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All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

The Stratospheric Aerosol and Gas Experiment (SAGE) IV

Atmospheric composition continues to be a key Earth science focus for international space agencies and research organizations. The target constituent varies depending upon the topic area of interest such as monitoring the ozone layer and the efficacy of the Montreal Protocol, assessing the influence of volcanic eruptions and large wildfires on the atmosphere, improving our knowledge of transport processes, or evaluating the impacts of greenhouse gases on climate. Additionally, there is a growing need for measurement continuity of many trace gases both from an inability to properly assess long-term trends without it as well as the reliance of reanalyses and chemistry climate models on observational input. To this end, proper continuity requires continuous and overlapping multi-instrument data records of which spaceborne measurements are a critical component. However, most current satellite systems are well beyond their expected lifetimes, and so we look toward the future to develop the Stratospheric Aerosol and Gas Experiment (SAGE) IV as a future mission concept. Enabled by the NASA Earth Science Technology Office’s (ESTO) Instrument Incubator Program, the SAGE IV Pathfinder project developed and validated a prototype demonstration that paves the way for a future SAGE IV spaceflight mission. Utilizing solar occultation imaging, SAGE IV will be capable of measuring key species in the stratosphere and upper troposphere with the same quality as previous SAGE instruments but with greatly improved pointing knowledge and extensibility to new science targets. The precision and stability of a well-designed occultation instrument can act as a calibration reference standard for other spaceborne instruments, ensuring proper continuity of the desired science targets. Furthermore, current technological advancements allow SAGE IV to fit within a CubeSat framework and make use of commercial hardware, significantly reducing the size and cost when compared with traditional missions and enabling sustainability of future measurements.

Robert Damadeo↗
NASA NTRS1980

Status of the DOE/NASA critical gas turbine research and technology project

Activities performed in order to provide an R&T data base for utility gas turbine systems burning coal-derived fuels are described. Experiments were run to determine the corrosivity effects of trace metal contaminants (and potential fuel additives) on gas turbine materials and these results were correlated in a corrosion-life prediction model. Actual fuels were burned in a burner rig hot corrosion test to verify the model. A deposition prediction model was assembled and compared with results of actual coal-derived fuel deposition tests. Thermal barrier coatings were tested to determine their potential for protecting gas turbine hardware from the corrosive contaminants. Several coatings were identified with significantly improved spallation-resistance (and, hence, corrosion resistance).

Clark, J. S.↗
NASA NTRS1979

High temperature UF6 RF plasma experiments applicable to uranium plasma core reactors

An investigation was conducted using a 1.2 MW RF induction heater facility to aid in developing the technology necessary for designing a self critical fissioning uranium plasma core reactor. Pure, high temperature uranium hexafluoride (UF6) was injected into an argon fluid mechanically confined, steady state, RF heated plasma while employing different exhaust systems and diagnostic techniques to simulate and investigate some potential characteristics of uranium plasma core nuclear reactors. The development of techniques and equipment for fluid mechanical confinement of RF heated uranium plasmas with a high density of uranium vapor within the plasma, while simultaneously minimizing deposition of uranium and uranium compounds on the test chamber peripheral wall, endwall surfaces, and primary exhaust ducts, is discussed. The material tests and handling techniques suitable for use with high temperature, high pressure, gaseous UF6 are described and the development of complementary diagnostic instrumentation and measurement techniques to characterize the uranium plasma, effluent exhaust gases, and residue deposited on the test chamber and exhaust system components is reported.

Roman, W. C.↗
NASA NTRS1981

ATS-6 engineering performance report. Volume 2: Orbit and attitude controls

Attitude control is reviewed, encompassing the attitude control subsystem, spacecraft attitude precision pointing and slewing adaptive control experiment, and RF interferometer experiment. The spacecraft propulsion system (SPS) is discussed, including subsystem, SPS design description and validation, orbital operations and performance, in-orbit anomalies and contingency operations, and the cesium bombardment ion engine experiment. Thruster failure due to plugging of the propellant feed passages, a major cause for mission termination, are considered among the critical generic failures on the satellite.

