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NASA NTRS1996

Reliability and Maintainability Model (RAM): User and Maintenance Manual: Improved Supportability Analysis - Part 2

This report documents the procedures for utilizing and maintaining the Reliability & Maintainability Model (RAM) developed by the University of Dayton for the National Aeronautics and Space Administration (NASA) Langley Research Center (LaRC). The purpose of the grant is to provide support to NASA in establishing operational and support parameters and costs of proposed space systems. As part of this research objective, the model described here was developed. This Manual updates and supersedes the 1995 RAM User and Maintenance Manual. Changes and enhancements from the 1995 version of the model are primarily a result of the addition of more recent aircraft and shuttle R&M data.

Ebeling, Charles E.↗

NASA NTRS1999

One for All: Maintaining a Single Schedule Database for Large Development Projects

Efficiently maintaining and controlling a single schedule database in an Integrated Product Team environment is a significant challenge. It's accomplished effectively with the right combination of tools, skills, strategy, creativity, and teamwork. We'll share our lessons learned maintaining a 20,000 plus task network on a 36 month project.

Hilscher, R.↗

NASA NTRS1996

Daily Supine LBNP Treadmill Exercise Maintains Upright Exercise Capacity During 14 Days of Bed Rest

Exposure to microgravity or bed rest reduces upright exercise capacity. Exercise modes, durations, and intensities which will effectively and efficiently counteract such deconditioning are presently unresolved. We that daily supine treadmill interval training with lower body negative pressure (LBNP) would prevent reduction in upright exercise capacity during 14 days of 6 deg. head-down bed rest (BR). Eight healthy male subjects underwent two 14 day BR protocols separated by 3 months. In a crossover design, subjects either remained at strict BR or performed 40 min of daily exercise consisting of supine walking and running at intensities varying from 40-80% of pre-BR upright peak oxygen uptake (VO2). LBNP during supine exercise was used to provide 1.0 to 1.2 times body weight of footward force. An incremental upright treadmill test to measure submaximal and peak exercise responses was given pre- and post-BR. In the non-exercise condition, peak VO2 and time to exhaustion were reduced 16 +/- 4% and 10 +/- 1% (p less than 0.05), respectively, from pre-BR. With LBNP exercise these variables were not significantly different (NS) from pre-BR. During submaximal treadmill speeds after BR, heart rate was higher (11 +/- 11 bpm, p less than 0.05) and respiratory exchange ratio was elevated (p less than 0.05) in the no exercise condition. Both were maintained at pre-BR levels in the LBNP exercise condition (NS from pre-BR). Since this supine treadmill interval training with addition of LBNP maintained upright exercise responses and capacity during BR, this countermeasure may also be effective during space flight.

Ertl, Andy C.↗

NASA NTRS1990

Low external pH replaces 2,4-D in maintaining and multiplying 2,4-D-initiated embryogenic cells of carrot

A mixed culture comprised of both embryonic globules and nonembryogenic callus was derived from seedling hypocotyls of Daucus carota cv. Scarlet Nantes on 2,4-D- containing medium using well-established methods. Then the mixed cultures were transferred to, and serially subcultured on, a hormone-free medium near pH 4. The medium contained 1 mM NH4+ as the sole nitrogen source. When cultured in this way, embryonic globules were able to multiply without development into later embryo stages. Nonembryogenic callus did not survive. Continuous culture of embryonic globules on this low pH hormone-free medium yielded cultures consisting entirely of preglobular stage proembryos (PGSPs). PGSP cultures have been maintained as such with continuous multiplication for nearly 2 years without loss of embryogenic potential. These hormone-free-maintained PGSPs continue their development to later embryo stages when cultured on the same hormone-free medium buffered at pH 5.8. We show that hormone-free medium near pH 4 can replace 2,4-D in its ability to sustain multiplication of 2,4-D-initiated embryogenic cells of carrot at an acceptable growth rate without their development into later embryo stages. This procedure provides selective conditions that do not permit the growth of non-embryogenic cells while providing an adequate environment for embryogenic cell proliferation and should prove invaluable in studying habituation.

