Rocket Exhaust Research Articles

Safe Testing of Nuclear Rockets

In the early 1960s, Werner Von Braun and others recognized the need for a nuclear rocket for sending humans to Mars. The great distances, the intense radiation levels, and the physiological response to zero gravity all support the concept of using a nuclear rocket to decrease mission time. These same needs have been recognized in later studies and, especially, in the Space Exploration Initiative in 1989. One of the key questions that has arisen in later studies, however, is the ability to test a nuclear rocket engine in the current societal environment. Unlike the Rover/Nuclear Engine for Rocket Vehicle Applications programs in the 1960s, the rocket exhaust can no longer be vented to the open atmosphere. As a consequence, previous studies have examined the feasibility of building a large-scale version of the Nuclear Furnace Scrubber that was demonstrated in 1971. We have investigated an alternative thatwoulddeposit the rocket exhaust alongwith anyentrained Ž ssion products directly into the ground. The subsurface active Ž ltering of exhaust concept would allow variable-sized engines to be tested for long times at a modest expense. A system overview, results of preliminary calculations, and current status of a proof-of-concept demonstration are presented.

TEMPERATURE MEASUREMENT OF SOLID ROCKET MOTOR EXHAUST PLUME BY ABSORPTION-EMISSION SPECTROSCOPY1*

A method, which measures the temperature of solid rocket motor exhaust plume, was developed by employing an improved sodium line reversal process. The formula for calculating the temperature was improved and simplified. The temporal temperature-time distributions of the exhaust plume of double base propellant rocket motors were given by the established method. The maximum time resolution and accuracy for the temperature measurement are 40 μs and 8%, respectively. This kind of temperature measurement does not disturb the combustion flow field of exhaust plume and is simpler and more sensitive. The maximum temperatures of SQ-2 propellant exhaust plumes are 2234 K and 2202 K for 240 mm and 500 mm apart from the motor nozzle, respectively. More combustion phenomena of the exhaust plume can be measured by using an existing instrument.

Mie light-scattering granulometer with an adaptive numerical filtering method II Experiments

A nephelometer is presented that theoretically requires no absolute calibration. This instrument is used for determining the particle-size distribution of various scattering media (aerosols, fogs, rocket exhausts, engine plumes, and the like) from angular static light-scattering measurements. An inverse procedure is used, which consists of a least-squares method and a regularization scheme based on numerical filtering. To retrieve the distribution function one matches the experimental data with theoretical patterns derived from Mie theory. The main principles of the inverse method are briefly presented, and the nephelometer is then described with the associated partial calibration procedure. Finally, the whole granulometer system (inverse method and nephelometer) is validated by comparison of measurements of scattering media with calibrated monodisperse or known size distribution functions.

H 2O and HCl adsorption on single crystal α-Al 2O 3(0001) at stratospheric temperatures

The adsorption of H 2O and HCl on single crystal α-Al 2O 3(0001) at stratospheric temperatures was studied using laser-induced thermal desorption (LITD) and temperature programmed desorption (TPD) techniques. The α-Al 2O 3(0001) surface was used to model stratospheric Al 2O 3 exhaust particles from solid rocket motors. H 2O and HCl coverages may influence heterogeneous chemistry on Al 2O 3 particles at stratospheric temperatures of ∼200–270 K. Compared with earlier measurements at 298–300 K, the saturation coverages of both H 2O and HCl on α-Al 2O 3(0001) were approximately two times higher at 210 K. The saturation coverages of H 2O and HCl at 210 K were Θ H 2O =4.4×10 14 molecules/cm 2 and Θ HCl=2.0×10 14 molecules/cm 2. The sticking coefficients for both H 2O and HCl on α-Al 2O 3(0001) at 210 K were also higher than the corresponding sticking coefficients at 298–300 K. The sticking coefficients (S) for both H 2O and HCl at 210 K were ∼0.08 at the lowest coverages. The TPD spectra revealed that H 2O and HCl desorption occurred over a broad range of temperatures. These results indicate that H 2O and HCl adsorb onto a wide distribution of binding sites on the α-Al 2O 3(0001) surface. The LITD and TPD results predict that α-Al 2O 3 rocket exhaust particles will be covered with chemisorbed H 2O and HCl under stratospheric conditions. Additional H 2O and HCl exposure can also replace the adsorbed HCl and H 2O species, respectively, by exchange reactions.

