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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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1938

Hydrodynamic and Aerodynamic Tests of Models of Floats for Single-float Seaplanes NACA Models 41-D, 41-E, 61-A, 73, and 73-A

Tests were made in the NACA tank and in the NACA 7 by 10 foot wind tunnel on two models of transverse step floats and three models of pointed step floats considered to be suitable for use with single float seaplanes. The object of the program was the reduction of water resistance and spray of single float seaplanes without reducing the angle of dead rise believed to be necessary for the satisfactory absorption of the shock loads. The results indicated that all the models have less resistance and spray than the model of the Mark V float and that the pointed step floats are somewhat superior to the transverse step floats in these respects. Models 41-D, 61-A, and 73 were tested by the general method over a wide range of loads and speeds. The results are presented in the form of curves and charts for use in design calculations.

Parkinson, J B↗
NASA NTRS1936

Tank Tests of Models of Floats for Single-float Seaplanes First Series.

Large models of the Mark V and Mark VI floats used for single float seaplanes (National Advisory Committee for Aeronautics (NACA) models 41-A and 41-B, respectively) were tested in the NACA tank to provide general test data for typical single floats and a basis for possible improvements of their form. The resistance of model 41-B was greater than that of model 41-A, either when free to trim or at the best trim angle for each. The resistance of model 35-B (a pointed step hull tested free to trim) was less than either of the models at the hump speed, greater at intermediate planing speeds, and less at the speeds and loads near get-away, although the spray was generally worse owing to the absence of transverse flare. The results of the fixed-trim tests of model 41-A were cross plotted to obtain data at the angle for zero trimming moment and at the best trim angle. The trims assumed by models 41-A and 41-B, when tested free to trim, were found to be excessive at the hump speed. The corresponding trim of model 35-B was found to be approximately 3 degrees lower because of the lower angle of afterbody keel used in this model, and the maximum hump resistance was 15 percent lower.

Parkinson, J B↗
NASA NTRS2000

Float processing of high-temperature complex silicate glasses and float baths used for same

A float glass process for production of high melting temperature glasses utilizes a binary metal alloy bath having the combined properties of a low melting point, low reactivity with oxygen, low vapor pressure, and minimal reactivity with the silicate glasses being formed. The metal alloy of the float medium is exothermic with a solvent metal that does not readily form an oxide. The vapor pressure of both components in the alloy is low enough to prevent deleterious vapor deposition, and there is minimal chemical and interdiffusive interaction of either component with silicate glasses under the float processing conditions. Alloys having the desired combination of properties include compositions in which gold, silver or copper is the solvent metal and silicon, germanium or tin is the solute, preferably in eutectic or near-eutectic compositions.

Cooper, Reid Franklin↗
NASA NTRS1931

On floats and float tests

The principal source of information on float resistance is the model test. In view of the insuperable difficulties opposing any attempt at theoretical treatment of the resistance problem, particularly at attitudes which tend toward satisfactory take-off, such as the transitory stage to planing, the towing test is and will remain the primary method for some time.

Seewald, Friedrich↗
NASA NTRS1938

The Aerodynamic Drag of Five Models of Side Floats N.A.C.A. Models 51-E, 51-F, 51-G, 51-H, 51-J

The drag of five models of side floats was measured in the N.A.C.A. 7- by 10-foot wind tunnel. The most promising method of reducing the drag of floats indicated by these tests is lowering the angle at which the floats are rigged. The addition of a step to a float does not always increase the drag in the flying range, floats with steps sometimes having lower drag than similar floats without steps. Making the bow chine no higher than necessary might result in a reduction in air drag because of the lower angle of pitch of the chines. Since side floats are used formally to obtain lateral stability when the seaplane is operating on the water at slow speeds or at rest, greater consideration can be given to factors affecting aerodynamic drag than is possible for other types of floats and hulls.

House, R O↗
NASA NTRS1933

Wind tunnel research comparing lateral control devices, particularly at high angles of attack XI : various floating tip ailerons on both rectangular and tapered wings

Discussed here are a series of systematic tests being conducted to compare different lateral control devices with particular reference to their effectiveness at high angles of attack. The present tests were made with six different forms of floating tip ailerons of symmetrical section. The tests showed the effect of the various ailerons on the general performance characteristics of the wing, and on the lateral controllability and stability characteristics. In addition, the hinge moments were measured for the most interesting cases. The results are compared with those for a rectangular wing with ordinary ailerons and also with those for a rectangular wing having full-chord floating tip ailerons. Practically all the floating tip ailerons gave satisfactory rolling moments at all angles of attack and at the same time gave no adverse yawing moments of appreciable magnitude. The general performance characteristics with the floating tip ailerons, however, were relatively poor, especially the rate of climb. None of the floating tip ailerons entirely eliminated the auto rotational moments at angles of attack above the stall, but all of them gave lower moments than a plain wing. Some of the floating ailerons fluttered if given sufficiently large deflection, but this could have been eliminated by moving the hinge axis of the ailerons forward. Considering all points including hinge moments, the floating tip ailerons on the wing with 5:1 taper are probably the best of those which were tested.

