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At least 1,027 records · Page 57
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

Development of a new generation solid rocket motor ignition computer code

This report presents the results of experimental and numerical investigations of the flow field in the head-end star grain slots of the Space Shuttle Solid Rocket Motor. This work provided the basis for the development of an improved solid rocket motor ignition transient code which is also described in this report. The correlation between the experimental and numerical results is excellent and provides a firm basis for the development of a fully three-dimensional solid rocket motor ignition transient computer code.

Foster, Winfred A., Jr.↗
NASA NTRS1995

Analysis of advanced solid rocket motor ignition phenomena

This report presents the results obtained from an experimental analysis of the flow field in the slots of the star grain section in the head-end of the advanced solid rocket motor during the ignition transient. This work represents an extension of the previous tests and analysis to include the effects of using a center port in conjunction with multiple canted igniter ports. The flow field measurements include oil smear data on the star slot walls, pressure and heat transfer coefficient measurements on the star slot walls and velocity measurements in the star slot.

Foster, Winfred A., Jr.↗
NASA NTRS1994

Miniature laser ignited bellows motor

A miniature optically ignited actuation device has been demonstrated using a laser diode as an ignition source. This pyrotechnic driven motor provides between 4 and 6 lbs of linear force across a 0.090 inch diameter surface. The physical envelope of the device is 1/2 inch long and 1/8 inch diameter. This unique application of optical energy can be used as a mechanical link in optical arming systems or other applications where low shock actuation is desired and space is limited. An analysis was performed to determine pyrotechnic materials suitable to actuate a bellows device constructed of aluminum or stainless steel. The aluminum bellows was chosen for further development and several candidate pyrotechnics were evaluated. The velocity profile and delivered force were quantified using an non-intrusive optical motion sensor.

Renfro, Steven L.↗
NASA NTRS1998

Rocket Ignition Demonstrations Using Silane

Rocket ignition demonstration tests using silane were performed at the Penn State Combustion Research Laboratory. A heat sink combustor with one injection element was used with gaseous propellants. Mixtures of silane and hydrogen were used as fuel, and oxygen was used as oxidizer. Reliable ignition was demonstrated using fuel lead and and a swirl injection element.

Pal, Sibtosh↗
NASA NTRS1999

Ignition and Combustion of Bulk Metals in a Microgravity Environment

Results of a study of heterogeneous and homogeneous combustion of metals in reduced gravity are presented. Cylindrical titanium and magnesium samples are radiatively ignited in pure-oxygen at 1 atm. Qualitative observations, propagation rates, and burning times are extracted from high-speed cinematography. Time-resolved emission spectra of gas-phase reactions are acquired with an imaging spectrograph. Lower propagation rates of the reacting mass on titanium and of ignition waves on magnesium are obtained at reduced gravity. These rates are compared to theoretical results from fire-spread analyses with a diffusion/convection controlled reaction. The close agreement found between experimental and theoretical propagation rates indicates the strong influence of natural-convection-enhanced oxygen transp6rt on burning rates. Lower oxygen flux and lack of condensed product removal appear to be responsible for longer burning times of magnesium gas-phase diffusion flames in reduced gravity. Spherically symmetric explosions in magnesium flames at reduced gravity (termed radiation-induced metal explosions, or RIME) may be driven by increased radiation heat transfer from accumulated condensed products to an evaporating metal core covered by a porous, flexible oxide coating. In titanium specimens, predominantly heterogeneous burning characterizes the initial steady propagation of the molten mass, while homogeneous gas-phase reactions are detected around particles ejected from the molten mixture. In magnesium specimens, band and line reversal of all the UV spectral systems of Mg and MgO are attributed to the interaction between small oxide particles and the principal gaseous emitters.

Branch, Melvyn C.↗
NASA NTRS1998

Two-Dimensional Failure Waves and Ignition Fronts in Premixed Combustion

This paper is a continuation of our work on edge-flames in premixed combustion. An edge-flame is a two-dimensional structure constructed from a one-dimensional configuration that has two stable solutions (bistable equilibrium). Edge-flames can display wavelike behavior, advancing as ignition fronts or retreating as failure waves. Here we consider two one-dimensional configurations: twin deflagrations in a straining flow generated by the counterflow of fresh streams of mixture: and a single deflagration subject to radiation losses. The edge-flames constructed from the first configuration have positive or negative speeds, according to the value of the strain rate. But our numerical solutions strongly suggest that only positive speeds (corresponding to ignition fronts) can exist for the second configuration. We show that this phenomenon can also occur in diffusion flames when the Lewis numbers are small. And we discuss the asymptotics of the one-dimensional twin deflagration configuration. an overlooked problem from the 70s.

