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NASA NTRS2019

NASA's Space Launch System: Payload Opportunities for Lunar Exploration, Science Missions

Nearing its first launch, the Space Launch System (SLS), NASA’s new super heavy-lift launch vehicle, offers highly energetic launches that deliver more mass and provide more volume in 8.4 m-diameter and potentially larger fairings to make a new generation of deep space missions possible. An evolvable launcher available in crew, crew with a co-manifested payload (CPL) and cargo-only configurations, SLS is a crucial capability to enable astronauts to return to the Moon, but it also offers key benefits for science missions. NASA’s 21st-century return to the Moon recently received a formal name: the Artemis program. In addition to the core enabling capabilities of SLS and the Orion crew spacecraft, NASA will also enlist international and commercial partnerships for Artemis. The Agency intends to build a scientific outpost in lunar orbit, the Gateway, from which human and robotic missions to and from the surface can rendezvous. SLS will launch Orion on a series of missions leading to landing the first woman and the next man on the Moon as part of Artemis. SLS uses proven propulsion systems: two solid rocket boosters and four RS-25s engines that have been upgraded to provide more thrust and operate in the SLS environment. SLS Block 1 uses a modified Delta IV Heavy upper stage, called the Interim Cryogenic Propulsion Stage (ICPS) and lifts at least 26 metric tons (t) to trans-lunar injection (TLI). The Block 1 vehicle can also be outfitted with a 5 m-diameter fairing. Block 1B, the next major variant, also uses solid rocket boosters and RS-25 engines to achieve Earth escape velocity, but replaces the single-engine liquid hydrogen (LH2)/liquid oxygen (LOX) ICPS with a four-engine LH2/LOX Exploration Upper Stage (EUS) to increase mass to TLI to 34-37 t, depending on crew or cargo configuration. In the Block 1B crew configuration, a 10 m-tall Universal Stage Adapter (USA) connects the vehicle to Orion and can carry a CPL up to 10 t. The USA provides 286 m3 of unpressurized volume for payloads. For large payloads, 8.4 m- and 10 m-diameter cargo fairings in 19.1 m and 27.4 m lengths are possible. The ultimate SLS vehicle, Block 2, incorporates evolved boosters to reach a lift capacity of more than 45 t to TLI. The capabilities of SLS not only make new missions to the Moon possible, but also game-changing science missions, such as deployment of large-aperture space telescopes, spacecraft to the ice giants or even probes to the interstellar medium. This paper will discuss the capabilities of SLS, the vehicle’s planned evolution, missions that can effectively utilize the vehicle and manufacturing status of the vehicle.

Creech, Steve↗
NASA NTRSDate not supplied

In-Situ Detection of Process-Induced Porosity During Cure of Out-of-Autoclave Composites

