Search NASA⌕ Search

SEARCH · Search NASA

Results for “Atmospheric Entries”

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.

At least 415 records · Page 23
All sourcesNASA NTRSDOE OSTI
NASA NTRS2018

Aerothermal Design of a Common Probe for Multiple Planetary Destinations

The idea of a single design of a capsule, for atmospheric entry at Venus, Jupiter, Saturn, Uranus, and Neptune and delivery of payloads for in situ scientific experiments, is currently being pursued by a team of scientists and engineers drawn from four NASA centers - Ames, Langley, JPL, and Goddard. For notional suites of instruments (the selection depending on the destination), interplanetary trajectories have been developed by team members at JPL and Goddard. Using the entry states provided by these trajectories, 3DOF atmospheric flight trajectories have been developed by Langley [4] and Ames. The range of entry flight path angles for each destination is chosen such that the deceleration load lies between 50 g (shallow) and 150-200 g (steep) for a 1.5 m (diameter) rigid aeroshell based on a 45deg sphere-cone geometry and an entry mass of 400 kg.

Allen Jr., G. A.↗
NASA NTRS2015

Radiant Heating Tests on Meteoritic Material

A new effort geared toward modeling the physics of meteor entry and break-up is underway at NASA Ames Research Center. This is part of a broader interdisciplinary effort on providing physics-based risk assessment models for potentially hazardous objects. As part of the entry modeling task we are seeking to improve our understanding of, among other things, the ablation of meteoric material during high speed entry into earths atmosphere. Meteoroid entry differs greatly in some key respects from spacecraft entry modeling. First, the aerothermal environment at these high velocities (18 km/s) is dominated by radiation. Second, meteoroids less than, say, 50m in size, will likely lose a significant portion of their mass during the high-speed atmospheric entry process due to vaporization as well as melting and spallation. The mass of the object, in turn, directly affects the amount of energy deposited in the atmosphere, and therefore the amount of damage done. Thus it is important for us to understand and be able to model this process in greater detail in order to assess the hazard posed by these objects.In this presentation, we first give an overview of the simple ablation models that are typically used in meteor entry calculations. Additionally, we will present a new model which utilizes a similar approach to what is typically done for spacecraft TPS response modeling. This uses an equilibrium assumption near the surface to compute the ablation rate, as is done in heritage material response codes. Next we describe the radiant heating experiment which uses a high-powered laser to emulate the radiation dominated heating environment experienced by meteoroids during atmospheric entry. The facility the Laser Hardened Material Evaluation Laboratory (LHMEL) permits us to expose samples of meteoritic material to heating rates in excess of 100kW/sq.cm. An overview of the experimental set-up and test plan for the initial exploratory campaign at this facility will be given. Then we present both qualitative and quantitative results from this initial test series. Comparisons between predicted and measured ablation rates suggest that there may be significant blockage of the incident beam by the ablation plume. Furthermore, melt is shown to be a significant ablation mechanics, even at high heating rates (16 kW/sq.cm). Finally, comparisons between the phenomenology of the ablation of terrestrial rocks namely, basalt -- to that of meteorites show very different behavior. This is shown to likely be due in part to the effect of composition on the melt viscosity.

Stern, Eric↗
NASA NTRSDate not supplied

A Green’s Function Sensor Fusion Approach for Evaluating Spacecraft Entry Heating From on-Board Thermal Instrumentation

During atmospheric entry, distributed thermal measurements are critical to enable the evaluation of heat loads on spacecraft thermal protection systems (TPS). In recent space exploration missions, Schmidt-Boelter-type heat flux gauges have been integrated into the TPS alongside conventional temperature measurement instrumentation to measure total (convective and radiative) and radiative heat transfer rates1,2. While direct heat flux sensors (HFS) are able to provide valuable information detailing the thermal loads experienced by spacecraft, the interpretation of these measurements in unsteady, convective environments requires a correction factor to account for local heating augmentations at the cold wall HFS surface2,3. Current efforts to estimate cold wall correction factors, and thus recover the hot wall TPS heat flux, rely on time-marching computational fluid dynamics (CFD) simulations2. Simulation-based methods are susceptible to large uncertainties, however, as they require estimations of vehicle trajectory, gas kinetics, wall catalysis models, and other flight conditions as input parameters2,4. Furthermore, CFD simulations are computationally expensive and cannot efficiently survey all possible entry scenarios, exacerbating the uncertainty of reconstructed hot wall heat flux values. These drawbacks motivate the development of alternative hot wall heat flux reconstruction methods that are not reliant on CFD-based correction factors.

