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At least 649 records · Page 36

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NASA NTRS1992

A Segmented Ion-Propulsion Engine

New design approach for high-power (100-kW class or greater) ion engines conceptually divides single engine into combination of smaller discharge chambers integrated to operate as single large engine. Analogous to multicylinder automobile engine, benefits include reduction in required accelerator system span-to-gap ratio for large-area engines, reduction in required hollow-cathode emission current, mitigation of plasma-uniformity problem, increased tolerance to accelerator system faults, and reduction in vacuum-system pumping speed.

Brophy, John R.↗

NASA NTRS1990

Planning and reasoning in the JPL telerobot testbed

The Telerobot Interactive Planning System is developed to serve as the highest autonomous-control level of the Telerobot Testbed. A recent prototype is described which integrates an operator interface for supervisory control, a task planner supporting disassembly and re-assembly operations, and a spatial planner for collision-free manipulator motion through the workspace. Each of these components is described in detail. Descriptions of the technical problem, approach, and lessons learned are included.

Peters, Stephen↗

NASA NTRS1992

Retrievable payload carrier. Next generation Long Duration Exposure Facility: Update 1992

Perry, A. T.↗

NASA NTRS1992

The Breadboard Project - A functioning CELSS plant growth system

The primary objective of the Breadboard Project for the next 3-4 years is to develop, integrate and operate a Controlled Ecological Life Support System (CELSS) at a one-person scale. The focus of this project over the past two years has been the development of the plant growth facility, the first module of the CELSS. The other major modules, food preparation, biomass processing, and resource recovery, have been researched at the laboratory scale during the past two years and facilities are currently under construction to scale-up these modules to an operational state. This paper will outline the design requirements for the Biomass Production Chamber (BPC), the plant growth facility for the project, and the control and monitoring subsystems which operate the chamber and will present results from both engineering and biological tests of the facility. Three production evaluations of wheat, conducted in the BPC during the past year, will be described and the data generated from these tests discussed.

Knott, W. M.↗

NASA NTRS1993

Tuners For Coplanar-Strip Transmission Lines

Sliding radio-frequency short circuits easily adjusted for optimum impedance. Tuning elements developed for use in planar integrated circuits operating at frequencies from about 10 to more than 1,000 GHz. Purpose of such adjustment to adjust impedance presented to circuit connected to nonshorted end of transmission line and thereby optimizes performance of circuit. Mixers, oscillators, amplifiers, couplers, and phase shifters among circuits improved by incorporating tuners of this type.

Mcgrath, William R.↗

NASA NTRS1993

LDEF archival system plan

The Long Duration Exposure Facility (LDEF) has provided the first significant opportunity to extensively study the space environment and its effects upon spacecraft systems and materials. The long-term value of the data obtained from LDEF, which is applicable to a wide range of areas including space environment definition, space environmental effects, and spacecraft design, will depend upon the system developed to archive and retrieve the data. Therefore, in addition to the large effort undertaken to analyze LDEF data, a substantial effort is also necessary in order to retain and disseminate LDEF resources for future research and design. W. J. Schafer Associates, Inc., has a task subcontract to develop the LDEF archival system. The LDEF resources include data, hardware, photographic records, and publications which cover the 20-year history of LDEF from concept design through data analysis. Chronologically, prelaunch resources include documentation of facility and experiment development, testing integration, and operation. Post-retrieval resources are the observations, testing, analysis, and publications since the January 1990 retrieval of LDEF. A third set of resources is the experiment and facility hardware and specimens, including more than 10,000 test specimens flown on LDEF and subsequently divided and distributed among investigators at numerous laboratories. Many valuable science and technology investigations were undertaken with LDEF experiments and hardware, and many more investigations are being identified in areas not yet explored. LDEF data applications encompass primarily low-Earth orbit spacecraft and structures. The nearly six-year space exposure of LDEF has provided data to evaluate materials, systems, and living specimens exposed to radiation, meteoroids, debris, and other constituents of the low-Earth environment. Structural, mechanical, electrical, optical, and thermal systems were studied, and materials with applications in all aspects of space systems were exposed to the space environment. The objectives of the LDEF archival system are to maintain the existing LDEF hardware, data, analysis, publications, and photographs as a long term resource, and to provide a quick and simple mechanism by which LDEF resources can be identified, located, and applied.