Composite materials offer unique benefits in aerospace applications, including high strength-to-weight ratio, and are becoming increasingly used by industry manufacturers. Current manufacturing and processing methods can lead to defects in the composites, which are identified after fabrication using inspection methods. This study utilized a high-temperature ultrasonic inspection system to detect process-induced porosity in an out-of-autoclave (OOA) composite panel during cure. In order to perform ultrasonic scans in-situ during cure, the system needed to be able to operate at oven temperatures up to 200 °C. There are no commercially available ultrasonic scanning systems that can operate continuously at these temperatures, so an enclosure was fabricated to insulate the ultrasonic system in the curing oven. The enclosure housed a MISTRAS® motorized X-Y raster scanner and contact transducer (Olympus® X2002). The Olympus® X2002 contact transducer is a continuous high-temperature delay line transducer with a center frequency of 2.25 MHz. In order to prevent the inside of the enclosure from reaching high temperatures, a sparge pipe inside the cooling enclosure was connected to a liquid nitrogen (LN2) tank outside of the oven via insulated hoses. The cooling system was automatically controlled by a temperature controller that was programmed to open a solenoid valve along the hose at 31 ℃ and close at 28 ℃ inside the cooling enclosure. When the solenoid valve was open, LN2 would flow from the LN2 tank and vaporize prior to reaching cooling enclosure. A U-shaped sparge pipe had holes drilled along its length to uniformly introduce cold nitrogen gas into the cooling enclosure. This prevented the motors from ever reaching the maximum desired operating temperature of 38 ℃. In the bottom of the enclosure, the tool plate was placed with the composite facing the outside of the enclosure, exposing it to the temperatures of the oven. The tool plate was 63.5 mm thick borosilicate glass, which was chosen for its low ultrasonic attenuation and moderate thermal conductivity. A thin layer of ultrasonic couplant was placed on the tool plate. The transducer sent and received ultrasonic waves through the tool plate into the composite. A MISTRAS® Remote UT System performed all wave generation, analog to digital conversion, and data acquisition and processing. The transducer was connected directly to the Remote UT System via a high-temperature BNC cable (CD International, RG-316). Polyimide insulated copper wire was used to connect the scanner to a 2-axis motor drive, which was connected to the Remote UT System. The motor drive and Remote UT System were located outside the industrial oven. A diagram of the ultrasonic system is shown in Figure 1. Figure 1: Diagram of ultrasonic in-situ defect detection system. In this study, a porosity gradient was introduced into the carbon fiber reinforced polymer (CFRP) composite through a misfit of the part and caul plate. A 24-ply quasi-isotropic ([0/90, ±45]12S) composite panel was laid up using Newport® AS4C-M/NB321 out-of-autoclave (OOA) plain weave (PW) prepreg (42% resin content, 195 g/m2). The first 16 plies were 203 mm × 203 mm. Ply drops were incorporated into the panel by decreasing the length of plies 17-24. The sizes of each ply are included in Table 1. All plies were centered along their length (x-axis) creating a trapezoidal type cross-section. Table 1: Ply sizes Plies Length (mm) Width (mm) 1-16 203 203 17-18 102 203 19-20 85 203 21-22 68 203 23-24 51 203 A 15-5 stainless steel caul plate (Size: 203 × 203 × 1.2 mm) was placed on the laminate. The composite and caul plate were vacuum bagged to the tool plate. Per the product datasheet, Newport 321 can be cured between 121 °C and 149 °C, depending on service temperature, with a hold for 90-120 minutes. Based on prior thermal testing of the cooling enclosure, the desired composite temperature cycle could be attained when the air temperature of the oven was ramped to 160 °C at a rate of 1.7 °C/min with a 3 hour hold. The extended hold was not necessary to cure the composite, but did allow for additional scans at the cure temperature during preliminary testing. The composite panel was under vacuum pressure for the entire cure cycle. Under vacuum, the caul plate deformed causing high and low pressure regions. The low-pressure regions formed high porosity in the composite part. The ultrasonic data collected showed that the inspection system was able to monitor the evolution of porosity within the composite throughout the cure cycle. Fifty scans of a 203 mm × 51 mm (8 in. × 2 in.) area of the composite were completed throughout the cure cycle. The scan speed was set to 43 mm/s in the x-direction and 36 mm/s in the y-direction, with a 1.0 mm/pixel resolution in both directions. Each scan took approximately five minutes to complete. Figure 2 shows C-scan amplitude data (top view) from one scan during the cure cycle. The color map indicates the maximum amplitude (%) measured with a time gate that contains reflections from the back surface (furthest from the transducer in contact with the caul plate) of the composite. Because porosity in the composite increases the ultrasonic attenuation in the composite part, a higher amplitude (red) indicates low porosity and a lower amplitude (blue) indicates high porosity. The regions where the caul plate was applying increased pressure (center and ends of the panel) resulted in reduced porosity, whereas the ply drop regions had reduced pressure and thus had higher porosity. Figure 2: Amplitude C-scan (top view) of OOA composite from one scan during the 160 °C temperature hold. Higher amplitude (red) indicates low porosity. Lower amplitude (blue) indicates high porosity. A B-scan is a two-dimensional image plotting the ultrasonic signals from a single y-position at every x-location of the composite panel. The travel time (μs) of the ultrasonic wave (representing the through-thickness location) is plotted along the y-axis, and the ultrasonic wave signal is represented as a contour map. Based on the B-scan data, the location of the defects with respect to the composite thickness was able to be determined. The ply drop regions had high porosity near the front (tool plate) surface of the composite (Figure 3). Figure 3: B-scan (cross-section view) of OOA composite from one scan during the 160 °C temperature hold. Using the data obtained from amplitude C-scans and B-scans throughout the cure cycle, the high and low porosity regions within the composite laminate were detected and localized with high spatial resolution. This paper will discuss the evolution of porosity content in the OOA composite during cure. OOA tests aided the transition of this system to an autoclave, which is the primary method of curing aerospace-grade thermoset composites.

