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NASA NTRS1999

Space Shuttle Orbital Maneuvering Subsystem (OMS) Engine Propellant Leakage Ball-Valve Shaft Seals

Evidence of propellant leakage across ball-valve shaft seals has been noted during the disassembly of five flight engines and one test engine at the NASA Lyndon B. Johnson Space Center, White Sands Test Facility. Based on data collected during the disassembly of these five engines, the consequences of propellant leakage across the ball-valve shaft seals can be divided into four primary areas of concern: Damage to the ball-valve pinion shafts, damage to sleeved bearings inside the ball-valve and actuator assemblies, degradation of the synthetic rubber o-rings used in the actuator assemblies, and corrosion and degradation to the interior of the actuator assemblies. The exact time at which leakage across the ball-valve shaft seals occurs has not been determined, however, the leakage most likely occurs during engine firings when, depending on the specification used, ball-valve cavity pressures range as high as 453 to 550 psia. This potential pressure range for the ball-valve cavities greatly exceeds the acceptance leakage test pressure of 332 psia. Since redesign and replacement of the ball-valve shaft seals is unlikely, the near term solution to prevent damage that occurs from shaft-seal leakage is to implement a routine overhaul and maintenance program for engines in the fleet. Recommended repair, verification, and possible preventative maintenance measures are discussed in the paper.

Lueders, Kathy↗

NASA NTRS2000

Development of a Enhanced Thermal Barrier for RSRM Nozzle Joints

A carbon fiber rope is being considered as replacement for the RTV thermal barrier that is currently used to protect o-rings in RSRM nozzle joints, Performance requirements include its ability to cool propellant gases filter slag and particulates, and conform to various joint assembly conditions as well as dynamic flight motion. Testing has shown its superior heat resistance, even in oxidative and corrosive environments. Testing has also demonstrated excellent performance of this system in sub-scale motors. Cold flow testing, has demonstrated its ability to conform to motor dynamics. Manufacture and assembly testing have demonstrated the ease of gland machining as well as assembly in a full-scale nozzle.

Bauer, P. H.↗

NASA NTRS2001

MNASA as a Test for Carbon Fiber Thermal Barrier Development

A carbon fiber rope thermal barrier is being evaluated as a replacement for the conventional room temperature vulcanizing (RTV) thermal barrier that is currently used to protect o-rings in Reusable Solid Rocket Motor (RSRM) nozzle joints. Performance requirements include its ability to cool any incoming, hot propellant gases that fill and pressurize the nozzle joints, filter slag and particulates, and to perform adequately in various joint assembly conditions as well as dynamic flight motion. Modified National Aeronautics and Space Administration (MNASA) motors, with their inherent and unique ability to replicate select RSRM internal environment features, were an integral step in the development path leading to full scale RSRM static test demonstration of the carbon fiber rope (CFR) joint concept. These 1/4 scale RSRM motors serve to bridge the gap between the other classes of subscale test motors (extremely small and moderate duration, or small scale and short duration) and the critical asset RSRM static test motors. A series of MNASA tests have been used to demonstrate carbon fiber rope performance and have provided rationale for implementation into a full-scale static motor and flight qualification.

Bauer, Paul↗

NASA NTRS2001

Portable Hyperbaric Chamber

A portable, collapsible hyperbaric chamber was developed. A toroidal inflatable skeleton provides initial structural support for the chamber, allowing the attendant and/or patient to enter the chamber. Oval hatches mate against bulkhead rings, and the hyperbaric chamber is pressurized. The hatches seal against an o-ring, and the internal pressure of the chamber provides the required pressure against the hatch to maintain an airtight seal. In the preferred embodiment, the hyperbaric chamber has an airlock to allow the attendant to enter and exit the patient chamber during treatment. Visual communication is provided through portholes in the patient and/or airlock chamber. Life monitoring and support systems are in communication with the interior of the hyperbaric chamber and/or airlock chamber through conduits and/or sealed feed-through connectors into the hyperbaric chamber.

