entrance pupil points of interest. These field or aperture, depending on the allo- nates of interest are obtained for every are chosen to be the edge of each space, cations. Once this minimum set of coor- plane of the propagation, the data is for- so that these rays produce the bounding dinates on the pupil and field is ob- matted into an xyz file suitable for FRED volume for the beam. The x and y global tained, a new set of rays is generated optical analysis software to import and coordinate data is collected on the sur- between the field plane and aperture create a STEP file of the data. This re- face planes of interest, typically an image plane (or vice-versa). sults in a spiral-like structure that is easily of the field and entrance pupil internal These rays are then evaluated at imported by mechanical CAD users of the optical system. This x and y coor- planes between the aperture and field, at can then use an automated algorithm to dinate data is then evaluated using a a desired number of steps perceived nec- wrap a skin around it and create a solid convex hull algorithm, which removes essary to build up the bounding volume that represents the beam. any internal points, which are unneces- or cone shape. At each plane, the ray co- This work was done by Joseph Howard and sary to produce the bounding volume of ordinates are again evaluated using the Lenward Seals of Goddard Space Flight Center. interest. At this point, tolerances can be convex hull algorithm to reduce the data Further information is contained in a TSP applied to the size of either the to a minimal set. When all of the coordi- (see page 1). GSC-16176-1

High-Performance, Multi-Node File Copies and Checksums for Clustered File Systems Ames Research Center, Moffett Field, California Modern parallel file systems achieve performance of clustered file systems. Mcp and msum provide significant per- high performance using a variety of Mcp and msum are drop-in replace- formance improvements over standard techniques, such as striping files across ments for the standard cp and md5sum and md5sum using multiple types of par- multiple disks to increase aggregate I/O programs that utilize multiple types of allelism and other optimizations. The bandwidth and spreading disks across parallelism and other optimizations to total speed-ups from all improvements are multiple servers to increase aggregate achieve maximum copy and checksum significant. Mcp improves cp perform- interconnect bandwidth. To achieve performance on clustered file systems. ance over 27×, msum improves md5sum peak performance from such systems, it Multi-threading is used to ensure that performance almost 19×, and the combi- is typically necessary to utilize multiple nodes are kept as busy as possible. nation of mcp and msum improves veri- concurrent readers/writers from multi- Read/write parallelism allows individual fied copies via cp and md5sum by almost ple systems to overcome various single- operations of a single copy to be over- 22×. These improvements come in the system limitations, such as number of lapped using asynchronous I/O. Multi- form of drop-in replacements for cp and processors and network bandwidth. The node cooperation allows different nodes md5sum, so are easily used and are avail- standard cp and md5sum tools of GNU to take part in the same copy/checksum. able for download as open source soft- coreutils found on every modern -file processing allows multiple ware at http://mutil.sourceforge.net. Unix/Linux system, however, utilize a threads to operate concurrently on the This work was done by Paul Z. Kolano and single execution thread on a single CPU same file. Finally, hash trees allow inher- Robert B. Ciotti of Ames Research Center. Fur- core of a single system, and hence can- ently serial checksums to be performed ther information is contained in a TSP (see not take full advantage of the increased in parallel. page 1). ARC-16494-1

Stiffness and Damping Coefficient Estimation of Compliant Surface Gas Bearings for Oil-Free Turbomachinery Initial applications include design of turbochargers, blowers, compressors, pumps, and turbine engines. John H. Glenn Research Center, Cleveland, Ohio

Foil gas bearings are a key technology valuable tool in system development. of sheet-metal foil layers from which they in many commercial and emerging oil- The current work extends this tool con- derive their name. They are compliant free turbomachinery systems. These cept to include rules for stiffness and bearings that offer high-speed rotor sup- bearings are nonlinear and have been damping coefficient estimation. It is ex- port while accommodating shaft mis- difficult to analytically model in terms of pected that these rules will further accel- alignment and distortion often encoun- performance characteristics such as load erate the development and deployment tered in turbomachinery. Lightly loaded, capacity, power loss, stiffness, and damp- of advanced oil-free machines operating low-temperature foil gas bearings are ing. Previous investigations led to an em- on foil gas bearings. commodities that predominate in the pirically derived method to estimate Foil gas bearings are self-acting hydro- rotor support for aircraft air cycle ma- load capacity. This method has been a dynamic bearings comprised of a series chines (ACMs). More highly loaded foil

