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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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NASA NTRSDate not supplied

Kalman Filtering and RTS Smoothing for Arc-Jet Sample Edge Tracking

Accurate and temporally consistent measurements of test-article recession are required to characterize material response during arc-jet ablation experiments. However, image-based boundary measurements are often affected by segmentation noise, brightness variations, and frame-to-frame variability. This work extends arcjetCV [1] with filtering methods for tracking the evolving boundaries of hemispherical and ISO-Q test articles. Two boundary-tracking approaches based on Kalman filtering [2] were implemented. The first applies a point-wise Kalman filter followed by a Rauch–Tung–Striebel smoother [3] to individual boundary-point locations. The second applies the same filtering and smoothing framework to a reduced set of geometry-dependent shape parameters. The point-wise method reduces local frame-to-frame fluctuations while preserving spatial details along the detected boundary. The shape-parameter method provides a compact and geometrically constrained estimate of the sample contour. Figure 1 illustrates the two approaches for a hemispherical test article. Both methods improve temporal consistency and support more robust estimation of surface recession from arc-jet imagery. The two filtering approaches provide complementary representations of boundary evolution and improve the reliability of image-based recession measurements during arc-jet experiments.

recession measurement↗
NASA NTRS2015

Summary of LOX/CH4 Thruster Technology Development at NASA/MSFC

In recent years, a variety of injectors for liquid oxygen (LOX) and methane (CH4) propellant systems have been designed, fabricated, and demonstrated with hot-fire testing at Marshall Space Flight Center (MSFC). Successful designs for liquid methane (LCH4) and gaseous methane (GCH4) have been developed. A variety of chambers, including a transpiration cooled design, along with uncooled ablatives and refractory metals, have also been hot-fire tested by MSFC for use with LOX/LCH4 injectors. Hot-fire testing has also demonstrated multiple ignition source options. Heat flux data for selected injectors has been gathered by testing with a calorimeter chamber. High performance and stable combustion have been demonstrated, along with designs for thrust levels ranging from 500 to 7,000 lbf. The newest LOX/CH4 injector and chamber developed by MSFC have been fabricated with additive manufacturing techniques and include unique design features to investigate regenerative cooling with methane. This low cost and versatile hardware offers a design for 4,000 lbf thrust and will be hot-fire tested at MSFC in 2015. Its design and operation can easily be scaled for use in systems with thrust levels up to 25,000 lbf.

Greene, Sandra Elam↗
NASA NTRS2016

Development of Advanced Conformal Ablative TPS Fabricated from Rayon- and PAN-Based Carbon Felts

The conformal ablative TPS first developed under NASA's Hypersonics Project in the early 2000's demonstrated very low through the thickness conductivity compared to state-ofthe- art PICA. However, in initial arcjet testing of Conformal-1, surface recession rates were 2x higher than PICA. Because commercial carbon felts are currently available as very thin substrates, this was a concern if conformal TPS were to be considered for a mission that required thicker material. Discussed in this paper are the results of the development of an Advanced Conformal TPS derived from thicker, higher density carbon felt. Two substrate systems were evaluated, the first material was a needled rayon-based carbon felt and the other a needled PAN-based carbon felt. Both substrates were impregnated with phenolic resin following the PICA/CPICA process to add a low density phenolic matrix to the system prior to aerothermal screening at the LaRC HyMETS facility and larger scale testing in the NASA ARC Interaction Heating Facility (IHF) at heating fluxes ranging from 250-1700 W/cm2.

