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NASA NTRS1993

Perspective on the National Aero-Space Plane Program instrumentation development

A review of the requirement for, and development of, advanced measurement technology for the National Aerospace Plane program is presented. The objective is to discuss the technical need and the program commitment required to ensure that adequate and timely measurement capabilities are provided for ground and flight testing in the NASP program. The scope of the measurement problem is presented, the measurement process is described, how instrumentation technology development has been affected by NASP program evolution is examined, the national effort to define measurement requirements and assess the adequacy of current technology to support the NASP program is discussed, and the measurement requirements are summarized. The unique features of the NASP program that complicate the understanding of requirements and the development of viable solutions are illustrated.

Bogue, Rodney K.↗

NASA NTRS1993

A perspective on the FAA approval process: Integrating rotorcraft displays, controls and workload

The FAA is responsible for making the determination that a helicopter is safe for IFR operations in the National Airspace System (NAS). This involves objective and subjective evaluations of cockpit displays, flying qualities, procedures and human factors as they affect performance and workload. After all of the objective evaluations are completed, and all Federal Regulations have been met, FAA pilots make the final subjective judgement as to suitability for use by civil pilots in the NAS. The paper uses the flying qualities and pilot workload characteristics of a small helicopter to help examine the FAA pilot's involvement in this process. The result highlights the strengths of the process and its importance to the approval of new aircraft and equipments for civil IFR helicopter applications. The paper also identifies opportunities for improvement.

Green, David L.↗

NASA NTRS1993

Computational Control Workstation: Users' perspectives

A Workstation has been designed and constructed for rapidly simulating motions of rigid and elastic multibody systems. We examine the Workstation from the point of view of analysts who use the machine in an industrial setting. Two aspects of the device distinguish it from other simulation programs. First, one uses a series of windows and menus on a computer terminal, together with a keyboard and mouse, to provide a mathematical and geometrical description of the system under consideration. The second hallmark is a facility for animating simulation results. An assessment of the amount of effort required to numerically describe a system to the Workstation is made by comparing the process to that used with other multibody software. The apparatus for displaying results as a motion picture is critiqued as well. In an effort to establish confidence in the algorithms that derive, encode, and solve equations of motion, simulation results from the Workstation are compared to answers obtained with other multibody programs. Our study includes measurements of computational speed.

Roithmayr, Carlos M.↗

NASA NTRS1993

Propagation issues for emerging mobile and portable communications: A systems perspective

The viewpoint of a system engineer regarding the format of propagation information and models suitable for the design of mobile and portable satellite communications systems for the following services: audio broadcast, two way voice, and packet data is presented. Topics covered include: propagation impairments for portable indoor reception in satellite communications systems; propagation impairments and mitigation techniques for mobile satellite communications systems; characterization of mobile satellite communications channels in the presence of roadside blockage when interleaving and FEC coding are implemented; characterization of short-term mobile satellite signal variations; and characterization of long-term signal variations.

Golshan, Nasser↗

NASA NTRS1993

New perspectives for high accuracy SLR with second generation geodesic satellites

This paper reports on the accuracy limitations imposed by geodesic satellite signatures, and on the potential for achieving millimetric performances by means of alternative satellite concepts and an optimized 2-color system tradeoff. Long distance laser ranging, when performed between a ground (emitter/receiver) station and a distant geodesic satellite, is now reputed to enable short arc trajectory determinations to be achieved with an accuracy of 1 to 2 centimeters. This state-of-the-art accuracy is limited principally by the uncertainties inherent to single-color atmospheric path length correction. Motivated by the study of phenomena such as postglacial rebound, and the detailed analysis of small-scale volcanic and strain deformations, the drive towards millimetric accuracies will inevitably be felt. With the advent of short pulse (less than 50 ps) dual wavelength ranging, combined with adequate detection equipment (such as a fast-scanning streak camera or ultra-fast solid-state detectors) the atmospheric uncertainty could potentially be reduced to the level of a few millimeters, thus, exposing other less significant error contributions, of which by far the most significant will then be the morphology of the retroreflector satellites themselves. Existing geodesic satellites are simply dense spheres, several 10's of cm in diameter, encrusted with a large number (426 in the case of LAGEOS) of small cube-corner reflectors. A single incident pulse, thus, results in a significant number of randomly phased, quasi-simultaneous return pulses. These combine coherently at the receiver to produce a convolved interference waveform which cannot, on a shot to shot basis, be accurately and unambiguously correlated to the satellite center of mass. This paper proposes alternative geodesic satellite concepts, based on the use of a very small number of cube-corner retroreflectors, in which the above difficulties are eliminated while ensuring, for a given emitted pulse, the return of a single clean pulse with an adequate cross-section.

