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Development of a Composite Material Aerodynamic Demise Model for the Object Reentry Survival Analysis Tool (ORSAT)

The reentry demise of fiber-reinforced polymer (FRP) composites is an increasing concern for modern spacecraft at end of life. Unlike traditional materials such as metals, shredding of the material by aerodynamic forces appears to be a major component of the reentry demise mechanism. This paper will describe a new mechanical, strength-based, material demise model for the Object Reentry Survival Analysis Tool (ORSAT) Version 7.1. The model is based on laboratory in-situ and residual strength tests of several FRP materials performed during the NASA Orbital Debris Program Office’s Phase II Composite Material Demise test campaign. To test the residual strength of partially charred FRP materials, the authors tested 107 rectangular shaped samples of different thicknesses that were previously exposed to high-enthalpy flow at the University of Texas at Austin’s Inductively Coupled Plasma Torch facility. Tests were performed under normal atmospheric conditions at NASA Johnson Space Center’s Experimental Impact Laboratory using a Chatillon TCD1000 tensile test machine configured with a three-point bending jig. Mean fracture load, residual strength, delamination, and flexural modulus were measured for each test. An engineering model of aeromechanical demise for each material was developed by correlating the measured residual strength of the samples with the duration and magnitude of the applied heat flux and the mass loss and char progression. This model has been implemented in ORSAT 7.1 for the built-in, charring carbon fiber/epoxy and charring glass fiber/epoxy material models. The new model was verified by calculating the demise of hundreds of FRP composite fragments of various shapes and sizes and checking the calculations for consistency, with specific focus on material characterization in one-dimension. Further tests are planned in hypersonic flow facilities to validate the assumptions used in the model.

Priscilla A. Mendoza↗

NASA NTRS1986

Application of a Runge-Kutta scheme for high-speed inviscid internal flows

A multi-stage Runge-Kutta method is analyzed for solving the two-dimensional Euler equations for external and internal flow problems. Subsonic, supersonic and, highly supersonic flows are studied. Various techniques for accelerating the convergence to a steady state are described and analyzed. Effects of the grid aspect ratio on the rate of convergence are evaluated. An enthalpy damping technique applicable to supersonic flows is described in detail. Numerical results for supersonic flows containing both oblique and normal shocks are presented confirming the efficiency of the method.

Moitra, A.↗

NASA NTRS1986

Application of Runge-Kutta scheme for high-speed inviscid internal flows

Moitra, A.↗

DOE OSTI2023

Low- and high-temperature heat capacity of metallic technetium

The heat capacity of technetium metal has been measured from 2.1 K to 293 K using relaxation calorimetry and the enthalpy increment up to 1700 K using drop calorimetry. The low-temperature calorimetry measurements revealed a superconducting transition temperature of T C = (7.76 ± 0.08) K. The zero-degree Debye temperature(θ E ) and the electronic heat capacity coefficient ($γ_{e}$) of the normal state were derived as (307 ± 5) K and (4.22 ± 0.20) mJ·K –2 ·mol –1 , respectively. The standard entropy of the superconducting standard state was derived as $S^{°}_{m}$ (298.15) = (36.8 ± 1.3) J·K –1 ·mol –1 . The fitting of enthalpy-increment data together with high-temperature heat capacity data reported in literature yielded a heat capacity equation up to 1700 K.

36 MATERIALS SCIENCE↗

NASA NTRS1993

Comparison of Numerical Model Results with Diffusion Flames in Microgravity

The effects of gravity on methane diffusion flames were studied using a finite difference numerical model. Variables under consideration included velocity, pressure, temperature, enthalpy, reactive species, and inert carrier gas. Results obtained showed that flames in zero gravity were wider and taller than those in normal gravity. The use of a six reaction scheme produced similar predictions of flame width and height compared to those of the single reaction case. The numerical models predicted a considerable difference in the flame base region between normal gravity and low gravity. This region is considered to be beyond the boundaries of current analytical models.

