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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

The reduction of takeoff ground roll by the application of a nose gear jump strut

A series of flight tests were conducted to evaluate the reduction of takeoff ground roll distance obtainable from a rapid extension of the nose gear strut. The NASA Quiet Short-haul Research Aircraft (QSRA) used for this investigation is a transport-size short take off and landing (STOL) research vehicle with a slightly swept wing that employs the upper surface blowing (USB) concept to attain the high lift levels required for its low-speed, short-field performance. Minor modifications to the conventional nose gear assembly and the addition of a high-pressure pneumatic system and a control system provided the extendable nose gear, or jump strut, capability. The limited flight test program explored the effects of thrust-to-weight ratio, wing loading, storage tank initial pressure, and control valve open time duration on the ground roll distance. The data show that a reduction of takeoff ground roll on the order of 10 percent was achieved with the use of the jump strut, as predicted. Takeoff performance with the jump strut was also found to be essentially independent of the pneumatic supply pressure and was only slightly affected by control valve open time within the range of the parameters examined.

Eppel, Joseph C.↗
NASA NTRS1994

Flight investigation of the use of a nose gear jump strut to reduce takeoff ground roll distance of STOL aircraft

A series of flight tests was conducted to evaluate the reduction of takeoff ground roll distance obtainable from a rapid extension of the nose gear strut. The NASA Quiet Short-haul Research Aircraft (QSRA) used for this investigation is a transport-size short takeoff and landing (STOL) research vehicle with a slightly swept wing that employs the upper surface blowing (USB) concept to attain the high lift levels required for its low speed, short-field performance. Minor modifications to the conventional nose gear assembly and the addition of a high pressure pneumatic system and a control system provided the extendible nose gear, or 'jump strut,' capability. The limited flight test program explored the effects of thrust-to-weight ratio, storage tank initial pressure, and control valve open time duration on the ground roll distance. The data show that the predicted reduction of takeoff ground roll on the order of 10 percent was achieved with the use of the jump strut. Takeoff performance with the jump strut was also found to be essentially independent of the pneumatic supply pressure and was only slightly affected by control valve open time within the range of the parameters examined.

Eppel, Joseph C.↗
NASA NTRS1993

Weld joint concepts for on-orbit repair of Space Station Freedom fluid system tube assemblies

Because Space Station Freedom (SSF) is an independent satellite, not depending upon another spacecraft for power, attitude control, or thermal regulation, it has a variety of tubular, fluid-carrying assemblies on-board. The systems of interest in this analysis provide breathing air (oxygen and nitrogen), a working fluid (two-phase anhydrous ammonia) for thermal control, and a monopropellant (hydrazine) for station reboost. The tube assemblies run both internally and externally with respect to the habitats. They are found in up to 50 ft. continuous lengths constructed of mostly AISI 316L stainless steel tubing, but also including some Inconel 625 nickel-iron and Monel 400 nickel-copper alloy tubing. The outer diameters (OD) of the tubes range from 0.25-1.25 inches, and the wall thickness between 0.028-.095 inches. The system operational pressures range from 377 psi (for the thermal control system) to 3400 psi (for the high pressure oxygen and nitrogen supply lines in the ECLSS). SSF is designed for a fifteen to thirty year mission. It is likely that the tubular assemblies (TA's) will sustain damage or fail during this lifetime such that they require repair or replacement. The nature of the damage will be combinations of punctures, chips, scratches, and creases and may be cosmetic or actually leaking. The causes of these hypothetical problems are postulated to be: (1) faulty or fatigued fluid joints--both QD's and butt-welds; (2) micro-meteoroid impacts; (3) collison with another man-made object; and (4) over-pressure strain or burst (system origin). While the current NASA baseline may be to temporarily patch the lines by clamping metal c-sections over the defect, and then perform high pressure injection of a sealing compound, it is clear that permanent repair of the line(s) is necessary. This permanent repair could be to replace the entire TA in the segment, or perhaps the segment itself, both alternatives being extremely expensive and risky. The former would likely require extensive EVA to release TA clamps and pose great risk to other engineering subsystems, and the latter would require major de-servicing of the Station.

Jolly, Steven D.↗
NASA NTRS1973

A closed-loop automatic control system for high-intensity acoustic test systems.

Sound at sound pressure levels in the range from 130 to 160 dB is used in the investigation. Random noise is passed through a series of parallel filters, generally 1/3-octave wide. A basic automatic system is investigated because of preadjustment inaccuracies and high costs found in a study of a typical manually controlled acoustic testing system. The unit described has been successfully used in automatic acoustic tests in connection with the spacecraft tests for the Mariner 1971 program.

