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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 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

Super miniaturization of film capacitor dielectrics

The alignment of the stable electrical characteristics of film capacitors in the physical dimensions of ceramic and tantalum capacitors are discussed. The reliability of polycarbonate and mylar capacitors are described with respect to their compatibility with military specifications. Graphic illustrations are presented which show electrical and physical comparisons of film, ceramic, and tantalum capacitors. The major focus is on volumetric efficiency, weight reduction, and electrical stability.

Lavene, B.↗
NASA NTRS1981

Aircraft energy efficiency. Overview

Six advanced technology development projects that could cut fuel consumption of future civil air transports by as much as 50 percent are highlighted. These include improved engine components; better engine design; thin short blades for turboprop aircaft; using composite primary structures for weight reduction; the use of supercritical wings, higher aspect ratio, and winglets for improved aerodynamics; active controls; and laminar flow control. The time span of each of the six efforts and NASA's expected expenditures are also discussed.

Source record↗
NASA NTRS1980

Design, fabrication and test of a complex helicopter airframe section

A design solution is developed for the fabrication of an all-composite helicopter airframe cabin roof structure. Although this is inherently a complex structure, the parts count has been minimized by the avoidance of many mechanical fasteners, and a weight reduction of 26% has been obtained. The reduction of parts and elimination of mechanical fasteners will also result in a lowering of labor costs. The bonded graphite/epoxy elements of the structure employed aluminum tooling with control on all mating surfaces to yield accurate bond lines. A summary of static test results is presented for the basic structure and for the structure with mechanically fastened skin stiffeners. It is shown that the shear buckles caused the skin to peel from the stiffeners at about 960 lb/in. shear flow, calling for the addition of stiffeners with more bond area.

Rich, M. J.↗
NASA NTRS1981

Thermal design of the Space Shuttle External Tank

The history of the engineering and manufacturing requirements leading to the final Thermal Protection System (TPS) for the External Tank (ET) is presented. The thermal design for the ET must be optimized, based on considerations of cost, weight, and application of the TPS. The significant thermal requirements include the structural and component temperature limits, the propellant quality, the minimization of ice and frost, no air liquefaction, and no film boiling. The TPS materials selected to meet the requirements are a low density closed cell foam (CPR-488) and two light-weight ablators (SLA-56 and MA-25s). The first four flights of the Space Shuttle (1981) will measure and evaluate external environmental, structural, propulsion, electrical, and engine performance data. The ET will be instrumented to measure acoustics, pressures, heat transfer, vibration, temperatures, and structural strains. TPS weight reductions are planned for future ETs through the use of a comprehensive thermal instrumentation system.

Warmbrod, J. D.↗
NASA NTRS1981

Development status of a regenerative fuel cell system for orbital operation

Mission studies conducted by NASA for future long-term orbital operations have indicated the need for substantial increases in the power level of low-earth orbital energy storage facilities by the mid-to-late 1980's. A description is presented of the results of a comprehensive study for a state-of-the-art assessment of solid polymer electrolyte electrochemical cell technology. Questions related to the weight optimization of the dedicated system are investigated, and attention is given to the analysis of a system having reversible modules capable of operating in either the electrolysis or fuel cell mode. It was found that performance improvements and weight reduction can be realized by advancing the state of the art of solid polymer electrolyte cell technology.

Erickson, A. C.↗
NASA NTRS1981

Sea based support aircraft alternatives

Multi-mission, CTOL, STOL and V/STOL aircraft concepts were sized for the Navy ASW/ASUW missions and comparatively evaluated. Initially, technology levels in the areas of lift, control systems, propulsion, advanced materials and avionics were established for the early 1990's. The aircraft were compared to determine the impact of multi-mission requirements, operational considerations, chiefly takeoff mode, as well as the technology advancements. Results presented include performance envelopes, weight statements, growth factors, impact of technology on weight reduction and the impact of design constraints.

Priestley, R. T.↗
NASA NTRS1982

Thermal management for large space platforms

This paper provides an evaluation of heat rejection techniques applicable to multihundred-kilowatt space platforms. A number of promising heat rejection concepts were parametrically weight-optimized over a wide range of conditions to provide a 99% reliability of achieving a 10-yr life for the multihundred-kilowatt space platform. Three panel designs were considered: (1) an advanced meteoroid-bumpered hybrid heat pipe concept, (2) a bumpered liquid concept, and (3) a space constructable heat pipe radiator. The following are some of the significant findings from the study: (1) A single subsystem approach can be used with the heat pipe system, whereas several smaller subsystems are required for the pumped fluid systems. (2) The space constructable radiator approach offers a 10% weight reduction and operational advantages over the conventionally deployed panels.