Lund, Glenn↗

NASA NTRS1993

An initial perspective of S-asteroid subtypes within asteroid families

Many main belt asteroids cluster around certain values of semi-major axis (a), inclination (i), and eccentricity (e). Hirayama was the first to notice these concentrations which he interpreted as evidence of disruptions of larger parent bodies. He called these clusters 'asteroid families'. The term 'families' is increasingly reserved for genetic associations to distinguish them from clusters of unknown or purely dynamical origin (e.g. the Phocaea cluster). Members of a genetic asteroid family represent fragments derived from various depths within the original parent planetesimal. Thus, family members offer the potential for direct examination of the interiors of parent bodies which have undergone metamorphism and differentiation similar to that occurring in the inaccessible interiors of terrestrial planets. The differentiation similar to that occurring in the inaccessible interiors of terrestrial planets. The condition that genetic family members represent the fragments of a parent object provides a critical test of whether an association (cluster in proper element space) is a genetic family. Compositions (types and relative abundances of materials) of family members must permit the reconstruction of a compositionally plausible parent body. The compositions of proposed family members can be utilized to test the genetic reality of the family and to determine the type and degree of internal differentiation within the parent planetesimal. The interpretation of the S-class mineralogy provides a preliminary evaluation of family memberships. Detailed mineralogical and petrological analysis was done based on the reflectance spectra of 39 S-type asteroids. The result is a division of the S-asteroid class into seven subtypes based on compositional differences. These subtypes, designated S(I) to S(VII), correspond to surface silicate assemblages ranging from monomineralic olivine (dunites) through olivine-pyroxene mixtures to pure pyroxene or pyroxene-feldspar mixtures (basalts). The most general conclusion is that the S-asteroids cannot be treated as a single group of objects without greatly oversimplifying their properties. Each S-subtype needs to be treated as an independent group with a distinct evolutionary history.

Kelley, M. S.↗

NASA NTRS1993

Origin of the Apollo 15 very low Ti green glass. A perspective from the compositional diversity in the very low Ti glasses

The very low Ti green glasses from the Apollo 15 site have intrigued scientists for over 20 years. Their primitive composition has been used to understand magmatic processes and the structure of the moon. The compositional variability observed in the Apollo 15 glass population has long been a point of debate. Initial studies did not recognize the compositional diversity in the glasses. Stolper et al. documented the major element variability and concluded it could not be produced by magmatic processes and therefore concluded that these glasses must be of impact origin. Subsequent studies confirmed a volcanic origin for the glass population and attempted to elucidate magmatic processes to account for its compositional variability. Models that have been proposed for these glasses include the following: (1) the crystallization of single or multiple phases (olivine, pyroxene, Fe metal, immiscible sulfide); (2) the incompatible behavior of Ni and Co during multiple phase crystallization at extremely low fO2; and (3) magma or source mixing. All of these models have problems. Type (1) models appear not to be consistent with recent trace element studies on the glasses; model (2) is dependent on the debatable incompatible behavior of Ni and Co, and, in models of type (3), the origin and nature of mixing models are somewhat unconstrained. This study compares the Apollo 15 green glasses with the very low Ti picritic glasses from other landing sites.

Shearer, C. K.↗

NASA NTRS1993

The NCC project: A quality management perspective

The Network Control Center (NCC) Project introduced the concept of total quality management (TQM) in mid-1990. The CSC project team established a program which focused on continuous process improvement in software development methodology and consistent deliveries of high quality software products for the NCC. The vision of the TQM program was to produce error free software. Specific goals were established to allow continuing assessment of the progress toward meeting the overall quality objectives. The total quality environment, now a part of the NCC Project culture, has become the foundation for continuous process improvement and has resulted in the consistent delivery of quality software products over the last three years.

