temperature distributions defined. An assumption of a Gaussian vertical temperature distribution at all stations is shown to result in a reasonable temperature field model. Data are presented which allow comparison of predicted and measured values over the range of conditions specified above
The Worldsheet Dual of the Symmetric Product CFT
Superstring theory on with
the smallest amount of NS-NS flux (`') is shown to be dual to the
spacetime CFT given by the large limit of the free symmetric product
orbifold . To define the worldsheet theory at
, we employ the hybrid formalism in which the part is described by the WZW model (which is
well defined). Unlike the case for , it turns out that the string
spectrum at does {\it not} exhibit the long string continuum, and
perfectly matches with the large limit of the symmetric product. We also
demonstrate that the fusion rules of the symmetric orbifold are reproduced from
the worldsheet perspective. Our proposal therefore affords a tractable
worldsheet description of a tensionless limit in string theory, for which the
dual CFT is also explicitly known.Comment: 29+24 page
A holographic dual for string theory on
The CFT dual of string theory on is conjectured to be the symmetric orbifold
of the theory, provided that one of the two
quantum numbers is a multiple of the other. We determine the BPS spectrum of
the symmetric orbifold in detail, and show that it reproduces precisely the BPS
spectrum that was recently calculated in supergravity. We also determine the
BPS spectrum of the world-sheet theory that is formulated in terms of WZW
models, and show that, apart from some gaps (which are reminiscent of those
that appear in the corresponding calculation), it also
reproduces this BPS spectrum. In fact, the matching seems to work as well as
for the familiar case, and thus our results give strong support
for this proposal.Comment: 41 pages, 2 figure
Higher spin algebras and large holography
A new family of higher spin algebras that arises upon restricting matrix
extensions of is found. We identify coset CFTs
realising these symmetry algebras, and thus propose new higher spin-CFT dual
pairs. These higher spin theories arise naturally as a subsector of string
theory on for
specific ratios of the radii of the two spheres.Comment: 22 page
Research in the development of an improved multiplier phototube Final report
Counting efficiency, noise factor measurement, dark noise, gain and counting rate, optical enhancemen
Conceptual design and analysis of orbital cryogenic liquid storage and supply systems
A wide variety of orbital cryogenic liquid storage and supply systems are defined in NASA and DOD long-range plans. These systems include small cooling applications, large chemical and electrical orbit transfer vehicles and supply tankers. All have the common requirements of low-g fluid management to accomplish gas-free liquid expulsion and efficient thermal control to manage heat leak and tank pressure. A preliminary design study was performed to evaluate tanks ranging from 0.6 to 37.4 cu m (22 to 1320 cu ft). Liquids of interest were hydrogen, oxygen, methane, argon and helium. Conceptual designs were generated for each tank system and fluid dynamic, thermal and structural analyses were performed for Shuttle compatible operations. Design trades considered the paradox of conservative support structure and minimum thermal input. Orbital performance and weight data were developed, and a technology evaluation was completed
Transient heat and mass transfer analysis of supercritical cryogenic storage systems with spherical static heaters Final report
Transient heat and mass transfer analysis of supercritical cryogenic storage systems with spherical static heaters by computer progra
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