Apollo Seals: A Basis for the Crew Exploration Vehicle Seals

43rd AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 2007

Available electronically at http://gltrs.grc.nasa.gov Trade names and trademarks are used in this report for identification only. Their usage does not constitute an official endorsement, either expressed or implied, by the National Aeronautics and Space Administration. Level of Review: This material has been technically reviewed by technical management.

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 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 pres...

44th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 2008

A universal docking system is being developed by the National Aeronautics and Space Administration (NASA) to support future space exploration missions to low Earth orbit (LEO), to the moon, and to Mars. The candidate docking seals for the system are a composite design consisting of elastomer seal bulbs molded into the front and rear sides of a metal ring. The test specimens were sub-scale seals with two different elastomer cross-sections and a 12-in. outside diameter. The seal assemblies were mated in elastomer seal-on-metal plate and elastomer seal-onelastomer seal configurations. The seals were manufactured from S0383-70 silicone elastomer compound. Nominal and off-nominal joint configurations were examined. Both the compression load required to mate the seals and the leak rate observed were recorded while the assemblies were subjected to representative docking system operating temperatures of-58, 73, and 122 °F (-50, 23, and 50 °C). Both the loads required to fully compress the seals and their leak rates were directly proportional to the test temperature. Nomenclature AO atomic oxygen CVCM collected volatile condensable materials LEO low Earth orbit LIDS Low Impact Docking System MMOD micrometeoroid and orbital debris NASA National Aeronautics and Space Administration RTD resistance temperature detector TML total mass loss UV ultraviolet radiation REPORT DOCUMENTATION PAGE Form Approved OMB No. 0704-0188 The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188),

2009

The Crew Exploration Vehicle (CEV) will be exposed to the Micrometeoroid Orbital Debris (MMOD) environment in Low Earth Orbit (LEO) during missions to the International Space Station (ISS) and to the micrometeoroid environment during lunar missions. The CEV will be equipped with a docking system which enables it to connect to ISS and the lunar module known as Altair; this docking system includes a hatch that opens so crew and supplies can pass between the spacecrafts. This docking system is known as the Low Impact Docking System (LIDS) and uses a silicone rubber seal to seal in cabin air. The rubber seal on LIDS presses against a metal flange on ISS (or Altair). All of these mating surfaces are exposed to the space environment prior to docking. The effects of atomic oxygen, ultraviolet and ionizing radiation, and MMOD have been estimated using ground based facilities. This work presents an initial methodology to predict meteoroid and orbital debris threats to candidate docking seals being considered for LIDS. The methodology integrates the results of ground based hypervelocity impacts on silicone rubber seals and aluminum sheets, risk assessments of the MMOD environment for a variety of mission scenarios, and candidate failure criteria. The experimental effort that addressed the effects of projectile incidence angle, speed, mass, and density, relations between projectile size and resulting crater size, and relations between crater size and the leak rate of candidate seals has culminated in a definition of the seal/flange failure criteria. The risk assessment performed with the BUMPER code used the failure criteria to determine the probability of failure of the seal/flange system and compared the risk to the allotted risk dictated by NASA's program requirements.

1st AIAA Atmospheric and Space Environments Conference, 2009

The Crew Exploration Vehicle (CEV) will be exposed to the Micrometeoroid Orbital Debris (MMOD) environment in Low Earth Orbit (LEO) during missions to the International Space Station (ISS) and to the micrometeoroid environment during lunar missions. The CEV will be equipped with a docking system which enables it to connect to ISS and the lunar module known as Altair; this docking system includes a hatch that opens so crew and supplies can pass between the spacecrafts. This docking system is known as the Low Impact Docking System (LIDS) and uses a silicone rubber seal to seal in cabin air. The rubber seal on LIDS presses against a metal flange on ISS (or Altair). All of these mating surfaces are exposed to the space environment prior to docking. The effects of atomic oxygen, ultraviolet and ionizing radiation, and MMOD have been estimated using ground based facilities. This work presents an initial methodology to predict meteoroid and orbital debris threats to candidate docking seals being considered for LIDS. The methodology integrates the results of ground based hypervelocity impacts on silicone rubber seals and aluminum sheets, risk assessments of the MMOD environment for a variety of mission scenarios, and candidate failure criteria. The experimental effort that addressed the effects of projectile incidence angle, speed, mass, and density, relations between projectile size and resulting crater size, and relations between crater size and the leak rate of candidate seals has culminated in a definition of the seal/flange failure criteria. The risk assessment performed with the BUMPER code used the failure criteria to determine the probability of failure of the seal/flange system and compared the risk to the allotted risk dictated by NASA's program requirements.

Programme and Invitation to the workshop: Seals and Sealing, A Survey of Materials, Forms and Functions

Tribology Online, 2020

A lot of exploration missions have been planned for the moon, and lunar activity is likely to increase. The moon's surface is covered by a great deal of dust, called regolith, and these particles can seriously damage mechanical components. The design of any mechanism that will operate on the moon must take regolith into account. This includes the wheels and crawlers of lunar rovers, and many other mechanical components. This study considers measures for protecting small bearings in a lunar rover that operate close to the surface, in particular simple collar seals. These seals will require exceptional sealing ability, low torque, light weight, and easy installation. Collar seals made of three polymer composite materials (such as PTFE and PEEK) were evaluated. The seals have a convex portion that slides on the end face of the inner ring of a bearing or that of the outer ring; the sliding between the convex portion and the rings prevents regolith from entering the bearing. The seal performance and torque of each type of collar seal were tested using a regolith simulant in vacuum. The test conditions were decided based on the lunar environment and specification of a lunar rover under development. In order to maintain seal performance and to obtain lower torque, the thicknesses of the collar seals and their axial deflection were varied. Sliding on the end face of the inner ring of the bearing showed good seal performance and lower torque with optimum collar thickness and axial deflection for all composite materials. There was some variation in sealing and torque between the composites. The tribological performance and results of surface analysis by XPS are discussed.

