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At least 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
NASA NTRS2003

Viscoelastic Vibration Dampers for Turbomachine Blades

Simple viscoelastic dampers have been invented for use on the root attachments of turbomachine blades. These dampers suppress bending- and torsion-mode blade vibrations, which are excited by unsteady aerodynamic forces during operation. In suppressing vibrations, these dampers reduce fatigue (thereby prolonging blade lifetimes) while reducing noise. These dampers can be installed in new turbomachines or in previously constructed turbomachines, without need for structural modifications. Moreover, because these dampers are not exposed to flows, they do not affect the aerodynamic performances of turbomachines. Figure 1 depicts a basic turbomachine rotor, which includes multiple blades affixed to a hub by means of dovetail root attachments. Prior to mounting of the blades, thin layers of a viscoelastic material are applied to selected areas of the blade roots. Once the blades have been installed in the hub and the rotor is set into rotation, centrifugal force compresses these layers between the mating load-bearing surfaces of the hub and the blade root. The layers of viscoelastic material provide load paths through which the vibration energy of the blade can be dissipated. The viscoelasticity of the material converts mechanical vibration energy into shear strain energy and then from shear strain energy to heat. Of the viscoelastic materials that have been considered thus far for this application, the one of choice is a commercial polyurethane that is available in tape form, coated on one side with an adhesive that facilitates bonding to blade roots. The thickness of the tape can be chosen to suit the specific application. The typical thickness of 0.012 in. (.0.3 mm) is small enough that the tape can fit in the clearance between the mating blade-root and hub surfaces in a typical turbomachine. In an experiment, a blade was mounted in a test fixture designed to simulate the blade-end conditions that prevail in a turbocompressor. Vibrations were excited in the blade by use of an impact hammer, and damping of the vibrations was measured by use of a dynamic signal analyzer. Tests were performed without and with viscoelastic dampers installed in the dovetail root attachment. The results of the measurements, some of which are presented in Figure 2, show that the viscoelastic dampers greatly increased the rate of damping of vibrations. Accordingly, dynamic stresses on rotor blades were significantly reduced, as shown in Figure 2.

Nguyen, Nhan↗
NASA NTRS2003

Stable, Thermally Conductive Fillers for Bolted Joints

A commercial structural epoxy [Super Koropon (or equivalent)] has been found to be a suitable filler material for bolted joints that are required to have large thermal conductances. The contact area of such a joint can be less than 1 percent of the apparent joint area, the exact value depending on the roughnesses of the mating surfaces. By occupying the valleys between contact peaks, the filler widens the effective cross section for thermal conduction. In comparison with prior thermal joint-filler materials, the present epoxy offers advantages of stability, ease of application, and -- as a byproduct of its stability -- lasting protection against corrosion. Moreover, unlike silicone greases that have been used previously, this epoxy does not migrate to contaminate adjacent surfaces. Because this epoxy in its uncured state wets metal joint surfaces and has low viscosity, it readily flows to fill the gaps between the mating surfaces: these characteristics affect the overall thermal conductance of the joint more than does the bulk thermal conductivity of the epoxy, which is not exceptional. The thermal conductances of metal-to-metal joints containing this epoxy were found to range between 5 and 8 times those of unfilled joints.

