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302 records · Page 17
All sourcesNASA NTRSDOE OSTI
NASA NTRS2024

Characterization of NUW-LHT-5m, A Lunar Highland Simulant

A new simulant of the lunar highlands regolith, NUW-LHT-5M, was designed by NASA and manufactured by Washington Mills. The simulant was based on Apollo 16 data and is a member of the NU-LHT-series. NASA’s Marshall Space Flight Center and Johnson Space Center have already purchased 3 metric tons of the simulant for advanced engineering work. In support of engineering uses of the simulant, we provided measurements of the simulant including: mineral abundance and composition, liberation, X-ray fluorescence (XRF), ferrous iron, carbon, sulfur, 60 element inductively coupled plasma (ICP), loss on ignition, particle size, both 2D and 3D particle shape, specific surface area, shear, cohesion, internal friction, helium pycnometry, minimum index density, tap density, magnetic susceptibility, cryogenic and high temperature permittivity, visible and near-infrared (VNIR) and middle infra-red spectroscopy (MIR), differential scanning calorimetry (DSC), viscosity, thermal diffusivity, thermal conductivity, thermal gravimetric analysis (TGA), evolved gas analysis (EGA), and spark sintering. For the crystalline components the design of the simulant called for two rocks from the Stillwater Complex, Montana: 17.6 wt% norite, 37.7% anorthosite, and 4.7 wt% olivine from an unspecified commercial source. The other 40% of the simulant was a high calcium (An100), vesicular glass that Washington Mills made specifically for the simulant. Fabrication and quality control processes for both the glass and the simulant are described. Importantly, most of the graphs and tables presented herein provide values for both the new simulant and data for the older NASA mare simulant, JSC-1A. Finally, we discussed the current limitations of NUW-LT-5M and most other lunar regolith simulants to replicate the lunar material.

lunar regolith simulant↗
NASA NTRS2019

Laboratory Scale Testing of Ignition Overpressure for Space Vehicle Launch Pad Environments

A scale model of a NASA representative space vehicle is used to develop a refined estimate of the transient pressure loads that are expected to form at the base of the vehicle in the event of a vapor cloud explosion. Flammable vapor clouds are known to form prior to engine startup due to the significant amount of unburned hydrogen that is ejected from the combustion chamber. In the event of a vapor cloud explosion, the vehicle and payload must be able to withstand the resulting overpressure waves. The study comprises an array of pressure sensors located along the base heat shield of the scale model space vehicle as well as the interior wall and throat plug plane of the solid rocket booster. A spark source generator is used to simulate the overpressure wave produced by a vapor cloud explosion while measurements are acquired with and without the effect of a mobile launcher. Time- resolved schlieren images of the simulated vapor cloud explosion reveal the path and impact of both the initial wave and several reflected waves on the various components at the base of the space vehicle. In some instances, the reflected waves superpose to create waves that are higher in amplitude than the initial overpressure wave. A time frequency analysis of the pressure waveforms measured inside the solid rocket booster reveal a ring down tone corresponding to a standing wave that is four times the length of the nozzle.

Tinney, Charles E.↗
NASA NTRS1928

Combustion time in the engine cylinder and its effect on engine performance

As part of a general program to study combustion in the engine cylinder and to correlate the phenomena of combustion with the observed performance of actual engines, this paper presents a sketchy outline of what may happen in the engine cylinder during the burning of a charge. It also suggests the type of information needed to supply the details of the picture and points out how combustion time and rate affect the performance of the engine. A theoretical concept of a flame front which is assumed to advance radially from the point of ignition is presented, and calculations based on the area and velocity of this flame and the density of the unburned gases are made to determine the mass rate of combustion. From this rate the mass which has been burned and the pressure at any instant during combustion are computed. This process is then reversed in an effort to determine actual rates of combustion and flame velocities from the pressures as recorded on indicator diagrams. The effects of different rates of combustion on engine performance are then discussed and the importance of proper spark advance is emphasized.

Marvin, Charles F , Jr↗
NASA NTRS1933

The NACA Apparatus for Studying the Formation and Combustion of Fuel Sprays and the Results from Preliminary Tests

This report describes the apparatus as designed and constructed at the Langley Memorial Aeronautical Laboratory, for studying the formation and combustion of fuel sprays under conditions closely simulating those occurring in a high-speed compression-ignition engine. The apparatus consists of a single-cylinder modified test engine, a fuel-injection system so designed that a single charge of fuel can be injected into the combustion chamber of the engine, an electric driving motor, and a high-speed photographic apparatus. The cylinder head of the engine has a vertical-disk form of combustion chamber whose sides are glass windows. When the fuel is injected into the combustion chamber, motion pictures at the rate of 2,000 per second are taken of the spray formation by means of spark discharges. When combustion takes place the light of the combustion is recorded on the same photographic film as the spray photographs. The report includes the results of some tests to determine the effect of air temperature, air flow, and nozzle design on the spray formation.

