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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 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

Twist seal for high-pressure vessels such as space shuttle rocket motors

Seals for sealing clevis and flange joints (14) of a solid rocket booster motor, and more particularly to a seal (30) which is twisted upon application of expansion forces to an edge seal (36). This twisting motion initially causes a leading edge seal (44) to be urged into sealing engagement with a surface (48) of an adjacent member (20) and thereafter, increasing fluid pressure on a pressurized side (64) of a seal (30) drives a broad sealing region (46) into sealing engagement with a surface (48).

von Pragenau, George L.↗
NASA NTRS2008

Review of Full-Scale Docking Seal Testing Capabilities

NASA is developing a new docking system to support future space exploration missions to low-Earth orbit, the Moon, and Mars. This mechanism, called the Low Impact Docking System (LIDS), is designed to connect pressurized space vehicles and structures including the Crew Exploration Vehicle, International Space Station, and lunar lander. NASA Glenn Research Center (GRC) is playing a key role in developing the main interface seal for this new docking system. These seals will be approximately 147 cm (58 in.) in diameter. To evaluate the performance of the seals under simulated operating conditions, NASA GRC is developing two new test rigs: a non-actuated version that will be used to measure seal leak rates and an actuated test rig that will be able to measure both seal leak rates and loads. Both test rigs will be able to evaluate the seals under seal-on-seal or seal-on-plate configurations at temperatures from -50 to 50 C (-58 to 122 F) under operational and pre-flight checkout pressure gradients in both aligned and misaligned conditions.

Dunlap, Patrick H., Jr.↗
NASA NTRS2008

Multiple internal seal ring micro-electro-mechanical system vacuum packaging method

A Multiple Internal Seal Ring (MISR) Micro-Electro-Mechanical System (MEMS) vacuum packaging method that hermetically seals MEMS devices using MISR. The method bonds a capping plate having metal seal rings to a base plate having metal seal rings by wafer bonding the capping plate wafer to the base plate wafer. Bulk electrodes may be used to provide conductive paths between the seal rings on the base plate and the capping plate. All seals are made using only metal-to-metal seal rings deposited on the polished surfaces of the base plate and capping plate wafers. However, multiple electrical feed-through metal traces are provided by fabricating via holes through the capping plate for electrical connection from the outside of the package through the via-holes to the inside of the package. Each metal seal ring serves the dual purposes of hermetic sealing and providing the electrical feed-through metal trace.

Hayworth, Ken J.↗
NASA NTRS2009

Foil Face Seal Testing

In the seal literature you can find many attempts by various researchers to adapt film riding seals to the gas turbine engine. None have been successful, potential distortion of the sealing faces is the primary reason. There is a film riding device that does accommodate distortion and is in service in aircraft applications, namely the foil bearing. More specifically a foil thrust bearing. These are not intended to be seals, and they do not accommodate large axial movement between shaft & static structure. By combining the 2 a unique type of face seal has been created. It functions like a normal face seal. The foil thrust bearing replaces the normal primary sealing surface. The compliance of the foil bearing allows the foils to track distortion of the mating seal ring. The foil seal has several perceived advantages over existing hydrodynamic designs, enumerated in the chart. Materials and design methodology needed for this application already exist. Also the load capacity requirements for the foil bearing are low since it only needs to support itself and overcome friction forces at the antirotation keys.

Munson, John↗
NASA NTRS2010

Reducing Seal Adhesion in Low Impact Docking Systems

Silicone elastomers, used in seals for airlocks or other sealing surfaces in space, are sticky in their as-received condition. Because of the sticking, a greater force may be needed to separate the mating surfaces. If the adhesion is sufficiently high, a sudden unpredicted movement of the spacecraft during undocking, vibration, or uneven release could pull off the seal, resulting in a damage that would have to be repaired before another docking. The damaged seal can result in significant gas leakage and possibly in a catastrophic mishap impacting the safety of the crew. It is also possible that a compromised seal could result in a delayed but sudden gas leak that could put the crew at unexpected risk. This is especially of concern for androgynous seals, which have identical mating surfaces on both sides for interchangeability and redundancy. Such seals typically have elastomer-on-elastomer sealing surfaces. To reduce sticking, one could use release agents such as powders and lubricants, but these can be easily removed and transferred to other surfaces, causing uneven sealing and contamination. Modification of the elastomer surface to make a more slippery and less sticky surface that is integral with the bulk elastomer would be more desirable.