Schneider, William C.↗

NASA NTRS1999

Design and Development of Lightweight Composite Tanks for the Mars Ascent Propulsion Technology

The investigation presented here focuses on the design and development of lightweight composite tanks for the Mars ascent propulsion technology. The proposed tanks are fabricated using the filament winding technique. The tanks will be used in the experimental permeability characterization of composite pressure vessels pressurized using cryogenic and kerosene fluids. We considered the geometry and composite material tailorability in the preliminary design formulation to obtain an isotensoid tank. The design formulation is based on membrane shell analysis. The tanks also include circular openings at the apex of the end caps for the installation of polar bosses. The development of a polar boss system was also investigated, and led to an innovative polar boss system that applies a uniform pressure on the o-ring gaskets. The permeability of these tanks was also considered and recommendations for improvement are presented.

Estrada, Hector↗

NASA NTRS1988

Laboratory Tool

Veterans Administration medical researchers, along with Langley Research Center are investigating possibility that peritoneal membrane (lining of abdominal cavity) can absorb nutrients and thus provide alternative route for nutrition when intestinal function is impaired. Apparatus (cake box design) consists of octagonal chamber with eight smaller chambers attached and secured by O-ring seals. Design is simple, interchangeable, and time controllable.

Source record↗

NASA NTRS2002

DMA Modulus as a Screening Parameter for Compatibility of Polymeric Containment Materials with Various Solutions for use in Space Shuttle Microgravity Protein Crystal Growth (PCG) Experiments

Protein crystals are grown in microgravity experiments inside the Space Shuttle during orbit. Such crystals are basically grown in a five-component system containing a salt, buffer, polymer, organic and water. During these experiments, a number of different polymeric containment materials must be compatible with up to hundreds of different PCG solutions in various concentrations for durations up to 180 days. When such compatibility experiments are performed at NASA/MSFC (Marshall Space Flight Center) simultaneously on containment material samples immersed in various solutions in vials, the samples are rather small out of necessity. DMA4 modulus was often used as the primary screening parameter for such small samples as a pass/fail criterion for incompatibility issues. In particular, the TA Instruments DMA 2980 film tension clamp was used to test rubber O-rings as small in I.D. as 0.091 in. by cutting through the cross-section at one place, then clamping the stretched linear cord stock at each end. The film tension clamp was also used to successfully test short length samples of medical/surgical grade tubing with an O.D. of 0.125 in.

Wingard, Charles Doug↗

NASA NTRS2002

Assessment of Various Flow Solvers Used to Predict the Thermal Environment inside Space Shuttle Solid Rocket Motor Joints

It is very important to accurately predict the gas pressure, gas and solid temperature, as well as the amount of O-ring erosion inside the space shuttle Reusable Solid Rocket Motor (RSRM) joints in the event of a leak path. The scenarios considered are typically hot combustion gas rapid pressurization events of small volumes through narrow and restricted flow paths. The ideal method for this prediction is a transient three-dimensional computational fluid dynamics (CFD) simulation with a computational domain including both combustion gas and surrounding solid regions. However, this has not yet been demonstrated to be economical for this application due to the enormous amount of CPU time and memory resulting from the relatively long fill time as well as the large pressure and temperature rising rate. Consequently, all CFD applications in RSRM joints so far are steady-state simulations with solid regions being excluded from the computational domain by assuming either a constant wall temperature or no heat transfer between the hot combustion gas and cool solid walls.

Wang, Qun-Zhen↗

NASA NTRS2003

Investigation Leads to Improved Understanding of Space Shuttle RSRM Internal Insulation Joints

