SEARCH · Engineering Papers
Results for “INTERSTELLAR SPACE”
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.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
System Engineering a Solar Thermal Propulsion Mission Concept for Rapid Interstellar Medium Access
The interstellar medium (ISM) represents the next frontier in space exploration, with many new discoveries to be made. The challenge, being so far away from Earth, the ISM requires many decades to reach. To advance our knowledge of what exists beyond our Solar System, new approaches for rapid access are required. One such approach is solar thermal propulsion (STP). The approach uses several Venus and Earth gravity assists to fly to Jupiter and use its gravity well to dive towards the Sun. Approaching within 3 solar radii a perihelion burn would be performed, maximizing the spacecraft’s ΔV to achieve high Solar System escape velocities. A unique aspect of the STP mission concept is that the Sun is not only used as a gravity well for an Oberth manoeuvre, but also to heat the fuel to ultra-high-temperatures (>3000 K), enabling a monopropellant burn with high specific impulse (Isp). Prior preliminary studies indicated escape velocities of over 20 astronomical unit (AU)/yr would be possible. An in-depth modelling exercise was undertaken to determine how such a system would perform. The model in this paper showed the current STP design is capable of providing just under 9±1 AU/yr, but there are many technology developments that could increase escape velocity. The technologies vary from items that could be implemented in the near term, like turbo-pumps driven by the hydrogen, to items requiring more extensive development programs like thin coatings which do not erode in superheated hydrogen. After reviewing the STP approach, and comparing it to a solid rocket motor (SRM), it was found that with currently available technology, SRM outperforms STP with an escape velocity of approximately 10-12 AU/yr. However, future advances in heat exchanger lining materials, turbo pumps, and advanced heat exchanger geometries may enable solar thermal propulsion to provide higher escape velocities, providing one of the fastest ways to exit the solar system. Ultimately, if all technology paths could be implemented with minimal side effects, the performance in a best-case scenario could reach up to 16 AU/yr.
Space Nuclear Propulsion for Deep Space Science Missions
The use of nuclear thermal propulsion (NTP) 1 and nuclear electric propulsion (NEP) 2 systems on deep space science missions to the outer planets and into the interstellar medium 3 can yield significant spacecraft system and mission performance benefits and improvements relative to the use of conventional chemical propulsion systems. Several recent and ongoing programs are developing the technologies and systems required to realize a near-term deep space nuclear propulsion capability. NTP provides improved propulsion efficiencies compared to chemical propulsion, while also providing substantial thrust. This combination of high thrust and increased specific impulse (I_sp) provides high acceleration and extended thrusting periods, enabling greatly reduced trip-times on certain types of missions compared to various propulsive alternatives. For examples, compared to a baseline mission using chemical propulsion, NTP-powered missions to Jupiter or Uranus could deliver approximately 2.4-3.6 times more payload (in the case of Jupiter, the payload delivery is significantly larger than the Juno spacecraft). In this comparison, the higher end of the payload advantage is obtained when the trip time is held equal for the NTP-powered vehicle and a vehicle using a chemical propulsion departure stage. NTP systems are presently under development by multiple government agencies. NASA’s Space Nuclear Propulsion (SNP) project aims to demonstrate a hydrogen-fed NTP engine at 900 s specific impulse (I_sp) and approximately 10-15 klb_f of thrust. DARPA’s Demonstration Rocket for Agile Cislunar Operations (DRACO) program is targeting a demonstration of an NTP system in the cislunar space between the Earth and the Moon. An appropriately phased development plan that applies the development of the reactor technology for an NTP engine in this performance class and leverages mature, existing liquid rocket component hardware provides a path to a lower cost propulsion system that can be realized on a shorter development schedule. NEP, with high Isp in the 2,000-8,000 s range, can also provide advantages over chemical propulsion, including a much greater payload delivery mass and the flexibility for planners to trade between delivered mass and a wider window of mission trajectory options. Electric propulsion (EP) systems have demonstrated great utility, performing notably on the Dawn mission to enable rendezvous and orbital insertion at two separate bodies, Vesta and Ceres. An NEP-powered vehicle would have a similar capability to visit multiple bodies, loitering at each before moving to the next. A 10 kW_e NEP system provides a power- rich environment on the spacecraft that is simply not possible using present radioisotope power systems, giving mission planners more scientific instrument and communication hardware options. Several programs and projects are presently developing NEP systems and subsystems in the 10 kW_e power range, leveraging past reactor work and recent nuclear power generation risk-reduction demonstration activities such as the Demonstration Using Flattop Fission (DUFF) and the Kilopower Reactor Using Stirling TechnologY (KRUSTY). The goal of the Air Force Research Laboratory’s Joint Energy Technology Supplying On-Orbit Nuclear Power (JETSON) program is an in-space demonstration vehicle that has a 10 kW_e -class fission power source. These past and present efforts can be combined with the ongoing development of 10 kW_e -class electric propulsion systems (notably the NEXT-C ion thruster or the Hall-effect thrusters for Power and Propulsion Element of the Lunar Gateway) to provide a pathway to a low-cost, reliable NEP system for deep space science application.
