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By NASA
The NESC Mechanical Systems TDT provides broad support across NASA’s mission directorates. We are a diverse group representing a variety of sub-disciplines including bearings, gears, metrology, lubrication and tribology, mechanism design, analysis and testing, fastening systems, valve engineering, actuator engineering, pyrotechnics, mechatronics, and motor controls. In addition to providing technical support, the
TDT owns and maintains NASA-STD-5017, “Design and Development Requirements for Space Mechanisms.”
Mentoring the Next Generation
The NESC Mechanical Systems TDT actively participates in the Structures, Loads & Dynamics, Materials, and Mechanical Systems (SLAMS) Early Career Forum that mentors early-career engineers. The TDT sent three members to this year’s forum at WSTF, where early-career engineers networked with peers and NESC mentors, gave presentations on tasks they worked on at their home centers, and attended splinter sessions where they collaborated with mentors.
New NASA Valve Standard to Reduce Risk and Improve Design and Reliability
Valve issues have been encountered across NASA’s programs and continue to compromise mission performance and increase risk, in many cases because the valve hardware was not qualified in the environment as specified in NASA-STD-5017. To help address these issues, the Mechanical Systems TDT is developing a NASA standard for valves. The TDT assembled a team of subject matter experts from across the Agency representing several disciplines including mechanisms, propulsion, environmental control and life support systems, spacesuits, active thermal control systems, and materials and processes. The team has started their effort by reviewing lessons learned and best practices for valve design and hope to have a draft standard ready by the end of 2025.
Bearing Life Testing for Reaction Wheel Assemblies
The Mechanical Systems TDT just concluded a multiyear bearing life test on 40 motors, each containing a pair of all steel bearings of two different conformities or a pair of hybrid bearings containing silicon nitride balls. The testing confirmed that hybrid bearings outperformed their steel counterparts, and bearings with higher conformity (54%) outperformed bearings with lower conformity (52%). The team is disassembling and inspecting the bearings, and initial results have been surprising. The TDT was able to “recover” some of the bearings that failed during the life test and get them running as well as they did when testing began. Some bearings survived over five billion revolutions and appeared like new when they were disassembled and inspected. These results will be published once analysis is complete.
X-57 Design Assessment
The Mechanical Systems TDT was asked by the Aeronautics Mission Directorate to assess the design of the electric cruise motors installed on X-57. The team responded quickly to meet the Project’s schedule, making an onsite visit and attending numerous technical interchange meetings. After careful review of the design, the TDT identified areas for higher-level consideration and risk assessment and attended follow-on reviews to provide additional comments and advice.
CLARREO Pathfinder Inner Radial Bearing Anomaly
The Climate Absolute Radiance and Refractivity Observatory (CLARREO) Pathfinder was designed to take highly accurate measurements of reflected solar radiation to better-understand Earth’s climate. During payload functional testing, engineers detected a noise as the HySICS pointing system was rotated from its normal storage orientation. Mechanical Systems TDT members reviewed the design and inspection reports after disassembly of the inner bearing unit, noticing contact marks on the bore of the inner ring and the shaft that confirmed that the inner ring of the bearing was moving on the shaft with respect to the outer ring. Lubricant applied to this interface resolved the noise problem and allowed the project to maintain schedule without any additional costs.
JPL Wheel Drive Actuator Extended Life Test Independent Review Team
A consequence of changes to its mission on Mars will require the Perseverance Rover to travel farther than originally planned. Designed to drive 20 km, the rover will now need to drive ~91 km to rendezvous and support Mars sample tube transfer to the Sample Retrieval Lander. The wheel drive actuators with integral brakes had only been life tested to 40 km, so a review was scheduled to discuss an extended life test. The OCE Science Mission Directorate Chief Engineer assembled an independent review team (IRT) that included NESC Mechanical Systems TDT members. This IRT issued findings and guidance that questioned details of the JPL assumptions and plan. Several important recommendations were made that improved the life test plan and led to the identification of brake software issues that were reducing brake life. The life test has achieved 40 km of its 137 km goal and is ongoing. In addition, software updates were sent to the rover to improve brake life.
