SEARCH · Engineering Papers
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.
The Planetary Science Decadal Survey [1] has identified Uranus as the highest priority destination for a flagship mission in the decade 2022-2032. Significant effort was expended across multiple teams in developing the concept study. The proposed poster will focus on the entry and descent aspects of an atmospheric probe, considered as part of the mission concept, and associated trades for viable trajectory options.
In this article we shall be concerned with the question of how to maximize the expected data return when the channel capacity cannot be predicted in advance. An example of this type is a planetary entry probe to Venus or Jupiter, whose atmospheric transmission characteristics are not yet fully known. And even if they were known, these transmission characteristics would be subject to unpredictable changes due to planet weather and/or entry trajectory.
Planetary quarantine analyses performed for recent unmanned Mars and Venus missions assumed that the probability of contamination by a spacecraft given accidental impact was equivalent to one. However, in the case of the gaseous outer planets, the heat generated during the inadvertent entry of a spacecraft into the planetary atmosphere might be sufficient to cause significant microbial burden reduction. This could affect navigation strategy by reducing the necessity for biasing the aim point away from the planets. An effort has been underway to develop the tools necessary to predict temperature histories for a typical spacecraft during inadvertent entry. In order that the results have general applicability, parametric analyses were performed. The thermal response of the spacecraft components and debris resulting from disintegration was determined. The temperature histories of small particles and composite materials, such as thermal blankets and an antenna, were given special attention. Guidelines are given to indicate the types of components and debris most likely to contain viable organisms, which could contaminate the lower layers of the Jovian atmosphere (approximately one atmosphere of pressure).
We discuss the INSIDE Jupiter (IJ) spacecraft. We detail the probes' science missions and data return and no-proprietary engineering aspects.
Results from flow and radiation simulations for the Hayabusa2 Sample Return Capsule (SRC) along its best-estimated trajectory (BET) are presented. Flow fields are first computed at several points along the best-estimated trajectory for a freestream consisting of N2, O2, Ar, CO2, and H2O; the last three are trace species in Earth’s atmosphere. The thermal response of an assumed ablative material is estimated and flow fields are recomputed at each time point with modified surface temperature distributions. The spectral radiance, from the combination of an aeroheated capsule and the high-temperature shock layer around it, is computed on an imaging plane for a given view angle and slant range at each time point. The radiance is transported through the intervening atmosphere between the Hayabusa2 SRC and the observing aircraft and upon integration over solid angle representing the field of view of the instruments converted to a spectral irradiance. The spectral irradiance is convolved with the instrument function to obtain results that can be directly compared with measurement. Fair to good comparisons with measurements required shifting the time coordinate of measurements by 7.5 s. The disagreement between prediction and measurement is substantial after about 72.5 s along the BET. Additional computations seem to support the idea of flow transition over the capsule.
Results from flow and radiation simulations for the Hayabusa2 Sample Return Capsule (SRC) along its best-estimated trajectory (BET) are presented. Flow fields are first computed at several points along the best-estimated trajectory for a freestream consisting of N2, O2, Ar, CO2, and H2O; the last three are trace species in Earth’s atmosphere. The thermal response of an assumed ablative material is estimated and flow fields are recomputed at each time point with modified surface temperature distributions. The spectral radiance, from the combination of an aeroheated capsule and the high-temperature shock layer around it, is computed on an imaging plane for a given view angle and slant range at each time point. The radiance is transported through the intervening atmosphere between the Hayabusa2 SRC and the observing aircraft and upon integration over solid angle representing the field of view of the instruments converted to a spectral irradiance. The spectral irradiance is convolved with the instrument function to obtain results that can be directly compared with measurement. Fair to good comparisons with measurements required shifting the time coordinate of measurements by 7.5 s. The disagreement between prediction and measurement is substantial after about 72.5 s along the BET. Additional computations seem to support the idea of flow transition over the capsule.
The entry of nuclear reactors into Earth's atmosphere resulting from an accidental or inadvertent abort of a space vehicle powered by nuclear-thermal rockets is investigated. The study is made for a typical piloted Mars mission vehicle incapacitated by an accident or malfunction during the Earth-arrival phase of the Mars-return journey due to simultaneous, multiple failures of its component systems. A single accident/abort scenario resulting in three entry possibilities is considered for a nominal hyperbolic in-bound approach velocity of 8 km/sec. The most severe case involving a direct entry is then analyzed over a broad range of approach velocities extending to 12 km/sec to include sprint-type missions. The results indicate that the severe surface heating, stagnation pressures, and g-loads are greater than 150 kW/sq cm, 300 atm, and 800-g, respectively. The wall heat transfer rate exceeds the value that can be accommodated by a carbon heatshield through radiation equilibrium prior to sublimation at 5500 K. These conditions are beyond our previous experience in crew safety, structural design, and thermal protection.
The Mars Pathfinder spacecraft will enter the Martian atmosphere directly from the interplanetary trajectory, at a relatively high velocity. The design of the nominal entry trajectory, and the accurate determination of potential trajectory dispersions, is necessary for the development of the Pathfinder Entry, Descent, and Landing (EDL) System.
Large meteoroids ablation and breakup mathematical model, estimating Mars atmosphere effectiveness as shield against surface impact craters production
Results from flow and radiation simulations for the Hayabusa2 Sample Return Capsule along its best-estimated trajectory are presented. The simulated spectral irradiances are compared with those measured by instruments onboard two airborne imaging platforms.
