Showing papers on "Rocket published in 1978"

Auroral electron distribution function

Abstract: During a rocket flight over an active aurora, electron velocity distribution is studied in the 15-25 keV range. The results are then compared to optical observations made by all-sky cameras and a television system. A broad plateau produced by downcoming electrons was observed. Smaller plateaus were seen when the rocket was south of arcs evident in all-sky camera photographs. By extending to higher energies when the rocket passed out of auroral forms, the plateaus appeared to broaden. When the rocket left an arc or entered weak diffuse auroral structures, the plateaus shrank as the more energetic portions faded. When field-aligned rays were observed within the arcs, the plateau's high-velocity cutoff was found to fluctuate. The results indicate that the auroral plasma was very unstable above the rocket. It is suggested that plateaus are produced as an unstable plasma evolves toward a quasi-equilibrium state.

Heating of the ambient ionosphere by an artificially injected electron beam

Abstract: An electrostatic analyzer on the electron accelerator of the Electron Echo 2 experiment showed that the electrons of the background plasma were heated to 10,000 K or more within 8 ms of the start of gun pulses. The degree of heating was dependent on the orientation of the rocket with respect to the magnetic field but was not measurably dependent on ambient electron density, neutral atmosphere density, or on the pitch angle at which the 40-keV electron beam was injected. This heating was also accompanied by an increase of plasma density. No evidence was found for an ion-free region around the rocket during gun pulses. These observations show that significant amounts of ionization are taking place around the rocket. During part of the flight a two-temperature electron distribution was found. It is believed that the high-temperature part of these distributions represents secondaries produced by the beam.

Rocket observation of high frequency waves over a strong aurora

Abstract: High frequency waves in two frequency bands above the electron gyro frequency (1.6 MHz and 2.3 MHz) were observed by radio receivers carried on a sounding rocket as it passed over a strong aurora. Only the line at 2.3 MHz has a large magnetic component. Both 0.4s and 4s periods are present in much of the emissions. Good correlation is seen for a short time between the 2.3 MHz waves and 1.9 keV electrons detected on board the rocket.

Aerodynamic control mechanism for thrust vector control

Abstract: A rocket thrust vector control system including jet tabs and aerodynamic control surfaces is disclosed The control system removes roll information present in commands to the aerodynamic surfaces and provides only pitch and yaw information to the jet tabs for the thrust vector control The roll information is removed by a geared summing mechanism The resulting pitch and yaw output is used to drive the thrust vector control jet tabs The same powered actuators are used for both the aerodynamic control surfaces and the jet tabs

Environmental effects of the Space Shuttle

Abstract: Rocket exhaust products, acoustic noise, and a sonic boom are produced during launch of the Space Shuttle. Their environmental effects have been assessed and found to be small and transient, or controllable by the choice of launch azimuth or launch conditions. Reentry of the Orbiter will produce a very low-level sonic boom over populated areas.

Ground observations of waves at 2.96 MHz generated by an 8‐ to 40‐keV electron beam in the ionosphere

Abstract: Electromagnetic waves at 2.96 MHz, associated with a beam of 8- to 40-keV electrons in the ionosphere, were observed during the Electron Echo 4 rocket experiment in January 1976. Over 1000 electron pulses were emitted during the rocket experiment, and about 20% of these produced observable signals on the ground. Waves were generated under three different sets of conditions. One set of conditions led to maximum amplitude at 190 km; 2.96 MHz is the second harmonic of the electron cyclotron frequency at an altitude of 160–170 km, so the frequency was about 1% above the local gyrofrequency at the rocket. The second set of conditions led to peak signal amplitude in the 110- to 130-km range, at twice the relativistic cyclotron frequency of the 8- to 16-keV beam. The third set of conditions required that the beam be fired downward. Observations were also made at 0.161, 1.11, 1.25, 1.39, and 5.73 MHz, but no signals were detected at those frequencies.

Rocket effluent: Its ice nucleation activity and related properties

Abstract: To investigate the possibility of inadvertent weather modification from rocket effluent, aerosol samples were collected from an instrumented aircraft subsequent to the Voyager 1 and 2 launches. The aerosol's morphology, concentration, and size distribution were examined with an electron microscope. The elemental compositions of individual particles were analyzed with an X-ray energy spectrometer. Ice nucleus concentration was measured with a thermal diffusion chamber. The particles' physical and chemical properties were related to their ice nucleation activity. A laboratory experiment on rocket propellant exhaust was conducted under controlled conditions. Both laboratory and field experimental results indicated that rocket propellant exhaust can produce active ice nuclei and modify local weather in suitable meteorological conditions.

