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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS2017

How Hospitable are Space Weather Affected Habitable Zones? The Role of Ion Escape

Atmospheres of exoplanets in the habitable zones around active young G-K-M stars are subject to extreme X-ray and EUV (XUV) (Extreme Ultraviolet) fluxes from their host stars that can initiate atmospheric erosion. Atmospheric loss affects exoplanetary habitability in terms of surface water inventory, atmospheric pressure, the efficiency of greenhouse warming, and the dosage of the UV surface irradiation. Thermal escape models suggest that exoplanetary atmospheres around active K-M stars should undergo massive hydrogen escape, while heavier species including oxygen will accumulate forming an oxidizing atmosphere. Here, we show that non-thermal oxygen ion escape could be as important as thermal, hydrodynamic H escape in removing the constituents of water from exoplanetary atmospheres under supersolar XUV irradiation. Our models suggest that the atmospheres of a significant fraction of Earth-like exoplanets around M dwarfs and active K stars exposed to high XUV fluxes will incur a significant atmospheric loss rate of oxygen and nitrogen, which will make them uninhabitable within a few tens to hundreds million years, given a low replenishment rate from volcanism or cometary bombardment. Our non-thermal escape models have important implications for the habitability of the Proxima Centauri's terrestrial planet.

radiation mechanisms↗
NASA NTRS2020

Solar System Escape Trajectories Using Outer Planetary Gravity Assists

A broad search of outer planet gravity assist sequences reveals flyby conditions that are naturally amenable for solar system escape. The optimal flyby conditions depend on the arrival velocity at the final body and provide the maximum possible escape speed for purely ballistic sequences. Trajectories in the 2030-2060 time frame are categorized by their encounter year with an emphasis on solar system escape speed and direction. All resulting sequences require a Jupiter gravity assist, and a considerable increase in escape speed is found in trajectories that utilize an additional Saturn, Uranus, or Neptune flyby. However, these solutions are limited by their availability and range of right ascensions. All cataloged trajectories are able to escape the solar system at least 3 au/year, and the highest energy sequences are in excess of 5.5 au/year. The search space is then used to find outer planet gravity assist trajectories to Kuiper Belt Objects (KBOs), and several cases are optimized.

Lam, Try↗
NASA NTRS2023

The Variable Detection of Atmospheric Escape around the Young, Hot Neptune AU Mic b

Photoevaporation is a potential explanation for several features within exoplanet demographics. Atmospheric escape observed in young Neptune-sized exoplanets can provide insight into and characterize which mechanisms drive this evolution and at what times they dominate. AU Mic b is one such exoplanet, slightly larger than Neptune (4.19 R ⊕ ). It closely orbits a 23 Myr pre-main-sequence M dwarf with an orbital period of 8.46 days. We obtained two visits of AU Mic b at Lyα with Hubble Space Telescope (HST)/Space Telescope Imaging Spectrograph. One flare within the first HST visit is characterized and removed from our search for a planetary transit. We present a nondetection in our first visit, followed by the detection of escaping neutral hydrogen ahead of the planet in our second visit. The outflow absorbed ∼30% of the star’s Lyα blue wing 2.5 hr before the planet’s white-light transit. We estimate that the highest-velocity escaping material has a column density of 10 13.96 cm −2 and is moving 61.26 km s −1 away from the host star. AU Mic b’s large high-energy irradiation could photoionize its escaping neutral hydrogen in 44 minutes, rendering it temporarily unobservable. Our time-variable Lyα transit ahead of AU Mic b could also be explained by an intermediate stellar wind strength from AU Mic that shapes the escaping material into a leading tail. Future Lyα observations of this system will confirm and characterize the unique variable nature of its Lyα transit, which, combined with modeling, will tune the importance of stellar wind and photoionization.

Exoplanets↗
NASA NTRS2012

Centrifugally Stimulated Exospheric Ion Escape at Mercury

We investigate the transport of ions in the low-altitude magnetosphere magnetosphere of Mercury. We show that, because of small spatial scales, the centrifugal effect due to curvature of the E B drift paths can lead to significant particle energization in the parallel direction. We demonstrate that because of this effect, ions with initial speed smaller than the escape speed such as those produced via thermal desorption can overcome gravity and escape into the magnetosphere. The escape route of this low-energy exosphere originating material is largely controlled by the magnetospheric convection rate. This escape route spreads over a narrower range of altitudes when the convection rate increases. Bulk transport of low-energy planetary material thus occurs within a limited region of space once moderate magnetospheric convection is established. These results suggest that, via release of material otherwise gravitationally trapped, the E B related centrifugal acceleration is an important mechanism for the net supply of plasma to the magnetosphere of Mercury.