Computational Assessment of Afterburning Cessation Mechanisms in Fuel-Rich Rocket Exhaust Plumes

Abstract : A computational study was conducted to identify fundamental physical processes governing the cessation or shutdown of the afterburning of fuel rich rocket exhaust with the atmosphere. Several mechanisms were examined which are: 1) a relaminarization phenomenon, 2) a Damkohler number effect and 3) a classical flame extinction mechanism. Analysis of the simulation results revealed the relaminarization mechanism to be implausible while the Damkohler number effect and the flame extinction mechanisms were found to be valid. The extinction mechanism was also found to dramatically alter the emission characteristics and enhance the shutdown behavior which has important implications with respect to radiative heat transfer to the body and missile defense systems. This is a significant finding because strain rate induced extinction is a previously unrecognized phenomena occurring in rocket exhaust plumes during afterburning cessation.

Non-Intrusive measurements of aircraft and rocket exhaust emissions

Abstract On ground measurements of aircraft exhaust emissions will increasingly be needed to support environmental protection and regulatory measures. This paper describes research into methods of measurement which can be applied in field conditions and which do not require intrusion into the engines being measured.

Mie light-scattering granulometer with adaptive numerical filtering I Theory

A search procedure based on a least-squares method including a regularization scheme constructed from numerical filtering is presented. This method, with the addition of a nephelometer, can be used to determine the particle-size distributions of various scattering media (aerosols, fogs, rocket exhausts, motor plumes) from angular static light-scattering measurements. For retrieval of the distribution function, the experimental data are matched with theoretical patterns derived from Mie theory. The method is numerically investigated with simulated data, and the performance of the inverse procedure is evaluated. The results show that the retrieved distribution function is quite reliable, even for strong levels of noise.

In-situ aerosol emissions characterization in rocket exhaust plumes during projects riso and accent

In-situ aerosol emissions characterization in rocket exhaust plumes during projects riso and accent

Adsorption and desorption of HCl on a single-crystal α-Al 2O 3(0001) surface

The adsorption and desorption of HCl on a single-crystal α-Al 2O 3(0001) surface were examined using laser-induced thermal desorption (LITD) and temperature-programmed desorption (TPD) techniques. α-Al 2O 3(0001) is a model for the surface of Al 2O 3 exhaust particles generated by solid rocket motors. HCl adsorption on these Al 2O 3 particles may alter the surface reactivity and affect heterogeneous atmospheric chemistry. Absolute HCl surface coverages on α-Al 2O 3(0001) were determined using calibrated HCl LITD signals. The reactive sticking coefficient for HCl adsorption on α-Al 2O 3(0001) at 298 K was S∼10 −3 at the lowest HCl coverages. The HCl reactive sticking coefficient decreased nearly exponentially with HCl coverage. The HCl coverage saturated at Θ HCl=1.0×10 14 molecules cm −2 after HCl exposures of >2×10 9 L. HCl desorption from the α-Al 2O 3(0001) surface occurred over a wide temperature range from 300 to 650 K. This broad temperature range suggests a distribution of surface sites with different binding energies. HCl desorption was investigated versus HCl coverage by annealing an α-Al 2O 3(0001) surface that was previously saturated by a large HCl exposure. These results confirmed a wide range of binding energies and suggested that surface diffusion between the adsorption sites must be negligible. Additional HCl desorption results versus HCl coverage, prepared by varying the HCl exposure, revealed that HCl adsorption randomly fills the adsorption sites independent of their binding energies. Modeling of the HCl desorption results was consistent with surface binding energies that ranged from 19 to 36 kcal mol −1. These adsorption and desorption results predict that α-Al 2O 3 rocket exhaust particles will be partially covered with a stable HCl adlayer at stratospheric temperatures and pressures.

Measurements of stratospheric plume dispersion by imagery of solid rocket motor exhaust

Plume expansion from nine space shuttle and Titan IV vehicles was measured at altitudes of 18, 24, and 30 km in the stratosphere. The plume diameters, inferred from electronic images of polarized, near‐infrared solar radiation scattered from the exhaust particles, increased linearly with time. The expansion rate was measured for as long as 50 min. Observations made simultaneously at multiple altitudes showed that the expansion rate increased with increasing altitude for six measurements made at Cape Canaveral but decreased between 24 and 30 km for the one measurement made at Vandenberg Air Force Base. The average expansion rates for all measurements are 4.3±1.0 m s−1 at 18 km, 6.8±1.9 m s−1 at 24 km, and 8.7±2.4 m s−1 at 30 km. Expansion rates varied from launch to launch by as much as a factor of 1.6 at 18 km, 2.2 at 24 km, and 2.6 at 30 km. No correlation between the expansion rate and wind speed or wind shear was evident. These data are compared with several models for diffusivity and are used to update a comprehensive particle model of solid rocket motor exhaust in the stratosphere. The expansion rates are required by models to calculate the spatial extent and temporal persistence of the local stratospheric ozone depletion cause by solid rocket exhaust.