Polymer Testing, 2017

This paper summarizes the small scale thermal exposure test results of the performance of metallic and polymeric O-ring seals typically used in radioactive material transportation packages. Five different Oring materials were evaluated: Inconel/silver, ethylene-propylene diene monomer (EPDM), polytetrafluoroethylene (PTFE), silicone, butyl, and Viton. The overall objective of this study is to provide test data and insights to the performance of these O-ring seals when exposed to beyond-design-basis temperature conditions due to a severe fire. Tests were conducted using a small-scale stainless steel pressure vessel pressurized with helium to 2 bar or 5 bar at room temperature. The vessel was then heated in an electric furnace to temperatures up to 900 C for a predetermined period (typically 8 he9 h). The pressure drop technique was used to determine if leakage occurred during thermal exposure. Out of a total of 46 tests performed, leakage (loss of vessel pressure) was detected in 13 tests.

1991

2008

Operations, for John Crane Inc., in Baton Rouge, Louisiana. He has held various engineering positions with Gulf Oil, Eastman Kodak, Exxon, and United Centrifugal Pump Company. Mr. Buck is routinely involved in the design, selection, application, and troubleshooting of mechanical seals. He was actively involved in the design and testing of the Type 48 low emission seal and upstream pumping seal. As a member of the API 682 Task Force, Mr. Buck helped to write the standard on mechanical seals for pumps. He is a member of ASME and STLE, and is a registered Professional Engineer in the State of Louisiana. He has several technical publications, including books and computer programs. Mr. Buck has a B.S. degree (Mechanical Engineering) from Mississippi State University (1970), and an M.S. degree (Mechanical Engineering) from Louisiana State University (1978).

2000

The ability for crewmembers to explore the surface of the Moon or Mars effectively on foot remains a significant test of any exploration design. The availability of a pressurized rover would substantially increase the range of exploration by space suited crewmembers. The design of the airlock systems or functions will facilitate crewmembers in accomplishing these efforts. The pressurized rover for planetary exploration incorporates three types of airlocks or pressure ports: the EVA airlock, the sample airlock and the habitat docking port. This paper conducts a survey of selected precedents in pressurized rover design and then analyzes the key issues for airlock design.

40th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, 2004

Control surface seals are crucial to current and future space vehicles, as they are used to seal the gaps surrounding body flaps, elevons, and other actuated exterior surfaces. During reentry, leakage of high temperature gases through these gaps could damage underlying lower temperature structures such as rudder drive motors and mechanical actuators, resulting in impaired vehicle control. To be effective, control surface seals must shield lower temperature structures from heat transfer by maintaining sufficient resiliency to remain in contact with opposing sealing surfaces through multiple compression cycles. The current seal exhibits significant loss of resiliency after a few compression cycles at elevated temperatures (i.e., 1900 °F) and therefore would be inadequate for advanced space vehicles. This seal utilizes a knitted Inconel X-750 spring tube as its primary resilient element. As part of a larger effort to enhance seal resiliency, researchers at the NASA Glenn Research Center performed high temperature compression testing (up to 2000 °F) on candidate spring tube designs employing material substitutions and modified geometries. These tests demonstrated significant improvements in spring tube resiliency (5.5x better at 1750 °F) through direct substitution of heat treated Rene 41 alloy in the baseline knit design. The impact of geometry modification was minor within the range of parameters tested, however trends did suggest that moderate resiliency improvements could be obtained by optimizing the current spring tube geometry.

Volume 3: Heat Transfer, Parts A and B, 2006

Advanced seals have been identified as critical in meeting engine goals for specific fuel consumption, thrust-to-weight ratio, emissions, durability, and operating costs. In a direct effort to reduce the parasitic leakage, a high-temperature, high-speed seal test rig with Active Clearance Control (ACC) has been designed, built and validated by the National Aerospace Laboratory (NLR) in the Netherlands within a collaborative program with Sulzer Metco Turbine Components (SMTC) and Pratt & Whitney (P&W). NLR’s new seal test rig is capable to evaluate seals for the next generation gas turbine engines. It will test air seals (i.e., labyrinth, brush, and new seal concepts) in near gas turbine engine environment conditions of high temperature to 815 °C (1500 °F), high pressure to 2400 kPa (335 psid), high surface speeds to 365 m/s (1200 ft/s). Seal flows for typical engine seal clearances between 0.12 mm (0.005 inch) and 0.65 mm (0.025 inch) can be measured without changing test articles b...

2000

Management jointly sponsored a program to evaluate elastomeric O-ring seal materials for radioactive material shipping containers. Thk report presents the results of low-and high-. temperature tests conducted on 27 common elastomeric compounds. ACKNOWLEDGMENTS I thank the many Sandia National Laboratories Transportation Systems and Development Department members who have contributed to this work, including

AIAA SPACE 2007 Conference & Exposition, 2007

Since its founding, NASA has been dedicated to the advancement of aeronautics and space science. The NASA Scientific and Technical Information (STI) program plays a key part in helping NASA maintain this important role. The NASA STI Program operates under the auspices of the Agency Chief Information Officer. It collects, organizes, provides for archiving, and disseminates NASA's STI. The NASA STI program provides access to the NASA Aeronautics and Space Database and its public interface, the NASA Technical Reports Server, thus providing one of the largest collections of aeronautical and space science STI in the world. Results are published in both non-NASA channels and by NASA in the NASA STI Report Series, which includes the following report types: