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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 901 records · Page 50

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NASA NTRS1972

Apollo experience reports: Window contamination

The problem of window contamination in the Apollo command module is reviewed. All five command module windows were contaminated while in earth orbit on the first three manned Apollo flights. The contamination sources were identified and eliminated. Preflight testing of lunar module windows showed that no serious contamination should occur, and this conclusion was verified in subsequent manned flights. The command module window designs and materials are described, the window contamination sources are identified, and the inflight and chemical analyses of the contamination are outlined. The corrective actions that were taken are reviewed. For the lunar module, the window design and materials and the preflight and fight evaluations are described. Window design recommendations are made.

Leger, L. J.↗

NASA NTRS1969

Performance of the CSM RCS during the AS 506/CSM 107/LM 5 mission (Apollo 11)

The Apollo 11 service module and the command module (CM) reaction control system performed satisfactorily throughout the mission. Two anomalies which occurred were an inadvertent isolation valve closure during command and service module/Saturn S4B/lunar module separation and a failure of a CM thruster to respond to automatic commands. The isolation valves were later opened by the crew and remained open during the remainder of the mission. The cause of the closure was determined to be the shock loads generated during separation. The CM engine malfunction was caused by a faulty terminal board connector. All system parameters were normal during the mission, and all mission requirements were satisfied.

Lingle, W. N.↗

NASA NTRS1972

Apollo 16 Mission Anomaly Report No. 1: Oxidizer Deservicing Tank Failure

The command module reaction control system is emptied of all remaining propellant using ground support equipment designed to provide an acid/base neutralization of the propellant in both the liquid and gaseous phases so that it may be disposed of safely. During the deactivation operation of the oxidizer from the Apollo 16 command module on 7 May 1972, the scrubber tank of the decontamination unit exploded, destroying the ground support equipment unit and damaging the building that housed the operation. Only minor injuries were received by the personnel in the area and the command module was not damaged. Test results show that the failure was caused by an insufficient quantity of neutralizer for the quantity of oxidizer. This insufficiency lead to exothermic nitration-type reactions which produced large quantities of gas at a very high rate and failed the decontamination tank.

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NASA NTRS1973

Aircraft control system

An aircraft control system is described which is particularly suited to rotary wing aircraft. Longitudinal acceleration and course rate commands are derived from a manual control stick to control translational velocity of the aircraft along a flight path. In the collective channel the manual controls provide vertical velocity commands. In the yaw channel the manual controls provide sideslip or heading rate commands at high or low airspeeds, respectively. The control system permits pilots to fly along prescribed flight paths in a precise manner with relatively low work load.

Rempfer, P. S.↗

NASA NTRS1972

Tracking and data relay satellite system configuration and tradeoff study. Volume 1: TDRS system summary, part 1

A Tracking and Data Relay Satellite System (TDRSS) concept for service of low and medium data rate user spacecraft has been defined. The TDRS system uses two geosynchronous dual spin satellites compatible with Delta 2914 to provide command, tracking, and telemetry service between multiple low earth orbiting users and a centrally located ground station. The low data rate user service capability via each TDRS is as follows: (1) forward link at UHF: voice to one user, commands to 20 users (sequential), range and range rate service, and (2) return link at VHF: voice from one user, data from 20 users (simultaneous), range and range rate return signals. The medium data rate user service via each TDRS is as follows: (1) forward link at S band: voice or command and tracking signals to one user, and (2) return link at S band: voice, data and tracking signals from one user "order wire" for high priority service requests (implemented with an earth coverage antenna).

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NASA NTRS1974

Analysis of a flare-director concept for an externally blown flap STOL aircraft

A flare-director concept involving a thrust-required flare-guidance equation was developed and tested on a moving-base simulator. The equation gives a signal to command thrust as a linear function of the errors between the variables thrust, altitude, and altitude rate and corresponding values on a desired reference flare trajectory. During the simulator landing tests this signal drove either the horizontal command bar of the aircraft's flight director or a thrust-command dot on a head-up virtual-image display of a flare director. It was also used as the input to a simple autoflare system. An externally blown flap STOL (short take-off and landing) aircraft (with considerable stability and control augmentation) was modeled for the landing tests. The pilots considered the flare director a valuable guide for executing a proper flare-thrust program under instrument-landing conditions, but were reluctant to make any use of the head-up display when they were performing the landings visually.

