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NASA NTRS2004

Double-Acting, Locking Carabiners

A proposed design for carabiners (tether hooks used in mountaineering, rock climbing, and rescue) is intended to make it possible to operate these devices even while wearing thick gloves. According to the proposal, the gate of a carabiner would be capable of swinging either toward or away from the hook body, relative to the closed position. The gate would be spring-biased to return to the closed position. An external locking collar would be pinned to an internal locking rod that would be springloaded to slide the collar longitudinally over the gate to lock the gate in the closed position. The gate would be unlocked by sliding the collar axially against the spring load. To reduce the probability of inadvertent unlocking, the rod-and-collar mechanism would include two locking buttons. Optionally, the rod-and-collar mechanism could be replaced with an external locking mechanism based on a longer collar.

Chang, Chi-Min↗

NASA NTRS2019

Time Resolved Irradiance of an Integrating Sphere Illuminated by a Mode-Locked Optical Parametric Oscillator

Tunable laser based illumination sources have been adopted by a number of recent hyperspectral instruments for pre-launch spectral radiometric calibration. Some of these sources use mode-locked cavity configurations, which produce a pulse train and create an undesirable fluctuation in the radiometric source at the mode locking frequency. Although typically this frequency is several orders of magnitude higher than the instrument response, care must be taken to ensure the resultant calibration is not biased due to detector or electronic saturation effects. The temporal averaging properties of an integrating sphere can be used to reduce high frequency fluctuations to an acceptable level. In this work, the time resolved output of an integrating sphere coupled with a mode-locked source was measured. A 76 cm diameter sphere with 30 cm output aperture was illuminated using a mode-locked pulse train at 76 MHz, with single pulse durations of 12 ps. The time constant of the sphere was found to be 36 ns, and the resultant temporal averaging of pulses produced a maximum time varying irradiance at the output of 20% of the mean. The form of this time variance is a sawtooth pattern, with a sharp rise during the introduction of each pulse into the sphere followed by a slower decay between pulses. A comparison of instrument calibration data generated with this integrating sphere using both a mode locked source and a continuous wave source is also given. .

McAndrew, Brendan↗

NASA NTRS2014

Shape Memory Alloy (SMA)-Based Launch Lock

Most NASA missions require the use of a launch lock for securing moving components during the launch or securing the payload before release. A launch lock is a device used to prevent unwanted motion and secure the controlled components. The current launch locks are based on pyrotechnic, electro mechanically or NiTi driven pin pullers and they are mostly one time use mechanisms that are usually bulky and involve a relatively high mass. Generally, the use of piezoelectric actuation provides high precession nanometer accuracy but it relies on friction to generate displacement. During launch, the generated vibrations can release the normal force between the actuator components allowing shaft's free motion which could result in damage to the actuated structures or instruments. This problem is common to other linear actuators that consist of a ball screw mechanism. The authors are exploring the development of a novel launch lock mechanism that is activated by a shape memory alloy (SMA) material ring, a rigid element and an SMA ring holding flexure. The proposed design and analytical model will be described and discussed in this paper.

launch lock↗

DOE OSTI2024

Frequency‐Locked Wireless Multifunctional Surface Acoustic Wave Sensors

Abstract Surface acoustic waves (SAWs) have shown great potential for developing sensors for structural health monitoring (SHM) and lab‐on‐a‐chip (LOC) applications. Existing SAW sensors mainly rely on measuring the frequency shifts of high‐frequency (e.g., >0.1 GHz) resonance peaks. This study presents frequency‐locked wireless multifunctional SAW sensors that enable multiple wireless sensing functions, including strain sensing, temperature measurement, water presence detection, and vibration sensing. These sensors leverage SAW resonators on piezoelectric chips, inductive coupling‐based wireless power transmission, and, particularly, a frequency‐locked wireless sensing mechanism that works at low frequencies (e.g., <0.1 GHz). This mechanism locks the input frequency on the slope of a sensor's reflection spectrum and monitors the reflection signal's amplitude change induced by the changes of sensing parameters. The proof‐of‐concept experiments show that these wireless sensors can operate in a low‐power active mode for on‐demand wireless strain measurement, temperature sensing, and water presence detection. Moreover, these sensors can operate in a power‐free passive mode for vibration sensing, with results that agree well with laser vibrometer measurements. It is anticipated that the designs and mechanisms of the frequency‐locked wireless SAW sensors will inspire researchers to develop future wireless multifunctional sensors for SHM and LOC applications.

