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NASA NTRS2002

Hawaii Ocean Mixing Experiment: Program Summary

It is becoming apparent that insufficient mixing occurs in the pelagic ocean to maintain the large scale thermohaline circulation. Observed mixing rates fall a factor of ten short of classical indices such as Munk's "Abyssal Recipe." The growing suspicion is that most of the mixing in the sea occurs near topography. Exciting recent observations by Polzin et al., among others, fuel this speculation. If topographic mixing is indeed important, it must be acknowledged that its geographic distribution, both laterally and vertically, is presently unknown. The vertical distribution of mixing plays a critical role in the Stommel Arons model of the ocean interior circulation. In recent numerical studies, Samelson demonstrates the extreme sensitivity of flow in the abyssal ocean to the spatial distribution of mixing. We propose to study the topographic mixing problem through an integrated program of modeling and observation. We focus on tidally forced mixing as the global energetics of this process have received (and are receiving) considerable study. Also, the well defined frequency of the forcing and the unique geometry of tidal scattering serve to focus the experiment design. The Hawaiian Ridge is selected as a study site. Strong interaction between the barotropic tide and the Ridge is known to take place. The goals of the Hawaiian Ocean Mixing Experiment (HOME) are to quantify the rate of tidal energy loss to mixing at the Ridge and to identify the mechanisms by which energy is lost and mixing generated. We are challenged to develop a sufficiently comprehensive picture that results can be generalized from Hawaii to the global ocean. To achieve these goals, investigators from five institutions have designed HOME, a program of historic data analysis, modeling and field observation. The Analysis and Modeling efforts support the design of the field experiments. As the program progresses, a global model of the barotropic (depth independent) tide, and two models of the baroclinic (depth varying) tide, all validated with near-Ridge data, will be applied, to reveal the mechanisms of tidal energy conversion along the Ridge, and allow spatial and temporal integration of the rate of conversion. Field experiments include a survey to identify "hot spots" of enhanced mixing and barotropic to baroclinic conversion, a Nearfield study identifying the dominant mechanisms responsible for topographic mixing, and a Farfield program which quantifies the barotropic energy flux convergence at the Ridge and the flux divergence associated with low mode baroclinic waves radiation. The difference is a measure of the tidal power available for mixing at the Ridge. Field work is planned from years 2000 through 2002, with analysis and modeling efforts extending through early 2006. If successful, HOME will yield an understanding of the dominant topographic mixing processes applicable throughout the global ocean. It will advance understanding of two central problems in ocean science, the maintenance of the abyssal stratification, and the dissipation of the tides. HOME data will be used to improve the parameterization of dissipation in models which presently assimilate TOPEX-POSEIDON observations. The improved understanding of the dynamics and spatial distribution of mixing processes will benefit future long-term programs such as CLIVAR.

Ray, Richard D.↗

NASA NTRS2002

Aerocapture Technology Development Needs for Outer Planet Exploration

The purpose of this white paper is to identify aerocapture technology and system level development needs to enable NASA future mission planning to support Outer Planet Exploration. Aerocapture is a flight maneuver that takes place at very high speeds within a planet's atmosphere that provides a change in velocity using aerodynamic forces (in contrast to propulsive thrust) for orbit insertion. Aerocapture is very much a system level technology where individual disciplines such as system analysis and integrated vehicle design, aerodynamics, aerothermal environments, thermal protection systems (TPS), guidance, navigation and control (GN&C) instrumentation need to be integrated and optimized to meet mission specific requirements. This paper identifies on-going activities, their relevance and potential benefit to outer planet aerocapture that include New Millennium ST7 Aerocapture concept definition study, Mars Exploration Program aeroassist project level support, and FY01 Aeroassist In-Space Guideline tasks. The challenges of performing aerocapture for outer planet missions such as Titan Explorer or Neptune Orbiter require investments to advance the technology readiness of the aerocapture technology disciplines for the unique application of outer planet aerocapture. This white paper will identify critical technology gaps (with emphasis on aeroshell concepts) and strategies for advancement.

