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Waviness of less than 0.004 inch achieved using titanium strips. Process uses titanium balancing strips to keep waviness within 0.004inch limit. Balancing strips reduce thermal bonding stresses on lower fiberglass fluted sections and placed so fiberglass ends up sandwiched between porous titanium skin and titanium balance strip. Method requires less skill and less labor intensive than composite-wrapped-mandrel method.
Ponderomotive stabilization of rigid plasma flute modes is numerically investigated by use of a variational principle, for a simple geometry, without eikonal approximation. While the near field of the studied antenna can be stabilizing, the far field has a small contribution only, because of large cancellation by quasi mode-coupling terms. The field energy for stabilization is evaluated and is a nonnegligible fraction of the plasma thermal energy. A new antenna design is proposed, and feedback stabilization is investigated. Their use drastically reduces power requirements.
The cascades of ideal invariants in the flute-mode turbulence are analyzed by considering a statistics based on an elementary three-mode coupling process. The statistical dynamics of the system is investigated on the basis of the existence of the physically most important (PMI) triad. When finite ion Larmor radius effects are considered, the PMI triad describes the formation of zonal flows.
The development of durable bonded joint technology for assembling composite structures is an essential component of future space technologies. While NASA is working toward providing an entirely new capability for human space exploration beyond low Earth orbit, the objective of this project is to design, fabricate, analyze, and test a NASA patented durable redundant joint (DRJ) and a NASA/Boeing co-designed fluted-core joint (FCJ). The potential applications include a wide range of sandwich structures for NASA's future launch vehicles. Three types of joints were studied -- splice joint (SJ, as baseline), DRJ, and FCJ. Tests included tension, after-impact tension, and compression. Teflon strips were used at the joint area to increase failure strength by shifting stress concentration to a less sensitive area. Test results were compared to those of pristine coupons fabricated utilizing the same methods. Tensile test results indicated that the DRJ design was stiffer, stronger, and more impact resistant than other designs. The drawbacks of the DRJ design were extra mass and complex fabrication processes. The FCJ was lighter than the DRJ but less impact resistant. With barely visible but detectable impact damages, all three joints showed no sign of tensile strength reduction. No compression test was conducted on any impact-damaged sample due to limited scope and resource. Failure modes and damage propagation were also studied to support progressive damage modeling of the SJ and the DRJ.
The fluted cylinder test article was available from a past test, and was a representative shape and size for the USA program to test its acoustic foam treatment. Modal testing's purpose was to define the damping of the structure to be fed into the acoustic models.
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It is shown that the source region for Saturnian kilometric radiation which originates in the high latitude near-noon dayside ionosphere can be mapped via the Saturn magnetic field to the outer edge of the dayside equatorial plasma sheet. It is shown how the MHD waves observed at the outer boundary of the plasma sheet may be causally related to the field-aligned acceleration of electrons to keV energies. It is suggested that the strong emission peak at a fixed Saturnian longitude is a consequence of locally reduced electron plasma frequency to electron gyrofrequency ratio.
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Two items of Tailorable Advanced Blanket Insulation (TABI) for Advanced Space Transportation Systems were produced. The first consisted of flat panels made from integrally woven, 3-D fluted core having parallel fabric faces and connecting ribs of Nicalon silicon carbide yarns. The triangular cross section of the flutes were filled with mandrels of processed Q-Fiber Felt. Forty panels were prepared with only minimal problems, mostly resulting from the unavailability of insulation with the proper density. Rigidizing the fluted fabric prior to inserting the insulation reduced the production time. The procedures for producing the fabric, insulation mandrels, and TABI panels are described. The second item was an effort to determine the feasibility of producing contoured TABI shapes from gores cut from flat, insulated fluted core panels. Two gores of integrally woven fluted core and single ply fabric (ICAS) were insulated and joined into a large spherical shape employing a tadpole insulator at the mating edges. The fluted core segment of each ICAS consisted of an Astroquartz face fabric and Nicalon face and rib fabrics, while the single ply fabric segment was Nicalon. Further development will be required. The success of fabricating this assembly indicates that this concept may be feasible for certain types of space insulation requirements. The procedures developed for weaving the ICAS, joining the gores, and coating certain areas of the fabrics are presented.
