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At least 793 records · Page 44
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Convective Vortices and Dust Devils Detected and Characterized by Mars 2020

Abstract We characterize vortex and dust devils (DDs) at Jezero from pressure and winds obtained with the Mars Environmental Dynamics Analyzer (MEDA) instrument on Mars 2020 over 415 Martian days (sols) ( Ls = 6°–213°). Vortices are abundant (4.9 per sol with pressure drops >0.5 Pa correcting from gaps in coverage) and they peak at noon. At least one in every five vortices carries dust, and 75% of all vortices with Δ p > 2.0 Pa are dusty. Seasonal variability was small but DDs were abundant during a dust storm ( Ls = 152°–156°). Vortices are more frequent and intense over terrains with lower thermal inertia favoring high daytime surface‐to‐air temperature gradients. We fit measurements of winds and pressure during DD encounters to models of vortices. We obtain vortex diameters that range from 5 to 135 m with a mean of 20 m, and from the frequency of close encounters we estimate a DD activity of 2.0–3.0 DDs km −2 sol −1 . A comparison of MEDA observations with a Large Eddy Simulation of Jezero at Ls = 45° produces a similar result. Three 100‐m size DDs passed within 30 m of the rover from what we estimate that the activity of DDs with diameters >100 m is 0.1 DDs km −2 sol −1 , implying that dust lifting is dominated by the largest vortices in Jezero. At least one vortex had a central pressure drop of 9.0 Pa and internal winds of 25 ms −1 . The MEDA wind sensors were partially damaged during two DD encounters whose characteristics we elaborate in detail.

Hueso, R.↗
NASA NTRS1990

BASG thermomechanical pump helium 2 transfer tests

The purpose of the effort described was to perform experiments and calculations related to using a thermomechanical pump in the space-based resupply of the Space Infrared Telescope Facility (SIRTF) with Helium 2. Thermomechanical (fountain effect) pumps have long been suggested as a means for pumping large quantities of Helium 2. The unique properties of Helium 2 have made it useful for cooling space instruments. Several space science missions, including SIRTF, are now being planned which would benefit greatly from on-orbit resupply of Helium 2. A series of experiments were performed to demonstrate that large volumes of Helium 2 can be transferred with a thermomechanical pump at high flow rates and at high efficiency from one dewar to another through valves and lines that are similar to the plumbing arrangement that would be necessary to accomplish such a transfer on-orbit. In addition, temperature, pressure, and flow rate data taken during the tests were used to verify and refine a computer model which was developed.

Mills, G. L.↗
NASA NTRS1991

Flight experiments measuring boundary-layer disturbances in laminar flow and correlation with stability analysis

Flight test results are reported from an experiment designed to study the detailed growth of disturbances in the laminar boundary layer. A gloved wing section incorporating closely-spaced flush-mounted streamwise-located instrumentation for measuring instability frequencies and amplitude growths as well as pressure distributions was used. The growth of Tollmien-Schlichting (T-S) and crossflow instabilities is predicted by the linear e exp n method and compared to the measured boundary-layer disturbance frequencies. The predictions showed good agreement with the measured data. The results exhibited fair agreement with previous n(T-S) and n(CF) flight correlations for several of the conditions analyzed. It is inferred from the high n(T-S) values for these data that moderately swept wings at compressible speeds can withstand higher combinations of n(T-S) and n(CF) values and still remain laminar than previously thought.

