Compilation of rocket spin data. Volume 3 - Data evaluation and recommendations Final report, Nov. 1964 - Aug. 1968
Qualitative analysis of spin acceleration effects on solid propellant rocket engine performance
Manda, L. J.↗
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Response of mouse epidermal cells to single doses of heavy-particles
The survival of mouse epidermal cells to heavy-particles has been studied In Vivo by the Withers clone technique. Experiments with accelerated helium, lithium and carbon ions were performed. The survival curve for the helium ion irradiations used a modified Bragg curve method with a maximum tissue penetration of 465 microns, and indicated that the dose needed to reduce the original cell number to 1 surviving cell/square centimeters was 1525 rads with a D sub o of 95 rads. The LET at the basal cell layer was 28.6 keV per micron. Preliminary experiments with lithium and carbon used treatment doses of 1250 rads with LET's at the surface of the skin of 56 and 193 keV per micron respectively. Penetration depths in skin were 350 and 530 microns for the carbon and lithium ions whose Bragg curves were unmodified. Results indicate a maximum RBE for skin of about 2 using the skin cloning technique. An attempt has been made to relate the epidermal cell survival curve to mortality of the whole animal for helium ions.
Leith, J. T.↗
Remote control circuit breaker evaluation testing
Engineering evaluation tests were performed on several models/types of remote control circuit breakers marketed in an attempt to gain some insight into their potential suitability for use on the space shuttle vehicle. Tests included the measurement of several electrical and operational performance parameters under laboratory ambient, space simulation, acceleration and vibration environmental conditions.
Bemko, L. M.↗
Performance documentation of the engineering model 30-cm diameter thruster
The results of extensive testing of two 30-cm ion thrusters which are virtually identical to the 900 series Engineering Model Thruster in an ongoing 15,000-hour life test are presented. Performance data for the nominal fullpower (2650 W) operating point; performance sensitivities to discharge voltage, discharge losses, accelerator voltage, and magnetic baffle current; and several power throttling techniques (maximum Isp, maximum thrust/power ratio, and two cases in between are included). Criteria for throttling are specified in terms of the screen power supply envelope, thruster operating limits, and control stability. In addition, reduced requirements for successful high voltage recycles are presented.
Bechtel, R. T.↗
Modularized ion thruster
A modularized ion thruster system was developed for space-propulsion applications. Separate discharge chamber modules (DCMs) were optimized for operation at the thrust levels of T = 0.5 mlb and T = 2 mlb to accommodate the extended thrust range. These optimizations included modifications in the discharge-chamber components and the incorporation of ion machined accelerators in the beam-extraction systems. Performance of the optimized modules are summarized.
Hyman, J., Jr.↗
Performance documentation of the Engineering Model 30 cm diameter Thruster
Presented are the results of extensive testing of two 30-cm ion thrusters which are virtually identical to the 900 series Engineering Model Thruster in an ongoing 15,000-hour life test. Included are performance data for the nominal full-power (2650 W) operating point; performance sensitivities to discharge voltage, discharge losses, accelerator voltage, and magnetic baffle current; and several power throttling techniques (maximum Isp, maximum thrust/power ratio, and two cases in between). Criteria for throttling are specified in terms of the screen power supply envelope, thruster operating limits, and control stability. In addition, reduced requirements for successful high voltage recycles are presented.
Bechtel, R. T.↗
A Costas loop with tangent error signal for use in Navstar GPS avionics
This paper describes an augmented Costas loop for use in low-cost avionics for the Navstar Global Positioning System. A standard loop has been augmented with supplementing feed-back to give a tracking error voltage proportional to the tangent of the phase error, rather than to the sine. The augmented loop yields increased performance in the presence of input phase acceleration and jerk, as caused by maneuvers of the GPS user vehicle. Many Monte Carlo simulation results are given.
Painter, J. H.↗
Experimental investigation of a variable speed constant frequency electric generating system from a utility perspective
As efforts are accelerated to improve the overall capability and performance of wind electric systems, increased attention to variable speed configurations has developed. A number of potentially viable configurations have emerged. Various attributes of variable speed systems need to be carefully tested to evaluate their performance from the utility points of view. With this purpose, the NASA experimental variable speed constant frequency (VSCF) system has been tested. In order to determine the usefulness of these systems in utility applications, tests are required to resolve issues fundamental to electric utility systems. Legitimate questions exist regarding how variable speed generators will influence the performance of electric utility systems; therefore, tests from a utility perspective, have been performed on the VSCF system and an induction generator at an operating power level of 30 kW on a system rated at 200 kVA and 0.8 power factor.