Wilson, Brenda K.↗

NASA NTRS1993

Retrievable payload carrier, next generation Long Duration Exposure Facility: Update 1992

Access to space and cost have been two major inhibitors of low Earth orbit research. The Retrievable Payload Carrier (RPC) Program is a commercial space program which strives to overcome these two barriers to space experimentation. The RPC Program's fleet of spacecraft, ground communications station, payload processing facility, and experienced integration and operations team will provide a convenient 'one-stop shop' for investigators seeking to use the unique vantage point and environment of low Earth orbit for research. The RPC is a regularly launched and retrieved, free-flying spacecraft providing resources adequate to meet modest payload/experiment requirements, and presenting ample surface area, volume, mass, and growth capacity for investigator usage. Enhanced capabilities of ground communications, solar-array-supplied electrical power, central computing, and on-board data storage pick up on the path where NASA's Long Duration Exposure Facility (LDEF) blazed the original technology trail. Mission lengths of 6-18 months, or longer, are envisioned. The year 1992 was designated as the 'International Space Year' and coincides with the 500th anniversary of Christopher Columbus's voyage to the New World. This is a fitting year in which to launch the full scale development of our unique shop of discovery whose intent is to facilitate retrieving technological rewards from another new world: space. Presented is an update on progress made on the RPC Program's development since the November 1991 LDEF Materials Workshop.

Perry, A. T.↗

NASA NTRS1991

Overview of NASA communications infrastructure

The infrastructure of NASA communications systems for effecting coordination across NASA offices and with the national and international research and technological communities is discussed. The offices and networks of the communication system include the Office of Space Science and Applications (OSSA), which manages all NASA missions, and the Office of Space Operations, which furnishes communication support through the NASCOM, the mission critical communications support network, and the Program Support Communications network. The NASA Science Internet was established by OSSA to centrally manage, develop, and operate an integrated computer network service dedicated to NASA's space science and application research. Planned for the future is the National Research and Education Network, which will provide communications infrastructure to enhance science resources at a national level.

Arnold, Ray J.↗

NASA NTRS1992

Space Congress, 29th, Cocoa Beach, FL, Apr. 21-24, 1992, Proceedings

The present volume on the quest for new frontiers in space discusses weather impacts on space operations, planning for the performance of future space bases, a new guidance and control unit for the Titan IV vehicle, and nondestructive evaluation of Shuttle Columbia tiles. Attention is given to Space Shuttle payload accommodations and trends in customer demands, a generic propellants transfer unit, making space part of general education, space station on-orbit solar array loads during assembly, and dimensional stability of the attitude reference assembly on SSF. Topics addressed include National Launch System payload accommodations and launch operations, the integrated factory/launch site processing concept, Pioneer 10 interstellar studies, and the role of advanced nuclear propulsion systems in precursor interstellar missions. Also discussed are legal challenges in realizing interstellar initiatives, Mars transportation system synthesis, and NASA's commercial space program.

Source record↗

NASA NTRS1992

The rapidly moving telescope - A progress report

A ground-based optical telescope system has been constructed with the capability to locate fast optical transients that may be associated with gamma-ray bursts (GRBs). The instrument has been integrated and operated during a shakedown period at GSFC, Maryland. Results of 35 hours of 'state mode' data are presented. The telescope has the proven capability to slew to any point on the night sky within 1.0 sec, track that position with better than one arcsecond stability, and image a 9 x 12 arcmin field of view with 1 arcsec angular resolution with 1.5 sec time resolution. The telescope-CCD camera system has a sensitivity of 13th magnitude for transients and 14th mag for field stars. In the 35 hr of operation many single frame transients of instrumental and optical origin have been observed; no two-sequential frame astrophysical transients have been identified. The combined rate of instrumental transients (predominantly sea-level muons) is 7.2/hr and of optical transients (satellite glints, airplane strobe lights, and meteors) is 5.1/hr. The RMT will operate in conjunction with the MIT Explosive Transient Camera survey instrument at Kitt Peak National Observatory, Tucson. The RMT is now being installed at Kitt Peak. Full operation will begin this summer.

Barthelmy, S. D.↗

NASA NTRS1952

Performance of the Components of the XJ34-WE-32 Turbojet Engine over a Range of Engine and Flight Conditions

Performance of the compressor, combustor, and turbine operating as integral parts of the XJ34-WE-32 turbojet engine was determined in the Lewis altitude wind tunnel over a range of altitudes from 5000 to 55,000 feet and flight Mach numbers from 0.28 to 1.05. Data were obtained for each of four exhaust-nozzle areas and are presented in graphical and tabular form.

