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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 559 records · Page 31
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

Hatch Cover Slides Through Hatch

Hatch cover for pressurized vessel provides tight seal but opened quickly from either side. In opening or closing, cover sweeps out relatively little volume within vessel, so it does not hinder movement of people or objects from vessel to outside or placement of people or objects near hatch. Cover uses internal pressure to create seal when closed. Design of cover eliminates leakage paths, and cover immune to hazards of sudden decompression or jamming when bolts and latches fail.

Alton, Charles↗
NASA NTRS1989

A wide bandwidth electrostatic field sensor for lightning research

Data obtained from UHF radar observation of direct-lightning strikes to the NASA F-106B aircraft have indicated that most of the 690 strikes acquired during direct-strike lightning tests were triggered by the aircraft. As an aid in understanding the triggered lightning process, a wide bandwidth electric field measuring system was designed for the F-106B by implementing a clamped-detection signal processing concept originated at the Air Force Cambridge Research Lab in 1953. The detection scheme combines the signals from complementary stator pairs clamped to zero bolts at the exact moment when each stator pair is maximally shielded by the rotor, a process that restores the dc level lost by the charge amplifier. The system was implemented with four shutter-type field mills located at strategic points on the aircraft. The bandwidth of the system was determined in the laboratory to be from dc to over 100 Hz, whereas past designs had upper limits of 10 to 100 Hz. To obtain the undisturbed electric field vector and total aircraft charge, the airborne field mill system is calibrated by using techniques involving results from ground and flight calibrations of the F-106B, laboratory tests of a metallized model, and a finite difference time-domain electromagnetic computer code.

Zaepfel, Klaus P.↗
NASA NTRS1989

Space Shuttle Main Engine structural analysis and data reduction/evaluation. Volume 2: High pressure oxidizer turbo-pump turbine end bearing analysis

The high-pressure oxidizer turbopump (HPOTP) consists of two centrifugal pumps, on a common shaft, that are directly driven by a hot-gas turbine. Pump shaft axial thrust is balanced in that the double-entry main inducer/impeller is inherently balanced and the thrusts of the preburner pump and turbine are nearly equal but opposite. Residual shaft thrust is controlled by a self-compensating, non-rubbing, balance piston. Shaft hang-up must be avoided if the balance piston is to perform properly. One potential cause of shaft hang-up is contact between the Phase 2 bearing support and axial spring cartridge of the HPOTP main pump housing. The status of the bearing support/axial spring cartridge interface is investigated under current loading conditions. An ANSYS version 4.3, three-dimensional, finite element model was generated on Lockheed's VAX 11/785 computer. A nonlinear thermal analysis was then executed on the Marshall Space Flight Center Engineering Analysis Data System (EADS). These thermal results were then applied along with the interference fit and bolt preloads to the model as load conditions for a static analysis to determine the gap status of the bearing support/axial spring cartridge interface. For possible further analysis of the local regions of HPOTP main pump housing assembly, detailed ANSYS submodels were generated using I-DEAS Geomod and Supertab (Appendix A).

Sisk, Gregory A.↗
NASA NTRS1989

Effect of design variables, temperature gradients, and speed on life and reliability of a rotating disk

A generalized methodology to predict the fatigue life and reliability of a rotating disk such as used for aircraft engine turbines and compressors is advanced. The approach incorporates the computed life of elemental stress volumes to predict system life and reliability. Disk speed and thermal gradients as well as design varibles such as disk diameter and thickness and bolt hole size, number and location are considered.

Zaretsky, E. V.↗
NASA NTRS1990

Static Pressure-Assisted Seal For Helium

Two-piece, all-metal, pressure-assisted static flange seal holds in pressurized helium satisfactorily at temperature of negative 80 degree F (negative 62 degree C). Installed between two flanges, then bolted together. New version includes one pressure-assisted metal sealing element held in place by metal plate and flanges. Certified for use in flight on helium joints of Space Shuttle main engine. Likely terrestrial applications include laboratory and industrial gas-distribution systems.

Stuck, Donald E.↗
NASA NTRS1990

Cheap Corner Reflectors For Radar

Corner reflectors for radar constructed easily and inexpensively. Wire mesh on plastic pipe forms retroreflective panels of triangular or square shape. Panels joined by bolts and wingnuts. Overlapping panel edges ensure mutual perpendicularity. Materials for new reflectors found in hardware and building-supply stores. No special skills or tools needed for assembly.

