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NASA NTRS2018

Development of Spacecraft Radiated Susceptibility RS103 Requirements From Modeling Methods

In defining radiated susceptibility requirements for a spacecraft with multiple number of receivers and transmitters in close proximity to each other, the main objective of an RF coupling analysis is to determine if the mechanical configuration of the receiver and transmitter antennas presents a risk to the functionality and safety of sensitive science instruments on the payload as a result of unintended RF coupling. Where there is a potential risk for interference or permanent damage, further analysis is required to evaluate the feasibility of mitigation schemes, such as mechanical reconfiguration of antennas or additional RF filtering. From these coupling analysis results, radiated susceptibility RS103 requirements are derived to better reflect actual requirement levels with adequate test margins.

Gonzalez, Edward C.↗

NASA NTRS1997

Three-Dimensional Analysis of Nuclear Size, Shape and Displacement in Clover Root Cap Statocytes from Space and a Clinostat

Under normal (l-g) conditions the statocytes of root caps have a characteristic polarity with the nucleus in tight association with the proximal cell wall; but, in altered gravity environments including microgravity (mu-g) and the clinostat (c-g) movement of the nucleus away from the proximal cell wall is not uncommon. To further understand the cause of gravity-dependent nuclear displacement in statocytes, three-dimensional cell reconstruction techniques were used to precisely measure the volumes, shapes, and positions of nuclei in white clover (Trifolium repens) flown in space and rotated on a clinostat. Seeds were germinated and grown for 72 hours aboard the Space Shuttle (STS-63) in the Fluid Processing Apparatus (BioServe Space Technologies, Univ. of Colorado, Boulder). Clinorotation experiments were performed on a two-axis clinostat (BioServe). Computer reconstruction of selected groups of statocytes were made from serial sections (0.5 microns thick) using the ROSS (Reconstruction Of Serial Sections) software package (Biocomputation Center, NASA Ames Research Center). Nuclei were significantly displaced from the tops of cells in mu-g (4.2 +/- 1.0 microns) and c-g (4.9 +/- 1.4 microns) when compared to l-g controls (3.4 +/- 0.8 gm); but, nuclear volume (113 +/- 36 cu microns, 127 +/- 32 cu microns and 125 +/- 28 cu microns for l-g, mu-g and c-g respectively) and the ratio of nuclear volume to cell volume (4.310.7%, 4.211.0% and 4.911.4% respectively) were not significantly dependent on gravity treatment (ANOVA; alpha = 0.05). Three-dimensional analysis of nuclear shape and proximity to the cell wall, however, showed that nuclei from l-g controls appeared ellipsoidal while those from space and the clinostat were more spherically shaped. This change in nuclear shape may be responsible for its displacement under altered gravity conditions. Since the cytoskeleton is known to affect nuclear polarity in root cap statocytes, those same cytoskeletal elements could also control nuclear shape. This alteration in nuclear shape and position in mu-g and c-g when compared to l-g may lead to functional differences in the gravity signaling systems of plants subjected to altered gravity environments.

Smith, J.D.↗

NASA NTRS1971

Study aids accuracy of turbopump axial thrust analysis

Test program to verify theory used in calculating axial thrust uses turbopump instrumented with /a/ proximity transducers for measuring shaft position, /b/ a strain gage thrust bearing carrier to measure axial thrust, and /c/ internal pressure taps to define component pressure gradients used in thrust calculations.

Nielson, C. E.↗

NASA NTRS2011

Space Transportation System (STS)-133/External Tank (ET)-137 Intertank (IT) Stringer Cracking Issue and Repair Assessment: Proximate Cause Determination and Material Characterization Study

Several cracks were detected in stringers located beneath the foam on the External Tank (ET) following the launch scrub of Space Transportation System (STS)-133 on November 5, 2010. The stringer material was aluminum-lithium (AL-Li) 2090-T83 fabricated from sheets that were nominally 0.064 inches thick. The mechanical properties of the stringer material were known to vary between different material lots, with the stringers from ET-137 (predominately lots 620853 and 620854) having the highest yield and ultimate stresses. Subsequent testing determined that these same lots also had the lowest fracture toughness properties. The NASA Engineering and Safety Center (NESC) supported the Space Shuttle Program (SSP)-led investigation. The objective of this investigation was to develop a database of test results to provide validation for structural analysis models, independently confirm test results obtained from other investigators, and determine the proximate cause of the anomalous low fracture toughness observed in stringer lots 620853 and 620854. This document contains the outcome of the investigation.