The Space Shuttle Reusable Solid Rocket Motor (RSRM) uses an internal insulation J-joint design for the mated insulation interface between two assembled RSRM segments. In this assembled (mated) segment configuration, this J-joint design serves as a thermal barrier to prevent hot gases from affecting the case field joint metal surfaces and O-rings. A pressure sensitive adhesive (PSA) provides some adhesion between the two mated insulation surfaces. In 1995, after extensive testing, a new ODC-free PSA (free of ozone depleting chemicals) was selected for flight on RSRM-55 (STS-78). Post-flight inspection revealed that the J-joint, equipped with the new ODC-free PSA, did not perform well. Hot gas seeped inside the J-joint interface. Although not a flight safety threat, the J-joint hot gas intrusion on RSRM-55 was a mystery to the investigators since the PSA had previously worked well on a full-scale static test. A team was assembled to study the J-joint and PSA further. All J-joint design parameters, measured data, and historical performance data were re-reviewed and evaluated by subscale testing and analysis. Although both the ODC-free and old PSA were weakened by humidity, the ODC-free PSA strength was lower to start with. Another RSRM full-scale static test was conducted in 1998 and intentionally duplicated the gas intrusion. This test, along with many concurring tests, showed that if a J-joint was 1) mated with the new ODC-free PSA, 2) exposed to a history of high humidity (Kennedy Space Center levels), and 3) also a joint which experienced significant but normal joint motion (J-joint deformation resulting from motor pressurization dynamics) then that J-joint would open (allow gas intrusion) during motor operation. When all of the data from the analyses, subscale tests, and full-scale tests were considered together, a theory emerged. Most of the joint motion on the RSRM occurs early in motor operation at which point the J-joints are pulled into tension. If the new PSA has been weakened due to humidity, then the J-joint will partially pull apart (inboard side), and the J-joint surfaces will be charred by exposure to hot gases. After early operation, a J-joint that has been pulled apart will come back together as the J-joint deformation decreases. This J-joint heating event is relatively short and occurs only during the first part of motor operation. Internal instrumentation was developed for another full-scale static test in February 2000. The static test instrumentation did indeed prove this theory to be correct. Post-test inspection revealed very similar charring characteristics as observed on RSRM-55. This experience of the development of a new PSA, its testing, the RSRM-55 flight, followed by the J-joint investigation led to good 'lessons learned' and to an additional fundamental understanding of the RSRM J-joint function.

McWhorter, Bruce B.↗

NASA NTRS2003

Development of Displacement Gages Exposed to Solid Rocket Motor Internal Environments

The Space Shuttle Reusable Solid Rocket Motor (RSRM) has three non-vented segment-to-segment case field joints. These joints use an interference fit J-joint that is bonded at assembly with a Pressure Sensitive Adhesive (PSA) inboard of redundant O-ring seals. Full-scale motor and sub-scale test article experience has shown that the ability to preclude gas leakage past the J-joint is a function of PSA type, joint moisture from pre-assembly humidity exposure, and the magnitude of joint displacement during motor operation. To more accurately determine the axial displacements at the J-joints, two thermally durable displacement gages (one mechanical and one electrical) were designed and developed. The mechanical displacement gage concept was generated first as a non-electrical, self-contained gage to capture the maximum magnitude of the J-joint motion. When it became feasible, the electrical displacement gage concept was generated second as a real-time linear displacement gage. Both of these gages were refined in development testing that included hot internal solid rocket motor environments and simulated vibration environments. As a result of this gage development effort, joint motions have been measured in static fired RSRM J-joints where intentional venting was produced (Flight Support Motor #8, FSM-8) and nominal non-vented behavior occurred (FSM-9 and FSM-10). This data gives new insight into the nominal characteristics of the three case J-joint positions (forward, center and aft) and characteristics of some case J-joints that became vented during motor operation. The data supports previous structural model predictions. These gages will also be useful in evaluating J-joint motion differences in a five-segment Space Shuttle solid rocket motor.

