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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.

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At least 631 records · Page 35

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NASA NTRS1990

Flight control issues of the next generation space transportation launch vehicles

Some of the issues that affect the flight control and guidance system designs for vertical-takeoff and horizontal-takeoff vehicles were investigated. A two-stage all-rocket vehicle was used to represent the vertical-takeoff system and a generic aerospace plane concept to represent the horizontal-takeoff vehicle. Two flight control issues for the vertical-takeoff rocket were uncovered. The first was the large gimbal angle range required for pitch trim when using parallel mated vehicles. The second was control during staging. Two issues were also identified for the air-breathing vehicle. The first is that the drag losses due to aerodynamic trim are a significant fraction of the total ideal velocity required to achieve orbit. The second issue is that since the vehicle flies at high dynamic pressure for most of the ascent, the guidance system design will be more difficult to ensure accurate insertion than that for the vertical-takeoff rocket system.

Powell, Richard W.↗

NASA NTRS1989

COLD-SAT - An orbital cryogenic hydrogen technology experiment

The COLD-SAT spacecraft will perform subcritical liquid hydrogen storage and transfer experiments under low-gravity conditions to provide engineering data for future space transportation missions. Consisting of an experiment module mated to a spacecraft bus, COLD-SAT will be placed in an initial 460 km circular orbit by an Atlas I commercial launch vehicle. After deployment, the three-axis-controlled spacecraft bus will provide electric power, experiment control and data management, communications, and attitude control along with propulsive acceleration levels ranging from 10 (-6) to 10(-4) g. These accelerations are an important aspect of some of the experiments, as it is desired to know the effects that low gravity levels might have on the heat and mass transfer processes involved. The experiment module will contain the three liquid hydrogen tanks, valves, pressurization equipment, and instrumentation. At launch all the hydrogen will be in the largest tank, which has helium-purged MLI and is loaded and topped off by the hydrogen tanking system used for the Centaur upper stage of the Atlas. The two smaller tanks will be utilized in orbit for performing some of the experiments. The experiments are grouped into two classes on the basis of their priority, and include six regarded as enabling technology and nine regarded as enhancing technology.

Schuster, J. R.↗

NASA NTRS1990

Electromechanical propellant control system actuator

New control mechanism technologies are currently being sought to provide alternatives to hydraulic actuation systems. The Propulsion Laboratory at Marshall Space Flight Center (MSFC) is involved in the development of electromechanical actuators (EMA's) for this purpose. Through this effort, an in-house designed electromechanical propellant valve actuator has been assembled and is presently being evaluated. This evaluation will allow performance comparisons between EMA and hydraulics systems. The in-house design consists of the following hardware: a three-phase brushless motor, a harmonic drive, and an output spline which will mate with current Space Shuttle Main Engine (SSME) propellant control valves. A resolver and associated electronics supply position feedback for the EMA. System control is provided by a solid-state electronic controller and power supply. Frequency response testing has been performed with further testing planned as hardware and test facilities become available.

Myers, W. Neill↗

NASA NTRS1990

Analysis and design of helium-buffered face seals for the SSME high-pressure oxygen turbopump

One form of a gas-buffered seal consists of two opposed fluid-film face seals, each mating against a single collar. The buffer fluid is introduced at the OD and flows through the radial clearances of each seal to opposite and separate environments at the IDs. This arrangement was investigated for the helium buffer seals applied to the oxidizer pump of the Space Shuttle Main Engine (SSME). A variety of face configurations were considered, and the self-energized-hydrostatic and spiral-groove geometries were selected for detailed evaluation. Fluid-film performance, dynamic response, and thermoelastic distortions were determined. Because of very high temperature gradients, distortions of the turbine-side seal ring were excessive. Otherwise, performance was excellent in all respects.

Shapiro, Wilbur↗

NASA NTRS1990

Thermographic inspection of solid-fuel rocket booster field joint components

Thermographic nondestructive evaluation techniques were investigated for possible application on Space Shuttle solid rocket booster field joint hardware. This investigation included evaluation of the clevis and tang mating surfaces for scratches and measurement of grease film thickness. The field joint insulation system was inspected for voids and disbonds.

Thompson, Karen G.↗

NASA NTRS1991

Thin, Lightweight Solar Cell

Improved design for thin, lightweight solar photovoltaic cells with front contacts reduces degradation of electrical output under exposure to energetic charged particles (protons and electrons). Increases ability of cells to maintain structural integrity under exposure to ultraviolet radiation by eliminating ultraviolet-degradable adhesives used to retain cover glasses. Interdigitated front contacts and front junctions formed on semiconductor substrate. Mating contacts formed on back surface of cover glass. Cover glass and substrate electrostatically bonded together.

