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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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Active Suppression of Pogo on the Space Shuttle

The use of active pogo suppressors on the space shuttle was qualitatively investigated. Suppressor design concepts and the effectiveness of these designs in maintaining the stability of the shuttle vehicle were the primary concerns. Suppressor design concepts were developed by means of a series of parametric stability analyses. These two designs together with two designs provided by NASA were evaluated in detail for control effectiveness, performance relative to a passive suppression device, sensitivity of performance to feedback error, suppressor volume flow requirements, and suppressor development requirements. An active device at the high pressure oxidizer pump inlet was shown to provide a simple and effective design that is insensitive to error in the feedback signal. The sizing of an active suppressor was demonstrated to be dependent upon knowledge of the dynamic characteristics of the system.

Lock, M. H.↗
NASA NTRS1972

Fan noise suppression

The principal suppressor parameters and their relationships have been used to formulate a suppressor design methodology which has been applied to the design of several full-scale suppressors. Tests of these suppressors on several full-scale fans have demonstrated noise reductions of the order of 10 PNdB. The amount of suppression in several instances seems to have been limited by reaching noise floors that are not clearly at the estimated jet noise level but are not far above it. In addition to identifying noise floors, two other areas are considered. The first is attenuation by the fan exhaust suppressors, which seems in most cases to be less than that of the inlet. The second is the effectiveness of outer cowl treatment alone on multiple pure tones. This question relates to whether a high-speed fan can become as quiet as a low-speed fan without a substantial increase in the amount of treatment.

Feiler, C. E.↗
NASA NTRS1973

Preliminary study of turbojets with rotary flow inductors for a low-noise supersonic transport

In a simplified airplane-mission study for a Mach 2.61 supersonic transport, dry turbojets with and without real suppressors and dry turbojets with ideal rotary flow inductors were studied for sideline noise levels as low as FAR 36-20. Compressor pressure ratio was varied from 5 to 30 and turbine temperature from 1800 to 3000 F. For no noise constraint and without a suppressor, the best dry turbojet gave a payload of 9.0 percent of gross weight and a sideline noise of 126 effective perceived noise decibels. Payload dropped rapidly for lower noise goals, becoming 6.3 percent of gross weight at FAR 36. At FAR 36, the turbojet with suppressor gave a payload of 8.3 percent and the turbojet with ideal rotary flow inductor, 7.3 percent. Below FAR 36, the ideal inductor was far superior to the real suppressor, giving payloads of 6.6 percent at FAR 36-10 and 5.7 percent at FAR 36-20.

Dugan, J. F., Jr.↗
NASA NTRS1972

Comparative performance of several SST configurations powered by noise limited turbojet engines

A simplified study was made in which the mission performances of three Mach 2.7 airplane configurations were compared. Both wing loading and size of the unaugmented turbojet engines were varied at different levels of suppressor technology. The lowest gross weight and the best return on investment were obtained with an advanced arrow wing configuration when a mission range of 4200 nautical miles was specified. This comparison was made for the takeoff noise levels specified in F.A.R. 36 using retractable jet noise suppressors assumed to be capable of 15 PNdb of suppression with only a 7.5-percent thrust loss. With less advanced suppressor technology, a modified delta configuration is a close competitor of the arrow wing. Despite its good takeoff characteristics, a swing-wing configuration was too structurally heavy to be competitive at F.A.R. 36 noise levels. Engine performance and weight commensurate with engine definition in 1975 were postulated.

Whitlow, J. B., Jr.↗
NASA NTRS1980

A universal procedure for evaluation and application of surge-protective devices

The source, nature, and frequency of occurrence of transients must be identified and a representative standard test wave chosen for proof testing. The performance of candidate suppressor devices then can be evaluated against the withstand goals set for the equipment. The various suppressors divide into two classes of generic behavior. The key to a universal procedure for evaluating both classes lies in representing transients as quasi-current sources of defined current impulse duration. The available surge current is established by the Thevenin equivalent transient voltage and source impedance. A load line drawn on the V-I characteristic graph of the suppressor quickly determines the clamping voltage and peak current. These values then can be compared to the requirement. The deposited energy and average power dissipation for multiple transients also can be calculated. The method is illustrated with a design example for motor vehicle alternator load dump suppression.