A significant discovery of the Mars Pathfinder (MPF) mission was that many rocks exhibit characteristics of ventifacts, rocks that have been sculpted by saltating particles. Diagnostic features identifying the rocks as ventifacts am elongated pits, flutes, and grooves (collectively referred to as "flutes" unless noted otherwise). Faceted rocks or rock portions, circular pits, rills, and possibly polished rock surfaces are also seen and could be due, to aeolian abrasion. Many of these features were initially identified in rover images, where spatial resolution generally exceeded that of the IMP (Imager for Mars Pathfinder) camera. These images had two major limitations: 1) Only a limited number of rocks were viewed by the rover, biasing flute statistics; and 2) The higher resolution obtained by the rover images and the lack of such pictures at the Viking landing sites hampered comparisons of rock morphologies between the Pathfinder and Viking sites. To avoid this problem, rock morphology and ventifact statistics have been examined using new "super-resolution" IMP and Viking Lander images. Analyses of these images show that: 1) Flutes are seen on about 50% or more of the rocks in the near field at the MPF site; 2) The orientation of these flutes is similar to that for flutes identified in rover images; and 3) Ventifacts are significantly more abundant at the Pathfinder landing site than at the two Viking Landing sites, where rocks have undergone only a limited amount of aeolian abrasion. This is most likely due to the ruggedness of the Pathfinder site and a greater supply of abrading particles available shortly after the Arcs and Tiu Valles outflow channel floods.
The feasibility of weaving Nextel ceramic and Nicalon silicon carbide yarns into integrally woven, three dimensional fluted core fabrics was demonstrated. Parallel face fabrics joined with woven fabric ribs to form triangular cross section flutes between the faces were woven into three single and one double layer configuration. High warp yarn density in the double layer configuration caused considerable yarn breakage during weaving. The flutes of all four fabrics were filled with mandrels made from Q-Fiber Felt and FRCI-20-12 to form candidate insulation panels for advanced Space Transportation Systems. Procedures for preparing and inserting the mandrels were developed. Recommendations are made on investigating alternate methods for filling the flutes with insulation, and for improving the weaving of these types of fabrics.
Two types of Tailorable Advanced Blanket Insulation (TABI) flat panels for Advanced Space Transportation Systems were produced. Both types consisted of integrally woven, 3-D fluted core having parallel faces and connecting ribs of Nicalon yarns. The triangular cross section flutes of one type was filled with mandrels of processed Ultrafiber (aluminoborosilicate) stitchbonded Nextel 440 fibrous felt, and the second type wall filled with Saffil alumina fibrous felt insulation. Weaving problems were minimal. Insertion of the fragile insulation mandrels into the fabric flutes was improved by using a special insertion tool. An attempt was made to weave fluted core fabrics from Nextel 440 yarns but was unsuccessful because of the yarn's fragility. A small sample was eventually produced by an unorthodox weaving process and then filled with Saffil insulation. The procedures for setting up and weaving the fabrics and preparing and inserting insulation mandrels are discussed. Characterizations of the panels produced are also presented.
Rocks observed by the Viking Landers and Pathfinder Lander/Sojourner rover exhibit a suite of perplexing rock textures. Among these are pits, spongy textures, penetrative flutes, lineaments, crusts, and knobs Fluvial, impact, chemical alteration, and aeolian mechanisms have been proposed for many of these. In an effort to better understand the origin and characteristics of Martian rock textures, abraded rocks in the Mojave Desert and other regions have been studied. We find that most Martian rock textures, as opposed to just a few, bear close resemblance to terrestrial aeolian textures and can most easily be explained by wind, not other, processes. Flutes, grooves, and some pits on Mars are consistent with abrasion by saltating particles, as described previously. However, many other rock textures probably also have an aeolian origin. Sills at the base of rocks that generally lie at high elevations, such as Half Dome, are consistent with such features on Earth that are related to moats or soil ramps that shield the basal part of the rock from erosion. Crusts consisting of fluted fabrics, such as those on Stimpy and Chimp, are similar to fluted crusts on Earth that spall off over time. Knobby and lineated rocks are similar to terrestrial examples of heterogeneous rocks that differentially erode. The location of specific rock textures on Mars also gives insight into their origin. Many of the most diagnostic ventifacts found at the Pathfinder site are located on rocks that lie near the crests or the upper slopes of ridges. On Earth, the most active ventifact formation occurs on sloped or elevated topography, where windflow is accelerated and particle kinetic energy and flux are increased. Integrated 0 together, these observations point to significant aeolian 0 modification of rocks on Mars and cast doubt on whether many primary textures resulting from other processes are preserved. Experimental simulations of abrasion in the presence of abundant sand indicate that rocks on Mars should erode at a rate of 7.7 to 210 micrometers/yr. These rates cannot have operated over the entire history of the Pathfinder site or elsewhere on Mars, because craters, knobs, and other obstacles would be quickly worn away. More likely, rock abrasion occurs over short time periods when sand supplies are sufficient and saltation friction speeds are frequently reached. Depletion or exhaustion of sand and a decline in wind fluxes at speeds greater than that of saltation friction will then act to reduce the rate of further abrasion. We are currently engaged in a new set of wind tunnel experiments coupled with theoretical models and field studies that address rock abrasion and ventifact formation on Mars and Earth. These studies have implications for the Noachian, when sand supplies were probably more plentiful and the threshold friction speed was possibly lower because of a more dense atmosphere. Under these conditions, erosion rates from the wind could have been much greater than to day, contributing, along with probable fluvial erosion, to the Noachian landscape that is in limited preservation today.