LeVesque, Raymond J., II↗
NASA NTRS2011

Self-Rupturing Hermetic Valve

For commercial, military, and aerospace applications, low-cost, small, reliable, and lightweight gas and liquid hermetically sealed valves with post initiation on/off capability are highly desirable for pressurized systems. Applications include remote fire suppression, single-use system-pressurization systems, spacecraft propellant systems, and in situ instruments. Current pyrotechnic- activated rupture disk hermetic valves were designed for physically larger systems and are heavy and integrate poorly with portable equipment, aircraft, and small spacecraft and instrument systems. Additionally, current pyrotechnically activated systems impart high g-force shock loads to surrounding components and structures, which increase the risk of damage and can require additional mitigation. The disclosed mechanism addresses the need for producing a hermetically sealed micro-isolation valve for low and high pressure for commercial, aerospace, and spacecraft applications. High-precision electrical discharge machining (EDM) parts allow for the machining of mated parts with gaps less than a thousandth of an inch. These high-precision parts are used to support against pressure and extrusion, a thin hermetically welded diaphragm. This diaphragm ruptures from a pressure differential when the support is removed and/or when the plunger is forced against the diaphragm. With the addition of conventional seals to the plunger and a two-way actuator, a derivative of this design would allow nonhermetic use as an on/off or metering valve after the initial rupturing of the hermetic sealing disk. In addition, in a single-use hermetically sealed isolation valve, the valve can be activated without the use of potential leak-inducing valve body penetrations. One implementation of this technology is a high-pressure, high-flow-rate rupture valve that is self-rupturing, which is advantageous for high-pressure applications such as gas isolation valves. Once initiated, this technology is self-energizing and requires low force compared to current pyrotechnic-based burst disk hermetic valves. This is a novel design for producing a single-use, self-rupturing, hermetically sealed valve for isolation of pressurized gas and/or liquids. This design can also be applied for single-use disposable valves for chemical instruments. A welded foil diaphragm is fully supported by two mated surfaces that are machined to micron accuracies using EDM. To open the valve, one of the surfaces is moved relative to the other to (a) remove the support creating an unsupported diaphragm that ruptures due to over pressure, and/or (b) produce tension in the diaphragm and rupture it.

Tucker, Curtis E., Jr.↗
NASA NTRS2012

Dual-Compartment Inflatable Suitlock

A paper discusses a dual-compartment inflatable suitlock (DCIS) for Extra - vehicular Activity (EVA) that will allow for dust control, suit maintenance, and efficient EVA egress/ingress. The expandable (inflatable technologies) aspect of the design will allow the unit to stow in a compact package for transport. The DCIS consists of three hard, in line bulkheads, separating two cylindrical membrane-walled compartments. The inner bulkhead can be fitted with a variety of hatch types, docking flanges, and mating hardware, such as the common berthing mechanism (CBM), for the purpose of mating with vehicles, habitats, and other pressurized modules. The inner bulkhead and center bulkhead function as the end walls of the inner compartment, which, during operations, would stay pressurized, either matching the pressure of the habitat or acting as a lower-pressure transitional volume. The suited crewmember can quickly don a suit, and egress the suitlock without waiting for the compartment to depressurize. The outer compartment can be pressurized infrequently, when a long dwell time is expected prior to the next EVA, or during off-nominal suit maintenance tasks, allowing shirtsleeve inspections and maintenance of the space suits. The outer bulkhead has a pressure-assisted hatch door that stays open and stowed routinely, but can be closed for suit maintenance and pressurization as needed.

Howe, Scott↗
NASA NTRS2013

Extraction and Separation Modeling of Orion Test Vehicles with ADAMS Simulation

The Capsule Parachute Assembly System (CPAS) project has increased efforts to demonstrate the performance of fully integrated parachute systems at both higher dynamic pressures and in the presence of wake fields using a Parachute Compartment Drop Test Vehicle (PCDTV) and a Parachute Test Vehicle (PTV), respectively. Modeling the extraction and separation events has proven challenging and an understanding of the physics is required to reduce the risk of separation malfunctions. The need for extraction and separation modeling is critical to a successful CPAS test campaign. Current PTV-alone simulations, such as Decelerator System Simulation (DSS), require accurate initial conditions (ICs) drawn from a separation model. Automatic Dynamic Analysis of Mechanical Systems (ADAMS), a Commercial off the Shelf (COTS) tool, was employed to provide insight into the multi-body six degree of freedom (DOF) interaction between parachute test hardware and external and internal forces. Components of the model include a composite extraction parachute, primary vehicle (PTV or PCDTV), platform cradle, a release mechanism, aircraft ramp, and a programmer parachute with attach points. Independent aerodynamic forces were applied to the mated test vehicle/platform cradle and the separated test vehicle and platform cradle. The aero coefficients were determined from real time lookup tables which were functions of both angle of attack ( ) and sideslip ( ). The atmospheric properties were also determined from a real time lookup table characteristic of the Yuma Proving Grounds (YPG) atmosphere relative to the planned test month. Representative geometries were constructed in ADAMS with measured mass properties generated for each independent vehicle. Derived smart separation parameters were included in ADAMS as sensors with defined pitch and pitch rate criteria used to refine inputs to analogous avionics systems for optimal separation conditions. Key design variables were dispersed in a Monte Carlo analysis to provide the maximum expected range of the state variables at programmer deployment to be used as ICs in DSS. Extensive comparisons were made with Decelerator System Simulation Application (DSSA) to validate the mated portion of the ADAMS extraction trajectory. Results of the comparisons improved the fidelity of ADAMS with a ramp pitch profile update from DSSA. Post-test reconstructions resulted in improvements to extraction parachute drag area knock-down factors, extraction line modeling, and the inclusion of ball-to-socket attachments used as a release mechanism on the PTV. Modeling of two Extraction parachutes was based on United States Air Force (USAF) tow test data and integrated into ADAMS for nominal and Monte Carlo trajectory assessments. Video overlay of ADAMS animations and actual C-12 chase plane test videos supported analysis and observation efforts of extraction and separation events. The COTS ADAMS simulation has been integrated with NASA based simulations to provide complete end to end trajectories with a focus on the extraction, separation, and programmer deployment sequence. The flexibility of modifying ADAMS inputs has proven useful for sensitivity studies and extraction/separation modeling efforts. 1