Source record↗
NASA NTRS1980

Results from flight noise tests on a Viper turbojet fitted with ejector/suppressor nozzle systems

Noise tests have been performed on a range of advanced exhaust suppressors fitted to a Viper turbojet engine with the objective of evaluating systems potentially suitable for subsonic and supersonic aircraft. A key item in the suppressor systems was an acoustically lined ejector, and tests were made with and without this ejector. Flight tests were made using an HS-125 aircraft in England and were followed by outdoor static tests at NASA Ames Research Center. In addition, acoustic and propulsion measurements were made at static, and in simulated flight conditions, with the engine installed in the Ames 40- by 80-ft wind tunnel. The paper deals mainly with the flight test results. These show that the use of a lined ejector considerably increases the attenuation obtainable using a suppressor nozzle alone and largely confirm predictions made on the basis of previous model and static tests. The maximum measured attenuation adjusted to an altitude of 500 ft was 14 EPNdB at an ideal jet velocity of 2400 ft/sec using the suppressor/ejector design intended for supersonic application. Initial propulsion performance results from the Ames wind tunnel confirm previous smaller scale propulsion results from a Douglas facility.

Brooks, J. R.↗
NASA NTRS1980

Mechanical suppression: Modern technology applied to an old art

Various suppressor configurations were analyzed and evaluated in an effort to reduce combustion instability and improved ballistic reproducibility of the MK 12 motor. A static firing test series of eight field return boosters featured two baseline motor firings with the existing suppressor in each motor, followed by two tests each of two different prototype suppressor designs. Results were analyzed and used to generate the design for the final two firings. Acoustic pressure pulsers were utilized to measure the damping effectiveness of the final design. The reduction in motor vibration and acoustic pressure levels between the baseline tests and the final two improved lightweight tests was significant. The average acceleration level of the motors equipped with flightweight rods was reduced to only 5% of the level in the unmodified motors; the average acoustic pressure level was reduced to 20%; maximum values were reduced to 6% for acceleration and 23% for pressure.

Crockford, W. H.↗
NASA NTRS1991

Circuit protection devices for transient suppression

The Electromer Corporation has developed a series of transient voltage suppression components based on a patented, specially formulated PolyClamp (trademark) material. PolyClamp components are a new class of transient voltage surge suppressors that extend the range of protection offered by transients protectors. The PolyClamp transient surge suppressors provide low capacitance, high energy capability, and packaging flexibility. A wide variety of applications can be protected. A tube and ferrule configuration was designed to be used with MIL/Aerospace style connectors and is designed to meet the applicable environmental, mechanical, and electrical requirements as defined by the United States and European defence standards performance requirements. Here, PolyClamp is compared with current transient surge suppressors. Typical performance and design are discussed.

Childers, Richard↗
NASA NTRS1994

Feedback Control of Plasma Instabilities with Charged Particle Beams and Study of Plasma Turbulence