Slusser, R. A.↗
NASA NTRS1979

Design and performance of the propulsion system for the quiet short-haul research aircraft /QSRA/

This paper describes the design and performance of the Quiet Short-Haul Research Aircraft (QSRA) propulsion system. A discussion of the mixed-flow boundary layer control (BLC) system, which uses high and low pressure engine bleed air, is included. This system seriously affected propulsion system performance, particularly engine acceleration characteristics, requiring an integration of BLC system and powerplant controls. Funding limitations for the QSRA Project prevented extensive full-scale testing and systems mockups, resulting in a high reliance on small-scale tests and analytical techniques. Ground tests of the actual aircraft systems showed that the extrapolation of small-scale tests and analytical techniques were in good agreement with measured full-scale results.

Shovlin, M. D.↗
NASA NTRS1982

CF6 Jet Engine Performance Improvement: High Pressure Turbine Active Clearance Control

An active clearance control system was developed which reduces fuel consumption and performance degradation. This system utilizes compressor discharge air during takeoff and fan discharge air during cruise to impinge on the shroud structure to improve the thermal response. The system was evaluated in component and engine tests. The test results demonstrated a performance improvement of 0.7 percent in cruise SFC.

Rich, S. E.↗
NASA NTRS2004

Multi-Element Unstructured Analyses of Complex Valve Systems

The safe and reliable operation of high pressure test stands for rocket engine and component testing places an increased emphasis on the performance of control valves and flow metering devices. In this paper, we will present a series of high fidelity computational analyses of systems ranging from cryogenic control valves and pressure regulator systems to cavitating venturis that are used to support rocket engine and component testing at NASA Stennis Space Center. A generalized multi-element framework with sub-models for grid adaption, grid movement and multi-phase flow dynamics has been used to carry out the simulations. Such a framework provides the flexibility of resolving the structural and functional complexities that are typically associated with valve-based high pressure feed systems and have been difficult to deal with traditional CFD methods. Our simulations revealed a rich variety of flow phenomena such as secondary flow patterns, hydrodynamic instabilities, fluctuating vapor pockets etc. In the paper, we will discuss performance losses related to cryogenic control valves, and provide insight into the physics of the dominant multi-phase fluid transport phenomena that are responsible for the choking like behavior in cryogenic control elements. Additionally, we will provide detailed analyses of the modal instability that is observed in the operation of the dome pressure regulator valve. Such instabilities are usually not localized and manifest themselves as a system wide phenomena leading to an undesirable chatter at high flow conditions.

Sulyma, Peter↗
NASA NTRS2005

Adaptive Development

The goal of this research is to develop and demonstrate innovative adaptive seal technologies that can lead to dramatic improvements in engine performance, life, range, and emissions, and enhance operability for next generation gas turbine engines. This work is concentrated on the development of self-adaptive clearance control systems for gas turbine engines. Researchers have targeted the high-pressure turbine (HPT) blade tip seal location for following reasons: Current active clearance control (ACC) systems (e.g., thermal case-cooling schemes) cannot respond to blade tip clearance changes due to mechanical, thermal, and aerodynamic loads. As such they are prone to wear due to the required tight running clearances during operation. Blade tip seal wear (increased clearances) reduces engine efficiency, performance, and service life. Adaptive sealing technology research has inherent impact on all envisioned 21st century propulsion systems (e.g. distributed vectored, hybrid and electric drive propulsion concepts).

Source record↗
NASA NTRS2017

Work Experience Report

The NASA Platform for Autonomous Systems (NPAS) toolkit is currently being used at the NASA John C. Stennis Space Center (SSC) to develop the INSIGHT program, which will autonomously monitor and control the Nitrogen System of the High Pressure Gas Facility (HPGF) on site. The INSIGHT program is in need of generic timing capabilities in order to perform timing based actions such as pump usage timing and sequence step timing. The purpose of this project was to develop a timing module that could fulfill these requirements and be adaptable for expanded use in the future. The code was written in Gensym G2 software platform, the same as INSIGHT, and was written generically to ensure compatibility with any G2 program. Currently, the module has two timing capabilities, a stopwatch function and a countdown function. Although the module has gone through some functionality testing, actual integration of the module into NPAS and the INSIGHT program is contingent on the module passing later checks.