Fraire, Usbaldo, Jr.↗
NASA NTRS2013

Dual-Compartment Inflatable Suitlock

There is a need for an improvement over current NASA Extravehicular Activity (EVA) technology. The technology must allow the capacity for quicker, more efficient egress/ingress, allow for shirtsleeve suit maintenance, be compact in transport, and be applicable to environments ranging from planetary surface (partial-g) to orbital or deep space zero-g environments. The technology must also be resistant to dust and other foreign contaminants that may be present on or around a planetary surface. The technology should be portable, and be capable of docking with a variety of habitats, ports, stations, vehicles, and other pressurized modules. The Dual-Compartment Inflatable Suitlock (DCIS) consists of three hard inline bulkheads, separating two cylindrical membrane-walled compartments. The Inner Bulkhead can be fitted with a variety of hatch types, docking flanges, and mating hardware, such as the Common Berthing Mechanism (CBM), for the purpose of mating with vehicles, habitats, and other pressurized modules. The Inner Bulkhead and Center Bulkhead function as the end walls of the Inner Compartment, which during operations, would stay pressurized, either matching the pressure of the habitat or acting as a lower-pressure transitional volume. The Inner Compartment contains donning/doffing fixtures and inner suit-port hatches. The Center Bulkhead has two integrated suit-ports along with a maintenance hatch. The Center Bulkhead and Outer Bulkhead function as the end walls of the Outer Compartment, which stays at vacuum during normal operations. This allows the crewmember to quickly don a suit, and egress the suitlock without waiting for the Outer Compartment to depressurize. The Outer Compartment can be pressurized infrequently for both nominal and off-nominal suit maintenance tasks, allowing shirtsleeve inspections and maintenance/repair of the environmental suits. The Outer Bulkhead has a pressure-assisted hatch door that stays open and stowed during EVA operations, but can be closed for environmental protection of the suits, suit maintenance, and pressurization.

Kennedy, Kriss J.↗
NASA NTRS2014

Integrated Attitude Control Strategy for the Asteroid Redirect Mission

A deep-space mission has been proposed to redirect an asteroid to a distant retrograde orbit around the moon using a robotic vehicle, the Asteroid Redirect Vehicle (ARV). In this orbit, astronauts will rendezvous with the ARV using the Orion spacecraft. The integrated attitude control concept that Orion will use for approach and docking and for mated operations will be described. Details of the ARV's attitude control system and its associated constraints for redirecting the asteroid to the distant retrograde orbit around the moon will be provided. Once Orion is docked to the ARV, an overall description of the mated stack attitude during all phases of the mission will be presented using a coordinate system that was developed for this mission. Next, the thermal and power constraints of both the ARV and Orion will be discussed as well as how they are used to define the optimal integrated stack attitude. Lastly, the lighting and communications constraints necessary for the crew's extravehicular activity planned to retrieve samples from the asteroid will be examined. Similarly, the joint attitude control strategy that employs both the Orion and the ARV attitude control assets prior, during, and after each extravehicular activity will also be thoroughly discussed.

