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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 613 records · Page 34
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Cometary delivery of organic molecules to the early earth

It has long been speculated that earth accreted prebiotic organic molecules important for the origins of life from impacts of carbonaceous asteroids and comets during the period of heavy bombardment 4.5 x 10 to the 9th to 3.8 x 10 to the 9th years ago. A comprehensive treatment of comet-asteroid interaction with the atmosphere, surface impact, and resulting organic pyrolysis demonstrates that organics will not survive impacts at velocities greater than about 10 kilometers per second and that even comets and asteroids as small as 100 meters in radius cannot be aerobraked to below this velocity in 1-bar atmospheres. However, for plausible dense (10-bar carbon dioxide) early atmospheres, it is found that 4.5 x 10 to the 9th years ago earth was accreting intact cometary organics at a rate of at least about 10 to the 6th to 10 to the 7th kilograms per year, a flux that thereafter declined with a half-life of about 10 to the 8th years. These results may be put in context by comparison with terrestrial oceanic and total biomasses, about 3 x 10 to the 12th kilograms and about 6 x 10 to the 14th kilograms, respectively.

Chyba, Christopher F.↗
NASA NTRS1990

21st century early mission concepts for Mars delivery and earth return

In the 21st century, the early missions to Mars will entail unmanned Rover and Sample Return reconnaissance missions to be followed by manned exploration missions. High performance leverage technologies will be required to reach Mars and return to earth. This paper describes the mission concepts currently identified for these early Mars missions. These concepts include requirements and capabilities for Mars and earth aerocapture, Mars surface operations and ascent, and Mars and earth rendezvous. Although the focus is on the unmanned missions, synergism with the manned missions is also discussed.

Cruz, Manuel I.↗
NASA NTRS1990

Expert system verification and validation study. Delivery 1: Survey and interview questions

The NASA funded questionnaire is presented to help define the state-of-the-practice in the formal evaluation of Expert Systems on current NASA and industry applications. The answers to this questionnaire, together with follow-up interviews, will provide realistic answers to the following questions: (1) How much evaluation is being performed; (2) What evaluation techniques are in use; and (3) What, if any, are the unique issues in evaluating Expert Systems.

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NASA NTRS1990

Expert system verification and validation survey. Delivery 2: Survey results

The purpose is to determine the state-of-the-practice in Verification and Validation (V and V) of Expert Systems (ESs) on current NASA and industry applications. This is the first task of the series which has the ultimate purpose of ensuring that adequate ES V and V tools and techniques are available for Space Station Knowledge Based Systems development. The strategy for determining the state-of-the-practice is to check how well each of the known ES V and V issues are being addressed and to what extent they have impacted the development of ESs.

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NASA NTRS1990

Expert system verification and validation study. Phase 2: Requirements identification. Delivery 1: Updated survey report

The purpose is to report the state-of-the-practice in Verification and Validation (V and V) of Expert Systems (ESs) on current NASA and Industry applications. This is the first task of a series which has the ultimate purpose of ensuring that adequate ES V and V tools and techniques are available for Space Station Knowledge Based Systems development. The strategy for determining the state-of-the-practice is to check how well each of the known ES V and V issues are being addressed and to what extent they have impacted the development of Expert Systems.

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NASA NTRS1991

Expert system verification and validation study. Phase 2: Requirements Identification. Delivery 2: Current requirements applicability

The second phase of a task is described which has the ultimate purpose of ensuring that adequate Expert Systems (ESs) Verification and Validation (V and V) tools and techniques are available for Space Station Freedom Program Knowledge Based Systems development. The purpose of this phase is to recommend modifications to current software V and V requirements which will extend the applicability of the requirements to NASA ESs.

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NASA NTRS1990

Expert system verification and validation survey. Delivery 3: Recommendations

The purpose is to determine the state-of-the-practice in Verification and Validation (V and V) of Expert Systems (ESs) on current NASA and Industry applications. This is the first task of a series which has the ultimate purpose of ensuring that adequate ES V and V tools and techniques are available for Space Station Knowledge Based Systems development. The strategy for determining the state-of-the-practice is to check how well each of the known ES V and V issues are being addressed and to what extent they have impacted the development of ESs.

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NASA NTRS1990

Expert system verification and validation survey, delivery 4

The purpose is to determine the state-of-the-practice in Verification and Validation (V and V) of Expert Systems (ESs) on current NASA and Industry applications. This is the first task of a series which has the ultimate purpose of ensuring that adequate ES V and V tools and techniques are available for Space Station Knowledge Based Systems development. The strategy for determining the state-of-the-practice is to check how well each of the known ES V and V issues are being addressed and to what extent they have impacted the development of ESs.

