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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 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

Switched steerable multiple beam antenna system

A steerable multibeam five element cross-feed cluster antenna system is described. The feed power is divided into five branches. Each branch includes a switching network comprised of a plurality of time delay elements each individually controlled by a respective electromagnetic latching switch. Frequency independent individual two-dimensional beam steering at intermediate (IF) scanning frequencies is thereby provided wherein discrete incremental time delays are introduced by the switching networks into each branch and the signals recombined thereafter to form each beam. The electromagnetic latched switching reduces power consumption and permits higher power switching and reciprocal coincident tranmsit and receive operation. Frequency independence due to incremental time delay switching permits coincident reciprocal operation and steering for transmit-receive signal paths carrying different transmit-receive frequencies. Diagonal quarter wave plates in the waveguides alter polarization from the circular to orthogonal linear to provide transmitter-receiver isolation.

Richard S Iwasaki↗
NASA NTRS1988

Frequency domain laser velocimeter signal processor

A laser velocimeter signal processor for measuring the signal frequency within a signal burst. The input signal is converted to digital by an ADC 16 and then shifted into shift registers 30 and 31. An automatic gain circuit 15 controls the gain of the input signal. A signal integration circuit 32 determines when a signal burst has been captured by the shift registers and then transfers the contents of the registers to data latches 33 and 34. The data in data latches 33 and 34 is processed by digital bandpass filters 57-63, square law detectors 64-70, burst counters 71-77 and signal processor 78 to determine the frequency of the signal within the captured signal burst.

James F Meyers↗
NASA NTRS1988

Docking system for spacecraft

A mechanism is disclosed for the docking of a spacecraft to a space station where a connection for transfer of personnel and equipment is desired. The invention comprises an active docking structure on a spacecraft and a passive docking structure on the station. The passive structure includes a docking ring mounted on a tunnel structure fixed to the space station. The active structure includes a docking ring carried by an actuator-attenuator devices, each attached at one end to the ring and at its other end in the spacecraft payload bay. The devices respond to command signals for moving the docking ring between a stowed position in the spacecraft to a deployed position suitable for engagement with the docking ring. The devices comprise means responsive to signals of sensed loadings to absorb impact energy and retraction means for drawing the coupled spacecraft and station into final docked configuration and moving the tunnel structure to a berthed position in the spacecraft. Latches couple the spacecraft and space station upon contact of the docking rings and latches establish a structural tie between the spacecraft when retracted.

Kahn, Jon B.↗
NASA NTRS1988

Joints in deployable space truss structures

Since the response of deployable structural concepts being considered for the Large Deployable Reflector (LDR) backup structure will be dominated by the response of joints, the joint characteristics are significant. An overview is given of the research activities at LaRC on the static behavior of joints for deployable space truss structures. Since a pin-clevis-type joint will be utilized in deployable structures, an experimental research program to characterize the joint parameters which affect stiffness was conducted. An experimental research program was conducted on a second type of joint, referred to as a near-center latch joint. It was used in the center of members on the deployable truss structure for the Control of Flexible Structures (COFS) flight experiment. The test results of the near-center latch joint and the member with the joints indicated that the stiffness of the near-center joint is linear and stiffer than the stiffness of the total member, and that non-linearities in the stiffness characteristics of the total member were due to bending introduced at the ends of the member. The resulting data indicates that stiff linear folding joints can be designed and that bending load paths should be avoided whenever possible. In summary, for deployable structures, special attention to the joint and the structure design is required to minimize the undesirable structural non-linearities.

Rhodes, M.↗
NASA NTRS1989

Transient fault behavior in a microprocessor: A case study

An experimental analysis is described which studies the susceptibility of a microprocessor based jet engine controller to upsets caused by current and voltage transients. A design automation environment which allows the run time injection of transients and the tracing from their impact device to the pin level is described. The resulting error data are categorized by the charge levels of the injected transients by location and by their potential to cause logic upsets, latched errors, and pin errors. The results show a 3 picoCouloumb threshold, below which the transients have little impact. An Arithmetic and Logic Unit transient is most likely to result in logic upsets and pin errors (i.e., impact the external environment). The transients in the countdown unit are potentially serious since they can result in latched errors, thus causing latent faults. Suggestions to protect the processor against these errors, by incorporating internal error detection and transient suppression techniques, are also made.