Banks, Bruce A.↗
NASA NTRS2010

Full-Scale System for Quantifying Loads and Leak Rates of Seals for Space Applications

NASA is developing advanced space-rated vacuum seals in support of future space exploration missions to low-Earth orbit and other destinations. These seals may be 50 to 60 in. (127 to 152 cm) in diameter and must exhibit extremely low leak rates to ensure that astronauts have sufficient breathable air for extended missions to the International Space Station or the Moon. Seal compression loads must be below prescribed limits so as not to overload the mechanisms that compress them during docking or mating, and seal adhesion forces must be low to allow two mated systems to separate when required. NASA Glenn Research Center has developed a new test apparatus to measure leak rates and compression and adhesion loads of candidate full-scale seals under simulated thermal, vacuum, and engagement conditions. Tests can be performed in seal-on-seal or seal-on-flange configurations at temperatures from -76 to 140 F (-60 to 60 C) under operational pressure gradients. Nominal and off-nominal mating conditions (e.g., incomplete seal compression) can also be simulated. This paper describes the main design features of the test apparatus as well as techniques used to overcome some of the design challenges.

Dunlap, Patrick H., Jr.↗
NASA NTRS2011

An Experimental Investigation of Leak Rate Performance of a Subscale Candidate Elastomer Docking Space Seal

A novel docking seal was developed for the main interface seal of NASA s Low Impact Docking System (LIDS). This interface seal was designed to maintain acceptable leak rates while being exposed to the harsh environmental conditions of outer space. In this experimental evaluation, a candidate docking seal assembly called Engineering Development Unit (EDU58) was characterized and evaluated against the Constellation Project leak rate requirement. The EDU58 candidate seal assembly was manufactured from silicone elastomer S0383-70 vacuum molded in a metal retainer ring. Four seal designs were considered with unique characteristic heights. The leak rate performance was characterized through a mass point leak rate method by monitoring gas properties within an internal control volume. The leakage performance of the seals were described herein at representative docking temperatures of -50, +23, and +50 C for all four seal designs. Leak performance was also characterized at 100, 74, and 48 percent of full closure. For all conditions considered, the candidate seal assemblies met the Constellation Project leak rate requirement.

Garafolo, Nicholas G.↗
NASA NTRS2013

Use of VUV Radiation to Control Elastomer Seal Adhesion

Due to their wide operating temperatures and low leakage rates, silicone elastomers are the only class of flight qualified elastomer materials that currently meet NASA's needs for various seal applications, which include docking and hatch seals for future space exploration vehicles. However, silicone elastomers are naturally sticky and exhibit sizeable adhesion when mated against metals and other silicone surfaces. This undesirable adhesion can make undocking spacecraft or opening a hatch problematic. Two approaches that can be used to reduce seal adhesion include use of grease or, application of low doses of atomic oxygen (AO). This paper investigates a third approach: the application of light doses of vacuum ultraviolet (VUV) radiation. Presented are the adhesion and leakage characteristics of S0383-70 silicone elastomer exposed to various VUV doses in the 115 to 200 nm wavelength range. The data indicate that adhesion is expected to be less than the target threshold maximum of 2 lb/in(exp2) after about 1 J/cm(exp2) of VUV exposure for seal-to-metal configurations and after 2 J/cm(exp2) for seal-to-seal configurations with no significant damage, or increase in seal leakage. This paper shows that VUV, without AO or grease, can be an effective means to reduce adhesion to the desired levels necessary for space seals with minimal change in seal leak rates.

deGroh, Henry C., III↗
NASA NTRS2014

An Overview of High Temperature Seal Development and Testing Capabilities at the NASA Glenn Research Center

The NASA Glenn Research Center (GRC), partnering with the University of Toledo, has a long history of developing and testing seal technologies for high-temperature applications. The GRC Seals Team has conducted research and development on high-temperature seal technologies for applications including advanced propulsion systems, thermal protection systems (airframe and control surface thermal seals), high-temperature preloading technologies, and other extreme-environment seal applications. The team has supported several high-profile projects over the past 30 years and has partnered with numerous organizations, including other government entities, academic institutions, and private organizations. Some of these projects have included the National Aerospace Space Plane (NASP), Space Shuttle Space Transport System (STS), the Multi-Purpose Crew Vehicle (MPCV), and the Dream Chaser Space Transportation System, as well as several high-speed vehicle programs for other government organizations. As part of the support for these programs, NASA GRC has developed unique seal-specific test facilities that permit evaluations and screening exercises in relevant environments. The team has also embarked on developing high-temperature preloaders to help maintain seal functionality in extreme environments. This paper highlights several propulsion-related projects that the NASA GRC Seals Team has supported over the past several years and will provide an overview of existing testing capabilities