Space Nuclear Propulsion for Deep Space Science Missions
The use of nuclear thermal propulsion (NTP) 1 and nuclear electric propulsion (NEP) 2 systems on deep space science missions to the outer planets and into the interstellar medium 3 can yield significant spacecraft system and mission performance benefits and improvements relative to the use of conventional chemical propulsion systems. Several recent and ongoing programs are developing the technologies and systems required to realize a near-term deep space nuclear propulsion capability. NTP provides improved propulsion efficiencies compared to chemical propulsion, while also providing substantial thrust. This combination of high thrust and increased specific impulse (I_sp) provides high acceleration and extended thrusting periods, enabling greatly reduced trip-times on certain types of missions compared to various propulsive alternatives. For examples, compared to a baseline mission using chemical propulsion, NTP-powered missions to Jupiter or Uranus could deliver approximately 2.4-3.6 times more payload (in the case of Jupiter, the payload delivery is significantly larger than the Juno spacecraft). In this comparison, the higher end of the payload advantage is obtained when the trip time is held equal for the NTP-powered vehicle and a vehicle using a chemical propulsion departure stage. NTP systems are presently under development by multiple government agencies. NASA’s Space Nuclear Propulsion (SNP) project aims to demonstrate a hydrogen-fed NTP engine at 900 s specific impulse (I_sp) and approximately 10-15 klb_f of thrust. DARPA’s Demonstration Rocket for Agile Cislunar Operations (DRACO) program is targeting a demonstration of an NTP system in the cislunar space between the Earth and the Moon. An appropriately phased development plan that applies the development of the reactor technology for an NTP engine in this performance class and leverages mature, existing liquid rocket component hardware provides a path to a lower cost propulsion system that can be realized on a shorter development schedule. NEP, with high Isp in the 2,000-8,000 s range, can also provide advantages over chemical propulsion, including a much greater payload delivery mass and the flexibility for planners to trade between delivered mass and a wider window of mission trajectory options. Electric propulsion (EP) systems have demonstrated great utility, performing notably on the Dawn mission to enable rendezvous and orbital insertion at two separate bodies, Vesta and Ceres. An NEP-powered vehicle would have a similar capability to visit multiple bodies, loitering at each before moving to the next. A 10 kW_e NEP system provides a power- rich environment on the spacecraft that is simply not possible using present radioisotope power systems, giving mission planners more scientific instrument and communication hardware options. Several programs and projects are presently developing NEP systems and subsystems in the 10 kW_e power range, leveraging past reactor work and recent nuclear power generation risk-reduction demonstration activities such as the Demonstration Using Flattop Fission (DUFF) and the Kilopower Reactor Using Stirling TechnologY (KRUSTY). The goal of the Air Force Research Laboratory’s Joint Energy Technology Supplying On-Orbit Nuclear Power (JETSON) program is an in-space demonstration vehicle that has a 10 kW_e -class fission power source. These past and present efforts can be combined with the ongoing development of 10 kW_e -class electric propulsion systems (notably the NEXT-C ion thruster or the Hall-effect thrusters for Power and Propulsion Element of the Lunar Gateway) to provide a pathway to a low-cost, reliable NEP system for deep space science application.
