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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 397 records · Page 22
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Theoretical spectral distributions and total cross sections for neutral subthreshold pion production in carbon-carbon collisions

A coherent isobar formalism is employed to model subthreshold production of neutral pions in carbon-carbon collisions at energies below 100 MeV/nucleon. No arbitrary scale factors or adjustable free parameters are used in calculation of the Lorentz-invariant cross sections for pion production in the projectile, which produces an excited state that goes to M1 resonance in the target by conservation of spin and isospin. Pion production is also modeled for the projectile, which also reaches M1 resonance. The overall pion spectral distribution in the center of mass system is then integrated over the energy range 35-84 MeV/nucleon. The results expose an energy loss in the incident ions, as observed experimentally, and indicate that an isobar mechanism is responsible for higher energy pion production. Lower energy pions are a result of thermal processes.

Norbury, J. W.↗
NASA NTRS1985

Impact experiments. I - Ejecta velocity distributions and related results from regolith targets

Results are reported of laboratory measurements of the velocity distributions of powdery ejecta of 14 impacts into powders simulating regolith in near vacuum. The impact velocities ranged from 5-2321 m/sec, a velocity range believed prevalent in the early solar system. The powder was mechanically similar to lunar regolith. The projectiles comprised harder materials than the regolith, i.e., pyrex spheres, basalt spheres and cylinders, and igneous rocks. High-speed photography was employed to record the events. The differences between the present results and those from hypervelocity impacts are discussed in detail. Notably, an impact velocity threshold was detected between 10-30 m/sec, below which the amount of ejecta is less than the projectile mass.

Hartmann, W. K.↗
NASA NTRS1986

Laser-photodetector timing station instruction and maintenance manual

A laser photodetector station is used for detecting the arrival of a projectile at a specific point along a ballistic range. The system can be employed on either an open or evacuated range, with small projectiles, and at hypervelocities. The setup procedures, maintenance, and system components are described.

Strader, E. A.↗
NASA NTRS1986

A planetary ultra hypervelocity impact mechanics and shock wave science facility

Using the concept of intercepting orbits from a pair of Space Station serviced free flyers, a class of impact and shock wave experiments pertinent to planetary science can be performed. One proposed free flying vehicle is an impactor dispensor, and the second is the impact laboratory. How collision is achieved by utilizing essentially twice orbital velocity is demonstrated. The impactor dispensor contains a series of small flyer plates or other projectiles which are launched into the trajectory of the impactor laboratory at appropriate positions. The impactor laboratory is a large impact tank similar to those in terrestrial gun laboratories, except that it contains a supply of targets and instrumentation such as high speed cameras, flash X-ray apparatus and digital recorders. Shock and isentropic pressures of up to 20 Mbar are achievable with such a system which provides 15 km/sec impact velocities for precisely oriented projectiles.

Ahrens, T. J.↗
NASA NTRS1986

Acoustic penetration and impact detector for micrometeoroid and space debris application

The Two-Stage Acoustic Penetration and Impact Detector is a simple device for measuring the impact event time, the projectile velocity, the flight path direction and the momentum. The results of laboratory tests have shown that this detector can be used in a wide range of projectile size and velocity. According to measurement purposes the size of the detection area, the distance between the front foil and the target plate and the number of microphones as well as the evaluation procedure can easily be adjusted. The target plate area can also be replaced by another foil detector, if two penetration stages are preferred. This active detector is suitable for a variety of applications in meteoroid and space debris exploration. It can also be supplied with capture cell properties for chemical analysis of inside-deposits. Therefore, this measurement principal has been taken into consideration as a possible flight experiment for instance for a later Longer Duration Exposure Facility (LDEF) flight or future space station activities.

Kuzcera, H.↗
NASA NTRS1985

Calculation of recoil implantation profiles using known range statistics

A method has been developed to calculate the depth distribution of recoil atoms that result from ion implantation onto a substrate covered with a thin surface layer. The calculation includes first order recoils considering projected range straggles, and lateral straggles of recoils but neglecting lateral straggles of projectiles. Projectile range distributions at intermediate energies in the surface layer are deduced from look-up tables of known range statistics. A great saving of computing time and human effort is thus attained in comparison with existing procedures. The method is used to calculate recoil profiles of oxygen from implantation of arsenic through SiO2 and of nitrogen from implantation of phosphorus through Si3N4 films on silicon. The calculated recoil profiles are in good agreement with results obtained by other investigators using the Boltzmann transport equation and they also compare very well with available experimental results in the literature. The deviation between calculated and experimental results is discussed in relation to lateral straggles. From this discussion, a range of surface layer thickness for which the method applies is recommended.