Rothrock, A M↗
NASA NTRS1979

CNO isotope production in nova outbursts

A current model of novae is presented which explains their outbursts assuming that the progenitor of a common nova is a carbon-oxygen dwarf. This white dwarf accretes H-rich material from its companion which produces strong shock waves at its surface; as the amount of accreted material increases later, its bottom ignites. The nova outburst is then triggered by CNO-Ne reactions which favor the formation of rare isotopes with proton-rich radioactive parents such as C-13, N-15, O-17, and Ne-21. The production of such nuclear species is examined in different nova models, and conclusions are drawn concerning the importance of novae in models of chemical evolution of the galaxy.

Audouze, J.↗
NASA NTRS2009

Determination of Pass/Fail Criteria for Promoted Combustion Testing

Promoted ignition testing is used to determine the relative flammability of metal rods in oxygen-enriched atmospheres. In these tests, a promoter is used to ignite each metal rod to start the sample burning. Experiments were performed to better understand the promoted ignition test by obtaining insight into the effect a burning promoter has on the preheating of a test sample. Test samples of several metallic materials were prepared and coupled to fast-responding thermocouples along their length. Various ignition promoters were used to ignite the test samples. The thermocouple measurements and test video was synchronized to determine temperature increase with respect to time and length along each test sample. A recommended length of test sample that must be consumed to be considered a flammable material was determined based on the preheated zone measured from these tests. This length was determined to be 30 mm (1.18 in.). Validation of this length and its rationale are presented.

Sparks, Kyle M.↗
NASA NTRS2012

Flow Friction or Spontaneous Ignition?

"Flow friction," a proposed ignition mechanism in oxygen systems, has proved elusive in attempts at experimental verification. In this paper, the literature regarding flow friction is reviewed and the experimental verification attempts are briefly discussed. Another ignition mechanism, a form of spontaneous combustion, is proposed as an explanation for at least some of the fire events that have been attributed to flow friction in the literature. In addition, the results of a failure analysis performed at NASA Johnson Space Center White Sands Test Facility are presented, and the observations indicate that spontaneous combustion was the most likely cause of the fire in this 2000 psig (14 MPa) oxygen-enriched system.

Stoltzfus, Joel M.↗
NASA NTRS2008

New Techniques to Evaluate the Incendiary Behavior of Insulators

New techniques for evaluating the incendiary behavior of insulators is presented. The onset of incendive brush discharges in air is evaluated using standard spark probe techniques for the case simulating approaches of an electrically grounded sphere to a charged insulator in the presence of a flammable atmosphere. However, this standard technique is unsuitable for the case of brush discharges that may occur during the charging-separation process for two insulator materials. We present experimental techniques to evaluate this hazard in the presence of a flammable atmosphere which is ideally suited to measure the incendiary nature of micro-discharges upon separation, a measurement never before performed. Other measurement techniques unique to this study include; surface potential measurements of insulators before, during and after contact and separation, as well as methods to verify fieldmeter calibrations using a charge insulator surface opposed to standard high voltage plates. Key words: Kapton polyimide film, incendiary discharges, brush discharges, contact and frictional electrification, ignition hazards, insulators, contact angle, surface potential measurements.

Buhler, Charles↗
NASA NTRS1975

Accretion and the nova outburst

Evolutionary sequences of thermonuclear runaways in the hydrogen-rich envelopes of carbon-oxygen white dwarfs are presented which include the effects of accretion of infalling material, allow the initial envelope to be out of equilibrium, and reproduce the gross features of the nova outburst. The models show that massive infall rates produce strong shocks at the stellar surface, that material passing through the shocks reaches nuclear-ignition temperatures, and that the thermonuclear runaway proceeds with an extended envelope around the star in the most extreme cases. The major effect of accretion is found to be a reduction in the amount of material ejected for a given degree of CNO enhancement as compared with previous nonaccretion models. It is also found that all the heating that causes ejection occurs in the deeper layers and that the light curves produced by the present models are in closer agreement with observed nova light curves that the previous models.

Starrfield, S. G.↗
NASA NTRS2010

Oxygen Compatibility Assessment of Components and Systems

Fire hazards are inherent in oxygen systems and a storied history of fires in rocket engine propulsion components exists. To detect and mitigate these fire hazards requires careful, detailed, and thorough analyses applied during the design process. The oxygen compatibility assessment (OCA) process designed by NASA Johnson Space Center (JSC) White Sands Test Facility (WSTF) can be used to determine the presence of fire hazards in oxygen systems and the likelihood of a fire. This process may be used as both a design guide and during the approval process to ensure proper design features and material selection. The procedure for performing an OCA is a structured step-by-step process to determine the most severe operating conditions; assess the flammability of the system materials at the use conditions; evaluate the presence and efficacy of ignition mechanisms; assess the potential for a fire to breach the system; and determine the reaction effect (the potential loss of life, mission, and system functionality as the result of a fire). This process should be performed for each component in a system. The results of each component assessment, and the overall system assessment, should be recorded in a report that can be used in the short term to communicate hazards and their mitigation and to aid in system/component development and, in the long term, to solve anomalies that occur during engine testing and operation.