Lee, Cynthia C.↗
NASA NTRS2016

Mars 2020 Entry, Descent and Landing Instrumentation 2 (MEDLI2)

The Mars Entry Descent and Landing Instrumentation 2 (MEDLI2) sensor suite will measure aerodynamic, aerothermodynamic, and TPS performance during the atmospheric entry, descent, and landing phases of the Mars 2020 mission. The key objectives are to reduce design margin and prediction uncertainties for the aerothermal environments and aerodynamic database. For MEDLI2, the sensors are installed on both the heatshield and backshell, and include 7 pressure transducers, 17 thermal plugs, and 3 heat flux sensors (including a radiometer). These sensors will expand the set of measurements collected by the highly successful MEDLI suite, collecting supersonic pressure measurements on the forebody, a pressure measurement on the aftbody, direct heat flux measurements on the aftbody, a radiative heating measurement on the aftbody, and multiple near-surface thermal measurements on the thermal protection system (TPS) materials on both the forebody and aftbody. To meet the science objectives, supersonic pressure transducers and heat flux sensors are currently being developed and their qualification and calibration plans are presented. Finally, the reconstruction targets for data accuracy are presented, along with the planned methodologies for achieving the targets.

Aerodynamics↗
NASA NTRSDate not supplied

Vacuum Sealable Container (VSC) and Astronaut Lunar Drill (ALD) for Artemis

Introduction: NASA’s Artemis Program is under development to send first woman and next man to the Moon. Artemis will utilize a suite of new technology for Lunar exploration, including new space vehicles, new space suits, and new Astronaut Tools. Honeybee Robotics has been working with NASA JSC to develop a new Vacuum Sealable Container (VSC) and new Astronaut Lunar Drill (ALD) for the upcoming Artemis missions. Vacuum Sealable Container: Sample return continues to be the “Holy Grail” of space exploration, allowing for the analysis of materials using Earth-based laboratories instead of needing to miniaturize and ruggedize instrumentation for space. The Apollo missions to the Moon had several kinds of Sealable Containers which brought back Lunar samples for analysis [1]. These samples are still being analyzed, fifty years later. The VSC requirements are different from that for Apollo containers and as such, new development was required. One major difference between Artemis samples and those from Apollo is the desire to bring back volatiles which may be part of lunar regolith. The VSC is designed to withstand a high-pressure differential caused by sublimating volatiles. Because of the new, stricter sealing requirements, additional features have been added to the VSC. For example, the seal on the container is required to be more robust, thus required more force to actuate, and the seal must be locked in place with a secondary mechanism. Astronaut Lunar Drill: The ALD is designed to be a multi-functional platform for Lunar sample acquisition. The drill builds on lessons learned from the Apollo Lunar Surface Drill (ALSD), as well as Honeybee’s long history of mechanized sample acquisition devices for space [2]. The main functionality of the ALD is Deep Core Regolith Drilling. Additional functionality includes Surface Rock Coring (SRC), and GeoTech Tools (GTT). The ALD is a rotary-percussive drill designed with deep drilling in mind. The ALD is currently designed to have decoupled rotary and percussion subsystems to allow for maximum battery life and reduced fatigue on the crewmember. Honeybee drill technology will automatically engage the percussion when needed to drill at maximum efficiency. The mechanized drill stand helps improve drilling efficiency; the system utilizes advanced drilling algorithms which only require the crewmember to hold a single switch. Additionally, the stand aids in extraction of deep cores, something which was a problem on Apollo. The SRC functionality of the ALD utilizes Honeybee’s Eccentric Tube Core Breakoff technology to collect and retain rock core samples. This technology has also been infused into the Perseverance rover mission. The ALD is removable from the stand to allow crewmembers to collect samples from large boulders. Bringing back rock cores samples instead of full rocks allows for a wider variety of samples to be returned to Earth for study and puts them in a uniform form-factor for effective sealing and analysis. SRC bits will utilize the power of the drill’s percussion system to drill hard Lunar rocks and expedite sample acquisition. The mechanized stand on the ALD allows for additional attachments for taking geotechnical measurements with a Static Cone Penetrometer (SCP) and a Shear Vane (SV). With the stand, the ALD can take SCP measurements with the touch of a button, storing data for return to Earth. SV measurements utilize the ALD’s Rotary motor to spin the vanes in a controlled manner, getting clean data untampered by human error. References: [1] Bar Cohen and Zacny (2009), Drilling in Extreme Environments - Penetration and Sampling on Earth and Other Planets, Wiley. [2] Bar-Cohen and Zacny, Advances in Terrestrial and Extraterrestrial Drilling, CRC Press. [3] Myrick (2003), Core Break-off Mechanism. US Patent No. 6,550,549 Acknowledgements: This work has been supported by NASA via SBIR Phase 3.