Oren, J. A.↗
NASA NTRS1982

Preliminary submillimeter spectroscopic measurements using a submillimeter heterodyne radiometer

A submillimeter heterodyne radiometer uses a submillimeter laser, pumped by a CO2 laser, as a local oscillator and a room temperature Schottky barrier diode as the first IF mixer. The radiometer can resolve spectral lines in the submillimeter region of the spectrum (arising from pure rotational molecular transitions) to within 0.3 MHz, using acousto-optic spectrum analyzer which measures the power spectrum by simultaneously sampling 0.3 MHz wide channels over a 100 MHz bandwidth spanning the line. Preliminary observations of eight spectral lines of H2O2, CO, NH3 and H2O, all lying in the 434-524 micrometer wavelength range are described. All eight lines were observed using two local oscillator frequencies obtained by operating the submillimeter laser with either methyl fluoride (CH3F) or formic acid (HCOOH) as the lasing gas. Sample calculations of line parameters from the observed data show good agreement with established values. One development goal is the size and weight reduction of the package to make it suitable for balloon or shuttle experiments to detect trace gases in the upper atmosphere.

Safren, H. G.↗
NASA NTRS1982

Application of MMIC modules in future multiple beam satellite antenna systems

Multiple beam antenna systems for advanced communication satellites operating in the 30/20 GHz frequency bands (30 GHz uplink, 20 GHz downlink) were developed. Up to twenty 0.3 deg HPBW fixed spot beams and six 0.3 deg HPBW scanning spot beams will be required. Array-fed dual reflector antenna systems in which monolithic microwave integrated circuit (MMIC) phase shift and amplifier modules are used with each radiating element of the feed array for beam pointing and power gain were developed. The feasibility of distributed power amplification and beam pointing with MMIC modules in the elements of an array and to develop a data base for future development were demonstrated. The technical discussion centers around the potential advantages of ""monolithic'' antennas for specific applications as compared to systems using high powered TWT's. These include: reduced losses in the beam forming network; advantage of space combining and graceful degradation; dynamic control of beam pointing and illumination contour; and possibilities for cost and weight reduction.

Smetana, J.↗
NASA NTRS1979

Advanced composite elevator for Boeing 727 aircraft

Detail design activities are reported for a program to develop an advanced composites elevator for the Boeing 727 commercial transport. Design activities include discussion of the full scale ground test and flight test activities, the ancillary test programs, sustaining efforts, weight status, and the production status. Prior to flight testing of the advanced composites elevator, ground, flight flutter, and stability and control test plans were reviewed and approved by the FAA. Both the ground test and the flight test were conducted according to the approved plan, and were witnessed by the FAA. Three and one half shipsets have now been fabricated without any significant difficulty being encountered. Two elevator system shipsets were weighed, and results validated the 26% predicted weight reduction. The program is on schedule.

Source record↗
NASA NTRS1982

Advanced axial field D.C. motor development for electric passenger vehicle

A wound-field axial-flux dc motor was developed for an electric vehicle drive system. The motor is essentially an axial-flux version of the classical Gramme-ring winding motor, but the active conductors are recessed into slots cut into the two opposite faces of the laminated tape-wound core ring. Three motors were built and tested in the program. The second (functional) model was a six-pole machine which weighed 88.5 kg. It developed 16.9 km (33.0 hp), and a max speed of 4800 rpm. Full load efficiency was 92% and predicted SAE D-cycle efficiency was 88%. The last engineering) model was a 4-pole machine with compoles, allowing a weight reduction to 45 kg (100 lbs.) while addressing some manufacturability problems. The engineering model was rated at 13.2 kw (17.6 hp) at 3000 rpm, with a peak power of 19.8 km (26.4 hp) and a max speed of 7200 rpm. Initial test results on this motor showed poor commutation and efficiency; the program was terminated without resolution of these problems.

Jones, W. J.↗
NASA NTRS1979

Advanced composite vertical stabilizer for DC-10 transport aircraft

Structural design, tooling, fabrication, and test activities are reported for a program to develop an advanced composite vertical stabilizer (CVS) for the DC 10 Commercial Transport Aircraft. Structural design details are described and the status of structural and weight analyses are reported. A structural weight reduction of 21.7% is currently predicted. Test results are discussed for sine wave stiffened shear webs containing representative of the CVS spar webs and for lightning current transfer and tests on a panel representative of the CVS skins.