Bo, Luyu↗

DOE OSTI2025

Injection locking and coupling dynamics in superconducting nanowire-based cryogenic oscillators

Oscillators designed to function at cryogenic temperatures play a critical role in superconducting electronics and quantum computing by providing stable, low-noise signals with minimal energy loss. Here, in this work, we present a comprehensive numerical study of injection locking and mutual coupling dynamics in superconducting nanowire (ScNW)-based cryogenic oscillators. Using the design space of a standalone ScNW-based oscillator, we investigate two critical mechanisms that govern frequency synchronization and signal coordination in cryogenic computing architectures: (1) injection locking induced by an external AC signal with a frequency near the oscillator's natural frequency, and (2) the mutual coupling dynamics between two ScNW oscillators under varying coupling strengths. We identify key design parameters—such as shunt resistance, nanowire inductance, and coupling strength—that govern the locking range. Additionally, we examine how the amplitude of the injected signal affects the amplitude of the locked oscillation, offering valuable insights for power-aware oscillator synchronization. Furthermore, we analyze mutual synchronization between coupled ScNW oscillators using capacitive and resistive coupling elements. Our results reveal that the phase difference between oscillators can be controlled by tuning the coupling strength, enabling programmable phase-encoded information processing. These findings could enable building ScNW-based oscillatory neural networks, synchronized cryogenic logic blocks, and on-chip cryogenic resonator arrays.

Artificial neural networks↗

NASA NTRS1974

Dually-mode-locked ND: YAG laser

Mode-locking is stabilized effectively by conventional loss-modulator and phase-modulator, mode-locking elements placed in laser cavity in optical series with one another. Resulting dually-mode-locked system provides pulses with constant phase relative to mode-lock drive signal without presence of relaxation oscillation noise.

Osmundson, J.↗

NASA NTRS1975

Phase-locked loops

An attempt to systematically outline the work done in the area of phase-locked loops which are now used in modern communication system design is presented. The analog phase-locked loops are well documented in several books but discrete, analog-digital, and digital phase-locked loop work is scattered. Apart from discussing the various analysis, design, and application aspects of phase-locked loops, a number of references are given in the bibliography.

Gupta, S. C.↗

NASA NTRS1978

False lock performance of Shuttle Costas loop receivers

The false (sideband) lock problem in Shuttle Costas loop receivers, in the presence of noise, is assessed. False lock margin is defined depending on symbol signal-to-noise ratio rather than in the absence of noise. Closed-form results are given for the case where the arm filters of the Costas loop are one-pole Butterworth filters as used in the Shuttle receivers. However, the approach taken is also general enough to cover filters of arbitrary characteristics. As part of the development of the false lock margin, it is shown that the false lock phenomenon of the squaring loop is identical to that of the Costas loop.

Woo, K. T.↗

NASA NTRS1978

Pulse compression inside an actively AM mode-locked Nd:YAG laser using a liquid Kerr cell

A mode-locked Nd:YAG laser capable of generating pulses substantially shorter than the present limit of 30-50 ps, while retaining the stability of active mode locking, would be a useful development. This study presents a simplified theoretical analysis and a preliminary experimental verification of the use of an optical Kerr cell as a passive lossless pulse compressor inside a Q-switched and actively mode-locked YAG laser. The theoretical model indicates possible compression to as short as about 5 ps in a typical low-power Nd:YAG laser. The preliminary experimental results show substantial pulse compression via the predicted mechanism, though still not below about 30 ps. The technique appears capable, however, of pulse compression to substantially shorter values without the instabilities, statistical fluctuations, or energy losses associated with saturable-absorber mode locking.

Duerinckx, A. J.↗

NASA NTRS1981

PN lock indicator for dithered PN code tracking loop

In a delay-lock one-delta (+or - 1/2 chip) dithered PN code tracking loop, an indication of lock in the PN code tracking loop is provided by delaying the dithered local PN code by a half chip to produce a +0, -1 dithered PN code that is then multiplied with the received PN-spread IF signal to produce a signal proportional to the correlation of this dithered code offset from the received code. The correlation signal is bandpass filtered, amplified with AGC control, and square-law detected to obtain a dc signal proportional to the degree of correlation. The dc signal is multiplied by the dithering control signal to effectivity substract noise voltage from the lock correlation signal which is then compared with a PN lock status signal.

Carson, L. M.↗

NASA NTRS1983

A study into the loss of lock of the space telescope fine guidance sensor

The results of a study into the loss of lock phenomenon associated with the Space Telescope Fine Guidance Sensor (FGS) are documented. The primary cause of loss of lock has been found to be a combination of cosmic ray spikes and photon noise due to a 14.5 Mv star. The probability of maintaining lock versus time is estimated both for the baseline FGS design and with parameter changes in the FGS firmware which will improve the probability of maintaining lock. The parameters varied are changeable in-flight from the ground and hence do not impact the design of the FGS hardware.