Vedarajan, T. G.↗
NASA NTRS2000

Polymer-Oxygen Compatibility Testing: Effect of Oxygen Aging on Ignition and Combustion Properties

The oxygen compatibility of six polymers used in oxygen service was evaluated after exposure for 48 hours to oxygen pressures ranging from 350 to 6200 kPa (50 to 900 psia), and temperatures ranging from 50 to 250 C (122 to 302 F). Three elastomers were tested: CR rubber (C873-70), FKM fluorocarbon rubber (Viton A), and MPQ silicone rubber (MIL-ZZ-765, Class 2); and three thermoplastics were tested: polyhexamethylene adipamide (Zytel 42), polytetrafluoroethylene (Teflon TFE), and polychlorotrifluoroethylene (Neoflon CTFE M400H). Post-aging changes in mass, dimensions, tensile strength, elongation at break, and durometer hardness were determined. Also, the compression set was determined for the three elastomers. Results show that the properties under investigation were more sensitive to oxygen pressure at low to moderate temperatures, and more sensitive to temperature at low to moderate oxygen pressures. Inspection of the results also suggested that both chain scissioning and cross-linking processes were operative, consistent with heterogeneous oxidation. Attempts are underway to verify conclusively the occurrence of heterogeneous oxidation using a simple modulus profiling technique. Finally, the effect of aging at 620 kpa (90 psia) and 121 C (250 F) on ignition and combustion resistance was determined. As expected, aged polymers were less ignitable and combustible (had higher AlTs and lower heats of combustion). Special attention was given to Neoflon CTFE. More specifically, the effect of process history (compression versus extrusion molding) and percent crystallinity (quick- versus slow-quenched) on the AIT, heat of combustion, and impact sensitivity of Neoflon CTFE was investigated. Results show the AIT, heat of combustion, and impact sensitivity to be essentially independent of Neoflon CTFE process history and structure.

Waller, Jess M.↗
NASA NTRS2002

The Revamping of an Ignition Test Facility

The revamping of an Ignition Test Facility, located in the Research Combustion Laboratory at the NASA Glenn Research Center, is presented. The history of how the test cell has adapted efficiently to a variety of test programs is discussed. The addition of a second test stand for ignition and small-scale rocket testing is detailed. An overview of the facility and the current test programs is offered. Planned upgrades for the future are outlined.

Kearns, Kimberly A.↗
NASA NTRS2003

Catalyzed Ignition of Bipropellants in Microtubes

This paper addresses the need to understand the physics and chemistry involved in propellant combustion processes in micro-scale combustors for propulsion systems on micro-spacecraft. These spacecraft are planned to have a mass less than 50 kilograms with attitude control estimated to be in the 10 milli-Newton thrust class. These combustors are anticipated to be manufactured using Micro Electrical Mechanical Systems (MEMS) technology and are expected to have diameters approaching the quenching diameter of the propellants. Combustors of this size are expected to benefit significantly from surface catalysis processes. Miniature flame tube apparatus is chosen for this study because microtubes can be easily fabricated from known catalyst materials and their simplicity in geometry can be used in fundamental simulations to more carefully characterize the measured heat transfer and pressure losses for validation purposes. Experimentally, we investigate the role of catalytically active surfaces within 0.4 and 0.8 mm internal diameter micro-tubes, with special emphases on ignition and extinction processes in fuel rich gaseous hydrogen and gaseous oxygen. Flame thickness and reaction zone thickness calculations predict that the diameters of our test apparatus are below the quenching diameter of the propellants in sub-atmospheric tests. Temperature and pressure rises in resistively heated platinum and palladium micro-tubes are used as an indication of exothermic reactions. Specific data on mass flow versus preheat temperature required to achieve ignition are presented.