Lopez, Pedro, Jr.↗
NASA NTRS2016

Silicon Alignment Pins: An Easy Way to Realize a Wafer-To-Wafer Alignment

A silicon alignment pin is used to align successive layers of components made in semiconductor chips and/or metallic components to make easier the assembly of devices having a layered structure. The pin is made as a compressible structure which can be squeezed to reduce its outer diameter, have one end fit into a corresponding alignment pocket or cavity defined in a layer of material to be assembled into a layered structure, and then allowed to expand to produce an interference fit with the cavity. The other end can then be inserted into a corresponding cavity defined in a surface of a second layer of material that mates with the first layer. The two layers are in registry when the pin is mated to both. Multiple layers can be assembled to create a multilayer structure. Examples of such devices are presented.

Jung-Kubiak, Cecile↗
NASA NTRS2016

Tribological Studies of Dynamic Thermal Seal Materials

Thermal seals are required on high-speed vehicles in many dynamic applications such as variable inlets in propulsion systems and control surfaces. These seals, often referred to as dynamic thermal seals, must not only mitigate inboard heat transfer, but must also exhibit sufficient durability when scrubbed against mating surfaces. For high-temperature high-speed vehicle applications, the mating surfaces are often made from thermal protection system (TPS) materials, which are typically rougher and more abrasive than TPS materials used at lower temperatures. The high-temperature TPS materials used can include non-ablative (e.g., lightweight porous oxides, ceramic matrix composites) andor ablative systems (e.g., phenolic systems). Due to the increased need for durable high-temperature dynamic seals, researchers working with the NASA Glenn Research Center embarked on an effort to (a) characterize the tribological performance of state-of-the-art thermal seal materials against a variety of TPS materials and (b) develop approaches for improved wear resistance. Tests were conducted using a recently upgraded high-temperature tribometer to assess wear resistance for a variety of tribopairs under multiple conditions. This data will begin to frame the challenges of using these materials and eventually permit an improved ability to design and implement these critical TPS components.

thermal protection↗
NASA NTRS2018

Wafer-To-Wafer Alignment Method

A silicon alignment pin is used to align successive layer of component made in semiconductor chips and/or metallic components to make easier the assembly of devices having a layered structure. The pin is made as a compressible structure which can be squeezed to reduce its outer diameter, have one end fit into a corresponding alignment pocket or cavity defined in a layer of material to be assembled into a layered structure, and then allowed to expand to produce an interference fit with the cavity. The other end can then be inserted into a corresponding cavity defined in a surface of a second layer of material that mates with the first layer. The two layers are in registry when the pin is mated to both. Multiple layers can be assembled to create a multilayer structure. Examples of such devices are presented.

Jung-Kubiak, Cecile↗
NASA NTRS2018

Evaluations of Candidate Materials for Advanced Space-Rated Vacuum Seals to Explore Space Environment Exposure Limits

For many materials used in space hardware, the environment in which they need to operate is harsher than the environment on earth. Exposure to vacuum conditions, atomic oxygen, and ultraviolet radiation can be detrimental, so testing of space hardware in simulated space environments is required. This is especially true for elastomeric components such as seals. NASA is developing advanced space-rated vacuum seals in support of future space exploration missions. These seals must exhibit extremely low leak rates to ensure that astronauts have sufficient breathable air during extended-duration missions. In some applications the seals are not mated during portions of the mission and are left uncovered and exposed to the conditions in space for prolonged periods of time prior to mating. Space-rated vacuum seals are often made of silicone because of the material's wide operating temperature range and ability to be molded or extruded into various shapes and cross sections. One approach being considered to achieve improved performance is to add titanium dioxide to the silicone material to make it more resistant to damage from ultraviolet radiation. In this study, seals made of the baseline material with and without 1.5 percent titanium dioxide additive (by weight) were exposed to atomic oxygen and increasing levels of ultraviolet radiation and then leak tested. Test results revealed that seals made of the new material could withstand longer exposures while still satisfying the leak rate requirement even under worst-case conditions of partial compression at the extremes of the anticipated operating temperature range.