Convective Burning in Solid-Propellant Cracks

Abstract: Transient combustion processes inside solid-propellant cracks can significantly affect the performance of a rocket motor. A comprehensive theoretical model has been developed to study the gas dynamics, heat transfer, and flame spreading phenomena within a single isolated crack. Calculations obtained from the theoretical mode! revealed that the infernal pressurization rate, pressure gradient, and flame propagation velocity in propellant cracks decrease as the gap width increases, the rocket chamber pressurization rate decreases, and the propellant gasification temperature increases. Additionally, the predicted flame spreading was found to decelerate in a region near the crack tip; this phenomena has been experimentally observed by others. A laboratory-size combustion chamber has been designed to establish a fundamental data base in propellant crack combustion and to verify the predicative capability of the theoretical model. Preliminary experimental data, obtained in wide cracks ( — 0.1 cm) for relatively low chamber pressurization rates, closely compares with theoretical predictions.

Rotating Valve for Velocity Coupled Combustion Response Measurements.

Abstract: : Coupling between the combustion process and the acoustics of the combustion chamber are important factors determining combustion stability of a solid propellant rocket. This coupling results from the response of the combustion process to both the local acoustic pressure and the local acoustic velocity. Because of the complexity of both processes, they cannot be totally characterized analytically; therefore, laboratory test data are needed in making analytical combustion stability predictions. Analytical studies accomplished under this contract have developed a mathematical analysis of the transient ballistics. The solution of the transient mass, momentum, and energy equations incorporates both linear and nonlinear velocity coupling, as well as pressure coupling, particle damping, flow turning, and nozzle losses in the analysis. The analysis shows that velocity coupling dominates the system response when the two valves operate 180 deg. out of phase. Combustion tests were conducted using two nonaluminized propellants. Analysis of the data, using the linear velocity response model, indicates the imaginary part of the response increases from approximately -10 at 150 Hz to approximately 1.6 at 570 Hz. Amplitude spectrum analyses of the pressure traces show significant harmonic content. Since the area wave form contains very low harmonic content, this suggests the nonlinear velocity coupling may provide a more realistic framework for data interpretation. Combustion tests were also conducted with a formulation containing 21% aluminum. With the exception of one slot insert, the apparatus operated satisfactorily.

Electron flux and auroral intensity measurements in situ

Abstract: A rocket (ADD-II-128) launched into bright aurora at Churchill, Canada on February 21, 1974 provided in situ measurements of electron influx and resulting 5577A emission intensity. The rocket descended through a broad and fairly homogeneous arc of 70 kR intensity. Measurements of downward electron energy flux (18 keV-20 eV) at the rocket during the time it descended from 120 to 110 km were compared with resulting emission intensities directly below the rocket. They yielded excitation efficiencies of 0.67 kR of 5577A OI and 180R of 4278A N2+ per erg/cm² sec energy influx. These values agree well with calculated values for bright auroras.

Uniform distribution of BeO particles in Be casting produced in rocket free fall

Abstract: An experiment at zero-g aboard a NASA sounding rocket was conducted to evaluate the distribution of BeO particles in a Be casting. A distinction is drawn between the downward settling of particles in a quiescent melt, and the velocity gradient collisions of particles in a melt agitated by electromagnetic stirring. A similar experiment was conducted on earth using the same melting and solidification of a 0.922 cm spheroid of HIP-50 as was carried out in space; the only difference arising from the effect of gravity. Under zero-g conditions, the time needed for agglomeration was lengthened considerably, but the result was a casting of more uniform particle distribution.

Rocket effluent size distributions made with a cascade quartz crystal microbalance

Abstract: Airborne particulate size distribution measurements were made in the stabilized ground cloud from a Titan III C rocket just after launch from the Kennedy Space Center on May 12, 1977. The measurements were made from aboard a small twin engine aircraft instrumented with particle and gas sensors. The plume was followed for about 1 hour while making multiple passes through the cloud at varying altitudes. The results obtained with a ten-stage cascade quartz crystal microbalance impactor show that the mass concentration as a function of particle diameter is bimodal with the first maximum between 0.05 micrometers and 0.1 micrometers and the second maximum between 0.8 and 1.0 micrometer. Scanning electron microscope analysis were performed on the material collected and show distinctly different kinds of particles in the two modes.

Rocket detent and release mechanism

Abstract: A rocket detent and release mechanism which restrains a rocket in a launchube during transportation of the launch tube and rocket mounted on a transporting vehicle; the detent and release mechanism is of such structure as to be released on ignition of a rocket motor of the rocket to allow the rocket to be launched, and the detent and release mechanism is fabricated and mounted such that no tools are required for engaging the detent and release mechanism when mounting the rocket in the launch tube.

A determination of F region convective electric fields from rocket measurements of ionospheric thermal ion spectra

Abstract: A detector package designed to measure the bulk flow of heavy ions was developed for sounding rocket studies of the lower ionosphere. The unit was first flown on board Electron Echo 3, which was launched eastward from Poker Flat Research Range on April 17, 1974. From least squares fits of a shifted, drifting Maxwellian distribution to direct measurements of the ionospheric particles' thermal energy spectra, average values of rocket payload potential, ion temperature, and bulk plasma flow were obtained. By interpreting the bulk flow velocity transverse to the local magnetic field as convective drift the strength of convective electric fields was inferred. Parameters determined from the data support an ion temperature of 1500 ± 94°K, a payload potential of 1.2 V, and convective field values of 6 ± 4 mV/m east and 25 ± 4 mV/m north. These values compare with an ion temperature of 1000°K, a northward field of 21 mV/m and an eastward field of O mV/m as measured by the auroral backscatter radar at Chatanika, Alaska. Results from the electron echo experiment are also consistent with these electric field values.