Duba, Patrick↗
NASA NTRS1990

An experimental study of fault propagation in a jet-engine controller

An experimental analysis of the impact of transient faults on a microprocessor-based jet engine controller, used in the Boeing 747 and 757 aircrafts is described. A hierarchical simulation environment which allows the injection of transients during run-time and the tracing of their impact is described. Verification of the accuracy of this approach is also provided. A determination of the probability that a transient results in latch, pin or functional errors is made. Given a transient fault, there is approximately an 80 percent chance that there is no impact on the chip. An empirical model to depict the process of error exploration and degeneration in the target system is derived. The model shows that, if no latch errors occur within eight clock cycles, no significant damage is likely to happen. Thus, the overall impact of a transient is well contained. A state transition model is also derived from the measured data, to describe the error propagation characteristics within the chip, and to quantify the impact of transients on the external environment. The model is used to identify and isolate the critical fault propagation paths, the module most sensitive to fault propagation and the module with the highest potential of causing external pin errors.

Choi, Gwan Seung↗
NASA NTRS1991

Push-To-Lock, Push-To-Release Mechanism

Latch locked or unlocked with single motion of hand. No tools needed to operate it, and user easily opens or closes it with heavily gloved hand. When unlocked, stem free of main body. In locked state, dowel pins in main body hold stem. Latch equipped with lock and key so only authorized users operate it.

Lozano, Anselmo, Jr.↗
NASA NTRS1992

Soft-Capture Mechanism For Collet Joint

Soft-capture mechanism part of latching-and-rigidifying mechanism joining strut rigidly to node on truss. Latching-and-rigidifying mechanism of spreading-collet type, in which collet inserted into base that mates with collet to assure proper alignment, then collet spread to rigidify joint, fixing alignment. Designed to be operable by heavily gloved hand or by robot.

Huff, John E., Jr.↗
NASA NTRS1991

Mechanized fluid connector and assembly tool system with ball detents

A fluid connector system is disclosed which includes a modified plumbing union having a rotatable member for drawing said union into a fluid tight condition. A drive tool is electric motor actuated and includes a reduction gear train providing an output gear engaging an integral peripheral spur gear on the rotatable member. Coaxial alignment means are attached to both the connector assembly and the drive tool. A hand lever actuated latching system includes a plurality of circumferentially spaced latching balls selectively wedged against the alignment means attached to the connector assembly or to secure the drive tool with its output gear in mesh with the integral peripheral spur gear. The drive motor is torque, speed, and direction controllable.

Zentner, Ronald C.↗
NASA NTRS1992

Deployment and retrieval mechanism redesigned for Spartan spacecraft on the STS

The Spartan Release Engage Mechanism (REM) is a system designed to restrain the Spartan spacecraft during Space Transportation System (STS) launch and landing. The mechanism is designed to allow deployment and retrieval of the Spartan free flyer spacecraft from the shuttle payload bay. Because current Spartan spacecraft payloads are much heavier than payloads intended for the original REM, an extensive redesign, analysis, and test program was necessary. Also, increased emphasis on safety in the post-Challenger era prompted a reevaluation of possible failures. Much of the design effort focused on improving the latch mechanism gearbox. Key concerns were effective gear lubrication, thermal gradients at the gearbox mounts, operation at thermal extremes, and gear-train failure contingencies. Increased concern for reliability led to the design of an Extra Vehicular Activity (EVA) backup latch system.

Galloway, Greg↗
NASA NTRS1991

Designing berthing mechanisms for international compatibility

The paper examines the technological issues regarding common berthing interfaces for the Space Station Freedom and pressurized modules from U.S., European, and Japanese space programs. The development of the common berthing mechanism (CBM) is based on common requirements concerning specifications, launch environments, and the unique requirements of ESA's Man-Tended Free Flyer. The berthing mechanism is composed of an active and a passive half, a remote manipulator system, 4 capture-latch assemblies, 16 structural bolts, and a pressure gage to verify equalization. Extensive graphic and verbal descriptions of each element are presented emphasizing the capture-latch motion and powered-bolt operation. The support systems to complete the interface are listed, and the manufacturing requirements for consistent fabrication are discussed to ensure effective international development.