Arcjet Testing↗
NASA NTRS2012

A Statistics-Based Material Property Analysis to Support TPS Characterization

Accurate characterization of entry capsule heat shield material properties is a critical component in modeling and simulating Thermal Protection System (TPS) response in a prescribed aerothermal environment. The thermal decomposition of the TPS material during the pyrolysis and charring processes is poorly characterized and typically results in large uncertainties in material properties as inputs for ablation models. These material property uncertainties contribute to large design margins on flight systems and cloud re- construction efforts for data collected during flight and ground testing, making revision to existing models for entry systems more challenging. The analysis presented in this work quantifies how material property uncertainties propagate through an ablation model and guides an experimental test regimen aimed at reducing these uncertainties and characterizing the dependencies between properties in the virgin and charred states for a Phenolic Impregnated Carbon Ablator (PICA) based TPS. A sensitivity analysis identifies how the high-fidelity model behaves in the expected flight environment, while a Monte Carlo based uncertainty propagation strategy is used to quantify the expected spread in the in-depth temperature response of the TPS. An examination of how perturbations to the input probability density functions affect output temperature statistics is accomplished using a Kriging response surface of the high-fidelity model. Simulations are based on capsule configuration and aerothermal environments expected during the Mars Science Laboratory (MSL) entry sequence. We identify and rank primary sources of uncertainty from material properties in a flight-relevant environment, show the dependence on spatial orientation and in-depth location on those uncertainty contributors, and quantify how sensitive the expected results are.

Copeland, Sean R.↗
NASA NTRS2006

Lightweight Ablative and Ceramic Thermal Protection System Materials for NASA Exploration Systems Vehicles

As a collaborative effort among NASA Centers, the "Lightweight Nonmetallic Thermal Protection Materials Technology" Project was set up to assist mission/vehicle design trade studies, to support risk reduction in thermal protection system (TPS) material selections, to facilitate vehicle mass optimization, and to aid development of human-rated TPS qualification and certification plans. Missions performing aerocapture, aerobraking, or direct aeroentry rely on advanced heatshields that allow reductions in spacecraft mass by minimizing propellant requirements. Information will be presented on candidate materials for such reentry approaches and on screening tests conducted (material property and space environmental effects tests) to evaluate viable candidates. Seventeen materials, in three classes (ablatives, tiles, and ceramic matrix composites), were studied. In additional to physical, mechanical, and thermal property tests, high heat flux laser tests and simulated-reentry oxidation tests were performed. Space environmental effects testing, which included exposures to electrons, atomic oxygen, and hypervelocity impacts, was also conducted.

Valentine, Peter G.↗
NASA NTRS1975

Interaction of graphite and ablative materials with CO2-laser, carbon-arc, and xenon-arc radiation

The behavior of graphite and several charring ablators in a variety of high radiative heat flux environments was studied in various radiative environments produced by a CO2 laser and a carbon arc facility. Graphite was also tested in xenon arc radiation. Tests were conducted in air nitrogen, helium, and a mixture of CO2 and nitrogen, simulating the Venus atmosphere. The experimental results are compared with theoretical results obtained with a one dimensional charring ablator analysis and a two dimensional subliming ablator analysis. Photomicroscopy showed no significant differences in appearance or microstructure of the charring ablators or graphite after testing in the three different facilities, indicating that the materials respond fundamentally the same to the radiation of different frequencies. The performance of phenolic nylon and graphite was satisfactorily predicted with existing analyses and published material property data.

Brewer, W. D.↗
NASA NTRS2018

Characterization of a Radiometer Window for Mars Aftbody Heating Including Ablation Product Deposition Using a Miniature Arc Jet

The Mars Entry, Descent, and Landing Instrumentation 2 (MEDLI2) sensor suite for the Mars 2020 mission includes a radiometer on the backshell to measure the radiative heating during entry into the Martian atmosphere. Thermal Protection System (TPS) ablation products may be deposited on the radiometer window which would degrade the transmission and thus alter the accuracy of the radiometer readings. Testing in NASA Ames Research Center's miniature arc jet (mARC) facility was conducted to deposit TPS ablation products on radiometer windows in an effort to characterize how the ablation products change the window transmission and thus alter radiometer performance. Heat flux and stagnation pressure characterization of the mARC facility in a 90 percent CO2, 10 percent N2 (by mass) Mars-like environment are presented. The spectral transmission of the radiometer windows before and after mARC testing are compared. Additionally, a discussion of how flight-like these test conditions were and future work to further characterize the effect of TPS ablation on radiometer performance are presented.