Attitude selective aircrew escape control

Abstract: A line cutter or discharge valve responsive to aircraft attitude is posited on an aircraft ejection seat to interrupt the gas initiated sustainer rocket system. During inverted ejections, the cutter or valve will either sever or discharge pressure from a tube which leads from the firing squib to the sustainer rocket. Preventing sustainer rocket ignition enhances inverted ejection survivability by reducing crew member velocity toward the ground, thereby lengthening the time available for parachute deployment.

Rocket launcher with inductive connection to rockets - includes seven parallel tubes of synthetic material surrounded by induction windings

Abstract: The rocket launcher includes an assembly of seven tubes (1) of glass fibre held together by an epoxy resin Primary inducting windings (2) are wound around these tubes to form an inductive link with secondary windings in the rockets The tubes are held in position in line by an upper girder (3) with mounting points (4) Blocks (6) fit in between the tubes to support them in their relative positions The girder and blocks are made of a light alloy Tie rods (7) connect together the front (8) conical portion and the rear flat part of the launcher, with these parts also being made of light alloy A thin sleeve (13) encloses the whole assembly The terminal (14) connects the rocket launcher to the firing control, and firing contacts (16) connect the rocket launcher to each of the rockets The casing (5) includes interface circuitry linking these two terminals

Shock suppressing apparatus and method for a rocket launcher

Abstract: A shock suppressing device adapted to be attached to the aft end of a shoulder-fired rocket launcher. The device comprises a cylindrical housing defining a substantially enclosed expansion chamber having a diameter and cross-sectional area greater than that of the exhaust end of the launch tube. A plurality of annular baffles extend radially inwardly from the cylindrical housing and define aligned through openings through which a plug from a rocket being launched can be emitted rearwardly from the launch tube. The initial shock which follows the expulsion of the plug from the rocket is spread outwardly into the expansion chamber to engage the baffles therein. The baffles suppress the shock by absorbing a substantial portion of the energy of the shock wave, and also partially reflecting the shock wave in an upstream direction toward the launch tube. In the preferred form, the housing is made of several members which telescope together for storage, and are pulled out to an expanded position for use.

Hypervelocity rocket system with velocity amplifier

Abstract: A hypervelocity rocket system with velocity amplifier including a launch e with a projectile mounted therein by sabot means and a rocket motor with an energy absorber at one end and mounted in the launch tube for impacting the projectile and causing velocity amplification of the projectile through momentum transfer as it is propelled from the launch tube.

Rocket exhaust plume impingement on the Voyager spacecraft

Abstract: In connection with the conduction of the long-duration Voyager missions to the outer planets and the sophisticated propulsion systems required, it was necessary to carry out an investigation to avoid exhaust plume impingement problems. The rarefied gas dynamics literature indicates that, for most engineering surfaces, the assumption of diffuse reemission and complete thermal accommodation is warranted in the free molecular flow regime. This assumption was applied to an analysis of a spacecraft plume impingement problem in the near-free molecular flow regime and yielded results to within a few percent of flight data. The importance of a correct treatment of the surface temperature was also demonstrated. Specular reflection, on the other hand, was shown to yield results which may be unconservative by a factor of 2 or 3. It is pointed out that one of the most difficult portions of an exhaust plume impingement analysis is the simulation of the impinged hardware. The geometry involved must be described as accurately and completely as possible.

Free-Flight Rocket's Initial Trajectory as Affected by Massive Blowby

Abstract: An experimental program has been conducted to determine the unbalanced forces on a tube-launched rocket due to the choking and the subsequent reversal (or blowby) of the exhaust flow. An underexpanded jet of unheated air was exhausted into a nontipoff launch tube. The surface of the simulated rocket was instrumented with static pressure orifices, located in diametrically opposed pairs. The differential pressure measurements were used to compute the rocket's trajectory in a three-degree-of-freedom program. Relatively large asymmetric pressure differentials were measured on the surface of the simulated rocket. Although the lateral displacement of the rocket was relatively insensitive to these pressure differentials, they caused large, oscillatory variations in the pitch angle and in the pitch rate.

Optimal flight paths for a winged supersonic rocket vehicle

Abstract: In 1951, Tsien and Evans successfully solved the problem of finding the optimum flight path for a vertically ascending sounding rocket (Ref. 1). Hibbs, in 1952, solved the problem of finding the optimum burning program for horizontal flight of a winged, rocket-propelled vehicle (Ref. 2). Since then work on optimal flight paths within the atmosphere has stagnated, most work being done for constant thrust, programmed in angle, in vacuo. The present work extends Tsien and Evans', and Hibbs' work, to flight paths off the vertical. Although the simpler paths produced analytical solutions in the time domain, the present solution is not analytic and is carried out numerically using distance or path length as the independent variable.