Mercury↗
DOE OSTI2025

Preemptive optimization of a clinical antibody for broad neutralization of SARS-CoV-2 variants and robustness against viral escape

Most previously authorized clinical antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have lost neutralizing activity to recent variants due to rapid viral evolution. To mitigate such escape, we preemptively enhance AZD3152, an antibody authorized for prophylaxis in immunocompromised individuals. Using deep mutational scanning (DMS) on the SARS-CoV-2 antigen, we identify AZD3152 vulnerabilities at antigen positions F456 and D420. Through two iterations of computational antibody design that integrates structure-based modeling, machine-learning, and experimental validation, we co-optimize AZD3152 against 24 contemporary and previous SARS-CoV-2 variants, as well as 20 potential future escape variants. Our top candidate, 3152-1142, restores full potency (100-fold improvement) against the more recently emerged XBB.1.5+F456L variant that escaped AZD3152, maintains potency against previous variants of concern, and shows no additional vulnerability as assessed by DMS. This preemptive mitigation demonstrates a generalizable approach for optimizing existing antibodies against potential future viral escape.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2025

Experiment of Sea Breeze Convection, Aerosols, Precipitation, and Environment (ESCAPE)

Convective clouds play an important role in Earth’s climate system and are a known source of extreme weather. Gaps in our understanding of convective vertical motions, microphysics, and precipitation across a full range of aerosol and meteorological regimes continue to limit our ability to predict the occurrence and intensity of these cloud systems. To improve predictability, the National Science Foundation (NSF) sponsored a large field experiment entitled “Experiment of Sea Breeze Convection, Aerosols, Precipitation, and Environment (ESCAPE).” ESCAPE took place between 30 May and 30 September 2022 in the vicinity of Houston, Texas, because this area frequently experiences isolated deep convection that interacts with the region’s mesoscale circulations and its range of aerosol conditions. ESCAPE focused on collecting observations of isolated deep convection through innovative sampling and developing novel analysis techniques. This included the deployment of two research aircraft, the National Research Council of Canada Convair-580 and the Stratton Park Engineering Company Learjet, which combined conducted 24 research flights from 30 May to 17 June. On the ground, three mobile X-band radars and one mobile Doppler lidar truck equipped with soundings were deployed from 30 May to 28 June. From 1 August to 30 September 2022, a dual-polarization C-band radar was deployed and operated using a novel, multisensor agile adaptive sampling strategy to track the entire life cycle of isolated convective clouds. Analysis of the ESCAPE observations has already yielded preliminary findings on how aerosols and environmental conditions impact the convective life cycle.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2025

Forecasting for ESCAPE: A Multi-Institution Hybrid Forecasting and Nowcasting Operation for Sea-Breeze Convection Supporting a Ground-Based and Airborne Field Campaign

The Experiment of Sea-Breeze Convection, Aerosols, Precipitation and Environment (ESCAPE) field project deployed two aircraft and ground-based assets in the vicinity of Houston, Texas, between 27 May and 2 July 2022, examining how meteorological conditions, dynamics, and aerosols control the initiation, early growth stage, and evolution of coastal convective clouds. To ensure that airborne- and ground-based assets were deployed appropriately, a forecasting and nowcasting team was formed. Daily forecasts guided real-time decision-making by assessing synoptic weather conditions, environmental aerosol, and a variety of atmospheric modeling data to assign a probability for meeting specific ESCAPE campaign objectives. During the research flights, a small team of forecasters provided “nowcasting” support by analyzing radar, satellite, and new model data in real time. The nowcasting team proved invaluable to the campaign operation, as sometimes changing environmental conditions affected, for example, the timing of convective initiation. In addition to the success of the forecasting and nowcasting teams, the ESCAPE campaign offered a unique “testbed” opportunity where in-person and virtual support both contributed to campaign objectives. The forecasting and nowcasting teams were each composed of new and experienced forecasters alike, where new forecasters were given invaluable experience that would otherwise be difficult to attain. Both teams received training on forecast models, map analysis, Hybrid Single-Particle Lagrangian Integrated Trajectory model (HYSPLIT), and thermodynamic sounding analysis before the beginning of the campaign. In this article, the ESCAPE forecasting and nowcasting teams reflect on these experiences, providing potentially useful advice for future field campaigns requiring forecasting and nowcasting support in a hybrid virtual/in-person framework.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2024