Stoltzfus, Joel↗
NASA NTRS2016

Failure Simulation Testing of the Z-1 Spacesuit Titanium Bearing Assemblies

The Z-2 is a candidate for NASA's next generation spacesuit, designed for a range of possible missions with enhanced mobility for spacewalks both on planetary surfaces and in microgravity. Increased mobility was accomplished through innovations in shoulder and hip joints, using a number of new bearings to allow spacesuit wearers to dip, walk, and bend with ease; all important tasks for a planetary explorer collecting samples or traveling over rough terrain. The Advanced Spacesuit Development Team of NASA Johnson Space Center requested that the NASA White Sands Test Facility (WSTF) perform a series failure simulation tests on three titanium bearing assemblies, an elemental part of the joint construction used in new spacesuit designs. This testing simulated two undetected failures within the bearings and as a result the objective of this test program was to evaluate whether a failed or failing bearing could result in ignition of the titanium race material due to friction. The first failure was an inner seal leak sufficient to pressurize the race with +99 percent oxygen. The second failure was an improperly installed or mismatched ball port that created a protrusion in the ball bearing race, partially obstructing the nominal rolling path of each ball bearing. When the spacesuit bearings are assembled, bearing balls are loaded into the assembly via a ball port. The ball port is specific and unique to each bearing assembly (matched pair). The simulated mismatched ball port is a significant source of friction, which would be caused by an assembly error. To evaluate this risk, the bearings were cycled in a simulated worst-case scenario environment, with operational loads, and potential flaw conditions. During test the amount of actuation torque required and heat generated through continuous operation were measured and the bearings were observed for sparks or burning events. This paper provides detailed descriptions of the test hardware, methodology, and results.

de Baca, Richard C.↗
NASA NTRS1980

Theoretical studies of massive stars. II - Evolution of a 15 solar-mass star from carbon shell burning to iron core collapse

The evolution of a Population I star of 15 solar masses is described from the carbon shell burning stage to the formation and collapse of an iron core. An unusual aspect of the evolution is that neon ignition occurs off-center and neon burning propagates inward by a series of shell flashes. The extent of the core burning is generally smaller than the Chandrasekhar mass, so that most of the nuclear energy generation occurs in shell sources. Because of degeneracy and the influence of rapid convective mixing, these shell sources are unstable and the core goes through large excursions in temperature and density. The small core also causes the shell sources to converge into a narrow mass region slightly above the Chandrasekhar mass. Thus, the final nucleosynthesis yields are generally small, with silicon being most strongly enhanced with respect to solar system abundances.

Sparks, W. M.↗
NASA NTRS1991

Liquid oxygen/metal gelled monopropellants

The objectives of this program were to establish the feasibility of metallized/liquid oxygen monopropellants and select the best monopropellant formulation for continued study. The metal powders mixed with the liquid oxygen were aluminum/magnesium (80/20), silicon and iron (Iron was only tested for burning properties). The formulations were first evaluated on whether they detonated when ignited or burned. The formulations only burned when ignited. The viscosity for the formulations ranged from 900 cps to 100 cps at shear rates up to 300 seconds(sup -1). Two percent (by weight) of Cab-O-Sil was added to the aluminum and aluminum/magnesium formulations for gelling while the silicon formulation used three percent. Within a seven hour period, settling was suggested only in the 29 percent aluminum and 29 percent aluminum/magnesium formulations. The monopropellants were burned in a cylinder submerged in a liquid nitrogen bath. Experimental data at ambient pressure indicated that the monopropellants were extinguished when the flame front reached regions submerged under the liquid nitrogen. The burn rate increased dramatically when burned in a cylinder enclosure with less heat sink available to the monopropellant. The test results were inconclusive as to whether the increased burn rate was due to the lower heat sink capacity or the small amount of pressure (2 psi) generated during the burning of the monopropellant. The burning of the aluminum and aluminum/magnesium resulted in a brilliant white flame similar to that of an arc welder. These monopropellants burned in a pulsating manner with the aluminum/magnesium appearing to have less pulsating combustion. The silicon monopropellant burned with an orange glow. No sparks or energetic burning was apparent as with the aluminum or aluminum/magnesium.

Wickman, John H.↗
NASA NTRS2010

Heat Effects of Promoters and Determination of Burn Criterion in Promoted Combustion Testing

Promoted ignition testing (NASA Test 17) [1] is used to determine the relative flammability of metal rods in oxygen-enriched atmospheres. A promoter is used to ignite a metal sample rod, initiating sample burning. If a predetermined length of the sample burns, beyond the promoter, the material is considered flammable at the condition tested. Historically, this burn length has been somewhat arbitrary. Experiments were performed to better understand this test by obtaining insight into the effect a burning promoter has on the preheating of a test sample. Test samples of several metallic materials were prepared and coupled to fast-responding thermocouples along their length. Thermocouple measurements and test video were synchronized to determine temperature increase with respect to time and length along each test sample. A recommended flammability burn length, based on a sample preheat of 500 F, was determined based on the preheated zone measured from these tests. This length was determined to be 30 mm (1.18 in.). Validation of this length and its rationale are presented.

Sparks, Kyle M.↗