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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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All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Materials and technologies for interstellar flights and intra-galactic spread of life

Small automated spaceships are capable to deliver seeds, frozen ova and gametes to other planetary systems. A spaceship can be equipped with a freezer containing reproductive cells, an artificial uterus, a robotic nursery and school, and a collection of instruments and equipment. The whole spaceship will be frozen during a long interstellar flight. Approaching another star, a spaceship will generate electricity from light, warm up, slow down and land on a suitable planet (if any), give birth to a human, provide care and education. After schooling, the human will vacate the spaceship and either build more space for living (using local materials) or die. A vacant spaceship will supply more people, one at a time. Hopefully, they will collectively create a sustainable colony on a remote planet. Our Milky Way galaxy has hundreds billion stars (i.e., more stars than humans on Earth). Mass production of spacecrafts for intragalactic spread of life will make each spaceship cheaper, will improve employment and purposeful production on Earth, and will spread human life beyond the Solar System. If any spaceship will miss its target stellar system, it will fly to the next one, retaining ability to bring life to another planet. Which materials and technologies are needed for the interstellar life propagation? Materials age during a long interstellar flight, which can last from 10^4 to 10^10 years. We evaluate the computational methods (such as C2NEB, available from https://lib.dr.iastate.edu/ameslab_software/1) that are suitable for addressing materials aging at low temperatures and high radiation levels during the appropriately long-time scales.

Technologies↗
NASA NTRS1996

The Voyager Interstellar Mission

The Voyager Interstellar Mission began on January 1, 1990, with the primary objective being to characterize the interplanetary medium beyond Neptune and to search for the transition region between the interplanetary medium and the interstellar medium...This paper describes the Voyager Interstellar Mission - the mission objectives, the spacecraft and science payload, the mission operations strategy being used to maximize science data return even in the event of certain potential spacecraft subsystem failures.

Voyager↗
NASA NTRS1994

Electron Density Power Spectrum in the Local Interstellar Medium

Interstellar scintillation (ISS), fluctuations in the amplitude and phase of radio waves caused by scattering in the interstellar medium, is important as a diagnostic of interstellar plasma turbulence. ISS is also of interest because it is noise for other radio astronomical observations.

interstellar↗
NASA NTRS2024

Interstellar Propulsion

As you read this, humanity’s first interstellar probe has left our solar system and is moving at nearly 17 km/s on its journey through interstellar space. Launched in 1977 and carrying a message from Earth on an inscribed golden disk, Voyager 1 completed its grand tour of the outer planets and has since travelled more than 24 billion km on its outward journey; it’s twin probe, Voyager 2, has also left the heliopause and entered interstellar space, traveling over 20 billion km from Earth. Yet even at these speeds and distances, our intrepid Voyagers have barely moved beyond the influence of our local star. If the distance between our Sun and the closest neighboring star system, Alpha Centauri, were scaled to the size of a meter stick, Voyager 1 would be located just over the ½-mm mark, having traveled 0.06% of the way to the next star (assuming it was pointed in the right direction, which it isn’t). At this rate it will take the probe nearly 75 thousand years to cover the equivalent distance to Alpha Centauri.

Interstellar↗
DOE OSTI2016

A study of interstellar aldehydes and enols as tracers of a cosmic ray-driven nonequilibrium synthesis of complex organic molecules

Significance Since the detection of the methylidyne radical (CH) in the interstellar medium nearly 80 y ago, about 200 molecules ranging from molecular hydrogen to fullerenes have been identified in interstellar and circumstellar environments, but the synthesis of complex organic molecules (COMs)––organics containing several atoms of carbon, hydrogen, nitrogen, and oxygen––has remained elusive to date. Here, we provide compelling evidence via laboratory experiments, computations, and modeling that the synthesis of COMs is driven by a cosmic-ray-triggered nonequilibrium chemistry within interstellar ices at temperatures as low as 10 K. These fundamental reaction mechanisms are of major significance to facilitate an understanding of the origin and evolution of the molecular universe.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

ON THE FORMATION AND ISOMER SPECIFIC DETECTION OF PROPENAL (C{sub 2}H{sub 3}CHO) AND CYCLOPROPANONE (c-C{sub 3}H{sub 4}O) IN INTERSTELLAR MODEL ICES—A COMBINED FTIR AND REFLECTRON TIME-OF-FLIGHT MASS SPECTROSCOPIC STUDY

