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All sourcesNASA NTRSDOE OSTI
NASA NTRS2012

NASA's Space Launch System (SLS) Program: Mars Program Utilization

NASA's Space Launch System is being designed for safe, affordable, and sustainable human and scientific exploration missions beyond Earth's orbit (BEO), as directed by the NASA Authorization Act of 2010 and NASA's 2011 Strategic Plan. This paper describes how the SLS can dramatically change the Mars program's science and human exploration capabilities and objectives. Specifically, through its high-velocity change (delta V) and payload capabilities, SLS enables Mars science missions of unprecedented size and scope. By providing direct trajectories to Mars, SLS eliminates the need for complicated gravity-assist missions around other bodies in the solar system, reducing mission time, complexity, and cost. SLS's large payload capacity also allows for larger, more capable spacecraft or landers with more instruments, which can eliminate the need for complex packaging or "folding" mechanisms. By offering this capability, SLS can enable more science to be done more quickly than would be possible through other delivery mechanisms using longer mission times.

May, Todd A.↗
NASA NTRS2015

Iodine Satellite

The Iodine Satellite (iSat) spacecraft will be the first CubeSat to demonstrate high change in velocity from a primary propulsion system by using Hall thruster technology and iodine as a propellant. The mission will demonstrate CubeSat maneuverability, including plane change, altitude change and change in its closest approach to Earth to ensure atmospheric reentry in less than 90 days. The mission is planned for launch in fall 2017. Hall thruster technology is a type of electric propulsion. Electric propulsion uses electricity, typically from solar panels, to accelerate the propellant. Electric propulsion can accelerate propellant to 10 times higher velocities than traditional chemical propulsion systems, which significantly increases fuel efficiency. To enable the success of the propulsion subsystem, iSat will also demonstrate power management and thermal control capabilities well beyond the current state-of-the-art for spacecraft of its size. This technology is a viable primary propulsion system that can be used on small satellites ranging from about 22 pounds (10 kilograms) to more than 1,000 pounds (450 kilograms). iSat's fuel efficiency is ten times greater and its propulsion per volume is 100 times greater than current cold-gas systems and three times better than the same system operating on xenon. iSat's iodine propulsion system consists of a 200 watt (W) Hall thruster, a cathode, a tank to store solid iodine, a power processing unit (PPU) and the feed system to supply the iodine. This propulsion system is based on a 200 W Hall thruster developed by Busek Co. Inc., which was previously flown using xenon as the propellant. Several improvements have been made to the original system to include a compact PPU, targeting greater than 80 percent reduction in mass and volume of conventional PPU designs. The cathode technology is planned to enable heaterless cathode conditioning, significantly increasing total system efficiency. The feed system has been designed to include iodine compatible control valves with internal heaters and temperature sensors to coincide with the iodine-compatible thruster. A key advantage to using iodine as a propellant is that it may be stored in the tank as an unpressurized solid on the ground and before flight operations. During operations, the tank is heated to vaporize the propellant. Iodine vapor is then routed through custom flow control valves to control mass flow to the thruster and cathode assembly. The thruster then ionizes the vapor and accelerates it via magnetic and electrostatic fields, resulting in high specific impulse, characteristic of a highly efficient propulsion system. The iSat spacecraft is a 12-unit (12U) CubeSat with dimensions of about 8 inches x 8 inches x 12 inches (20 centimeters x 20 centimeters x 30 centimeters). The spacecraft frame will be constructed from aluminum with a finish to prevent iodine-driven corrosion. The iSat spacecraft includes full three-axis control and will leverage heat generated by spacecraft components and radiators for a passive thermal control system. After the CubeSat has successfully detached from its launch vehicle, it will deploy its solar panels, correct for tip-off and maintain attitude control before ground contact. An initial check-out period of two weeks is planned for testing all subsystems. The spacecraft will charge the power system while in sunlight, using momentum wheels and magnetic torque rods to rotate the vehicle to the required attitude.

iSat↗
NASA NTRS1988

Discovery of very high velocity outflow in V Hydra - Wind from an accretion disk in a binary?