Kenneth McAfee↗
NASA NTRSDate not supplied

A Green’s Function Sensor Fusion Approach for Evaluating Spacecraft Entry Heating From on-Board Thermal Instrumentation

During atmospheric entry, distributed thermal measurements are critical to enable the evaluation of heat loads on spacecraft thermal protection systems (TPS). In recent space exploration missions, Schmidt-Boelter-type heat flux gauges have been integrated into the TPS alongside conventional temperature measurement instrumentation to measure total (convective and radiative) and radiative heat transfer rates1,2. While direct heat flux sensors (HFS) are able to provide valuable information detailing the thermal loads experienced by spacecraft, the interpretation of these measurements in unsteady, convective environments requires a correction factor to account for local heating augmentations at the cold wall HFS surface2,3. Current efforts to estimate cold wall correction factors, and thus recover the hot wall TPS heat flux, rely on time-marching computational fluid dynamics (CFD) simulations2. Simulation-based methods are susceptible to large uncertainties, however, as they require estimations of vehicle trajectory, gas kinetics, wall catalysis models, and other flight conditions as input parameters2,4. Furthermore, CFD simulations are computationally expensive and cannot efficiently survey all possible entry scenarios, exacerbating the uncertainty of reconstructed hot wall heat flux values. These drawbacks motivate the development of alternative hot wall heat flux reconstruction methods that are not reliant on CFD-based correction factors.

Kenneth McAfee↗
NASA NTRSDate not supplied

A Green’s Function Sensor Fusion Approach for Evaluating Spacecraft Entry Heating From on-Board Thermal Instrumentation

During atmospheric entry, distributed thermal measurements are critical to enable the evaluation of heat loads on spacecraft thermal protection systems (TPS). In recent space exploration missions, Schmidt-Boelter-type heat flux gauges have been integrated into the TPS alongside conventional temperature measurement instrumentation to measure total (convective and radiative) and radiative heat transfer rates1,2. While direct heat flux sensors (HFS) are able to provide valuable information detailing the thermal loads experienced by spacecraft, the interpretation of these measurements in unsteady, convective environments requires a correction factor to account for local heating augmentations at the cold wall HFS surface2,3. Current efforts to estimate cold wall correction factors, and thus recover the hot wall TPS heat flux, rely on time-marching computational fluid dynamics (CFD) simulations2. Simulation-based methods are susceptible to large uncertainties, however, as they require estimations of vehicle trajectory, gas kinetics, wall catalysis models, and other flight conditions as input parameters2,4. Furthermore, CFD simulations are computationally expensive and cannot efficiently survey all possible entry scenarios, exacerbating the uncertainty of reconstructed hot wall heat flux values. These drawbacks motivate the development of alternative hot wall heat flux reconstruction methods that are not reliant on CFD-based correction factors.

Kenneth McAfee↗
NASA NTRS2015

Adaptable, Deployable Entry and Placement Technology (ADEPT) Overview of FY15 Accomplishments

ADEPT is an atmospheric entry architecture for missions to most planetary bodies with atmospheres: Current Technology development project funded under STMD Game Changing Development Program (FY12 start); stowed inside the launch vehicle shroud and deployed in space prior to entry; low ballistic coefficient (less than 50 kilograms per square meter) provides a benign deceleration and thermal environment to the payload; High-temperature ribs support three dimensional woven carbon fabric to generate drag and withstand high heating.