National Aerospace Plane↗
NASA NTRS2014

Effects of Low Earth Orbit on Docking Seal Materials

Spacecraft docking seals are typically made of silicone elastomers. When such seals are exposed to low Earth orbit (LEO) conditions, they can suffer damage from ultraviolet (UV) radiation and atomic oxygen (AO, or monoatomic oxygen, the predominant oxygen species in LEO). An experiment flew on the International Space Station (ISS) to measure the effects of LEO on seal materials S0383-70 and ELA-SA-401 and various mating counterface materials which included anodized aluminum. Samples flown in different orientations received different amounts of UV and AO. The hypotheses were that most of the damage would be from UV, and 10 days or more of exposure in LEO would badly damage the seals. Eighteen seals were exposed for 543 days in ram (windward), zenith (away from Earth), or wake (leeward) orientations, and 15 control samples (not flown) provided undamaged baseline leakage. To determine post-flight leak rates, each of the 33 seals were placed in an O-ring groove of a leak test fixture and pressure tested over time. Resistance temperature detectors (RTDs), pressure transducers, and LabVIEW (National Instruments) programs were used to measure and analyze the temperature and pressure and calculate leakage. Average leakage of control samples was 2.6 x 10(exp -7) lbs/day. LEO exposure did not considerably damage ELA-SA-401. The S0383-70 flight samples leaked at least 10 times more than ELA-SA-401 in all cases except one, demonstrating that ELA-SA-401 may be a more suitable sealing material in LEO. AO caused greater damage than UV; samples in ram orientation (receiving an AO fluence of 4.3 x 10(exp 21) atoms/(sq cm) and in wake (2.9x 10(exp 20) atoms/(sq cm)) leaked more than those in zenith orientation (1.58 x 10(exp 20) atoms/(sq cm)), whereas variations in UV exposure did not seem to affect the samples. Exposure to LEO did less damage to the seals than hypothesized, and the data did not support the conjecture that UV causes more damage than AO.

Leakage↗
DOE OSTI2024

Puck Loop Seal (Final Project Technical Report)

Sandia National Laboratories (SNL) is advancing technical capabilities used in passive loop seals. The “Puck” seal used a set of International Atomic Energy Agency (IAEA) requirements for new passive loop seals published in 2020 as a design guide. The seal is based on an oxygen-sensitive inner mixture encased in an oxygen-impermeable shell, is monolithic rather than two-part, incorporates self-capturing wire features, contains colored water beads and bubbles formed during processing as unique identifiers (UIDs), and visually indicates tamper (whether from seal body penetration or from seal wire removal) by irreversibly changing the seal body from multi-colored to black. This paper will provide details on the design, development, and testing of Puck seal prototypes.

42 ENGINEERING↗
NASA NTRS1972

New circumferential seal design concept using self-acting lift geometries

Seal operating temperatures, leakage (pressurizing gas flow), torque, and wear of a conventional circumferential shaft seal were measured and compared to those of a conventional seal modified to have self-acting lift geometries. Both seal types had a 2.625-in diameter bore and were operated at a sliding velocity of 150 ft/sec with differential pressures ranging from 0 to 100 psi. Results of this investigation show that the self-acting seal operated at lower bulk carbon temperatures with half the torque and approximately one-tenth the wear of the conventional seal. Seal leakage of the self-acting seal was of order of 0.04 scfm for pressures above 60 psi which is well within the accepted range for gas turbine engine applications.

Hady, W. F.↗
NASA NTRS1973

Design, develop and test high temperature dynamic seals for the space shuttle's aerodynamic control surfaces

A description is given of the design, development and testing of high temperature dynamic seals for the gaps between the structure and aerodynamic control surfaces on the space shuttle. These aerodynamic seals are required to prevent high temperature airflow from damaging thermally unprotected structures and components during entry. Two seal concepts evolved a curtain seal for the spanwise elevon cove gap, and a labyrinth seal for the area above the elevon, at the gap between the end of the elevon and the fuselage. On the basis of development testing, both seal concepts were shown to be feasible for controlling internal temperatures to 350 F or less when exposed to a typical space shuttle entry environment. The curtain seal concept demonstrated excellent test results and merits strong consideration for application on the space shuttle orbiter. The labyrinth seal concept, although demonstrating significant temperature reduction characteristics, may or may not be required on the Orbiter, depending on the actual design configuration and flight environment.