Hyer, Paul V.↗

DOE OSTI2020

Determination of the enthalpy of adsorption of hydrogen in activated carbon at room temperature

The development of high-performance materials for hydrogen storage by adsorption requires detailed understanding of the adsorbate-adsorbent interactions, e.g., the enthalpy of adsorption ΔH, which measures the interaction strength. The determination of ΔH for a weakly adsorbing gas such as hydrogen in a carbonaceous porous material is difficult experimentally, normally requiring measuring two cryogenic adsorption isotherms. Here we demonstrate a calculation of ΔH based on ca. room temperature adsorption isotherms at 273 K and 296 K using the Clausius-Clapeyron equation. This requires an estimation of the volume of the adsorbed film (~40%, ~12% of the total pore volume at 77 K, 296 K, respectively) obtained from fits of the excess adsorption isotherms to an Ono-Kondo model with the auxiliary use of a fixed point corresponding to the saturation film density (estimated as 100 ± 20 g/L) which appears to be remarkably sample and temperature independent, i.e., a property of the adsorbate. The calculated room temperature enthalpy of adsorption ΔH = 8.3 ± 0.4 kJ/mol is in excellent agreement with the low-coverage cryogenic determination of ΔH. The methodology hereby proposed facilitates reliable calculations of the enthalpy of adsorption at room temperatures for weakly-adsorbing gases.

08 HYDROGEN↗

DOE OSTI2021

Effect of Temperature and FEC on Silicon Anode Heat Generation Measured by Isothermal Microcalorimetry

Isothermal microcalorimetry (IMC) was used to better understand parasitic reactions and heat generation from Si electrodes in the first 10 cycles using Li/Si half cells. Heat generation from cell polarization (ohmic heat), entropy changes (reversible heat), and parasitic reactions (parasitic heat) are separated and quantified. The effect of temperature and fluoroethylene carbonate (FEC) as an electrolyte additive are also explored. Our results show that at the C/10 cycling rate used here, ohmic heat makes the largest contribution to overall heat generation while reversible heat is the smallest. Ohmic heat generation increases with cycle number due to increasing internal resistance, though the effect is smaller for cells with FEC. Interestingly, capacity-normalized parasitic heat generation is largely unaffected by changes in temperature despite differing reaction kinetics. We show that this is caused by a decrease in average parasitic reaction enthalpy as temperature is increased. Further, cells with FEC display higher average parasitic reaction enthalpy than cells without. The average parasitic reaction enthalpies for all the Si electrodes we tested were lower than previously reported values for graphite, indicating that the SEI formed on Si is less stable.

25 ENERGY STORAGE↗

NASA NTRS1976

Table and charts of equilibrium normal-shock properties for hydrogen-helium mixtures with velocities to 70 km/sec. Volume 1: 0.95 H2-0.05 He (by volume)

Equilibrium thermodynamic and flow properties are presented in tabulated and graphical form for moving, standing, and reflected normal shock waves into hydrogen-helium mixtures representative of postulated outer planet atmospheres. These results are presented in four volumes and the volmetric compositions of the mixtures are 0.95H2-0.05He in Volume 1, 0.90H2-0.10He in Volume 2, 0.85H2-0.15He in Volume 3, and 0.75H2-0.25He in Volume 4. Properties include pressure, temperature, density, enthalpy, speed of sound, entropy, molecular-weight ratio, isentropic exponent, velocity, and species mole fractions. Incident (moving) shock velocities are varied from 4 to 70 km/sec for a range of initial pressure of 5 N/sq m to 100 kN/sq m. Results are applicable to shock-tube flows and for determining flow conditions behind the normal portion of the bow shock about a blunt body at high velocities in postulated outer planet atmospheres. The document is a revised version of the original edition of NASA SP-3085 published in 1974.

Miller, C. G., III↗

NASA NTRS2011

A Simple, Analytical Model of Collisionless Magnetic Reconnection in a Pair Plasma

A set of conservation equations is utilized to derive balance equations in the reconnection diffusion region of a symmetric pair plasma. The reconnection electric field is assumed to have the function to maintain the current density in the diffusion region, and to impart thermal energy to the plasma by means of quasi-viscous dissipation. Using these assumptions it is possible to derive a simple set of equations for diffusion region parameters in dependence on inflow conditions and on plasma compressibility. These equations are solved by means of a simple, iterative, procedure. The solutions show expected features such as dominance of enthalpy flux in the reconnection outflow, as well as combination of adiabatic and quasi-viscous heating. Furthermore, the model predicts a maximum reconnection electric field of E(sup *)=0.4, normalized to the parameters at the inflow edge of the diffusion region.

Hesse, Michael↗

NASA NTRS1950

Application of radial-equilibrium condition to axial-flow compressor and turbine design

Basic general equations governing the three-dimensional compressible flow of gas through a compressor or turbine are given in terms of total enthalpy, entropy, and velocity components of the gas. Two methods of solution are obtained for the simplified, steady axially symmetric flow; one involves the use of a number of successive planes normal to the axis of the machine and short distances apart, and the other involves only three stations for a stage in which an appropriate radial-flow path is used. Methods of calculation for the limiting cases of zero and infinite blade aspect ratios and an approximate method of calculation for finite blade aspect ratio are also given. In these methods, the blade loading and the shape of the annular passage wall may be arbitrarily specified.