Collisionless Relaxation of the Ion Ring Distribution in Space Plasma
Energetic processes often produce transversely-heated angular distributions of the magnetized core (lowest energy) plasma. This characteristic is found in solar wind ion pickup, resulting from cometary or interstellar gas ionization, in Earths' ionosphere, and with hot ions formed around the Space Transportation System during gas releases. We investigate the thermalization of O+ ion pickup using the 2.5D hybrid simulation method (with fluid electrons and kinetic ions) of the ion pickup (ring) distributions, formed in the auroral ionosphere, with a range of ring velocities and thermal to magnetic pressure ratios. We find that in the unstable collisonless regime the anisotropy of the non-thermal distribution produces the ion-cyclotron instability, and the nonlinear relaxation is accompanied by wave-particle scattering that results in an emitted power of EMIC waves. We conclude that ionospheric pickup thermalization is slow due to the small ring speed compared to the thermal and Alfven speeds, while in the solar wind and other space plasmas regions with larger ion-ring velocity the collisionless relaxation and thermalization is rapid in terms of O+ ion gyro-period.
Heliophysics: The New Science of the Sun-Solar System Connection. Recommended Roadmap for Science and Technology 2005-2035
This is a Roadmap to understanding the environment of our Earth, from its life-sustaining Sun out past the frontiers of the solar system. A collection of spacecraft now patrols this space, revealing not a placid star and isolated planets, but an immense, dynamic, interconnected system within which our home planet is embedded and through which space explorers must journey. These spacecraft already form a great observatory with which the Heliophysics program can study the Sun, the heliosphere, the Earth, and other planetary environments as elements of a system--one that contains dynamic space weather and evolves in response to solar, planetary, and interstellar variability. NASA continually evolves the Heliophysics Great Observatory by adding new missions and instruments in order to answer the challenging questions confronting us now and in the future as humans explore the solar system. The three heliophysics science objectives: opening the frontier to space environment prediction; understanding the nature of our home in space, and safeguarding the journey of exploration, require sustained research programs that depend on combining new data, theory, analysis, simulation, and modeling. Our program pursues a deeper understanding of the fundamental physical processes that underlie the exotic phenomena of space.
C{sub 60} in photodissociation regions
Recent studies have confirmed the presence of buckminsterfullerene (C{sub 60}) in different interstellar and circumstellar environments. However, several aspects regarding C{sub 60} in space are not yet well understood, such as the formation and excitation processes, and the connection between C{sub 60} and other carbonaceous compounds in the interstellar medium, in particular polycyclic aromatic hydrocarbons (PAHs). In this paper, we study several photodissociation regions (PDRs) where C{sub 60} and PAHs are detected and the local physical conditions are reasonably well constrained to provide observational insights into these questions. C{sub 60} is found to emit in PDRs where the dust is cool (T{sub d} = 20-40 K) and even in PDRs with cool stars. These results exclude the possibility for C{sub 60} to be locked in grains at thermal equilibrium in these environments. We observe that PAH and C{sub 60} emission are spatially uncorrelated and that C{sub 60} is present in PDRs where the physical conditions (in terms of radiation field and hydrogen density) allow for full dehydrogenation of PAHs, with the exception of Ced 201. We also find trends indicative of an increase in C{sub 60} abundance within individual PDRs, but these trends are not universal. These results support models where the dehydrogenation of carbonaceous species is the first step toward C{sub 60} formation. However, this is not the only parameter involved and C{sub 60} formation is likely affected by shocks and PDR age.
G-star astropauses - A test for interstellar pressure
Under the assumption of a solar system model, astropause radii are estimated for a sample of 70 G stars near the sun. G-star space velocities and trajectories are calculated. Three stars within 10 pc of the sun have predicted astropause radii larger than 6 arcsec. At least eight stars have traversed low interstellar pressure regions, similar to the path of the sun, over the last 4 Myr. The Galactic influences on these stellar systems thus may be similar to those on the solar system, providing a list of possibly attractive SETI targets. The closest star to the sun 4 Myr ago, in this restricted sample, was HD 147513. The relative dimensions of the astropause radii of G stars with space motions parallel and perpendicular to the surrounding interstellar magnetic field may vary by a factor of 2 and may ultimately yield quantitative estimates of interstellar magnetic field strength near the sun.