Polites, M. E.↗

NASA NTRS1982

Developments in mode-locked lasers and their applications

The most important recent advance with respect to mode locking has been the development of 'colliding-pulse' mode locking. An important extension to this method is reported. According to this extension, the colliding pulse function is obtained by making use of an 'antiresonant ring' laser cavity. The new concept has been applied to a flash-pumped passively mode-locked Nd:YAG laser in a number of experiments. Attention is given to mode locking of a self-pumped phase conjugate laser, picosecond photoacoustic experiments, and picosecond pulses on semiconductor surfaces.

Siegman, A. E.↗

NASA NTRS1984

Testing and evaluation of Vespel up to 450 deg F when used in nuts and bolts as a self-locking element

The object of this investigation was to evaluate Vespel for potential application on the Solid Rocket Booster to replace all-metal deformed self-locking nuts and anchor nuts and be used as self-locking elements for bolts and screws. The Vespel self-locking elements were tested for prevailing torque retention at room temperature, after heating to 450 F and exposure for 3 hr, breakaway torque at 450 F and for vibration at a level consistent with the maximum expected on the SRB at lift-off and reentry. The investigation revealed Vespel has properties that can provide a self-locking capability for threaded fasteners up to 450 F and it can be used in nuts and anchor nuts for installation on the SRB. Vespel elements in bolts did not meet all our SRB requirements for reuse, however, we have defined a design for Vespel elements in nuts/anchor nuts that fully meets all requirements. It is recommended that No. 1, 1/4 in. and 5/16 in. nuts/anchor nuts be procured for use on the SRB. This system will eliminate the galling problems now encountered and achieve a much higher reuse life than the present deformed nut design.

Wood, C. M.↗

NASA NTRS1985

Ensuring fault tolerance of phase-locked clocks

Processors within a real-time multiprocessor system must be synchronized with as little overhead as possible. Although synchronization can be achieved via both software (e.g., interactive convergence and interactive consistency algorithms) and hardware (e.g., multistage synchronizers and phase-locked clocks), phase-locked clocks are most attractive due to their small overheads. Despite the fact that synchronization of the multiprocessor system with phase-locked clocks is totally different in nature from the interactive consistency algorithm, it is presently proven that it must satisfy the same condition, N equal to or greater than 3m + 1, where N is the total number of clocks in the multiprocessor system and m is the maximum number of faults tolerable. Also presented are results showing how to design phase-locked clocks so as to be impervious up to a given arbitrary number of malicious failures.

Krishna, C. M.↗

NASA NTRS1986

Preliminary results toward injection locking of an incoherent laser array

The preliminary results of phase locking an incoherent laser array to a master source in an attempt to achieve coherent operation are presented. The techniques necessary to demonstrate phase locking are described along with some topics for future consideration. As expected, the results obtained suggest that injection locking of an array, where the spacing between adjacent longitudinal modes of its elements is significantly larger than the locking bandwidth, may not be feasible.

Daher, J.↗

NASA NTRS1987

False lock performance in polarity-type Costas receivers in the presence of periodic data patterns

The authors address the false-lock performance of receivers which use polarity-type Costas loops for the carrier recovery of unbalanced quadrature phase-shift keyed (QPSK), asynchronous QPSK or binary PSK (BPSK) signals in the presence of periodic data patterns. The potential false-lock frequencies are first identified. Expressions for both true-lock and false-lock components are also derived, thereby allowing numerical evaluation of various key parameters for cases of practical interest.

Wang, James June-Ming↗

NASA NTRS1987

Time-locked time-histories - A new way of examining eye-movement data

A problem often encountered when eye-movement measurement is conducted is the choice of 'indices' or 'statistics' available to present such information. The present study reports the use of the Time-Locked Time-History as a technique of value in the examination and presentation of eye-movement data. Plots created using this technique are labeled time-locked time-histories as they illustrate subject eye lookpoint during a period of time before and after a certain time-locking event. Events that occur with some degree of repetition, such as the onset or termination of control activities, warning signals, or changes in indicator positions may be utilized as time-locking events. The present study reports the use of this technique in an eye-movement study using a secondary task in which the subject must discriminate specific types of information in the display.

Comstock, J. Raymond, Jr.↗

NASA NTRS1989

Costas loop lock detection in the advanced receiver

The advanced receiver currently being developed uses a Costas digital loop to demodulate the subcarrier. Previous analyses of lock detector algorithms for Costas loops have ignored the effects of the inherent correlation between the samples of the phase-error process. Accounting for this correlation is necessary to achieve the desired lock-detection probability for a given false-alarm rate. Both analysis and simulations are used to quantify the effects of phase correlation on lock detection for the square-law and the absolute-value type detectors. Results are obtained which depict the lock-detection probability as a function of loop signal-to-noise ratio for a given false-alarm rate. The mathematical model and computer simulation show that the square-law detector experiences less degradation due to phase jitter than the absolute-value detector and that the degradation in detector signal-to-noise ratio is more pronounced for square-wave than for sine-wave signals.

Mileant, A.↗