Artemis↗
DOE OSTI2022

CO 2 laser heating system for in situ radial x-ray absorption at 16-BM-D at the Advanced Photon Source

Here we present a portable CO 2 laser heating system for in situ x-ray absorption spectroscopy (XAS) studies at 16-BM-D (High Pressure Collaborative Access Team, Advanced Photon Source, Argonne National Laboratory). Back scattering optical measurements are made possible by the implementation of a Ge beamsplitter. Optical pyrometry is conducted in the near-infrared, and our temperature measurements are free of chromatic aberration due to the implementation of the peak-scaling method and mode scrambling of the input signal. Laser power stabilization is established using electronic feedback, providing a steady power over second timescales - crucial for longer XAS collections. Examples of in situ high pressure–temperature extended x-ray absorption fine structure measurements of ZrO 2 are presented to demonstrate this new capability.

36 MATERIALS SCIENCE↗
NASA NTRS2004

High-speed Imaging of Global Surface Temperature Distributions on Hypersonic Ballistic-Range Projectiles

The NASA-Ames ballistic range provides a unique capability for aerothermodynamic testing of configurations in hypersonic, real-gas, free-flight environments. The facility can closely simulate conditions at any point along practically any trajectory of interest experienced by a spacecraft entering an atmosphere. Sub-scale models of blunt atmospheric entry vehicles are accelerated by a two-stage light-gas gun to speeds as high as 20 times the speed of sound to fly ballistic trajectories through an 24 m long vacuum-rated test section. The test-section pressure (effective altitude), the launch velocity of the model (flight Mach number), and the test-section working gas (planetary atmosphere) are independently variable. The model travels at hypersonic speeds through a quiescent test gas, creating a strong bow-shock wave and real-gas effects that closely match conditions achieved during actual atmospheric entry. The challenge with ballistic range experiments is to obtain quantitative surface measurements from a model traveling at hypersonic speeds. The models are relatively small (less than 3.8 cm in diameter), which limits the spatial resolution possible with surface mounted sensors. Furthermore, since the model is in flight, surface-mounted sensors require some form of on-board telemetry, which must survive the massive acceleration loads experienced during launch (up to 500,000 gravities). Finally, the model and any on-board instrumentation will be destroyed at the terminal wall of the range. For these reasons, optical measurement techniques are the most practical means of acquiring data. High-speed thermal imaging has been employed in the Ames ballistic range to measure global surface temperature distributions and to visualize the onset of transition to turbulent-flow on the forward regions of hypersonic blunt bodies. Both visible wavelength and infrared high-speed cameras are in use. The visible wavelength cameras are intensified CCD imagers capable of integration times as short as 2 ns. The infrared camera uses an Indium Antimonide (InSb) sensor in the 3 to 5 micron band and is capable of integration times as short as 500 ns. The projectiles are imaged nearly head-on using expendable mirrors offset slightly from the flight path. The proposed paper will discuss the application of high-speed digital imaging systems in the NASA-Ames hypersonic ballistic range, and the challenges encountered when applying these systems. Example images of the thermal radiation from the blunt nose of projectiles flying at nearly 14 times the speed of sound will be given.

Wilder, Michael C.↗
NASA NTRS1976

Modeling and analysis of the TF30-P-3 compressor system with inlet pressure distortion

Circumferential inlet distortion testing of a TF30-P-3 afterburning turbofan engine was conducted at NASA-Lewis Research Center. Pratt and Whitney Aircraft analyzed the data using its multiple segment parallel compressor model and classical compressor theory. Distortion attenuation analysis resulted in a detailed flow field calculation with good agreement between multiple segment model predictions and the test data. Sensitivity of the engine stall line to circumferential inlet distortion was calculated on the basis of parallel compressor theory to be more severe than indicated by the data. However, the calculated stall site location was in agreement with high response instrumentation measurements.