Miller, Ruth A.↗
NASA NTRS2011

Orion Flight Test-1 Thermal Protection System Instrumentation

The Orion Crew Exploration Vehicle (CEV) was originally under development to provide crew transport to the International Space Station after the retirement of the Space Shuttle, and to provide a means for the eventual return of astronauts to the Moon. With the current changes in the future direction of the United States human exploration programs, the focus of the Orion project has shifted to the project s first orbital flight test, designated Orion Flight Test 1 (OFT-1). The OFT-1 is currently planned for launch in July 2013 and will demonstrate the Orion vehicle s capability for performing missions in low Earth orbit (LEO), as well as extensibility beyond LEO for select, critical areas. Among the key flight test objectives are those related to validation of the re-entry aerodynamic and aerothermal environments, and the performance of the thermal protection system (TPS) when exposed to these environments. A specific flight test trajectory has been selected to provide a high energy entry beyond that which would be experienced during a typical low Earth orbit return, given the constraints imposed by the possible launch vehicles. This trajectory resulted from a trade study that considered the relative benefit of conflicting objectives from multiple subsystems, and sought to provide the maximum integrated benefit to the re-entry state-of-the-art. In particular, the trajectory was designed to provide: a significant, measureable radiative heat flux to the windward surface; data on boundary transition from laminar to turbulent flow; and data on catalytic heating overshoot on non-ablating TPS. In order to obtain the necessary flight test data during OFT-1, the vehicle will need to have an adequate quantity of instrumentation. A collection of instrumentation is being developed for integration in the OFT-1 TPS. In part, this instrumentation builds upon the work performed for the Mars Science Laboratory Entry, Descent and Landing Instrument (MEDLI) suite to instrument the OFT-1 ablative heat shield. The MEDLI integrated sensor plugs and pressure sensors will be adapted for compatibility with the Orion TPS design. The sensor plugs will provide in-depth temperature data to support aerothermal and TPS model correlation, and the pressure sensors will provide a flush air data system for validation of the entry and descent aerodynamic environments. In addition, a radiometer design will be matured to measure the radiative component of the reentry heating at two locations on the heat shield. For the back shell, surface thermocouple and pressure port designs will be developed and applied which build upon the heritage of the Space Shuttle Program for instrumentation of reusable surface insulation (RSI) tiles. The quantity and location of the sensors has been determined to balance the needs of the reentry disciplines with the demands of the hardware development, manufacturing and integration. Measurements which provided low relative value and presented significant engineering development effort were, unfortunately, eliminated. The final TPS instrumentation has been optimized to target priority test objectives. The data obtained will serve to provide a better understanding of reentry environments for the Orion capsule design, reduce margins, and potentially reduce TPS mass or provide TPS extensibility for alternative missions.

Kowal, T. John↗
NASA NTRS1977

Moldable cork ablation material

A successful thermal ablative material was manufactured. Moldable cork sheets were tested for density, tensile strength, tensile elongation, thermal conductivity, compression set, and specific heat. A moldable cork sheet, therefore, was established as a realistic product.

Source record↗
NASA NTRS1977

Arc heater code validation tests of heat shield materials

Results are reported for tests of candidate heat-shield materials for outer-planet entry probes, which were conducted in two different arc-heater facilities at heating rates below those predicted for entry. One facility supplied a combined radiative-convective heating environment in air while the other provided a hydrogen/helium environment for convective heating only. Both 'infinite-slab' and 'finite-slab' models consisting of various carbon phenolic (CP) and fused silica (FS) materials were tested. The test results obtained are expressed in terms of ablation rates and surface as well as in-depth temperature variations with time for the air environment and in terms of normalized ablation rate as a function of temperature for the H/He environment. The measured values are compared with calculations based on a charring material thermal response and ablation code. For the CP models, good agreement between predicted and measured mass-loss rates is noted, surface temperatures in air are predicted within 18%, and in-depth temperature predictions are shown to be conservative in comparison with measured values. For the FS models, discrepancies are found between the predicted and measured mass-loss rates and surface temperatures.