Numerical Study of Shock-Reflection Hysteresis in an Underexpanded Jet

Shock-ree ection hysteresis and plume structure in a low-density, axisymmetric highly underexpanded air jet is examined using a Navier ‐Stokes e ow solver. This type of jet is found in a number of applications, e.g., rocket exhausts and fuel injectors. The plume structure is complex, involving the interaction of several e ow features, making this a demanding problem. Two types of shock ree ection appear to occur in the plume, regular and Mach, depending on the jet pressure ratio. The existence of a dual solution domain where either type may occur has been predicted, in agreement with experiment where the same phenomenon has been observed for a nitrogen jet. There is a hysteresis in the shock-ree ection type; the ree ection type observed in the dual-solution domain depends on the time history of the plume development. A quasi-steady approach is employed to calculate the entire hysteresis loop. An implicit, multiblock structured, e nite volume e ow solver is used. The results of the computational study are used to examine the structure of the plume and are compared with experimental data where possible. Some e ow features not initially recognized from experiment have been identie ed, notably curvature of the Mach disk, recirculation behind the Mach disk, and the regular ree ection having Mach-ree ection characteristics.

Airborne mass spectrometers: four decades of atmospheric and space research at the Air Force research laboratory.

Mass spectrometry is a versatile research tool that has proved to be extremely useful for exploring the fundamental nature of the earth's atmosphere and ionosphere and in helping to solve operational problems facing the Air Force and the Department of Defense. In the past 40 years, our research group at the Air Force Research Laboratory has flown quadrupole mass spectrometers of many designs on nearly 100 sounding rockets, nine satellites, three Space Shuttles and many missions of high-altitude research aircraft and balloons. We have also used our instruments in ground-based investigations of rocket and jet engine exhaust, combustion chemistry and microwave breakdown chemistry. This paper is a review of the instrumentation and techniques needed for space research, a summary of the results from many of the experiments, and an introduction to the broad field of atmospheric and space mass spectrometry in general.

Study blazing new trails into effects of aviation and rocket exhaust in the atmosphere

A new study may help resolve uncertainties in the impact of aviation and rocket exhaust on the atmosphere. Results of the project are expected to serve the aviation and rocket communities in their propulsion system choices and fleet operations in the 21st century. The study, known as the Atmospheric Chemistry of Combustion Emissions near the Tropopause (ACCENT) project, follows the lead of two other programs motivated by continuing concern over the impact such emissions are having on upper troposphere and lower stratosphere (UT/LS) ozone and climate. ACCENT in effect combines those two programs, one of which concerns aviation, the other rockets.

Water on the Sun: The Sun yields more secrets to spectroscopy

Analysis of sunlight, which started the discipline of spectroscopy, has been the key to a number of major scientific discoveries. Sunspots, which are much cooler than most of the Sun's surface, have particularly rich and complicated spectra which has long been thought to be due to very hot water. The challenge of analysing this spectrum has stimulated the development of new theoretical procedures based on full quantum mechanical treatments of the vibrational and rotational motion of the water molecule. The result has been the identification of novel spectral features and a deeper understanding of how excited molecules such as superheated water behave. This work has applications ranging from the models of cool star atmospheres and rocket exhausts to the possible automated detection of forest fires. Perhaps the most interesting result is the insight given to understanding how our own atmosphere absorbs sunlight, and the possible consequences that this may have for modelling the greenhouse effect.

Evaluation of the performance of supersonic exhaust diffuser using scaled down models

Experiments were carried out on straight cylindrical supersonic exhaust diffusers (SED) using cold nitrogen and hot rocket exhaust gases as driving fluids, in order to evaluate the effects of the ratios of the SED area to rocket nozzle throat area ( A d/ A t), SED area to rocket nozzle exit area ( A d/ A e), SED length to its diameter ( L/ D) and specific heat ratio of the driving gases ( k) on the minimum starting pressure ratio, ( P o/ P a)st, of SED. The rocket nozzle and SED starting transients were also simulated in the models. The study reveals that ( P o/ P a)st increases monotonically with increase in ( A d/ A t) and k. One-dimensional normal shock relations were used in predicting the ( P o/ P a)st since the compression in long ducts is basically a normal shock process. Predicted values of ( P o/ P a)st were validated with experimental data. SED efficiency factors( η ns) were arrived at based on one-dimensional normal shock relations. η ns goes down at higher values of ( A d/ A e). ( P o/ P a)st is lower for lower k values for the same ( A d/ A t). Cylindrical SEDs exhibit no hysteresis. The results of this investigation were utilised in validating the design of high altitude test (HAT) facility for testing the third stage motor (PS-3) of Polar Satellite Launch Vehicle (PSLV). The simulation of starting transients in the model revealed that the HAT facility shall not be operated in the unstarted phase, because the rocket nozzle may fail due to violent oscillations of the vacuum chamber pressure. These experimental data were also utilised for designing a SED for PS-3 sub-scale motor, the results of which are covered in this paper. The accuracy of measurements are within a range of ±0.4%. Error analysis of the data were carried out and are presented in Appendix A.

