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NASA NTRS2015

NASA Manufacturing and Test Requirements for Normally Closed Pyrovalves for Hazardous Flight Systems Applications

Pyrovalves (figure 1, Basic Pyrovalve Design and Features,) are typically lighter, more reliable, and in most cases less expensive than other types of valves. They also consume less electrical power. They are single-use devices that are used in propulsion systems to isolate propellants or pressurant gases. These fluids may be hazardous because of their toxicity, reactivity, temperature, or high pressure. Note that in the simplified block diagram below not all detail features are shown so that those of major interest are more prominent. The diagram is provided to point out the various features that are discussed in this Specification. Features of some NC parent metal valve designs may differ. In 2013, the NESC concluded an extensive study of the reliability and safety of NC parent metal valves used in payloads carried aboard ELVs. The assessment successfully evaluated technical data to determine the risk of NC parent metal valve leakage or inadvertent activation in ELV payloads. The study resulted in numerous recommendations to ensure personnel and hardware/facility safety during ground processing of ELV payloads. One of those recommendations was to establish a NASA specification for NC parent metal valves. This Specification is a result of that recommendation, which is documented in NESC-RP-10-00614.

McDougle, Stephen H.↗

NASA NTRS2017

Hover Performance of Isolated Proprotors and Propellers - Experimental Data

The use of Computational Fluid Dynamics (CFD) is gaining momentum within the aeronautical community. A relatively small segment of this community is applying CFD technology in the prediction of VSTOL aircraft performance. An even smaller group of engineers are refining and applying fluid dynamics solvers to the problem of predicting hover performance of helicopter rotors and proprotors designed by rotorcraft advocates. This small group of CFD engineers who are attacking the hover performance problem have, today, been using a quite limited experimental data base upon which to demonstrate their progress. This is because their concentration has been on only two successful tiltrotor flying; namely the XV-15 and the MV-22B. No attention appears (as yet) to be directed at the CL-84 or the XC-142A. The purpose of this report is to expand the experimental data base of both proprotors and propellers so that comparisons of test and various theories can be made to several more configurations of these propulsive devices used by VSTOL aircraft.

Hover↗

NASA NTRS1983

Using second-sound shock waves to probe the intrinsic critical velocity of liquid helium II

A critical velocity truly intrinsic to liquid helium II is experimentally sought in the bulk fluid far from the apparatus walls. Termed the 'fundamental critical velocity,' it necessarily is caused by mutual interactions which operate between the two fluid components and which are activated at large relative velocities. It is argued that flow induced by second-sound shock waves provides the ideal means by which to activate and isolate the fundamental critical velocity from other extraneous fluid-wall interactions. Experimentally it is found that large-amplitude second-sound shock waves initiate a breakdown in the superfluidity of helium II, which is dramatically manifested as a limit to the maximum attainable shock strength. This breakdown is shown to be caused by a fundamental critical velocity. Secondary effects include boiling for ambient pressures near the saturated vapor pressure or the formation of helium I boundary layers at higher ambient pressures. When compared to the intrinsic critical velocity discovered in highly restricted geometries, the shock-induced critical velocity displays a similar temperature dependence and is the same order of magnitude.

Turner, T. N.↗

NASA NTRS1984

Heat transfer effects of longitudinal vortices embedded in a turbulent boundary layer

The results of tests with five different vortex generators in an open circuit wind tunnel are reported. The tests were performed to enhance the data base on heat transfer effects of an isolated longitudinal vortex in a turbulent boundary layer and the effects of embedded vortex pairs. A heated plate was set in the boundary layer downstream of a tripping mechanism and measurements were made of the free stream and surface temperatures using thermocouples. A four-hole cobra probe assayed the velocity profiles. Trials revealed that vortex pairs with scales larger than the boundary layer thickness induce significant changes in the Stanton number. A 15 percent Stanton number increase was produced by isolated vortices, which swept cool free stream fluid into the near-wall region.