Non-NASA Center↗

NASA NTRS1997

Upright exercise or supine lower body negative pressure exercise maintains exercise responses after bed rest

Adaptation to bed rest or space flight is accompanied by an impaired ability to exercise in an upright position. We hypothesized that a daily, 30-min bout of intense, interval exercise in upright posture or supine against lower body negative pressure (LBNP) would maintain upright exercise heart rate and respiratory responses after bed rest. Twenty-four men (31 +/- 3 yr) underwent 5 d of 6 degree head-down tilt: eight performed no exercise (CON), eight performed upright treadmill exercise (UPex), and eight performed supine treadmill exercise against LBNP at -51.3 +/- 0.4 mm Hg (LBNPex). Submaximal treadmill exercise responses (56, 74, and 85% of VO2peak) were measured pre- and post-bed rest. In CON, submaximal heart rate, respiratory exchange ratio, and ventilation were significantly greater (P < or = 0.05) after bed rest. In UPex and LBNPex, submaximal exercise responses were similar pre- and post-bed rest. Our results indicate that a daily 30-min bout of intense, interval upright exercise training or supine exercise training against LBNP is sufficient to maintain upright exercise responses after 5 d of bed rest. These results may have important implications for the development of exercise countermeasures during space flight.

NASA Center ARC↗

NASA NTRS2008

Lower Body Negative Pressure Treadmill Exercise and Resistive Exercise Countermeasures Maintain Physiologic Function in Women during Simulated Microgravity

We hypothesized that supine LBNP treadmill exercise combined with Flywheel resistive exercise maintains upright physiologic responses following 60-days of head-down tilt (HDT) bed rest (BR). METHODS: 16 healthy women (age 25-40 years) underwent 60-days HDT (-6deg.) BR. Women were assigned to either a non-exercise control group (CON, n=8) or to an exercise group (EX, n=8). EX subjects performed a 40-min, variable intensity LBNP exercise protocol at foot-ward forces between 1.0-1.1 times body weight, followed by 10- min of resting LBNP 3-4 days/week. Resistive exercise of maximal concentric and eccentric supine leg press and heel raise exercises were performed using a flywheel ergometer 2-3 days/week. IRBs approved this study with informed/written consent. RESULTS: Post-BR VO2pk was not different in EX (-3.3+/-1.2%) but decreased significantly in CON (-21.2+/-2.1%), p< 0.05. Post-BR orthostatic tolerance time (mean se) decreased significantly less in EX (19.3+/-1.3 to 14.4+/-1.5 min) than in CON (17.5+/-0.1 to 9.1+/- 1.5 min), p=0.03. Post-BR muscle strength decreased significantly in CON, but was preserved in EX. Post-BR bone resorption was greater than pre-BR in both groups (p<0.05). Bone formation markers, were significantly elevated (p<0.05) in EX than in CON. CONCLUSIONS: Supine LBNP treadmill exercise along with flywheel resistive exercise maintains upright exercise capacity, orthostatic responses and muscle strength during 60-days HDT BR.

Macias, B. R.↗

NASA NTRS1966

Charged Probes, Bourdon Tubes Maintain Cryogenic Liquid Level

The problem: To design a system that automatically maintains the fluid level in a liquid nitrogen cold trap. It is frequently necessary to operate a vacuum system using one or more cold traps for a prolonged period with the cold trap liquid level maintained between set limits. Electronic devices have been subject to failure due to the effect on components of cryogenic temperatures. The solution: An automatic liquid nitrogen dispensing system that uses gas filled probes, driving Bourdon tube gauges equipped with microswitches that, through a relay, control a solenoid valve in the liquid nitrogen storage line.

Krejsa, Mylo J.↗

NASA NTRS2011

Maintaining Adequate CO2 Washout for an Advanced EMU via a New Rapid Cycle Amine Technology

Over the past several years, NASA has realized tremendous progress in Extravehicular Activity (EVA) technology development. This has been evidenced by the progressive development of a new Rapic Cycle Amine (RCA) system for the Advanced Extravehicular Mobility Unit (AEMU) Portable Life Support Subsystem (PLSS). The PLSS is responsible for the life support of the crew member in the spacesuit. The RCA technology is responsible for carbon dioxide (CO2) and humidity control. Another aspect of the RCA is that it is on-back vacuum-regenerable, efficient, and reliable. The RCA also simplifies the PLSS schematic by eliminating the need for a condensing heat exchanger for humidity control in the current EMU. As development progresses on the RCA, it is important that the sizing be optimized so that the demand on the PLSS battery is minimized. As well, maintaining the CO2 washout at adequate levels during an EVA is an absolute requirement of the RCA and associated ventilation system. Testing has been underway in-house at NASA Johnson Space Center and analysis has been initiated to evaluate whether the technology provides exemplary performance in ensuring that the CO2 is removed sufficiently enough and the ventilation flow is adequate enough to maintain CO2 1 Project Engineer, Space Suit and Crew Survival Systems Branch, Crew and Thermal Systems Division, 2101 NASA Parkway, Houston, TX 77058/EC5. washout in the AEMU spacesuit helmet of the crew member during an EVA. This paper will review the recent developments of the RCA unit, the testing results performed in-house with a spacesuit simulator, and the associated analytical work along with insights from the medical aspect on the testing.

