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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 379 records · Page 21
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Failure detection and isolation methods for redundant gimballed inertial measurement units.

Skewed alignment of two redundant conventional inertial measuring units permits nonambiguous detection and isolation of hard and soft failures in real time by an airborne computer. Accelerometer outputs and gimbal readouts are monitored periodically, and attitude rate and velocity error vectors are computed from these data. Magnitudes of these vectors provide failure detection, and projection of these error vectors onto the coordinate axes of the two clusters permits isolation. A detailed Monte Carlo simulation of one version of the mechanization as applied to Space Shuttle boost trajectories demonstrates effectiveness down to very low levels of inertial instrument performance failures. The results indicate that worst case overall navigation performance occurs when accelerometer failures are of the order of 20 sigma and gyro failures are about 100 sigma for conventional state-of-the-art IMU instruments.

Solov, E. G.↗
NASA NTRS1973

The application of standardized control and interface circuits to three dc to dc power converters.

Standardized control and interface circuits were applied to the three most commonly used dc to dc converters: the buck-boost converter, the series-switching buck regulator, and the pulse-modulated parallel inverter. The two-loop ASDTIC regulation control concept was implemented by using a common analog control signal processor and a novel digital control signal processor. This resulted in control circuit standardization and superior static and dynamic performance of the three dc-to-dc converters. Power components stress control, through active peak current limiting and recovery of switching losses, was applied to enhance reliability and converter efficiency.

Yu, Y.↗
NASA NTRS1971

Single-stage earth-orbital reusable vehicle space shuttle feasibility study. Volume 2: Aerodynamic model testing

This volume is one of a 6-volume final report of the Study of a Single-stage Earth-orbital Reusable Vehicle (SERV). The study was conducted by the Chrysler Corporation Space Division (CCSD) for the National Aeronautics and Space Administration, George C. Marshall Space Flight Center under Contract NAS8-26341. The purpose of the study was to evaluate the potential of SERV as the boost element of a candidate space transportation system. To establish the SERV potential, five key technical areas affecting concept feasibility were identified for examination: engine performance, aerodynamic characteristics, thermal protection, subsystem weights, and the landing method. The results of analyses are published in a final reporting consisting of the following six volumes: Volume 1 Summary Volume 2 Aerodynamic Model Testing Volume 3 Concept Evaluation Volume 4 Vehicle Definition Volume 5 Operations Definition Volume 6 Resources

C. E. Tharratt↗
NASA NTRS1973

Unsteady aerodynamic analysis of space shuttle vehicles. Part 3: Booster interference effects

An investigation of the interference flow field on the space-shuttle boost configuration has been made. The results show that the interference effects can dominate the shuttle aerodynamics. Vortices shed from shock-induced flow separations on the forward portion of the vehicle affect the aerodynamic loads on the aft portion of the booster. Thus, the forebody and aft-body flow fields are coupled. This coupling and the associated time lag due to the finite convection speed of the vortices furnish a mechanism whereby the unsteady aerodynamics can cause undamping of certain low frequency elastic modes of the booster. A preliminary order-of-magnitude analysis of the aeroelastic stability of the shuttle booster indicates that negative aerodynamic damping could occur for at least one bending mode and be of sufficient magnitude to dominate the structural damping. The implication of these results, (with the possibility of undamped oscillations leading to structural failure), is serious enough to warrant further, more detailed analysis.

Reding, J. P.↗
NASA NTRS1973

Evaluation of dispersion strengthened nickel-base alloy heat shields for space shuttle application

The work reported constitutes the first phase of a two-phase program. Vehicle environments having critical effects on the thermal protection system are defined; TD Ni-20Cr material characteristics are reviewed and compared with TD Ni-20Cr produced in previous development efforts; cyclic load, temperature, and pressure effects on TD Ni-20Cr sheet material are investigated; the effects of braze reinforcement in improving the efficiency of spotwelded, diffusion-bonded, or seam-welded joints are evaluated through tests of simple lap-shear joint samples; parametric studies of metallic radiative thermal protection systems are reported; and the design, instrumentation, and testing of full-scale subsize heat shield panels are described. Tests of full-scale subsize panels included simulated meteoroid impact tests; simulated entry flight aerodynamic heating in an arc-heated plasma stream; programmed differential pressure loads and temperatures simulating mission conditions; and acoustic tests simulating sound levels experienced by heat shields during about boost flight. Test results are described, and the performances of two heat shield designs are compared and evaluated.