Bolton, D. E.↗

NASA NTRS2002

Facility and Methods Developed for Simulated Space Vacuum Ultraviolet Exposure Testing of Polymer Films

Vacuum ultraviolet (VUV) radiation of wavelengths between 115 and 200 nm produced by the Sun in the space environment can degrade polymer films, producing changes in their optical, mechanical, and chemical properties. These effects are particularly important for thin polymer films being considered for ultralightweight space structures, because, for most polymers, VUV radiation is absorbed in a thin surface layer. The NASA Glenn Research Center has developed facilities and methods for long-term ground testing of polymer films to evaluate space environmental VUV radiation effects. VUV exposure can also be used as part of combined or sequential simulated space environmental exposures to determine combined damaging effects with other aspects of the space environment, which include solar ultraviolet radiation, solar flare x-rays, electron and proton radiation, atomic oxygen (for low-Earth-orbit missions), and temperature effects. Because the wavelength sensitivity of VUV damage is not well known for most materials, Glenn's VUV facility uses a broad-spectrum deuterium lamp with a magnesium fluoride window that provides output between 115 and 200 nm. Deuterium lamps of this type were characterized by the National Institute of Standards and Technology and through measurements at Glenn. Spectral irradiance measurements show that from approximately 115 to 160 nm, deuterium lamp irradiance can be many times that of air mass zero solar irradiance, and as wavelength increases above approximately 160 nm, deuterium lamp irradiance decreases in comparison to the Sun. The facility is a cryopumped vacuum chamber that achieves a system pressure of approximately 5310(exp -6) torr. It contains four individual VUV-exposure compartments in vacuum, separated by water-cooled copper walls to minimize VUV radiation and any sample contamination cross interactions between compartments. Each VUV-exposure compartment contains a VUV deuterium lamp, a motor-controlled sample stage coupled with a moveable cesium iodide VUV phototube, and two thermocouples for temperature measurement. The vacuum chamber and exterior equipment is shown. Each VUV lamp is located at the top of the chamber with its projection-tube pushed through an O-ring compression fitting. The lamp assemblies are located on ports that can be isolated from the rest of the vacuum chamber, permitting maintenance or replacement of the lamps without breaking vacuum in the main chamber where the samples are located. A view of two of the four interior VUV-exposure compartments, including the moveable sample stages and detector holders is also shown. Glenn is using this facility to support testing of Next Generation Space Telescope sunshield materials that is being led by the NASA Goddard Space Flight Center and to develop an understanding of the wavelength, intensity, and temperature dependence of VUV-induced polymer degradation.

Dever, Joyce A.↗

NASA NTRS2007

A Rapid Survey of the Compatibility of Selected Seal Materials with Conventional and Semi-Synthetic JP-8

Since the synthesis of a liquid hydrocarbon fuel from coal by Franz Fischer and Hans Tropsch in 1923, there has been cyclic interest in developing this fuel for military and commercial applications. In recent years the U.S. Department of Defense has taken interest in producing a unified battlespace fuel using the Fischer Tropsch (FT) process for a variety of reasons including cost, quality, and logistics. In the past year there has been a particular emphasis on moving quickly to demonstrate that an FT fuel can be used in the form of a blend with conventional petroleum-derived jet fuel. The initial objective is to employ this semi-synthetic fuel with blend ratios as high as 50 percent FT with longer range goals to use even high blend ratios and ultimately a fully synthetic jet fuel. A significant concern associated with the use of a semi-synthetic jet fuel with high FT blend ratios is the effect these low aromatic fuels will have on fuel-wetted polymeric materials, most notably seals and sealants. These materials typically swell and soften to some degree when exposed to jet fuel and the aromatic content of these fuels contribute to this effect. Semi-synthetic jet fuels with very low aromatic contents may cause seals and sealants to shrink and harden leading to acute or chronic failure. Unfortunately, most of the material qualification tests are more concerned with excessive swelling than shrinkage and there is little guidance offered as to an acceptable level of shrinkage or other changes in physical properties related to low aromatic content. Given the pressing need for guidance data, a program was developed to rapidly survey the volume swell of selected fuel-wetted materials in a range of conventional and semi-synthetic jet fuels and through a statistical analysis to make a determination as to whether there was a basis to be concerned about using fuels with FT blend ratios as high as 50 percent. Concurrent with this analysis data was obtained as to the composition of the fuel absorbed in fuel-wetted materials through the use of GC-MS analysis of swollen samples as well as other supporting data. In this presentation the authors will present a summary of the results of the volume swell and fuel absorbed by selected O-rings and sealants as well as a description of the measurement protocols developed for this program.