Schneider, Steven J.↗
NASA NTRS2003

An Experimental Investigation of Hypergolic Ignition Delay of Hydrogen Peroxide with Fuel Mixtures

An experimental evaluation of decomposition and ignition delay of hydrogen peroxide at concentrations of 80% to 98% with combinations of hydrocarbon fuels, tertiary amines and transition metal chelates will be presented in the proposed paper. The results will be compared to hydrazine ignition delays with hydrogen peroxide and nitric acid mixtures using the same test apparatus.

Blevins, John A.↗
NASA NTRS2005

Fusion Ignition Rocket Engine with Ballistic Ablative Lithium Liner

Thermo-nuclear fusion may be the key to a high Isp, high specific power (low alpha) propulsion system. In a fusion system energy is liberated within, and imparted directly to, the propellant. In principle, this can overcome the performance limitations inherent in systems that require thermal power transfer across a material boundary, and/or multiple power conversion stages (NTR, NEP). A thermo-nuclear propulsion system, which attempts to overcome some of the problems inherent in the ORION concept, is described. A passive tapered liner is launched behind a vehicle, through a hole in a pusher-plate, that is connected to the vehicle by a shock-absorbing mechanism. A dense FRC plasmoid is then accelerated to high velocity (in excess of 1,000 km/s) and shot through the hole into the liner, when it has reached a given point down-range. The kinetic energy of the FRC is converted into thermal and magnetic-field energy, igniting a fusion bum in the magnetically confined plasma. The fusion reaction serves as an ignition source for the liner, which is made out of detonable materials. The energy liberated in this process is converted to thrust by the pusher-plate, as in the classic ORION concept. However with this concept, the vehicle does not carry a magazine of pre-fabricated pulse-units. A magnetic nozzle may also be used, in place of the pusher-plate. Estimates of the conditions needed to achieve a sufficient gain will be presented, along with a description of the driver characteristics. The incorporation of this concept into the propulsion system of a spacecraft will also be discussed.

Martin, Adam↗
NASA NTRS2005

A Study of Cavitation-Ignition Bubble Combustion

We present the results of an experimental and computational study of the physics and chemistry of cavitation-ignition bubble combustion (CIBC), a process that occurs when combustible gaseous mixtures are ignited by the high temperatures found inside a rapidly collapsing bubble. The CIBC process was modeled using a time-dependent compressible fluid-dynamics code that includes finite-rate chemistry. The model predicts that gas-phase reactions within the bubble produce CO and other gaseous by-products of combustion. In addition, heat and mechanical energy release through a bubble volume-expansion phase are also predicted by the model. We experimentally demonstrate the CIBC process using an ultrasonically excited cavitation flow reactor with various hydrocarbon-air mixtures in liquid water. Low concentrations (< 160 ppm) of carbon monoxide (CO) emissions from the ultrasonic reactor were measured, and found to be proportional to the acoustic excitation power. The results of the model were consistent with the measured experimental results. Based on the experimental findings, the computational model, and previous reports of the "micro-diesel effect" in industrial hydraulic systems, we conclude that CIBC is indeed possible and exists in ultrasonically- and hydrodynamically-induced cavitation. Finally, estimates of the utility of CIBC process as a means of powering an idealized heat engine are also presented.

Nguyen, Quang-Viet↗
NASA NTRS2007

Catalytic Ignition and Upstream Reaction Propagation in a Platinum Tube

A challenge for catalytic combustion in monolithic reactors at elevated temperatures is the start-up or "light-off" from a cold initial condition. In this work, we demonstrate a concept called "back-end catalytic ignition that potentially can be utilized in the light-off of catalytic monoliths. An external downstream flame or Joule heating raises the temperature of a small portion of the catalyst near the outlet initiating a localized catalytic reaction that propagates upstream heating the entire channel. This work uses a transient numerical model to demonstrate "back-end" ignition within a single channel which can characterize the overall performance of a monolith. The paper presents comparisons to an experiment using a single non-adiabatic channel but the concept can be extended to the adiabatic monolith case. In the model, the time scales associated with solid heat-up are typically several orders of magnitude larger than the gas-phase and chemical kinetic time-scales. Therefore, the model assumes a quasi-steady gas-phase with respect to a transient solid. The gas phase is one-dimensional. Appropriate correlations, however, account for heat and mass transfer in a direction perpendicular to the flow. The thermally-thin solid includes axial conduction. The gas phase, however, does not include axial conduction due to the high Peclet number flows. The model includes both detailed gas-phase and catalytic surface reactions. The experiment utilizes a pure platinum circular channel oriented horizontally though which a CO/O2 mixture (equivalence ratios ranging from 0.6 to 0.9) flows at 2 m/s.