Wu, Chung-Hua↗

NASA NTRS1974

Tables and charts of equilibrium normal shock and shock-tube solutions for helium-hydrogen mixtures with velocities to 70 km/sec

Equilibrium thermodynamic and flow properties are presented in tabulated and graphical form for moving, standing, and reflected normal shock waves into helium-hydrogen mixtures representative of proposed outer planet atmospheres. The volumetric compositions of these mixtures are 0.35He-0.65H2, 0.20He-0.80H2, and 0.05He-0.95H2. Properties include pressure, temperature, density, enthalpy, speed of sound, entropy, molecular-weight ratio, isentropic exponent, velocity, and species mole fractions. Incident (moving) shock velocities are varied from 4 to 70 km/sec for a range of initial pressure of 5 N/sq m to 100 kN/sq m. The present results are applicable to shock-tube flows and to free-flight conditions for a blunt body at high velocities. A working chart illustrating idealized shock-tube performance with a 0.20He-0.80H2 test gas and heated helium driver gas is also presented.

Miller, C. G., III↗

NASA NTRS1995

Scaling in a scramjet combustor

Studies of scramjet combustor scaling have been extended to include testing of a 'small' combustor, thereby allowing comparison with results obtained in a 'large' combustor of nearly identical configuration. The scale of the two combustors varied by a factor of 5. It was anticipated that the combustion process would scale as the product of pressure with length if the temperature, the Mach number, the velocity, the free stream composition and the equivalence ratio were the same. To achieve this while allowing for the necessary difference in pressure the two models were tested with different shock tunnel nozzles. The large was tested in a M = 8 nozzle, with an intake consisting of a pair of opposing wedges preceding the model, which produced shocks to reduce the Mach number to approximately 3.4 before the flow entered the model inlet. It was then expanded to raise the Mach number again. The small model was tested in a M = 4 nozzle, with the nozzle flow passing directly to the inlet of the model. The wedge intake for the large model was adjusted to yield similar combustion chamber Mach number for both models. Then, by matching the stagnation enthalpy, it was possible also to match the temperature and the velocity. The free stream composition was matched by operating at the same nozzle supply pressure. Wall pressure distributions were measured along each of the ducts. The pressure is normalized with respect to the pressure measured at the point opposite to the injector exit, and the distance downstream of the exit is normalized with respect to the height of the duct. It can be seen that, when normalized in this manner, both ducts produce quantitatively similar pressure distributions, confirming the initial hypothesis that the combustion process would scale as the product of pressure with length.

Pulsonetti, M. V.↗

NASA NTRS1989

Thermophysical properties of Helium-4 from 0.8 to 1500 K with pressures to 2000 MPa

Tabular summary data of the thermophysical properties of fluid helium are given for temperatures from 0.8 to 1500 K, with pressures to 2000 MPa between 75 and 300 K, or to 100 MPa outside of this temperature band. Properties include density, specific heats, enthalpy, entropy, internal energy, sound velocity, expansivity, compressibility, thermal conductivity, and viscosity. The data are calculated from a computer program which is available from the National Institute of Standards and Technology. The computer program is based on carefully fitted state equations for both normal and superfluid helium.

Arp, Vincent D.↗

NASA NTRS1993

Summary of the GASP code application and evaluation effort for scramjet combustor flowfields

Numerical simulations of 3D turbulent mixing and reacting flows have been systematically evaluated by comparison with experimental data and other numerical solutions to provide confidence in the General Aerodynamic Simulation Program (GASP) code version 1.3. Specifically, the GASP flow solver has been used to model high speed flow through scram jet combustors. Unit injector problems evaluated include (1) UVA staged sonic normal injection of air into Mach 2 air stream, (2) the VPI Mach 1.7 low angled (15 deg) flush wall helium injection into an unconfined Mach 6 'cold air' stream, and (3) the HYPULSE angled (30 deg) flush wall hydrogen injection into a Mach 6, high enthalpy (flight Mach 17 simulation) nitrogen and air test gases. Results of the numerical simulation for the first two test cases have been compared with detailed in-stream measurements and with SPARK CFD solutions. The results for the last two cases have been compared with measured wall pressure and heat flux data and with SPARK CFD solutions. The present GASP solutions compare favorably with both the experimental data and the SPARK solutions.

