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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 469 records · Page 26
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Digital adaptive model following flight control

Simple mechanical linkages are often unable to cope with the many control problems associated with high performance aircraft maneuvering over a wide flight envelope. One procedure for retaining uniform handling qualities over such an envelope is to implement a digital adaptive controller. Towards such an implementation an explicit adaptive controller, which makes direct use of online parameter identification, has been developed and applied to the linearized equations of motion for a typical fighter aircraft. The system is composed of an online weighted least squares identifier, a Kalman state filter, and a single stage real model following control law. The corresponding control gains are readily adjustable in accordance with parameter changes to ensure asymptotic stability if the conditions for perfect model following are satisfied and stability in the sense of boundedness otherwise.

Alag, G. S.↗
NASA NTRS1974

The Representative Shuttle Environmental Control System

The Representative Shuttle Environmental Control System (RSECS) program was conceived to provide NASA with a prototype system representative of the Shuttle Environmental Control System (ECS). Discussed are the RSECS program objectives, predicated on updating and adding to the early system as required to retain its usefulness during the Shuttle ECS development and qualification effort. Ultimately, RSECS will be replaced with a flight-designed system using either refurbished development or qualification equipment to provide NASA with a flight simulation capability during the Shuttle missions. The RSECS air revitalization subsystem and the waste management support subsystem are being tested. A water coolant subsystem and a freon coolant subsystem are in the development and planning phases.

Brose, H. F.↗
NASA NTRS1973

Reentry guidance for Space Shuttle

An explicit guidance scheme is outlined which provides the appropriate energy management in order for the shuttle orbiter to reach any location within the required footprint. Considering the orbiter as entering the earth's atmosphere, expressions for the downrange, crossrange, and the time of the termination of the entry phase as functions of the control variables are developed. Performing an order-of-magnitude analysis of the terms in these expressions, only dominant terms are retained. Analytical expressions for the elements of the sensitivity matrix which represents the partial derivatives of the desired range with respect to control variables are formulated. Using the Gauss-Jordan inversion technique, the required change in guidance commands as a function of the deviations in the downrange and crossrange are explicitly computed.

Causey, W.↗
NASA NTRS1974

Maneuver strategies for the extended Pioneer 11 Jupiter/Saturn mission

The Jupiter-bound Pioneer 11 spacecraft was launched in April 1973, eight months before the Jupiter encounter of the front-running spacecraft, Pioneer 10. Near-Earth maneuvers placed Pioneer 11 on an interim flight path designed to retain a later retargeting capability to repeat the Pioneer 10 flyby geometry or encounter a wide variety of alternate Jupiter aimpoints, including one resulting in an extended five-year trajectory to Saturn. Pioneer 11 was retargeted to this aimpoint in April 1974, subsequent to the successful Pioneer 10 encounter in December 1973. This paper presents the retargeting and trimming maneuver strategies necessary to assure a productive Pioneer 11 Jupiter encounter in early December 1974, followed by a Saturn encounter in late 1979.

Frauenholz, R. B.↗
NASA NTRS1974

Analysis and experimental studies of the control of hang gliders

A theoretical analysis of the longitudinal and lateral characteristics of hang gliders in straight flight, pullups, and turns is presented. Some examples of the characteristics of a straight-wing configuration and a Rogallo-wing configuration are given. A means for improving the control of hang gliders while retaining the same basic control feel is proposed.

Phillips, W. H.↗
NASA NTRS1974

Cosmic-ray streaming perpendicular to the mean magnetic field

Starting from a quasi-linear approximation for the ensemble-averaged particle distribution function in a random magnetic field, the complete diffusion tensor is derived. This is done by assuming a simple form for the ensemble-averaged distribution function, explicitly retaining all components of the streaming flux. This derivation obtains the antisymmetric terms in a natural manner. The necessary dropping of higher-order terms gives a criterion for the lower-energy limit of validity of the perpendicular and antisymmetric diffusion coefficients. The limit for the assumed distribution function is about 0.8 GV rigidity in the interplanetary field near 1 AU.

Forman, M. A.↗
NASA NTRS1952

Experimental Investigation of Average Heat-Transfer and Friction Coefficients for Air Flowing in Circular Tubes Having Square-Thread-Type Roughness

An investigation of forced-convection heat transfer and associated pressure drops was conducted with air flowing through electrically heated Inconel tubes having various degrees of square-thread-type roughness, an inside diameter of 1/2 inch, and a length of 24 inches. were obtained for tubes having conventional roughness ratios (height of thread/radius of tube) of 0 (smooth tube), 0.016, 0.025, and 0.037 over ranges of bulk Reynolds numbers up to 350,000, average inside-tube-wall temperatures up to 1950deg R, and heat-flux densities up to 115,000 Btu per hour per square foot. Data The experimental data showed that both heat transfer and friction increased with increase in surface roughness, becoming more pronounced with increase in Reynolds number; for a given roughness, both heat transfer and friction were also influenced by the tube wall-to-bulk temperature ratio. Good correlation of the heat-transfer data for all the tubes investigated was obtained by use of a modification of the conventional Nusselt correlation parameters wherein the mass velocity in the Reynolds number was replaced by the product of air density evaluated at the average film temperature and the so-called friction velocity; in addition, the physical properties of air were evaluated at the average film temperature. The isothermal friction data for the rough tubes, when plotted in the conventional manner, resulted in curves similar to those obtained by other investigators; that is, the curve for a given roughness breaks away from the Blasius line (representing turbulent flow in smooth tubes) at some value of Reynolds number, which decreases with increase in surface roughness, and then becomes a horizontal line (friction coefficient independent of Reynolds number). A comparison of the friction data for the rough tubes used herein indicated that the conventional roughness ratio is not an adequate measure of relative roughness for tubes having a square-thread-type element. The present data, as well as those of other investigators, were used to isolate the influence of ratios of thread height to width, thread spacing to width, and the conventional roughness ratio on the friction coefficient. A fair correlation of the friction data was obtained for each tube with heat addition when the friction coefficient and Reynolds number were defined on the basis of film properties; however, the data for each tube retained the curve characteristic of that particular roughness. The friction data for all the rough tubes could be represented by a single line for the complete turbulence region by incorporating a roughness parameter in the film correlation. No correlation was obtained for the region of incomplete turbulence.