Piascik, Robert S.↗

NASA NTRS1997

Sulfur in Cometary Dust

The computer-intensive project consisted of the analysis and synthesis of existing data on composition of comet Halley dust particles. The main objective was to obtain a complete inventory of sulfur containing compounds in the comet Halley dust by building upon the existing classification of organic and inorganic compounds and applying a variety of statistical techniques for cluster and cross-correlational analyses. A student hired for this project wrote and tested the software to perform cluster analysis. The following tasks were carried out: (1) selecting the data from existing database for the proposed project; (2) finding access to a standard library of statistical routines for cluster analysis; (3) reformatting the data as necessary for input into the library routines; (4) performing cluster analysis and constructing hierarchical cluster trees using three methods to define the proximity of clusters; (5) presenting the output results in different formats to facilitate the interpretation of the obtained cluster trees; (6) selecting groups of data points common for all three trees as stable clusters. We have also considered the chemistry of sulfur in inorganic compounds.

Fomenkova, M. N.↗

NASA NTRS2012

Analysis and Synthesis of Tonal Aircraft Noise Sources

Fixed and rotary wing aircraft operations can have a significant impact on communities in proximity to airports. Simulation of predicted aircraft flyover noise, paired with listening tests, is useful to noise reduction efforts since it allows direct annoyance evaluation of aircraft or operations currently in the design phase. This paper describes efforts to improve the realism of synthesized source noise by including short term fluctuations, specifically for inlet-radiated tones resulting from the fan stage of turbomachinery. It details analysis performed on an existing set of recorded turbofan data to isolate inlet-radiated tonal fan noise, then extract and model short term tonal fluctuations using the analytic signal. Methodologies for synthesizing time-variant tonal and broadband turbofan noise sources using measured fluctuations are also described. Finally, subjective listening test results are discussed which indicate that time-variant synthesized source noise is perceived to be very similar to recordings.

Allen, Matthew P.↗

NASA NTRS1986

Biological extinction in earth history

Virtually all plant and animal species that have ever lived on the earth are extinct. For this reason alone, extinction must play an important role in the evolution of life. The five largest mass extinctions of the past 600 million years are of greatest interest, but there is also a spectrum of smaller events, many of which indicate biological systems in profound stress. Extinction may be episodic at all scales, with relatively long periods of stability alternating with short-lived extinction events. Most extinction episodes are biologically selective, and further analysis of the victims and survivors offers the greatest chance of deducing the proximal causes of extinction. A drop in sea level and climatic change are most frequently invoked to explain mass extinctions, but new theories of collisions with extraterrestrial bodies are gaining favor. Extinction may be constructive in a Darwinian sense or it may only perturb the system by eliminating those organisms that happen to be susceptible to geologically rare stresses.

Raup, D. M.↗

NASA NTRS1991

Analysis of unsteady pressures induced on a body by a rotor

An analysis was conducted on the unsteady pressures measured on a body surface in proximity to a rotor. Unsteady pressures were measured at strategic points on the body in forward flight at various combination of advance ratio, rotor thrust, and tip-path-plane angle. It was found that the local values of unsteady pressure were significantly altered by small changes in rotor thrust and advance ratio; tip-path-plane angle variations had a much smaller effect. Four characteristic pressure signatures representative of (1) blade passage, (2) close wake interactions with the body, (3) wake impingement on the body, and (4) postwake impingement were distinguished. These classifications were supported by correlations with shadowgraphic flow visualization of the rotor wake/body interaction, as well as unsteady potential flow models. This general classification of the surface pressure signatures has permitted a greater physical understanding of the overall air loads and possible mechanisms responsible for the interactional effects between a helicopter rotor and its fuselage.