Caro, E. R.↗
NASA NTRS1990

Relevance of impacter shape to nonvisible damage and residual tensile strength of a thick graphite/epoxy laminate

A study was made to determine the relevance of impacter shape to nonvisible damage and tensile residual strength of a 36 mm (1.4 in.) thick graphite/epoxy motor case. The shapes of the impacters were as follows: 12.7 mm (0.5 in.) and 25.4 mm (1.0 in.) diameter hemispheres, a sharp corner, and a 6.3 mm (0.25 in.) diameter bolt-like rod. The investigation revealed that damage initiated when the contact pressure exceeded a critical level. However, the damage was not visible on the surface until an even higher pressure was exceeded. The damage on the surface consisted of a crater shaped like the impacter, and the damage below the surface consisted of broken fibers. The impact energy to initiate damage or cause visible damage on the surface increased approximately with impacter diameter to the third power. The reduction in strength for nonvisible damage increased with increasing diameter, 9 and 30 percent for the 12.7 mm (0.5 in.) and 25.4 mm (1.0 in.) diameter hemispheres, respectively. The corner impacter made visible damage on the surface for even the smallest impact energy. The rod impacter acted like a punch and sliced through the composite. Even so, the critical level of pressure to initiate damage was the same for the rod and hemispherical impacters. Factors of safety for nonvisible damage increased with increasing kinetic energy of impact. The effects of impacter shape on impact force, damage size, damage visibility, and residual tensile strength were predicted quite well assuming Hertzian contact and using maximum stress criteria and a surface crack analysis.

Poe, C. C., Jr.↗
NASA NTRS1990

Flight set 360T004 (STS-30)

The performance of 360T004, Forth Flight, Redesigned Solid Rocket Motors (RSRM) is assessed in respect to joint sealing issues as seen from post-test inspection of the seals and sealing surfaces. The factory joint disassembly inspections for this flight set were omitted. The decision was based on the rational that there is sufficient information in the present data base, and this would give H-7 refurbishment operations faster turn around time for this set of hardware. The factory joint disassembly inspections will resume for 360H005, Fifth Flight, through 360L007, Seventh Flight, due to a new grease application being in effect during the assembly process. The left hand nozzle was forced into the snubbed position upon splash down. This required unique tooling to be manufactured to perform the disassembly of the internal nozzle joints. This was completed on February 5 and 6, 1990 at the H-5 Clearfield, Utah facility. The RSRM consisting of capture feature, field joints with the J-joint insulation configuration is illustrated. The nozzle-to-case joint design, which includes 100, 7/8-inch radial bolts in conjunction with a wiper O-ring and modified insulation design is also illustrated, as is the ignition system seals and a cross section of the igniter. The configuration of all internal nozzle joints is shown.

Nelsen, Lowell V.↗
NASA NTRS1990

Design of a telescoping tube system for access and handling equipment

Spacecraft processing presents unique problems for the design of ground support equipment. A telescoping tube system consists of a number of nested structural tubes that can be extended and retracted (telescoped) while supporting a load. A typical telescoping tube system provides lateral, torsional, and vertical support for an access platform. Several concepts for improved telescoping tubes were developed with emphasis placed on reliability, ease of maintenance, and cost effectiveness. The most promising prototype design utilizes adjustable rollers running on tracks bolted to the tube sections. A wire rope deployment system ensures that all tube sections are controlled during extension and retraction. Track shimming and roller adjustment allow for fabrication of a high precision tube assembly that does not require extensive machining or unusually large shop equipment. The use of rolling contact eliminates the contamination problems encountered with sliding tubes in previous designs. The prototype design is suitable for indoor or outdoor use. A prototype tube assembly was fabricated and tested for strength, stiffness, maintainability, and endurance.