Source record↗
NASA NTRS1974

Mainshaft seals for small gas turbine engines

An experimental evaluation of mainshaft seals for small gas turbine engines was conducted with shaft speeds to 213 m/s (700 ft/sec), air pressures to 148 Newtons per square centimeter abs. (215 psia), and air temperatures to 412k(282 F). A radial face seal incorporating self-acting geometry for lift augmentation was evaluated. In addition, three conventional carbon seal types (face, circumferential segmented, and rotating ring) were run for comparison. Test results indicated that the conventional seals used in this evaluation may not be satisfactory in future advanced engines because of excessive air leakage. On the other hand, the self-acting face seal was shown to have the potential capability of limiting leakages to one-half that of the conventional face seals and one-fifth that of conventional ring seals. A 150-hour endurance test of the self-acting face seal was conducted.

Ludwig, L. P.↗
NASA NTRS1976

Fundamentals of fluid sealing

The fundamentals of fluid sealing, including seal operating regimes, are discussed and the general fluid-flow equations for fluid sealing are developed. Seal performance parameters such as leakage and power loss are presented. Included in the discussion are the effects of geometry, surface deformations, rotation, and both laminar and turbulent flows. The concept of pressure balancing is presented, as are differences between liquid and gas sealing. Mechanisms of seal surface separation, fundamental friction and wear concepts applicable to seals, seal materials, and pressure-velocity (PV) criteria are discussed.

Zuk, J.↗
NASA NTRS1976

The development of large diameter, high pressure, cryogenic radial static seals

Two configurations of radial static seals are developed for high-pressure 773 kg per sq cm cryogenic applications: a U-shaped fluorocarbon seal and a delta-shaped PTFE seal. The U-seal is a common commercial design consisting of a spring-loaded cup-shaped jacket; the basic principle is that the soft plastic jacket provides the interface between the piston and the bore, the jacket being held in place by a metal spring. The delta seal is based on the principle that the soft plastic delta cross section furnishes the interface at the metal face and circumferential face of the gland and cylinder. Test results indicate that both the plastic U-seal and the delta seal designs are sufficiently flexible to accommodate assembly in bore or piston grooves. Of these two configurations, the delta seal is found to be superior as it meets all the design requirements for proof pressure testing the turbopump components of the main engine in the Space Shuttle.

Burr, M. E.↗
NASA NTRS1977

Design considerations in mechanical face seals for improved performance. 2: Lubrication

The importance of sealing technology in our industrial, chemical-oriented society in regard to maintenance and environmental contamination is pointed out. It is stated that seal performance (leakage, life) is directly related to seal lubrication. Current thinking in regard to seal lubrication is reviewed; the effect of energy dissipation in the thin lubricating film separating the sealing faces is pointed out, and the results of vaporization due to heating are illustrated. Also, hydrodynamic lubrication is reviewed, and an inherent tendency for the seal to operate with angular misalignment is shown. Recent work on hydrostatic effects is summarized and the conditions for seal instability are discussed. Four different modes of seal lubrication are postulated with the mode type being a strong function of speed and pressure.

Ludwig, L. P.↗
NASA NTRS1977

Space Shuttle Solid Rocket booster nozzle flexible seal pivot point dynamics

The NASA Space Shuttle Solid Rocket Motor (SRM) uses an omniaxial flexible seal for vectoring the nozzle. This flexible seal, being built under the technical management of Marshall Space Flight Center in Huntsville, Alabama, is the first ever to be used on a manned spacecraft booster. Since no test history on the particular type of flexible seal being used was available and since flexible seal dynamics characteristics affect many vehicle hardware design and manufacture requirements, a rigorous test program to assess the integrity and operating characteristics of the seal was developed and executed. Vector requirements of the SRM flexible seal and results of subscale and full-scale prototype seal verification tests are included. The advantages of an improved method of calculating actuator stroke versus vector angle and pressure over the more classical method of calculating actuator strokes using pivot point envelopes are discussed. Results presented show that the SRM seal design will satisfy flight requirements.

Gaffin, R. D.↗