Mazzawy, R. S.↗
NASA NTRS2014

Inferred Variable FeO Content in Medium-sized Lunar Pyroclastic Deposits from LRO Diviner Data

Lunar pyroclastic deposits (LPDs) are low albedo features that mantle underlying terrain (Gaddis et al. 1985). They are high priority targets for science and exploration as they are believed to originate from and therefore reflect the composition of the deep lunar interior (NRC, 2011). They are also the best potential resource of oxygen out of any Apollo samples (Allen et al. 1996). Historically, LPDs have been divided into regional versus local categories (Gaddis et al. 2003). The large (>1000 km2 area) regional deposits are deeply sourced (>400 km deep) and result from fire fountaining. Small (<1000 km2) local deposits are thought to result from Vulcanian eruptions in which magma is slowly emplaced beneath the surface until enough volatiles exsolve and the high pressure causes an explosion. Bennett et al. (2013) identified a local deposit (674 km2 area) that may have resulted from both Vulcanian activity and fire fountaining. This deposit potentially represents a new intermediate class of LPDs that straddles the interface between the two formation mechanisms. The deposit also exhibits the highest inferred FeO wt.% of any known lunar glass. In this work we investigate the inferred FeO abundances of other medium-sized deposits to characterize this potential new class of deposits and understand the magnitude of variations in inferred FeO among pyroclastic deposits. We use the method of Greenhagen et al. (2010) to calculate the wavelength of the Christiansen Feature (CF) from Lunar Reconnaissance Orbiter Diviner Lunar Radiometer instrument thermal-infrared observations for four medium-sized deposits. From the CF values, we estimate each deposit's FeO abundance using the method of Allen et al. (2012). The four LPDs that we examined (Oppenheimer South, Beer, Cleomedes, and J. Herschel) all have average CF values from 8.22-8.28 microns, corresponding to FeO abundances of approx. 10-15 wt.%. All of these values are within the range and uncertainties of FeO abundances measured in Apollo samples. As previously identified, the Oppenheimer South deposit exhibits an area of enhanced CF values (8.49 microns) that, if the methods of Allen et al. (2012) can be extrapolated, correspond to a highest observed approx. 30 wt.% FeO. Moon Mineralogy Mapper near-infrared spectra indicate that this area is glass-rich as opposed to olivine-rich. While we are still investigating the nature of the high CF wavelength in Oppenheimer South, spatially-resolved observations there and (to a smaller degree) in our other study sites, shows that FeO wt.% can vary within LPDs. Thus, obtaining only the average FeO abundance over a large area may not be adequate to understand global variation. The magnitude of Oppenheimer South's CF variability, if due to actual surface variations rather than calibration artifacts or spectral mixing, could indicate that it is a unique deposit and not part of a new mid-sized class of deposits. The higher value could be a result of its location within the South Pole Aitken Basin and exsolution of more deeply sourced magma due to the thin crust there.

Bennett, K. A.↗
NASA NTRS1991

Measurement of tropospheric carbon monoxide using gas filter radiometers

The measurement of tropospheric carbon monoxide with gas filter radiometers is examined on the basis of the MAPS experiment. The performance characteristics of an instrument that uses the MAPS detectors, broadband filters, and gas cells in a system similar to the GASCOFIL system described by Morrow and Nicholls (1985) is determined. The signal function for two carbon monoxide channels of the MAPS instrument as it was flown in 1981 is shown. The measurements of the lower pressure channel are weighted to a higher altitude. The signal function, when integrated over altitude and multiplied by the normalization constant, yields the value of the signal. Both signal functions approach zero at the top because the gas concentration approaches zero. The present data reduction technique assumes that there are no clouds in the field of view. If clouds are present, the inferred carbon monoxide mixing ratio is too high, and those points must be rejected from the data set.