Seals↗
NASA NTRS2018

Evaluations of Candidate Materials for Advanced Space-Rated Vacuum Seals to Explore Space Environment Exposure Limits

For many materials used in space hardware, the environment in which they need to operate is harsher than the environment on earth. Exposure to vacuum conditions, atomic oxygen, and ultraviolet radiation can be detrimental, so testing of space hardware in simulated space environments is required. This is especially true for elastomeric components such as seals. NASA is developing advanced space-rated vacuum seals in support of future space exploration missions. These seals must exhibit extremely low leak rates to ensure that astronauts have sufficient breathable air during extended-duration missions. In some applications the seals are not mated during portions of the mission and are left uncovered and exposed to the conditions in space for prolonged periods of time prior to mating. Space-rated vacuum seals are often made of silicone because of the material's wide operating temperature range and ability to be molded or extruded into various shapes and cross sections. One approach being considered to achieve improved performance is to add titanium dioxide to the silicone material to make it more resistant to damage from ultraviolet radiation. In this study, seals made of the baseline material with and without 1.5% titanium dioxide additive (by weight) were exposed to atomic oxygen and increasing levels of ultraviolet radiation and then leak tested. Test results revealed that seals made of the new material could withstand longer exposures while still satisfying the leak rate requirement even under worst-case conditions of partial compression at the extremes of the anticipated operating temperature range.

Ultraviolet radiation↗
NASA NTRS2017

Synchronous Separation, Seaming, Sealing and Sterilization (S4) using Brazing for Sample Containerization and Planetary Protection

The potential return of samples back to Earth from other planetary bodies would be based on planetary protection requirements that vary depending on the type of body [1]. Potential Mars Sample Return would require the protection of our planet from backward contamination. To fulfill this requirement, it would be necessary to implement “break the chain of contact (BTC)” process, where any material reaching Earth would have to be inside a container that is sealed with an extremely high level of confidence. In order to accomplish this, it would be necessary to contain the acquired samples and destroy any potential biological materials that may have contaminated the external surface of the container, while protecting the samples for further analysis. Using brazing, a novel synchronous separation, seaming, sealing and sterilization (S4) process for sample containerization and planetary protection has been conceived and demonstrated. A prototype double-wall container with inner and outer shells and Earth clean interstitial space was used for this demonstration. For potential Mars sample return, the double wall container would be consist of two halves and prepared on Earth. The on-orbit execution would consist of inserting the sample into one of the halves and then mating to the other half and melt the braze material to perform the S4 process. The use of brazing material that melts at temperatures higher than 500OC would assure sterilization of the exposed areas due to pyrolysis since carbon bonds are broken at this temperature. The process consists of two-steps, Step-1: the double wall container halves are fabricated and brazed on Earth; and Step-2: Assembly and brazing the samples on orbit. To prevent potential jamming during the process of mating the two halves of the double-wall container and the extraction of the brazed inner container, a double cone-within-cone approach has been conceived. The results of this study are described and discussed in this manuscript.

Bar-Cohen, Yoseph↗
NASA NTRS2019

Characterization of Prepreg Tack for Composite Manufacturing by Automated Fiber Placement

Automated fiber placement (AFP) has become the industry standard for large-scale production of carbon fiber reinforced plastics (CFRP) to improve rate and reduce defects associated with manual layup. Still, defects generated during AFP processes require manual, painstaking inspection by technicians and rework of the part when substantial defects are found. Prepreg (carbon fiber infused with uncured epoxy resin) tack is one of the primary factors that influences the generation of defects that arise during auto-mated fiber placement (AFP). Tack, as it relates to AFP processes and defect formation, can be understood as a combination of two stages, cohesion and decohesion. During the cohesion phase, two pieces of prepreg are brought into contact under elevated temperature and pressure. Compaction of the resin within the contact area will result in a degree of intimate contact, I, between the mating prepreg surfaces. Defect formation, as a result of decohesion between prepreg surfaces, occurs after the cohesion phase and arises due to stress from events such as fiber placement over an existing defect, on a contoured path, etc. (Figure 1). Tack strength resists the displacement of prepreg on a surface due to stresses developed during deposition.

