Showing papers on "Chamber pressure published in 2001"

Microfabrication of a high pressure bipropellant rocket engine

Abstract: A high pressure bipropellant rocket engine has been successfully micromanufactured by fusion bonding a stack of six individually etched single crystal silicon wafers. In order to test the device, an innovative packaging technique was developed to deliver liquid coolant and gaseous propellants to the rocket chip at pressures in excess of 200 atm at temperatures above 300°C. Testing continues on the 1.2 g devices, which have been run to date at a chamber pressure of 12 atm, generating 1 N of thrust, and delivering a thrust power of 750 W.

Chamber pressure state-based control for a reactor

Abstract: A process chamber containing a substrate has at least one process gas introduced for reacting with a surface of the substrate to form a layer on the substrate. The gas creates a certain pressure in the chamber. At a certain time, the gas is expelled to end the reaction, and the gas pressure is reduced. The detection of the change in pressure in said chamber automatically controls valves to supply a second gas into the chamber to further react with the surface of the substrate.

High-Pressure Bipropellant Microrocket Engine

Abstract: The development of high-aspect-ratio, high-precision micromachining in silicon or silicon carbide suggests the feasibility of microfabricated, high-chamber-pressure chemical rocket engines. With high-speed turbopumps and valvesincorporatedontotherocketchip,anumberofpropulsioncyclesarepossible.Suchanengine,approximately 20 ££ 15 £ 3 mm in size, operating at a 125-atm chamberpressure, would produceabout 15 N of thrust using 300-s Isp propellants at a thrust-to-weight ratio of 1000:1. The feasibility of these engines has been investigated, and a liquid-cooled, pressure-fed thrust chamber and nozzle have been successfully designed, fabricated, and operated at a 12.5-atm chamber pressure to further evaluate the concept.

Study on ice slurry production by water spray

Abstract: A theoretical and experimental study was performed to examine the water spray method of ice slurry production. First, the conditions for the formation of ice particles were investigated theoretically by the diffusion-controlled evaporation model. The prediction of the model was proved to agree relatively well with experiments in which we examined the conditions for a droplet of initial temperature 20°C and size 50 μm to change into an ice particle in a chamber of height 1.33 m. Second, the production of cold storage heat will increase almost proportionally to the number of spray nozzles because no substantial difference was found in the Sauter Mean Diameter (SMD) of sprays from single and twin nozzle. Third, an ice slurry was experimentally obtained by spraying droplets of 7% ethylene glycol aqueous solution in a vacuum chamber where pressure is maintained below the freezing point of the solution. Finally, based on the theoretical and experimental results, we propose an optimizing chart for providing the operating conditions to make ice slurry using the relations of the staying time of the droplet in the chamber, the injection pressure, the spray droplet size and the chamber pressure.

Air-in-line and pressure detection

Abstract: Methods and apparatus for air content and pressure measurement of sample fluid, especially sample fluid in association with an infusion pump. Volume change in a chamber as the chamber transitions between negative and positive pressure relates to the air content in the chamber. In particular, in an infusion pump, the volume change of infusion fluid as it transitions between being under negative pressure and positive pressure within a cassette central chamber, e.g., pumping chamber, relates to the air content in the infusion fluid. The outlet pressure of the cassette central chamber, e.g., blood pressure, can be monitored based on the cassette central chamber pressure.

Lift pin alignment and operation methods and apparatus

Abstract: A lifting mechanism includes a plurality of lift pins which may be driven separately and independently upward to engage an alignment surface of the chamber using ambient atmospheric pressure as the chamber is evacuated by a pump. In the illustrated embodiment, each lift pin includes a piston which is exposed to the internal chamber pressure on one side of the piston, and is exposed to the external ambient pressure on the other side of the piston. As the pump evacuates the chamber, the internal chamber pressure decreases, causing each lift pin piston to drive the associated lift pin upward. Once all the lift pins have securely engaged the alignment surface, the lift pins may be clamped to a linking mechanism to permit a motor to actuate the lift pins during processing operations.