Herrera, J. I.↗
Piloted-simulation evaluation of escape guidance for microburst wind shear encounters
Numerous air carrier accidents and incidents result from encounters with the atmospheric wind shear associated with microburst phenomena, in some cases resulting in heavy loss of life. An important issue in current wind shear research is how to best manage aircraft performance during an inadvertent wind shear encounter. The goals of this study were to: (1) develop techniques and guidance for maximizing an aircraft's ability to recover from microburst encounters following takeoff, (2) develop an understanding of how theoretical predictions of wind shear recovery performance might be achieved in actual use, and (3) gain insight into the piloting factors associated with recovery from microburst encounters. Three recovery strategies were implemented and tested in piloted simulation. Results show that a recovery strategy based on flying a flight path angle schedule produces improved performance over constant pitch attitude or acceleration-based recovery techniques. The best recovery technique was initially counterintuitive to the pilots who participated in the study. Evidence was found to indicate that the techniques required for flight through the turbulent vortex of a microburst may differ from the techniques being developed using classical, nonturbulent microburst models.
Hinton, David A.↗
Experiments with simplified computed-torque controllers for free-flying robots
The effect of neglecting base accelerations in an inertial space endpoint computed-torque (CT) controller is examined. Numerical simulations predict a rather wide set of conditions under which CT controllers can neglect base accelerations in their dynamic model with insignificant performance degradation. Two predictions are experimentally verified with a laboratory robot. These two experiments show that negligible additional endpoint controller error results with a simplified CT controller for the given robot mass parameters and manipulator articulation.
Koningstein, R.↗
Optimal active vibration absorber: Design and experimental results
An optimal active vibration absorber can provide guaranteed closed-loop stability and control for large flexible space structures with collocated sensors/actuators. The active vibration absorber is a second-order dynamic system which is designed to suppress any unwanted structural vibration. This can be designed with minimum knowledge of the controlled system. Two methods for optimizing the active vibration absorber parameters are illustrated: minimum resonant amplitude and frequency matched active controllers. The Controls-Structures Interaction Phase-1 Evolutionary Model at NASA LaRC is used to demonstrate the effectiveness of the active vibration absorber for vibration suppression. Performance is compared numerically and experimentally using acceleration feedback.
Lee-Glauser, Gina↗
Optimal active vibration absorber - Design and experimental results
An optimal active vibration absorber can provide guaranteed closed-loop stability and control for large flexible space structures with collocated sensors/actuators. The active vibration absorber is a second-order dynamic system which is designed to suppress any unwanted structural vibration. This can be designed with minimum knowledge of the controlled system. Two methods for optimizing the active vibration absorber parameters are illustrated: minimum resonant amplitude and frequency matched active controllers. The Controls-Structures Interaction Phase-1 Evolutionary Model at NASA LaRC is used to demonstrate the effectiveness of the active vibration absorber for vibration suppression. Performance is compared numerically and experimentally using acceleration feedback.
Lee-Glauser, Gina↗
Experimental investigation of nozzle/plume aerodynamics at hypersonic speeds
Much of the work involved the Ames 16-Inch Shock Tunnel facility. The facility was reactivated and upgraded, a data acquisition system was configured and upgraded several times, several facility calibrations were performed and test entries with a wedge model with hydrogen injection and a full scramjet combustor model, with hydrogen injection, were performed. Extensive CFD modeling of the flow in the facility was done. This includes modeling of the unsteady flow in the driver and driven tubes and steady flow modeling of the nozzle flow. Other modeling efforts include simulations of non-equilibrium flows and turbulence, plasmas, light gas guns and the use of non-ideal gas equations of state. New experimental techniques to improve the performance of gas guns, shock tubes and tunnels and scramjet combustors were conceived and studied computationally. Ways to improve scramjet engine performance using steady and pulsed detonation waves were also studied computationally. A number of studies were performed on the operation of the ram accelerator, including investigations of in-tube gasdynamic heating and the use of high explosives to raise the velocity capability of the device.
Bogdanoff, David W.↗
Flight Stability and Control and Performance Results from the Linear Aerospike SR-71 Experiment (LASRE)
The Linear Aerospike SR-71 Experiment (LASRE) is presently being conducted to test a 20-percent-scale version of the Linear Aerospike rocket engine. This rocket engine has been chosen to power the X-33 Single Stage to Orbit Technology Demonstrator Vehicle. The rocket engine was integrated into a lifting body configuration and mounted to the upper surface of an SR-71 aircraft. This paper presents stability and control results and performance results from the envelope expansion flight tests of the LASRE configuration up to Mach 1.8 and compares the results with wind tunnel predictions. Longitudinal stability and elevator control effectiveness were well-predicted from wind tunnel tests. Zero-lift pitching moment was mispredicted transonically. Directional stability, dihedral stability, and rudder effectiveness were overpredicted. The SR-71 handling qualities were never significantly impacted as a result of the missed predictions. Performance results confirmed the large amount of wind-tunnel-predicted transonic drag for the LASRE configuration. This drag increase made the performance of the vehicle so poor that acceleration through transonic Mach numbers could not be achieved on a hot day without depleting the available fuel.