Johnson, R., Jr.↗
NASA NTRS1974

IMPMOT user's manual

This user's manual describes the input and output variables as well as the job control language necessary to utilize the IMP-H apogee motor firing program, IMPMOT. The IMPMOT program can be executed as either a stand-alone program or as a member of the flight dynamics system. This program is used to determine the time and attitude at which to fire the IMP-H apogee boost motor. The IMPMOT program is written in FORTRAN 4 for use on the IBM 360 series computer.

Stewart, D. J.↗
NASA NTRS1972

Study of Uncertainties of Predicting Space Shuttle Thermal Environment

Quantitative estimates of the uncertainty in predicting aerodynamic heating rates for a fully reusable space shuttle system are developed and the impact of these uncertainties on Thermal Protection System (TPS) weight are discussed. The study approach consisted of statistical evaluations of the scatter of heating data on shuttle configurations about state-of-the-art heating prediction methods to define the uncertainty in these heating predictions. The uncertainties were then applied as heating rate increments to the nominal predicted heating rate to define the uncertainty in TPS weight. Separate evaluations were made for the booster and orbiter, for trajectories which included boost through reentry and touchdown. For purposes of analysis, the vehicle configuration is divided into areas in which a given prediction method is expected to apply, and separate uncertainty factors and corresponding uncertainty in TPS weight derived for each area.

Fehrman, A. L.↗
NASA NTRS1974

Digital image enhancement techniques used in some ERTS application problems

Enhancements discussed include contrast stretching, multiratio color displays, Fourier plane operations to remove striping and boosting MTF response to enhance high spatial frequency content. The use of each technique in a specific application in the fields of geology, geomorphology and oceanography is demonstrated.

Goetz, A. F. H.↗
NASA NTRS1974

Asymmetrical booster guidance and control system design study. Volume 3: Space shuttle vehicle SRB actuator failure study

The investigation of single actuator failures on the space shuttle solid rocket booster required the analysis of both square pattern and diamond pattern actuator configurations. It was determined that for failures occuring near or prior to the region of maximum dynamic pressure, control gain adjustments can be used to achieve virtually nominal mid-boost vehicle behavior. A distinct worst case failure condition was established near staging that could significantly delay staging. It is recommended that the square pattern be retained as a viable alternative to the baseline diamond pattern because the staging transient is better controlled resulting in earlier staging.

Williams, F. E.↗
NASA NTRS1974

Advanced planning activity

Selected mission concepts for interplanetary exploration through 1985 were examined, including: (1) Jupiter orbiter performance characteristics; (2) solar electric propulsion missions to Mercury, Venus, Neptune, and Uranus; (3) space shuttle planetary missions; (4) Pioneer entry probes to Saturn and Uranus; (5) rendezvous with Comet Kohoutek and Comet Encke; (6) space tug capabilities; and (7) a Pioneer mission to Mars in 1979. Mission options, limitations, and performance predictions are assessed, along with probable configurational, boost, and propulsion requirements.

Source record↗
NASA NTRS1974

The Space Shuttle Program and its technology

Review of the considerations leading to the development of the Space Shuttle system, followed by a description of the system and an analysis of the current program development status. The Space Shuttle system arose out of a need for a reusable vehicle that could routinely carry large payloads (up to 65,000 lb) into earth orbit and return on a cost-effective basis. The system, as currently baselined, consists of a manned reusable Orbiter vehicle and the booster hardware for ground launching. The proposed Orbiter will be 123 feet long, double delta-winged, and roughly the size of a DC-9. The Orbiter will normally carry a crew of four who will work without space suits in a shirtsleeve environment. The Orbiter will be boosted into space through the simultaneous operation of two solid propellant booster rockets and the Orbiter's three high-pressure liquid oxygen/liquid hydrogen main engines. The Orbiter will have reusable external insulation, since each vehicle will have a design life of ten years.

Thompson, R. F.↗
NASA NTRS1974

Unsteady aerodynamics could dominate the space shuttle booster aeroelastic stability

Quasi-steady techniques are used in a preliminary, order of magnitude, analysis of the aeroelastic stability of a number of space shuttle boost configurations. The configurations analyzed all have at least one low frequency free-free bending mode that is aerodynamically undamped due to aerodynamic interference effects. Typically, the aerodynamic interference effects involve flow conditions at one vehicle station influencing the loads at another. Due to the finite flow convection velocity and the aerodynamic coupling of flow conditions at different locations on the vehicle, these interference loads result in aerodynamic undamping of one or more of the low frequency free-free elastic modes. The implication of these results, i.e., the possibility of undamped, divergent, oscillations leading to structural failure, (if the aerodynamic undamping should dominate the structural damping) is serious enough to warrant further analytic and experimental investigations.