Valve timing adjusting device for internal combustion engine

Abstract: It is an object to provide a continuously variable valve timing adjusting device to improve valve timing advance response for an internal combustion engine. The device, capable of continuously and variably controlling the intake valve timing phase, includes: an advance chamber which hydraulically rotates a vane rotor and a camshaft on the advance side relative to the timing rotor; a retard chamber for rotating the camshaft on the retard side relative to the timing rotor; an advance-retard oil pressure control valve; an oil communicating passage for fluid communication between the advance chamber and the retard chamber; a hydraulic piston, flow control valve which controls the oil in the communicating passage according to the retard chamber pressure when the engine is running at a low speed and a high oil temperature; and a ball valve check valve which checks the oil flow from the advance chamber to the retard chamber.

Manipulating biological samples for environmental scanning electron microscopy observation

Abstract: Biological samples having different characteristics were observed by environmental scanning electron microscopy (ESEM). The environmental conditions for untreated biological samples was determined by optimizing sample temperature and chamber pressure. When the temperature was at 4 degrees - 6 degrees C and chamber pressure was 5.2-5.9 Torr, the relative humidity in the specimen chamber was about 85%. Under these conditions, the surface features of the sample were completely exposed and did not exhibit charging. The images obtained from the untreated samples at different ESEM conditions were also compared with fixed and coated samples observed under high vacuum.

Dry etch release of MEMS structures

Abstract: The present invention pertains to a method of fabricating a surface within a MEM which is free moving in response to stimulation. The free moving surface is fabricated in a series of steps which includes a release method, where release is accomplished by a plasmaless etching of a sacrificial layer material. An etch step is followed by a cleaning step in which by-products from the etch step are removed along with other contaminants which may lead to stiction. There are a series of etch and then clean steps so that a number of “cycles” of these steps are performed. Between each etch step and each clean step, the process chamber pressure is typically abruptly lowered, to create turbulence and aid in the removal of particulates which are evacuated from the structure surface and the process chamber by the pumping action during lowering of the chamber pressure. The final etch/clean cycle may be followed by a surface passivation step in which cleaned surfaces are passivated and/or coated.

Interaction of Acoustic Waves with a Cryogenic Nitrogen Jet at Sub- and Supercritical Pressures

Abstract: : To better understand the nature of the interaction between acoustic waves and liquid fuel jets in rocket engines, cryogenic liquid nitrogen is injected into a room temperature high-pressure chamber having optical access on its sides. A piezo-siren capable of generating sound waves with an SPL of up to 180 dB is used under three chamber pressures of 1.46, 2.48, and 4.86 MPa. The reduced pressures for these pressures are 0.43 (subcritical), 0.73 (near-critical), and 1.43 (supercritical), respectively. The assembly consisting of the acoustic driver and the high- pressure chamber form a cavity that resonates at several frequencies, the strongest being at 2700 and 4800 Hz. Three different flow rates are considered and the nature of the aforementioned interaction has been documented via a high-speed imaging system using a CCD camera. It is found that the impact of the acoustic waves on the jet structure is strongest from low to near-critical chamber pressures and at low injectant flow rates. No significant effects of the acoustic waves are detected at the supercritical chamber pressure examined. It suggests that engine operation either near the critical point or in transition passing through the critical point could be troublesome and may lead to or feed combustion instabilities in liquid rocket engines. Further work is needed to directly relate these effects to the observed instabilities.

Combination differential and absolute pressure transducer for load lock control

Abstract: Transducer apparatus and method combining both an absolute pressure sensor for sensing absolute pressure in the load lock chamber and a differential pressure sensor for sensing a pressure difference between ambient atmospheric pressure and pressure in a load lock chamber and provides control signals for opening an interior door from the load lock chamber into a vacuum processing chamber and for opening an exterior door between ambient atmosphere and the load lock chamber. The transducer can also produce signals to control transition from slow to fast vacuum pump-down of load lock chamber pressure at a predetermined pressure set point.

Study of the structure and deviation from equilibrium in direct current supersonic plasma jets