Wales, R. O.↗
NASA NTRS1982

Fiber optic experiment for the Shuttle long-duration exposure facility

The present investigation is concerned with an active fiber-optic data transmission experiment which has been under development for a planned orbital exposure on the Shuttle Long Duration Exposure Facility (LDEF) and subsequent recovery for laboratory evaluation. The LDEF is a space shuttle payload which is designed to carry a large number of independent tray-mounted experiments into low earth orbit for exposure to the space environment. The LDEF is then to be recovered by a later shuttle flight for postflight examination. Data is stored on a tape recorder within the experiment tray; no telemetry is provided. A description is given of two independent experiment trays which are being prepared. The experiments are to be conducted to gain experience in the design of a complete fiber link for the space environment and to confirm that the effects of the critical environments in space, in particular particle radiation and temperature extremes, are not detrimental to satisfactory link operation.

Johnston, A. R.↗
NASA NTRS1985

Preparation for microgravity science investigation of compound semiconductor crystal growth

Preparatory work on Bridgman directional solidification (BDS) of PbSnTe crystals prior to microgravity crystal growth experiments on Shuttle flights are reported. Gravitational effects become important in crystal growth when density gradients are present. The situation is critical in BDS of PbSnTe because of the necessity of obtaining homogeneous compositional distributions, which can be disturbed when convective processes occur. Numerical models have been defined which quantify the effects of convection in the crystal growth solution. The models were verified by earth-based crystal-growth tests in a two-zone furnace using equal concentrations of each of the elements. Data are provided to demonstrate the differences in composition among crystals grown at different orientations to the gravitational field vector.

Fripp, A. L.↗
NASA NTRS1986

Protecting spacecraft from atomic oxygen

Findings are reported from Space Shuttle flights STS-3, 4, 5, and 8 regarding the degradation of materials exposed to atomic oxygen in low earth orbit. Atomic oxygen, a strong oxidizing agent, is present in low concentrations at such altitudes, and a spacecraft can sweep up considerable volumes of it at orbital velocities of 5 miles/s, especially if mission lifetimes are measured in years or decades. Material loss has been found to be a function of the fluence (the number of oxygen atoms striking a unit area of surface over a given period); fluence is proportional to atmospheric density, orbital velocity, surface attitude relative to velocity vector, and duration of exposure. Atmospheric density depends first on altitude and second on the phase of the 11-year solar activity cycle. Metals, in the experiments, reacted less than nonmetals. Graphs and a table are included, permitting calculation of how far a surface of various organic materials will recede on a spacecraft in low earth orbit. The limited data base on atomic oxygen interactions with materials, using both Shuttle flight experiments and ground-based facilities must be augmented. Space Station design is imminent, and the understanding of such interactions is critical to the success of that design.

Leger, L. J.↗
NASA NTRS1987

AIS-2 radiometry and a comparison of methods for the recovery of ground reflectance

A field experiment and its results involving Airborne Imaging Spectrometer-2 data are described. The radiometry and spectral calibration of the instrument are critically examined in light of laboratory and field measurements. Three methods of compensating for the atmosphere in the search for ground reflectance are compared. It was found that laboratory determined responsitivities are 30 to 50 percent less than expected for conditions of the flight for both short and long wavelength observations. The combined system atmosphere surface signal to noise ratio, as indexed by the mean response divided by the standard deviation for selected areas, lies between 40 and 110, depending upon how scene averages are taken, and is 30 percent less for flight conditions than for laboratory. Atmospheric and surface variations may contribute to this difference. It is not possible to isolate instrument performance from the present data. As for methods of data reduction, the so-called scene average or log-residual method fails to recover any feature present in the surface reflectance, probably because of the extreme homogeneity of the scene.

Conel, James E.↗
NASA NTRS1988

Mars sampling strategy and aeolian processes

It is critical that the geological context of planetary samples (both in situ analyses and return samples) be well known and documented. Apollo experience showed that this goal is often difficult to achieve even for a planet on which surficial processes are relatively restricted. On Mars, the variety of present and past surface processes is much greater than on the Moon and establishing the geological context of samples will be much more difficult. In addition to impact hardening, Mars has been modified by running water, periglacial activity, wind, and other processes, all of which have the potential for profoundly affecting the geological integrity of potential samples. Aeolian, or wind, processes are ubiquitous on Mars. In the absence of liquid water on the surface, aeolian activity dominates the present surface as documented by frequent dust storms (both local and global), landforms such as dunes, and variable features, i.e., albedo patterns which change their size, shape, and position with time in response to the wind.