Chullen, Cinda↗

NASA NTRS2012

Maintaining Adequate CO2 Washout for an Advanced EMU via a New Rapid Cycle Amine Technology

Over the past several years, NASA has realized tremendous progress in Extravehicular Activity (EVA) technology development. This has been evidenced by the progressive development of a new Rapid Cycle Amine (RCA) system for the Advanced Extravehicular Mobility Unit (AEMU) Portable Life Support Subsystem (PLSS). The PLSS is responsible for the life support of the crew member in the spacesuit. The RCA technology is responsible for carbon dioxide (CO2) and humidity control. Another aspect of the RCA is that it is on-back vacuum-regenerable, efficient, and reliable. The RCA also simplifies the PLSS schematic by eliminating the need for a condensing heat exchanger for humidity control in the current EMU. As development progresses on the RCA, it is important that the sizing be optimized so that the demand on the PLSS battery is minimized. As well, maintaining the CO2 washout at adequate levels during an EVA is an absolute requirement of the RCA and associated ventilation system. Testing has been underway in-house at NASA Johnson Space Center and analysis has been initiated to evaluate whether the technology provides exemplary performance in ensuring that the CO2 is removed sufficiently and the ventilation flow is adequate for maintaining CO2 washout in the AEMU spacesuit helmet of the crew member during an EVA. This paper will review the recent developments of the RCA unit, testing planned in-house with a spacesuit simulator, and the associated analytical work along with insights from the medical aspect on the testing. 1

Chullen, Cinda↗

NASA NTRS2011

Automated Methods to Maintain Aircraft Separation

The air traffic control system in the United States has a great track-record for safety. As more aircraft enter the system at a given time, the situation becomes more complex though. Researchers at NASA are attempting to leverage advances in many fields including optimization, data mining, and numerical modeling of systems to improve the air-transportation system maintaining safety while increasing throughput and reducing delays. This talk will give a brief overview of the research at NASA towards modernizing the air-transportation system. It will then focus on the specific area of automation tools for maintaining physical separation between aircraft known as Separation Assurance.

Lauderdale, Todd↗

NASA NTRS2014

Maintaining Aura's Orbit Requirements While Performing Orbit Maintenance Maneuvers Containing an Orbit Normal Delta-V Component

The Earth Observing System (EOS) Afternoon Constellation consists of five member missions (GCOM-W1, Aqua, CALIPSO, CloudSat, and Aura), each of which maintain a frozen, sun-synchronous orbit with a 16-day repeating ground track that follows the Worldwide Reference System-2 (WRS-2). Under nominal science operations for Aura, the propulsion system is oriented such that the resultant thrust vector is aligned 13.493 degrees away from the velocity vector along the yaw axis. When performing orbit maintenance maneuvers, the spacecraft performs a yaw slew to align the thrust vector in the appropriate direction. A new Drag Make Up (DMU) maneuver operations scheme has been implemented for Aura alleviating the need for the 13.493 degree yaw slew. The focus of this investigation is to assess the impact that no-slew DMU maneuver operations will have on Aura's Mean Local Time (MLT) which drives the required along track separation between Aura and the constellation members, as well as Aura's frozen orbit properties, eccentricity and argument of perigee. Seven maneuver strategies were analyzed to determine the best operational approach. A mirror pole strategy, with maneuvers alternating at the North and South poles, was implemented operationally to minimize impact to the MLT. Additional analysis determined that the mirror pole strategy could be further modified to include frozen orbit maneuvers and thus maintain both MLT and the frozen orbit properties under noslew operations.

Aqua↗

NASA NTRS2014

Maintaining Aura's Orbit Requirements Under New Maneuver Operations

The Earth Observing System (EOS) Afternoon Constellation consists of five member missions (GCOM-W1, Aqua, CALIPSO, CloudSat, and Aura), each of which maintain a frozen, sun-synchronous orbit with a 16-day repeating ground track that follows the Worldwide Reference System-2 (WRS-2). Under nominal science operations for Aura, the propulsion system is oriented such that the resultant thrust vector is aligned 13.493 degrees away from the velocity vector along the yaw axis. When performing orbit maintenance maneuvers, the spacecraft performs a yaw slew to align the thrust vector in the appropriate direction. A new Drag Make Up (DMU) maneuver operations scheme has been implemented for Aura alleviating the need for the 13.493 degree yaw slew. The focus of this investigation is to assess the impact that no-slew DMU maneuver operations will have on Auras Mean Local Time (MLT) which drives the required along track separation between Aura and the constellation members, as well as Auras frozen orbit properties, eccentricity and argument of perigee. Seven maneuver strategies were analyzed to determine the best operational approach. A mirror pole strategy, with maneuvers alternating at the North and South poles, was implemented operationally to minimize impact to the MLT. Additional analysis determined that the mirror pole strategy could be further modified to include frozen orbit maneuvers and thus maintain both MLT and the frozen orbit properties under no-slew operations