Brandhorst, Henry W., Jr.↗

NASA NTRS1991

Fast-Acting Rubber-To-Coated-Aluminum Adhesive

Cyanoacrylate adhesive used to join rubber to coated aluminum easier to apply and more effective. One-part material applied in single coat to aluminum treated previously with epoxy primer and top coat. Parts mated as soon as adhesive applied; no drying necessary. Sets in 5 minutes. Optionally, accelerator brushed onto aluminum to reduce setting time to 30 seconds. Clamping parts together unnecessary. Adhesive comes in four formulations, all based on ethyl cyanoacrylate with various amounts of ethylene copolymer rubber, poly(methyl methacrylate), silicon dioxide, hydroquinone, and phthalic anhydride.

Comer, Dawn A.↗

NASA NTRS1991

Hand Broaching Tool For Use In Confined Areas

Broaching tool cuts keyslots in tapped holes. With exceptionally slim outer body, well suited for work in areas of limited accessibility, particularly when features of workpiece create obstructions. Threaded sections on inner and outer bodies mate. After inner body used to broach keyways in hole in workpiece, turning outer body by its handle forces bearing surface against workpiece and pulls inner body tip out of hole. Reduces time for broaching holes from 4 h to 1 h. Blade replaced only twice per circle.

Beach, Arthur A.↗

NASA NTRS1991

Adjustable Pitot Probe

Probe readily positionable in core of uniform flow in hypersonic wind tunnel. Formed of pair of mating cylindrical housings: transducer housing and pitot-tube housing. Pitot tube supported by adjustable wedge fairing attached to top of pitot-tube housing with semicircular foot. Probe adjusted both radially and circumferentially. In addition, pressure-sensing transducer cooled internally by water or other cooling fluid passing through annulus of cooling system.

Ashby, George C., Jr.↗

NASA NTRS1991

Heat-Transfer Coupling For Heat Pipes

Proposed welded heat-transfer coupling joins set of heat pipes to thermoelectric converter. Design avoids difficult brazing operation. Includes pair of mating flanged cups. Upper cup integral part of housing of thermoelectric converter, while lower cup integral part of plate supporting filled heat pipes. Heat pipes prefilled. Heat of welding applied around periphery of coupling, far enough from heat pipes so it would not degrade working fluid or create excessive vapor pressure in the pipes.

Nesmith, Bill J.↗

NASA NTRS1991

Quick-Connect/Disconnect Joint For Truss Structures

Simple connector used for temporary structures and pipes. Truss connector joins and aligns structural members. Consists of two sections, one flanged and other with mating internal groove. When flanged half inserted in groove, moves lever of trigger mechanism upward. Cone then shoots into grooved half. Attached without tools in less than 2 seconds and taken apart just as quickly and easily. Developed for assembling structures in outer space, also useful for temporary terrestrial structures like scaffolds and portable bleachers. With modifications, used to join sections of pipelines carrying liquids or gases.

Sprague, Benny B.↗

NASA NTRS1991

Bidirectional Drive-And-Brake Mechanism

Vehicle that crawls along monorail combines features of both bicycle and railroad handcar. Bidirectional drive-and-brake mechanism includes selectable-pawl-and-ratchet overrunning clutch (drive mechanism) and mating stationary and rotating conical surfaces pressing against each other (brake mechanism). Operates similarly to bicycle drive-and-brake mechanism except limits rotation of sprocket in both directions and brakes at both limits. Conceived for use by astronaut traveling along structure in outer space, concept also applied on Earth to make very small railraod handcars or crawling vehicles for use on large structures, in pipelines under construction, or underwater.

Swan, Scott A.↗

NASA NTRS1989

Numerical aerodynamic simulation of the space shuttle ascent environment

After the STS 51-L accident, an extensive review of the Space Shuttle Orbiter's ascent aerodynamic loads uncovered several questionable areas that required further analysis. The insight gained by comparing the Shuttle ascent CFD numerical simulations, obtained by the NASA Ames Space Shuttle Flow Simulation Group, to the current IVBC-3 aerodynamic loads database was instrumental in resolving uncertainties on the Orbiter payload bay doors and fuselage. Initial confidence in the numerical simulations was gained by comparing them with the limited flight data that had been obtained during the Orbiter Flight Test (OFT) program. Current CFD results exist for Mach numbers 0.6, 0.9, 1.05, 1.55, 2.0, and 2.5. Since the pre STS-1 wind tunnel test program (IA-105) often yields considerable differences when compared to STS-5 flight data, the M(sub infinity) = 1.05 transonic case is the most investigated. The IA308 mated-vehicle hot gas plume wind tunnel test, recently completed at AEDC 16T (transonic) and Lewis (hypersonic), is also used to compare with the computation where applicable.