Tyler B. Hudson↗
NASA NTRS2023

Reconfigurations in Brain Networks Upon Awakening From Slow Wave Sleep: Interventions and Implications in Neural Communication

Sleep inertia is the brief period of impaired alertness and performance experienced immediately after waking. Little is known about the neural mechanisms underlying this phenomenon. A better understanding of the neural processes during sleep inertia may offer insight into the awakening process. We observed brain activity every 15 min for 1 hr following abrupt awakening from slow wave sleep during the biological night. Using 32-channel electroencephalography, a network science approach, and a within-subject design, we evaluated power, clustering coefficient, and path length across frequency bands under both a control and a polychromatic short-wavelength-enriched light intervention condition. We found that under control conditions, the awakening brain is typified by an immediate reduction in global theta, alpha, and beta power. Simultaneously, we observed a decrease in the clustering coefficient and an increase in path length within the delta band. Exposure to light immediately after awakening ameliorated changes in clustering. Our results suggest that long-range network communication within the brain is crucial to the awakening process and that the brain may prioritize these long-range connections during this transitional state. Our study highlights a novel neurophysiological signature of the awakening brain and provides a potential mechanism by which light improves performance after waking.

EEG↗
NASA NTRS1988

ARC length control for plasma welding

A control system to be used with a plasma arc welding apparatus is disclosed. The plasma arc welding apparatus includes a plasma arc power supply, a contactor, and an electrode assembly for moving the electrode relative to a work piece. The electrode assembly is raised or lowered by a drive motor. The present apparatus includes a plasma arc adapter connected across the power supply to measure the voltage across the plasma arc. The plasma arc adapter forms a dc output signal input to a differential amplifier. A second input is defined by an adjustable resistor connected to a dc voltage supply to permit operator control. The differential amplifier forms an output difference signal provided to an adder circuit. The adder circuit then connects with a power amplifier which forms the driving signal for the motor. In addition, the motor connects to a tachometor which forms a feedback signal delivered to the adder to provide damping, therby avoiding servo loop overshoot.

William F Iceland↗
NASA NTRS1981

Memory-based frame synchronizer

A frame synchronizer for use in digital communications systems wherein data formats can be easily and dynamically changed is described. The use of memory array elements provide increased flexibility in format selection and sync word selection in addition to real time reconfiguration ability. The frame synchronizer comprises a serial-to-parallel converter which converts a serial input data stream to a constantly changing parallel data output. This parallel data output is supplied to programmable sync word recognizers each consisting of a multiplexer and a random access memory (RAM). The multiplexer is connected to both the parallel data output and an address bus which may be connected to a microprocessor or computer for purposes of programming the sync word recognizer. The RAM is used as an associative memory or decorder and is programmed to identify a specific sync word. Additional programmable RAMs are used as counter decoders to define word bit length, frame word length, and paragraph frame length.