Bi, Nai-Pei↗

NASA NTRS1993

Prostaglandin E2 Increased Rat Cortical Bone Mass When Administered Immediately Following Ovariectomy

To investigate the effects of ovariectomy and the simultaneous administration of prostaglandin E2 (PGE2) on rat tibial shaft cortical bone histomorphometry, thirty-five 3 month-old female Sprague-Dawley rats were either ovariectomized (OVX), or sham ovariectomy (sham-OVX). The OVX rats were divided into three groups and treated with 0, 1 and 6 mg PGE2/kg/day for 90 days. The double fluorescent labeled undecalcified tibial shaft cross sections (proximal to the tibiofibular junction) of all the subjects were used for histomorphometry analysis. No differences in cross-sectional area and cortical bone area were found between sham-OVX and OVX controls, but OVX increased marrow area, intracortical porosity area and endocortical eroded perimeter. Periosteal and endocortical bone formation rates decreased with aging yet OVX prevented these changes. These OVX-induced increases in marrow area and endocortical eroded perimeter were prevented by 1 mg PGE2/kg/day treatment and added bone to periosteal and endocortical surfaces and to the marrow cavity. At the 6 mg/kg/day dose level, PGE2-treated OVX rats increased total tissue area, cortical bone area, marrow trabmular bone area, minimal cortical width and intracortical porosity area, and decreased marrow area compared to basal, sham-OVX and OVX controls. In addition, periosteal bone formation was elevated in the 6 mg PGE2/kg/day-treated OVX rats compared to OVX controls. Endocortical eroded perimeter increased from basal and sham-OVX control levels, but decreased from OVX control levels in the 6 mg PGE2/kg/day-treated OVX rats. Our study confirmed that ovariectomy does not cause osteopenia in tibial shaft cortical bone in rats, but it does stimulate endocortical bone resorption and enlarges marrow area. The new findings from the present study demonstrate that PGE2 prevents the OVX-induced increases in endocortical bone resorption and marrow area and adds additional bone to periosteal and endocortical surfaces and to marrow cavity to increase total bone mass in the tibial shaft of OVX rats when given immediately following ovafiectomy.

Ke, Hua Zhu↗

NASA NTRS2012

Beat-to-Beat Blood Pressure Monitor

This device provides non-invasive beat-to-beat blood pressure measurements and can be worn over the upper arm for prolonged durations. Phase and waveform analyses are performed on filtered proximal and distal photoplethysmographic (PPG) waveforms obtained from the brachial artery. The phase analysis is used primarily for the computation of the mean arterial pressure, while the waveform analysis is used primarily to obtain the pulse pressure. Real-time compliance estimate is used to refine both the mean arterial and pulse pressures to provide the beat-to-beat blood pressure measurement. This wearable physiological monitor can be used to continuously observe the beat-to-beat blood pressure (B3P). It can be used to monitor the effect of prolonged exposures to reduced gravitational environments and the effectiveness of various countermeasures. A number of researchers have used pulse wave velocity (PWV) of blood in the arteries to infer the beat-to-beat blood pressure. There has been documentation of relative success, but a device that is able to provide the required accuracy and repeatability has not yet been developed. It has been demonstrated that an accurate and repeatable blood pressure measurement can be obtained by measuring the phase change (e.g., phase velocity), amplitude change, and distortion of the PPG waveforms along the brachial artery. The approach is based on comparing the full PPG waveform between two points along the artery rather than measuring the time-of-flight. Minimizing the measurement separation and confining the measurement area to a single, well-defined artery allows the waveform to retain the general shape between the two measurement points. This allows signal processing of waveforms to determine the phase and amplitude changes. Photoplethysmography, which measures changes in arterial blood volume, is commonly used to obtain heart rate and blood oxygen saturation. The digitized PPG signals are used as inputs into the beat-to-beat blood pressure measurement algorithm.