Greeley, Ronald↗
NASA NTRS1990

Physiological adaptation to space flight

In space, adaptive physiological changes have been observed in virtually all body systems, but how far these changes progress with time is not known. Their time course demonstrates variable patterns; some systems show evidence of gradual and progressive change. Biomedical postflight data have shown that a compensatory period of readaptation to one gravity is required after space flight, with longer intervals required for longer missions. Consistent readaptation trends include orthostatic intolerance and neurovestibular difficulties. For the long-duration missions of the exploration era, it is critical to determine the extent to which deleterious changes (e.g., bone loss and possible immunological changes) can be reversed upon return to earth. Radiation protection is another critical enabling element for missions beyond low earth orbit. Radiation exposure guidelines have not been established for exploration missions. Currently our experience is insufficient to prescribe countermeasures for the stay times associated with a lunar base or a mission to Mars. Artificial gravity may provide a solution, but the level and duration of exposure necessary to prevent deconditioning must be determined. Central issues for medical care in remote settings are preventive, diagnostic, and therapeutic care and the minimization of risk.

Nicogossian, Arnauld E.↗
NASA NTRS1996

Second United States Microgravity Payload: One Year Report

The second United States Microgravity Payload (USMP-2), flown in March 1994, carried four major microgravity experiments plus a sophisticated accelerometer system. The USMP program is designed to accommodate experiments requiring extensive resources short of a full Spacelab mission. The four USMP-2 experiments dealt with understanding fundamental aspects of materials behavior, three with the formation of crystals from melts and one with the critical point of a noble gas. This successful, scientifically rich mission also demonstrated telescience operations.

Curreri, Peter A.↗
NASA NTRS1997

A Technology Plan for Enabling Commercial Space Business

The National Aeronautics and Space Administration's (NASA) Advanced Space Transportation Program is a customer driven, focused technology program that supports the NASA Strategic Plan and considers future commercial space business projections. The initial cycle of the Advanced Space Transportation Program implementation planning was conducted from December 1995 through February 1996 and represented increased NASA emphasis on broad base technology development with the goal of dramatic reductions in the cost of space transportation. The second planning cycle, conducted in January and February 1997, updated the program implementation plan based on changes in the external environment, increased maturity of advanced concept studies, and current technology assessments. The program has taken a business-like approach to technology development with a balanced portfolio of near, medium, and long-term strategic targets. Strategic targets are influenced by Earth science, space science, and exploration objectives as well as commercial space markets. Commercial space markets include those that would be enhanced by lower cost transportation as well as potential markets resulting in major increases in space business induced by reductions in transportation cost. The program plan addresses earth-to-orbit space launch, earth orbit operations and deep space systems. It also addresses all critical transportation system elements; including structures, thermal protection systems, propulsion, avionics, and operations. As these technologies are matured, integrated technology flight experiments such as the X-33 and X-34 flight demonstrator programs support near-term (one to five years) development or operational decisions. The Advanced Space Transportation Program and the flight demonstrator programs combine business planning, ground-based technology demonstrations and flight demonstrations that will permit industry and NASA to commit to revolutionary new space transportation systems beginning at the turn of the century and continuing far into the future.

Lyles, Garry M.↗
NASA NTRS1999

HEDS Goals

In November of 1996, NASA made the decision to fully integrate several areas of robotic and human Mars exploration study and planning. As a result of this decision, requirements for unmanned robotic missions to support human Mars exploration were identified and a plan to meet these requirements was developed. Concrete progress in the implementation of this plan has been made. Three experiments have been selected and are in development for the Mars Surveyor Program 2001 Orbiter and Lander missions which will provide critical data for the planning of human missions to Mars. An Announcement of Opportunity for the Mars Surveyor Program 2003 Lander mission has recently been released which solicited proposals related to planning for a human mission. In order to define HEDS objectives for Mars robotic missions, it is important to understand what information is required as a foundation for mounting a program of exploration of this magnitude. We identify areas of research on robotic missions that will enable future human missions. These areas include Site Selection for Human Missions, Hazards to Human Explorers, Living off the Land, and Testing Critical Technologies in the Mars Environment.