Stattel, R. J.↗
NASA NTRS1985

The number of stable points of an infinite-range spin glass memory

A rigorous asymptotic expression for the number of stable points of an infinite-range spin glass with independently identically distributed (i.i.d) zero-mean gaussian exchange interactions is discussed. The result also applies tot he number of stable points of a Hopfield Memory (a kind of associative memory) when the memory connections are i.i.d. zero-mean gaussians. The result is that the number of stable points is asymptotic to a constant slightly larger than 1 times 2 to a power slightly larger thann/4, where n is the number of spins in the glass, or the length of the n-tuples to be remembered by the memory. The answer is easily derived using simple asymptotic techniques from an exact expression for the probability that an arbitrary plus or minus 1 n-tuple of spins is a fixed point. This expression is obtained from the fact that any distribution of joint zero-mean gaussians of given covariances is specified solely by these covariances. This is a far shorter derivation of the result than those existing.

Posner, E. C.↗
NASA NTRS2005

Navier-Stokes Simulation of Airconditioning Facility of a Large Modem Computer Room

NASA recently assembled one of the world's fastest operational supercomputers to meet the agency's new high performance computing needs. This large-scale system, named Columbia, consists of 20 interconnected SGI Altix 512-processor systems, for a total of 10,240 Intel Itanium-2 processors. High-fidelity CFD simulations were performed for the NASA Advanced Supercomputing (NAS) computer room at Ames Research Center. The purpose of the simulations was to assess the adequacy of the existing air handling and conditioning system and make recommendations for changes in the design of the system if needed. The simulations were performed with NASA's OVERFLOW-2 CFD code which utilizes overset structured grids. A new set of boundary conditions were developed and added to the flow solver for modeling the roomls air-conditioning and proper cooling of the equipment. Boundary condition parameters for the flow solver are based on cooler CFM (flow rate) ratings and some reasonable assumptions of flow and heat transfer data for the floor and central processing units (CPU) . The geometry modeling from blue prints and grid generation were handled by the NASA Ames software package Chimera Grid Tools (CGT). This geometric model was developed as a CGT-scripted template, which can be easily modified to accommodate any changes in shape and size of the room, locations and dimensions of the CPU racks, disk racks, coolers, power distribution units, and mass-storage system. The compute nodes are grouped in pairs of racks with an aisle in the middle. High-speed connection cables connect the racks with overhead cable trays. The cool air from the cooling units is pumped into the computer room from a sub-floor through perforated floor tiles. The CPU cooling fans draw cool air from the floor tiles, which run along the outside length of each rack, and eject warm air into the center isle between the racks. This warm air is eventually drawn into the cooling units located near the walls of the room. One major concern is that the hot air ejected to the middle isle might recirculate back into the cool rack side and cause thermal short-cycling. The simulations analyzed and addressed the following important elements of the computer room: 1) High-temperature build-up in certain regions of the room; 2) Areas of low air circulation in the room; 3) Potential short-cycling of the computer rack cooling system; 4) Effectiveness of the perforated cooling floor tiles; 5) Effect of changes in various aspects of the cooling units. Detailed flow visualization is performed to show temperature distribution, air-flow streamlines and velocities in the computer room.

Source record↗
NASA NTRS2009

Sequential Imaging of Earth by Astronauts: 50 Years of Global Change

For nearly 50 years, astronauts have collected sequential imagery of the Earth. In fact, the collection of astronaut photography comprises one of the earliest sets of data (1961 to present) available to scientists to study the regional context of the Earth s surface and how it changes. While today s availability of global high resolution satellite imagery enables anyone with an internet connection to examine specific features on the Earth s surface with a regional context, historical satellite imagery adds another dimension (time) that provides researchers and students insight about the features and processes of a region. For example, one of the geographic areas with the longest length of record contained within the astronaut photography database is the lower Nile River. The database contains images that document the flooding of Lake Nasser (an analog to today s flooding behind China s Three Gorges Dam), the changing levels of Lake Nasser s water with multiyear cycles of flood and drought, the recent flooding and drying of the Toshka Lakes, as well as urban growth, changes in agriculture and coastal subsidence. The imagery database allows investigations using different time scales (hours to decades) and spatial scales (resolutions and fields of view) as variables. To continue the imagery collection, the astronauts on the International Space Station are trained to understand basic the Earth Sciences and look for and photograph major events such as tropical storms, landslides, and volcanic eruptions, and document landscapes undergoing change (e.g., coastal systems, cities, changing forest cover). We present examples of selected sequences of astronaut imagery that illustrate the interdependence of geological processes, climate cycles, human geography and development, and prompt additional questions about the underlying elements of change.