32 NASA Tech Briefs, June 2012 bearings operating at high temperatures Methods to estimate critical stiffness that yield stiffness, damping, and load are an emerging technology making and damping parameters, however, do capacity values as a function of bearing commercial inroads into several markets not currently exist. The purpose of the size, design, and operating speed. With including aircraft auxiliary power units methods put forth in this work is to estab- these models, one can easily determine (APUs), microturbines, gas compressors lish simple tools capable of estimating foil the feasibility of building a foil bearing and blowers, and turbochargers. bearing stiffness and damping coeffi- supported machine without incurring The general trend for foil bearings cients suitable for oil-free rotor support the expense of early experimental work. since their initial development over five design work. This has been accomplished The models presented represent the decades ago is application to larger and by first coalescing all available empirical only known and verified methods to pre- more complex rotor systems. As this pro- data on foil bearing performance that dict conveniently foil bearing perform- liferation occurs, more practitioners will has been generated in the author’s own ance properties. become actively involved with new ma- laboratories, and by researchers working This work was done by Christopher Della- chine development using foil bearings. in university, government, and industrial Corte of Glenn Research Center. Further infor- Thus, there is a great need for applica- laboratories. This information is exam- mation is contained in a TSP (see page 1). tion guidelines to establish the feasibility ined and combined, then used to de- Inquiries concerning rights for the commer- of proposed rotor systems and to iden- velop ROT for foil bearing stiffness and cial use of this invention should be addressed tify existing machines that are good can- damping. These ROTs can then be com- to NASA Glenn Research Center, Innovative didates for foil bearing use. Specifically, bined with existing rules for load capacity Partnerships Office, Attn: Steven Fedor, Mail a method is needed to estimate foil bear- to obtain credible feasibility assessments Stop 4–8, 21000 Brookpark Road, Cleve- ing stiffness and damping behavior in for proposed oil-free rotor systems. land, Ohio 44135. Refer to LEW-18755-1. order to foster advanced oil-free rotating The effort described has resulted in machine development. algebraic models for foil gas bearings

Sampling and Reconstruction of the Pupil and Electric Field for Phase Retrieval Goddard Space Flight Center, Greenbelt, Maryland

This technology is based on sampling analytical results are given using a 1-d 1

Space Operations Learning Center Facebook Application This app uses the latest networking technology to inspire young audiences to be interested in math, science, and engineering. Goddard Space Flight Center, Greenbelt, Maryland

The proposed Space Operations learning with a fun game and social envi- and levels increase. A player can interact Learning Center (SOLC) Facebook mo- ronment. The mission of the game is to with other players using multiplayer Face- dule, initially code-named “Spaceville,” build a scientific outpost on the Moon or book functionality. As a result, a player can is intended to be an educational online Mars and expand the colony. Game activi- discover unexpected treasures through sci- game utilizing the latest social network- ties include collecting resources, trading entific missions, engineering, and working ing technology to reach a broad audi- resources, completing simple science ex- with others. ence base and inspire young audiences periments, and building architectures such The player creates his/her own avatar to be interested in math, science, and as laboratories, habitats, greenhouses, ma- with his/her selection of its unique ap- engineering. chine shops, etc. The player is awarded pearance, and names the character. The Spaceville will be a Facebook applica- with points and achievement levels. The player controls the avatar to perform ac- tion/game with the goal of combining player’s ability increases as his/her points tivities such as collecting oxygen mole-

NASA Tech Briefs, June 2012 33