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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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This report presents the results of the Voice Command System (VCS) flight experiment on the five-day STS-41 mission. Two mission specialists,Bill Shepherd and Bruce Melnick, used the speaker-dependent system to evaluate the operational effectiveness of using voice to control a spacecraft system. In addition, data was gathered to analyze the effects of microgravity on speech recognition performance.
This paper presents research on the reliability assessment of adaptive flight control systems. The topics include: 1) Overview of Project Focuses; 2) Reliability Analysis; and 3) Design for Reliability. This paper is presented in viewgraph form.
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A CMOS time-of-flight TOF system-on-a-chip SoC for precise time interval measurement with low power consumption and high counting rate has been developed. The analog and digital TOF chip may include two Constant Fraction Discriminators CFDs and a Time-to-Digital Converter TDC. The CFDs can interface to start and stop anodes through two preamplifiers and perform signal processing for time walk compensation (110). The TDC digitizes the time difference with reference to an off-chip precise external clock (114). One TOF output is an 11-bit digital word and a valid event trigger output indicating a valid event on the 11-bit output bus (116).
The Space Shuttle main propulsion system, like other major elements of the vehicle, has been part of an ongoing program to enhance the flight safety of the Space Transportation System. This activity, inherent in the basic program since its inception, has continued as part of a renewed review of failure modes and effects pertaining to flight-critical functions. Selected components were further evaluated, their potential for impacting flight safety was defined, and then the necessity for changing their design and/or operational practices was determined. Major examples of such components are the 17-inch disconnect and gaseous oxygen flow control valve. This paper summarizes that activity and provides examples of critical processes and components that have been or are being modified to enhance flight safety.
The Small Expendable-tether Deployer System (SEDS) is being built for a 1991 flight on a Delta launch vehicle. SEDS will deploy a 50 lb instrument satellite as an end mass at the end of a 20 km tether. The objective of the experiment is to test the SEDS design concept by demonstrating that the system will satisfactorily deploy the full 20 km tether without stopping prematurely, come to a smooth stop on application of the brake, and cut the tether at the proper time after it swings to the vertical. SEDS will also collect data that will be used to test the accuracy of tether dynamics models for this type of deployment. Radar tracking is planned. In addition, the SEDS on-board computer system will record, store, and continuously transmit data over the Delta II S-band telemetry channel. Initial testing of the software under simulated flight conditions was performed. These tests used both assembly language routines running on SEDS data systems and C-language routines on an IBM-PC. As the software now stands relatively few additions are needed before the entire set of flight software is complete.
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The National Aeronautics and Space Administration (NASA) has flight-tested a flush airdata sensing (FADS) system on the Hyper-X Research Vehicle (X-43A) at hypersonic speeds during the course of two successful flights. For this series of tests, the FADS system was calibrated to operate between Mach 3 and Mach 8, and flight test data was collected between Mach 1 and Mach 10. The FADS system acquired pressure data from surface-mounted ports and generated a real-time angle-of-attack (alpha) estimate on board the X-43A. The collected data were primarily intended to evaluate the FADS system performance, and the estimated alpha was used by the flight control algorithms on the X-43A for only a portion of the first successful flight. This paper provides an overview of the FADS system and alpha estimation algorithms, presents the in-flight alpha estimation algorithm performance, and provides comparisons to wind tunnel results and theory. Results indicate that the FADS system adequately estimated the alpha of the vehicle during the hypersonic portions of the two flights.
Hughes Aircraft Company developed qualified and integrated flight, a flight test Ion Auxiliary Propulsion System (IAPS), on an Air Force technology satellite. The IAPS Flight Package consists of two identical Thruster Subsystems and a Diagnostic Subsystem. Each thruster subsystem (TSS) is comprised of an 8-cm ion Thruster-Gimbal-Beam Shield Unit (TGBSU); Power Electronics Unit; Digital Controller and Interface Unit (DCIU); and Propellant Tank, Valve and Feed Unit (PTVFU) plus the requisite cables. The Diagnostic Subsystem (DSS) includes four types of sensors for measuring the effect of the ion thrusters on the spacecraft and the surrounding plasma. Flight qualifications of IAPS, prior to installation on the spacecraft, consisted of performance, vibration and thermal-vacuum testing at the unit level, and thermal-vacuum testing at the subsystem level. Mutual compatibility between IAPS and the host spacecraft was demonstrated during a series of performance and environmental tests after the IAPS Flight Package was installed on the spacecraft. After a spacecraft acoustic test, performance of the ion thrusters was reverified by removing the TGBSUs for a thorough performance test at Hughes Research Laboratories (HRL). The TGBSUs were then reinstalled on the spacecraft. The IAPS Flight Package is ready for flight testing when Shuttle flights are resumed.
This paper discusses very specifically the mode of the Mariner Venus/Mercury 1973 (MVM'73) telecommunications system in the interplexed dual channel 117.6 kilobits per second (kbps) and 2.45 kbps telemetry. This mode, originally designed for only Venus encounter, was also used at Mercury despite significantly less performance margin. Detailed analysis and careful measurement of system performance before and during flight operations allowed critical operational decisions, which made maximum use of the system capabilities.
The requirements are assessed for the use of remote computation to support HRV flight testing. First, remote computational requirements were developed to support functions that will eventually be performed onboard operational vehicles of this type. These functions which either cannot be performed onboard in the time frame of initial HRV flight test programs because the technology of airborne computers will not be sufficiently advanced to support the computational loads required, or it is not desirable to perform the functions onboard in the flight test program for other reasons. Second, remote computational support either required or highly desirable to conduct flight testing itself was addressed. The use is proposed of an Automated Flight Management System which is described in conceptual detail. Third, autonomous operations is discussed and finally, unmanned operations.
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For the Hyper-X/X-43A program, the development of a comprehensive validation test plan played an integral part in the success of the mission. The goal was to demonstrate hypersonic propulsion technologies by flight testing an airframe-integrated scramjet engine. Preparation for flight involved both verification and validation testing. By definition, verification is the process of assuring that the product meets design requirements; whereas validation is the process of assuring that the design meets mission requirements for the intended environment. This report presents an overview of the program with emphasis on the validation efforts. It includes topics such as hardware-in-the-loop, failure modes and effects, aircraft-in-the-loop, plugs-out, power characterization, antenna pattern, integration, combined systems, captive carry, and flight testing. Where applicable, test results are also discussed. The report provides a brief description of the flight systems onboard the X-43A research vehicle and an introduction to the ground support equipment required to execute the validation plan. The intent is to provide validation concepts that are applicable to current, follow-on, and next generation vehicles that share the hybrid spacecraft and aircraft characteristics of the Hyper-X vehicle.
This paper discusses the benefits of conducting multi-system integration testing of space flight elements in lieu of merely shipping and shooting to the launch site and launching. "Ship and shoot" is a philosophy that proposes to transport flight elements directly from the factory to the launch site and begin the mission without further testing. Integration testing, relevant to validation testing in this context, is a risk mitigation effort that builds upon the individual element and system levels of qualification and acceptance tests, greatly improving the confidence of operations in space. The International Space Station Program (ISSP) experience is the focus of most discussions from a historical perspective, while proposed integration testing of the Constellation Program is also discussed. The latter will include Multi-Element Integration Testing (MElT) and Flight Element Integration Testing (FElT).
Electric propulsion systems and spacecraft power sources, flight mechanics, and mission applications
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