Evans, Cynthia A.↗
NASA NTRS2010

Current Status of the Development of a Transportable and Compact VLBI System by NICT and GSI

MARBLE (Multiple Antenna Radio-interferometer for Baseline Length Evaluation) is under development by NICT and GSI. The main part of MARBLE is a transportable VLBI system with a compact antenna. The aim of this system is to provide precise baseline length over about 10 km for calibrating baselines. The calibration baselines are used to check and validate surveying instruments such as GPS receiver and EDM (Electro-optical Distance Meter). It is necessary to examine the calibration baselines regularly to keep the quality of the validation. The VLBI technique can examine and evaluate the calibration baselines. On the other hand, the following roles are expected of a compact VLBI antenna in the VLBI2010 project. In order to achieve the challenging measurement precision of VLBI2010, it is well known that it is necessary to deal with the problem of thermal and gravitational deformation of the antenna. One promising approach may be connected-element interferometry between a compact antenna and a VLBI2010 antenna. By measuring repeatedly the baseline between the small stable antenna and the VLBI2010 antenna, the deformation of the primary antenna can be measured and the thermal and gravitational models of the primary antenna will be able to be constructed. We made two prototypes of a transportable and compact VLBI system from 2007 to 2009. We performed VLBI experiments using theses prototypes and got a baseline length between the two prototypes. The formal error of the measured baseline length was 2.7 mm. We expect that the baseline length error will be reduced by using a high-speed A/D sampler.

Ishii, Atsutoshi↗
NASA NTRS1991

A connection between long-term luminosity variations and orbital period changes in chromospherically active binaries

The eclipsing binary CG Cyg provides observational confirmation of three predictions made by Applegate's (1991) improvement on the theory that magnetic cycles cause the quasi-periodic orbital period changes in binaries containing a convective star. The mean brightness outside eclipse and the period vary with the same cycle length of about 50 yr. The light curve and O - C curve are in phase, with maximum light and period increase occurring in early 1980. The chromospherically active star becomes bluer in phase with the brightening. Because a period increase occurs at maximum brightness, the sense of the star's differential rotation is specified: outside rotating faster.

Hall, Douglas S.↗
NASA NTRS2000

Intramolecular activation of a Ca(2+)-dependent protein kinase is disrupted by insertions in the tether that connects the calmodulin-like domain to the kinase

Ca(2+)-dependent protein kinases (CDPK) have a calmodulin-like domain (CaM-LD) tethered to the C-terminal end of the kinase. Activation is proposed to involve intramolecular binding of the CaM-LD to a junction sequence that connects the CaM-LD to the kinase domain. Consistent with this model, a truncated CDPK (DeltaNC) in which the CaM-LD has been deleted can be activated in a bimolecular interaction with an isolated CaM-LD or calmodulin, similar to the activation of a calmodulin-dependent protein kinase (CaMK) by calmodulin. Here we provide genetic evidence that this bimolecular activation requires a nine-residue binding segment from F436 to I444 (numbers correspond to CPK-1 accession number L14771). Two mutations at either end of this core segment (F436/A and VI444/AA) severely disrupted bimolecular activation, whereas flanking mutations had only minor effects. Intramolecular activation of a full-length kinase was also disrupted by a VI444/AA mutation, but surprisingly not by a F436/A mutation (at the N-terminal end of the binding site). Interestingly, intramolecular but not bimolecular activation was disrupted by insertion mutations placed immediately downstream of I444. To show that mutant enzymes were not misfolded, latent kinase activity was stimulated through binding of an antijunction antibody. Results here support a model of intramolecular activation in which the tether (A445 to G455) that connects the CaM-LD to the kinase provides an important structural constraint and is not just a simple flexible connection.