This device takes advantage of the centrifugal forces that are generated when a coring bit is rotated, and a granular sample is entered into the bit while it is spinning, making it adhere to the internal wall of the bit, where it compacts itself into the wall of the bit. The bit can be specially designed to increase the effectiveness of regolith capturing while turning and penetrating the subsurface. The bit teeth can be oriented such that they direct the regolith toward the bit axis during the rotation of the bit. The bit can be designed with an internal flute that directs the regolith upward inside the bit. The use of both the teeth and flute can be implemented in the same bit. The bit can also be designed with an internal spiral into which the various particles wedge. In another implementation, the bit can be designed to collect regolith primarily from a specific depth. For that implementation, the bit can be designed such that when turning one way, the teeth guide the regolith outward of the bit and when turning in the opposite direction, the teeth will guide the regolith inward into the bit internal section. This mechanism can be implemented with or without an internal flute. The device is based on the use of a spinning coring bit (hollow interior) as a means of retaining granular sample, and the acquisition is done by inserting the bit into the subsurface of a regolith, soil, or powder. To demonstrate the concept, a commercial drill and a coring bit were used. The bit was turned and inserted into the soil that was contained in a bucket. While spinning the bit (at speeds of 600 to 700 RPM), the drill was lifted and the soil was retained inside the bit. To prove this point, the drill was turned horizontally, and the acquired soil was still inside the bit. The basic theory behind the process of retaining unconsolidated mass that can be acquired by the centrifugal forces of the bit is determined by noting that in order to stay inside the interior of the bit, the frictional force must be greater than the weight of the sample. The bit can be designed with an internal sleeve to serve as a container for granular samples. This tube-shaped component can be extracted upon completion of the sampling, and the bottom can be capped by placing the bit onto a corklike component. Then, upon removal of the internal tube, the top section can be sealed. The novel features of this device are: center dot A mechanism of acquiring and retaining granular samples using a coring bit without a closed door. center dot An acquisition bit that has internal structure such as a waffle pattern for compartmentalizing or helical internal flute to propel the sample inside the bit and help in acquiring and retaining granular samples. center dot A bit with an internal spiral into which the various particles wedge. center dot A design that provides a method of testing frictional properties of the granular samples and potentially segregating particles based on size and density. A controlled acceleration or deceleration may be used to drop the least-frictional particles or to eventually shear the unconsolidated material near the bit center.
An hermetic seal for a linear rod having a portion thereof projected axially through a port defined in a wall for a pressure chamber and supported thereby for omni-directional motion is described. The seal is characterized by a resilient, impervious, cylindrical body having a first section concentrically related to the shaft and integrally affixed thereto comprising a linear ordered array of annular flutes. A second section integrally is affixed to the wall of the chamber and concentrically related to the port comprising a second linear ordered array of annular flutes. A third section is interposed between the first and second sections and integrally affixed in coaxial alignment therewith comprising an annular ordered array of linear flutes concentrically related to the shaft, whereby axial, angular, and pivotal motion of the rod is accommodated.