ENGINES, TURBO-JET↗

NASA NTRS1994

Implementation of a low-cost, commercial orbit determination system

Traditional satellite and launch control systems have consisted of custom solutions requiring significant development and maintenance costs. These systems have typically been designed to support specific program requirements and are expensive to modify and augment after delivery. The expanding role of space in today's marketplace combined with the increased sophistication and capabilities of modern satellites has created a need for more efficient, lower cost solutions to complete command and control systems. Recent technical advances have resulted in commercial-off-the-shelf products which greatly reduce the complete life-cycle costs associated with satellite launch and control system procurements. System integrators and spacecraft operators have, however, been slow to integrate these commercial based solutions into a comprehensive command and control system. This is due, in part, to a resistance to change and the fact that many available products are unable to effectively communicate with other commercial products. The United States Air Force, responsible for the health and safety of over 84 satellites via its Air Force Satellite Control Network (AFSCN), has embarked on an initiative to prove that commercial products can be used effectively to form a comprehensive command and control system. The initial version of this system is being installed at the Air Force's Center for Research Support (CERES) located at the National Test Facility in Colorado Springs, Colorado. The first stage of this initiative involved the identification of commercial products capable of satisfying each functional element of a command and control system. A significant requirement in this product selection criteria was flexibility and ability to integrate with other available commercial products. This paper discusses the functions and capabilities of the product selected to provide orbit determination functions for this comprehensive command and control system.

Corrigan, Jim↗

NASA NTRS1994

Scheduling with genetic algorithms

In many domains, scheduling a sequence of jobs is an important function contributing to the overall efficiency of the operation. At Boeing, we develop schedules for many different domains, including assembly of military and commercial aircraft, weapons systems, and space vehicles. Boeing is under contract to develop scheduling systems for the Space Station Payload Planning System (PPS) and Payload Operations and Integration Center (POIC). These applications require that we respect certain sequencing restrictions among the jobs to be scheduled while at the same time assigning resources to the jobs. We call this general problem scheduling and resource allocation. Genetic algorithms (GA's) offer a search method that uses a population of solutions and benefits from intrinsic parallelism to search the problem space rapidly, producing near-optimal solutions. Good intermediate solutions are probabalistically recombined to produce better offspring (based upon some application specific measure of solution fitness, e.g., minimum flowtime, or schedule completeness). Also, at any point in the search, any intermediate solution can be accepted as a final solution; allowing the search to proceed longer usually produces a better solution while terminating the search at virtually any time may yield an acceptable solution. Many processes are constrained by restrictions of sequence among the individual jobs. For a specific job, other jobs must be completed beforehand. While there are obviously many other constraints on processes, it is these on which we focussed for this research: how to allocate crews to jobs while satisfying job precedence requirements and personnel, and tooling and fixture (or, more generally, resource) requirements.

Fennel, Theron R.↗

NASA NTRS1995

Nuclear Thermal Rocket/Vehicle Design Options for Future NASA Missions to the Moon and Mars

The nuclear thermal rocket (NTR) provides a unique propulsion capability to planners/designers of future human exploration missions to the Moon and Mars. In addition to its high specific impulse (approximately 850-1000 s) and engine thrust-to-weight ratio (approximately 3-10), the NTR can also be configured as a 'dual mode' system capable of generating electrical power for spacecraft environmental systems, communications, and enhanced stage operations (e.g., refrigeration for long-term liquid hydrogen storage). At present the Nuclear Propulsion Office (NPO) is examining a variety of mission applications for the NTR ranging from an expendable, single-burn, trans-lunar injection (TLI) stage for NASA's First Lunar Outpost (FLO) mission to all propulsive, multiburn, NTR-powered spacecraft supporting a 'split cargo-piloted sprint' Mars mission architecture. Each application results in a particular set of requirements in areas such as the number of engines and their respective thrust levels, restart capability, fuel operating temperature and lifetime, cryofluid storage, and stage size. Two solid core NTR concepts are examined -- one based on NERVA (Nuclear Engine for Rocket Vehicle Application) derivative reactor (NDR) technology, and a second concept which utilizes a ternary carbide 'twisted ribbon' fuel form developed by the Commonwealth of Independent States (CIS). The NDR and CIS concepts have an established technology database involving significant nuclear testing at or near representative operating conditions. Integrated systems and mission studies indicate that clusters of two to four 15 to 25 klbf NDR or CIS engines are sufficient for most of the lunar and Mars mission scenarios currently under consideration. This paper provides descriptions and performance characteristics for the NDR and CIS concepts, summarizes NASA's First Lunar Outpost and Mars mission scenarios, and describes characteristics for representative cargo and piloted vehicles compatible with a reference 240 t-class heavy lift launch vehicle (HLLV) and smaller 120 t HLLV option. Attractive performance characteristics and high-leverage technologies associated with both the engine and stage are identified, and supporting parametric sensitivity data is provided. The potential for commonality of engine and stage components to satisfy a broad range of lunar and Mars missions is also discussed.