The formation routes of two structural isomers—propenal (C{sub 2}H{sub 3}CHO) and cyclopropanone (c-C{sub 3}H{sub 4}O)—were investigated experimentally by exposing ices of astrophysical interest to energetic electrons at 5.5 K thus mimicking the interaction of ionizing radiation with interstellar ices in cold molecular clouds. The radiation-induced processing of these ices was monitored online and in situ via Fourier Transform Infrared spectroscopy and via temperature programmed desorption exploiting highly sensitive reflectron time-of-flight mass spectrometry coupled with single photon ionization in the post irradiation phase. To selectively probe which isomer(s) is/are formed, the photoionization experiments were conducted with 10.49 and 9.60 eV photons. Our studies provided compelling evidence on the formation of both isomers—propenal (C{sub 2}H{sub 3}CHO) and cyclopropanone (c-C{sub 3}H{sub 4}O)—in ethylene (C{sub 2}H{sub 4})—carbon monoxide (CO) ices forming propenal and cyclopropanone at a ratio of (4.5 ± 0.9):1. Based on the extracted reaction pathways, the cyclopropanone molecule can be classified as a tracer of a low temperature non-equilibrium chemistry within interstellar ices involving most likely excited triplet states, whereas propenal can be formed at ultralow temperatures, but also during the annealing phase via non-equilibrium as well as thermal chemistry (radical recombination). Since propenal has been detected in the interstellar medium and our laboratory experiments demonstrate that both isomers originated from identical precursor molecules our study predicts that the hitherto elusive second isomer—cyclopropanone—should also be observable toward those astronomical sources such as Sgr B2(N) in which propenal has been detected.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Polycyclic aromatic hydrocarbons in samples of Ryugu formed in the interstellar medium

Polycyclic aromatic hydrocarbons (PAHs) contain ≲20% of the carbon in the interstellar medium. They are potentially produced in circumstellar environments (at temperatures ≳1000 kelvin), by (~10 kelvin) interstellar clouds, or by processing of carbon-rich dust grains. We report isotopic properties of PAHs extracted from samples of the asteroid Ryugu and the meteorite Murchison. The doubly- 13 C substituted compositions (Δ2× 13 C values) of the PAHs naphthalene, fluoranthene, and pyrene are 9 to 51‰ higher than values expected for a stochastic distribution of isotopes. The Δ2× 13 C values are higher than expected if the PAHs formed in a circumstellar environment, but consistent with formation in the interstellar medium. By contrast, the PAHs phenanthrene and anthracene in Ryugu samples have Δ2× 13 C values consistent with formation by higher-temperature reactions.

Science & Technology - Other Topics↗
DOE OSTI2021

Toward Discovering the Structure and Dynamics of the Sun-Interstellar Medium System (Los Alamos LDRD Report)

We have taken major steps toward developing the tools necessary to explore with unprecedented resolution the plasma structure and dynamics of the Sun-interstellar medium (ISM) interaction region, known as the heliosheath. We have applied a rigorous imaging technique known as Generalized Ridge Regression (GRR) to construct statistically robust sky maps of hydrogen energetic neutral atoms (ENAs) emanating from this region and detected by the Los Alamos-led IBEX-Hi ENA imager [1] on NASA’s Interstellar Boundary Explorer (IBEX) mission [2]. Our methods go far beyond the map reconstruction process currently applied by the IBEX Science Operations Center (ISOC), opening up the possibility of new discovery science with the IBEX data set and positioning LANL for a lead science role for the upcoming Interstellar Mapping and Acceleration Probe (IMAP) mission [3] for which LANL is providing two key experiments. We have successfully demonstrated that the new maps are higher resolution and are capable of revealing structures that are not presently resolveable in standard ISOC maps

58 GEOSCIENCES↗
DOE OSTI2021

Diffuse Bands 9577 and 9633: Relations to Other Interstellar Features

We study, for the first time, the relations of two strong diffuse bands (DIBs) at 9633 and 9577 Å, commonly attributed to C{sub 60}{sup +}, to other interstellar features seen in optical and UV spectra including H i, Ca i, Fe ii, Na i, Ti ii, CN, CH, CH{sup +}, and C{sub 2} and DIBs 5780, 5797, 6196, 6269, 6284, and 6614. We analyzed 62 lines of sight where the stellar contamination by Mg ii was corrected or found negligible for DIB 9633. Equivalent widths of DIB 9577 were measured in 62 lines of sight. Poor mutual correlation between the strengths of the above features and the major diffuse bands (5780 and 5797) as well as with other DIBs (with some exceptions) were revealed. The considered DIBs are also poorly correlated with the features of neutral hydrogen, molecular carbon, and those of simple interstellar radicals. Perhaps this phenomenon can be explained if the diffuse band 9577 is an unresolved blend of two or more interstellar features. There are indications that 9633 and 9577 diffuse bands are stronger in σ-type clouds, i.e., these features resemble the behavior of reasonably broad DIBs, which are strong in the lines of sight where the UV flux from the very hot nearby stars plays an important role.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