Weick, Fred E↗
NASA NTRS2016

Observations of Transient ISS Floating Potential Variations During High Voltage Solar Array Operations

The International Space Station (ISS) continues to be a world-class space research laboratory after over 15 years of operations, and it has proven to be a fantastic resource for observing spacecraft floating potential variations related to high voltage solar array operations in Low Earth Orbit (LEO). Measurements of the ionospheric electron density and temperature along the ISS orbit and variations in the ISS floating potential are obtained from the Floating Potential Measurement Unit (FPMU). In particular, rapid variations in ISS floating potential during solar array operations on time scales of tens of milliseconds can be recorded due to the 128 Hz sample rate of the Floating Potential Probe (FPP) pro- viding interesting insight into high voltage solar array interaction with the space plasma environment. Comparing the FPMU data with the ISS operations timeline and solar array data provides a means for correlating some of the more complex and interesting transient floating potential variations with mission operations. These complex variations are not reproduced by current models and require further study to understand the underlying physical processes. In this paper we present some of the floating potential transients observed over the past few years along with the relevant space environment parameters and solar array operations data.

Willis, Emily M.↗
NASA NTRS1933

Tank Tests of Two Floats for High-speed Seaplanes

At the request of the Bureau of Aeronautics, Navy Department, a study of the design of floats especially suitable for use on high-speed seaplanes was undertaken in the N.A.C.A. tank. This note give the results obtained in tests of one-quarter full-size models of two floats for high-speed seaplanes. One was a float similar to that used on the Macchi high-speed seaplane which competed in the 1926 Schneider Trophy races, and the other a float designed at the N.A.C.A. tank in an attempt to improve on the water performance of the Macchi float. The model of the latter showed considerably better water performance than the model of the Macchi float.

Bell, Joe W↗
NASA NTRS1947

An Analysis of the Full-Floating Journal Bearing

An analysis of the operating characteristics of a full-floating bearing - a bearing in which a floating sleeve is located between the journal and bearing surfaces - is presented together with charts - from which the performance of such bearings may be predicted. Examples are presented to illustrate the use of these charts and a limited number of experiments conducted upon a glass full-floating bearing to verify some results of the analysis are reported. The floating sleeve can operate over a wide range of speeds for a given shaft speed, the exact value depending principally upon the ratio of clearances and upon the ratio of radii of the bearing. Lower operating temperatures at high rotative speeds are to be expected by using a full-floating bearing. This lower operating temperature would be obtained at the expense of the load-carrying capacity of the bearing if, for comparison, the clearances remain the same in both bearings. A full-floating bearing having the same load capacity as a conventional journal bearing may be designed if decreased clearances are allowable.

Shaw, M.C.↗
NASA NTRS2011

Current-Sensitive Path Planning for an Underactuated Free-Floating Ocean Sensorweb

This work investigates multi-agent path planning in strong, dynamic currents using thousands of highly under-actuated vehicles. We address the specific task of path planning for a global network of ocean-observing floats. These submersibles are typified by the Argo global network consisting of over 3000 sensor platforms. They can control their buoyancy to float at depth for data collection or rise to the surface for satellite communications. Currently, floats drift at a constant depth regardless of the local currents. However, accurate current forecasts have become available which present the possibility of intentionally controlling floats' motion by dynamically commanding them to linger at different depths. This project explores the use of these current predictions to direct float networks to some desired final formation or position. It presents multiple algorithms for such path optimization and demonstrates their advantage over the standard approach of constant-depth drifting.

oceanography↗
NASA NTRS2012

Floating Oil-Spill Containment Device

Previous oil containment booms have an open top that allows natural gas to escape, and have significant oil leakage due to wave action. Also, a subsea pyramid oil trap exists, but cannot move relative to moving oil plumes from deepsea oil leaks. The solution is to have large, moveable oil traps. One version floats on the sea surface and has a flexible tarp cover and a lower weighted skirt to completely entrap the floating oil and natural gas. The device must have at least three sides with boats pulling at each apex, and sonar or other system to track the slowly moving oil plume, so that the boats can properly locate the booms. The oil trap device must also have a means for removal of the oil and the natural gas. A second design version has a flexible pyramid cover that is attached by lines to ballast on the ocean floor. This is similar to fixed, metal pyramid oil capture devices in the Santa Barbara Channel off the coast of California. The ballast lines for the improved design, however, would have winches that can move the pyramid to always be located above the oil and gas plume. A third design is a combination of the first two. It uses a submerged pyramid to trap oil, but has no anchor and uses boats to locate the trap. It has ballast weights located along the bottom of the tarp and/or at the corners of the trap. The improved floating oil-spill containment device has a large floating boom and weighted skirt surrounding the oil and gas entrapment area. The device is triangular (or more than three sides) and has a flexible tarp cover with a raised gas vent area. Boats pull on the apex of the triangles to maintain tension and to allow the device to move to optimum locations to trap oil and gas. The gas is retrieved from a higher buoyant part of the tarp, and oil is retrieved from the floating oil layer contained in the device. These devices can be operated in relatively severe weather, since waves will break over the devices without causing oil leaking. Also, natural gas is entrapped and can be retrieved. All designs can use sonar to locate the moving oil plume, and then be relocated by using boats or winches to move the oil trapping devices. These devices can be constructed of treated, non-permeable DuPont Kevlar cloth (or similar material).