Wohl, Christopher J↗
NASA NTRSDate not supplied

Fusion of Test and Analysis: Artemis I Booster to Mobile Launcher Interface Validation

NASA is in the midst of bold and exciting next steps in human exploration and spaceflight. The designs of the new Space Launch System (SLS), the Orion spacecraft and the Exploration Ground Systems (EGS) for vehicle processing and launch are essentially complete and there has been significant progress in manufacturing and assembly of specific hardware for the Artemis I and Artemis II missions. Equally as important, the program level and integrated system level testing and analyses are also well underway to support integrated verification, validation, and Certificate of Flight Readiness (CoFR) for Artemis I. Testing and analysis are key to addressing technical challenges faced by the Artemis missions. Building block approaches are required that provide the right balance between component, element, and/or system level testing that satisfies verification and validation objectives where uncertainties are quantified and minimized. Artemis I is a system of systems that requires a fusion of test and analysis that adeptly characterizes critical interfaces between major program elements. An example of this fusion involves characterizing the interface between the SLS booster and the Mobile Launcher (ML) Vertical Support Post (VSP) interfaces. Proper characterization of this interface represents a number of challenges beginning with the fact that it is a mating of ground support structure in the form of a civil structure to flight hardware. Both sides of the interface are built to different construction standards, but are governed by interface requirements to ensure compatibility when mated. From past program experience, the flexibility at the booster to ML interface is critical in developing accurate prelaunch stacking and cryogenic preloads, squat loads, and pad separation release of preloads and squat loads. This same premise holds for Artemis I. To characterize the asymmetric characteristics at this interface, careful consideration of static forces due to gravity loading with the commensurate effects due to leveling during booster stacking (i.e., spacing and shimming) and nonlinear geometric forces are necessary for inclusion in pre-test assessments. This paper will look at these issues for the upcoming Booster Pull Test in which two boosters will be installed on the ML and one of these boosters will undergo static lateral loading followed afterwards with dynamic excitation into resonance and free-decay. This paper evaluates the booster to ML interface characteristics by characterizing the interface flexibility between the booster aft skirt and the ML VSP interfaces. Furthermore, this paper methodically evaluates the effect of the following on the test outcome: gravitational effects on the booster and ML, the effects of VSP leveling, spacing, and shimming under gravitational loading during booster stacking, the effect of geometric nonlinear follower force due to cg offset as booster is laterally displaced, and the system coupling between the booster under test, ML, and the second booster. Simulated results for a static load pull and dynamic excitation provide insight into the differences in measurement responses when boundary conditions and geometric conditions are included and not included.

Joel W Sills Jr.↗
NASA NTRS2022

International Docking System Standard (IDSS) Interface Definition Document (IDD) Revision F

This IDSS IDD details the physical geometric mating interface and design loads requirements. The physical geometric interface requirements must be strictly followed to ensure physical spacecraft mating compatibility. This includes both defined components and areas that are void of components. The IDD also identifies common design parameters as identified in Section 3.0, e.g., docking initial conditions and vehicle mass properties. This information represents a recommended set of design values enveloping a broad set of design reference missions and conditions, which if accommodated in the docking system design, increases the probability of successful docking between different spacecraft.