Graham, John L.↗

NASA NTRS2004

Variable pressure washer

A variable pressure washer has two interlocking channel rings separated by a channel and retained by a captive set of fasteners. Within the channel between the rings are multiple rows of springs having at least two different spring moduli. The washer is particularly suited for use with a polar boss assembly secured to a bulkhead of a pressure vessel such as of propellent tank dome structure where the washer allows for the substantially uniform deflection of multiple O-rings as affected by the curved structure.

Smeltzer, III, Stanley S.↗

NASA NTRS1988

Ampoule sealing apparatus and process

An apparatus 10 for effecting sealing of a fused quartz ampoule 24 while maintaining a vacuum on the ampoule via system 12 is disclosed. A plug 28 of fused quartz is lowered into the vertically disposed ampoule 24 (while maintaining the vacuum thereon) and heat sealed therein to prevent any vapor escape from, or contamination of, the contained semiconductor growth charge 29 during subsequent semiconductor crystal growth processes. A rotary vacuum feed-through mechanism 16 selectively rotates axle 34 and spool 32 to unwind wire 30 for lowering of plug 28 into the reduced diameter portion 24b of ampoule 24. Ampoule 24 is hermatically connected to vacuum housing 18 by quick release flange 20 wherein O-ring 22 retains ampoule 24.

Debnam, Jr., William J.↗

NASA NTRS2010

What if Things Get Worse? Really Grand Challenges for Modeling and Simulation in a Risky and Complex World or Modeling and Simulation for the "Greater Good"?

Today Modeling and Simulation-- ---as an important practice or industry or area of expertise ----- is at a complex crossroad - a sort of cyber-highway--where these complexities meet-technical, economic, environmental, geopolitical and cultural. They may converge or collide. Let's not kid ourselves. It is all too much for anyone person or organization Malcolm Gladwell said it. "We have constructed a world in which the potential for high tech catastrophe is embedded in the fabric of everyday life." We are surrounded by problems that scream at us from our television, Internet and social networks along with billboards and protest signs. We face not just high tech catastrophes but, also, landslides, earthquakes, tornados, floods and hurricanes and large-scale criminality. Evil, war, famine and pestilence have not gone away. It is all too much to think about. My friend, George Peabody, who taught me everything I know about power said that addressing such issues requires that we constantly build our network, information resources and the credibility and visibility of our work. That is how we will build the power of simulation so it can change the world --even maybe, save it. We need all the help we can get and give one another because our human early warning systems appear to be out of kilter. We seem to have trouble imagining how small failings can continue to lead to catastrophic disaster. Think about O-rings and blowout preventers. One is reminded of the old nursery rhyme, "For want of a nail, a shoe was lost! for want of a shoe the horse was lost! for want of a rider the battle was lost and so the kingdom fell." Although the investigation will take more time for real answers, it is worrisome that a rig worker reported to the BBC that-- weeks before the explosion of Deep Ocean Horizon. -he identified a leak in the oil rig's safety equipment -the Control Pod of the blowout preventer which has giant shears designed to cut and seal off the well's main pipe. With both electronics and hydraulics, these are effectively the brains of the blowout preventer. No one fixed it, he alleges, they just shut it down and relied on the other control pod -an act deemed unacceptable by petroleum expert, Tad Patzek, at the University of Texas. The US Congress has identified numerous other problems with the blowout preventer, including design problems and unexpected modifications.