Kesselring, J. P.↗
NASA NTRS2017

Laser Ablation Experiments on the Tamdakht H5 Chondrite

High-powered lasers were used to induce ablation and to form fusion crusts in the lab on Tamdakht H5 chondrites and basalt. These ground tests were undertaken to improve our understanding, and ultimately improve our abilty to model and predict, meteoroid ablation during atmospheric entry. The infrared fiber laser at the LHMEL facilty, operated in the continuous wave (i.e. non-pulsed) mode, provided radiation surface heat flux at levels similar to meteor entry for these tests. Results are presented from the first round of testing on samples of Tamdakht H5 ordinary chondrite which were ex-posed to entry-relevant heating rates between 2 and 10 kWcm2.

meteor↗
NASA NTRS1972

Determination of the effects of graphite material properties on ablation performance.

Application of statistical methods to the problem of identifying those material properties of artificial graphite having the strongest effect on ablation performance. Ablation performance, as determined by total length change during test, recession rate, surface temperature, surface texture, and degree of gouging, was measured on 40 different, commercially available, artificial graphites in a Mach 2 airstream having a nominal enthalpy of 2.2 MJ/kg and a stagnation pressure of 5.6 atm. Eighteen material properties were measured on these same graphites, and correlations between pairs of these material properties were developed where possible, reducing the original 18 properties to ten mutually independent properties. Multiple regression equations were formulated relating ablation performance to the reduced set of ten independent material properties, thereby identifying those material properties having the most pronounced effect on ablation performance. These regression equations reveal that for optimum ablation performance in the present environment, grain size should be small, ash content low, density and thermal conductivity high, and mean pore radius large.

Maahs, H. G.↗
NASA NTRS2010

Validation of a Three-Dimensional Ablation and Thermal Response Simulation Code

The 3dFIAT code simulates pyrolysis, ablation, and shape change of thermal protection materials and systems in three dimensions. The governing equations, which include energy conservation, a three-component decomposition model, and a surface energy balance, are solved with a moving grid system to simulate the shape change due to surface recession. This work is the first part of a code validation study for new capabilities that were added to 3dFIAT. These expanded capabilities include a multi-block moving grid system and an orthotropic thermal conductivity model. This paper focuses on conditions with minimal shape change in which the fluid/solid coupling is not necessary. Two groups of test cases of 3dFIAT analyses of Phenolic Impregnated Carbon Ablator in an arc-jet are presented. In the first group, axisymmetric iso-q shaped models are studied to check the accuracy of three-dimensional multi-block grid system. In the second group, similar models with various through-the-thickness conductivity directions are examined. In this group, the material thermal response is three-dimensional, because of the carbon fiber orientation. Predictions from 3dFIAT are presented and compared with arcjet test data. The 3dFIAT predictions agree very well with thermocouple data for both groups of test cases.

Chen, Yih-Kanq↗
NASA NTRS1974

PERF - A new approach to the experimental study of radiative aerodynamic heating and radiative blockage by ablation products

The present work describes a facility designed to validate the various aspects of radiative flow field theory, including the absorption of shock layer radiation by ablation products. The facility is capable of producing radiation with a spectrum similar to that of an entry vehicle shock layer and is designed to allow measurements at vacuum ultraviolet wavelengths where the most significant absorption by ablation products is predicted to occur. The design concept of the facility is presented along with results of theoretical analyses carried out to assess its research potential. Experimental data obtained during tests that simulated earth and Venusian entry and in which simulated ablation products were injected into the stagnation region flow field are discussed.