Struk, P. M.↗
NASA NTRS2008

Numerical Determination of Critical Conditions for Thermal Ignition

The determination of ignition or thermal explosion in an oxidizing porous body of material, as described by a dimensionless reaction-diffusion equation of the form .tu = .2u + .e-1/u over the bounded region O, is critically reexamined from a modern perspective using numerical methodologies. First, the classic stationary model is revisited to establish the proper reference frame for the steady-state solution space, and it is demonstrated how the resulting nonlinear two-point boundary value problem can be reexpressed as an initial value problem for a system of first-order differential equations, which may be readily solved using standard algorithms. Then, the numerical procedure is implemented and thoroughly validated against previous computational results based on sophisticated path-following techniques. Next, the transient nonstationary model is attacked, and the full nonlinear form of the reaction-diffusion equation, including a generalized convective boundary condition, is discretized and expressed as a system of linear algebraic equations. The numerical methodology is implemented as a computer algorithm, and validation computations are carried out as a prelude to a broad-ranging evaluation of the assembly problem and identification of the watershed critical initial temperature conditions for thermal ignition. This numerical methodology is then used as the basis for studying the relationship between the shape of the critical initial temperature distribution and the corresponding spatial moments of its energy content integral and an attempt to forge a fundamental conjecture governing this relation. Finally, the effects of dynamic boundary conditions on the classic storage problem are investigated and the groundwork is laid for the development of an approximate solution methodology based on adaptation of the standard stationary model.

Luo, W.↗
NASA NTRS2009

Multimodal Friction Ignition Tester

The multimodal friction ignition tester (MFIT) is a testbed for experiments on the thermal and mechanical effects of friction on material specimens in pressurized, oxygen-rich atmospheres. In simplest terms, a test involves recording sensory data while rubbing two specimens against each other at a controlled normal force, with either a random stroke or a sinusoidal stroke having controlled amplitude and frequency. The term multimodal in the full name of the apparatus refers to a capability for imposing any combination of widely ranging values of the atmospheric pressure, atmospheric oxygen content, stroke length, stroke frequency, and normal force. The MFIT was designed especially for studying the tendency toward heating and combustion of nonmetallic composite materials and the fretting of metals subjected to dynamic (vibrational) friction forces in the presence of liquid oxygen or pressurized gaseous oxygen test conditions approximating conditions expected to be encountered in proposed composite material oxygen tanks aboard aircraft and spacecraft in flight. The MFIT includes a stainless-steel pressure vessel capable of retaining the required test atmosphere. Mounted atop the vessel is a pneumatic cylinder containing a piston for exerting the specified normal force between the two specimens. Through a shaft seal, the piston shaft extends downward into the vessel. One of the specimens is mounted on a block, denoted the pressure block, at the lower end of the piston shaft. This specimen is pressed down against the other specimen, which is mounted in a recess in another block, denoted the slip block, that can be moved horizontally but not vertically. The slip block is driven in reciprocating horizontal motion by an electrodynamic vibration exciter outside the pressure vessel. The armature of the electrodynamic exciter is connected to the slip block via a horizontal shaft that extends into the pressure vessel via a second shaft seal. The reciprocating horizontal motion can be chosen to be random with a flat spectrum over the frequency range of 10 Hz to 1 kHz, or to be sinusoidal at any peak-to-peak amplitude up to 0.8 in. (.2 cm) and fixed or varying frequency up to 1 kHz. The temperatures of the specimen and of the vessel are measured by thermocouples. A digital video camera mounted outside the pressure vessel is aimed into the vessel through a sapphire window, with its focus fixed on the interface between the two specimens. A position transducer monitors the displacement of the pneumatic-cylinder shaft. The pressure in the vessel is also monitored. During a test, the output of the video camera, the temperatures, and the pneumatic-shaft displacement are monitored and recorded. The test is continued for a predetermined amount of time (typically, 10 minutes) or until either (1) the output of the position transducer shows a sudden change indicative of degradation of either or both specimens, (2) ignition or another significant reaction is observed, or (3) pressure in the vessel increases beyond a pre-set level that triggers an automatic shutdown.