High-resolution observations of lines from the CO v = 1-0 vibration-rotation band at 4.6 microns, taken with the FTS/KPNO 4-m telescope, are reported for the carbon-rich red giant V Hydra, which is surrounded by an extended expanding molecular envelope resulting from extensive mass loss. The spectrum shows, in addition to the expected absorption at the outflow velocity of the envelope, absorption extending up to 120 km/s bluewards of the stellar velocity. A comparison of the spectrum observed at two epochs shows that the high-velocity absorption features change with time. It is suggested that the observed high-velocity features in V Hydra arise in a high-velocity polar outflow from an accretion disk in a binary system, as proposed in the mass-loss model for bipolar envelopes by Morris (1988).

Sahai, R.↗
NASA NTRS1975

Pioneer Jupiter Orbiter/Probe mission. I - Spacecraft system description

This paper discusses the Pioneer Jupiter Orbiter/Probe mission with emphasis on the orbiter spacecraft system. In this mission, the atmosphere of Jupiter will be investigated for physical and chemical structure by a probe which survives entry and transmits data while descending below the 10-bar level. The spacecraft deflects after probe separation to a nonimpacting approach trajectory, acts as a communications relay for data from the descending probe, and propulsively enters an orbit about Jupiter. As an orbiter, it explores the environment of Jupiter for three years, making in situ measurements of the particles and fields of the Jovian magnetosphere together with remote measurements (including images) of Jupiter and the Galilean satellites. The spacecraft system is logically based on the design of Pioneers 10 and 11 with modifications for these different mission requirements: antenna, receiver, and memory for the probe-spacecraft data link; a retropropulsion system for the high velocity-change requirements of orbit insertion; a data system consistent with the requirements of a line-scan imaging system; and an improved complement of radioisotope-thermoelectric-generator power sources to provide adequate power six years after launch.

Lassen, H. A.↗
NASA NTRS1981

Comparisons between optical and ultraviolet interstellar lines formed in the Carina Nebula (NGC 3372)

Discovery of complex Ca II H and K interstellar line profiles towards stars embedded in the giant H II region surrounding Eta Carinae led to a reconnaissance of the richer ultraviolet (UV) interstellar line spectrum. Single International Ultraviolet Explorer (IUE) spectra were secured for those stars exhibiting the greatest variety of structure in the optical interstellar lines, namely, HD 93130, 93160, 93162, 93204, 93205, 93206 and HDE 303308. Appraisal of the spectra suggests that: (1) longwards of Lyman Alpha many of the interstellar lines, including an unidentified one, in the spectrum of Zeta Oph seem to be present in the Carina Nebula spectra; (2) interstellar line structure varies widely in both velocity and intensity throughout the region, as well as along a given line of sight as the species change; (3) new high velocity components of UV lines appear to extend the total range of velocities in the nebular interstellar lines to about 400 m/s; and (4) lines of the high excitation species Si IV and C IV are strong and also structured in velocity space.

Hesser, J. E.↗
NASA NTRS1987

Analysis and interpretation of satellite fragmentation data

The velocity perturbations of the fragments of a satellite can shed valuable information regarding the nature and intensity of the fragmentation. A feasibility study on calculating the velocity perturbations from existing equations was carried out by analyzing 23 major documented fragmentation events. It was found that whereas the calculated values of the radial components of the velocity change were often unusually high, those in the two other orthogonal directions were mostly reasonable. Since the uncertainties in the radial component necessarily translate into uncertainties in the total velocity change, it is suggested that alternative expressions for the radial component of velocity be sought for the purpose of determining the cause of the fragmentation from the total velocity change. The calculated variances in the velocity perturbations in the two directions orthogonal to the radial vector indicate that they have the smallest values for collision induced breakups and the largest values for low-intensity explosion induced breakups. The corresponding variances for high-intensity explosion induced breakups generally have values intermediate between those of the two extreme categories. A three-dimensional plot of the variances in the two orthogonal velocity perturbations and the plane change angle shows a clear separation between the three major types of breakups. This information is used to reclassify a number of satellite fragmentation events of unknown category.

Tan, Arjun↗
NASA NTRS1973

Observation and analysis of abrupt changes in the interplanetary plasma velocity and magnetic field.