Abstract: Mathematical modelling and optical emission spectroscopy are applied to study the effect of the chamber pressure on the structure and properties of supersonic plasma jets formed by a direct current arc. In this installation the plasma is created inside the nozzle where the flow is accelerated. As a result some deviation from thermal and ionization equilibrium can be found, even at the working chamber inlet. In this paper, by means of a two-temperature model, we study the argon jet flow using the data of the emission spectroscopy measurements to make realistic assumptions about the inlet boundary conditions. The results show that, when the chamber pressure is low, a strongly underexpanded jet with a Mach disc is formed. For the higher ambient pressure values, the core region of the jet changes to a mildly underexpanded structure with alternating oblique expansion and compression zones. The predicted shock zone positions are in a very good agreement with measurement. The general analysis shows that the deviation from local thermodynamic equilibrium in the jet is inversely related to the chamber pressure. Along the jet core the deviation from thermal equilibrium is less in the shock regions than in the expansion zones, where the electrons are heated by three-particle recombination. Downstream of the jet core the velocity drops, but the ionization and thermal equilibria are not attained because of the correlation between the characteristic recombination and the hydrodynamic times. Both the modelling and the emission spectroscopy show that the axial electron number density is much closer to its frozen value than to equilibrium value. The results obtained are helpful for different applications such as plasma processing, rocket propulsion systems and the simulation of re-entry conditions.

Effect of chamber pressure and atmosphere on the microstructure and nanomechanical properties of amorphous carbon films prepared by pulsed laser deposition

Abstract: We have investigated the effect of chamber pressure and atmosphere on the microstructure and nanomechanical properties of amorphous carbon thin films prepared by pulsed laser deposition. The amorphous carbon films were deposited in various atmospheres such as nitrogen and argon at different chamber pressures. We used Raman spectroscopy to study the bonding characteristics of the deposited amorphous carbon films. Atomic force microscopy and optical microscopy were utilized to observe the surface conditions and the microstructures of the deposited films. Nanoindentation measurements were carried out on various samples prepared under different conditions to study the effect of chamber pressure and atmosphere on the elastic modulus and nanohardness of the films. It was found that reduced vacuum leads to formation of amorphous carbon films with reduced elastic modulus and nanohardness. Amorphous carbon films prepared under higher chamber pressures exhibit an increased density of particulates and significantly ...

The effect of carrier gas pressure and wall heating on the operation of the thermal diffusion cloud chamber

Abstract: Experimental observations indicate that the nucleation behavior within the thermal diffusion cloud chamber (TDCC) changes with increasing carrier gas pressure and applied sidewall heating, even though such an effect is not predicted by typical nucleation theories and it is not seen in typical expansion-based nucleation studies. In this work we present a model of the chamber which shows that both of these effects are likely due to buoyancy-induced convection within the TDCC. As the chamber pressure is increased, the calculated critical supersaturation within the chamber decreases. Results from a simple model of the chamber wall heating are also presented. Previously, it was argued that unheated chamber walls result in a significant, radial concentration gradient which lowers the vapor concentration and condensation flux within the chamber center. In contrast, we show that this reduction is due primarily to a convective flow induced by the sidewall concentration gradient. The model has been applied to recent experimental data for n-pentanol. Results indicate that, with respect to buoyancy-induced convection, the typical 1D model should be regarded as an upper limit to the maximum attainable supersaturation within the chamber.

Etching characteristics and plasma-induced damage of high-k Ba0.5Sr0.5TiO3 thin-film capacitors

Abstract: The inductively coupled plasma (ICP) etching behavior of Ba05Sr05TiO3 (BST) thin films has been characterized with Cl2/Ar gas mixtures by varying the process parameters such as chamber pressure, ICP power, and substrate bias rf power The etching characteristics of BST were investigated in terms of etch rate, etch profile, surface residue, and electrical properties The results obtained can be further interpreted by the plasma properties (ion flux and dc bias) in situ measured by a Langmuir probe Quantitative analysis of the plasma-induced damage in the Pt/BST/Pt capacitor was attempted to discuss the mechanism of leakage current density and dielectric constant with various substrate bias rf power and ICP power levels Finally, optimization of the etch parameters for fabricating BST capacitors was performed to minimize the plasma-induced damage The optimum condition appears to be under a 30% Cl2/(Cl2+Ar) gas mixture, ICP power of 800 W, substrate bias rf power of 100 W, and chamber pressure of 067 Pa

Thermal gradient enhanced CVD deposition at low pressure

Abstract: A method wherein a thermal gradient over a substrate enhances Chemical Vapor Deposition (CVD) at low pressures. An upper heat source is positioned above the substrate and a lower heat source is positioned below the substrate. The upper and lower heat sources are operated to raise the substrate temperature to 400-700° and cause a heat gradient of 100-200° C. between the upper and lower heat sources. This heat gradient causes an increase in the deposition rate for a given reactant gas flow rate and chamber pressure. The preferred parameters for implementation of the present invention for poly crystalline silicon deposition include the temperature of the upper heat source 100-200° C. above the lower heat source, a substrate temperature in the range of 400-700° C., a reactant gas pressure between 250 and 1000 mTorr, and a gas flow rate of 200-800 sccm. The substrate is rotated, with 5 RPM being a typical rate. A deposition rate of 2000 angstroms per minute deposition of poly crystalline silicon is achieved with a 200° C. temperature differential, substrate temperature of 650° C., pressure of 250 mTorr and silane flow of 500 sccm.