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NASA NTRS1990

Expert system verification and validation survey. Delivery 5: Revised

The purpose is to determine the state-of-the-practice in Verification and Validation (V and V) of Expert Systems (ESs) on current NASA and Industry applications. This is the first task of a series which has the ultimate purpose of ensuring that adequate ES V and V tools and techniques are available for Space Station Knowledge Based Systems development. The strategy for determining the state-of-the-practice is to check how well each of the known ES V and V issues are being addressed and to what extent they have impacted the development of ESs.

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NASA NTRS1991

CLIPS: A tool for the development and delivery of expert systems

The C Language Integrated Production System (CLIPS) is a forward chaining rule-based language developed by the Software Technology Branch at the Johnson Space Center. CLIPS provides a complete environment for the construction of rule-based expert systems. CLIPS was designed specifically to provide high probability, low cost, and easy integration with external systems. Other key features of CLIPS include a powerful rule syntax, an interactive development environment, high performance, extensibility, a verification/validation tool, extensive documentation, and source code availability. The current release of CLIPS, version 4.3, is being used by over 2,500 users throughout the public and private community including: all NASA sites and branches of the military, numerous Federal bureaus, government contractors, 140 universities, and many companies.

Riley, Gary↗
NASA NTRS1990

Delivery and application of precise timing for a traveling wave powerline fault locator system

The Bonneville Power Administration (BPA) has successfully operated an in-house developed powerline fault locator system since 1986. The BPA fault locator system consists of remotes installed at cardinal power transmission line system nodes and a central master which polls the remotes for traveling wave time-of-arrival data. A power line fault produces a fast rise-time traveling wave which emanates from the fault point and propagates throughout the power grid. The remotes time-tag the traveling wave leading edge as it passes through the power system cardinal substation nodes. A synchronizing pulse transmitted via the BPA analog microwave system on a wideband channel sychronizes the time-tagging counters in the remote units to a different accuracy of better than one microsecond. The remote units correct the raw time tags for synchronizing pulse propagation delay and return these corrected values to the fault locator master. The master then calculates the power system disturbance source using the collected time tags. The system design objective is a fault location accuracy of 300 meters. BPA's fault locator system operation, error producing phenomena, and method of distributing precise timing are described.

Street, Michael A.↗
NASA NTRS1991

Expert system verification and validation study. Delivery 3A and 3B: Trip summaries

Key results are documented from attending the 4th workshop on verification, validation, and testing. The most interesting part of the workshop was when representatives from the U.S., Japan, and Europe presented surveys of VV&T within their respective regions. Another interesting part focused on current efforts to define industry standards for artificial intelligence and how that might affect approaches to VV&T of expert systems. The next part of the workshop focused on VV&T methods of applying mathematical techniques to verification of rule bases and techniques for capturing information relating to the process of developing software. The final part focused on software tools. A summary is also presented of the EPRI conference on 'Methodologies, Tools, and Standards for Cost Effective Reliable Software Verification and Validation. The conference was divided into discussion sessions on the following issues: development process, automated tools, software reliability, methods, standards, and cost/benefit considerations.

French, Scott↗
NASA NTRS1992

A study of the control problem of the shoot side environment delivery system of a closed crop growth research chamber

The details of our initial study of the control problem of the crop shoot environment of a hypothetical closed crop growth research chamber (CGRC) are presented in this report. The configuration of the CGRC is hypothetical because neither a physical subject nor a design existed at the time the study began, a circumstance which is typical of large scale systems control studies. The basis of the control study is a mathematical model which was judged to adequately mimic the relevant dynamics of the system components considered necessary to provide acceptable realism in the representation. Control of pressure, temperature, and flow rate of the crop shoot environment, along with its oxygen, carbon dioxide, and water concentration is addressed. To account for mass exchange, the group of plants is represented in the model by a source of oxygen, a source of water vapor, and a sink for carbon dioxide. In terms of the thermal energy exchange, the group of plants is represented by a surface with an appropriate temperature. Most of the primitive equations about an experimental operating condition and a state variable representation which was extracted from the linearized equations are presented. Next, we present the results of a real Jordan decomposition and the repositioning of an undesirable eigenvalue via full state feedback. The state variable representation of the modeling system is of the nineteenth order and reflects the eleven control variables and eight system disturbances. Five real eigenvalues are very near zero, with one at zero, three having small magnitude positive values, and one having a small magnitude negative value. A Singular Value Decomposition analysis indicates that these non-zero eigenvalues are not results of numerical error.