This paper presents a limited study of the physical nature of abrupt changes in the interplanetary plasma velocity and magnetic field based on 19 day's data from the Pioneer 6 spacecraft. The period was chosen to include a high-velocity solar wind stream and low-velocity wind. Abrupt events were accepted for study if the sum of the energy density in the magnetic field and velocity changes was above a specified minimum. A statistical analysis of the events in the high-velocity solar wind stream shows that Alfvenic changes predominate. This conclusion is independent of whether steady state requirements are imposed on conditions before and after the event. Alfvenic changes do not dominate in the lower-speed wind. This study extends the plasma field evidence for outwardly propagating Alfvenic changes to time scales as small as 1 min (scale lengths on the order of 20,000 km).

Martin, R. N.↗
NASA NTRSDate not supplied

Comparison of Active and Passive Head Impulse Testing of the Horizontal Vestibulo-Ocular Reflex: Exploring the Feasibility of Different Approaches for Spaceflight

INTRODUCTION: Astronauts experience a wide variety of sensorimotor disturbances primarily due to microgravity-induced vestibular adaptations during spaceflight. Head Impulse Testing (HIT) will be conducted during the Complement of Integrated Protocols for Human Exploration Research program(CIPHER) Vestibular Health study to examine changes in the horizontal vestibulo-ocular reflex in response to high-velocity head movements to detect changes in peripheral vestibular function [1,2]. However, correct interpretation will require consideration of potential artifacts and the constraints of conducting this test across different phases of the mission. Therefore, the aims of our study were to (1) examine reliability across different test operators, and (2) compare results of active (aHIT) versus passive (pHIT) approaches to evaluate the feasibility of self-administered versus operator-assisted approaches. A comparison of responses with visual viewing of a wall target (default condition) versus vision occluded evaluated the influence of other oculomotor control influence across conditions, and comparison with computer-generated rotator head impulse tests (rHIT) examined the variability associated with the ocular responses independent of the variability in executing the head movements themselves. METHODS: Seventeen non-astronaut volunteers (male n=12, age=22.9 ± 3.0; female n=5, age=27.0 ± 6.0, mean ± std) completed HIT testing using video-oculography (VOG) goggles and a high-torque rotator system. The test order was counterbalanced across conditions: (1) passive head-on-torso (pHIT, default condition for flight study) using two operators (Op1 and Op2), (2) active head-on-torso (aHIT, subject initiated), and (3) passive head and torso using rotary chair (rHIT). Eye and head movement data were processed to obtain gain in each direction. The main outcome measures were average gain and asymmetry [1], as well as the percentage of acceptable trials not excluded due to insufficient head amplitude or recording artifacts. RESULTS: While the pHIT gains were similar with vision (1.032 ± 0.043) and vision occluded (1.029 ± 0.038) conditions, the percentage of acceptable trials was greater with vision (Op1 = 93.0%, Op2 = 93.2%) versus occluded (Op1 = 70.7%, Op2 = 67.6%). The reliability between operators was greater for pHIT gain (Intraclass Correlation, ICC = 0.66, p = 0.001) than for pHIT asymmetry (ICC = 0.57, p = 0.01). The percentage of acceptable trials reduced by ~20% during the self-administered aHITs for both visual conditions and tended to be lower than computer-generated rHITs (76% versus 83%). While the aHIT gains were not significantly different than pHIT gains for vision or vision occluded conditions, these measures were poorly correlated. Both aHIT and pHIT gains were significantly greater than the rHIT gains, presumably due to the reduced velocities from the rotator. The asymmetry measures were poorly correlated across pHIT, aHIT, and rHIT conditions, although none of the subjects had asymmetries greater than 16%. DISCUSSION: Our findings support the feasibility of using the standard pHIT methodology for spaceflight. Similarities between visual conditions reflect that these responses are mediated by the peripheral lateral canals rather than other oculomotor mechanisms. The inter-tester reliability was acceptable despite differences in the tester training. In addition to concerns of non-vestibular mechanisms introduced during self-administered aHITs [2], operator-assisted pHITs resulted in higher percentage of acceptable trials and should result in more efficient and reliable measures during spaceflight.