Walberg, G.↗
NASA NTRS2003

Aerogel Composites for Aerospace Thermal Protection

Aerogel composites formed by infiltrating organic and/or inorganic aerogels into fiber matrix materials enable us to exploit the low thermal conductivity and low density of aerogels while maintaining the strength, structure and other useful properties of a porous fiber matrix. New materials for extreme heating ranges are needed to insulate future spacecraft against the extreme heat of planetary atmospheric entry, but the insulation mass must be minimized in order to maximize the payload. A reusable system passively insulates to survive heating unchanged for relatively low heating. Ablators, which sacrifice mass to control heating, are used to protect vehicles against more extreme heating for a single use thermal protection system (TPS). Aerogel composites were fabricated and tested for spacecraft thermal protection. The high-temperaturey high heat flux tests described in this paper were performed in NASA Ames arc-jet facilities to simulate spacecraft atmospheric entry, and include heating conditions predicted for the forebody and backshell of the Mars Science Lander (MSL) entry probe. The aerogel composites tested showed excellent thermal performance in the arc-jet tests, functioning both as reusuable insulation under lower heat fluxes, and as ablative aerogels under the extreme heating predicted for the MSL forebody.

White, Susan↗
NASA NTRSDate not supplied

Multiscale Modeling of Woven Ablative Thermal Protection System Materials

The NASA Entry Systems Modeling project maintains a portfolio of computational model and tool development activities focused on reducing performance uncertainties in ablative Thermal Protection System (TPS) materials for NASA missions. The development activities span material scale and strive to allow microstructural characterization of material structure and properties, mesoscale analyses of damage, and macroscale evaluation of heatshield performance and recession in a given aerothermodynamic environment. This talk will detail the application of developed capabilities at all three scales to the woven TPS material that the Agency has selected as the heatshield for the Mars Sample Return Earth Entry System (MSR-EES) mission – 3D Mid-Density Carbon Phenolic (3MDCP). Each of the applications focuses on driving down uncertainties in material performance and thus risk for MSR-EES and other future missions that may leverage woven TPS. At the microscale, machine learning techniques are used to characterize images from destructive microscopy and inform structural variability. At the mesoscale, Lagrangian techniques are used to simulate ballistic impact and interpret damage modes noted in experiments. At the macroscale, coupled flow-material response techniques are validated by Arc Jet testing to enable heatshield design for missions with massive ablation.

Justin B Haskins↗
NASA NTRS1972

The ablation of graphitic materials in the sublimation regime.

A large variety of graphitic materials have been tested in an arc heated air stream at a surface pressure of 4.3 atm and a nominal surface temperature of 3925 K. Included were commercial and developmental grades of artificial graphites, both two and three dimensional carbon-carbon composites, composites seeded with refractory compounds, and several special materials such as pyrolytic graphite, mesophase graphite, glassy carbon, and natural graphite. ATJ graphite was used as a control material. Except for the seeded materials which had poor performance, the mass loss rate for all the man-made graphitic materials fell within the range of 17 per cent less to 30 per cent more than the rate for ATJ. Thus it is concluded that wide variations in constituents, processing, fabrication and structure have relatively little effect on the ablation performance of graphitic materials, at least under the conditions of the present tests. Particulate mass loss was observed for all the materials tested and is the dominant mechanism for mass removal at the present test conditions. It is suggested that this mechanism results from physical failure, primarily by compressive thermal stress.

Lundell, J. H.↗
NASA NTRS2018

Boeing: Arc Jet Exposure of Ablative Non-Oxide CMC TPS for Planetary Probe and Sample Return Applications

NASA Game Changing Development (GCD) provided Boeing support under a Space Act Agreement (SAA) for arc jet sample design, CFD support and arc jet test time of stagnation and shear models for 3 Boeing TPS materials: BLA (Boeing Lightweight Ablator, 18, 21 and 22 densities), BPA (Boeing Phenolic Ablator, standard, graded density, or without reinforcement) and Non-oxide high temperature ceramic composite for structurally integrated TPS (SITPS). Results: For BLA, tested successfully to 500 W/cm² heat flux and heat loads up to 12 kJ/cm² with shear loads up to 370 Pa. The BPA 2017 formulation tested successfully to 1500 W/cm² and 80 kJ/cm², with shear loads up to 250 Pa. For SITIPS, Boeing fabricated C/SiC laminate materials survived testing in shear.

commercial space↗