CIRCUM-GALACTIC GAS AND THE ISOTROPIC GAMMA-RAY BACKGROUND
Interactions of cosmic rays with the interstellar medium in the disk of the Milky Way provide the majority of the diffuse gamma-ray emission observed by the Fermi Gamma-ray Space Telescope. In addition to the gas which is densely concentrated along the galactic plane, hydrodynamical simulations and observational evidence favor the presence of a halo of hot (T {approx} 10{sup 6} K) ionized hydrogen (H II), extending with non-negligible densities out to the virial radius of the Milky Way. We show that cosmic-ray collisions with this circum-galactic gas should be expected to provide on the order of 3%-10% of the observed isotopic gamma-ray background at energies above 1 GeV. In addition, gamma rays originating from the extended H II halos of other galaxies along a given line of sight should contribute at a similar level.
Atomic Physics with the Goddard High Resolution Spectrograph on the Hubble Space Telescope: Oscillator Strengths for Neutral Carbon - III
High quality spectra of interstellar absorption from C I toward beta(sup 1) S(sub co), rho O(sub ph) A, and chi O(sub ph) were obtained with the Goddard High Resolution Spectrograph on HST. Many weak lines were detected within the observed wavelength intervals: 1150-1200 A for beta(sup 1) S(sub co) and 1250-1290 A for rho O(sub ph) A and chi O(sub ph). Curve-of-growth analyses were performed in order to extract accurate column densities and Doppler parameters from lines with precise laboratory-based f-values. These column densities and b-values were used to obtain a self-consistent set of f-values for all the observed C I lines. A particularly important constraint was the need to reproduce data for more than one line of sight. For about 50% of the lines, the derived f-values differ appreciably from the values quoted by Morton.
Propulsion Technology Assessment: Science and Enabling Technologies to Explore the Interstellar Medium
The Advanced Concepts Office at NASA’s George C. Marshall Space Flight Center conducted a study to assess what low-thrust advanced propulsion system candidates, existing and near term, could deliver a small, Voyager-like satellite to our solar system’s heliopause, approximately 100 AU from the sun, within 10 years. The advanced propulsion system trade study consisted of three candidates, including a Magnetically Shielded Miniature Hall thruster, a solar sail and an electric sail. A second analysis was conducted to determine which solid rocket motor kick stage(s) would be required to provide additional thrust at various points in the trajectory, assuming a characteristic energy capability provided by a Space Launch System Block 1B vehicle architecture carrying an 8.4 meter payload fairing. Two trajectory profiles were considered, including an escape trajectory using a Jupiter gravity assist and an escape trajectory first performing a Jupiter gravity assist followed by an Oberth maneuver around the sun and an optional Saturn gravity assist. Results indicated that if the Technology Readiness Level of an electric sail could be increased in time, this technology could not only enable a satellite to reach 100 AU in 10 years but it could potentially do so in even less time.
An HST study of galactic inerstellar zinc and chromium
We present a survey of interstellar Zn II and Cr II absorption extracted from the Hubble Space Telescope Goddard High Resolution Spectrograph (HST GHRS) data archive. We find clear evidence for an enhanced depletion of Zn from the gas phase with increasing fractional abundance of molecular hydrogen f(H2). Our lower limit to the Galactic interstellar metallicity is approximately 65% of the solar value as determined by the measured Zn abundances in the lowest f(H2) sightlines, (N(Zn)/N(H(sup 0)(sub tot)) = -0.19 +/- 0.04. The correspondingly high depletion of Cr with respect to solar (N(Cr/N(H(sup 0)(sub tot)) = -1.44 +/- 0.26 indicates that there are significant amounts of dust present in these lines of sight. The Galactic abundances of Zn and Cr in the ISM provide a fundamental reference point which is used to understand the metal enrichment and dust formation history of damped Lyman alpha QSO absorption-line systems, normally believed to arise from intervening precursors to modern disk galaxies. Although the spread in Zn abundances is large for both the local ISM and in damped Lyman alpha systems, we still find a substantial difference (factor of 4-10) in metallicity between the two sets. This survey and future observations of more distant objects which probe the full extent of the Milky Way halo provide a more complete picture of the enrichment and depletion characteristics of present-day galaxies.