Reichle, Henry G., Jr.↗
NASA NTRS1990

Liquid Transfer Cryogenic Test Facility: Initial hydrogen and nitrogen no-vent fill data

The Liquid Transfer Cryogenic Test Facility is a versatile testbed for ground-based cryogenic fluid storage, handling, and transfer experimentation. The test rig contains two well instrumented tanks, and a third interchangeable tank, designed to accommodate liquid nitrogen or liquid hydrogen testing. The internal tank volumes are approx. 18, 5, and 1.2 cu. ft. Tank pressures can be varied from 2 to 30 psia. Preliminary no vent fill tests with nitrogen and hydrogen were successfully completed with the test rig. Initial results indicate that no vent fills of nitrogen above 90 percent full are achievable using this test configuration, in a 1-g environment, and with inlet liquid temperatures as high as 143 R, and an average tank wall temperature of nearly 300 R. This inlet temperature corresponds to a saturation pressure of 19 psia for nitrogen. Hydrogen proved considerably more difficult to transfer between tanks without venting. The highest temperature conditions resulting in a fill level greater than 90 percent were with an inlet liquid temperature of 34 R, and an estimated tank wall temperature of slightly more than 100 R. Saturation pressure for hydrogen at this inlet temperature is 10 psia. All preliminary no vent fill tests were performed with a top mounted full cone nozzle for liquid injection. The nozzle produces a 120 degree conical droplet spray at a differential pressure of 10 psi. Pressure in the receiving tank was held to less than 30 psia for all tests.

Moran, Matthew E.↗
NASA NTRS1996

Validation of UARS Microwave Limb Sounder Temperature and Pressure Measurements

The accuracy and precision of the Upper Atmosphere Research Satellite (UARS) Microwave Limb Sounder (MLS) atmospheric temperature and tangent-point pressure measurements are described. Temperatures and tangent- point pressure (atmospheric pressure at the tangent height of the field of view boresight) are retrieved from a 15-channel 63-GHz radiometer measuring O2 microwave emissions from the stratosphere and mesosphere. The Version 3 data (first public release) contains scientifically useful temperatures from 22 to 0.46 hPa. Accuracy estimates are based on instrument performance, spectroscopic uncertainty and retrieval numerics, and range from 2.1 K at 22 hPa to 4.8 K at 0.46 hPa for temperature and from 200 m (equivalent log pressure) at 10 hPa to 300 m at 0.1 hPa. Temperature accuracy is limited mainly by uncertainty in instrument characterization, and tangent-point pressure accuracy is limited mainly by the accuracy of spectroscopic parameters. Precisions are around 1 K and 100 m. Comparisons are presented among temperatures from MLS, the National Meteorological Center (NMC) stratospheric analysis and lidar stations at Table Mountain, California, Observatory of Haute Provence (OHP), France, and Goddard Spaceflight Center, Maryland. MLS temperatures tend to be 1-2 K lower than NMC and lidar, but MLS is often 5 - 10 K lower than NMC in the winter at high latitudes, especially within the northern hemisphere vortex. Winter MLS and OHP (44 deg N) lidar temperatures generally agree and tend to be lower than NMC. Problems with Version 3 MLS temperatures and tangent-point pressures are identified, but the high precision of MLS radiances will allow improvements with better algorithms planned for the future.

Fishbein, E. F.↗
NASA NTRSDate not supplied

CFD Simulations of the Truncated IHF Semi-Elliptical Nozzle Flow: Convective Calibration Plate

This paper reports computational simulations of a high-enthalpy panel test facility at NASA Ames Research Center. The recently developed facility configuration uses a truncated version of an existing semi-elliptical nozzle in the 60-MW Interaction Heating Facility, and it provides testing capability for panel test articles as large as 43.2 cm x 43.2 cm (17 in x 17 in). A water-cooled calibration plate, which is attached to the semi-elliptical nozzle bottom surface and instrumented with twenty Gardon-gage heat flux calorimeters and twelve pressure gages, is used to characterize the convective heating environment over the panel test articles. The present analysis comprises computational fluid dynamics simulations of the nonequilibrium flowfield in the facility nozzle and test box, and flowfield over panel test articles. Both laminar and turbulent simulations are performed, and the computational results are compared with the calibration plate measurements. Comparisons of computed and measured heat fluxes indicate that the boundary layer in the semi-elliptical nozzle is transitional at certain conditions (relatively higher arc-heater pressures or mass flow rates).