Safety protection garment

Abstract: A safety protection garment which enables a user to comfortably wear it during travel, and in which the garment can be rapidly prepared for an emergency for resisting impact forces or for providing buoyancy to keep the user afloat in water. The garment has an inner lining and outer shell which are joined together to form a chamber which contains a compressible layer. The compressible layer is formed of an elastic material which resiliently expands and contracts between memory and compressed shapes. A valve device enables the user to open and close air flow into the chamber. For normal wearing, the layer is in its compressed state with air substantially evacuated from the chamber and the valve closed. To prepare for an emergency, the valve is opened so that air enters the chamber sufficient to equalize the chamber pressure with atmospheric pressure. The layer then expands to its memory shape where it resiliently resists impact forces and also provide buoyancy to keep the user afloat in water.

Unstructured Adaptive Monte Carlo Simulations of Flows in Micronozzles

Abstract: A direct simulation Monte Carlo (DSMC) coed is developed using unstructured tetrahedral grids with adaptation. The numerical code is used to simulate rarefied flows in micronozzles. The grid generation methodology and adaptation are reviewed. The simulations include cold-gas micronozzles and a MEMS-manufactured micronozzle. The results are compared with experimental data and previous DSMC computations. Introduction The growing interest of microspacecraft has caused increased need in onboard micropropulsion systems. The miniaturization of electronics and improved fabrication techniques, such as deep reactive ion etching, has enabled the manufacture of smaller propulsion devices than ever before. Micropropulsion is a mission enabling technology for microspacecraft, providing precision maneuvering and thrust at reduced sizes and weight' . This work is motivated by the increasing interest in space applications of rarefied gas and plasma dynamics, primarily in the simulation of internal flows in micropropulsion devices as well as plume flows and their interaction with spacecraft surfaces. Flows in micro thrusters exhibit distinct flow characteristics that can include transition from continuum to slip to rarefied regimes. Rarefaction effects may be a direct result of reduced spatial dimensions or operating conditions. See for example, previous work on cold-gas rnicrothrusters, the simplest available onboard propulsion device used primarily for precise station-keeping and drag nullification'. Under such conditions the use of Navier-Stokes formulations for the nozzle flow becomes questionable and even break down. Prior to MEMS manufacturing techniques, low thrust levels were achieved by running small nozzles at reduced chamber pressures . However, this regime of operation is associated with considerable viscous losses, as the Reynolds number (ratio of inertial force to viscous force) is low for these conditions. The Graduate Research Assistant. 100 Institute Rd. Student Member AIAA. ' Graduate Research Assistant. * Associate Professor. Senior Member AIAA Copyright © 2001 by the authors. Published by the American Institute of Aeronautics and Astronautics, Inc. with permission ability to manufacture micron-scale nozzles with MEMS-type fabrication techniques may reduce viscous losses for the same thrust regime, as the chamber may operate at higher pressures and the throat size is reduced. This increases thruster efficiency. In the case of plume flows, rarefaction and non-equilibrium effects occur regardless of the operating conditions of the microthruster. In certain cases rarefaction effects can persist well inside the nozzle. The modeling of micronozzle and plume flows that exhibit transition and/or non-equilibrium characteristics is achieved by modeling techniques based on kinetic descriptions of the gas or techniques that combine the continuum and kinetic approaches. The Direct Simulation Monte Carlo method (DSMC) has been proven a method capable of handling a wide range of rarefied gas flows and has been applied successfully to the characterization of flows in micronozzles.''''' A small traditionally-machined helium thruster was modeled for the purpose of obtaining precise flow characteristics desirable for complete drag nullification' . This thruster produced thrusts of the order of 1 mN, which is similar to the regime of MEMS rnicrothrusters, but a chamber pressure of only 7 Pa. Normalized mass flux and discharge coefficient compared favorably with experimental measurements. This study demonstrated the applicability of the DSMC method to the study of small nozzles for engineering purposes. The DSMC had been applied subsequently to MEMS-fabricated micronozzles. Piekos and Breuer' 11 presented 2-D DSMC calculations of a parabolic micronozzle with atmospheric chamber conditions and a vacuum at the exit. Temperature and Mach contours showed considerable slip (> M=0.5) at the exit. The performance characteristics *of MEMS nozzles were studied experimentally in a vacuum chamber and compared with 2-D Navier-Stokes results. These conical micronozzles were manufactured using deep reactive ion etching. At lower chamber pressures,