NICROFER 7016 TiNb

Abstract Nicrofer 7016 TiNb is an austenitic age-hardening Ni-Cr-Fe alloy containing Ti, Nb, and Al. High tensile strength is combined with good weldability. This aerospace alloy finds applications in rocket exhaust heat exchangers, springs, bellows, and bolts. This datasheet provides information on composition, physical properties, microstructure, elasticity, and tensile properties as well as creep. It also includes information on high temperature performance as well as forming, heat treating, machining, and joining. Filing Code: Ni-534. Producer or source: VDM Technologies Corporation.

Observation of stratospheric ozone depletion in rocket exhaust plumes

Although modelling studies have predicted1,2,3,4,5,6,7 that particulate and reactive gas-phase species in the exhaust plume of large rockets might cause significant local ozone depletion, the actual response of the stratosphere after rocket launches has never been directly determined. Here we report comprehensive measurements that follow the evolution of stratospheric ozone in the wake of two Titan IV rockets launched on 12 May and 20 December 1996. In both cases, ozone concentrations dropped to near-zero values in the plume wake, across regions four to eight kilometres wide, within 30 minutes after launch; intense ozone loss persisted for 30 minutes after which time concentrations recovered to ambient levels. Our data indicate that the number of ozone molecules lost in the plume regions significantly exceed the number of chlorine molecules deposited by the two rockets. This suggests that a catalytic cycle based on Cl2O2, other than Cl2, and unique to solid rocket motor (SRM) plumes might be responsible for our observations. However, the limited spatial and temporal extent of the observed ozone losses implies that neither the catalytic Cl2O2 cycle nor other reactions involving exhaust compounds from large solid-fuelled rockets have a globally significant impact on stratospheric chemistry.

A random simulation of droplet distribution in nozzle and plume flows

A simple entrainment model is used to estimate droplet streamlines, velocity and mass flux in rocket exhaust plumes. Since droplet mass flux constitutes only about 1% of the exhaust mass flux, the effect of droplet entrainment on the gas flow is neglected. The novelty of the present model is in obtaining the droplet distribution within the nozzle by assuming a small radial random velocity component for droplets at the throat. Gas flow in the nozzle is approximated as isentropic plus a correction for the boundary layer. The computed distribution of droplet mass flux is found to be in good agreement with experimental data.

In‐situ measurement of Cl2 and O3 in a stratospheric solid rocket motor exhaust plume

The concentration of Cl2 in the stratospheric exhaust plume of a Titan IV launch vehicle was measured with a neutral mass spectrometer carried on a WB‐57F aircraft at 18.9 km altitude. Twenty nine minutes after a twilight Titan IV launch, the mean Cl2 concentration across an 8 km wide plume was 126 ± 44 ppbv, consistent with model predictions that a large fraction of the HCl in solid rocket motor exhaust is converted into Cl2 by afterburning reactions in the hot plume. Co‐incident measurements with ultraviolet absorption photometers also carried on the aircraft show that ozone concentration in the plume was not different from ambient levels. This is consistent with model predictions that nighttime SRM launches will not cause transient ozone loss in the lower stratosphere. The measured Cl2 concentration equals 15% of the ambient ozone concentration suggesting that transient ozone reduction in SRM plume wakes can be expected after daytime launches when solar ultraviolet radiation will photolyze the exhaust plume Cl2.

Radiation Emitted from Rocket Plumes

AbstractThe signature of rocket plumes can be used for detection, identification and guidance of rockets. The objective was to investigate the signature of various types of solid rocket propellants by application of spectroscopic methods. The emission and transmission characteristics of plumes were studied experimentally, the results were analyzed based on molecular bands and continuum radiation. The model formulations include a nitramine propellant, a double‐base propellant and a composite propellant. Applied were rapid‐scanning filter wheel spectrometers for the wavelength region from 1.2 μm to 14 μm with a time resolution of 50 spectra/s and a wavelengths resolution of 1% of actual wavelength. The UV/VIS wavelengths region was recorded by an OMA system with wavelength resolution of 0.1 nm and 1 nm and time resolution of 10 spectra/s. Molecular bands of water and carbon dioxide dominate in the near infrared and infrared. Depending on composition, continuous radiation indicates particles in the rocket exhaust. A code was developed to calculate molecular bands and continuous radiation using temperature and species distributions found by thermodynamic estimation to obtain the radiance of the plume. Comparison with experimental data delivered plume temperatures.