Ultrasonic/sonic rotary-hammer drill (USRoHD) is a recent addition to the collection of apparatuses based on ultrasonic/sonic drill corer (USDC). As described below, the USRoHD has several features, not present in a basic USDC, that increase efficiency and provide some redundancy against partial failure. USDCs and related apparatuses were conceived for boring into, and/or acquiring samples of, rock or other hard, brittle materials of geological interest. They have been described in numerous previous NASA Tech Briefs articles. To recapitulate: A USDC can be characterized as a lightweight, lowpower, piezoelectrically driven jackhammer in which ultrasonic and sonic vibrations are generated and coupled to a tool bit. A basic USDC includes a piezoelectric stack, an ultrasonic transducer horn connected to the stack, a free mass ( free in the sense that it can bounce axially a short distance between hard stops on the horn and the bit), and a tool bit. The piezoelectric stack creates ultrasonic vibrations that are mechanically amplified by the horn. The bouncing of the free mass between the hard stops generates the sonic vibrations. The combination of ultrasonic and sonic vibrations gives rise to a hammering action (and a resulting chiseling action at the tip of the tool bit) that is more effective for drilling than is the microhammering action of ultrasonic vibrations alone. The hammering and chiseling actions are so effective that unlike in conventional twist drilling, little applied axial force is needed to make the apparatus advance into the material of interest. There are numerous potential applications for USDCs and related apparatuses in geological exploration on Earth and on remote planets. In early USDC experiments, it was observed that accumulation of cuttings in a drilled hole causes the rate of penetration of the USDC to decrease steeply with depth, and that the rate of penetration can be increased by removing the cuttings. The USRoHD concept provides for removal of cuttings in the same manner as that of a twist drill: An USRoHD includes a USDC and a motor with gearhead (see figure). The USDC provides the bit hammering and the motor provides the bit rotation. Like a twist drill bit, the shank of the tool bit of the USRoHD is fluted. As in the operation of a twist drill, the rotation of the fluted drill bit removes cuttings from the drilled hole. The USRoHD tool bit is tipped with a replaceable crown having cutting teeth on its front surface. The teeth are shaped to promote fracturing of the rock face through a combination of hammering and rotation of the tool bit. Helical channels on the outer cylindrical surface of the crown serve as a continuation of the fluted surface of the shank, helping to remove cuttings. In the event of a failure of the USDC, the USRoHD can continue to operate with reduced efficiency as a twist drill. Similarly, in the event of a failure of the gearmotor, the USRoHD can continue to operate with reduced efficiency as a USDC.
NASA's Resource Prospector (RP) project intends to characterize the 3D distribution of volatiles in permanently shadowed regions at the lunar poles. One RP remote sensing instrument is a near-infrared spectrometer with an associated camera and radiometer, called the Near-InfraRed Volatile Spectrometer System (NIRVSS). In May 2016, NIRVSS, a Honeybee Robotics drill, and an Inficon mass spectrometer were placed in a vacuum chamber at Glenn Research Center. Also inside was a tube (1.2 m high x 25 cm diameter) filled with lunar simulant NU-LHT-3M, initially doped with a homogeneous water abundance of ~5%, chilled to cryogenic temperatures and exposed to a vacuum (~10e-6 Torr). During drilling, the NIRVSS instruments observed the cuttings pile as subsurface materials were emplaced on the surface. Spectral features associated with water ice, near 2000 and 3000 nm, were measured by the spectrometer during drilling. The spectral data documents development of a desiccated soil layer in the tube down to ~25-30 cm (confirmed by post-test soil analyses), formed during the initial pump down to vacuum. Drilling occurred in 10 cm segments, with the drill stem extracted and flutes brushed after each 10 cm depth. One exception to this was the 40 cm depth segment where the soil was delivered to a sample capture mechanism, and sealed for post-test analyses. To ~30 cm depth the greatest 2000 and 3000 nm signatures were associated with brushing of the drill flutes above the surface. At depths >40 cm the strongest ice signatures were associated with the drill clearing soil from the existing hole, or beginning to encounter new material. For these greater depths, brushing the flutes after extraction produced much weaker ice signatures than for shallower depths. This suggests that the soil may remain trapped in the exit funnel and is not emplaced on the surface. After each event creating strong ice signatures, these signatures decreased to near background levels in 5 minutes or less, due to surface exposure to vacuum.