Arc-jets↗
NASA NTRSDate not supplied

CFD Simulations of the Truncated IHF Semi-Elliptical Nozzle Flow: Convective Calibration Plate

This paper reports computational simulations of a high-enthalpy panel test facility at NASA Ames Research Center. The recently developed facility configuration uses a truncated version of an existing semi-elliptical nozzle in the 60-MW Interaction Heating Facility, and it provides testing capability for panel test articles as large as 43.2 cm x 43.2 cm (17 in x 17 in). A water-cooled calibration plate, which is attached to the semi-elliptical nozzle bottom surface and instrumented with twenty Gardon-gage heat flux calorimeters and twelve pressure gages, is used to characterize the convective heating environment over the panel test articles. The present analysis comprises computational fluid dynamics simulations of the nonequilibrium flowfield in the facility nozzle and test box, and the flowfields over panel test articles. Both laminar and turbulent simulations are performed, and the computational results are compared with the calibration plate measurements. Comparisons of computed and measured heat fluxes indicate that the boundary layer in the semi-elliptical nozzle is transitional at certain conditions (relatively higher arc-heater pressures or mass flow rates).

Arc-jets↗
NASA NTRSDate not supplied

On Characterization of Laminar to Turbulent Transitional Flow in the Truncated IHF Semi-Elliptical Nozzle

This paper reports computational analysis and experimental data to characterize the laminar to turbulent flow transition in a high-enthalpy panel test facility at NASA Ames Research Center. The recently developed facility configuration uses a truncated version of an existing semi-elliptical nozzle in the 60-MW Interaction Heating Facility, and it provides testing capability for panel test articles as large as 43.2 cm x 43.2 cm (17 in x 17 in). A water-cooled calibration plate, which is attached to the semi-elliptical nozzle bottom surface and instrumented with twenty Gardon-gage heat flux calorimeters and twelve pressure gages, is used to characterize the convective heating environment over the panel test articles. The present analysis comprises computational fluid dynamics simulations of the nonequilibrium flowfield in the facility nozzle and test box, and the flowfields over panel test articles, and comparisons with the measured test data. Both laminar and turbulent simulations are performed. Constant current studies are performed: the measured data are grouped at the same arc current levels with varying mass flow rates, and they are compared with corresponding computations. For all currents studied, these studies indicate that the semi-elliptical nozzle flow is transitional at relatively higher mass flow rates within the facility operating envelope.

Arc-jets↗
NASA NTRSDate not supplied

On Characterization of Laminar to Turbulent Transitional Flow in the Truncated IHF Semi-Elliptical Nozzle

This paper reports computational analysis and experimental data to characterize the laminar to turbulent flow transition in a high-enthalpy panel test facility at NASA Ames Research Center. The recently developed facility configuration uses a truncated version of an existing semi-elliptical nozzle in the 60-MW Interaction Heating Facility, and it provides testing capability for panel test articles as large as 43.2 cm x 43.2 cm (17 in x 17 in). A water-cooled calibration plate, which is attached to the semi-elliptical nozzle bottom surface and instrumented with twenty Gardon-gage heat flux calorimeters and twelve pressure gages, is used to characterize the convective heating environment over the panel test articles. The present analysis comprises computational fluid dynamics simulations of the nonequilibrium flowfield in the facility nozzle and test box, and the flowfields over panel test articles, and comparisons with the measured test data. Both laminar and turbulent simulations are performed. Constant current studies are conducted: the measured data are grouped at the same arc current levels with varying mass flow rates, and they are compared with corresponding computations. For all currents considered, these studies indicate that the semi-elliptical nozzle flow is transitional at relatively higher mass flow rates within the facility operating envelope. An approximate facility map for the transitional flow characterization is developed, showing laminar and transitional to turbulent flow regions.