M R Ehrenburg↗
NASA NTRS1990

MHD shocks in the ISM

Researchers survey shock solutions of a partially ionized gas with a magnetic field. The gas is modeled by interacting neutral, ion, electron and charged grain components. They employ a small neutral-ion chemical network to follow the dissociation and ionization of the major species. Cooling by molecular hydrogen (rotational, vibrational and dissociation), grains and dipole molecules is included. There are three basic types of solutions (C, C asterisk, and J) and some more complicated flows involving combinations of the basic types. The initial preshock conditions cover hydrogen nuclei densities of 1 less than n less than 10(exp 10) cm(-3) and shock velocities of 5 less than v(sub s) less than 60 km/s. The magnetic field is varied over 5 decades and the sensitivity of the results to grain parameters, UV and cosmic ray fluxes is ascertained. The parameter space is quite complicated, but there exist some simple divisions. When the initial ionization fraction is small (chi sub i less than 10(-5)), there is a sharp transition between fully C solutions at low velocity and strong J solutions at high velocity. When the initial ionization fraction is larger, C asterisk and/or very weak J shocks are present at low velocities in addition to the C solutions. The flow again changes to strong J shocks at high velocities. When the ionization fraction is large and the flow is only slightly greater than the bulk Alfven velocity, there is a complicated mixture of C, C asterisk and J solutions.

Chernoff, D. F.↗
NASA NTRS1987

Thermally induced phase changes, lateral heterogeneity of the mantle, continental roots, and deep slab anomalies

Factors which influence the lateral heterogeneity in density and seismic velocity with depth in the upper earth mantle are discussed. It is emphasized that most of the increases in density and seismic velocity with depth are caused by pressure-induced solid-solid phase changes in the high-density high-velocity phases of mineral assemblage, due to variations in temperature. In particular, the ilmenite form of MgSiO3 and the gamma-spinel form of Mg2SiO4 have broad stability fields in cold mantle and are not stable in hotter mantle. It is emphasized that the density and velocity anomalies associated with temperature-induced phase changes in mineral assemblage must be taken into account in the thermal models of the slabs; when these effects are accounted for, the geoid and seismic anomalies associated with subducted slabs are consistent with slab confinement to the upper mantle and with layered models of mantle convection.

Anderson, Don L.↗
NASA NTRS1988

Pressure measuring probe

The invention is a prove (10) for measuring changes in pressure in a high velocity fluid streams over and adjacent the surface of an object. The probe (10) is formed of an exterior housing (11) having a closed pressure chamber (28) in which a piezo-electric pressure transducer (32) is mounted. an open connector tube (26) having a probe tip (29) passes a portion of said fluid stream into the closed pressure chamber (28), any change of pressure therein requiring a "settling-time" to appear in the closed pressure chamber (28) that is inversely proportional to the cross-sectional area of the connector tube (26). A cooling chamber (47) formed around the pressure chamber (28) is connected to a source of cooling fluid by means of inlet and outlet tubes (44) and (46), respectively.

George C Ashby, Jr↗
NASA NTRS1984

Fluid shielding of high-velocity jet noise

Experimental noise data for a nozzle exhaust system incorporating a thermal acoustic shield (TAS) are presented to show the effect of changes in geometric and flow parameters on attenuation of high-velocity jet exhaust noise in the flyover plane. The results are presented for a 10.00-cm-diameter primary conical nozzle with a TAS configuration consisting of a 2.59- or 5.07-cm-wide annular gap. Shield-stream exhaust velocity was varied from 157 to 248 m/sec to investigate the effect of velocity ratio. The results showed that increasing the annular gap width increases attenuation of high-frequency noise when comparisons are made on the same ideal thrust basis. Varying the velocity ratio had a minor effect on the noise characteristics of the nozzles investigated.