Stanley R Donahoe↗
NASA NTRSDate not supplied

Advancing Dust Tolerant Mechanisms for a Sustained Exploration of the Moon

Introduction: “I think dust is probably one of our greatest inhibitors to a nominal operation on the Moon. I think we can overcome other physio-logical or physical or mechanical problems except dust.”– Gene Cernan, Apollo 17 Technical Debrief The Apollo missions revealed the impact of lu-nar dust on mechanisms. Lunar dust particles are jagged and electrostatically charged, giving them the ability to bind or damage mechanisms and alter thermal properties. Reports documented clogged equipment and jammed mechanisms in every mission, regardless of surface duration, as well as clogged mechanisms in the Extravehicular Mobility Suit (EMS), including zippers, wrist and hose locks, faceplates, and sunshades [1-2]. Several astronauts remarked they could not have sustained surface activity much longer because clogged joints would have frozen up completely [2]. Effective dust mitigation strategies are need-ed to support longer duration stays on the lunar surface [3-4]. State of the Art: Technology for mechanisms able to operate in dusty enviroments is advancing rapidly due to the needs of both Mars rovers and the Artemis program. Vacuum-tight connectors are essential for spacesuits and habitats, and their performance can be dependent on cleaning technologies, which have proven difficult on the lunar surface. Several TRL 3-5 technologies are undergoing tests with the expectation to reach TRL 6 within 1-2 years. Some mechanisms will be infused and tested on the VIPER (Volatiles Inves-tigating Polar Exploration Rover) mission planned for mid-2020s. NASA Funded Efforts: NASA has recognized the need for dust tolerant mechanisms, and has partnered with industry to advance the state-of-the-art. At NASA GRC, KSC, and JSC, the Dust Tolerant Mechanisms Project is working to devel-op advanced actuator seals for rotary joints and rotary bearing technologies for long-term sus-tained operation in lunar dust environments. An-other NASA project at NASA GRC, partnered with GSFC, JPL, and KSC is Motors for Dusty & Ex-treme Cold Environments (MDECE). MDECE is developing an unheated magnetically-geared mo-tor that can operate continuously for a long dura-tion at an ambient temperature of -243 ºC (33 K). NASA GRC has the capability to characterize the effects of dust on seals, mechanisms, and other mating surfaces and components under lunar conditions [5]. Through the SBIR/STTR program, NASA has funded several companies to advance dust toler-ant mechanisms via the Dust Tolerant Mecha-nisms sub-topic with applications in surface mobil-ity, spacesuits, connectors, joints, and more. LSIC and Community Efforts: The Lunar Surface Innovation Consortium (LSIC) Dust Miti-gation focus group has fostered collaborations across NASA, industry, and academia to develop solutions that minimizes the impact of lunar dust on robotic and human systems. Community ef-forts have included topical meetings on dust tol-erant mechanisms, featured technology presenta-tions, and feedback to NASA on potential gaps and needs. Testing: In 2021, NASA released NASA-STD-1008 [6]. This NASA Technical Standard estab-lishes minimum requirements and provides guid-ance for testing systems and hardware to be ex-posed to dust in planetary environments. The standard has specific sections dedicated to Mechanisms Testing (e.g. bearings, gears) as well as Seals and Mating Surfaces Testing (e.g. hatches, docking systems). Gaps and Needs: NASA is tracking dust tol-erant mechanisms as a gap in a cross-directorate analysis of capability areas needed to enable fu-ture human space-flight architectures. Two high-priority gap areas include additional facilities for testing mechanisms in lunar-surface conditions, and a better understanding of vulnerabilities to the smallest, nanometer-scale dust particles. Conclusion: Understanding and mitigating lu-nar dust is critical to successful, sustained opera-tions on the lunar surface – whether autonomous or otherwise. This presentation will discuss both the state-of-the-art and open needs in lunar dust tolerant mechanisms, technology impacts, mitiga-tion approaches, testing, LSIC community efforts, and more. References: [1] Gaier, J. R. (2020). The Im-pact of Dust on Lunar Surface Equipment During Apollo. Lunar Dust 2020. [2] GRC, & Gaier, J. R. (2005). The Effects of Lunar Dust on EVA Sys-tems During the Apollo Missions. [3] Johansen, M. R. (2020). An Update on NASA’s Lunar Dust Mitigation Strategy. Lunar Dust 2020. [4] ASI, CSA, ESA, JAXA, & NASA. (2016). Dust Mitiga-tion Gap Assessment Report. [5] Jimenez, N. et al (2022), LPSC Abstract 2572. [6] NASA-STD-1008, 2021.

J I Nunez↗
NASA NTRS2024

Electron Beam Welding of Additively Manufactured Niobium Alloy Heat Pipes

Additively manufactured refractory alloy-liquid metal heat pipes are being developed and tested for thermal management systems within nuclear propulsion and power applications. This study investigated electron beam (EB) welded joints on a laser powder bed fusion printed niobium alloy (C-103) and the impact of multiple joined heat pipe sections on working fluid flow and container leak-tightness. Results showed that EB welded joints connecting multiple heat pipe sections do not impact working fluid wicking behavior and the printed C-103 material and the EB welds joining the tubular sections created a leak-tight container. Interestingly, CT data showed an order of magnitude greater number and volume of porosity indications in the ground mating surface weld compared to the as-printed mating surface weld. The work concluded that AM is a viable manufacturing process for niobium alloy heat pipes and provided valuable insights for future AM heat pipe research and development.

Electron beam welding↗