Lee, Raymond H.↗

NASA NTRS1993

Monitoring issues from a modeling perspective

Recognition that earth's climate and biogeophysical conditions are likely changing due to human activities has led to a heightened awareness of the need for improved long-term global monitoring. The present long-term measurement efforts tend to be spotty in space, inadequately calibrated in time, and internally inconsistent with respect to other instruments and measured quantities. In some cases, such as most of the biosphere, most chemicals, and much of the ocean, even a minimal monitoring program is not available. Recently, it has become painfully evident that emerging global change issues demand information and insights that the present global monitoring system simply cannot supply. This is because a monitoring system must provide much more than a statement of change at a given level of statistical confidence. It must describe changes in diverse parts of the entire earth system on regional to global scales. It must be able to provide enough input to allow an integrated physical characterization of the changes that have occurred. Finally, it must allow a separation of the observed changes into their natural and anthropogenic parts. The enormous policy significance of global change virtually guarantees an unprecedented level of scrutiny of the changes in the earth system and why they are happening. These pressures create a number of emerging challenges and opportunities. For example, they will require a growing partnership between the observational programs and the theory/modeling community. Without this partnership, the scientific community will likely fall short in the monitoring effort. The monitoring challenge before us is not to solve the problem now, but rather to set appropriate actions in motion so as to create the required framework for solution. Each individual piece needs to establish its role in the large problem and how the required interactions are to take place. Below, we emphasize some of the needs and opportunities that could and should be addressed through participation by the theoreticians and modelers in the global change monitoring effort.

Mahlman, Jerry D.↗

NASA NTRS1992

Scientific computing in the 1990ies: An astronomical perspective

The compute performance, storage capability, degree of networking, and usability of modern computer hardware have enormously progressed in the past decade. These hardware advances are not paralleled by an equivalent increase in software productivity. Among astronomers the need is gradually perceived to discuss questions such as whether we are prepared to meet the pending challenge of vector and massively parallel computers. Therefore, a moderated, time-limited and access-restricted, wide-area network discussion forum is proposed for having a first, broad-minded go at the question of whether our current software efforts are heading in the right direction. The main topics, goals, means, and form of the proposed discussion process are presented.

Adorf, Hans-Martin↗

NASA NTRS1993

Future directions in flight simulation: A user perspective

Langley Research Center was an early leader in simulation technology, including a special emphasis in space vehicle simulations such as the rendezvous and docking simulator for the Gemini program and the lunar landing simulator used before Apollo. In more recent times, Langley operated the first synergistic six degree of freedom motion platform (the Visual Motion Simulator, or VMS) and developed the first dual-dome air combat simulator, the Differential Maneuvering Simulator (DMS). Each Langley simulator was developed more or less independently from one another with different programming support. At present time, the various simulation cockpits, while supported by the same host computer system, run dissimilar software. The majority of recent investments in Langley's simulation facilities have been hardware procurements: host processors, visual systems, and most recently, an improved motion system. Investments in software improvements, however, have not been of the same order.

Jackson, Bruce↗

NASA NTRS1992

First Annual HSR Program Workshop: Headquarters perspective

The presentation is made up of viewgraphs. The national challenge is presented along with the program genesis and structure. The objectives of the workshop are also given. The national challenge is to develop and take advantage of the growing market for long distance air travel. The High Speed Civil Transport (HSCT) represents the next plateau in an aggressive international aviation competition. The workshop is to review and discuss future effort and plans in HSR.

Anderson, Robert E.↗

NASA NTRS1992

Community noise technology needs: Boeing's perspective

Airport community acceptance of High Speed Civil Transport (HSCT) noise levels will depend on the relative noise levels of airplanes flying at the time of introduction. The 85 dBA noise contours for the range of large subsonic airplanes that are expected to be in service in the early 21st century are shown as a shaded area. A certifiable HSCT noise contour as shown, would be somewhat wider along the runway, but about the same in the residential areas downrange. An HSCT noise rule should insure this noise capability.