Goodykoontz, J. H.↗
NASA NTRS1982

LOX/hydrocarbon auxiliary propulsion system study

Liquid oxygen (LOX)/hydrocarbon propulsion concepts for a "second generation' orbiter auxiliary propulsion system was evaluated. The most attractive fuel and system design approach identified, and the technology advancements that are needed to provide high confidence for a subsequent system development were determined. The fuel candidates were ethanol, methane, propane, and ammonia. Even though ammonia is not a hydrocarbon, it was included for evaluation because it is clean burning and has a good technology base. The major system design options were pump versus pressure feed, cryogenic versus ambient temperature RCS propellant feed, and the degree of OMS-RCS integration. Ethanol was determined to be the best fuel candidate. It is an earth-storable fuel with a vapor pressure slightly higher than monomethyl hydrazine. A pump-fed OMS was recommended because of its high specific impulse, enabling greater velocity change and greater payload capability than a pressure fed system.

Orton, G. F.↗
NASA NTRS2003

Laboratory Simulation of Space Weathering: ESR Measurements of Nanophase Metallic Iron in Laser-irradiated Olivine and Pyroxene Samples

S-type asteroids are believed to be parent bodies of ordinary chondrites. Although both S-type asteroids and ordinary chondrites contain the same mineral assemblage, mainly olivine and pyroxene, the reflectance spectra of the asteroids exhibit more overall depletion (darkening) and reddening, and more weakening of absorption bands relative to the meteorites. This spectral mismatch is explained by space weathering process, where high-velocity dust particle impacts should change the optical properties of the uppermost regolith surface of asteroids. In order to simulate the space weathering, we irradiated nanosecond pulse laser beam onto pellet samples of olivine (8.97wt% FeO) and pyroxene (enstatite: 9.88wt% FeO, hypersthene: 16.70wt%). We got spectral changes in our samples similar to that by space weathering on asteroids and confirmed nanophase alpha-metallic iron particles, which were theoretically predicted, not only on olivine but also on pyroxene samples by Transmission Electron Microscopy (TEM). Nanophase metallic iron particles were widely scattered throughout the amorphous rims developed along the olivine grains, whereas they were embedded in aggregates of amorphous in enstatite samples. Recently, we also measured laser-irradiated samples by ESR (Electron Spin Resonance). Strong ESR signals, characteristic to nanophase iron particles, are observed on irradiated olivine samples. In this paper, we report the quantities of nanophase metallic iron particles in pyroxene samples by ESR observations in addition to olivine samples.

Kurahashi, E.↗
NASA NTRS2022

Eta Carinae: An Evolving View of the Central Binary, Its Interacting Winds and Its Foreground Ejecta

FUV spectra of η Car, recorded across two decades with HST/STIS, document multiple changes in resonant lines caused by dissipating extinction in our line of sight. The FUV flux has increased nearly tenfold, which has led to increased ionization of the multiple shells within the Homunculus and photodestruction of H 2 . Comparison of observed resonant line profiles with CMFGEN model profiles allows separation of wind–wind collision and shell absorptions from the primary wind P Cygni profiles. The dissipating occulter preferentially obscured the central binary and interacting winds relative to the very extended primary wind. We are now able to monitor changes in the colliding winds with orbital phase. High-velocity transient absorptions occurred across the most recent periastron passage, indicating acceleration of the primary wind by the secondary wind, which leads to a downstream, high-velocity bow shock that is newly generated every orbital period. There is no evidence of changes in the properties of the binary winds.

Massive stars↗
NASA NTRS1973

On the relation between solar wind structure and solar wind rotational and tangential discontinuities.

Solar wind plasma and magnetic field data were used to identify rotational and tangential discontinuities during the first 40 days of the flight of Mariner 5. Of the 40 rotational discontinuities found, 36 were clustered in three distinct 3- to 6-day intervals. These three intervals were characterized by high solar wind bulk velocities, high magnetic field magnitudes, low densities, high correlation between velocity and magnetic field changes, and the presence of smooth Alfven waves. The rotational discontinuities had magnetic field changes that were generally close to the direction of magnetic field changes for smooth Alfven waves. Although the primary component of these changes was perpendicular to the equatorial plane for both, the radial component for the discontinuities was generally larger. The normals to the tangential discontinuity surfaces strongly preferred a direction near the ecliptic plane and perpendicular to the spiral field direction.

Turner, J. M.↗