Guo, Daniel↗
NASA NTRS2005

System-Level Design of a Shape Memory Alloy Actuator for Active Clearance Control in the High-Pressure Turbine

This paper describes results of a numerical analysis evaluating the feasibility of high-temperature shape memory alloys (HTSMA) for active clearance control actuation in the high-pressure turbine section of a modern turbofan engine. The prototype actuator concept considered here consists of parallel HTSMA wires attached to the shroud that is located on the exterior of the turbine case. A transient model of an HTSMA actuator was used to evaluate active clearance control at various operating points in a test bed aircraft engine simulation. For the engine under consideration, each actuator must be designed to counteract loads from 380 to 2000 lbf and displace at least 0.033 inches. Design results show that an actuator comprised of 10 wires 2 inches in length is adequate for control at critical engine operating points and still exhibits acceptable failsafe operability and cycle life. A proportional-integral-derivative (PID) controller with integrator windup protection was implemented to control clearance amidst engine transients during a normal mission. Simulation results show that the control system exhibits minimal variability in clearance control performance across the operating envelope. The final actuator design is sufficiently small to fit within the limited space outside the high-pressure turbine case and is shown to consume only small amounts of bleed air to adequately regulate temperature.

DeCastro, Jonathan A.↗
NASA NTRS1990

Experimental characterization of the effects of pneumatic tubing on unsteady pressure measurements

Advances in aircraft control system designs have, with increasing frequency, required that air data be used as flight control feedback. This condition requires that these data be measured with accuracy and high fidelity. Most air data information is provided by pneumatic pressure measuring sensors. Typically unsteady pressure data provided by pneumatic sensing systems are distorted at high frequencies. The distortion is a result of the pressure being transmitted to the pressure sensor through a length of connective tubing. The pressure is distorted by frictional damping and wave reflection. As a result, air data provided all-flush, pneumatically sensed air data systems may not meet the frequency response requirements necessary for flight control augmentation. Both lab and flight test were performed at NASA-Ames to investigate the effects of this high frequency distortion in remotely located pressure measurement systems. Good qualitative agreement between lab and flight data are demonstrated. Results from these tests are used to describe the effects of pneumatic distortion in terms of a simple parametric model.

Whitmore, Stephen A.↗
NASA NTRS2022

XSP Methane Sensors Test and Evaluation Project “M-Step”

Methane sensor technology is employed in industry sectors from oil and gas to agriculture, landfills, and monitoring of natural emissions. The US oil and gas sector is extensive in scale, critical to fulfilling US energy needs, and deals with commodities presenting enormous challenges for personnel safety and the environment. Thus, it is imperative that they have accurate and responsive sensors to detect hazardous gases such as methane. US space launch systems will increasingly also use liquefied methane and liquefied natural gas (LNG), which is mostly methane, in quantities large and small, as main and auxiliary propulsion and power. Some of these systems will be reusable, which adds the unique challenge of processing a vehicle that has residual commodities and has returned to its launch site to be readied for its next launch. The methane sensors test and evaluation project (M-STEP) began within the context of a reusable launch system, the Defense Advanced Research Projects Agency (DARPA) Experimental Spaceplane (XSP) program, which would have employed a high-pressure gaseous methane and gaseous oxygen reaction control system. Although the XSP partnership between Boeing and DARPA was terminated by Boeing in early 2020, DARPA and KSC have continued to collaborate in the area of gas sensors with the hydrogen sensor test and evaluation project (H-STEP) and with M-STEP. The NASA Launch Services program (LSP) invested in M-STEP in FY 2021 “to evaluate and understand the state-of-the-art in methane gas sensors”. M-STEP and the LSP effort was complementary, pushing in the same direction to understand US launch system stakeholder needs and approaches, requirements internal (NASA) and external, and commercially available or forthcoming methane sensing technologies, practices, and approaches. In addition, M-STEP (as with H-STEP) enhances KSC capabilities and understanding of these technologies, informing agency investments and further research in these areas.

Tracy L. Gibson↗
NASA NTRS1972

Study of low gravity propellant transfer

The results are presented of a program to perform an analytical assessment of potential methods for replenishing the auxiliary propulsion, fuel cell and life support cryogens which may be aboard an orbiting space station. The fluids involved are cryogenic H2, O2, and N2. A complete transfer system was taken to consist of supply storage, transfer, and receiver tank fluid conditioning (pressure and temperature control). In terms of supply storage, the basic systems considered were high pressure (greater than critical), intermediate pressure (less than critical), and modular (transfer of the tanks). Significant findings are included.

Source record↗
NASA NTRS1992

Cryogenic leak testing of tube fittings/valves

A high pressure and variable temperature cryogenic leak testing system was conceived and designed in order to conduct leakage testing of pipe fittings/valves in liquid hydrogen supply lines of the Space Shuttle. The system can create a continuous testing environment of variable temperature, 5.5 to about 300 K, and variable pressure, 0.01 to about 70 x 10 exp 5 Pa, with a large sample space, 90 mm diameter x 228 mm length, and at low operating cost. In terms of cryogenic leak testing the system has a special capability for extensive applications. The system comprised a variable temperature cryostat, a high pressure sample chamber, a vacuum pumping station, gas flow control system, pressure and temperature control systems, and leak detecting and measuring systems. A general discussion of cryogenic leak testing methods is also presented.