Reding, J. P.↗
NASA NTRS1974

Turbopump configuration selection for the Space Shuttle main engine

Studies to define the optimum turbopump configurations for the Space Shuttle propulsion system are reported. For each propellant, two turbopumps - one low-pressure and one high-pressure - are needed to generate the high discharge pressures required for engine operation. The optimization of the four pumps resulted in the selection of an axial inducer type for both low-pressure pumps and in a three-stage centrifugal pump for the high-pressure hydrogen turbopump; meanwhile the oxygen pump features a double inlet main impeller. This impeller feeds the thrust chamber injector, as well as a preburner pump, which boosts the main impeller discharge pressure to the required preburner pressure. The interaction between engine performance and obtainable turbopump performance is discussed, and the reasons for the final selection of the turbine and pump types are presented.

Rothe, K.↗
NASA NTRS1974

The case for a high-speed research airplane - Results from an in-house study

Results of a study aimed at determining the feasibility of developing a single versatile high-speed research airplane (HSRA) which will meet flight research needs of both Mach 3 to 5 JP-fueled military aircraft and of hydrogen-fueled aircraft, both military and civil, for speeds up to Mach 10. The proposed HSRA design concept is an air-launched, rocket-boosted research aircraft designed to accommodate a wide variety of large-scale propulsive and structural flight research experiments. The aircraft is a 60-foot-long discrete wing-body concept with high wings and a center-line vertical tail. Heat sink shields are proposed as an effective and versatile method of achieving low-cost, low-risk thermal protection of the all-aluminum primary structure.-

Kirkham, F. S.↗
NASA NTRS1974

Centaur feedline dynamics study using power spectral methods

Tests were conducted to determine the dynamic characteristics of the Centaur/RL-10 oxygen and hydrogen feedlines. The fundamental-mode resonant frequencies were determined by applying power spectral methods to noise-generated data from hot firings of the RL-10 engine. The effect of net positive suction pressure of the main feed pumps on resonant frequency characteristics was determined to be a straight-line relation. Power spectral methods were also used to determine the dynamic characteristics of the boost pumps.

Lorenzo, C. F.↗
NASA NTRS1974

Dynamics of multirate sampled data control systems

The effect was investigated of the synthesis approach (single or multirate) on the machine requirements for a digital control system for the space shuttle boost vehicle. The study encompassed four major work areas: synthesis approach trades, machine requirements trades, design analysis requirements and multirate adaptive control techniques. The primary results are two multirate autopilot designs for the low Q and maximum Q flight conditions that exhibits equal or better performance than the analog and single rate system designs. Also, a preferred technique for analyzing and synthesizing multirate digital control systems is included.

Naylor, J. R.↗
NASA NTRS1975

Titan/Centaur T/C-1 post flight evaluation report

The first Titan/Centaur launch vehicle, TC-1, was launched from the Eastern Test Range Complex 41 at 09:48:01.46 hours Eastern Daylight Time on February 11, 1974. The vehicle carried a dynamic mass model of the Viking spacecraft and a SPHINX spacecraft, intended to study high voltage interactions in space. This launch was a Proof Flight of a vehicle con- figuration integrating the Air Force Titan booster and the NASA Centaur upper stage. It also was the first flight of the Centaur Standard Shroud developed for the Titan/Centaur. The countdown for the launch proceeded normally except for an additional 45 minute hold which was required to resolve a question concerning interpretation of booster hydraulic system data. The launch window opened at 09:03:00 hours Eastern Daylight Time. The vehicle was launched o on a flight azimuth of 105°. The Titan boost phase of flight was satisfactory. Solid Motor operation, Stage I and Stage II operation were normal. Venting of the Centaur Standard Shroud during ascent was successful and shroud separation and jettison was accomplished without incident. At the completion of the Titan Stage II burn, the Centaur successfully separated from the Titan. At this time, the Centaur main engines were sequenced through the first planned starting cycle but failed to achieve steady state operation. The vehicle flight control system, not sensing vehicle acceleration, commanded engine shutdown, and recycled, as programmed, through a back-up engine start attempt. The second engine start attempt was also unsuccessful. The flight control system then placed the vehicle in a coast-phase mode and the vehicle continued downrange in free fall. The vehicle was destroyed by Range Safety when the impact point was approximately 2200 nautical miles downrange, 12 minutes, 28.5 seconds after liftoff.

S. V. Szabo, Jr.↗