Littlefield, Alan C.↗
NASA NTRS1990

Space environment robot vision system

A prototype twin-camera stereo vision system for autonomous robots has been developed at Goddard Space Flight Center. Standard charge coupled device (CCD) imagers are interfaced with commercial frame buffers and direct memory access to a computer. The overlapping portions of the images are analyzed using photogrammetric techniques to obtain information about the position and orientation of objects in the scene. The camera head consists of two 510 x 492 x 8-bit CCD cameras mounted on individually adjustable mounts. The 16 mm efl lenses are designed for minimum geometric distortion. The cameras can be rotated in the pitch, roll, and yaw (pan angle) directions with respect to their optical axes. Calibration routines have been developed which automatically determine the lens focal lengths and pan angle between the two cameras. The calibration utilizes observations of a calibration structure with known geometry. Test results show the precision attainable is plus or minus 0.8 mm in range at 2 m distance using a camera separation of 171 mm. To demonstrate a task needed on Space Station Freedom, a target structure with a movable I beam was built. The camera head can autonomously direct actuators to dock the I-beam to another one so that they could be bolted together.

Wood, H. John↗
NASA NTRS1990

Thermal/structural analysis of the shaft-disk region of a fan drive system

In January 1989, a mishap occurred in the National Transonic Facility wind tunnel at NASA-Langley. It is believed that the failure of an insulation retainer holding foam insulation around the exterior of the fan drive shaft resulted in the subsequent damage to other components in the tunnel. The effect was determined of removing the external thermal insulation on the shaft would have on the stresses on the shaft, disk and bolts holding the two together. To accomplish this, a detailed thermal/structural finite element analysis of the shaft-disk interface was performed. The maximum stresses on the three components were determined for several configurations and conditions with and without the external thermal insulation, and then these results were compared to the original analyses to access the effect of removing the external thermal insulation on the proposed future operation of the shaft/disk structures of the fan drive system. Although the stresses were higher without the external insulation, the stresses did meet all stress criteria. In addition, all stresses were within the infinite life regime of the Modified Goodman diagram. Therefore, it was determined that the structural integrity of the shaft-disk region is not compromised if the external insulation is removed.

Gregory, Peyton B.↗
NASA NTRS1990

Simplified design procedures for fiber composite structural components/joints

Simplified step-by-step design procedures are summarized, which are suitable for the preliminary design of composite structural components such as panels (laminates) and composite built-up structures (box beams). Similar procedures are also summarized for the preliminary design of composite bolted and adhesively bonded joints. The summary is presented in terms of sample design cases complemented with typical results. Guidelines are provided which can be used in the design selection process of composite structural components/joints. Also, procedures to account for cyclic loads, hygrothermal effects and lamination residual stresses are included.

Murthy, P. L. N.↗
NASA NTRS1990

Summary of a study to determine low-velocity impact damage and residual tension strength for a thick graphite/epoxy motor case

Impacters of various shapes and masses were dropped from various heights onto 36 mm (1.4 in.) thick graphite/epoxy cylinders, which represented filament wound cases (FWC) for the booster motors of the Space Shuttle. Insert solid propellant was cast into some of the cylinders. The cylinders were impacted numerous times around the circumference and then cut into 51 mm (2.0 in.) wide tension specimens, each containing an impact site. Four indenters were used: a sharp corner, two hemispheres, and a bolt-like rod. The diameters of the hemispheres were 12.7 mm mm (0.5 in.) and 25.4 mm (1.0 in.), and the diameter of the rod was 6.3 mm (0.25 in.). Impacts with the rod were simulated by pressing the rod against the face of specimens. For the hemispheres, the damage initiated beneath the surface at a critical contact pressure and was not visible on the surface until an even larger pressure was exceeded. The damage consisted of matrix cracking and broken fiber. The rod an corner made visible surface damage in all tests. For the hemispheres, the tension strength was reduced considerably before the damage was visible on the surface, 30 percent for the 25.4 mm (1.0 in.) diameter hemisphere and 10 percent for the 12.7 mm (0.5 in.) diameter hemisphere. Analytical methods were used to predict the damage and residual tension strength. A factor of safety to account for nonvisible damage was determined.

Poe, C. C., Jr.↗
NASA NTRS1990

Flight set 360L001 (STS-26) igniter, post flight

Space Transportation System (STS-26) was launched from KSC pad 39B. Two of the Redesigned Solid Rocket Motors (RSRM) were part of the launch system and are designated RSRM-1A and RSRM-1B. Each of these motors were initiated by an 1U75164 igniter. The post flight condition of the igniters and associated components is documented. The overall performance of the igniter components was excellent. No damage or heat affected areas were noted. The sealing elements of the igniter functioned as expected with no evidence of erosion or blowby. The thermal protection system protected all areas adequately. No excessive erosion was noted. Corrosion was found in the special bolt holes in the igniter chamber. The corrosion will not affect refurbishment of the chamber. Beginning with flight 5 grease has been added to the chamber holes to prevent this erosion.