Fifrey, Priscilla↗

NASA NTRS1995

NASA Tech Briefs, November 1995

The contents include: 1) Mission Accomplished; 2) Resource Report: Marshall Space Flight Center; 3) NASA 1995 Software of the Year Award; 4) Microbolometers Based on Epitaxial YBa2Cu3O(sub 7-x) Thin Films; 5) Garnet Random-Access Memory; 6) Fabrication of SNS Weak Links on SOS Substrates; 7) High-Voltage MOSFET Switching Circuit; 8) Asymmetric Switching for a PWM H-Bridge Power Circuit; 9) Better Ohmic Contacts for InP Semiconductor Devices; 10) Low-Bandgap Thermovoltaic Materials and Devices; 11) Digital Frequency-Differencing Circuit; 12) Imaging Magnetometer; 13) Computer-Assisted Monitoring of a Complex System; 14) Buffered Telemetry Demodulator; 15) Compact Multifunction Inspection Head; 16) Optical Detection of Fractures in Ceramic Diaphragms; 17) Eddy-Current Detection of Cracks in Reinforced Carbon/Carbon; 18) Apparent Thermal Conductivity of Multilayer Insulation; 19) Optimizing Misch-Metal Compositions in Metal Hydride Anodes; 20) Device for Sampling Surface Contamination; 21) Probabilistic Failure Assessment for Fatigue; 22) Probabilistic Fatigue and Flaw-Propagation Analysis; 23) Windows Program for Driving the TDU-850 Printer; 24) Subband/Transform MATLAB Functions for Processing Images; 25) Computing Equilibrium Chemical Compositions; 26) Program Processes Thermocouple Readings; 27) ICAN-Second-Generation Integrated Composite Analyzer; 28) Integrated Composite Analyzer with Damping Capabilities; 29) Computing Efficiency of Transfer of Microwave Power; 30) Program Calculates Power Demands of Electronic Designs; 31) Cost-Estimation Program; 32) Program Estimates Areas Required by Electronic Designs; 33) Program to Balance Mapped Turbopump Assemblies; 34) BiblioTech; 35) Controlling Mirror Tilt With a Bimorph Actuator; 36) Burst-Disk Device Simulates Effect of Pyrotechnic Device; 37) Bearing-Mounting Concept Accommodates Thermal Expansion; 38) Parallel-Plate Acoustic Absorbers for Hot Environments; 39) Adjustable-Length Strut Withstands Large Cyclic Loads; 40) Tool Indicates Contact Angles in Bearing Raceways; 41) Gravity Slides With Magnetic Braking; 42) High-Torque, Lightweight, Pneumatically Driven Wrench for Small Spaces; 43) Device for Testing Compatibility of an O-Ring; 44) Magnetic Heat Pump Containing Flow Diverters; 45) Variable-Tilt Helicopter Rotor Mast; 46) "Beach-Ball" Robotic Rovers; 47) Apparatus Would Measure Temperatures of Ball Bearings; 48) Flexible Borescope for Inspecting Ducts; 49) Texturing Copper To Reduce Secondary Emission of Electrons; 50) Automated Laser Cutting in Three Dimensions; 51) Algorithm Helps Monitor Engine Operation; 52) Flexible Revision of Data-Processing Communications; 53) Software for Managing the Use of Land; 54) Thermal Strap Increases Cryocooling Efficiency; 55) Reversible Nut With Engagement Indication; 56) Control Algorithms for Kinematically Redundant Manipulators; 57) Computed Hydrogen-Flow Splits in a Rocket Engine; 58) Pressure and Thermal Modeling of Rocket Launches; 59) Field of View of a Spacecraft Antenna: Analysis and Software; 60) Digital Controller for Laser-Beam-Steering Subsystem; 61) More About Beam-Steering Subsystem for Laser Communication; 62) Digital Controller for Laser-Beam-Steering Subsystem: Part 2; 63) Interface Circuit Board for Space-Shuttle Communications; 64) Automated Planning of Spacecraft Telecommunications; 65) Artifacts of Spectral Analysis of Instrument Readings; 66) Neural-Network Controller for Vibration Suppression; 67) Adaptive Finite-Element Computation in Fracture Mechanics; 68) Attitude Control for the Cassini Spacecraft; 69) Analytical Model for Fluid Dynamics in a Microgravity Environment; 70) Study of Rocket-Engine Joints Bonded by NVCU/NARloy-Z; 71) Improved Silicon Nitride for Advanced Heat Engines; 72) Parameters for Welding Aluminum/Lithium Alloys; 73) Lightweight Composite Intertank Structure; 74) Foil Patches Seal Small Vacuum Leaks; 75) Data Base on Cables and Connectors; 76) Effect of Clock Mode on Radiation Hardnessf an ADC; and 77) Fault-Tolerant Control for a Robotic Inspection System.