Stephens, C. O.↗
NASA NTRS1983

Assessment of flywheel energy storage for spacecraft power systems

The feasibility of inertial energy storage in a spacecraft power system is evaluated on the basis of a conceptual integrated design that encompasses a composite rotor, magnetic suspension, and a permanent magnet (PM) motor/generator for a 3-kW orbital average payload at a bus distribution voltage of 250 volts dc. The conceptual design, which evolved at the Goddard Space Flight Center (GSFC), is referred to as a Mechanical Capacitor. The baseline power system configuration selected is a series system employing peak-power-tracking for a Low Earth-Orbiting application. Power processing, required in the motor/generator, provides a potential alternative configurations that can only be achieved in systems with electrochemical energy storage by the addition of power processing components. One such alternative configuration provides for peak-power-tracking of the solar array and still maintains a regulated bus, without the expense of additional power processing components. Precise speed control of the two counterrotating wheels is required to reduce interaction with the attitude control system (ACS) or alternatively, used to perform attitude control functions. Critical technologies identified are those pertaining to the energy storage element and are prioritized as composite wheel development, magnetic suspension, motor/generator, containment, and momentum control. Comparison with a 3-kW, 250-Vdc power system using either NiCd or NiH2 for energy storage results in a system in which inertial energy storage offers potential advantages in lifetime, operating temperature, voltage regulation, energy density, charge control, and overall system weight reduction.

Rodriguez, G. E.↗
NASA NTRS1982

Graphite/polyimide technology overview and Space Shuttle Orbiter applications

The materials, production processes, testing procedures, and repair techniques for composite structures on the Orbiter are reviewed. The Orbiter currently features graphite/epoxy payload bay doors, as well as graphite/polyimide elevons, vertical tail, and aft body flap, which can withstand up to 600 F temperatures. Graphite/polyimide is also being considered for areas of the baseline aluminum structure and the thermal protection system in order to achieve a 20-30% weight reduction, i.e., over 7.5 tons. An analysis of the allowable stresses on FRC imide thermal protection system tiles bonded directly to the structure has shown satisfactory performances in high temperature and cryogenic conditions, although failure modes are yet to be determined. Ultrasonic emissions have been used for defect detection in nondestructive evaluations, together with tension, notch, shear, and compression tests. Field repairs have not been perfected, and require the evolution of high temperature adhesives that are curable under vacuum pressure and heat blankets.

Morita, W. H.↗
NASA NTRS1982

Optimum shapes for lightweighted mirrors

Two types of monolithic lightweight mirrors with arched backs, the center-supported single arch and the ring-supported double arch, are discussed. It is shown that, assuming a maximum permissible rms tolerance of 6 x 10 to the -6th in, the single arch mirror weighs about 50 percent of an equivalent solid mirror up to a diameter of 24 in. The single arch is relatively simple to construct and uses a simple center support. Where a better figure is required, or for larger sizes, the double arch is superior in performance to the single arch. The weight of the double arch will vary from about 50 to under 40 percent of an equivalent conventional mirror as the diameter is increased from 20 to 144 in. Further weight reduction for the double arch is possible through the reduction of the size of the support.

Vukobratovich, D.↗
NASA NTRS1983

System technology analysis of aeroassisted orbital transfer vehicles - Moderate lift/drag

The utilization of procedures involving aerodynamic braking and/or aerodynamic maneuvering on return from higher altitude orbits to low-earth orbit makes it possible to realize significant performance benefits. The present study is concerned with a number of mission scenarios for Aeroassisted Orbital Transfer Vehicles (AOTV) and the impact of potential technology advances in the performance enhancement of the class of AOTV's having a hypersonic lift to drag ratio (L/D) of 0.75 to 1.5. It is found that the synergistic combination of a hypersonic L/D of 1.2, an advanced cryopropelled engine, and an LH2 drop tank (1-1/2 stage) leads to a single 65,000 pound shuttle, two-man geosynchronous mission with 2100 pounds of useful paylod. Additional payload enhancement is possible with AOTV dry weight reductions due to technology advances in the areas of vehicle structures and thermal protection systems and other subsystems.

Florence, D. E.↗
NASA NTRS1983

A design study of a reaction control system for a V/STOL fighter/attack aircraft

Attention is given to a short takeoff vertical landing (STOVL) aircraft reaction control system (RCS) design study. The STOVL fighter/attack aircraft employs an existing turbofan engine, and its hover requirement places a premium on weight reduction, which eliminates prospective nonairbreathing RCSs. A simple engine compressor bleed RCS degrades overall performance to an unacceptable degree, and the supersonic requirement precludes the large volume alternatives of thermal or ejector thrust augmentation systems as well as the ducting of engine exhaust gases and the use of a dedicated turbojet. The only system which addressed performance criteria without requiring major engine modifications was a dedicated load compressor driven by an auxilliary power unit.

Beard, B. B.↗