Wercinski, Paul↗

NASA NTRS2002

Human Factors Process Task Analysis: Liquid Oxygen Pump Acceptance Test Procedure at the Advanced Technology Development Center

This viewgraph presentation provides information on Human Factors Process Failure Modes and Effects Analysis (HF PFMEA). HF PFMEA includes the following 10 steps: Describe mission; Define System; Identify human-machine; List human actions; Identify potential errors; Identify factors that effect error; Determine likelihood of error; Determine potential effects of errors; Evaluate risk; Generate solutions (manage error). The presentation also describes how this analysis was applied to a liquid oxygen pump acceptance test.

Diorio, Kimberly A.↗

NASA NTRS2002

Repair and Utilization of the Kratos XSAM 800 X-Ray Photoelectron Spectrometer (XPS)

The objectives for this summer faculty fellowship were first to repair the Kratos XSAM 800 X-ray Photoelectron Spectrometer (XPS) and then to utilize the instrument to participate in ongoing research projects at KSC and in the researcher's own laboratory at UCF. The first 6 weeks were used in repairing the instrument. Working both alone and with the Kratos service engineer, a number of hardware problems, largely associated with the sample stage control system, were corrected. Defective parts were identified and fixed in the computer driver boards, the stage power supply, and the driver interface. The power supply was completely replaced. After four weeks of work, the instrument was functional. This occurred on a Wednesday. The following Friday the instrument had to be completely shut down because the power to the O & C Building was to be turned off. The instrument was properly secured. On Monday, the instrument was powered up and the original problems returned. After another 2 weeks of work, a software problem was identified. This problem caused the computer to use a defective port for the sample stage control. It was circumvented by rewriting the startup routine. The final 3 weeks of the fellowship were spent using the XPS to analyze samples being studied in the Langley materials project (Martha Williams) and a catalyst project (Dr. Orlando Melendez). During this time, several sample analysis requests from other groups at KSC also came in and those samples were run as well. The summer faculty fellowship also allowed many contacts to be made. After meeting with the sensors group, two projects were identified for collaboration and white papers are being prepared. One project aims to develop small, very sensitive hydrogen detectors and the other to develop a broad area, easily monitored, zero power consumption hydrogen detector. In addition to the work mentioned above, the XPS was utilized in a study underway in Dr. Hampton's laboratory at UCF.

Hampton, Michael D.↗

NASA NTRS2003

Statistical Distribution of Inflation on Lava Flows: Analysis of Flow Surfaces on Earth and Mars

The surface morphology of a lava flow results from processes that take place during the emplacement of the flow. Certain types of features, such as tumuli, lava rises and lava rise pits, are indicators of flow inflation or endogenous growth of a lava flow. Tumuli in particular have been identified as possible indicators of tube location, indicating that their distribution on the surface of a lava flow is a junction of the internal pathways of lava present during flow emplacement. However, the distribution of tumuli on lava flows has not been examined in a statistically thorough manner. In order to more rigorously examine the distribution of tumuli on a lava flow, we examined a discrete flow lobe with numerous lava rises and tumuli on the 1969 - 1974 Mauna Ulu flow at Kilauea, Hawaii. The lobe is located in the distal portion of the flow below Holei Pali, which is characterized by hummocky pahoehoe flows emplaced from tubes. We chose this flow due to its discrete nature allowing complete mapping of surface morphologies, well-defined boundaries, well-constrained emplacement parameters, and known flow thicknesses. In addition, tube locations for this Mauna Ulu flow were mapped by Holcomb (1976) during flow emplacement. We also examine the distribution of tumuli on the distal portion of the hummocky Thrainsskjoldur flow field provided by Rossi and Gudmundsson (1996). Analysis of the Mauna Ulu and Thrainsskjoldur flow lobes and the availability of high-resolution MOC images motivated us to look for possible tumuli-dominated flow lobes on the surface of Mars. We identified a MOC image of a lava flow south of Elysium Mons with features morphologically similar to tumuli. The flow is characterized by raised elliptical to circular mounds, some with axial cracks, that are similar in size to the tumuli measured on Earth. One potential avenue of determining whether they are tumuli is to look at the spatial distribution to see if any patterns similar to those of tumuli-dominated terrestrial flows can be identified. Since tumuli form by the injection of lava beneath a crust, the distribution of tumuli on a flow should represent the distribution of thermally preferred pathways beneath the surface of the crust. That distribution of thermally preferred pathways may be a function of the evolution of a basaltic lava flow. As a longer-lived flow evolves, initially broad thermally preferred pathways would evolve to narrower, more well-defined tube-like pathways. The final flow morphology clearly preserves the growth of the flow over time, with inflation features indicating pathways that were not necessarily contemporaneously active. Here, we test using statistical analysis whether this final flow morphology produces distinct distributions that can be used to readily determine the distribution of thermally preferred pathways beneath the surface of the crust.