Davis, Eddie↗
NASA NTRS2010

Ignition-and-Growth Modeling of NASA Standard Detonator and a Linear Shaped Charge

The main objective of this study is to quantitatively investigate the ignition and shock sensitivity of NASA Standard Detonator (NSD) and the shock wave propagation of a linear shaped charge (LSC) after being shocked by NSD flyer plate. This combined explosive train was modeled as a coupled Arbitrary Lagrangian-Eulerian (ALE) model with LS-DYNA hydro code. An ignition-and-growth (I&G) reactive model based on unreacted and reacted Jones-Wilkins-Lee (JWL) equations of state was used to simulate the shock initiation. Various NSD-to-LSC stand-off distances were analyzed to calculate the shock initiation (or failure to initiate) and detonation wave propagation along the shaped charge. Simulation results were verified by experimental data which included VISAR tests for NSD flyer plate velocity measurement and an aluminum target severance test for LSC performance verification. Parameters used for the analysis were obtained from various published data or by using CHEETAH thermo-chemical code.

Oguz, Sirri↗
NASA NTRS2003

Promoted Ignition and Burning Tests of Stainless Steel in Flowing and Nonflowing Oxygen

The Industry-Sponsored Metals Combustion Test Program 96-1 was coordinated through Wendell Hull & Associates, Inc. on behalf of several contributing companies, and all design and testing was performed at the NASA White Sands Test Facility. Phase I of this test program studied the threshold pressure for self-sustained burning of various types and sizes of stain less steel rods in nonflowing oxygen, as observed in Standard Test Method for Determining the Combustion Behavior of Metallic Materials in Oxygen-Enriched Atmospheres (ASTM G 124-95). Phase II studied the ignition and propagation of burning of 316L stainless steel rods and pipe in flowing gaseous oxygen. The test sample configurations were chosen to replicate previous promoted ignition and burning tests as well as to represent geometries and cross-sectional thicknesses common in industrial piping applications. The gas pressw'es and velocities for the test matrix were selected to generally compare with CGA G-4.4 guidelines for the use of stain less steel in oxygen service. This paper summarizes the results from the Phase I nonflowing oxygen tests and presents in detail the results of the Phase II flowing oxygen tests. The maximum sample burn-length is shown as a function of test pressure in Phase 1 and also as a function of gas velocity in Phase IT. These results indicate that flowing oxygen, under the given test conditions, significantly affects maximum sample burn length as compared to nonflowing oxygen. Supplementary flowing oxygen test data on stainless steel rods from a follow-up test program are consistent with these results and are presented herein.

Forsyth, Elliot T.↗
NASA NTRS2010

Investigating Premature Ignition of Thruster Pressure Cartridges by Vibration-Induced Electrostatic Discharge

Pyrotechnic thruster pressure cartridges (TPCs) are used for aeroshell separation on a new NASA crew launch vehicle. Nondestructive evaluation (NDE) during TPC acceptance testing indicated that internal assemblies moved during shock and vibration testing due to an internal bond anomaly. This caused concerns that the launch environment might produce the same movement and release propellant grains that might be prematurely ignited through impact or through electrostatic discharge (ESD) as grains vibrated against internal surfaces. Since a new lot could not be fabricated in time, a determination had to be made as to whether the lot was acceptable to fly. This paper discusses the ESD evaluation and a separate paper addresses the impact problem. A challenge to straight forward assessment existed due to the unavailability of triboelectric data characterizing the static charging characteristics of the propellants within the TPC. The approach examined the physical limitations for charge buildup within the TPC system geometry and evaluated it for discharge under simulated vibrations used to qualify components for launch. A facsimile TPC was fabricated using SS 301 for the case and surrogate worst case materials for the propellants based on triboelectric data. System discharge behavior was evaluated by applying high voltage to the point of discharge in air and by placing worst case charge accumulations within the facsimile TPC and forcing discharge. The facsimile TPC contained simulated propellant grains and lycopodium, a well characterized indicator for static discharge in dust explosions, and was subjected to accelerations equivalent to the maximum accelerations possible during launch. The magnitude of charge generated within the facsimile TPC system was demonstrated to lie in a range of 100 to 10,000 times smaller than the spark energies measured to ignite propellant grains in industry standard discharge tests. The test apparatus, methodology, and results are described in this paper.

Woods, Stephen S.↗