2,714 research outputs found
Hypersonic Research Vehicle (HRV) real-time flight test support feasibility and requirements study. Part 2: Remote computation support for flight systems functions
The requirements are assessed for the use of remote computation to support HRV flight testing. First, remote computational requirements were developed to support functions that will eventually be performed onboard operational vehicles of this type. These functions which either cannot be performed onboard in the time frame of initial HRV flight test programs because the technology of airborne computers will not be sufficiently advanced to support the computational loads required, or it is not desirable to perform the functions onboard in the flight test program for other reasons. Second, remote computational support either required or highly desirable to conduct flight testing itself was addressed. The use is proposed of an Automated Flight Management System which is described in conceptual detail. Third, autonomous operations is discussed and finally, unmanned operations
Automated flight test management system
The Phase 1 development of an automated flight test management system (ATMS) as a component of a rapid prototyping flight research facility for artificial intelligence (AI) based flight concepts is discussed. The ATMS provides a flight engineer with a set of tools that assist in flight test planning, monitoring, and simulation. The system is also capable of controlling an aircraft during flight test by performing closed loop guidance functions, range management, and maneuver-quality monitoring. The ATMS is being used as a prototypical system to develop a flight research facility for AI based flight systems concepts at NASA Ames Dryden
From an automated flight-test management system to a flight-test engineer's workstation
The capabilities and evolution is described of a flight engineer's workstation (called TEST-PLAN) from an automated flight test management system. The concept and capabilities of the automated flight test management systems are explored and discussed to illustrate the value of advanced system prototyping and evolutionary software development
High-speed civil transport issues and technology program
A strawman program plan is presented, consisting of technology developments and demonstrations required to support the construction of a high-speed civil transport. The plan includes a compilation of technology issues related to the development of a transport. The issues represent technical areas in which research and development are required to allow airframe manufacturers to pursue an HSCT development. The vast majority of technical issues presented require flight demonstrated and validated solutions before a transport development will be undertaken by the industry. The author believes that NASA is the agency best suited to address flight demonstration issues in a concentrated effort. The new Integrated Test Facility at NASA Dryden Flight Research Facility is considered ideally suited to the task of supporting ground validations of proof-of-concept and prototype system demonstrations before night demonstrations. An elaborate ground hardware-in-the-loop (iron bird) simulation supported in this facility provides a viable alternative to developing an expensive fill-scale prototype transport technology demonstrator. Drygen's SR-71 assets, modified appropriately, are a suitable test-bed for supporting flight demonstrations and validations of certain transport technology solutions. A subscale, manned or unmanned flight demonstrator is suitable for flight validation of transport technology solutions, if appropriate structural similarity relationships can be established. The author contends that developing a full-scale prototype transport technology demonstrator is the best alternative to ensuring that a positive decision to develop a transport is reached by the United States aerospace industry
Autonomous aircraft initiative study
The results of a consulting effort to aid NASA Ames-Dryden in defining a new initiative in aircraft automation are described. The initiative described is a multi-year, multi-center technology development and flight demonstration program. The initiative features the further development of technologies in aircraft automation already being pursued at multiple NASA centers and Department of Defense (DoD) research and Development (R and D) facilities. The proposed initiative involves the development of technologies in intelligent systems, guidance, control, software development, airborne computing, navigation, communications, sensors, unmanned vehicles, and air traffic control. It involves the integration and implementation of these technologies to the extent necessary to conduct selected and incremental flight demonstrations
Numerical evaluation of oscillatory integrals via automated steepest descent contour deformation
Steepest descent methods combining complex contour deformation with numerical
quadrature provide an efficient and accurate approach for the evaluation of
highly oscillatory integrals. However, unless the phase function governing the
oscillation is particularly simple, their application requires a significant
amount of a priori analysis and expert user input, to determine the appropriate
contour deformation, and to deal with the non-uniformity in the accuracy of
standard quadrature techniques associated with the coalescence of stationary
points (saddle points) with each other, or with the endpoints of the original
integration contour. In this paper we present a novel algorithm for the
numerical evaluation of oscillatory integrals with general polynomial phase
functions, which automates the contour deformation process and avoids the
difficulties typically encountered with coalescing stationary points and
endpoints. The inputs to the algorithm are simply the phase and amplitude
functions, the endpoints and orientation of the original integration contour,
and a small number of numerical parameters. By a series of numerical
experiments we demonstrate that the algorithm is accurate and efficient over a
large range of frequencies, even for examples with a large number of coalescing
stationary points and with endpoints at infinity. As a particular application,
we use our algorithm to evaluate cuspoid canonical integrals from scattering
theory. A Matlab implementation of the algorithm is made available and is
called PathFinder
Gluino decays with heavier scalar superpartners
We compute gluino decay widths in supersymmetric theories with arbitrary
flavor and CP violation angles. Our emphasis is on theories with scalar
superpartner masses heavier than the gluino such that tree-level two-body
decays are not allowed, which is relevant, for example, in split supersymmetry.
We compute gluino decay branching fractions in several specific examples and
show that it is plausible that the only accessible signal of supersymmetry at
the LHC could be four top quarks plus missing energy. We show another example
where the only accessible signal for supersymmetry is two gluon jets plus
missing energy.Comment: 17 pages, 8 figures. Added references and minor typos and errors
corrected (no change in numerical results
On the maximal Sobolev regularity\ud of distributions supported by subsets of Euclidean space
Given a subset of with empty interior and an integrability parameter , what is the maximal regularity for which there exists a non-zero distribution in the Bessel potential Sobolev space H^{s,p (\R^n) that is supported in ? For sets of zero Lebesgue measure we show, using results on certain set capacities from classical potential theory, that the maximal regularity is non-positive, and is characterised by the Hausdorff dimension of , improving known results. We classify all possible maximal regularities, as functions of , together with the sets of values of for which the maximal regularity is attained, and construct concrete examples for each case.\ud
\ud
For sets with positive measure the maximal regularity is non-negative, but appears more difficult to characterise in terms of geometrical properties of . We present some partial results relating to the latter case, namely lower bounds on the maximal Sobolev regularity supported by certain fat Cantor sets, which we obtain both by capacity-theoretic arguments, and by direct estimation of the Sobolev norms of characteristic functions. We collect several results characterising the regularity that can be achieved on certain special classes of sets, such as -sets, boundaries of open sets, and Cartesian products, of relevance for applications in differential and integral equations
Acoustic scattering by impedance screens/cracks with fractal boundary: well-posedness analysis and boundary element approximation
We study time-harmonic scattering in () by a planar
screen (a "crack" in the context of linear elasticity), assumed to be a
non-empty bounded relatively open subset of the hyperplane
, on which impedance (Robin) boundary conditions
are imposed. In contrast to previous studies, can have arbitrarily
rough (possibly fractal) boundary. To obtain well-posedness for such
we show how the standard impedance boundary value problem and its associated
system of boundary integral equations must be supplemented with additional
solution regularity conditions, which hold automatically when
is smooth. We show that the associated system of boundary integral operators is
compactly perturbed coercive in an appropriate function space setting,
strengthening previous results. This permits the use of Mosco convergence to
prove convergence of boundary element approximations on smoother "prefractal"
screens to the limiting solution on a fractal screen. We present accompanying
numerical results, validating our theoretical convergence results, for
three-dimensional scattering by a Koch snowflake and a square snowflake
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