Borowski, Stanley K.↗

NASA NTRS1995

Ka-band MMIC array system for ACTS aeronautical terminal experiment (Aero-X)

During the summer of 1994, the Advanced Communication Technology Satellite (ACTS) Aeronautical Terminal Experiment (Aero-X) was successfully completed by the NASA Lewis Research Center (LeRC) and the Jet Propulsion Laboratory (JPL). 4.8 and 9.6 Kbps duplex voice links were established between the LeRC Learjet and the ACTS Link Evaluation Terminal (LET) in Cleveland, Ohio, via the ACTS. The antenna system used in this demonstration was developed by LeRC and featured LeRC and US Air Force experimental arrays using GaAs MMIC devices at each radiating element for electronic beam steering and distributed power amplification. The antenna system consisted of three arrays mounted inside the LeRC Learjet, pointing out through the windows. An open loop tracking controller developed by LeRC used information from the aircraft position and attitude sensors to automatically steer the arrays toward ACTS during flight JPL ACTS Mobile Terminal (AMT) system hardware was used as transceivers both on the aircraft and at the LET. The single 32 element MMIC transmit array developed by NASA/LeRC and Texas Instruments has an EIRP of 23.4 dBW at boresight. The two 20 GHz MMIC receive arrays were developed in a cooperative effort with the USAF Rome Laboratory/Electronic System Center, taking advantage of existing USAF array development contracts with Boeing and Martin Marietta. The Boeing array has 23 elements and a G/T of 16/6 db/degK at boresight. The Martin Marietta array has 16 elements and a G/T of 16.1 db/degK at boresight. The three proof-of-concept arrays, the array control system and their integration and operation in the Learjet for Aero-X are described.

Raquet, Charles A.↗

NASA NTRS1998

Experimental Investigation of an Integrated Strut-Rocket/Scramjet Operating at Mach 4.0 and 6.5 Conditions

A series of tests were conducted to investigate RBCC performance at ramjet and scramjet conditions. The hardware consisted of a linear strut-rocket manufactured by Aerojet and a dual-mods scramjet combustor. The hardware was tested at NASA Langley Research Center in the Direct Connect Supersonic Combustion Test Facility at Mach 4.0 and 6.5 simulated flight conditions.

Hawk, Clark↗

NASA NTRS1999

Life Sciences Division Spaceflight Hardware

The Ames Research Center (ARC) is responsible for the development, integration, and operation of non-human life sciences payloads in support of NASA's Gravitational Biology and Ecology (GB&E) program. To help stimulate discussion and interest in the development and application of novel technologies for incorporation within non-human life sciences experiment systems, three hardware system models will be displayed with associated graphics/text explanations. First, an Animal Enclosure Model (AEM) will be shown to communicate the nature and types of constraints physiological researchers must deal with during manned space flight experiments using rodent specimens. Second, a model of the Modular Cultivation System (MCS) under development by ESA will be presented to highlight technologies that may benefit cell-based research, including advanced imaging technologies. Finally, subsystems of the Cell Culture Unit (CCU) in development by ARC will also be shown. A discussion will be provided on candidate technology requirements in the areas of specimen environmental control, biotelemetry, telescience and telerobotics, and in situ analytical techniques and imaging. In addition, an overview of the Center for Gravitational Biology Research facilities will be provided.

Yost, B.↗

NASA NTRS2000

Demonstration of a Large-Scale Tank Assembly via Circumferential Friction Stir Welds

A collaborative effort between NASA/Marshall Space Flight Center and the Michoud Unit of Lockheed Martin Space Systems Company was undertaken to demonstrate assembly of a large-scale aluminum tank using circumferential friction stir welds. The hardware used to complete this demonstration was fabricated as a study of near-net- shape technologies. The tooling used to complete this demonstration was originally designed for assembly of a tank using fusion weld processes. This presentation describes the modifications and additions that were made to the existing fusion welding tools required to accommodate circumferential friction stir welding, as well as the process used to assemble the tank. The tooling modifications include design, fabrication and installation of several components. The most significant components include a friction stir weld unit with adjustable pin length capabilities, a continuous internal anvil for 'open' circumferential welds, a continuous closeout anvil, clamping systems, an external reaction system and the control system required to conduct the friction stir welds and integrate the operation of the tool. The demonstration was intended as a development task. The experience gained during each circumferential weld was applied to improve subsequent welds. Both constant and tapered thickness 14-foot diameter circumferential welds were successfully demonstrated.

Jones, Clyde S.↗