Orion Crew Module Hydrazine Valve
When an Orion crew module hydrazine valve failed to close, the production team asked the Mechanical Systems TDT for help. A TDT member attended two meetings and then visited the valve manufacturer, where it was determined this valve was a scaled-down version of the 12-inch SLS prevalve that was the subject of a previous NESC assessment and shared similar issues. The Orion Program requested NESC materials and mechanical systems support. The Mechanical Systems TDT member then worked closely with a Lockheed Martin (LM) Fellow for Mechanisms to review all the valve vendor’s detailed drawings and assembly procedures and document any issues. A follow-on meeting was held to brief both the LM and NASA Technical Fellows for Propulsion that a redesign and requalification was recommended. These recommendations have now been elevated to the LM Vice President for Mission Success and the LM Chief Engineer for Orion.
NASA’s Perseverance Mars rover selfie taken in July 2024.
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By NASA
This article is from the 2024 Technical Update.
Multiple human spaceflight programs are underway at NASA including Orion, Space Launch System, Gateway, Human Landing System, and EVA and Lunar Surface Mobility programs. Achieving success in these programs requires NASA to collaborate with a variety of commercial partners, including both new spaceflight companies and robotic spaceflight companies pursuing crewed spaceflight for the first time. It is not always clear to these organizations how to show their systems are safe for human spaceflight. This is particularly true for avionics systems, which are responsible for performing some of a crewed spacecraft’s most critical functions. NASA recently published guidance describing how to show the design of an avionic system meets safety requirements for crewed missions.
Background
The avionics in a crewed spacecraft perform many safety critical functions, including controlling the position and attitude of the spacecraft, activating onboard abort systems, and firing pyrotechnics. The incorrect operation of any of these functions can be catastrophic, causing loss of the crew. NASA’s human rating requirements describe the need for “additional rigor and scrutiny” when designing safety-critical systems beyond that done
for uncrewed spacecraft [2]. Unfortunately, it is not always clear how to interpret this guidance and show an avionics architecture is sufficiently safe. To address this problem, NASA recently published NASA/TM−20240009366 [1]. It outlines best practices for designing safety-critical avionics, as well as describes key artifacts or evidence NASA needs to assess the safety of an avionics architecture.
Failure Hypothesis
One of the most important steps to designing an avionics architecture for crewed spacecraft is specification of the failure hypothesis (FH). In short, the FH summarizes any assumptions the designers make about the type, number, and persistence of component failures (e.g., of onboard computers, network switches). It divides the space of all possible failures into two parts – failures the system is designed to tolerate and failures it is not.
One key part of the FH is a description of failure modes the system can tolerate – i.e., the behavior exhibited by a failed component. Failure modes are categorized using a failure model. A typical failure model for avionics splits failures into two broad categories:
Value failures, where data produced by a component is missing (i.e., an omissive failure) or incorrect (i.e., a transmissive failure). Timing failures, where data is produced by a component at the wrong time.
Timing failures can be further divided into many sub-categories, including:
Inadvertent activation, where data is produced by a component without the necessary preconditions. Out-of-order failures, where data is produced by a component in an incorrect sequence. Marginal timing failures, where data is produced by a component slightly too early or late.
In addition to occurring when data is produced by a component, these failure modes can also occur when data enters a component. (e.g., a faulty component can corrupt a message it receives). Moreover, all failure modes can manifest in one of two ways:
Symmetrically, where all observers see the same faulty behavior. Asymmetrically, where some observers see different faulty behavior.
Importantly, NASA’s human-rating process requires that each of these failure modes be mitigated if it can result in catastrophic effects [2]. Any exceptions must be explicitly documented and strongly justified. In addition to specifying the failure modes a system can tolerate, the FH must specify any limiting assumptions about the relative arrival times of permanent failures and radiation-induced upsets/ errors or the ability for ground operator to intervene to safe the system or take recovery actions. For more information on specifying a FH and other artifacts needed to evaluate the safety of an avionics architecture for human spaceflight, see the full report [1].
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By NASA
NASA, along with members of the FAA and commercial drone engineers, gathered in the Dallas area May 25, 2024, to view multiple delivery drones operating in a shared airspace beyond visual line of sight using an industry-developed, NASA-originated uncrewed aircraft system traffic management system.NASA NASA’s Uncrewed Aircraft Systems Traffic Management Beyond Visual Line of Sight (UTM BVLOS) subproject aims to support the growing demand for drone flights across the globe.