Sams, E. W.↗
NASA NTRS1975

Low-cost, portable fire hose tester

Availability of pumping unit permits scheduling and performing required periodic hose tests in proper manner while retaining full fire equipment readiness. Use of pumping unit preserves operating life and capability of pumper truck.

Jocke, R. F.↗
NASA NTRS1975

High strength forgeable tantalum base alloy

Increasing tungsten content of tantalum base alloy to 12-15% level will improve high temperature creep properties of existing tantalum base alloys while retaining their excellent fabrication and welding characteristics.

Buckman, R. W., Jr.↗
NASA NTRS1975

A nondispersive infrared analyzer

Apparatus retains all advantages of prior nondispersive infrared analysis systems and provides significantly more innumity to type of errors that may be introduced by geometric changes in analysis system. Technique also permits construction of instruments of lower weight, smaller volume, and smaller power consumption.

Dimeff, J.↗
NASA NTRS1975

Method of attaching insulation tiles

Felt pads attached underneath tiles add very little weight and retain flexibility at low temperatures. Very thin layer of room-temperature vulcanizing silicone adhesive is applied to tile. Then felt pad is attached to adhesive. Finally, tile-felt combination is attached to metal surface by means of similar adhesive layer.

Leger, L. J.↗
NASA NTRS1975

Quick-change absorption column

Column has end caps held in place by springs; prefilled packs of absorbent can be exchanged quickly. Both ends of metal or plastic body tube of size which can hold adequate amount of absorbent are machined to provide seat for perforated plate and groove for its spring retainer ring.

Mcewen, G. N., Jr.↗
NASA NTRS1975

Simple computer method provides contours for radiological images

Computer is provided with information concerning boundaries in total image. Gradient of each point in digitized image is calculated with aid of threshold technique; then there is invoked set of algorithms designed to reduce number of gradient elements and to retain only major ones for definition of contour.

Newell, J. D.↗
NASA NTRS1975

Liquid ethylene-propylene copolymers

Oligomers are prepared by heating solid ethylene-propylene rubber in container that retains solid and permits liquid product to flow out as it is formed. Molecular weight and viscosity of liquids can be predetermined by process temperature. Copolymers have low viscosity for given molecular weight.

Rhein, R. A.↗
NASA NTRS1974

Fabrication of liquid-rocket thrust chambers by electroforming

Electroforming has proven to be an excellent fabrication method for building liquid rocket regeneratively cooled thrust chambers. NASA sponsored technology programs have investigated both common and advanced methods. Using common procedures, several cooled spool pieces and thrust chambers have been made and successfully tested. The designs were made possible through the versatility of the electroforming procedure, which is not limited to simple geometric shapes. An advanced method of electroforming was used to produce a wire-wrapped, composite, pressure-loaded electroformed structure, which greatly increased the strength of the structure while still retaining the advantages of electroforming.

Duscha, R. A.↗
NASA NTRS1974

The maxometer-dynamic and static tests

The ability to withstand extreme environmental conditions, such as the high flow velocities and extreme temperatures associated with the launch of aerospace vehicles, was considered in the developement of two maxometer models which are capable of measuring extremely high wind speeds (130 m/sec) and retaining a record of the peak speed over any given time period. The dynamic and static tests of these models are reported, along with pertinent results.

Camp, D. W.↗
NASA NTRS1973

Investigation of solidification in zero-gravity environment: M553 sphere forming experiment. Nickel-silver alloy evaluation

The processing of nickel-silver alloy specimens in space is discussed. Four specimens were melted only partially, while a fifth was melted completely and assumed after solidification a perfectly spherical shape. Growth of the solid was epitaxial on the unmelted material or on the retaining sting and occurred without undercooling. Solidification was dendritic in all cases with nonequilibrium silver particles forming monotectically between dendrite arms. Substantial loss of silver by evaporation took place. Evaporation of the silver within internal gas cavities on the melt was followed by surface condensation after completion of solidification and cooling, leading to a silver-rich lining in these cavities. The material gave no microstructural evidence of any reduction in liquid convection.

Kattamis, T. Z.↗
NASA NTRS1974

Tough cryogenic alloys from the Fe-Mn and Fe-Mn-Cr systems

By adjusting composition, metastable gamma (austenite) and epsilon (hexagonal) martensite may be retained in Fe-Mn and Fe-Mn-Cr alloys and used to impact toughness through the TRIP mechanism. The resulting alloys have excellent toughness at cryogenic temperatures. The best alloys obtained to date are: Fe-20Mn, with sigma (sub y) = 79ksi and K sub IC = 275ksi square root of (in) at 77 K, and Fc-16Mn-8Cr, with sigma sub y = 85ksi and K sub IC = 72ksi square root of (in) at 77 K.

Schanfein, M. J.↗