Arc-jets↗
NASA NTRS1994

The use of multispectral thermal infrared image data to estimate the sulfur dioxide flux from volcanoes: A case study from Mount Etna, Sicily, July 29, 1986

We have found that image data acquired with NASA's airborne Thermal Infrared Multispectral Scanner (TIMS) can be used to make estimates of the SO2 content of volcanic plumes. TIMS image data are most applicable to the study of partially transparent SO2 plumes, such as those released during quiescent periods or nonexplosive eruptions. The estimation procedure is based on the LOWTRAN 7 radiative transfer code, which we use to model the radiance perceived by TIMS as it views the ground through an SO2 plume. The input to the procedure includes the altitudes of the aircraft and ground, the altitude and thickness of the SO2 plume, the emissivity of the ground, and altitude profiles of the atmospheric pressure, temperature, and relative humidity. We use the TIMS data to estimate both ground temperatures beneath a plume and SO2 concentrations within a plume. Applying our procedure to TIMS data acquired over Mount Etna, Sicily, on July 29, 1986, we estimate that the SO2 flux from the volcano was approximately 6700 t d(exp -1). The use of TIMS to study SO2 plumes represents a bridge between highly localized methods, such as correlation spectroscopy or direct sampling, and small-scale mapping techniques involving satellite instruments such as the Total Ozone Mapping Spectrometer or Microwave Limb Sounder. We require further airborne experiments to refine our estimation procedure. This refinement is a necessary preparation for the schedueled 1998 launch of the Advanced Spaceborne Thermal Emission and Reflectance Radiometer, which will allow large-scale multispectral thermal infrared image data to be collected over virtually any volcano on Earth at least once every 16 days.

Realmuto, Vincent J.↗
NASA NTRS1996

Pressure Oscillations in Shuttle Solid Rocket Motors

All Shuttle Solid Rocket Motors (SRM's) exhibit low amplitude longitudinal pressure oscillations during motor burn. Although the oscillations have no known deleterious effect on motor ballistics, the acoustic pressure variations cause thrust oscillations that might affect Shuttle systems or components. The acoustic mode of greatest interest is the first or fundamental mode which, in the SRM, has a nominal frequency of 14-Hz. Oscillations in the SRM are believed to be caused by coupling between large scale vortices and the acoustic modes of the motor chamber. The vortices are thought to be created in the region of the motor segment interfaces and are inherent in the design of the motor. In such a situation the usual approach is to measure the oscillations and assess their impact on any sensitive components through tests and analysis. Questionable components can be altered to survive the vibration environment. As motor firings occur, oscillations are monitored to determine whether there are changes in the nature of the oscillations. Since the first static test, SRM's have been equipped with instrumentation especially designed to acquire chamber pressure oscillation data. Data from the first SRM static tests were used to establish predicted upper bounds for the maximum amplitudes in the latter half of burn. Those bounds have been used as a basis for worst-case simulation scenarios by specialists in structural dynamics at NASA and Rockwell International and to provide a basis for evaluating data from individual motors which were tested subsequent to the original SRM's. This paper updates the upper bounds prediction the High Performance Motors (HPM) by including data from all static tests performed to date including both original SRM's and post Challenger SRM's or Reusable Solid Rocket Motors (RSRM) in which the joint design was changed. All together, this study examines 27 SRM motors, 16 HPM motors and 11 RSRM motors. Predicted upper bounds will be made for both the first and second longitudinal modes. The first mode upper bounds will be compared to the original seven standard rocket motors (STD). The results indicate that, although the upper bounds have increased, they are still within acceptable bounds.

Blomshield, Fred S.↗