Glazel, L. S.↗

NASA NTRS2002

Unified Instrumentation: Examining the Simultaneous Application of Advanced Measurement Techniques for Increased Wind Tunnel Testing Capability

A Unified Instrumentation Test examining the combined application of Pressure Sensitive Paint, Projection Moire Interferometry, Digital Particle Image Velocimetry, Doppler Global Velocimetry, and Acoustic Microphone Array has been conducted at the NASA Langley Research Center. The fundamental purposes of conducting the test were to: (a) identify and solve compatibility issues among the techniques that would inhibit their simultaneous application in a wind tunnel, and (b) demonstrate that simultaneous use of advanced instrumentation techniques is feasible for increasing tunnel efficiency and identifying control surface actuation / aerodynamic reaction phenomena. This paper provides summary descriptions of each measurement technique used during the Unified Instrumentation Test, their implementation for testing in a unified fashion, and example results identifying areas of instrument compatibility and incompatibility. Conclusions are drawn regarding the conditions under which the measurement techniques can be operated simultaneously on a non-interference basis. Finally, areas requiring improvement for successfully applying unified instrumentation in future wind tunnel tests are addressed.

Fleming, Gary A.↗

NASA NTRS2003

An Evaluation of Electronic Nose for Space Program Applications

The ability to monitor air contaminants in the Shuttle and the International Space Station is important to ensure the health and safety of astronauts. Three specific space applications have been identified that would benefit from a chemical monitor: organic contaminants in crew cabins, propellant contaminants in the airlock, and pre-combustion fire detection. NASA has assessed several commercial and developing electronic noses (e-noses) for these applications. A preliminary series of tests identified those e-noses that exhibited sufficient sensitivity to the vapors of interest. These e-noses were further tested to assess their ability to identify vapors, and in-house software has been developed to enhance identification. This paper describes the tests, the classification ability of selected e-noses, and the software improvements made to meet the requirements for these space program applications.

Young, Rebecca C.↗

NASA NTRS2002

TIES for Dummies 3rd Edition (Technology Identification, Evaluation, and Selection) Basic how to's to implement the TIES method

The TIES method is a forecasting environment whereby the decision-maker has the ability to easily assess and trade-off the impact of various technologies without sophisticated and time-consuming mathematical formulations. TIES provides a methodical approach where technically feasible alternatives can be identified with accuracy and speed to reduce design cycle time, and subsequently, life cycle costs, and was achieved through the use of various probabilistic methods, such as Response Surface Methodology and Monte Carlo Simulations. Furthermore, structured and systematic techniques are utilized from other fields to identify possible concepts and evaluation criteria by which comparisons can be made. This objective is achieved by employing the use of Morphological Matrices and Multi-Attribute Decision Making techniques. Through the execution of each step, a family of design alternatives for a given set of customer requirements can be identified and assessed subjectively or objectively. This methodology allows for more information (knowledge) to be brought into the earlier phases of the design process and will have direct implications on the affordability of the system. The increased knowledge allows for optimum allocation of company resources and quantitative justification for program decisions. Finally, the TIES method provided novel results and quantitative justification to facilitate decision making in the early stages of design so as to produce affordable and quality products.