On the Detectability of the X-tilde {sup 2}A{sup ′′} HSS, HSO, and HOS Radicals in the Interstellar Medium

X-tilde {sup 2}A{sup ′′} HSS has yet to be observed in the gas phase in the interstellar medium (ISM). HSS has been observed in cometary material and in high abundance. However, its agglomeration to such bodies or dispersal from them has not been observed. Similarly, HSO and HOS have not been observed in the ISM, either, even though models support their formation from reactions of known sulfur monoxide and hydrogen molecules, among other pathways. Consequently, this work provides high-level, quantum chemical rovibrational spectroscopic constants and vibrational frequencies in order to assist in interstellar searches for these radical molecules. Furthermore, the HSO−HOS isomerization energy is determined to be 3.63 kcal mol{sup −1}, in line with previous work, and the dipole moment of HOS is 36% larger at 3.87 D than HSO, making the less stable isomer more rotationally intense. Finally, the S−S bond strength in HSS is shown to be relatively weak at 30% of the typical disulfide bond energy. Consequently, HSS may degrade into SH and sulfur atoms, making any ISM abundance of HSS likely fairly low, as recent interstellar surveys have observed.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

The Origin of Compressible Magnetic Turbulence in the Very Local Interstellar Medium

Voyager 1 observed compressible magnetic turbulence in the very local interstellar medium (VLISM). We show that inner heliosheath (IHS) fast- and slow-mode waves incident on the heliopause (HP) generate VLISM fast-mode waves only that propagate into the VLISM. We suggest that this is the origin of compressible turbulence in the VLISM. We show that fast- and slow-mode waves transmitted across a tangential discontinuity such as the HP are strongly refracted on crossing the HP and subsequently propagate at highly oblique angles to the VLISM magnetic field. Thus, fast-mode waves in the VLISM contribute primarily to the compressible and not the transverse components of the VLISM fluctuating magnetic field variance 〈δ B-hat {sup 2}〉 since 〈δ B-hat {sub fz}{sup 2}〉≠0 and 〈δ B-hat {sub fx,fy}{sup 2}〉≃0. If the fast- and slow-mode waves in the IHS exhibit a Kolmogorov-like k{sup −5/3} power spectral density, as appears to be observed by Voyager 1, then the corresponding transmitted spectral density in the VLISM forms an amplified k{sup −5/3} power law. Consequently, the HP “radiates” fast-mode fluctuations into the VLISM, and the heliosphere therefore mediates the character of turbulence in the VLISM. In particular, we predict the form of the VLISM magnetic turbulence power spectral density to be a superposition of the background pristine interstellar turbulence spectrum and the fast-mode spectrum generated by the interaction of fast- and slow-mode IHS waves with the HP, i.e., a power law with an enhanced feature or “bump” corresponding to the contribution by fast-mode turbulence radiated by the HP. We note the applicability of these results to the generation of compressible turbulence in the local interstellar medium surrounding the asterospheres of stars.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2019

All-sky Measurement of the Anisotropy of Cosmic Rays at 10 TeV and Mapping of the Local Interstellar Magnetic Field

© 2019. The American Astronomical Society. All rights reserved. We present the first full-sky analysis of the cosmic ray arrival direction distribution with data collected by the High-Altitude Water Cherenkov and IceCube observatories in the northern and southern hemispheres at the same median primary particle energy of 10 TeV. The combined sky map and angular power spectrum largely eliminate biases that result from partial sky coverage and present a key to probe into the propagation properties of TeV cosmic rays through our local interstellar medium and the interaction between the interstellar and heliospheric magnetic fields. From the map, we determine the horizontal dipole components of the anisotropy δ 0h = 9.16 ×10 -4 and δ 6h = 7.25 ×10 -4 (±0.04 × 10 -4 ). In addition, we infer the direction (229.°2 ± 3.°5 R.A., 11.°4 ± 3.°0 decl.) of the interstellar magnetic field from the boundary between large-scale excess and deficit regions from which we estimate the missing corresponding vertical dipole component of the large-scale anisotropy to be δ N ~ -3.97 +1.0-2.0 × 10 -4 .