aura↗

NASA NTRS2015

PTM Along Track Algorithm to Maintain Spacing During Same Direction Pair-Wise Trajectory Management Operations

Pair-wise Trajectory Management (PTM) is a cockpit based delegated responsibility separation standard. When an air traffic service provider gives a PTM clearance to an aircraft and the flight crew accepts the clearance, the flight crew will maintain spacing and separation from a designated aircraft. A PTM along track algorithm will receive state information from the designated aircraft and from the own ship to produce speed guidance for the flight crew to maintain spacing and separation

Carreno, Victor A.↗

NASA NTRS2019

Effectiveness of Redundant Communications Systems in Maintaining Operational Control of Small Unmanned Aircraft

As a part of NASA’s Unmanned Aircraft System (UAS) Traffic Management (UTM) research, a test was performed to evaluate the effectiveness of the redundant Command and Control (C2) communications system for maintaining operational control of small UAS in the airspace over a rural area. In the test, operators set up a primary and a secondary UAS C2 communications system, sent a maneuver command to an Unmanned Aircraft (UA) with and without a functioning primary system, then verified the execution of the sent command to confirm the operator control. Operators reported that the tested redundancy configurations were effective in maintaining operational control in the test airspace over rural locations. Since the next phase of UTM research focuses on operations in an urban area where an increased level of Radio Frequency (RF) activities occur compared to a rural area, four recommendations are provided to sustain the effectiveness of redundancy in urban operations. First, the operator should not include C2 systems that use the industrial, scientific, and medical (ISM) radio bands in redundancy configurations. Second, the operator should verify the RF characteristics of the intended operation area and examine the area’s radio noise floor. Third, the operator should monitor the availability, quality, and reliability of communications services used by a redundant system. Fourth, the small UAS community should adopt a standard set of contingency steps to handle the loss of C2 communications so that such events are managed in a consistent manner across the airspace. The insights from the test will be used to accommodate the FAA’s UAS integration effort.

Jung, Jaewoo↗

NASA NTRS2019

Effectiveness of Redundant Communications Systems in Maintaining Operational Control of Small Unmanned Aircraft

NASA has been researching prototype technologies for an Unmanned Aircraft System (UAS) Traffic Management (UTM) system to facilitate enabling of safe and efficient civilian low-altitude airspace and UAS operations, in a series of Technical Capability Levels (TCL) activities that are increasingly complex. In TCL1, completed in 2015, visual line-of-sight operations such as agriculture, firefighting and infrastructure monitoring were addressed with a focus on geofencing and operations scheduling. Technologies and requirements needed for beyond visual line-of-sight (BVLOS) operations in sparsely populated areas were examined in TCL2 in 2016, and those for operations over moderately populated areas in TCL3 in 2017 and 2018. TCL4 will build on the earlier TCLs and focus on technologies and requirements for operations in higher-density urban areas for tasks such as news gathering, package delivery and for managing large-scale contingencies. This paper describes a communications test conducted in TCL3 and discusses insights gained from the test. In the test, operators were directed to equip UAS with redundant Command and Control (C2) communications systems, send a maneuver command to Unmanned Aircraft (UA) via the primary system, then verify execution of the sent command. This exercise was repeated with each redundant system. The test was designed to assess effectiveness of redundant C2 systems in maintaining operational control of UA. Several UAS were configured with varying arrangements to achieve redundancy, including two identical radio modems using the same frequency band, WiFi and Long-Term Evolution (LTE) cellular modems, etc. From the test, digital data such as time maneuver command sent, time maneuver verified, etc., were collected. Descriptions of methods to detect loss of C2 communications and contingency steps for such event were collected and assessed. The final paper will include a detailed analysis of the collected data leading to the following insights. First, effectiveness of redundant C2 systems depends on several factors, such as operational environment and communications service availability. For example, use of two identical point-to-point radio to connect operator and UA on the same frequency band can be effective in mitigating radio malfunction when operating in an environment where possibility of Radio Frequency (RF) interference is low, such as over open plains. However, the same arrangement may not be effective where high level of RF transmissions in broad spectrum ranges can be expected, such as over or near urban areas. For redundant systems that consist of external communications services, such as cellular and satellite communications network, redundancy is maintained only in the areas where more than one services are available. Therefore, UAS operators should have the means to plan for and monitor the performance of external communications services they are relying on to control UA. Second, communications performance needs, such as the minimum data transfer rate and the maximum tolerable latency, should be assessed to reflect the potential hazard that can come from loss of UA control. For example, UA operations over desolate area pose less hazard to people than operations over densely populated area and performance need for the former would be less than the latter.