Kirby, Michelle R.↗

NASA NTRS2003

Star Identification Using a Triplet Algorithm

The stars observed by onboard star trackers must be identified in order for the star tracker information to be used for attitude determination. Star identification associates the observed stars in the body frame with catalog stars, the positions of which in an inertial frame are well known. If the attitude is approximately known (from less accurate sensors) identification is relatively simple, but if there is no prior attitude knowledge (the Lost in Space problem) star identification is quite difficult. A new, reliable, and accurate star identification algorithm has been developed for use in a batch, ground-based attitude determination system. The identification algorithm uses input from one or more star trackers, each of which can observe three or more stars simultaneously. If observations are available at different times, rate data is used to relate them. The algorithm includes the following steps that are automatically performed: 1) Observations are examined to determine the optimal set of simultaneous star observations in a single tracker. 2) The selected optimal observations are identified using a triplet match. 3) The identified stars in the selected tracker at the selected time are used to compute an attitude at that time. 4) The rate data is refined by determination of biases that minimize the dispersion of repeated observations of the same stars. 5) The refined rate data is used to propagate the attitude to the times of each star observation. 6) The attitude at each time is used to associate all stars observed at that time, in each tracker, with catalog stars. The overall algorithm is very dependable at producing accurate star identification with no initial attitude input.

Hashmall, Joseph A.↗

NASA NTRS2003

Biotechnology System Facility: Risk Mitigation on Mir

NASA is working with its international partners to develop space vehicles and facilities that will give researchers the opportunity to conduct scientific investigations in space. As part of this activity, NASA's Biotechnology Cell Science Program (BCSP) at the Johnson Space Center (JSC) is developing a world-class biotechnology laboratory facility for the International Space Station (ISS). This report describes the BCSP, including the role of the BTS. We identify the purpose and objectives of the BTS and a detailed description of BTS facility design and operational concept, BTS facility and experiment-specific hardware, and scientific investigations conducted in the facility. We identify the objectives, methods, and results of risk mitigation investigations of the effects of microgravity and cosmic radiation on the BTS data acquisition and control system. These results may apply to many other space experiments that use commercial, terrestrial-based data acquisition technology. Another focal point is a description of the end-to-end process of integrating and operating biotechnology experiments on a variety of space vehicles. The identification of lessons learned that can be applied to future biotechnology experiments is an overall theme of the report. We include a brief summary of the science results, but this is not the focus of the report. The report provides some discussion on the successful 130-day tissue engineering experiment performed in BTS on Mir and describes a seminal gene array investigation that identified a set of unique genes that are activated in space.

Gonda, Steve R., III↗

NASA NTRS1990

Transfer Vehicle Accommodations at Transportation Node

There are three primary objectives of this study. The first is to identify time-phased accommodation capabilities necessary to support the civil space exploration initiatives. These initiatives include the Lunar and Mars missions in the Human Exploration Initiative (HEI). Primary accommodation requirements include integration and assembly of vehicle components and systems on-orbit, and protection of these vehicles from the space environment, particularly debris. Secondly, this study will develop accommodation concepts, define impacts (hooks and scars) to Space Station Freedom (SSF), identify staging/servicing requirements, and identify required technology advances. Finally, the majority of the study effort has been devoted to conducting a trade study to evaluate alternative transfer vehicle accommodation concepts. These concepts have ranged from basing all transfer vehicle accommodations for both Lunar and Mars transfer vehicles at SSF, to basing all accommodation capabilities off SSF. Two steps are shown in the NASA reference SSF evolution process. The first configuration is to provide lunar transfer vehicle accommodation support, and the second is to provide accommodation support for the Mars transfer vehicle. (MTV)