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

Why Interstellar Ice Dust Grains Should Be Elongated

Models of interstellar dust alignment assume that dust grains are elongated, but none of these models explain why dust grains should be elongated. On the other hand, models of interstellar dust grain growth assume that dust grains are spherical and not elongated. We show that when dusty plasma effects and the dipole moment of water molecules are together taken into account, ice grains in interstellar space should be prolate ellipsoids and not spheres. Dusty plasma analysis shows that an ice grain is charged to a negative potential that has magnitude nearly equal to that of the electron temperature. Several different mechanisms causing deviation from sphericity are identified; these mechanisms involve the interaction of the dipole moment of water molecules with electric fields associated with ice grain charging. These mechanisms include the focusing of water molecule trajectories, the migration of water molecules in a quasi-liquid layer on the grain surface toward regions where the electric field is strongest, the enhancement of this migration by the bombardment of energetic protons that gain energy upon falling into the ice grain negative potential, and mutual repulsion by electric charges having the same sign. Furthermore, the aspect ratio is established shortly after the ice grain is formed, and then is maintained as the grain grows.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1972

Preliminary results on interstellar reddening as deduced from filter photometry

Filter photometry has been used to derive the interstellar reddening law from stars through the study of a single spectral type, B0. The deficiency in the far ultraviolet flux of a supergiant relative to a main sequence star is compared with the difference in the flux distribution due to a change of one spectral class. Individual interstellar reddening curves show the general feature reported by Stecher (1969) and by Bless and Savage (1970). There is a large amount of scatter in the far ultraviolet which may be partially due to a real difference in interstellar extinction and partially due to observational inaccuracy.

Laget, M.↗
NASA NTRS1972

Interstellar medium model

A model of the ionized part of the interstellar medium was developed, based on the low frequency observations by the Radio Astronomy Explorer Satellite with a background of nonthermal radiation. This nonthermal background radiation is caused by synchrotron emission from cosmic ray electrons, and at low frequencies this emission is heavily absorbed by free-free absorption from the residual thermal electrons in the interstellar medium. By an appropriate model, parameters relevant to both the thermal and nonthermal components of the interstellar medium are shown. The observations were taken with the 100 deg dipole antenna and separated into galactic and extragalactic components. This model was developed using only the separated galactic component.

Novaco, J. C.↗
NASA NTRS1972

The influence of the ionized medium on synchrotron emission in interstellar space.

The effect of the ionized gas on synchrotron emission in the interstellar medium is investigated. A detailed calculation of the synchrotron emissivity of cosmic electrons, assumed to have an isotropic pitch-angle distribution in a uniform magnetic field, is made as a function of frequency and observation angle with respect to the field. The results are presented both as a local emissivity and as an intensity, the latter obtained by neglecting free-free absorption in the interstellar medium and by assuming that the emissivity is constant along the line of sight. The comparison of these results with previous studies on the nature of the low-frequency turnover of the galactic nonthermal radio background reveals that, except if the component perpendicular to the line of sight of the interstellar magnetic field is small (less than 1 microgauss), or if the cosmic-ray electron spectrum is cut off at energies below a few hundred MeV, the suppression of synchrotron emission by the ambient electrons has in general a lesser effect than free-free absorption by these electrons, and that in some cases this suppression effect is almost entirely negligible.

Ramaty, R.↗
NASA NTRS1972

Interstellar circular polarization.

This paper shows that optical observations of circular polarization produced by aligned interstellar grains could yield valuable information about the grain material. The interstellar medium is known to be linearly dichroic from observations of interstellar linear polarization. Since the same aligned grains make the medium linearly birefringent, a small component of circular polarization can result from incident linearly polarized light if the position angle of the linear polarization does not coincide with either principal axis of the medium. Calculations demonstrate that the wavelength of the circular polarization is sensitive to the imaginary part of the complex refractive index of the grain material. This provides an opportunity of investigating whether the grains are characteristically dielectric or metallic.

Martin, P. G.↗
NASA NTRS1973

A study of cosmic-ray positron and electron spectra in interplanetary and interstellar space and the solar modulation of cosmic rays

The differential energy spectra of cosmic-ray positrons and negatrons with energies between approximately 11 and 1500 MeV was measured during the period 1968-1971 using a balloon-borne magnetic spectrometer. These measurements fill a gap in the previously existing data and permit the determination of the interstellar spectra of cosmic-ray positrons and electrons. Knowledge of these spectra provides a crucial tool for studies of the distribution and density of matter and magnetic fields in the interstellar medium and the origin and dynamics of energetic particles contained in the fields. The differential energy spectrum of interstellar electrons may be represented as a power-law, j alpha T to the -1.8 power for 100 MeV approximately T approximately 2 GeV, but must flatten considerably at lower energies. From the measured electron charge composition, it is concluded that the majority of cosmic-ray electrons with energies above approximately 10 MeV originate in primary sources.

Cummings, A. C.↗