1,810 research outputs found
Solid motor diagnostic instrumentation
A review of typical surveillance and monitoring practices followed during the flight phases of representative solid-propellant upper stages and apogee motors was conducted to evaluate the need for improved flight diagnostic instrumentation on future spacecraft. The capabilities of the flight instrumentation package were limited to the detection of whether or not the solid motor was the cause of failure and to the identification of probable primary failure modes. Conceptual designs of self-contained flight instrumentation packages capable of meeting these reqirements were generated and their performance, typical cost, and unit characteristics determined. Comparisons of a continuous real time and a thresholded hybrid design were made on the basis of performance, mass, power, cost, and expected life. The results of this analysis substantiated the feasibility of a self-contained independent flight instrumentation module as well as the existence of performance margins by which to exploit growth option applications
IUS/payload communication system simulator configuration definition study
The requirements and specifications for a general purpose payload communications system simulator to be used to emulate those communications system portions of NASA and DOD payloads/spacecraft that will in the future be carried into earth orbit by the shuttle are discussed. For the purpose of on-orbit checkout, the shuttle is required to communicate with the payloads while they are physically located within the shuttle bay (attached) and within a range of 20 miles from the shuttle after they have been deployed (detached). Many of the payloads are also under development (and many have yet to be defined), actual payload communication hardware will not be available within the time frame during which the avionic hardware tests will be conducted. Thus, a flexible payload communication system simulator is required
Development of whole-heart myocardial perfusion magnetic resonance imaging
Myocardial perfusion imaging is of huge importance for the detection of
coronary artery disease (CAD), one of the leading causes of morbidity
and mortality worldwide, as it can provide non-invasive detection at the
early stages of the disease. Magnetic resonance imaging (MRI) can assess
myocardial perfusion by capturing the rst-pass perfusion (FPP) of a
gadolinium-based contrast agent (GBCA), which is now a well-established
technique and compares well with other modalities. However, current MRI
methods are restricted by their limited coverage of the left ventricle. Interest
has therefore grown in 3D volumetric \whole-heart" FPP by MRI, although
many challenges currently limit this. For this thesis, myocardial perfusion
assessment in general, and 3D whole-heart FPP in particular, were reviewed
in depth, alongside MRI techniques important for achieving 3D FPP. From
this, a 3D `stack-of-stars' (SOS) FPP sequence was developed with the aim
of addressing some current limitations. These included the breath-hold
requirement during GBCA rst-pass, long 3D shot durations corrupted by
cardiac motion, and a propensity for artefacts in FPP. Parallel imaging and
compressed sensing were investigated for accelerating whole-heart FPP, with
modi cations presented to potentially improve robustness to free-breathing.
Novel sequences were developed that were capable of individually improving
some current sequence limits, including spatial resolution and signal-to-noise
ratio, although with some sacri ces. A nal 3D SOS FPP technique was
developed and tested at stress during free-breathing examinations of CAD
patients and healthy volunteers. This enabled the rst known detection of an
inducible perfusion defect with a free-breathing, compressed sensing, 3D FPP
sequence; however, further investigation into the diagnostic performance is
required. Simulations were performed to analyse potential artefacts in 3D
FPP, as well as to examine ways towards further optimisation of 3D SOS
FPP. The nal chapter discusses some limitations of the work and proposes
opportunities for further investigation.Open Acces
Conceptual definition of a high voltage power supply test facility
NASA Lewis Research Center is presently developing a 60 GHz traveling wave tube for satellite cross-link communications. The operating voltage for this new tube is - 20 kV. There is concern about the high voltage insulation system and NASA is planning a space station high voltage experiment that will demonstrate both the 60 GHz communications and high voltage electronics technology. The experiment interfaces, requirements, conceptual design, technology issues and safety issues are determined. A block diagram of the high voltage power supply test facility was generated. It includes the high voltage power supply, the 60 GHz traveling wave tube, the communications package, the antenna package, a high voltage diagnostics package and a command and data processor system. The interfaces with the space station and the attached payload accommodations equipment were determined. A brief description of the different subsystems and a discussion of the technology development needs are presented
Space Shuttle/TDRSS communication and tracking systems analysis
In order to evaluate the technical and operational problem areas and provide a recommendation, the enhancements to the Tracking and Data Delay Satellite System (TDRSS) and Shuttle must be evaluated through simulation and analysis. These enhancement techniques must first be characterized, then modeled mathematically, and finally updated into LinCsim (analytical simulation package). The LinCsim package can then be used as an evaluation tool. Three areas of potential enhancements were identified: shuttle payload accommodations, TDRSS SSA and KSA services, and shuttle tracking system and navigation sensors. Recommendations for each area were discussed
System analysis and integration studies for a 15-micron horizon radiance measurement experiment
Systems analysis and integration studies for 15-micron horizon radiance measurement experimen
A high-rate telemetry system for the Mariner Mars 1969 mission
High rate telemetry system for Mariner Mars 1969 missio
Analysis of spacecraft anomalies
The anomalies from 316 spacecraft covering the entire U.S. space program were analyzed to determine if there were any experimental or technological programs which could be implemented to remove the anomalies from future space activity. Thirty specific categories of anomalies were found to cover nearly 85 percent of all observed anomalies. Thirteen experiments were defined to deal with 17 of these categories; nine additional experiments were identified to deal with other classes of observed and anticipated anomalies. Preliminary analyses indicate that all 22 experimental programs are both technically feasible and economically viable
Preliminary candidate advanced avionics system for general aviation
An integrated avionics system design was carried out to the level which indicates subsystem function, and the methods of overall system integration. Sufficient detail was included to allow identification of possible system component technologies, and to perform reliability, modularity, maintainability, cost, and risk analysis upon the system design. Retrofit to older aircraft, availability of this system to the single engine two place aircraft, was considered
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