Pline, A.↗
NASA NTRS1999

Study of Flow of Superfluid He-II Very Near Tau(sub lambda)

We report here, preliminary data from an experiment studying flow of superfluid helium through a slit orifice (of sub-micron width) very close to T(sub lambda). Critical supercurrent (I(sub c)) data is obtained from a step function drive to the diaphragm in a Helmholtz resonator cell. The superfluid density (rho(sub s)) data can be obtained from the resonant frequency of the Helmholtz oscillator, as determined by transfer function of the resonator or from the free ringing after the step function excitation. Preliminary data shows that I(sub c) is proportional to (rho(sub s))(exp 1.27) and rho(sub s)) is proportional to tau(exp 0.73), where tau is the reduced temperature. However, the magnitude of I(sub c) is much larger than expected, indicating a possible parallel flow path. Further investigations are in progress. Keywords: superfluid; hydrodynamics; critical exponent

Mukharsky, Yury↗
NASA NTRS2004

Containerless Processing of a Lithium Disilicate Glass

Glasses of Li2O.2SiO2 (LS2), and LS2 doped with 0.001wt% platinum (LS2 + 0.001 wt% Pt) compositions were melted, cooled and reheated at controlled rates while levitated (containerless) inside an Electrostatic Levitator (ESL) furnace at the NASA Marshall Space Flight Center, Huntsville, AL. The experiments were conducted in vacuum (approximately 10(exp -5) Pa) using spherical, 2.5 to 3 millimeter diameter, glass samples. The measured critical cooling rate for glass formation, R(sub c), for the LS2 and LS2+0.001 wt% Pt glasses processed at ESL were 14 plus or minus 2 Celsius per minute and 130 plus or minus 5 Celsius per minute, respectively. The values of R(sub c), for the same LS2 and LS2 + 0.001 wt% Pt glasses processed in a container were 62 plus or minus 3 Celsius per minute and 162 plus or minus 5 Celsius per minute, respectively. The effective activation energy for crystallization, E, for this LS2 glass processed without a container at ESL, 392 plus or minus 15 kiloJoules per mole, was higher than that, 270 plus or minus 15 kiloJoules per mole, for an identical glass processed in a container. These results suggest that the glass formation tendency for a containerless LS2 melt is significantly increased compared to an identical melt in contact with a container. The absence of heterogeneous nucleation sites that are inherently present in all melts held in containers, and or a change in the surface composition due to evaporation of Li2O during processing at ESL are likely reasons for the increased glass forming tendency of this containerless LS2 melt.

Ranasinghe, Kisa↗
NASA NTRS2004

Bubble Combustion

A method of energy production that is capable of low pollutant emissions is fundamental to one of the four pillars of NASA s Aeronautics Blueprint: Revolutionary Vehicles. Bubble combustion, a new engine technology currently being developed at Glenn Research Center promises to provide low emissions combustion in support of NASA s vision under the Emissions Element because it generates power, while minimizing the production of carbon dioxide (CO2) and nitrous oxides (NOx), both known to be Greenhouse gases. and allows the use of alternative fuels such as corn oil, low-grade fuels, and even used motor oil. Bubble combustion is analogous to the inverse of spray combustion: the difference between bubble and spray combustion is that spray combustion is spraying a liquid in to a gas to form droplets, whereas bubble combustion involves injecting a gas into a liquid to form gaseous bubbles. In bubble combustion, the process for the ignition of the bubbles takes place on a time scale of less than a nanosecond and begins with acoustic waves perturbing each bubble. This perturbation causes the local pressure to drop below the vapor pressure of the liquid thus producing cavitation in which the bubble diameter grows, and upon reversal of the oscillating pressure field, the bubble then collapses rapidly with the aid of the high surface tension forces acting on the wall of the bubble. The rapid and violent collapse causes the temperatures inside the bubbles to soar as a result of adiabatic heating. As the temperatures rise, the gaseous contents of the bubble ignite with the bubble itself serving as its own combustion chamber. After ignition, this is the time in the bubble s life cycle where power is generated, and CO2, and NOx among other species, are produced. However, the pollutants CO2 and NOx are absorbed into the surrounding liquid. The importance of bubble combustion is that it generates power using a simple and compact device. We conducted a parametric study using CAVCHEM, a computational model developed at Glenn, that simulates the cavitational collapse of a single bubble in a liquid (water) and the subsequent combustion of the gaseous contents inside the bubble. The model solves the time-dependent, compressible Navier-Stokes equations in one-dimension with finite-rate chemical kinetics using the CHEMKIN package. Specifically, parameters such as frequency, pressure, bubble radius, and the equivalence ratio were varied while examining their effect on the maximum temperature, radius, and chemical species. These studies indicate that the radius of the bubble is perhaps the most critical parameter governing bubble combustion dynamics and its efficiency. Based on the results of the parametric studies, we plan on conducting experiments to study the effect of ultrasonic perturbations on the bubble generation process with respect to the bubble radius and size distribution.

