Skylab three-axis motion platform test results
Performance tests of three axis motion platform simulator for Skylab program
Borelli, M. T.↗
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Experiment M405: Tri-axis flux gate magnetometer
A tri-axis flux-gate magnetometer was used on four Gemini spacecraft for determination of the magnitude and direction of the local geomagnetic field with respect to the spacecraft. Conclusions derived from the data are not only important to the proton-electron spectrometer experiment, but also are of significance to any directional charged particle experiments that may be conducted. Even though the Gemini spacecraft was not clean magnetically, the data could be reduced to a form that supplied directional information on the magnetic field in relation to the spacecraft. Stray fields were the result of spacecraft structure, not the result of current flows that were produced within the spacecraft electrical systems. Efforts were made to reduce spacecraft stray fields and to facilitate the acquisition of more accurate data.
Womack, W. D.↗
Statistics concerning the Apollo command module water landing, including the probability of occurrence of various impact conditions, sucessful impact, and body X-axis loads
Statistical information for the Apollo command module water landings is presented. This information includes the probability of occurrence of various impact conditions, a successful impact, and body X-axis loads of various magnitudes.
Whitnah, A. M.↗
A single axis electrostatic beam deflection system for a 5-cm diameter ion thruster
A single-axis electrostatic beam deflection system has been tested on a 5-cm diameter mercury ion thruster at a thrust level of about 0.43 mlb (25 mA beam current at 1400 volts). The accelerator voltage was 500 volts. Beam deflection capability of plus or minus 10 deg was demonstrated. A life test of 1367 hours was run at the above conditions. Results of the test indicated that the system could possibly perform for upwards of 10,000 hours.
Lathem, W. C.↗
The relation of QRS amplitude to the frontal QRS axis and the heart-electrode distance.
The relation between QRS amplitude, QRS axis deviation and heart position was studied in 360 subjects, using the 12-lead EKG. The height of the V sub 6 R wave was used as the measure of QRS amplitude. The distance from the left lateral border of the heart was used to indicate heart position. The frontal and horizontal QRS axes were determined by noting the isoelectric limb and precordial leads, measured according to Schmitt's values.
Dougherty, J. D.↗
Response of a semi-infinite elastic solid to an arbitrary line load along the axis.
The axisymmetric problem of a line load acting along the axis of a semiinfinite elastic solid is solved using Hankel transforms. In this solution the line load is interpreted as a body force loading and by assuming the line load to be of the form of a Dirac delta function the solution of Mindlin's problem of a point load within the interior of the half space is obtained. Solutions of this problem presented in the literature have been obtained using semiinverse techniques whereas the solution given here is obtained in a systematic step-by-step manner.
Agrawal, G. L.↗
Human transinformation rates during one-to-four axis tracking with a concurrent audio task
The information processing rates of six subjects performing one-, two-, three-, and four-axis compensatory tracking tasks, with and without a concurrent four-choice auditory task were determined. The purpose was to obtain further evidence concerning the nature of an hypothesized ceiling on human transinformation rates. Interference was found among tasks, but the evidence concerning a ceiling on information processing rates was inconclusive.
Baty, D. L.↗
Development of a three axis fluidic airspeed sensor
A three axis fluidic airspeed sensor system has been fabricated and wind tunnel tested. The complete system consists of the fluidic sensor, air power supply and instrumentation and readout. The system is adapted to aircraft and requires only the standard aircraft 28V dc supply to function.
Neradka, V. F.↗
Lunar electromagnetic scattering. 1: Propagation parallel to the diamagnetic cavity axis
An analytic theory is developed for the time dependent magnetic fields inside the Moon and the diamagnetic cavity when the interplanetary electromagnetic field fluctuation propagates parallel to the cavity axis. The Moon model has an electrical conductivity which is an arbitrary function of radius. The lunar cavity is modelled by a nonconducting cylinder extending infinitely far downstream. For frequencies less than about 50 Hz, the cavity is a cylindrical waveguide below cutoff. Thus, cavity field perturbations due to the Moon do not propagate down the cavity, but are instead attenuated with distance downstream from the Moon.
Schwartz, K.↗
A laboratory simulation of a single-axis dual-level precision pointing system
The laboratory simulation of a scaled single-axis dual-level control system for a large space telescope is demonstrated. The dual-level control system consists of a coarse-body-pointing system and a fine-pointing system, which uses an image motion compensator, an image dissector tube, and digital electronics. The results of the simulation indicate that the dual-level system can be used to provide tracking capability within one-tenth of a diffraction-limited image diameter of a 3-meter f/100 telescope for stars up to a +12.3 visual magnitude.
