SEARCH · Engineering Papers
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
To learn how we might solve some important and challenging problems that require us to step into extreme or “wicked problem” domains. Where systems-level engineering and design are required to integrate with other domains. Connect with the external community to cross-pollinate on best methods, processes, and tools.
The world is changing rapidly. And with it, so are the potential futures for humanity. Many of these potential futures pose hidden threats, while others offer new opportunities for aviation and the broader aerospace community. To mitigate these risks and capitalize on opportunities, organizations must work to deeply understand these potential future scenarios and uncover any underlying drivers. Organizations will be more equipped and informed when making strategic investment decisions by better understanding these threats, opportunities, and drivers . The future scenarios and their threats and opportunities described in this paper were identified through a series of extensive brainstorming workshops, collectively titled MADNESS (Mapping for Aviation Driven by Needs Emergence and Satiating Society). These workshops engaged NASA civil servants and contractors with diverse backgrounds through a facilitated process of future scenario development and critique. The participants were led through exercises focused on a time horizon spanning from 2022 to 2072 and on problems that aviation might solve and or create during this period. From the broad results, two patterns of critical uncertainty emerged: “availability” (scarcity versus abundance) and “transparency” (openness versus security and privacy). The successful iteration and ideation across the MADNESS workshops also suggests a repeatable mechanism for strategic risk exploration across a variety of NASA and industry stakeholders.
No abstract provided
As the world grows increasingly networked and complex, so do challenges faced by aviation and technology professionals (e.g., fighting wildfires and increasing access to healthcare). There is a need to develop new methods to tackle complex socio-technical problems relevant to aviation. The concept of “wicked” problems offers new methods and perspectives for framing complex challenges. In this paper, we present two modes of operationalizing “wickedness” used by NASA’s Convergent Aeronautics Solutions (CAS) Project to develop transformative innovations in aviation: as an analytical, evaluative tool and a creative, generative tool. Through project examples, we demonstrate that using wickedness as a creative tool during the design process enables rich problem exploration with diverse stakeholders and reflection on how a problem is formulated, while usage as an analytical tool can provide criteria for project selection if internal agreement on the definitions of such criteria is established. Operationalizing wickedness as a creative tool may also enable organizational development of a generative mindset to better adapt to our rapidly changing future.
As the world grows increasingly networked and complex, so do challenges faced by aviation and technology professionals (e.g., fighting wildfires and increasing access to healthcare). There is a need to develop new methods to tackle complex socio-technical problems relevant to aviation. The concept of “wicked” problems offers new methods and perspectives for framing complex challenges. In this paper, we present two modes of operationalizing “wickedness” used by NASA’s Convergent Aeronautics Solutions (CAS) Project to develop transformative innovations in aviation: as an analytical, evaluative tool and a creative, generative tool. Through project examples, we demonstrate that using wickedness as a creative tool during the design process enables rich problem exploration with diverse stakeholders and reflection on how a problem is formulated, while usage as an analytical tool can provide criteria for project selection if internal agreement on the definitions of such criteria is established. Operationalizing wickedness as a creative tool may also enable organizational development of a generative mindset to better adapt to our rapidly changing future.
Novel hybrid wick heat pipes are developed to operate against gravity on planetary surfaces, operate in space carrying power over long distances and act as thermosyphons on the planetary surface for Lunar and Martian landers and rovers. These hybrid heat pipes will be capable of operating at the higher heat flux requirements expected in NASA's future spacecraft and on the next generation of polar rovers and equatorial landers. In addition, the sintered evaporator wicks mitigate the start-up problems in vertical gravity aided heat pipes because of large number of nucleation sites in wicks which will allow easy boiling initiation. ACT, NASA Marshall Space Flight Center, and NASA Johnson Space Center, are working together on the Advanced Passive Thermal experiment (APTx) to test and validate the operation of a hybrid wick VCHP with warm reservoir and HiK"TM" plates in microgravity environment on the ISS.
A common problem occurs when refrigerant fluids wick inside the insulation of thermocouple wires through a compressor's casing feedthrough and then leak into the adjacent disconnect box outside the casing. Leaking fluids create an unfavorable situation inside the disconnect box and may contaminate the fluids. To address this problem, NASA Lewis Research Center s Manufacturing Engineering Division developed a customized hermetic feedthrough for a bank of Worthington compressors. In these compressors, bearing temperatures are measured by internal thermocouples embedded in bearings located inside the compressor casings. The thermocouple wires need to be routed outside the casing and read at another location. These wires are short and are terminated to a disconnect strip inside the casing. The bearings operate at about 170 F, but because the casing is filled with R12 refrigerant oil, the casing has a maximum temperature of about 100 F. The operating conditions of these compressors permit the use of an epoxy that is compatible with the R12 fluid. The desired finished product is a stainless steel tube that has been filled solid with epoxy after thermocouple wires bonded and sealed by epoxy have been inserted through its length. Shrink tubing extends from both ends of the tube. The process that was developed to isolate the thermocouple wires from the R12 fluid follows. For this application, use an 8-in.-long piece of 0.500-in. 304 stainless steel tube with six pairs of 24-gauge stranded, PTFE-insulated (polytetrafluoroethylene) type "T" thermocouple wires for each feedthrough. Use shrink tubing to strain relief the insulated wires at their exit from the stainless steel tube. Cut the wire to length and identify the location of the stainless steel tube sleeve with masking tape. Then, remove the outer insulation from a 2-in. section of wire that will be inside the tube, and carefully strip to bare wire a 1-in. section in the middle of the section with the outer insulation removed. For an effective seal, the epoxy must penetrate between the strands when stranded conductors are used. Make the seal with epoxy bond on the bare wire. The bare wire must be encapsulated with a thin layer of the epoxy that leaves only a very low profile. These encapsulated wires must cure before the assembly can be continued. Then, inspect the cured wires for complete encapsulation before going to the next step. Insert the wires in the stainless steel tube and orient them so that the epoxied stripped sections are staggered within the tube; then, apply shrink tubing to one end of the cleaned wires, positioning it inside the edge of the tube. The small gaps between the wires on the other end will be used to inject the epoxy into the tube. Let the epoxy cure inside the tube, free of any voids. Then, continue to fill the tube until the entire 8-in. length is nearly filled, allowing room for the other strain-relieving shrink tubing. Since this first design, the process has been adjusted to fit many needs and situations. Customized feedthroughs have been assembled from various wire types, wire gauges, and/or stainless steel tube passages. The fittings selected to mount these feedthroughs allow their use in other areas, such as pressure or vacuum systems.