The Escape Velocity Profile of the Milky Way from Gaia DR3

Abstract The escape velocity profile of the Milky Way offers a crucial and independent measurement of its underlying mass distribution and dark matter (DM) properties. Using a sample of stars from the third data release of Gaia with 6D kinematics and strict quality cuts, we obtain an escape velocity profile of the Milky Way from 4 to 11 kpc in Galactocentric radius. To infer the escape velocity in radial bins, we model the tail of the stellar speed distribution with both traditional power-law models and a new functional form that we introduce. While power-law models tend to rely on extrapolation to high speeds, we find our new functional form gives the most faithful representation of the observed distribution. Using this for the escape velocity profile, we constrain the properties of the Milky Way’s DM halo modeled as a Navarro–Frenck–White profile. Combined with constraints from the circular velocity at the solar position, we obtain a concentration and mass of c 200 c DM = 13.9 − 4.3 + 6.2 and M 200 c DM = 0.55 − 0.14 + 0.15 × 10 12 M ⊙ . This corresponds to a total Milky Way mass of M 200 c = 0.64 − 0.14 + 0.15 × 10 12 M ⊙ , which is on the low end of the historic range of the galaxy’s mass, but in line with other recent estimates.

Astronomy & Astrophysics↗
NASA NTRS1973

Apollo experience report: Launch escape propulsion subsystem

The Apollo launch escape propulsion subsystem contained three solid rocket motors. The general design, development, and qualification of the solid-propellant pitch-control, tower-jettison, and launch-escape motors of the Apollo launch escape propulsion subsystem were completed during years 1961 to 1966. The launch escape system components are described in general terms, and the sequence of events through the ground-based test programs and flight-test programs is discussed. The initial ground rules established for this system were that it should use existing technology and designs as much as possible. The practicality of this decision is proved by the minimum number of problems that were encountered during the development and qualification program.

Townsend, N. A.↗
NASA NTRS1973

Behavioral regulation of gravity - Schedule effects under escape-avoidance procedures

Squirrel monkeys were restrained in a centrifuge capsule and trained to escape and avoid increases in artificial gravity. During escape-avoidance, lever responses reduced centrifugally simulated gravity or postponed scheduled increases. The effect of variation in the interval of postponement (equal to the duration of decrease produced by escape responses) was studied under a multiple schedule of four components. Three components were gravity escape-avoidance with postponement times of 20, 40, and 60 sec. The fourth component was extinction. Each component was associated with a different auditory stimulus. Rate of responding decreased with increasing postponement time and higher mean g-levels occurred at shorter intervals of postponement. Effects of the schedule parameter on response rate and mean g-level were similar to effects of the schedule on free-operant avoidance and on titration behavior maintained by shock.

Clark, F. C.↗
NASA NTRS1975

The upstream escape of energized solar wind protons from the bow shock

The paper analyzes the geometry of escape from the bow shock for solar wind protons in order to determine under what conditions a proton reflected from the bow shock can escape upstream or not. Some numerical examples show that protons with rather high energies and pitch angles can escape the shock at only marginally quasi-parallel field orientations, even if they have quite moderate speeds parallel to B. This does not provide evidence that such high energy protons are produced at the bow shock, but does show that such protons can escape upstream with the characteristics observed by Lin et al. (1974). It is also possible that some particles will encounter the shock two or more times, their total energy compounding until it reaches a high level.-

Greenstadt, E. W.↗
NASA NTRS1976

Wind enhanced planetary escape: Collisional modifications

The problem of thermal escape is considered in which both the effects of thermospheric winds at the exobase and collisions below the exobase are included in a Monte Carlo calculation. The collisions are included by means of a collisional relaxation layer of a background gas which models the transition region between the exosphere and the thermosphere. The wind effects are considered in the limiting cases of vertical and horizontal flows. Two species are considered: terrestrial hydrogen and terrestrial helium. In the cases of terrestrial hydrogen the escape fluxes were found to be strongly filtered or throttled by collisions at high exospheric temperatures. The model is applied to molecular hydrogen diffusing through a methane relaxation layer under conditions possible on Titan. The results are similar to the case of terrestrial hydrogen with wind enhanced escape being strongly suppressed by collisions. It is concluded that wind enhanced escape is not an important process on Titan.

Curtis, S. A.↗
NASA NTRS1976

Lunar escape systems feasibility study

Results are presented for a study conducted to determine the feasibility of simple lunar escape system concepts, to develop a spectrum of operational data, and to identify techniques and configurations suitable for the emergency escape mission. The study demonstrated the feasibility of the lunar emergency escape-to-orbit system (LESS) designed to provide a means for the two-man crew of a lunar module (LM) or extended-stay LM (ELM) to escape from the lunar surface in the event that the LM/ELM ascent stage becomes unsafe or is otherwise unable to take off. The LESS is to carry the two astronauts to a safe lunar orbit, where the Apollo command and service modules (CSM) are to be used for rendezvous and rescue, all within the lifetime of the backpack life support system (about 4 hr). It is concluded that simple manual control modes are sufficient, that simple boost profiles are acceptable, and that one man can deploy and set up the LESS. Initial guidance data can be calculated for the LESS by Mission Control and transmitted via the LM/ELM uplink.