Middleton, D. B.↗

NASA NTRS1975

Apollo experience report: Guidance and control systems: Automated control system for unmanned mission AS-201

The Apollo command module heat shield and Apollo command and service module/Saturn launch vehicle structural integrity were evaluated in an unmanned test flight. An automated control system was developed to provide the mission event sequencing, the real-time ground control interface, and the backup attitude reference system for the unmanned flight. The required mission events, the design logic, the redundancy concept, and the ground-support-equipment concept are described and some development problem areas are discussed. The mission event time line and the real-time ground command list are included to provide an outline of the control system capabilities and requirements. The mission was accomplished with the automated control system, which functioned without flight anomalies.

Holloway, G. F.↗

NASA NTRS1975

Switch selector processing

The proper program execution of the switch selector commands that provide sequencing signals to the launch vehicle hardware was verified. Correct execution of each step necessary to activate a switch selector command and maintenance of the minimum timing requirements between steps are verified through analysis of a series of 6D/LVDC intermediate timing cases. Nominal and perturbed switch selector feedback conditions are simulated to verify correct processing of all realistic and timing combinations. A command which is in progress can be properly terminated by issuance of a forced reset. This is verified by forcing the conditions which require a forced reset and observing that the proper termination is completed.

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NASA NTRS1975

Manual control displays for a four-dimensional landing approach

Six instrument rated pilots flew a STOL fixed base simulator to study the effectiveness of three displays for a four dimensional approach. The three examined displays were a digital readout of forward position error, a digital speed command, and an analog display showing forward position error and error prediction. A flight director was used in all conditions. All test runs were for a typical four dimensional approach in moderate turbulence that included a change in commanded ground speed, a change in flight path angle, and two standard rate sixty degree turns. Use of the digital forward position error display resulted in large overshoot in the forward position error. Some type of lead (rate or prediction information) was shown to be needed. The best overall performance was obtained using the speed command display. It was demonstrated that curved approaches can be flown with relative ease.

Silverthorn, J. T.↗

NASA NTRS1977

Information retrieval and display system

Versatile command-driven data management system offers users, through simplified command language, a means of storing and searching data files, sorting data files into specified orders, performing simple or complex computations, effecting file updates, and printing or displaying output data. Commands are simple to use and flexible enough to meet most data management requirements.

Groover, J. L.↗

NASA NTRS1976

LANDSAT-1 and LANDSAT-2 flight evaluation report

The LANDSAT-1 spacecraft was launched from the Western Test Range on 23 July 1972, at 18:08:06.508Z. The launch and orbital injection phase of the space flight was nominal and deployment of the spacecraft followed predictions. Orbital operations of the spacecraft and payload subsystems were satisfactory through Orbit 147, after which an internal short circuit disabled one of the Wideband Video Tape Recorders (WBVTR-2). Operations resumed until Orbit 196, when the Return Beam Vidicon failed to respond when commanded off. The RBV was commanded off via alternate commands. LANDSAT-1 continued to perform its imaging mission with the Multispectral Scanner and the remaining Wideband Video Tape Recorder providing image data.

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NASA NTRS1977

Digital flight control design for a tandem-rotor helicopter

Methods and results in the continuing development of a digital flight control system (DFCS) for the CH-47B helicopter are examined. The helicopter is the research vehicle for the NASA VTOL Approach and Landing Technology (VALT) Program. It is equipped with comprehensive equipment for the investigation of navigation, guidance, and control requirements for future VTOL aircraft. Two control modes (attitude-command and velocity-command) are implemented, and each mode provides 'Type 1' response to guidance commands. DFCS design is based upon optimal estimation and control methods, which are found to provide flexible and efficient means for defining practical digital control systems.