Hale, Elgie J.↗
NASA NTRS1990

Igniter adapter-to-igniter chamber deflection test

Testing was performed to determine the maximum RSRM igniter adapter-to-igniter chamber joint deflection at the crown of the inner joint primary seal. The deflection data was gathered to support igniter inner joint gasket resiliency predictions which led to launch commit criteria temperature determinations. The proximity (deflection) gage holes for the first test (Test No. 1) were incorrectly located; therefore, the test was declared a non-test. Prior to Test No. 2, test article configuration was modified with the correct proximity gage locations. Deflection data were successfully acquired during Test No. 2. However, the proximity gage deflection measurements were adversely affected by temperature increases. Deflections measured after the temperature rise at the proximity gages were considered unreliable. An analysis was performed to predict the maximum deflections based on the reliable data measured before the detectable temperature rise. Deflections to the primary seal crown location were adjusted to correspond to the time of maximum expected operating pressure (2,159 psi) to account for proximity gage bias, and to account for maximum attach and special bolt relaxation. The maximum joint deflection for the igniter inner joint at the crown of the primary seal, accounting for all significant correction factors, was 0.0031 in. (3.1 mil). Since the predicted (0.003 in.) and tested maximum deflection values were sufficiently close, the launch commit criteria was not changed as a result of this test. Data from this test should be used to determine if the igniter inner joint gasket seals are capable of maintaining sealing capability at a joint displacement of (1.4) x (0.0031 in.) = 0.00434 inches. Additional testing should be performed to increase the database on igniter deflections and address launch commit criteria temperatures.

Cook, M.↗
NASA NTRS1990

Flight set 360H005 (STS-28) seals, volume 4

The performance is assessed of the 360H005, Fifth flight, Redesigned Solid Rocket Motors (RSMR) in respect to joint sealing issues as seen from post flight inspection of the seals and sealing surfaces. The factory joint disassembly inspections have resumed for 360H005. The new factory joint grease application is in effect and now can be assessed during the disassembly process. The RSRM is illustrated consisting of capture feature field joints as is the J-joint insulation configuration. The nozzle-to-case joint design is also illustrated, which includes 100, 7/8 inch radial bolts in conjunction with a wiper O-ring and modified insulation design. The ignition system seals and a cross section of the igniter are illustrated. The configuration of all the internal nozzle joints are also shown. The postflight inspection of both motors showed the seal components to be in excellent condition except for the indentation found on the inner primary seal of the right hand inner igniter gasket, aft face. Detailed inspection results, and inspections performed by the O-ring Inspection Team are presented.

Curry, Jeffrey T.↗
NASA NTRS1990

Advanced NDE techniques for quantitative characterization of aircraft

Recent advances in nondestructive evaluation (NDE) at NASA Langley Research Center and their applications that have resulted in quantitative assessment of material properties based on thermal and ultrasonic measurements are reviewed. Specific applications include ultrasonic determination of bolt tension, ultrasonic and thermal characterization of bonded layered structures, characterization of composite materials, and disbonds in aircraft skins.

Heyman, Joseph S.↗
NASA NTRS1990

The vortex flap F-106B, overcoming safety and data problems in flight testing

A NASA, F-106B airplane equipped with a vortex flap is establishing a data base for calibration of design and analysis tools for this vortical flow control concept. Some of the problems in safely and precisely flying to research data points were caused by the modified airplane's low longitudinal stability and low margin of structural strength. These characteristics are, in part, a consequence of the program's low cost approach which utilizes a bolt-on, ground-adjustable flap attached to a minimally modified airplane. Presently, the 40-degree flap deflection flight research is being concluded with a flow visualization phase. A similar pattern of flight envelope expansion, pressure distribution, performance, and flow visualization phases remain to be accomplished for the 30-degree flap setting. To date, good research flight data has followed resolution of the safety and data problems described.

Brown, Philip W.↗