Source record↗

NASA NTRS2006

System for Continuous Deaeration of Hydraulic Oil

A system for continuous, rapid deaeration of hydraulic oil has been built to replace a prior system that effected deaeration more slowly in a cyclic pressure/ vacuum process. Such systems are needed because (1) hydraulic oil has an affinity for air, typically containing between 10 and 15 volume percent of air and (2) in the original application for which these systems were built, there is a requirement to keep the proportion of dissolved air below 1 volume percent because a greater proportion can lead to pump cavitation and excessive softness in hydraulic-actuator force-versus-displacement characteristics. In addition to overcoming several deficiencies of the prior deaeration system, the present system removes water from the oil. The system (see figure) includes a pump that continuously circulates oil at a rate of 10 gal/min (38 L/min) between an 80-gal (303-L) airless reservoir and a tank containing a vacuum. When the circulation pump is started, oil is pumped, at a pressure of 120 psi (827 kPa), through a venturi tube below the tank with a connection to a stand-pipe in the tank. This action draws oil out of the tank via the standpipe. At the same time, oil is sprayed into the tank in a fine mist, thereby exposing a large amount of oil to the vacuum. When the oil level in the tank falls below the lower of two level switches, a vacuum pump is started, drawing a hard vacuum on the tank through a trap that collects any oil and water entrained in the airflow. When the oil level rises above higher of the two level switches or when the system is shut down, a solenoid valve between the tank and the vacuum pump is closed to prevent suction of oil into the vacuum pump. Critical requirements that the system is designed to satisfy include the following: 1) The circulation pump must have sufficient volume and pressure to operate the venturi tube and spray nozzles. 2) The venturi tube must be sized to empty the tank (except for the oil retained by the standpipe) and maintain a vacuum against the vacuum pump. 3) The tank must be strong enough to withstand atmospheric pressure against the vacuum inside and must have sufficient volume to enable exposure of a sufficiently large amount of sprayed oil to the vacuum. 4) The spray nozzles must be sized to atomize the oil and to ensure that the rate of flow of sprayed oil does not exceed the rate at which the venturi action can empty the tank. 5) The vacuum pump must produce a hard vacuum against the venturi tube and continue to work when it ingests some oil and water. 6) Fittings must be made vacuum tight (by use of O-rings) to prevent leakage of air into the system. The system is fully automatic, and can be allowed to remain in operation with very little monitoring. It is capable of reducing the air content of the oil from 11 to less than 1 volume percent in about 4 hours and to keep the water content below 100 parts per million.

Anderson, Christopher W.↗

NASA NTRS2005

Variable-Pressure Washer

The variable-pressure washer (VPW) is a proposed device that is so named because (1) it would play the role similar to that played by an ordinary washer, except that (2) the clamping pressure applied by it would vary with either circumferential or radial position. In a typical contemplated application, the radially varying clamping pressure would be used to obtain more nearly uniform compression on a pair of concentric seals (e.g., an O-ring or a gasket) in an assembly that experiences larger deformations normal to the sealing surface for locations around the outer diameter of the attachment flange when compared to locations around the inner diameter. The VPW (see figure) would include two interlocking channel rings pushed axially away from each other by compression spring-like components located at two or more radial positions. Each spring would have a different stiffness based on the radial location. Overlapping splits in each interlocking channel ring would allow for the non-uniform deformation in the rings. Each spring would be held in place by retaining cups attached to the inner flat surfaces of the channel rings. A plunger attached to one channel ring on the central axis would be captured in a plunger housing attached to the other channel ring: The capture of the plunger would hold the VPW together. When the VPW was clamped between two flat surfaces, the clamping force would be distributed unevenly across the face of the washer in the radial direction. The different stiffnesses of the springs would be chosen, in conjunction with other design parameters, to obtain a specified radial variation of clamping pressure in the presence of a specified clamping force.

Smeltzer, Stanley S., III↗