Matzenauer, J. O.↗
NASA NTRS1977

Wind enhanced planetary escape - Collisional modifications

Effects of collisions and finite winds characteristic of a highly perturbed atmosphere on the thermal escape of terrestrial hydrogen and helium are investigated using a Monte Carlo approach. The limiting cases of vertical and horizontal winds are considered, and the relaxation layer between the collisionless exosphere and the collision-dominated thermosphere is modeled as a plane-parallel slab of given column density, depth, and atmospheric density. For both gases, the upwardly injected flux at the base of the relaxation layer is compared with the returning downward flux distribution at the same location; the technique is also applied to the atmosphere of Titan. The results show that inclusion of collisions in the escape model for terrestrial hydrogen with winds effectively throttles the escape process, that collisional throttling is negligible for helium when the exobase temperature is at least 5000 K, and that the escape of a planetary-atmosphere constituent depends on the ratio of its gravitational and kinetic energies as well as on the ratio of its mass to that of the background gas.

Curtis, S. A.↗
NASA NTRS1980

Modulation of terrestrial ion escape flux composition /by low-altitude acceleration and charge exchange chemistry/

Motivated by recent observations of highly variable hot plasma composition in the magnetosphere, control of the ionospheric escape flux composition by low-altitude particle dynamics and ion chemistry has been investigated for an e(-), H(+), O(+) ionosphere. It is found that the fraction of the steady state escape flux which is O(+) can be controlled very sensitively by the occurrence of parallel or transverse ion acceleration at altitudes below the altitude where the neutral oxygen density falls rapidly below the neutral hydrogen density and the ionospheric source of O(+) tends to be rapidly converted by charge exchange to H(+). The acceleration is required both to overcome the gravitational confinement of O(+) and to violate charge exchange equilibrium so that the neutral hydrogen atmosphere appears 'optically' thin to escaping O(+). Constraints are placed on the acceleration processes, and it is shown that O(+) escape is facilitated by observed ionospheric responses to magnetic activity.

Moore, T. E.↗
NASA NTRS1981

The dynamics of a rapidly escaping atmosphere - Applications to the evolution of earth and Venus

A simple model for the rapid escape of a hydrogen thermosphere is presented in order to establish the energy-limited flux of escaping particles. The model assumes that the atmosphere is tightly bound by gravity at the lower boundary, that all the EUV is absorbed in a narrow region where the optical depth is unity, and that the main source of heating is solar EUV. The flux is limited by the amount of EUV energy absorbed, which is in turn controlled by the radial extent of the thermosphere. It is found that, regardless of the amount of hydrogen in the thermosphere, the low temperatures which accompany rapid escape limit its extent and thus constrain the flux. The results are applied to the earth and Venus, showing that the escape of hydrogen from these planets would have been energy-limiting if their primordial atmospheres contained total hydrogen mixing ratios exceeding only a few percent. This conclusion places a constraint on the theory of the origin and evolution of the planets.

Watson, A. J.↗
NASA NTRS1987

Hypervelocity Technology (HVT) crew escape

Conceptual designs are being investigated for escape systems applicable to hypervelocity technology class aerospace vehicles. The concepts selected for further development will provide survivable escape and recovery throughout all phases of flight. Sixteen conceptual escape systems were identified, of which two were viable. The study vehicles included a horizontally launched vehicle (HLV) and a vertically launched vehicle (VLV). Computer-aided design models of the candidate escape systems were developed. State-of-the-art or near-term enabling technologies were identified in such areas as propulsion, life support, thermal protection, and deceleration.

Jines, Lanny A.↗
NASA NTRS1992

Helium escape from the Earth's atmosphere - The charge exchange mechanism revisited

We have studied the escape of neutral helium from the terrestrial atmosphere through exothermic charge exchange reactions between He(+) ions and the major atmospheric constituents N2, O2 and O. Elastic collisions with the neutral background particles were treated quantitatively using a recently developed kinetic theory approach. An interhemispheric plasma transport model was employed to provide a global distribution of He(+) ions as a function of altitude, latitude and local solar time and for different levels of solar ionization. Combining these ion densities with neutral densities from an MSIS model and best estimates for the reaction rate coefficients of the charge exchange reactions, we computed the global distribution of the neutral He escape flux. The escape rates show large diurnal and latitudinal variations, while the global average does not vary by more than a factor of three over a solar cycle. We find that this escape mechanism is potentially important for the overall balance of helium in the Earth's atmosphere. However, more accurate values for the reaction rate coefficients of the charge exchange reactions are required to make a definitive assessment of its importance.

Lie-Svendsen, O.↗