Hueter, Uwe↗

NASA NTRS2001

KT Boundary Impact Debris from DSDP Site 577

The KT boundary at DSDP Site 577 (Shatsky Rise, western North Pacific) is in a calcareous nannofossil ooze. It is bioturbated so Ir and impact debris are smeared across less than 15 cm of core. An absence of sulfides and chalcophile enrichment and the presence of Mn-micronodules indicate that this boundary did not experience anoxic conditions typical of many other calcareous KT sites. Because of its shallow burial (109 m) ejecta is extremely well preserved and has been the subject of numerous studies. Three high-temperature minerals have been identified at this site. Clinopyroxene (cpx), found only at Site 577 may be precursor to diagenetic sanidine in some European sites. Magnesioferrite spinel has the highest Fe2O3/FeO of any locality and can have and trace inclusions of Ni-magnesiowustite, which is known at only one other site (Site 596). Other debris described includes shocked quartz grains less than 200 microns, hollow spherules possibly related to impact melt glasses found near Chicxulub, and irregular Ir-rich particles that may be derived directly from meteoritic materials. The latter may be related to the fossil meteorite found at Site 576, just 500 km to the east. A large-volume (approx. 10 cc) sample was taken to systematically characterize debris. The less than 60 microns fraction of the carbonate-free sediment contained 44 mg of impact debris. 2700 particles less than l00 microns were classified based on color, shape, and morphology. About 55% are generally light colored, composed mostly of clays, and typically lack magnesioferrite spinel. Less than half of these are quite spherical; many have irregular shapes, possibly from fragmentation. Hollow spherules with smooth shiny surfaces are only 2% of the total but many fragments in the 60 - 100 microns fraction suggest that they were more abundant and that some may have been quite large; 800 microns or more. Cpx-bearing spherules, easily identified by green crystals at the surface, constitute only 2.5% of the total. Three cpx spherules are dumbbells. The other 40% of the debris is a complex assemblage of dark-colored particles, most of which have magnesioferrite spinel. We have currently separated these into 6 groups based on color and morphology, but this hardly describes the diversity of this group. They range from smooth and spherical to rough and irregular in shape. Some have a planar cleavage, similar to some broken cosmic spherules. 220 particles were irradiated for trace element analysis, as groups and as individual particles. It appears that every spherule type as at least a few ng/g Ir. Several of the spinel-bearing particles have been identified with high Ir (200-1500 ng/g), Cr (2-5 mg/g), and Ni (2-10 mg/g), consistent with results. It is hoped that some of these will yield potential fragments of the KT bolide. Only five have been sectioned to date and they are characterized by high concentrations of spinel; two contained traces of magnesiowustite. This debris constitutes a complex assemblage of ejecta materials. The light-colored, spinel-free particles likely derive mainly from target materials. A significant fraction of these are probably alteration products of cpx-spherules. The dark-colored debris is more likely to have high siderophile concentrations, and thus a high extraterrestrial component. However, the majority don't. Most of the larger spinel-bearing spherules have modest Ir concentrations (5-30 ng/g).

Kyte, Frank T.↗

NASA NTRS2003

From Global Reconnaissance to Sample Return: A Proposal for a Post-2009 Strategy to Follow the Water on Mars

Since the mid-1990's, the stated strategy of the Mars Exploration Program has been to Follow the Water. Although this strategy has been widely publicized, its degree of influence -- and the logic behind its current implementation (as reflected in mission planning, platform and instrument selection, and allocation of spacecraft resources) remains unclear. In response to this concern, we propose an integrated strategy for the post-2009 exploration of Mars that identifies the scientific objectives, rationale, sequence of missions, and specific investigations, that we believe provides the maximum possible science return by pursuing the most direct, cost-effective, and technically capable approach to following the water. This strategy is based on the orbital identification, high-resolution surface investigation, and ultimate sampling of the highest priority targets: near-surface liquid water and massive ground ice (potentially associated with the discharge of the outlflow channels or the relic of a former ocean). The analysis of such samples, in conjunction with the data acquired by the necessary precursor investigations (to identify the locations and characterize the environments of the optimum sampling sites), is expected to address a majority of the goals and high priority science objectives identified by MEPAG.