Moes, Timothy R.↗
Gravitational Acceleration Effects on Macrosegregation: Experiment and Computational Modeling
Experiments were performed under terrestrial gravity (1g) and during parabolic flights (10-2 g) to study the solidification and macrosegregation patterns of Al-Cu alloys. Alloys having 2% and 5% Cu were solidified against a chill at two different cooling rates. Microscopic and Electron Microprobe characterization was used to produce microstructural and macrosegregation maps. In all cases positive segregation occurred next to the chill because shrinkage flow, as expected. This positive segregation was higher in the low-g samples, apparently because of the higher heat transfer coefficient. A 2-D computational model was used to explain the experimental results. The continuum formulation was employed to describe the macroscopic transports of mass, energy, and momentum, associated with the solidification phenomena, for a two-phase system. The model considers that liquid flow is driven by thermal and solutal buoyancy, and by solidification shrinkage. The solidification event was divided into two stages. In the first one, the liquid containing freely moving equiaxed grains was described through the relative viscosity concept. In the second stage, when a fixed dendritic network was formed after dendritic coherency, the mushy zone was treated as a porous medium. The macrosegregation maps and the cooling curves obtained during experiments were used for validation of the solidification and segregation model. The model can explain the solidification and macrosegregation patterns and the differences between low- and high-gravity results.
Leon-Torres, J.↗
Growth of Solid Solution Single Crystals
The solidification of a solid solution semiconductor, having a wide separation between liquidus and solidus has been extensively studied in ground based, high magnetic field and Spacelab experiments. Two alloys of mercury cadmium telluride have been studied; with 80.0 mole percent of HgTe and 84.8 mole percent of HgTe respectively, the remainder being cadmium telluride. Such alloys are extremely difficult to grow by directional solidification on earth due to high solutal and thermal density differences that give rise to fluid flow and consequent loss of interface shape and composition. Diffusion controlled growth is therefore impossible to achieve in conventional directional solidification. The ground based experiments consisted of growing crystals in several different configurations of heat pipe furnaces, NASA's Advanced Automated Directional Solidification Furnace (AADSF), and a similar furnace incorporated in a superconducting magnet capable of operating at up to 5T. The first microgravity experiment took place during the flight of STS-62 in March 1994, with the AADSF installed on the second United States Microgravity Payload (USMP-2). The alloy was solidified at 3/4 inch per day over a 9 day period, and for the first time a detailed evaluation was performed correlating composition variations to measured residual acceleration. The second flight experiment took place in the fourth United States Microgravity Payload Mission (USMP-4) in November 1997. Due to contamination of the furnace system, analysis shows that the conditions prevailing during the experiment were quite different from the requirements requested prior to the mission. The results indicate that the sample did accomplish the desired objectives.
Lehoczky, Sandor L.↗
Environmental Physiology at the Johnson Space Center: Past, Present, and Future
This viewgraph presentation reviews the work in environmental physiology done at Johnson Space Center (JSC). The work is aimed at keeping astronauts healthy. This is a different approach than treating the sick, and is more of an occupational health model. The reduction of risks is the main emphasis for this work. They emphasis is to reduce the risk of decompression sickness (DCS) and acute mountain sickness (AMS). The work in environmental physiology encompasses the following areas: (1) Pressure: hypobaric and hyperbaric (2) Gases: hypoxia and hyperoxia, hypercapnia--closed space issues, inert gas physiology / respiration (3) Temperature: hypothermia and hyperthermia, thermal comfort, Protective clothing diving, aviation, mountaineering, and space (4) Acceleration (5) Noise and Vibration (6) Exercise / Performance (6) Acclimatization / Adaptation: engineering solutions when necessary. This presentation reviews the work done at JSC in the areas of DCS and AMS.
Conkin, Johnny↗
Neutron Imaging Camera
The Neutron Imaging Camera (NIC) is based on the Three-dimensional Track Imager (3DTI) technology developed at GSFC for gamma-ray astrophysics applications. The 3-DTI, a large volume time-projection chamber, provides accurate, approximately 0.4 mm resolution, 3-D tracking of charged particles. The incident direction of fast neutrons, En > 0.5 MeV, are reconstructed from the momenta and energies of the proton and triton fragments resulting from (sup 3)He(n,p) (sup 3)H interactions in the 3-DTI volume. The performance of the NIC from laboratory and accelerator tests is presented.
Hunter, Stanley↗