THE HELIOTAIL
The heliotail is formed when the solar wind (SW) interacts with the local interstellar medium (LISM) and is shaped by the interstellar magnetic field (ISMF). While there are no spacecraft available to perform in situ measurements of the SW plasma and heliospheric magnetic field (HMF) in the heliotail, it is of importance for the interpretation of measurements of energetic neutral atom fluxes performed by Interstellar Boundary Explorer. It has been shown recently that the orientation of the heliotail in space and distortions of the unperturbed LISM caused by its presence may explain the anisotropy in the TeV cosmic ray flux detected in air shower observations. The SW flow in the heliotail is a mystery itself because it is strongly affected by charge exchange between the SW ions and interstellar neutral atoms. If the angle between the Sun’s magnetic and rotation axes is constant, the SW in the tail tends to be concentrated inside the HMF spirals deflected tailward. However, the twisted field soon becomes unstable and the reason for the SW collimation within a two-lobe structure vanishes. We demonstrate that kinetic treatment of the H atom transport becomes essential in this case for explaining the lobe absence further along the tail. We show that the heliotail flow is strongly affected by the solar cycle that eliminates artifacts, which is typical of solutions based on simplifying assumptions. The heliopause in the tail is subject to Kelvin–Helmholtz instability, while its orientation and shape are determined by the ISMF direction and strength.
AN ECHO OF SUPERNOVA 2008bk
I have discovered a prominent light echo around the low-luminosity Type II-plateau supernova (SN) 2008bk in NGC 7793, seen in archival images obtained with the Wide Field Channel of the Advanced Camera for Surveys on board the Hubble Space Telescope (HST). The echo is a partial ring, brighter to the north and east than to the south and west. The analysis of the echo I present suggests that it is due to the SN light pulse scattered by a sheet, or sheets, of dust located Almost-Equal-To 15 pc from the SN. The composition of the dust is assumed to be of standard Galactic diffuse interstellar grains. The visual extinction of the dust responsible for the echo is A{sub V} Almost-Equal-To 0.05 mag in addition to the extinction due to the Galactic foreground toward the host galaxy. That the SN experienced much less overall extinction implies that it is seen through a less dense portion of the interstellar medium in its environment. The late-time HST photometry of SN 2008bk also clearly demonstrates that the progenitor star has vanished.
Aerogel Captures Cometary and Interstellar Samples via STARDUST
Aerogel is the primary payload on STARDUST, the fourth mission of the National Aeronautics and Space Administration Discovery program, to be launched in February 1999.
PSR B0329+54: STATISTICS OF SUBSTRUCTURE DISCOVERED WITHIN THE SCATTERING DISK ON RADIOASTRON BASELINES OF UP TO 235,000 km
We discovered fine-scale structure within the scattering disk of PSR B0329+54 in observations with the RadioAstron ground–space radio interferometer. Here we describe this phenomenon, characterize it with averages and correlation functions, and interpret it as the result of decorrelation of the impulse-response function of interstellar scattering between the widely separated antennas. This instrument included the 10 m Space Radio Telescope, the 110 m Green Bank Telescope, the 14 × 25 m Westerbork Synthesis Radio Telescope, and the 64 m Kalyazin Radio Telescope. The observations were performed at 324 MHz on baselines of up to 235,000 km in 2012 November and 2014 January. In the delay domain, on long baselines the interferometric visibility consists of many discrete spikes within a limited range of delays. On short baselines it consists of a sharp spike surrounded by lower spikes. The average envelope of correlations of the visibility function shows two exponential scales, with characteristic delays of τ{sub 1}=4.1±0.3 μs and τ{sub 2}=23±3 μs, indicating the presence of two scales of scattering in the interstellar medium. These two scales are present in the pulse-broadening function. The longer scale contains 0.38 times the scattered power of the shorter one. We suggest that the longer tail arises from highly scattered paths, possibly from anisotropic scattering or from substructure at large angles.
Paradigm transition in cosmic plasma physics
New discoveries in cosmic plasma physics are described, and their applications to solar, interstellar, galactic, and cosmological problems are discussed. The new discoveries include the existence of double layers in magnetized plasmas and in the low magnetosphere, and energy transfer by electric current in the auroral circuit. It is argued that solar flares and the solar wind-magnetosphere interaction should not be interpreted in terms of magnetic merging theories, and that electric current needs to be explicitly taken account of in understanding these phenomena. The filamentary structure of cosmic plasmas may be caused by electric currents in space, and the pinch effect may have a central role to play in the evolutionary history of interstellar clouds, stars, and solar systems. Space may have a cellular structure, with the cell walls formed by thin electric current layers. Annihilation may be the source of energy for quasars and the Hubble expansion, and the big bang cosmology may well be wrong.