Bullock, G. F.↗
Omni-axis secondary injection thrust vector control system
The concept, development, design study and preliminary analysis and layout of the required digital logic scheme to be used for injection valve control are presented. An application and optimization study of an Omni-Axis Secondary Injection Control System applicable to the proposed Space Shuttle Pressure Fed Engine is reported. Technical definition and analysis control procedures and test routines, as well as a supporting set of drawing sketches and reference manual, are enclosed.
Kirkley, D. J.↗
On the relationship between acoustic energy density flux near the jet axis and far field acoustic intensity
By measurement and analysis, the relationship between the distribution of the outflow of acoustic energy over the jet boundary and the far-field intensity is considered. The physical quantity used is the gradient of the pressure evaluated on a geometrical plane at the smallest possible radial distance from the jet axis, but outside the vortical region, in the area where the homogeneous wave equation is reasonably well satisfied. The numerical and experimental procedures involved have been checked out by using a known source. Results indicate that the acoustic power output per unit length of the jet, in the region from which the sound emanates, peaks at approximately 9 diameters downstream. The acoustic emission for a jet Strouhal number of about 0.3 exceeds the emission for all other Strouhal numbers nearly everywhere along the measurement plane. However, the far-field peak intensity distribution obtained from the contribution of each station was found to depend on the spatial extent of the region where sound emanates from the jet, which, in turn, depends more on the far-field angle than on the Strouhal number.
Maestrello, L.↗
Attitude control of a large flexible spacecraft using three-axis mass expulsion control.
A study of the elastic effects of large area solar arrays on attitude control of a spacecraft was conducted. It is demonstrated for sufficiently low structural frequencies that excitation of certain modes can induce instability in the pitch axis. Stiffening the arrays can eliminate the instability. However, a severe weight penalty is associated with such modification. A more efficient means of minimizing the structural interaction effects is to change the shape of the array. For stable configurations, another problem may be encountered. This is the imposition of high rates on the spacecraft bus by oscillation of the solar arrays. Since low rates are required to obtain accurate science experiment results, it is imperative that the high rate problem be resolved. This also is possible by changing the solar array configuration.
Marsh, E. L.↗
Lunar electromagnetic scattering. I - Propagation parallel to the diamagnetic cavity axis.
A general analytic solution is obtained for the interaction of the moon and its downstream cavity with a linearly polarized plane electromagnetic wave propagating parallel to the cavity axis. The solution is formulated in terms of a spherical moon model with arbitrary radially dependent electromagnetic parameters and a nonconducting cylindrical downstream cavity. Use is made of a number of approximations that are consistent with the physical nature of the interaction between the moon and the solar wind.
Schwartz, K.↗
Three-axis adjustable loading structure
A three axis adjustable loading structure for testing the movable surfaces of aircraft by applying pressure, is described. The device has three electric drives where the wall angle, horizontal position, and vertical position of the test device can be rapidly and accurately positioned.
Lynch, E. J.↗
Vertical axis wind rotors: Status and potential
The design and application of a vertical axis wind rotor is reported that operates as a two stage turbine wherein the wind impinging on the concave side is circulated through the center of the rotor to the back of the convex side, thus decreasing what might otherwise be a high negative pressure region. Successful applications of this wind rotor to water pumps, ship propulsion, and building ventilators are reported. Also shown is the feasibility of using the energy in ocean waves to drive the rotor. An analysis of the impact of rotor aspect ratio on rotor acceleration shows that the amount of venting between rotor vanes has a very significant effect on rotor speed for a given wind speed.
Vance, W.↗
Control theory analysis of a three-axis VTOL flight director
A control theory analysis of a VTOL flight director and the results of a fixed-based simulator evaluation of the flight-director commands are discussed. The VTOL configuration selected for this study is a helicopter-type VTOL which controls the direction of the thrust vector by means of vehicle-attitude changes and, furthermore, employs high-gain attitude stabilization. This configuration is the same as one which was simulated in actual instrument flight tests with a variable stability helicopter. Stability analyses are made for each of the flight-director commands, assuming a single input-output, multi-loop system model for each control axis. The analyses proceed from the inner-loops to the outer-loops, using an analytical pilot model selected on the basis of the innermost-loop dynamics. The time response of the analytical model of the system is primarily used to adjust system gains, while root locus plots are used to identify dominant modes and mode interactions.
Niessen, F. R.↗
A three-axis flight simulator
A simulator is described, which was designed for testing and evaluating inertial measuring units, and flight platforms. Mechanical and electrical specifications for the outer, middle, and inner axis are presented. Test results are included.
Mason, M. G.↗