NASA Discipline Plant Biology↗
NASA NTRS1974

Coaxial anode wire for gas radiation counters

The design and characteristics of a gas radiation counter are discussed. The coaxial anode consists of an elongated central wire covered with an electrically insulating sleeve. Several longitudinally discontinuous segments of an electrically conductive coating are disposed about the insulating sleeve in a coaxial pattern along the length of the central wire. The conductive coating segments form a veto or rejection anode at each end of the central wire and a main or primary charge detecting anode between the ends. The segments are coupled together so that the primary charge detecting anode is connected to detection circuitry in anti-coincidence with the veto anodes. Background radiation detected by either of the veto anodes and the primary charge detecting anode is rejected and the sensitivity of the radiation counter device is increased.

Kraushaar, W. L.↗
NASA NTRS1977

Design, fabrication and expected performance of the HEAO-B X ray telescope

The X-ray telescope of the second High Energy Astronomy Observatory (HEAO-B) is described. The design consists of four concentric paraboloid/hyperboloid pairs. Focal length is 3.44 meters, paraboloid diameters vary from 580-336 mm, grazing angles vary from 70 to 40 arcmin for paraxial rays, segment lengths are 511 mm. The reflecting surfaces are nickel-coated fused quartz and the resolution is limited by assembly errors (for small field angles) and design aberrations (for large field angles). The local slope, roundness, and surface roughness are identified as the primary optical tolerances connected with the individual elements.

Van Speybroeck, L. P.↗
NASA NTRS2012

Integrated Simulation Design Challenges to Support TPS Repair Operations

During the Orbiter Repair Maneuver (ORM) operations planned for Return to Flight (RTF), the Shuttle Remote Manipulator System (SRMS) must grapple the International Space Station (ISS), undock the Orbiter, maneuver it through a long duration trajectory, and orient it to an EVA crewman poised at the end of the Space Station Remote Manipulator System (SSRMS) to facilitate the repair of the Thermal Protection System (TPS). Once repair has been completed and confirmed, then the SRMS proceeds back through the trajectory to dock the Orbiter to the Orbiter Docking System. In order to support analysis of the complex dynamic interactions of the integrated system formed by the Orbiter, ISS, SRMS, and SSMS during the ORM, simulation tools used for previous ‘nominal’ mission support required substantial enhancements. These upgrades were necessary to provide analysts with the capabilities needed to study integrated system performance. Prevalent throughout this ORM operation is a dynamically varying topology. In other words, the ORM starts with the SRMS grappled to the mated Shuttle/ISS stack (closed loop topology), moves to an open loop chain topology consisting of the Shuttle, SRMS, and ISS, and then, at the repair configuration, extends the chain topology to one consisting of the Shuttle, SMS, ISS, and SSRMS/EVA crewman. The resulting long dynamic chain of vehicles and manipulators may exhibit significant motion between the Shuttle worksite and the EVA crewman due to the system flexibility throughout the topology (particularly within the SRMS/SSRMS joints and links). Since the attachment points of both manipulators span the flexible structure of the ISS, simulation analysis may also need to take that into consideration. Moreover, due to the lengthy time duration associated with the maneuver and repair, orbital effects become a factor and require the ISS vehicle control system to maintain active attitude control. Several facets of the ORM operation make the associated analytical efforts different from previous mission support, including: (1) the magnitude of the SRMS handled payload (Le., Orbiter class), (2) the orbital effects induced on the integrated system consisting of the large Shuttle and ISS masses connected by a light flexible SRMS, (3) long duration environmental consequences due to the lengthy operational times associated with the maneuver and repair of the TPS, (4) active attitude control (as opposed to free drift) interacting with the SRMS and SSRMS manipulators (also due to the length of the maneuver and repair), (5) relative dynamics between the EVA crewman and thc worksite influenced by the extended flexible topology. In order to meet these analysis challenges, an ORM simulation architecture was developed leveraging upon numerous pre-existing simulation elements to analyze the various subsystems individually. For example, core manipulator subsystem simulations for both the SRMS and SSRMS were originally combined to provide the dual-arm dynamics topology simulation (in the absence of orbital dynamics and vehicle control). This capability was later merged with the simulation used to analyze SRMS loading with a heavy payload in the orbital environment with an active payload control system (in this case, the ISS Attitude Control System (ACS)), configured for the ORM. The resulting worksite dynamics simulation, based off of the modified ORM simulation, provided the extended topological chain of vehicles and manipulators, while taking into account the orbital effects of both the Shuttle and ISS (as well as its ACS). Verification and validation (V&V) of these integrated simulations became a challenge in itself. A systematic approach needed to be developed such that integration simulation results could be tested against previous constituent simulations upon which these simulations were built. General V&V categories included: (1) core orbital state propagation, (2), stand-alone SRMS, (3) stand-alone SSRMS, (4) stand-alone ISS ACS, (5) integrated Shuttle, SRMS, ISS (with active ACS) in the orbital environment, and (5) dual-arm SRMS/SSRMS dynamics topology. Integrated simulation V&V run suites were created and correlated to verification runs from subsystem simulations, in order to establish the validity of the results. This paper discusses the simulation design challenges encountered while developing simulation capabilities to mirror the ORM operations. The paper also describes the incremental build approach that was utilized, starting with the subsystem simulation elements and integration into increasing more complex simulations until the resulting ORM worksite dynamics simulation had been assembled. Furthermore, the paper presents an overall integrated simulation V&V methodology based upon a subsystem level testing, integrated comparisons, and phased checkout.