Corrigan, Jackie↗
NASA NTRS2003

Risk-based analysis and decision making in multi-disciplinary environments

A risk-based decision-making process conceived of and developed at JPL and NASA, has been used to help plan and guide novel technology applications for use on spacecraft. These applications exemplify key challenges inherent in multi-disciplinary design of novel technologies deployed in mission-critical settings. 1) Cross-disciplinary concerns are numerous (e.g., spacecraft involve navigation, propulsion, telecommunications). These concems are cross-coupled and interact in multiple ways (e.g., electromagnetic interference, heat transfer). 2) Time and budget pressures constrain development, operational resources constrain the resulting system (e.g., mass, volume, power). 3) Spacecraft are critical systems that must operate correctly the first time in only partially understood environments, with no chance for repair. 4) Past experience provides only a partial guide: New mission concepts are enhanced and enabled by new technologies, for which past experience is lacking. The decision-making process rests on quantitative assessments of the relationships between three classes of information - objectives (the things the system is to accomplish and constraints on its operation and development), risks (whose occurrence detracts from objectives), and mitigations (options for reducing the likelihood and or severity of risks). The process successfully guides experts to pool their knowledge, using custom-built software to support information gathering and decision-making.

technology↗
NASA NTRS2011

Assessment of Antarctic Ice-Sheet Mass Balance Estimates: 1992 - 2009

Published mass balance estimates for the Antarctic Ice Sheet (AIS) lie between approximately +50 to -250 Gt/year for 1992 to 2009, which span a range equivalent to 15% of the annual mass input and 0.8 mm/year Sea Level Equivalent (SLE). Two estimates from radar-altimeter measurements of elevation change by European Remote-sensing Satellites (ERS) (+28 and -31 Gt/year) lie in the upper part, whereas estimates from the Input-minus-Output Method (IOM) and the Gravity Recovery and Climate Experiment (GRACE) lie in the lower part (-40 to -246 Gt/year). We compare the various estimates, discuss the methodology used, and critically assess the results. Although recent reports of large and accelerating rates of mass loss from GRACE=based studies cite agreement with IOM results, our evaluation does not support that conclusion. We find that the extrapolation used in the published IOM estimates for the 15 % of the periphery for which discharge velocities are not observed gives twice the rate of discharge per unit of associated ice-sheet area than the 85% faster-moving parts. Our calculations show that the published extrapolation overestimates the ice discharge by 282 Gt/yr compared to our assumption that the slower moving areas have 70% as much discharge per area as the faster moving parts. Also, published data on the time-series of discharge velocities and accumulation/precipitation do not support mass output increases or input decreases with time, respectively. Our modified IOM estimate, using the 70% discharge assumption and substituting input from a field-data compilation for input from an atmospheric model over 6% of area, gives a loss of only 13 Gt/year (versus 136 Gt/year) for the period around 2000. Two ERS-based estimates, our modified IOM, and a GRACE-based estimate for observations within 1992 to 2005 lie in a narrowed range of +27 to - 40 Gt/year, which is about 3% of the annual mass input and only 0.2 mm/year SLE. Our preferred estimate for 1992-2001 is - 47 Gt/year for West Antarctica, + 16 Gt/year for East Antarctica, and -31 Gt/year overall (+0.1 mm/year SLE), not including part of the Antarctic Peninsula (1.07 % of the AIS area)

Zwally, H. Jay↗