Dielectric recovery characteristics of a high current arcing gap

Abstract: Experimental measurements of the dielectric breakdown strength of an arcing gap after current zero were made to determine the effects of arc chamber venting on the reverse recovery voltage needed to break down a recovering gap. The recovery conditions applied closely matched those created in a molded case circuit breaker under power line fault conditions. Three different vent sizes were used to determine the effect of gas pressure on the recovery characteristics of the plasma with recovery time between 170 /spl mu/s to 280 /spl mu/s, and currents from 3 kA/sub p/ to 15 kA/sub p/. Larger venting, providing increased cooling of the plasma, resulted in increased breakdown strength over the full range of currents. Based on the approximation that the recovering plasma breakdown strength is inversely proportional to plasma thermal temperature, breakdown voltage values were fitted to an exponential model to obtain plasma time constants and the initial hold-off voltage. Comparing these results to curve fits of E/p values showed E/p was a more accurate representation of the data. It is proposed to use E/p values when there is significant post current-zero chamber pressure. These results could be used as a guide to predicting molded case breaker interruption performance, especially for small arc chambers and short gaps.

Aperture for linear control of vacuum chamber pressure

Abstract: The linear controlling of the pressure of a vacuum chamber, such as a plasma etch chamber used in semiconductor processing, is disclosed. A plasma etch chamber pressure control mechanism includes an aperture diaphragm and a number of aperture blades rotatably mounted on the aperture diaphragm. The diaphragm defines a contractible and expandable aperture for controlling the pressure of the chamber. Rotation of the aperture blades in a first direction contracts the aperture by causing movement of the blades towards the aperture, increasing the pressure of the chamber. Rotation of the aperture blades in a second direction opposite to the first direction expands the aperture by causing movement of the blades away from the aperture, decreasing the pressure of the chamber.

Methods of fabricating capacitors including Ta2O5 layers in a chamber including changing a Ta2O5 layer to heater separation or chamber pressure

Abstract: Methods of forming Ta2O5 layers in a process chamber are disclosed. A Ta2O5 layer can be maintained at a first temperature that is less than a temperature for crystallization of the Ta2O5 layer. At least one of a position of the Ta2O5 layer in the process chamber relative to the heater and a pressure in the process chamber is changed to increase the temperature of the Ta2O5 layer to about the temperature for crystallization.

Method and apparatus for increased workpiece throughput

Abstract: A method is disclosed for speeding workpiece thoughput in a low pressure, high temperature semiconductor processing reactor. The method includes loading (100, 200) a workpiece into a chamber at atmospheric pressure, bringing the chamber down to an intermediate pressure (110, 210, 225), and heating the wafer while under the intermediate pressure (115, 230). The chamber is then pumped down to the operating pressure (125, 235). The preferred embodiments involve single wafer plasma ashers, where a wafer is loaded (100) onto lift pins at a position above a wafer chuck, the pressure is rapidly pumped down (110) to about 40 Torr by rapidly opening and closing an isolation valve, and the wafer is simultaneously lowered (115) to the heated chuck. Alternatively, the wafer can be pre-processed to remove (220) an implanted photoresist crust at a first temperature and the chamber then backfilled (225) to about 40 Torr for further heating (230) to close to the chuck temperature. At 40 Torr, the heat transfer from the chuck to the wafer is relatively fast, but still slow enough to avoid thermal shock. In the interim, the pump line is further pumped down to operating pressure (about 1 Torr) behind the isolation valve. The chamber pressure is then again reduced (235) by opening the isolation valve, and the wafer is processed (240).