Blackwell, C. C.↗
NASA NTRS1992

Endogenous production, exogenous delivery and impact-shock synthesis of organic molecules - An inventory for the origins of life

The contribution of organic-rich comets, carbonaceous asteroids, and interplanetary dust particles and of impact shock-synthesized organics in the atmosphere to the origin of life on earth is studied and quantitatively compared with the principal non-heavy-bombardment sources of prebiotic organics. The results suggest that heavy bombardment before 3.5 Gyr ago either produced or delivered quantities of organics comparable to those produced by other energy sources.

Chyba, Christopher↗
NASA NTRS1991

Regenerable biocide delivery unit

The Microbial Check Valve (MCV) is used on the Space Shuttle to impart an iodine residual to the drinking water to maintain microbial control. Approximately twenty MCV locations have been identified in the Space Station Freedom design, each with a 90-day life. This translates to 2400 replacement units in 30 years of operation. An in situ regeneration concept has been demonstrated that will reduce this replacement requirement to less than 300 units based on data to date. A totally automated system will result in significant savings in crew time, resupply requirements, and replacement costs. An additional feature of the device is the ability to provide a concentrated biocide source (200 mg/liter of I2) that can be used to superiodinate systems routinely or after a microbial upset.

Colombo, Gerald V.↗
NASA NTRS1992

The breakup of a meteorite parent body and the delivery of meteorites to earth

Whether many of the 10,000 meteorites collected in the Antarctic are unlike those falling elsewhere is contentious. The Antarctic H chondrites, one of the major classes of stony meteorites, include a number of individuals with higher induced thermoluminescence peak temperatures than observed among non-Antarctic H chondrites. The proportion of such individuals decreases with the mean terrestrial age of the meteorites at the various ice fields. These H chondrites have cosmic-ray exposure ages of about 8 million years, experienced little cosmic-ray shielding, and suffered rapid postmetamorphic cooling. Breakup of the H chondrite parent body, 8 million years ago, may have produced two types of material with different size distributions and thermal histories. The smaller objects reached earth more rapidly through more rapid orbital evolution.

Benoit, Paul H.↗
NASA NTRS1993

Regenerable biocide delivery unit

A method and apparatus are disclosed for maintaining continuous, long-term microbial control in the water supply for potable, hygiene, and experimental water for space activities, as well as treatment of water supplies on Earth. The water purification is accomplished by introduction of molecular iodine into the water supply to impart a desired iodine residual. The water is passed through an iodinated anion exchange resin bed. The iodine is bound as I-(sub n) at the anion exchange sites and releases I(sub 2) into the water stream flowing through the bed. The concentration of I(sub 2) in the flowing water gradually decreases and, in the prior art, the ion-exchange bed has had to be replaced. In a preferred embodiment, a bed of iodine crystals is provided with connections for flowing water therethrough to produce a concentrated (substantially saturated) aqueous iodine solution which is passed through the iodinated resin bed to recharge the bed with bound iodine. The bed of iodine crystals is connected in parallel with the iodinated resin bed and is activated periodically (e.g., by timer, by measured flow of water, or by iodine residual level) to recharge the bed. Novelty resides in the capability of inexpensively and repeatedly regenerating the ion-exchange bed in situ.

Sauer, Richard L.↗
NASA NTRS1993

A dual output pressure, high reliability, long storage life gas delivery vessel assembly

A Gas Vessel Assembly has been developed that delivers purified, very low moisture content gas at two different output pressures. High pressure gas is delivered at up to 6,700 psi, and low pressure gas regulated to 130 psi is also delivered via a second outlet over a wide range of flow rates. The device is extremely lightweight (less than 1 lb) and compact, affords maximum mechanical integrity, high reliability (0.9999 at 95 percent confidence level), and offers extremely long storage life. Specialized design and fabrication techniques are employed that guarantee gas purity and negligible leakage for more than 20 years, in widely varying conditions of storage temperature, humidity, altitude, and vibration environments. The technology offers unique advantages in fast, high pressure discharge applications. For example, when combined with a cryostat, cryogenic temperatures can be achieved such as those used in missile seeker technology. The technology has many additional applications such as: emergency power sources for safety devices such as those needed in nuclear power plants, refineries, collision cushioning devices, superconductor cooling devices, emergency egress systems, miniature mechanical devices that employ gas bearings, and other areas where long storage, extremely high reliability and/or high energy density sources are required.

Maya, Isaac↗