Lee, Yong Jin↗

NASA NTRS2012

Beat-to-Beat Blood Pressure Monitor

Lee, Yong Jin↗

NASA NTRS2023

Python Based Plume Dynamics Estimation Tool (PyPDET) Rapid Plume Strike Analysis for RPOD Maneuvers in Deep Space Operations

I worked as a NASA Intern during the Summer 2023 term in the DS-00 division under the supervision of my mentor, Dr. Jonathan Pitt. Our goal was to build on our previous work from 2022 to develop a plume strike estimation tool using a prescribed physics methodology and model plume impingement effects while considering the dynamics of a rendezvous, operations, proximity, and docking (RPOD) maneuver. This tool supports previously configured CFD-DSMC calculations by allowing for rapid analysis of initial designs using a low-fidelity source flow model. Engineers can then use the high-fidelity CFD-DSMC tool to consolidate results as they work towards finalizing a design. This year’s project was focused on developing a software application that other engineers would be using in their analysis. Thus, the user’s experience was considered in the development of this application. Proper documentation, testability, and modularity of the codebase was our priority. For example, the project included auto documentation procedures to start building towards a User Manual, while also including dedicated demonstration cases for more explicit communication of functionality. Also, this project included a framework for testing the source code for future developments. Additionally, care was taken to develop the code using an Object-Oriented Programming approach. Thus, allowing for a modular extensibility of functionality in anticipation of future developments. The core work of this project was developing an algorithm that would transform the visiting vehicle and associated thruster data according to the kinematics described in the jet firing history. It would then calculate the estimated plume strikes on two of the target vehicles and write data accordingly into a VTK file. Summer work is to conclude by developing and presenting a PowerPoint slide deck at the intern exit briefing on August 11 th , 2023. Once the model for simple plume strike calculations is developed and tested there are several avenues to explore to continue development of this tool. These are also discussed in this report.

Plume Impingement↗

NASA NTRS1981

Experiment K305: Quantitative analysis of selected bone parameters. Supplement 2: Bone elongation rate and bone mass in metaphysis of long bones

The proximal humeral metaphysis of rats from time periods recovery plus zero days (R+0), recovery plus six days (R+6), and recovery plus twenty nine days (R+29) was analyzed. The volume of calcified cartilage and bone in flight and synchronous controls was reduced in groups R+0 and R+6, but was normal in group R+29. The number of functional bone cells (osteoblasts and osteoclasts) was decreased in proportion to the amount of bone in the early groups, and was normal in the last group. The fatty marrow volume was increased only in flight animals of groups R+0 and R+6, but was normal in the R+29 group. Accumulation of excess fatty marrow was seen only in flight animals. The decreased amount of bone and calcified cartilage is believed to be the result of a temporarily slowed or arrested production of calcified cartilage as a substrate for bone formation. This would have resulted from slowed bone elongation during flight and synchronous control conditions. Bone elongation returned to normal by twenty nine days after return.

Jee, W. S. S.↗

NASA NTRS2004

Autonomous NanoTechnology Swarm (ANTS) Prospecting Asteroid Mission (PAM), Asteroid Proximity Operations

The Autonomous NanoTechnology Swarm (ANTS) is a generic mission architecture based on spatially distributed spacecraft, autonomous and redundant components, and hierarchical organization. The ANTS Prospecting Asteroid Mission (PAM) is an ANTS application which will nominally use a swarm of 1000 spacecraft. There would be 10 types of "specialists" with common spacecraft buses. There would be 10 subswarms of approximately 100 spacecraft each or approximately 10 of each specialist in each swarm. The ANTS PAM primary objective is the exploration of the asteroid belt in search of resources and material with astrobiologically relevant origins and signatures. The ANTS PAM spacecraft will nominally be released from a station in an Earth-Moon L1 libration point orbit, and they will use Solar sails for propulsion. The sail structure would be highly flexible, capable of changing morphology to change cross-section for capture of sunlight or to form effective "tip vanes" for attitude control. ANTS PAM sails would be capable of full to partial deployment, to change effective sail area and center of pressure, and thus allow attitude control. Results of analysis of a transfer trajectory from Earth to a sample target asteroid will be presented. ANTS PAM will require continuous coverage of different asteroid locations as close as one to two asteroid "diameters" from the surface of the asteroid for periods of science data collection during asteroid proximity operations. Hovering spacecraft could meet the science data collection objectives. The results of hovering analysis will be presented. There are locations for which hovering is not possible, for example on the illuminated side of the asteroid. For cases where hovering is not possible, the results of utilizing asteroid formations to orbit the asteroid and achieve the desired asteroid viewing will be presented for sample asteroids. The ability of ANTS PAM to reduce the area of the solar sail during asteroid proximity operations is critical to the maintenance of orbiting formations for a period of time. Results of analysis of potential "traffic" problems during asteroid proximity operations will be presented.