A new non-perturbing technique for feedback control of plasma instabilities has been developed in the Columbia Linear Machine (CLM). The feedback control scheme involves the injection of a feedback modulated ion beam as a remote suppressor. The ion beam was obtained from a compact ion beam source which was developed for this purpose. A Langmuir probe was used as the feedback sensor. The feedback controller consisted of a phase-shifter and amplifiers. This technique was demonstrated by stabilizing various plasma instabilities to the background noise level, like the trapped particle instability, the ExB instability and the ion-temperature-gradient (ITG) driven instability. An important feature of this scheme is that the injected ion beam is non-perturbing to the plasma equilibrium parameters. The robustness of this feedback stabilization scheme was also investigated. The principal result is that the scheme is fairly robust, tolerating about 100% variation about the nominal parameter values. Next, this scheme is extended to the unsolved general problem of controlling multimode plasma instabilities simultaneously with a single sensor-suppressor pair. A single sensor-suppressor pair of feedback probes is desirable to reduce the perturbation caused by the probes. Two plasma instabilities the ExB and the ITG modes, were simultaneously stabilized. A simple 'state' feedback type method was used where more state information was generated from the single sensor Langmuir probe by appropriate signal processing, in this case, by differentiation. This proof-of-principle experiment demonstrated for the first time that by designing a more sophisticated electronic feedback controller, many plasma instabilities may be simultaneously controlled. Simple theoretical models showed generally good agreement with the feedback experimental results. On a parallel research front, a better understanding of the saturated state of a plasma instability was sought partly with the help of feedback. A plasma instability is usually observed in its saturated state and appears as a single feature in the frequency spectrum with a single azimuthal and parallel wavenumbers. The physics of the non-zero spectral width was investigated in detail because the finite spectral width can cause "turbulent" transport. One aspect of the "turbulence" was investigated by obtaining the scaling of the linear growth rate of the instabilities with the fluctuation levels. The linear growth rates were measured with the established gated feedback technique. The research showed that the ExB instability evolves into a quasi-coherent state when the fluctuation level is high. The coherent aspects were studied with a bispectral analysis. Moreover, the single spectral feature was discovered to be actually composed of a few radial harmonics. The radial harmonics play a role in the nonlinear saturation of the instability via three-wave coupling.

Tham, Philip Kin-Wah↗
NASA NTRS1999

High-Lift Engine Aeroacoustics Technology (HEAT) Test Program Overview

The NASA High-Speed Research program developed the High-Lift Engine Aeroacoustics Technology (HEAT) program to demonstrate satisfactory interaction between the jet noise suppressor and high-lift system of a High-Speed Civil Transport (HSCT) configuration at takeoff, climb, approach and landing conditions. One scheme for reducing jet exhaust noise generated by an HSCT is the use of a mixer-ejector system which would entrain large quantities of ambient air into the nozzle exhaust flow through secondary inlets in order to cool and slow the jet exhaust before it exits the nozzle. The effectiveness of such a noise suppression device must be evaluated in the presence of an HSCT wing high-lift system before definitive assessments can be made concerning its acoustic performance. In addition, these noise suppressors must provide the required acoustic attenuation while not degrading the thrust efficiency of the propulsion system or the aerodynamic performance of the high-lift devices on the wing. Therefore, the main objective of the HEAT program is to demonstrate these technologies and understand their interactions on a large-scale HSCT model. The HEAT program is a collaborative effort between NASA-Ames, Boeing Commercial Airplane Group, Douglas Aircraft Corp., Lockheed-Georgia, General Electric and NASA - Lewis. The suppressor nozzles used in the tests were Generation 1 2-D mixer-ejector nozzles made by General Electric. The model used was a 13.5%-scale semi-span model of a Boeing Reference H configuration.

Zuniga, Fanny A.↗
NASA NTRS2002

Thrust Augmentation with Mixer/Ejector Systems

Older commercial aircraft often exceed FAA (Federal Aviation Administration) sideline noise regulations. The major problem is the jet noise associated with the high exhaust velocities of the low bypass ratio engines on such aircraft. Mixer/ejector exhaust systems can provide a simple means of reducing the jet noise on these aircraft by mixing cool ambient air with the high velocity engine gases before they are exhausted to ambient. This paper presents new information on thrust performance predictions, and thrust augmentation capabilities of mixer/ejectors. Results are presented from the recent development program of the patented Alternating Lobe Mixer Ejector Concept (ALMEC) suppressor system for the Gulfstream GII, GIIB and GIII aircraft. Mixer/ejector performance procedures are presented which include classical control volume analyses, compound compressible flow theory, lobed nozzle loss correlations and state of the art computational fluid dynamic predictions. The mixer/ejector thrust predictions are compared to subscale wind tunnel test model data and actual aircraft flight test measurements. The results demonstrate that a properly designed mixer/ejector noise suppressor can increase effective engine bypass ratio and generate large thrust gains at takeoff conditions with little or no thrust loss at cruise conditions. The cruise performance obtained for such noise suppressor systems is shown to be a strong function of installation effects on the aircraft.