Stengel, R. F.↗

NASA NTRS1978

Computer interface for mechanical arm

Man/machine interface commands computer-controlled mechanical arm. Remotely-controlled arm has six degrees of freedom and is controlled through "supervisory-control" mode, in which all motions of arm follow set of preprogramed sequences. For simplicity, few prescribed commands are required to accomplish entire operation. Applications include operating computer-controlled arm to handle radioactive of explosive materials or commanding arm to perform functions in hostile environments. Modified version using displays may be applied in medicine.

Derocher, W. L.↗

NASA NTRS1978

Analytical study of ride smoothing benefits of control system configurations optimized for pilot handling qualities

An analytical study was conducted to evaluate the relative improvements in aircraft ride qualities that resulted from utilizing several control law configurations that were optimized for pilot handling qualities only. The airplane configuration used was an executive jet transport in the approach configuration. The control law configurations included the basic system, a rate feedback system, three command augmentation systems (rate command, attitude command, and rate command/attitude hold), and a control wheel steering system. Both the longitudinal and lateral directional axes were evaluated. A representative example of each control law configuration was optimized for pilot handling qualities on a fixed base simulator. The root mean square airplane responses to turbulence were calculated, and predictions of ride quality ratings were computed by using three models available in the literature.

Powers, B. G.↗

NASA NTRS1977

V/STOL hover stability impact on hover control task

Longitudinal static stability requirements for V/STOL aircraft are discussed in terms of vertical landing on a small ship at night, response of the aircraft to air turbulence, and hovering flight. The increased pilot workload encountered under these flight conditions is considered. Results of a flight simulation study performed to evaluate a specific hover control task, two control systems - attitude rate command and translational velocity command, and the pilots' performance with and without turbulence are reported. It is concluded that the translational velocity command system provides the control requirements for good spot hovering capability and reduced pilot workload.

Whitaker, A. B.↗

NASA NTRS1978

GSFC Systems Test and Operation Language (STOL) functional requirements and language description

The Systems Tests and Operation Language (STOL) provides the means for user communication with payloads, applications programs, and other ground system elements. It is a systems operation language that enables an operator or user to communicate a command to a computer system. The system interprets each high level language directive from the user and performs the indicated action, such as executing a program, printing out a snapshot, or sending a payload command. This document presents the following: (1) required language features and implementation considerations; (2) basic capabilities; (3) telemetry, command, and input/output directives; (4) procedure definition and control; (5) listing, extension, and STOL nucleus capabilities.

Desjardins, R.↗

NASA NTRS1978

Steering laws for double-gimbal control-moment gyros

Derivation of CMG steering laws was considered. The type of CMG considered was a double gimbal one which has a constant magnitude momentum vector. The equations for the generation of torque of an inertially fixed CMG are presented. To realize a particular commanded torque, the gimbal rates of the CMG must be specified. These gimbal rates are shown to be functions of gimbal angle orientation and the commanded torque. The conventional cross-product steering law was derived by minimizing a function which was the square of the magnitude of the error between the commanded torque and the realizable torque of the gyro. This steering law was severely dependent upon the inner gimbal angle. When the inner gimbal reaches 90 degrees, the cross product law requires infinite outer gimbal rates to realize finite torque values.

Winder, S. W.↗

NASA NTRS1978

Remote lightning monitor system

An apparatus for monitoring, analyzing and accurately determining the value of peak current, the peak rate of change in current with respect to time and the rise time of the electrical currents generated in an electrical conductive mast that is located in the vicinity where lightning is to be monitored is described. The apparatus includes an electrical coil for sensing the change in current flowing through the mast and generating a voltage responsive. An on-site recorder and a recorder control system records the voltages produced responsive to lightning strikes and converts the voltage to digital signals for being transmitted back to the remote command station responsive to command signals. The recorder and the recorder control system are carried within an RFI proof environmental housing into which the command signals are fed by means of a fiber optic cable so as to minimize electrical interference.

Lennon, C. L.↗