Slotnick, Jeff P.↗

NASA NTRS1989

Conjugate (solid/fluid) computational fluid dynamics analysis of the space shuttle solid rocket motor nozzle/case and case field joints

Three-dimensional, conjugate (solid/fluid) heat transfer analyses of new designs of the Solid Rocket Motor (SRM) nozzle/case and case field joints are described. The main focus was to predict the consequences of multiple rips (or debonds) in the ambient cure adhesive packed between the nozzle/case joint surfaces and the bond line between the mating field joint surfaces. The models calculate the transient temperature responses of the various materials neighboring postulated flow/leakpaths into, past, and out from the nozzle/case primary O-ring cavity and case field capture O-ring cavity. These results were used to assess if the design was failsafe (i.e., no potential O-ring erosion) and reusable (i.e., no excessive steel temperatures). The models are adaptions and extensions of the general purpose PHOENICS fluid dynamics code. A non-orthogonal coordinate system was employed and 11,592 control cells for the nozzle/case and 20,088 for the case field joints are used with non-uniform distribution. Physical properties of both fluid and solids are temperature dependent. A number of parametric studies were run for both joints with results showing temperature limits for reuse for the steel case on the nozzle joint being exceeded while the steel case temperatures for the field joint were not. O-ring temperatures for the nozzle joint predicted erosion while for the field joint they did not.

Doran, D.↗

NASA NTRS1990

System for connecting fluid couplings

A system for mating fluid transfer couplings is constructed having a male connector which is provided with a pair of opposed rollers mounted to an exterior region thereof. A male half of a fluid transfer coupling is rotatably supported in an opening in an end of the connector and is equipped with an outwardly extending forward portion. The forward portion locks into an engagement and locking region of a female half of the fluid transfer coupling, with female half being rotatably supported in a receptacle. The receptacle has an opening aligned with locking region, with this opening having a pair of concentric, annularly disposed ramps extending around an interior portion of opening. These ramps are inclined toward the interior of the receptacle and are provided with slots through which rollers of the connector pass. After the connector is inserted into the receptacle (engaging forward portion into engagement region), relative rotation between the connector and receptacle causes the rollers to traverse ramps until the rollers abut and are gripped by retainers. This axially forces the forward portion into locked, sealed engagement with the engagement region.

Cody, Joseph C.↗

NASA NTRS1991

Modeling a ball screw/ball nut in substructuring

In the particular NASTRAN application discussed here, a nut was attached to a stationary structure. The object of the analysis was to determine the vibration characteristics of the whole structure for various configurations; i.e., the evaluation of the mode shapes and frequencies when parts were moved to different mating positions. Details of the analysis are given.

Butler, Thomas G.↗

NASA NTRS1991

Contact stresses in gear teeth: A new method of analysis

A new, innovative procedure called point load superposition for determining the contact stresses in mating gear teeth. It is believed that this procedure will greatly extend both the range of applicability and the accuracy of gear contact stress analysis. Point load superposition is based upon fundamental solutions from the theory of elasticity. It is an iterative numerical procedure which has distinct advantages over the classical Hertz method, the finite element method, and over existing applications with the boundary element method. Specifically, friction and sliding effects, which are either excluded from or difficult to study with the classical methods, are routinely handled with the new procedure. Presented here are the basic theory and the algorithms. Several examples are given. Results are consistent with those of the classical theories. Applications to spur gears are discussed.

Somprakit, Paisan↗

NASA NTRS1991

Dual diaphragm tank with telltale drain

A fluid storage and expulsion system comprising a tank with an internal flexible diaphragm assembly of dual diaphragms in back-to-back relationship, at least one of which is provided with a patterned surface having fine edges such that the diaphragms are in contact along said edges without mating contact of surface areas to thereby form fluid channels which extend outwardly to the peripheral edges of the diaphragms is described. The interior wall of the tank at the juncture of tank sections is formed with a circumferential annular recess comprising an outer annular recess portion which forms a fluid collection chamber and an inner annular recess portion which accommodates the peripheral edge portions of the diaphragms and a sealing ring in clamped sealing relation therebetween. The sealing ring is perforated with radially extending passages which allow any fluid leaking or diffusing past a diaphragm to flow through the fluid channels between the diaphragms to the fluid collection chamber. Ports connectable to pressure fittings are provided in the tank sections for admission of fluids to opposite sides of the diaphragm assembly. A drain passage through the tank wall to the fluid collection chamber permits detection, analysis and removal of fluids in the collection chamber.

Tuthill, Wallace C., Jr.↗