Jung, Jaewoo↗

NASA NTRSDate not supplied

Operating and Maintaining the JWST Cleanroom attached to JSC's Chamber A during preparations for the OTIS Cryogenic Thermal Vacuum Test

In order to maintain cleanliness during preparations for JWST’s OTIS (Optical Telescope Element-Integrated Science Instrument Module) Cryogenic Thermal Vacuum Test, a cleanroom was built that attached directly to the 60-year-old Chamber A. The cleanroom and chamber were outfitted with independent environmental control systems each providing ISO Class 71 air cleanliness. To maintain balanced, positive pressure in both the cleanroom and chamber volumes, a special control protocol was developed and successfully implemented. Dual back-up environmental control units (one each for the chamber and cleanroom) were installed just outside the building to provide environmental control redundancy due to a single source chilled water supply and weather threats. In addition, lack of a dedicated cleanroom airlock facilitating clean ingress and egress made it necessary to perform additional cleaning and packaging, as well as augment the uncontrolled truck lock space with small clean tents for pre-cleaning. Special procedures were developed to allow ingress of extra-large support equipment required for load testing of the cleanroom crane, installation of optical equipment in Chamber A and accommodation of the OTIS shipping container. A thorough bake-out and cleaning of Chamber A was also necessary to reduce volatiles from the shroud’s black thermal paint and to reduce particle fallout. Acrylic adhesive fracture discovered during early cryo-testing represented a significant challenge that was successfully mitigated prior to OTIS testing. A dedicated team of Contamination Control (CC) Technicians was specifically trained to clean support equipment and screen materials entering the cleanroom and chamber to ensure cleanliness and vacuum compatibility.

Optics↗

NASA NTRSDate not supplied

Operating and Maintaining the JWST Cleanroom attached to JSC's Chamber A during preparations for the OTIS Cryogenic Thermal Vacuum Test

James Webb Space Telescope↗

NASA NTRSDate not supplied

Material Compatibility Study of Coated Metals to Maintain Biocidal Silver in a Spacecraft Potable Water System

Ionic silver-based biocide remains an option of choice for microbial control in spacecraft potable water systems. However, depletion of silver ions by wetted materials readily reduces ionic silver to nonbiocidal levels. This phenomenon occurs via various transport mechanisms at the liquid-solid interfaces between the silver-containing water and adjacent surfaces. Consequently, challenges remain in the design and/or selection of materials that can be used for the wetted system components that will help ensure silver is maintained at biocidal levels. Since silver has been baselined, and/or remains, as a potable water biocide option for several future spacecraft potable water systems, a multitiered approach is being investigated, looking at heritage materials, new processes, and/or alterative materials. This study conducted the application of eleven chemically-resistant coatings onto coupons that were cut out from three types of spacecraft-grade metals (Titanium Grade 2, Inconel 718, and 316L Stainless Steel) to investigate the performance of this material strategy as a barrier against silver depletion. In this investigation, the coated metals were immersed in a static 400 parts per billion silver biocide solution at a surface-area-to-volume ratio of 2.0 cm^(-1) and left to soak for predefined time periods. The concentration of the solution in contact with the coated samples was analyzed at various points via inductively coupled plasma mass spectrometry, and the measurements were interpreted as silver retention percentages over time. This paper summarizes the coating selection process, the configuration of the test, and the performance of each coating-metal combination at diminishing silver depletion. The preliminary results demonstrate that some of the selected coatings succeeded at maintaining biocidal silver concentrations far beyond the corresponding base metal in a similar test. The knowledge acquired through this investigation supports the deploying of coatings on plumbing lines for the integration of biocidal silver in the water system architecture of a spacecraft. Nevertheless, further testing must be continued to assess the performance of these coatings on other wetted geometries and any implications of unifying this material strategy with traditional and developmental engineering design processes for spacecraft potable water systems.

water↗