Jones, Jack A.↗
NASA NTRS2022

Vertical Structure in Phytoplankton Growth and Productivity Inferred From Biogeochemical-Argo Floats and the Carbon-Based Productivity Model

Estimates of marine net primary production (NPP) commonly rely on limited in situ 14C incubations or satellite-based algorithms mainly constrained to the surface ocean. Here we combine data from biogeochemical Argo floats with a carbon-based productivity model (CbPM) to compute vertically-resolved estimates of NPP. Inferred NPP profiles derived by informing the CbPM with float-based, depth-resolved, bio-optical data are able to qualitatively reproduce the vertical structure in NPP inferred from in situ 14C incubations at various ocean regions. At station ALOHA, float-based estimates agree within uncertainty with productivity observations at depth, but underestimate surface NPP. We test the ability of the CbPM to infer the depth-resolved structure in NPP from bio-optical properties in the mixed layer, in similar fashion as how remote sensing algorithms of ocean productivity operate. In Southern Ocean waters, the depth-reconstructing implementation of the CbPM overestimates phytoplankton division rates and Chl:C below the mixed layer, resulting in artificially high subsurface NPP when compared with the fully float-informed implementation of the model. The CbPM subsurface extrapolation of phytoplankton Chl, Chl:C division rates, and NPP improves by accounting for deep nutrient (iron) stress impacts on photoacclimation in the Southern Ocean. This improvement is also observed in vertically- integrated NPP, where the mean bias between model implementations in depth-integrated productivity south of 30◦S is reduced by 62 % when account for deep iron limitation. Our results demonstrate that profiling data from biogeochemical Argo floats can serve to inform regional adjustments that lead to the improvement of marine productivity algorithms.

NPP↗
NASA NTRS1928

Tank Tests of Twin Seaplane Floats

The following report contains the most essential data for the hydrodynamic portion of the twin-float problem. The following points were successfully investigated: 1) difference between stationary and nonstationary flow; 2) effect of the shape of the step; 3) effect of distance between floats; 4) effect of nose-heavy and tail-heavy moments; 5) effect of the shape of floats; 6) maneuverability.

FLOAT STEPS↗
NASA NTRSDate not supplied

Automatic Generation of Guard-Stable Floating-Point Code

In floating-point programs, test instability occurs when the control flow of a conditional statement diverges from its ideal execution under real arithmetic. This phenomenon is caused by the presence of round-off errors in floating-point computations. Writing programs that correctly handle test instability often require expertise on finite precision computations and rounding errors. This paper presents a fully automatic tool chain that generates and formally verifies a test-stable floating-point C program from its functional specification in real arithmetic. The generated program is instrumented to soundly detect when unstable tests may occur and, in these cases, to issue a warning. The proposed approach combines the PRECiSA floating-point static analyzer, the Frama-C software verification suite, and the PVS theorem prover.

Floating-Point Arithmetic↗
NASA NTRSDate not supplied

A Provably Correct Floating-Point Implementation of Well Clear Avionics Concepts

The NASA DAIDALUS library provides formal definitions for Detect-and-Avoid avionics concepts such as when an aircraft is well-clear with respect to the surrounding air traffic, i.e., it does not operate in such proximity to create a collision hazard. While several properties are proven correct for DAIDALUS assuming ideal real number arithmetic, an actual implementation that uses floating-point numbers may behave unexpectedly because of round-off errors and run-time exceptions. This paper presents an experience report on the application of a formal methods toolchain to extract and verify floating-point C code from a real-valued specification of the well-clear module of DAIDALUS. This toolchain comprises the PVS theorem prover, the PRECiSA floating-point analyzer and code generator, and the Frama-C analysis suite. The generated code is automatically instrumented to detect when the control flow of the floating-point program may diverge from the ideal real number specification, and it is annotated with contracts that state the maximum accumulated round-off error. The absence of overflows is also formally verified for the generated code. In order to apply the toolchain to an industrial case study such as DAIDALUS, a formally verified pre-processing of the input specification is performed, which includes a program slicing and several semantic-preserving simplifications.

Program verification↗