Thermal Protection System↗
NASA NTRS2013

Miniature Sensor Probe for O2, CO2, and H2O Monitoring in Portable Life Support Systems

A miniature sensor probe, composed of four sensors which monitor the partial pressure of O2, CO2, H2O, and temperature, designed to operate in the portable life support system (PLSS), has been demonstrated. The probe provides an important advantage over existing technology in that it is able to operate reliably while wet. These luminescence-based fiber optic sensors consist of an indicator chemistry immobilized in a polymeric film, whose emission lifetime undergoes a strong change upon a reversible interaction with the target gas. Each sensor includes chemistry specifically sensitive to one target parameter. All four sensors are based on indicator chemistries that include luminescent dyes from the same chemical family, and therefore exhibit similar photochemical properties, which allow performing measurements of all the sensors by a single, compact, low-power optoelectronic unit remotely connected to the sensors by an electromagnetic interference-proof optical fiber cable. For space systems, using these miniature sensor elements with remote optoelectronics provides unmatched design flexibility for measurements in highly constrained volume systems such as the PLSS. A 10 mm diameter and 15 mm length prototype multiparameter probe was designed, fabricated, tested, and demonstrated over a wide operational range of gas concentration, humidity, and temperature relevant to operation in the PLSS. The sensors were evaluated for measurement range, precision, accuracy, and response time in temperatures ranging from 50 aF-150 aF and relative humidity from dry to 100% RH. Operation of the sensors in water condensation conditions was demonstrated wherein the sensors not only tolerated liquid water but actually operated while wet.

Delgado, Jesus↗
NASA NTRS2000

Tubular Coupling

A system for coupling a vascular overflow graft or cannula to a heart pump. A pump pipe outlet is provided with an external tapered surface which receives the end of a compressible connula. An annular compression ring with a tapered internal bore surface is arranged about the cannula with the tapered internal surface in a facing relationship to the external tapered surface. The angle of inclination of the tapered surfaces is converging such that the spacing between the tapered surfaces decreases from one end of the external tapered surface to the other end thereby providing a clamping action of the tapered surface on a cannula which increases as a function of the length of cannula segment between the tapered surfaces. The annular compression ring is disposed within a tubular locking nut which threadedly couples to the pump and provides a compression force for urging the annular ring onto the cannula between the tapered surfaces. The nut has a threaded connection to the pump body. The threaded coupling to the pump body provides a compression force for the annular ring. The annular ring has an annular enclosure space in which excess cannula material from the compression between the tapered surfaces to "bunch up" in the space and serve as an enlarged annular ring segment to assist holding the cannula in place. The clamped cannula provides a seamless joint connection to the pump pipe outlet where the clamping force is uniformly applied to the cannula because of self alignment of the tapered surfaces. The nut can be easily disconnected to replace the pump if necessary.