Uncrewed aircraft systems (UAS), or drones, offer an increasing number of services, from package delivery to critical public safety operations, like search and rescue missions. However, without special waivers, these flights are currently limited to visual line of sight – or only as far as the pilot can see – which is roughly no farther than one mile from the operator. As the FAA works to authorize flights beyond this point, NASA is working with industry and the Federal Aviation Administration (FAA) to operationalize an uncrewed traffic management system for these operations.
NASA’s UTM Legacy
NASA’s Uncrewed Aircraft Systems Traffic Management, or UTM, was first developed at NASA’s Ames Research Center in California’s Silicon Valley in 2013, and enables drones to safely and efficiently integrate into air traffic that is already flying in low-altitude airspace. UTM is based on digital sharing of each user’s planned flight details, ensuring each user has the same situational awareness of the airspace.
NASA performed a series of drone flight demonstrations using UTM concepts in rural areas and densely populated cities under the agency’s previous UTM project . And commercial drone companies have since utilized NASA’s UTM concepts and delivery operations in limited areas.
Several projects supporting NASA’s Advanced Air Mobility or AAM mission are working on different elements to help make AAM a reality and one of these research areas is automation.NASA / Graphics UTM Today
NASA research is a driving force in making routine drone deliveries a reality. The agency is supporting a series of commercial drone package deliveries beyond visual line of sight, some of which kicked off in August 2024 in Dallas, Texas. Commercial operators are using NASA’s UTM-based capabilities during these flights to share data and planned flight routes with other operators in the airspace, detect and avoid hazards, and maintain situational awareness. All of these capabilities allow operators to safely execute their operations in a shared airspace below 400 feet and away from crewed aircraft. These drone operations in Dallas are a collaboration between NASA, the FAA, industry drone operators, public safety operators, and others.
These initial flights will help validate UTM capabilities through successful flight operation evaluations and inform the FAA’s rulemaking for safely expanding drone operations beyond visual line of sight.
The agency will continue to work with industry and government partners on more complex drone operations in communities across the country. NASA is also working with partners to leverage UTM for other emerging operations, including remotely piloted air cargo delivery and air taxi flights. UTM infrastructure could also support high-altitude operations for expanded scientific research, improved disaster response, and more.
NASA UTM BVLOS
NASA’s UTM Beyond Visual Line of Site (UTM BVLOS) subproject is leading this effort, under the Air Traffic Management eXploration portfolio within the agency’s Aeronautics Research Mission Directorate. This work is in support of NASA’s Advanced Air Mobility Mission, which seeks to transform our communities by bringing the movement of people and goods off the ground, on demand, and into the sky.
Keep Exploring Discover More Topics From NASA
Missions
Humans in Space
Climate Change
Solar System
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By Space Force
The Air Force Research Laboratory, or AFRL, launched the Space Power InfraRed Regulation and Analysis of Lifetime, or SPIRRAL, experiment, Nov. 4. SPIRRAL, flown by AFRL through the DOD Space Test Program, will characterize the performance of Variable Emissivity Materials, or VEMs, an approach toward solving thermal challenges for space vehicles while on-orbit.
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By European Space Agency
Video: 00:02:18 At ESA, through the Advanced Research in Telecommunications Systems programme, we’re addressing solutions for when safety and security of communication services cannot be guaranteed by the terrestrial networks alone. With our programme Space systems for Safety and Security, or 4S, we are pioneering cutting-edge development of secure and resilient satellite communication systems, technologies and services to improve life on Earth.
Picture a world where our critical infrastructure is protected from cyber threats, and where communication links work when the world around them doesn't. A transportation network where safety is not just a priority, but a guarantee. Where air traffic flows completely efficiently, reliable and connected. Railways operate without interruption, and shipping can navigate safely and securely.
Imagine that our first responders are coordinating via seamless communications, and institutional agencies are acting rapidly and decisively when there's a crisis. All thanks to secure and safe satellite communication systems, orbiting above the planet. This is the future we're building with the 4S programme. A future where space systems safeguard our security, making sure that connectivity remains our greatest strength. Join us as we continue to push the boundaries of innovation.
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