Presz, Walter M., Jr.↗
DOE OSTI2021

KIBRA connects Hippo signaling and cancer

The Hippo signaling pathway is a tumor suppressor pathway that plays an important role in tissue homeostasis and organ size control. KIBRA is one of the many upstream regulators of the Hippo pathway. It functions as a tumor suppressor by positively regulating the core Hippo kinase cascade. However, there are accumulating shreds of evidence showing that KIBRA has an oncogenic function, which we speculate may arise from its functions away from the Hippo pathway. In this review, we have attempted to provide an overview of the Hippo signaling with a special emphasis on evidence showing the paradoxical role of KIBRA in cancer.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2021

Human α-defensin 5 suppressed colon cancer growth by targeting PI3K pathway

Defensins are highly conserved antimicrobial peptides, which ubiquitously expressed in different species. In addition to the functions in host defense, their aberrant expression have also been documented in cancerous tissue including breast cancer, lung caner and renal carcinoma etc. Whereas, roles of Defensin Alpha 5 (DEFA5) in colon cancer has not been explored. Bioinformatic analysis was used to study the expression of DEFA5 and its correlation with clinical outcomes; Western blot, qPCR, Co-immunoprecipitation, xenograft models were used to the study the molecular mechanism. Decreased expression of DEFA5 at protein level was observed in colon tissues. Colon cancer cell lines proliferation and colony formation capacity were significantly suppressed by DEFA5 overexpression. Moreover, in vivo tumor growth in nude mice was also suppressed by DEFA5 overexpression, suggesting a tumor suppressor role of DEFA5 in colon cancer. Mechanistically, DEFA5 directly binds to the subunits of PI3K complex, thus attenuates the downstream signaling transduction, leads to delayed cell growth and metastasis. Collectively, we concluded that DEFA5 showed an inhibitory effect in colon cancer cell growth and may serve as a potential tumor suppressor in colon cancer.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2021

MiR-10b-5p inhibits tumorigenesis in gastric cancer xenograft mice model through down-regulating Tiam1

Highlights: • MiR-10b-5p acted as a tumor suppressor in gastric cancer by targeting and down-regulating Tiam1. • Overexpression of miR-10b-5p induced apoptosis of gastric cancer cells. • As a specifically chemically modified miRNA mimics, agomir-10b-5p can accumulate in target cells after overcoming membrane and tissue barriers in vivo. • Agomir-10b-5p could be a potential therapeutic agent for the treatment of gastric cancer. The miR-10b-5p plays an important role in gastric cancer development but its exact effect on gastric cancer development in vivo has not been fully studied. We showed that miR-10b-5p inhibited the proliferation and migration of gastric cancer cells by down-regulating Tiam1 which was up-regulated in both gastric cancer cells and tissues. Gastric cancer xenograft experiment showed that lenti-miR-10b-5p treatment and agomir-10b-5p injection could significantly retard tumor growth and reduce tumor size and induced apoptosis. Therefore, our results elucidate the tumor suppressor role of miR-10b-5p in gastric cancer in which it acts as a negative regulator of Tiam1 and also provide a molecular mechanism for agomir-10b-5p to treat gastric cancer.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2025

A cytosolic glyoxylate shunt complements the canonical photorespiratory pathway in Arabidopsis

Photorespiration functions in part to support photosynthetic performance, especially under stress such as high light, yet the underlying mechanisms are poorly understood. To identify modulators of photorespiration under high light, we have isolated genetic suppressors of the photorespiratory mutant hpr1 (hydroxypyruvate reductase 1) from Arabidopsis. A suppressor that partially rescues hpr1 is mapped to GLYR1, which encodes the cytosolic glyoxylate reductase 1 that converts glyoxylate to glycolate. Independent glyr1 mutants also partially rescue hpr1 and another photorespiratory mutant, catalase 2. Our genetic, transcriptomic and metabolic profiling analyses together reveal a connection between cytosolic glyoxylate and a non-canonical photorespiratory route mediated by HPR2, which we name the photorespiratory glyoxylate shunt. This shunt complements the canonical photorespiratory pathway and is especially critical when high photorespiratory fluxes are required and when the major photorespiratory pathway is deficient. Our findings support the metabolic flexibility of photorespiration and may help to improve crop performance under stress.