Rosenbaum, Bernard J.↗
NASA NTRS2016

Hot-Fire Test Results of Liquid Oxygen/RP-2 Multi-Element Oxidizer-Rich Preburners

As part of the Combustion Stability Tool Development project funded by the Air Force Space and Missile Systems Center, the NASA Marshall Space Flight Center was contracted to assemble and hot-fire test a multi-element integrated test article demonstrating combustion characteristics of an oxygen/hydrocarbon propellant oxidizer-rich staged-combustion engine thrust chamber. Such a test article simulates flow through the main injectors of oxygen/kerosene oxidizer-rich staged combustion engines such as the Russian RD-180 or NK-33 engines, or future U.S.-built engine systems such as the Aerojet-Rocketdyne AR-1 engine or the Hydrocarbon Boost program demonstration engine. To supply the oxidizer-rich combustion products to the main injector of the integrated test article, existing subscale preburner injectors from a previous NASA-funded oxidizer-rich staged combustion engine development program were utilized. For the integrated test article, existing and newly designed and fabricated inter-connecting hot gas duct hardware were used to supply the oxidizer-rich combustion products to the oxidizer circuit of the main injector of the thrust chamber. However, before one of the preburners was used in the integrated test article, it was first hot-fire tested at length to prove it could provide the hot exhaust gas mean temperature, thermal uniformity and combustion stability necessary to perform in the integrated test article experiment. This paper presents results from hot-fire testing of several preburner injectors in a representative combustion chamber with a sonic throat. Hydraulic, combustion performance, exhaust gas thermal uniformity, and combustion stability data are presented. Results from combustion stability modeling of these test results are described in a companion paper at this JANNAF conference, while hot-fire test results of the preburner injector in the integrated test article are described in another companion paper.

Protz, C. S.↗
NASA NTRS2019

Interannual Oscillations in Earth Rotation

At seasonal and shorter time scales, polar motion and length‐of‐day (LOD) change are dominated by mass redistribution in the Earth climate system, including the atmosphere, oceans, and hydrosphere. Long‐term polar motion and LOD change are believed to be forced by solid Earth geophysical process, such as glacial isostatic adjustment. Decadal LOD variations are also connected to core‐mantle coupling. This study provides a comprehensive analysis of interannual oscillations in all three components of Earth rotation using accurately measured polar motion and LOD time series, and geophysical excitations computed from atmospheric, oceanic, and hydrological models over the period 1962 to 2018. Strong interannual oscillations remain in all three components after detrending and band‐pass filtering to retain variations at periods between 2 and 8 years. Polar motion Y is dominated by a 3.65‐year oscillation, plus others at periods of 2.5 and 5.9 years. Polar motion X shows a strong oscillation near 5.9 years, plus smaller variations at shorter periods. A 5.9‐year LOD variation has been recognized in earlier studies, but oscillations at periods of 2.36, 3.65, and 4.9 years are also observed. Atmosphere, ocean, and hydrosphere (AOH) sources largely account for 2.5‐ and 3.65‐year components in polar motion Y, but not for the 5.9‐year component in polar motion X and Y. The 2.36‐, 3.65‐, and 4.9‐year components in LOD can largely be accounted for by AOH sources. The 5.9‐year LOD component becomes more prominent after AOH sources have been subtracted. The presence of a 5.9‐year variation in all three components of Earth rotation suggests a source in Earth's interior, probably from the core.

Jianli Chen↗