technology↗
NASA NTRS2005

NASA Ames Arc Jets and Range, Capabilities for Planetary Entry

NASA is pursuing innovative technologies and concepts as part of America's Vision for Space Exploration. The rapidly emerging field of nanotechnology has led to new concepts for multipurpose shields to prevent catastrophic loss of vehicles and crew against the triple threats of aeroheating during atmospheric entry, radiation (Solar and galactic cosmic rays) and Micrometorid/Orbital Debris (MMOD) strikes. One proposed concept is the Thermal Radiation Impact Protection System (TRIPS) using carbon nanotubes, hydrogenated carbon nanotubes, and ceramic coatings as a multi-use TPS. The Thermophysics Facilities Branch of the Space Technology Division at NASA Ames Research Center provides testing services for the development and validation of the present and future concepts being developed by NASA and national and International research firms. The Branch operates two key facilities - the Range Complex and the Arc Jets. The Ranges include both the Ames Vertical Gun Range (AVGR) and the Hypervelocity Free Flight (HFF) gas guns best suited for MMOD investigations. Test coupons can be installed in the AVGR or HFF and subjected to particle impacts from glass or metal particles from micron to _ inch (6.35-mm) diameters and at velocities from 5 to 8 kilometers per second. The facility can record high-speed data on film and provide damage assessment for analysis by the Principle Investigator or Ames personnel. Damaged articles can be installed in the Arc Jet facility for further testing to quantify the effects of damage on the heat shield s performance upon entry into atmospheric environments.

Fretter, Ernest F.↗
NASA NTRS1988

Planetary operations for the Pioneer Venus Orbiter mission

The Pioneer Venus Orbiter was inserted into Venus orbit on December 4, 1974 and is expected to operate until 1992. This paper discusses the scientific objectives of the Pioneer Venus Orbiter Project components, i.e., the Orbiter spacecraft, the atmosphere entry Probes, and the probe Bus, together with the design and operation characteristics of the Orbiter. Consideration is also given to the science instruments of the Orbiter, to their requirements with respect to pointing, orientation, and timing, and to the ground operations system. The Probes, the Bus, and the Orbiter were selected to study Venus in complementary ways: the Probes by sounding through most of the atmosphere at four locations, the probe Bus by sounding through the upper atmosphere during entry, and the Orbiter by in situ planet-wide observations of the ionosphere and the extreme upper atmosphere, and by examining the surface and interior remotely. In addition, the Orbiter also observes the interactions of Venus with the solar environment.

Jackson, Robert W.↗
NASA NTRS1978

Thermal structure of Mars' atmosphere from Viking entry measurements

An experimental study using accelerometers as well as pressure and temperature sensors was carried out for accurate determination of the thermal structure of the atmosphere of Mars from nominally 100-km altitude to the planet surface during atmosphere entry of the two Viking landers. A comparison was made with the neutral thermal structure above 130 km and with the ion temperatures. Both entries exhibited strong temperature fluctuations about the mean, which was attributed to thermal tides. The mean temperature of the atmosphere above the boundary layer was shown to be governed by radiative equilibrium, while the radiative boundary layer was observed to be 4 km deep. Ion temperatures indicated a structure correlated with that of the neutral atmosphere at altitudes up to 160 km. Thickness of the convective boundary layer was 6.5 km in late summer afternoon.

Seiff, A.↗
NASA NTRS1972

The aerothermodynamic environment of the Apollo command module during superorbital entry

Aerothermodynamic measurements were obtained on two Apollo spacecraft during atmospheric entry at near-lunar-return velocities. Histories of measured pressure and of convective and radiative heating rates are compared with theoretical predictions and with wind-tunnel results. The comparisons show that pressures measured in the wind tunnel correspond to those measured in the flight environment of the entry face. Unexplained low pressures were obtained on the conical section. Measured radiative heating rates agree with predictions calculated for both visible and infrared radiation. Good agreement was found between convective heating rates measured in flight and predictions obtained by using cold wall theory adjusted for mass injection from the ablator.

Lee, D. B.↗
NASA NTRS1994

Aerobraking the Magellan Spacecraft in Venus Orbit

A spacecraft which was not designed for atmospheric entry was successfully flown in the sensible atmosphere of Venus during the periapsis passes of more than 700 orbits, thus becoming the first spacecraft to demonstrate the use of aerobraking to significantly alter the shape of its orbit at another planet. This experimental operation utilized the force imparted by atmospheric drag near periapsis to reduce the altitude of apoapsis by nearly 8000 km using little propellant. A description of the Magellan spacecraft is briefly reviewed; its configuration and operation during aerobraking is discussed, as are its behavior in the atmosphere, concerns for possible damage, the resulting orbit, and the unique demands placed on the spacecraft controllers and JPL's Deep Space Network tracking facility (DSN), during the aerobraking operation.

Magellan Venus aerobraking↗