S M Clifford↗

NASA NTRS2003

Detecting Near-Surface Water and Hydrate Minerals on Mars from a Rover, Penetrator, or Borehole: The HYDRA Instrument

One of the major goals of near term NASA Mars exploration is to identify exact locations of near-surface water or hydrated minerals on Mars. Evidence for the existence of recent nearsurface water on Mars underscores the need for developing instrumentation that can identify water or hydrated minerals very near the surface. Further encouraging evidence of surface and near-surface water and hydrate minerals on Mars comes from neutron spectrometer measurements aboard Mars Odyssey. Preliminary results show very large regions of high hydrogen content poleward of 60 deg. latitude, as well as interesting features closer to the equator. However, spatial resolution from orbit is very poor, approx. 400 km. The next logical step is to use in-situ or near-surface investigations to map in detail some of the most interesting features. Relatively simple instrumentation based on He-3 gas proportional counters were shown to be highly successful on the Lunar Prospector mission in identifying even low levels of enhanced hydrogen abundances. Here we discuss HYDRA, a water- and hydrate-sensing instrument currently being developed under the NASA Mars Instrument Development Program (MIDP). HYDRA is based on Lunar Prospector technology, and is intended as a rover body-mounted instrument, or an instrument on an aerobot, penetrator, hard lander on the surface of Mars, or for borehole stratigraphy applications. Our proposed instrument would be ideal for such platforms as it would be small (less than 7 cm diameter by 10 cm long), low mass (less than 500 g), low power (less than 1W), and have a low data volume per measurement. We use neutron spectrometry (a) because of its proven ability to uniquely detect and quantify hydrogen abundance, and (b) because the resources required by this approach (weight, power, size, telemetry bandwidth, and measurement time) are extremely low. This compact neutron spectrometer package, comprised of two small He-3 gas proportional counters, offers superior sensitivity, extensive flight heritage, and inherent ruggedness. These tubes have survived approx. 1500 g's of acceleration in penetrator tests. In a landed application, HYDRA would help address many topics of interest to the Mars Exploration and Astrobiology communities: (a) nature and origin of stratified deposits; (b) water cycle(s) and temporal changes; (c) early water oceans, aquifers, precipitation; (d) current extent/location/state of water; (e) polar cap processes and temporal changes; (f) where extremeophiles could survive on Mars; (g) paleoclimate surface signatures and modeling; (h) strategies for future Mars exploration.

R C Elphic↗

NASA NTRS2003

Investigation of Critical Heat Flux in Reduced Gravity Using Photomicrographic Techniques

Experiments were performed to examine the effects of body force on flow boiling critical heat flux (CHF). FC-72 was boiled along one wall of a transparent rectangular flow channel that permitted photographic study of the vapor-liquid interface just prior to CHF. High-speed video imaging techniques were used to identify dominant CHF mechanisms corresponding to different flow orientations and liquid velocities. Six different CHF regimes were identified: Wavy Vapor Layer, Pool Boiling, Stratification, Vapor Counterflow, Vapor Stagnation, and Separated Concurrent Vapor Flow. CHF showed significant sensitivity to orientation for flow velocities below 0.2 m/s, where extremely low CHF values where measured, especially with downward-facing heated wall and downflow orientations. High flow velocities dampened the effects of orientation considerably. The CHF data were used to assess the suitability of previous CHF models and correlations. It is shown the Interfacial Lift-off Model is very effective at predicting CHF for high velocities at all orientations. The flooding limit, on the other hand, is useful at estimating CHF at low velocities and for downflow orientations. A new method consisting of three dimensionless criteria is developed for determining the minimum flow velocity required to overcome body force effects on near-saturated flow boiling CHF. Vertical upflow boiling experiments were performed in pursuit of identifying the trigger mechanism for subcooled flow boiling CHF. While virtually all prior studies on flow boiling CHF concern the prediction or measurement of conditions that lead to CHF, this study was focused on events that take place during the CHF transient. High-speed video imaging and photomicrographic techniques were used to record the transient behavior of interfacial features from the last steady-state power level before CHF until the moment of power cut-off following CHF. The video records show the development of a wavy vapor layer which propagates along the heated wall, permitting cooling prior to CHF only in wetting fronts corresponding to the wave troughs. Image analysis software was developed to estimate void fraction from the individual video images. The void fraction records for subcooled flow boiling show the CHF transient is accompanied by gradual lift-off of wetting fronts culminating in some maximum vapor layer mean thickness, following which the vapor layer begins to thin down as the transition to film boiling ensues. This study proves the Interfacial Lift-off Model, which has been validated for near-saturated flow boiling CHF, is equally valid for subcooled conditions.