Use of plasma impedance monitoring for the determination of SF6 reactive ion etch process end points in a SiO2/Si system

Abstract: It is shown here that plasma impedance monitoring can be used successfully to determine the end point of reactive ion etching of a SiO2 layer lying on a Si substrate in SF6 plasma. The usefulness of this technique is demonstrated using a commercial Plasma Impedance Monitoring (PIM) system. The end point conditions are tested by monitoring changes in the fundamental and the first four harmonic components of the RF current, RF voltage, phase between RF voltage and current, RF discharge power and RF impedance. The best process monitoring parameter found in this work is modeled as a polynomial equation of RF input power, chamber pressure and gas flow rate, from which the end point can be predicted with good precision and easily detected by the PIM. The end point conditions are confirmed by both Fourier Transform Infrared Spectroscopy (FTIR) measurements and via observation of plasma color changes.

Method of calibrating brake servo motor for vehicle, involves determining master cylinder and servo chamber pressure values for set functioning points of servomotor

Abstract: The method of calibrating a pneumatic brake servo for a motor vehicle involves measuring and storing the pressure values (Pmc) for the hydraulic master cylinder (16) outlet and the vacuum in the working chamber (26) of the servomotor (14), for several functioning points of the servomotor, for a given vacuum pressure value in the servomotor vacuum chamber (24). This allows precise determination of the coordinates of the saturation point for control of the brakes.

Parametric Study of the Swirler/Venturi Spray Injectors

Abstract: An experimental parametric study is carried out to characterize the spray from swirler/venturi injectors (SVIs) insidea steady-e owpressurechamber. In this study,venturi tubeswith diffuseranglesof 20, 40, 60, and 80 deg and different throat lengths are combined with different swirlers with vane angles of 30, 45, and 60 deg to investigate their combined effect on spray structure. The ambient pressure conditions inside the chamber were varied from 0.1 to 0.4 MPa to simulate the relevant gas turbine density and momentum condition. For simplicity, water is used to present liquid fuel. Focusing on the spray atomization and dispersion aspects, laser diagnostic techniques are used to characterize the isothermal spray structure, including phase Doppler particle analyzer and copper-vapor laser-sheet visualization. Pressure drop across the SVI is also measured. It was found that the pressure drop and droplet size are dominated by the throat velocity, but are modie ed signie cantly by the divergent angle, throat length, and swirler. It is also shown that matching the correct swirler with the venturi geometry is important to obtain optimal liquid atomization and droplet distribution.

ESEM observation for biological samples

Abstract: Biological samples with different characteristics were observed in the environmental scanning electron microscope (ESEM) The optimal environmental condition for untreated biological samples is determined by changing the combination of the sample temperature and chamber pressure When the temperature is at 4～6℃ and chamber pressure at 6 93 ×10 2Pa～7 86×10 2Pa respectively, the relative humidity in the specimen chamber is about 85%, the sample surface can be shown completely exposed without water covering and dehydration, nor obvious postmortem change and charging artifact The handling methods for different sample types and the future application of ESEM are also discussed

Safety device for an air-conditioning compressor

Abstract: The invention relates to a safety device for limiting the pressure of a compressor that operates with variable stroke or variable displacement. The tilt of the wobble plate or the swash plate is varied at least by the difference between the high pressure in the discharge pressure zone (11) and the driving chamber pressure (16), optionally by the difference between the driving chamber pressure and the suction pressure. The safety device is provided with a supply connection between the discharge pressure zone (11) and the driving chamber pressure (16), with a valve device disposed in said supply connection, and optionally with a bypass throttle.

Fastrac Gas Generator Testing

Abstract: A rocket engine gas generator component development test was recently conducted at the Marshall Space Flight Center. This gas generator is intended to power a rocket engine turbopump by the combustion of Lox and RP-1. The testing demonstrated design requirements for start sequence, wall compatibility, performance, and stable combustion. During testing the gas generator injector was modified to improve distribution of outer wall coolant and the igniter boss was modified to investigate the use of a pyrotechnic igniter. Expected chamber pressure oscillations at longitudinal acoustic mode were measured for three different chamber lengths tested. High amplitude discrete oscillations resulted in the chamber-alone configurations when chamber acoustic modes coupled with feed-system acoustics modes. For the full gas generator configuration, which included a turbine inlet manifold, high amplitude oscillations occurred only at off-design very low power levels. This testing led to a successful gas generator design for the Fastrac 60,000 lb thrust engine.