Jia, L. X.↗
NASA NTRS1990

ECLS resupply for Space Station Freedom

The design of logistics carriers is presented emphasizing the use of cost-effective pressurized and nonpressurized versions to resupply consumable fluids and provide on-orbit support for the Space Station Freedom. The requirements for the Environmental Control and Life Support (ECLS) system include high-pressure oxygen and nitrogen as well as consumables that do not require pressurization. The nominal and contingency requirements are given for logistics carriers designed to support various mission scenarios by resupplying and servicing fluid systems on-orbit. The resulting design overview for the logistics carriers describes the cryogenic-nitrogen storage during launch and operation of the unpressurized version and the flexible payload-support capacity of the pressurized version. The carriers are characterized as lightweight and versatile, and the resupply of cryogenic nitrogen is a flight-proven capability.

Higginbotham, Keith↗
NASA NTRS1995

Spectral Changes in Metal Halide and High-pressure Sodium Lamps Equipped with Electronic Dimming

Electronic dimming of high-intensity discharge lamps offers control of photosynthetic photon flux (PPF) but is often characterized as causing significant spectral changes. Growth chambers with 400-W metal halide (MH) and high-pressure sodium (HPS) lamps were equipped with a dimmer system using silicon-controlled rectifiers (SCR) as high-speed switches. Phase control operation turned the line power off for some period of the alternating current cycle. At full power, the electrical input to HPS and MH lamps was 480 W (root mean squared) and could be decreased to 267 W and 428 W, respectively, before the arc was extinguished. Concomitant with this decrease in input power, PPF decreased by 60% in HPS and 50% in MH. The HPS lamp has characteristic spectral peaks at 589 and 595 nm. As power to the HPS lamps was decreased, the 589-nm peak remained constant while the 595-nm peak decreased, equaling the 589-nm peak at 345-W input, and the 589-nm peak was almost absent at 270-W input. The MH lamp has a broader spectral output but also has a peak at 589 nm and another smaller peak at 545 nm. As input power to the MH lamps decreased, the peak at 589 diminished to equal the 545-nm peak. As input power approached 428 W, the 589-nm peak shifted to 570 nm. While the spectrum changed as input power was decreased in the MH and HPS lamps, the phytochrome equilibrium ratio (P(sub fr):P(sub tot)) remains unchanged for both lamp types.

Bubenheim, David L.↗
NASA NTRS1995

Spectral Changes in Metal Halide and High-Pressure Sodium Lamps Equipped with Electronic Dimming

Electronic dimming of high-intensity discharge lamps offers control of Photosynthetic Photon Flux (PPF) but is often characterized as causing significant spectral changes. Growth chambers with 400-W Metal Halide (MH) and High-Pressure Sodium (HPS) lamps were equipped with a dimmer system using Silicon-Controlled Rectifiers (SCR) as high-speed switches. Phase control operation turned the line power off for some period of the alternating current cycle. At full power, the electrical input to HPS and MH lamps was 480 W (root mean squared) and could be decreased to 267 W and 428 W, respectively, before the arc was extinguished. Concomitant with this decrease in input power, PPF decreased by 60% in HPS and 50% in MH. The HPS lamp has characteristic spectral peaks at 589 and 595 nm. As power to the HPS lamps was decreased, the 589-nm peak remained constant while the 595-nm peak decreased, equaling the 589-nm peak at 345-W input, and 589-nm peak was almost absent at 270-W input. The MH lamp has a broader spectral output but also has a peak at 589 nm and another smaller peak at 545 nm. As input power approached 428 W, the 589-nm peak shifted to 570 nm. While the spectrum changed as input power was decreased in the MH and HPS lamps, the phytochrome equilibrium ratio (P(sub ft):P(sub tot)) remains unchanged for both lamp types.

Bubenheim, David L.↗
NASA NTRS2007

Active Control of Flow Separation on a High-Lift System with Slotted Flap at High Reynolds Number

The NASA Energy Efficient Transport (EET) airfoil was tested at NASA Langley's Low- Turbulence Pressure Tunnel (LTPT) to assess the effectiveness of distributed Active Flow Control (AFC) concepts on a high-lift system at flight scale Reynolds numbers for a medium-sized transport. The test results indicate presence of strong Reynolds number effects on the high-lift system with the AFC operational, implying the importance of flight-scale testing for implementation of such systems during design of future flight vehicles with AFC. This paper describes the wind tunnel test results obtained at the LTPT for the EET high-lift system for various AFC concepts examined on this airfoil.

Khodadoust, Abdollah↗