Fung, C. D.↗
NASA NTRS1986

Origin of the earth's moon - Constraints from alkali volatile trace elements

Although the moon is depleted in volatile elements compared to the earth, these depletions are not in accord with simple volatility. For example, the Cs/Rb ratios of the earth and moon inferred from basalt are approximately one seventh and one half of the CI ratio, respectively. Volatility considerations alone predict that the lunar Cs/Rb ratio should be equal to or lower than the terrestrial ratio if the moon was derived entirely from earth mantle material. Thus hypotheses such as rotational fission which invoke derivation of lunar material entirely from the earth's mantle may be excluded. The collisional ejection hypothesis of lunar origin requires at least 18 percent of lunar material to be derived from a projectile with dehydrated CI composition to match the lunar Cs/Rb ratio, and 25-50 percent to match both the lunar Cs/Rb ratio and absolute concentrations of Cs and Rb. It remains to be demonstrated that this relatively large contribution of projectile material is consistent with other elemental abundances and element ratios in the moon.

Kreutzberger, M. E.↗
NASA NTRS1986

Stoichiometric disturbances in compound semiconductors due to ion implantation

A method is developed to calculate the depth distribution of the local stoichiometric disturbance (SD) resulting from ion implantation in binary-compound substrates. The calculation includes first-order recoils considering projected range straggle of projectiles and recoils and lateral straggle of recoils. The method uses tabulated final-range statistics to infer the projectile range distributions at intermediate energies. This approach greatly simplifies the calculation with little compromise on accuracy as compared to existing procedures. As an illustration, the SD profile is calculated for implantation of boron, silicon, and aluminum in silicon carbide. The results for the latter case suggest that the SD may be responsible for otherwise unexplained distortions in the annealed aluminum profile. A comparison with calculations by other investigators using the Boltzmann transport equation shows good agreement.

Avila, R. E.↗
NASA NTRS1987

A space debris simulation facility for spacecraft materials evaluation

A facility to simulate the effects of space debris striking an orbiting spacecraft is described. This facility was purchased in 1965 to be used as a micrometeoroid simulation facility. Conversion to a Space Debris Simulation Facility began in July 1984 and it was placed in operation in February 1985. The facility consists of a light gas gun with a 12.7-mm launch tube capable of launching 2.5-12.7 mm projectiles with a mass of 4-300 mg and velocities of 2-8 km/sec, and three target tanks of 0.067 m, 0.53 a m and 28.5 a m. Projectile velocity measurements are accomplished via pulsed X-ray, laser diode detectors, and a Hall photographic station. This facility is being used to test development structural configurations and candidate materials for long duration orbital spacecraft. A summary of test results are also described.

Taylor, Roy A.↗
NASA NTRS1987

Bolide impacts, acid rain, and biospheric traumas at the Cretaceous-Tertiary boundary

Two plausible projectiles are considered: an ice-rich long-period comet and a much smaller rock-metal asteroid. In the framework of a proposal addressed by Lewis et al. (1982), it is shown that, while the impact projectiles themselves do not shock-heat the atmosphere very extensively, the supersonic plume of water vapor and rock produced on impact does shock the atmosphere up to global scales and the shock is of sufficient intensity to produce abundant nitric oxide. For example, an ice-rich long-period comet with a mass of 1.25 x 10 to the 16th kg and a velocity of 65 km/s striking the earth would produce about 7 x 10 to the 40th molecules NO through shock-heating of the atmosphere by the high-velocity ejecta plume fragments. Specific attention is given to the fraction of the atmosphere shock-heated, the global circulation of the nitrogen oxides, the effects of the ejecta plume water on acid rain (AR) predictions, the effects of AR on continental soils, the relationship between AR production rates and the total amount of acid needed to acidify the surface oceans, and the longevity of the oceanic acidity event and the exhaled CO2 event and their implications for the environment in the first millenia or so after the impact.

Prinn, Ronald G.↗
NASA NTRS1987

Numerical simulation of three dimensional transonic flows

The three-dimensional flow over a projectile has been computed using an implicit, approximately factored, partially flux-split algorithm. A simple composite grid scheme has been developed in which a single grid is partitioned into a series of smaller grids for applications which require an external large memory device such as the SSD of the CRAY X-MP/48, or multitasking. The accuracy and stability of the composite grid scheme has been tested by numerically simulating the flow over an ellipsoid at angle of attack and comparing the solution with a single grid solution. The flowfield over a projectile at M = 0.96 and 4 deg angle-of-attack has been computed using a fine grid, and compared with experiment.