Nihart, Gene L.↗

NASA NTRS1992

HSCT airframe materials: The Boeing perspective

Vugraphs are presented on the effect of cruise Mach number on the maximum takeoff weight of the High Speed Commercial Transport (HSCT). Predictions are made of the service life of the aircraft, and the aging effects of various candidate materials are examined. The objective of the study is to develop and evaluate low cost airplane designs by examining alternate structural, material, and manufacturing concepts, for the purpose of advising material suppliers and NASA on desired materials, product forms, and processing techniques.

Grande, Donald L.↗

NASA NTRS1992

HSCT materials and structures: An MDC perspective

The key High Speed Civil Transport (HSCT) features which control the materials selection are discussed. Materials are selected based on weight and production economics. The top-down and bottoms-up approaches to material selection are compared for the Mach 2.4 study baseline aircraft. The key materials and structures related tasks which remain to be accomplished prior to proceeding with the building of the HSCT aircraft are examined.

Sutton, Jay O.↗

NASA NTRS1994

NASA/DOD Aerospace Knowledge Diffusion Research Project. Paper 41: Technical communication practices of Dutch and US aerospace engineers and scientists: International perspective on aerospace

As part of Phase 4 of the NASA/DOD Aerospace Knowledge Diffusion Research Project, studies were conducted that investigated the technical communications practices of Dutch and U.S. aerospace engineers and scientists. The studies had the following objectives: (1) to solicit the opinions of aerospace engineers and scientists regarding the importance of technical communication to their professions, (2) to determine the use and production of technical communication by aerospace engineers and scientists, (3) to investigate their use of libraries and technical information centers, (4) to investigate their use of and the importance to them of computer and information technology, (5) to examine their use of electronic networks, and (6) to determine their use of foreign and domestically produced technical reports. Self-administered (mail) questionnaires were distributed to Dutch aerospace engineers and scientists at the National Aerospace Laboratory (NLR) in the Netherlands, the NASA Ames Research Center in the U.S., and the NASA Langley Research Center in the U.S. Responses of the Dutch and U.S. participants to selected questions are presented in this paper.

Barclay, Rebecca O.↗

NASA NTRS1992

Forced unsteady deceleration of a turbulent boundary layer from a temporal perspective

The behavior of a turbulent boundary layer which has been subjected to a local ramp-like deceleration in the external velocity field, which leads to forced separation, has been studied experimentally. The data of this study are re-interpreted in light of more recent findings concerning the temporal nature of boundary layer turbulence in the presence of forced unsteady shear. In particular, the robustness of the near-wall turbulent motions to organized deformation is recognized. Their resilence during unsteady shearing action promotes continued efficient turbulent mixing and rapid redistribution of turbulent kinetic energy during forced transients. In aerodynamic problems, the rapid nature of the adjustment of the turbulence field to a new temporal boundary condition necessitates equally rapid remedial measures to be taken if means of control/prevention of forced unsteady separation are to be deployed to maximum effect. This requirement suggests exploration of the use of simple, real-time statistical forecasting techniques, based upon time-series analysis of easily-measurable features of the flow, to help assure timely deployment of mechanisms of boundary-layer control. This paper focuses upon the nature of turbulence in boundary layers undergoing forced deceleration which would lead to separation. A preliminary form of a forecasting model is presented and evaluated. Using observations of the previous two large eddies passing a detector, it forecasts the behavior of the future large eddy rather well.

Brereton, G. J.↗

NASA NTRS1993

Perspectives on hypersonic viscous flow research

Issues and advances in current hypersonic flow research perceived to be of interest in theoretical fluid/gas dynamics are reviewed. Particular attention is given to the hypersonic aircraft as waverider, computational methods and theoretical development in the study of viscous interaction, and boundary-layer instability and transition studies. In the present framework the study of viscous hypersonic flow faces transition problems of two kinds which represent the two major areas of current research: the turbulence transition in the high Re range and the transition to the free-molecule limit.

Cheng, H. K.↗