Srinivasan, Shivakumar↗

DOE OSTI2023

Stability Criteria for Self-Propagating Reaction Waves in Co/Al Multilayers

The propagation of self-sustained formation reactions in sputter-deposited Co/Al multilayers is known to exhibit a design-dependent instability. Multilayers having thin bilayers (<55 nm period) exhibit stable propagating waves, whereas those with a larger period react unstably. The specific two-dimensional (2D) instability observed involves the transverse propagation of a band in front of a stalled front commonly referred to as a “spin band.” Previous finite-element studies have shown that these instabilities are thermodynamically driven by the forward conduction of heat away from the flame front. However, the magnitude of that loss is inherently tied to the bilayer design in traditional bimetallic multilayers, which couples any proposed stability criteria to a varying critical diffusion distance. Here, this work utilizes a recently developed class of materials known as “inert-mediated reactive multilayers” to decouple the thermodynamic and kinetic contributions to propagating wave stability by reducing the stored chemical energy density in normally stable bilayer designs. By depositing an inert product phase (B2-CoAl) within the mid-plane of Co and Al reactant layers, spin instabilities arise as a function of both diluted volume and critical diffusion distance. From there, a stability criterion is determined for Co/Al multilayers based on enthalpy loss from the reaction zone, and its physical significance is explored.

36 MATERIALS SCIENCE↗

NASA NTRS1964

Experimental Data on Stagnation-Point Gas Injection Cooling on a Hemisphere-Cone in a Hypersonic Arc Tunnel

Exploratory tests were made to determine the reduction of heat transfer resulting from ejection of gases at the stagnation point on a hemisphere-cone at a nominal Mach number of about 9 and at stagnation enthalpies up to 1600 BTU per pound. Helium, nitrogen, and argon gases were used as coolants. The ratio of mass flow of coolant to the mass flow of air swept out by the model projected area was less than 0.20 in all cases. The experimental heat-transfer data were normalized by the calculated stagnation-point values based on test conditions in the tunnel and are presented as a function of the surface distance from the stagnation point. The variation of shock standoff distances with mass flow and volumetric flow of the gaseous ejectants is presented along with photographs of the luminous flow field of the model during tests.

STAGNATION FLOW↗

NASA NTRS2012

Photogrammetric recession measurements of an ablating surface

An instrument and method for measuring the time history of recession of an ablating surface of a test article during testing in a high enthalpy thermal test facility, such as an arcjet. The method advances prior art by providing time-history data over the full ablating surface without targets and without any modifications to the test article. The method is non-intrusive, simple to implement, requires no external light source, and does not interfere with normal operations of the arcjet facility.

Schairer, Edward T.↗

DOE OSTI2020

Glass transition temperature studies of planetary ball milled glasses: Accessing the rapidly cooled glassy state in Na 4 P 2 S 7-x O x , 0 ≤ x ≤ 7, Oxy-thio phosphate glasses

This paper details the very first in-depth study of the glass transition temperature (T g ) for planetary balled milled (PBM) Na 4 P 2 S 7-x O x (NaPSO), where 0 ≤ x ≤ 7, glasses. For 0 ≤ x ≤ 5, fully amorphous, homogeneous, and chemically reacted compositions can be prepared. For samples with 5 < x ≤ 7, partially amorphous but fully chemically reacted glass-ceramics can be produced. The reproducible, thermally cyclable onset T g and the onset crystallization temperature, T c , were investigated as a function of the composition and of the short-range order (SRO) structures of the glasses. Additionally, we examined the extreme sub-T g exothermic relaxations present due to the high energy milling processing and correspondingly high effective quenching rate. Using a differential scanning calorimeter (DSC) and scanning from well below the onset T g , the glasses are observed to relax exothermally below T g . The integrated relaxation enthalpy, ΔH rel , is ~ 0 for the x = 2 glass, but is significantly exothermic for lower and higher values of x. Once the high fictive state of these glasses has been erased by scanning to above the T g , but below the T c of the glass, the DSC scans of the glasses recover normal behavior for a normally cooled glass without any relaxation exotherm. The T g s of these glasses remain relatively constant for 0 ≤ x ≤ 3, but for glasses with 3 < x ≤ 5, T g increases sharply following the combined effects of the phosphate chain length increasing caused by the formation of bridging oxygens and the increasing concentration of more charge dense non-bridging oxygens (NBOs). For x > 5, both T g and Tc decrease sharply, becoming nearly identical at x = 7 where glass formation essentially ceases. For smaller values of x, T c increases with both chain length and the structural complexity of the composition but decreases sharply for glass-ceramics of x > 5.

36 MATERIALS SCIENCE↗