Winch, John↗
NASA NTRS1991

Flight Support System (FSS) docking and umbilical services systems

The Satellite Servicing Project at GSFC in the early 80's developed a facility for servicing observatories in orbit when docked on the shuttle. The facility includes a three point docking ring and one or two umbilicals to provide power, data and command capability to docked payloads. This facility was used in the 1984 repair of the Solar Maximum satellite. It will be used for the Hubble repair mission in 1993, and it is planned to be used on the Explorer Platform retrieval mission in 1995 and for servicing AXAF in the late 90's. The basic three point docking mechanisms and umbilical interfaces were adopted by the OMU Project for that vehicle's remote rendezvous and docking mission capability. This would have assured a common interface for a serviceable payload for either shuttle based or remote servicing, i.e., HST. For OMU remote servicing, quick reaction docking latches were under development when that Project was cancelled. Although there is no remote servicing capability being funded at present, the EOS spacecraft configuration does include three pins compatible with the FSS latches as a contingency planning measure.

Falkenhayn, Edward↗
NASA NTRS1991

Contact dynamics testing of automated three point docking mechanism

TRW has conducted an extensive Contact Dynamics Test Program (CDTP) of the Three Point Docking Mechanism (TPDM). The CDTP tested the ability of the TPDM latches to capture and automatically dock to target spacecraft. The target selected was the Hubble Space Telescope (HST). Mock ups of the TPDM with its three latches and the docking interface of the HST were constructed at the Marshall Space Flight Center (MSFC) in Huntsville, Alabama for use in the tests. The tests were performed at the Flat Floor and Six Degree of Freedom (6-DOF) facilities at MSFC.

Spitzer, Christopher J.↗
NASA NTRS1992

FOCUS - An experimental environment for fault sensitivity analysis

FOCUS, a simulation environment for conducting fault-sensitivity analysis of chip-level designs, is described. The environment can be used to evaluate alternative design tactics at an early design stage. A range of user specified faults is automatically injected at runtime, and their propagation to the chip I/O pins is measured through the gate and higher levels. A number of techniques for fault-sensitivity analysis are proposed and implemented in the FOCUS environment. These include transient impact assessment on latch, pin and functional errors, external pin error distribution due to in-chip transients, charge-level sensitivity analysis, and error propagation models to depict the dynamic behavior of latch errors. A case study of the impact of transient faults on a microprocessor-based jet-engine controller is used to identify the critical fault propagation paths, the module most sensitive to fault propagation, and the module with the highest potential for causing external errors.

Choi, Gwan S.↗
NASA NTRS1993

Connector systems for structures

A releasable coupling device for connecting two members to one another where a collet type fastener has normally retracted latching fingers insertable into a latching recess and a longitudinally movable expander for activating the fastener is described. The longitudinal movement is retained with a paraffin actuated system which can reset. The longitudinal movement of the expander in one direction is through a one way threaded ratchet system which provides an automatic locking action and the expander is movable in either direction by an independently operated threaded action.

Lupo, Christian↗
NASA NTRS1993

Proton radiation testing of an 18 bit A/D converter

An 18-bit first order incremental analog to digital converter (ADC) has been constructed in a 2 mu commercial CMOS process. The ADC was exposed to energetic protons at the Harvard Cyclotron Laboratory to simulate latch-up and noise behavior in low earth orbits. Results of the test indicate no latch-up problems and only a small loss in accuracy while operating in proton radiation with energies similar to the South Atlantic Anomaly.

Thelen, Donald C.↗
NASA NTRS1993

Waves in space plasma dipole antenna subsystem

The Waves In Space Plasma (WISP) flight experiment requires a 50-meter-long deployable dipole antenna subsystem (DASS) to radiate radio frequencies from the STS Orbiter cargo bay. The transmissions are to excite outer ionospheric plasma between the dipole and a free-flying receiver (Spartan) for scientific purposes. This report describes the singular DASS design requirements and how the resulting design satisfies them. A jettison latch is described in some detail. The latch releases the antenna in case of any problems which might prevent the bay doors from closing for re-entry and landing of the Orbiter.

Thomson, Mark↗
NASA NTRS1994

Deployable and retractable telescoping tubular structure development

A new deployable and retractable telescoping boom capable of high deployed stiffness and strength is described. Deployment and retraction functions are controlled by simple, reliable, and fail-safe latches between the tubular segments. The latch and a BI-STEM (Storable Tubular Extendible Member) actuator work together to eliminate the need for the segments to overlap when deployed. This yields an unusually lightweight boom and compact launch configuration. An aluminum space-flight prototype with three joints displays zero structural deadband, low hysteresis, and high damping. The development approach and difficulties are discussed. Test results provide a joint model for sizing flight booms of any diameter and length.

Thomson, M. W.↗