Marr, Greg↗

NASA NTRS1975

An RF link analysis of MSBLS during ALT

An analysis of the microwave scanning beam landing system (MSBLS) ground station to orbiter radio frequency (RF) link was made to determine if the expected signal levels will be compatible with orbiter receiver capabilities. Of primary interest was whether or not loss of data will occur due to interference caused by the orbiter 101 nose boom which provides additional air data during the approach and landing test. The results of the analysis indicate that a small amount of data loss may occur due to the proximity of the MSBLS antennas and the nose boom. Tabulated data of antenna radiation patterns are given.

Speir, R. E.↗

NASA NTRS1997

Comparative diversification dynamics among palaeocontinents during the Ordovician Radiation

The Ordovician Radiation was among the most extensive intervals of diversification in the history of life. However, a delineation of the proximal cause(s) of the Radiation remains elusive. Any such determination should involve an analysis of geographic overprints on diversification: did the Radiation occur randomly around the world or, alternatively, was it focused in particular geographic or depositional regimes? Here, I present a comparative evaluation of Ordovician diversification among several palaeocontinents to determine whether biotas associated with certain palaeocontinents exhibited different diversification patterns than others; in part, this involves a numerical "correction" to raw diversity trajectories. Clear disparities among palaeocontinents are indicated by the data, which appear to reflect differences in the extent of siliciclastic input partly in association with tectonic activity. Further testing will be required to fully substantiate the implication that siliciclastic influx was a predominant factor in the Ordovician Radiation, affecting a variety of higher taxa among all three Phanerozoic evolutionary faunas.

Non-NASA Center↗

NASA NTRS1986

Experimental study of effects of forebody geometry on high angle of attack static and dynamic stability and control

A series of low-speed wind tunnel tests on a generic airplane model with a cylindrical fuselage were made to investigate the effects of forebody shape and fitness ratio, and fuselage/wing proximity on static and dynamic lateral/directional stability. In addition, some preliminary testing to determine the effectiveness of deflectable forebody strakes for high angle of attack yaw control was conducted. During the stability investigation, 11 forebodies were tested including three different cross-sectional shapes with fineness ratios of 2, 3, and 4. In addition, the wing was tested at two longitudinal positions to provide a substantial variation in forebody/wing proximity. Conventional force tests were conducted to determine static stability characteristics, and single-degree-of-freedom free-to-roll tests were conducted to study the wing rock characteristics of the model with the various forebodies. Flow visualization data were obtained to aid in the analysis of the complex flow phenomena involved. The results show that the forebody cross-sectional shape and fineness ratio and forebody/wing proximity can strongly affect both static and dynamic (roll) stability at high angles of attack. These characteristics result from the impact of these factors on forebody vortex development, the behavior of the vortices in sideslip, and their interaction with the wing flow field. Preliminary results from the deflectable strake investigation indicated that forebody flow control using this concept can provide very large yaw control moments at stall and post-stall angles of attack.

Brandon, J. M.↗

NASA NTRS2004

Disk Crack Detection for Seeded Fault Engine Test

Work was performed to develop and demonstrate vibration diagnostic techniques for the on-line detection of engine rotor disk cracks and other anomalies through a real engine test. An existing single-degree-of-freedom non-resonance-based vibration algorithm was extended to a multi-degree-of-freedom model. In addition, a resonance-based algorithm was also proposed for the case of one or more resonances. The algorithms were integrated into a diagnostic system using state-of-the- art commercial analysis equipment. The system required only non-rotating vibration signals, such as accelerometers and proximity probes, and the rotor shaft 1/rev signal to conduct the health monitoring. Before the engine test, the integrated system was tested in the laboratory by using a small rotor with controlled mass unbalances. The laboratory tests verified the system integration and both the non-resonance and the resonance-based algorithm implementations. In the engine test, the system concluded that after two weeks of cycling, the seeded fan disk flaw did not propagate to a large enough size to be detected by changes in the synchronous vibration. The unbalance induced by mass shifting during the start up and coast down was still the dominant response in the synchronous vibration.

Luo, Huageng↗