Results from pre-flight flow and radiation simulations for the OSIRIS-REx Sample Return Capsule along a candidate entry trajectory are presented. These results are from pre-flight simulations in support of the observation campaign. Details of the methodology for computing temporal variation of spectral irradiance on an instrument onboard an aerial observation platform are presented along with a sampling of results. An attempt is made to use the methodology presented to assess the level of elemental sodium in the shock layer. The final paper will be based on the actual flight trajectory and will include comparisons of predictions with calibrated spectrometric data.
The accuracy of Computational Fluid Dynamics predictions of subsonic capsule aerodynamics is examined by comparison against recent NASA wind-tunnel data at high-Reynolds-number flight conditions. Several aspects of numerical and physical modeling are considered, including inviscid numerical scheme, mesh adaptation, rough-wall modeling, rotation and curvature corrections for eddy-viscosity models, and Detached-Eddy Simulations of the unsteady wake. All of these are considered in isolation against relevant data where possible. The results indicate that an improved predictive capability is developed by considering physics-based approaches and validating the results against flight-relevant experimental data.
The entry of sample return vehicles (SRVs) into the Earth's atmosphere is the subject of this document. The Earth entry environment for vehicles, or capsules, returning from the planet Mars is discussed along with the subjects of dynamics, aerodynamics, and heat transfer. The material presented is intended for engineers and scientists who do not have strong backgrounds in aerodynamics, aerothermodynamics and flight mechanics. The document is not intended to be comprehensive and some important topics are omitted. The topics considered in this document include basic principles of physics (fluid mechanics, dynamics and heat transfer), chemistry and engineering mechanics. These subjects include: a) fluid mechanics (aerodynamics, aerothermodynamics, compressible fluids, shock waves, boundary layers, and flow regimes from subsonic to hypervelocity; b) the Earth s atmosphere and gravity; c) thermal protection system design considerations; d) heat and mass transfer (convection, radiation, and ablation); e) flight mechanics (basic rigid body dynamics and stability); and f) flight- and ground-test requirements; and g) trajectory and flow simulation methods.
In considering the problem of communicating with outer space and detection of spacecraft from the ground, one usually has to worry about only the propagation characteristics of electromagnetic waves of vacuum wavelength falling within either one of the two well known "atmospheric windows," namely; (1) the "optical window" extending from about 0.3 microns to a few microns, and (2) the "RF window" extending from a few millimeters to about 30 meters in the wavelength scale. However, during entry (or reentry) of a spacecraft into the earth's atmosphere, there exists two physical phenomena which tend to complicate the communication problem on the one hand, and to simplify the detection problem on the other hand.
High-mass planetary surface access is one of NASAs technical challenges involving entry, descent and landing (EDL). During the entry and descent phase, frictional interaction with the planetary atmosphere causes a heat build-up to occur on the spacecraft, which will rapidly destroy it if a heat shield is not used. However, the heat shield incurs a mass penalty because it must be launched from Earth with the spacecraft, thus consuming a lot of precious propellant. This NASA Innovative Advanced Concept (NIAC) project investigated an approach to provide heat shield protection to spacecraft after launch and prior to each EDL thus potentially realizing significant launch mass savings. Heat shields fabricated in situ can provide a thermal-protection system for spacecraft that routinely enter a planetary atmosphere. By fabricating the heat shield with space resources from materials available on moons and asteroids, it is possible to avoid launching the heat-shield mass from Earth. Regolith has extremely good insulating properties and the silicates it contains can be used in the fabrication and molding of thermal-protection materials. In this paper, we will describe three types of in situ fabrication methods for heat shields and the testing performed to determine feasibility of this approach.
Entry probe systems for characterizing, by in situ measurements, the atmospheric properties, chemical composition, and cloud structure of the planets Saturn, Uranus, and Jupiter are examined from the standpoint of unique mission requirements, associated subsystem performance, and degree of commonality of design. Past earth entry vehicles (PAET) and current planetary spacecraft (Pioneer Venus probes and Viking lander) are assessed to identify the extent of potential subsystem inheritance, as well as to establish the significant differences, in both form and function, relative to outer planet requirements. Recent research results are presented and reviewed for the most critical probe technology areas, including: science accommodation, telecommunication, and entry heating and thermal protection. Finally presented is a brief discussion of the use of decision analysis techniques for quantifying various probe heat-shield test alternatives and performance risk.
Stagnation point radiative heating rates for manned vehicles entering the earth's atmosphere at parabolic velocity are presented and compared with corresponding laminar convective heating rates. The calculations were made for both nonlifting and lifting entry trajectories for vehicles of varying nose radius, weight-to-area ratio, and drag. It is concluded from the results presented that radiative heating will be important for the entry conditions considered.
A study of scientific probes to explore the atmospheres of Saturn and Uranus to depths of between 2 and 30 bars is summarized. The study assessed configuration tradeoffs of recommended exploratory payloads, determined the types and quantities of the thermal control devices required, and evaluated thermal structural details and viable mission alternatives. These results indicated that a vented probe design with an environmental pressurization system for the first 2.5 bars of descent would satisfy the requirements for missions to either Saturn or Uranus to depths of approximately 20 bars. Parametric atmospheric descent thermal analyses are discussed and the effect of worst-case atmospheric models and navigational arrival uncertainties on mission performance are presented.