Mudawar, Issam↗

NASA NTRS2003

A Closer Look at Quality Control

Spectrometers, which are durable, lightweight, and compact instruments, are a requirement for NASA deep space science missions, especially as NASA strives to conduct these missions with smaller spacecraft. NASA s Jet Propulsion Laboratory (JPL) awarded the Brimrose Corporation of America a Small Business Innovation Research (SBIR) contract to develop a compact, rugged, near-infrared spectrometer for possible future missions. Spectrometers are of particular importance on NASA missions because they help scientists to identify the make-up of a planet s surface and analyze the molecules in the atmosphere. Minerals and molecules emit light of various colors. The light, identified as spectra, is difficult to see, and spectrometers, which are essentially special cameras that collect the separate colors of light in an object, allow scientists to identify the different materials. For example, spectrometers can help scientists determine whether soil was created from lava flows or from meteorites.

Source record↗

NASA NTRS2003

A Solar System Survey of Forced Librations in Longitude

Physical librations in longitude are forced periodic variations of a body's rotation rate. If the torque producing the librations can be calculated, then observations of the phase and amplitude of librations can provide information on mass distribution, and effective strength of the body. In the near future prospects for observing physical librations look quite promising. Radio interferometric observations of Venus and Mercury may yield sufficiently accurate rotational observations that librations there may be visible. Range measurements from Earth to networks of landed instrument packages on Mars are likely to yield librational data there as well. We compute expected libration amplitudes from physical and orbital parameters of a set of planets and satellites partially motivated by a desire to identify candidates for future observations. Solar system bodies occupy one of three general rotation states: non-resonant states, resonant states, and the synchronous resonant state. Analytical treatments of forced librations were initially motivated by the Moon. Lunar librations were predicted by Newton, first detected telescopically by Bessel, and definitively resolved through lunar laser ranging which has led to quite thorough analysis of of librations for the synchronous case. The synchronous resonant state is commonly observed among satellites. The only known body to exist in a non-synchronous resonance is Mercury which exists in a 3:2 resonance, completing three rotations for every two revolutions about the sun. The analysis of Goldreich and Peale has lead to improved understanding of the general case of half integer resonance states. The dynamics of forced librations in non-resonant rotators has received less attention. While there are few cases in which non-resonant forced librations have been observed, Earth is an important exception, and current observing techniques may have the capacity to detect them on Venus. A comprehensive observing program spanning a range of solar system bodies can address an array of geophysical issues involving interior mass distribution of planets, satellites, and asteroids. Calculations of expected librations can supply amplitude estimates helpful in identifying the likelihood of detecting librations observationally. We present a survey of expected libration amplitudes for a subset of solar system bodies, identifying those bodies with amplitudes likely to be detectable, and commenting on spin state, and radial structure implications.

Comstock, R. L.↗

NASA NTRS2003

Small Engine Technology Investigation

The primary objective of the small engine technology study task is to identify key, enabling jet engine component technologies for improved performance, primarily for commercial, regional subsonic aircraft. The study involved two regional engine applications: the CF34 turbofan engine, which is installed on a regional jet application and the CT7-9 turboprop, which is installed on regional turboprop applications. Technologies to improve the performance of these applications were identified. Estimates of the benefits and development costs for each technology were made. Performance sensitivities were calculated for each of the technology items identified. The technology improvements were then translated into component improvements and their impact on the aircraft economics was evaluated. A factor of merit based on sfc was calculated as the percent improvement in sfc times the probability of improvement divided by the development evaluation costs associated with that technology item. The technologies were ranked for both the turbofan and turboprop applications.

Gregory, Brent B.↗