Light stress↗
DOE OSTI2023

A cryptic oxidoreductase safeguards oxidative protein folding in Corynebacterium diphtheriae

In many gram-positive Actinobacteria, including Actinomyces oris and Corynebacterium matruchotii , the conserved thiol-disulfide oxidoreductase MdbA that catalyzes oxidative folding of exported proteins is essential for bacterial viability by an unidentified mechanism. Intriguingly, in Corynebacterium diphtheriae , the deletion of mdbA blocks cell growth only at 37 °C but not at 30 °C, suggesting the presence of alternative oxidoreductase enzyme(s). By isolating spontaneous thermotolerant revertants of the mdbA mutant at 37 °C, we obtained genetic suppressors, all mapped to a single T-to-G mutation within the promoter region of tsdA , causing its elevated expression. Strikingly, increased expression of tsdA —via suppressor mutations or a constitutive promoter—rescues the pilus assembly and toxin production defects of this mutant, hence compensating for the loss of mdbA . Structural, genetic, and biochemical analyses demonstrated TsdA is a membrane-tethered thiol-disulfide oxidoreductase with a conserved CxxC motif that can substitute for MdbA in mediating oxidative folding of pilin and toxin substrates. Together with our observation that tsdA expression is upregulated at nonpermissive temperature (40 °C) in wild-type cells, we posit that TsdA has evolved as a compensatory thiol-disulfide oxidoreductase that safeguards oxidative protein folding in C. diphtheriae against thermal stress.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

Tris(isodecyl)guanidine Degradation in the MCU System

The current solvent blend consists of four components; an extractant, the modifier, a suppressor, and the diluent. Of the four components, only the suppressor – tris(isodecyl)guanidine (TiDG) has exhibited an appreciable depletion rate during facility operations. Using data derived from Modular Caustic-Side Solvent Extraction Unit (MCU) process samples, Savannah River National Lab (SRNL) derived a method to predict the TiDG depletion based upon time and volume of feed processed.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2021

Solvent Hold Tank Sample Results for MCU-20-32-33-34 (Quarterly Report, September 2020)

In late FY13, MCU implemented the Next Generation Solvent (NGS) flow sheet. Facility personnel added a non-radioactive, NGS “cocktail” containing the new Extractant (MaxCalix) and a new Suppressor (TiDG) to the SHT heel to implement the NGS flow sheet. The resulting “blend” solvent (“NGS blend solvent”) is essentially NGS with residual amounts of calix[4]arene-bis(tert-octylbenzo-crown-6) (BOBCalixC6) and trioctylamine (TOA). For process monitoring, SHT samples are sent to Savannah River National Laboratory (SRNL) to examine solvent composition changes over time. With the exception of Isopar™ L which is regularly added to the SHT due to its high vapor pressure, this report shows the cumulative chemical composition data, including impurities like mercury, of the September 2020 (MCU-20-32-33-34) solvent SHT sample. A summary report of the September SHT solvent sample was issued earlier. This report examines the cumulative results from these and several past monthly reports. These samples are intended to verify that the solvent is within the specified composition range. A baseline “scratch” solvent - a scratch solvent is a preparation of all 6 solvent components (this includes the old extractant BoBCalix and the old suppressor TrioctylAmine that remained when solvent was converted to Next Generation Solvent [NGS]) of the composition that approximates the blend of cocktail and heel solvent - was prepared in the lab (September 2018) and used for comparison and evaluation. The results from the analyses are presented in this document. This report is the last characterization analysis of the SHT solvent. MCU entered a lay-up state and about 128 gallons of the SHT solvent were pumped into 55 gallons drums for future disposal.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