Sahu, Jubaraj↗
NASA NTRS1988

Rain simulation studies for high-intensity acoustic nose cavities

Unarmed plastic projectiles can be equipped with small axisymmetric cavities for the generation of intense tones that are useful in training maneuvers. Attention is presently given to the simulation of rainfall in an airstream and the effect of rain droplet impingement on the nose of projectiles, and especially to any penetration or accumulation of water at the base of the cavity that might increase the fundamental cavity frequency and/or reduce the intensity of sound production during rain conditions.

Clayton, R. M.↗
NASA NTRS1989

Inductively-Activated Short-Interval Timer

Timing circuit in pneumatically launched projectile triggers explosive charge in projectile at specified delay after launch. Both power and control signals coupled inductively to timer from stationary launcher circuitry. Eliminates need for direct electrical contacts, which are unreliable and generate sparks that trigger explosive accidentally. Inductive coupling also provides higher reliability in field operation than contacts. Concept useful in such other safety-related applications as remotely or automatically controlling flow of bottled flammable gas.

Wiker, Gordon A.↗
NASA NTRS1987

A planetary ultra hypervelocity impact mechanics and shock wave science facility

Using the concept of intercepting orbits from a pair of Space Station serviced free flyers, a class of impact and shock wave experiments pertinent to planetary science can be performed. One proposed free flying vehicle is an impactor dispensor, and the second is the impact laboratory. How collision is achieved by utilizing essentially twice orbital velocity is demonstrated. The impactor dispensor contains a series of small flyer plates or other projectiles which are launched into the trajectory of the impactor laboratory at appropriate positions. The impactor laboratory is a large impact tank similar to those in terrestrial gun laboratories, except that it contains a supply of targets and instrumentation such as high speed cameras, flash X-ray apparatus, and digital recorders. Shock and isentropic pressures of up to 20 Mbar are achievable with such a system which provides 15 km/sec impact velocities for precisely oriented projectiles.

Ahrens, Thomas J.↗
NASA NTRS1988

Further investigations of oblique hypervelocity impact phenomena

The results of a continuing investigation of the phenomena associated with the oblique hypervelocity impact of spherical projectiles onto multi-sheet aluminum structures are described. A series of equations that quantitatively describes these phenomena is obtained through a regression of experimental data. These equations characterize observed ricoshet and penetration damage phenomena in a multi-sheet structure as functions of the geometric parameters of the structure and the diameter, obliquity, and velocity of the impacting projectile. Crater damage observed on the ricochet witness plates is used to determine the sizes and speeds of the ricochet debris particles that caused the damage. It is shown that, in general, the most damaging ricochet debris particle is approximately 0.25 cm (0.10 in) in diameter and travels at the speed of approximately 2.1 km/sec (6,890 ft/sec). The equations necessary for the design of shielding panels that will protect external systems from such ricochet debris damage are also developed. The dimensions of these shielding panels are shown to be strongly dependent on their inclination and on their circumferential distribution around the spacecraft. It is concluded that obliquity effects of high-speed impacts must be considered in the design of any structure exposed to the meteoroid and space debris environment.

Schonberg, William P.↗
NASA NTRS1988

Coffee-can-sized spacecraft

The current status and potential scientific applications of intelligent 1-5-kg projectiles being developed by SDIO and DARPA for military missions are discussed. The importance of advanced microelectronics for such small spacecraft is stressed, and it is pointed out that both chemical rockets and EM launchers are currently under consideration for these lightweight exoatmospheric projectiles (LEAPs). Long-duration power supply is identified as the primary technological change required if LEAPs are to be used for interplanetary scientific missions, and the design concept of a solar-powered space-based railgun to accelerate LEAPs on such missions is considered.

Jones, Ross M.↗
NASA NTRS1989

Nuclear collective flow and charged-pion emission in Ne-nucleus collisions at E/A = 800 MeV

Triple-differential cross sections of charged pions were measured for collisions of Ne projectiles at E/A = 800 MeV with NaF, Nb, and Pb targets. The reaction plane was estimated event by event from the light-baryon momentum distribution. For heavy targets, preferential emission of charged pions away from the interaction zone toward the projectile side was observed in the transverse direction. Such a preferential emission, which is not predicted by cascade calculations, may be attributed to a stronger pion absorption by the heavier spectator remnant.

Gosset, J.↗