A computer program for numerical solution of differential equations that describe heat pipes with graded-porosity fibrous wicks is discussed. A mathematical problem is provided with a summary of the input and output steps used to solve it. The program is also applied to the analysis of a typical heat pipe.
The choice of chemically vapor deposited (CVD) tungsten as material for the heat pipes is based on studies reported by Busse et al. (1970). Aspects of pipe construction are discussed together with wick construction, and heat pipe operation. An auxiliary heater was used to overcome problems during the start of operation in the case of a thermally loaded pipe. Two heat pipes were operated at temperatures up to 1850 K. Annular and channeled wicks were investigated. The design of a cross flow heat exchanger is presented together with the design of a reactor heat pipe life test station.
Continuum and rarefied vapor flows co-exist along the heat pipe length for most of the startup period. A two-region model is proposed in which the vapor flow in the continuum region is modeled by the compressible Navier-Stokes equations, and the vapor flow in the rarefied region is simulated by a self-diffusion model. The two vapor regions are linked with appropriate boundary conditions, and heat pipe wail, wick, and vapor flow are solved as a conjugate problem. The numerical solutions for the entire heat pipe startup process from the frozen state are compared with the corresponding experimental data with good agreement.
Turbofan STOL transport application to air transportation congestion, discussing conditioning landing field length, navigational/control problems and jet flap concepts
Important issues: Mass gauging; Stability dynamics of disconnected capillary surfaces; Slow capillary driven flow (i.e. wicking); Long-term material property evolution in micro-g; Dumping problem with freezing of dump lines.
Results are presented for a comprehensive test program directed toward determining the physical and thermal performance of two flexible cryogenic heat pipes that can provide a highly efficient thermal link between a detector and a space radiator or other cooling system in spacecraft applications. A 100-200 K high-power heat pipe is tested with methane at 100-140 K while a 15-100 K low-temperature pipe is designed for operation with nitrogen and oxygen and is optimized for oxygen in the range 75-90 K. Parametric performance and design tradeoff studies are carried out to determine the optimum geometry and materials for the container and wicking systems. A spiral multiwrap wick in conjunction with braided bellows appears to be a workable solution to the problem of developing highly flexible heat transport devices for cryogenic applications.
The lubrication of rolling element bearings is surveyed. Emphasis is on the critical design aspects related to speed, temperature, and ambient pressure environment. Types of lubrication including grease, jets, mist, wick, and through the race are discussed. The historical development, present state of technology, and the future problems of rolling element bearing lubrication are discussed.
This paper presents an overview of the Cryogenic Test Bed (CTB) experiments including experiment results, integration techniques used, and lessons learned during integration, test and flight phases of the Cryogenic Heat Pipe Flight Experiment (STS-53) and the Cryogenic Two Phase Flight Experiment (OAST-2, STS-62). We will also discuss the Cryogenic Flexible Diode Heat Pipe (CRYOFD) experiment which will fly in the 1996/97 time frame and the fourth flight of the CTB which will fly in the 1997/98 time frame. The two missions tested two oxygen axially grooved heat pipes, a nitrogen fibrous wick heat pipe and a 2-methylpentane phase change material thermal storage unit. Techniques were found for solving problems with vibration from the cryo-collers transmitted through the compressors and the cold heads, and mounting the heat pipe without introducing parasitic heat leaks. A thermally conductive interface material was selected that would meet the requirements and perform over the temperature range of 55 to 300 K. Problems are discussed with the bi-metallic thermostats used for heater circuit protection and the S-Glass suspension straps originally used to secure the BETSU PCM in the CRYOTP mission. Flight results will be compared to 1-g test results and differences will be discussed.
A collector/heat pipe cooled, externally configured (heated) thermionic diode module was designed for use in a laboratory test to demonstrate the applicability of this concept as the fuel element/converter module of an in-core thermionic electric power source. During the course of the program, this module evolved from a simple experimental mock-up into an advanced unit which was more reactor prototypical. Detailed analysis of all diode components led to their engineering design, fabrication, and assembly, with the exception of the collector/heat pipe. While several designs of high power annular wicked heat pipes were fabricated and tested, each exhibited unexpected performance difficulties. It was concluded that the basic cause of these problems was the formation of crud which interfered with the liquid flow in the annular passage of the evaporator region.
This paper is a broad survey of the lubrication of rolling-element bearings. Emphasis is on the critical design aspects related to speed, temperature, and ambient pressure environment. Types of lubrication including grease, jets, mist, wick, and through-the-race are discussed. The paper covers the historical development, present state of technology, and the future problems of rolling-element bearing lubrication.