Eibeck, P. A.↗

NASA NTRS1992

New inertial actuator provides isolation and stabilization in microgravity conditions

Experiments in materials and fluids processing have been conducted, or are planned, that take advantage of the low-g environment offered by space-based platforms. While the specific goals of the experiments vary, a common objective is to see improved results from the processes over those that would be obtained from similar ground-based experiments. While the space-based processing environment does offer a low-g environment, it is not disturbance free. Results of experiments already conducted, particularly those in manned vehicles, show that spacecraft induced disturbances still limit what can be achieved in materials processing. The duration of actual micro-g level environments is shorter than desired and periods of milli-g activity levels are not uncommon. While small scale experiments can be configured to overcome some of the vehicle disturbance sources, larger scale processing devices and commercial activities will require alternative methods to reduce the influences of spacecraft vibrations. Applied Technology Associates, Inc., (ATA), in cooperation with NASA Lewis Research Center, is developing hardware to provide a sustained micro-g experiment environment. This work is being sponsored under a Small Business Innovation Research (SBIR) program, which is currently in the Phase 2 development stage. ATA's approach is based on an inertial actuator, which when used as part of a closed-loop stabilization system, rejects unwanted disturbances to the experiment package. A prototype of the actuator has been fabricated and used in a laboratory demonstration to prove the principle of operation. ATA's presentation emphasized the development and testing of the Digital Materials Processing Experiment (DAMPER) inertial actuator. Physical and performance characteristics of the device are presented. Technical issues, including further optimization of the actuator's performance and plans for additional laboratory experiments, are also covered.

Blackburn, John↗

NASA NTRS1997

Remote Sensing of Dipole Rings

Historical satellite-derived sea surface temperature (SST) data are reanalyzed with a zebra color palette and a thermal separatrix method. The new results from this reanalysis are as follows: (a) Thirteen observational sequences of six rings from the Gulf Stream and the Brazil Current, which have historically been interpreted as solitary vortices or monopoles are shown to have a dipolar character; (b) some of these dipole rings have been observed in the open ocean, thereby eliminating the possibility that they are sustained by topographic interactions with the continental slope; (c) whether interacting with other features or evolving as isolated circulations, dipoles are seen to rotate within a relatively narrow range of approximately 4-8 deg/day (interacting) and 10-11 deg/day (isolated); and (d) feature tracking delineates energetic fluid in both vortices and eliminates the possibility of interpreting dipole rings as transient features produced by active monopoles and patches of entrained fluid.

Hooker, Stanford B.↗

NASA NTRS2010

Design and Testing of an Active Heat Rejection Radiator with Digital Turn-Down Capability

NASA's proposed lunar lander, Altair, will be exposed to vastly different external environment temperatures. The challenges to the active thermal control system (ATCS) are compounded by unfavorable transients in the internal waste heat dissipation profile: the lowest heat load occurs in the coldest environment while peak loads coincide with the warmest environment. The current baseline for this fluid is a 50/50 inhibited propylene glycol/water mixture with a freeze temperature around -35 C. While the overall size of the radiator's heat rejection area is dictated by the worst case hot scenario, a turn-down feature is necessary to tolerate the worst case cold scenario. A radiator with digital turn-down capability is being designed as a robust means to maintain cabin environment and equipment temperatures while minimizing mass and power consumption. It utilizes active valving to isolate and render ineffective any number of parallel flow tubes which span across the ATCS radiator. Several options were assessed in a trade-study to accommodate flow tube isolation and how to deal with the stagnant fluid that would otherwise remain in the tube. Bread-board environmental tests were conducted for options to drain the fluid from a turned-down leg as well an option to allow a leg to freeze/thaw. Each drain option involved a positive displacement gear pump with different methods of providing a pressure head to feed it. Test results showed that a start-up heater used to generate vapor at the tube inlet held the most promise for tube evacuation. Based on these test results and conclusions drawn from the trade-study, a full-scale radiator design is being worked for the Altair mission profile.

Sunada, Eric↗

NASA NTRS2011

Two-axis direct fluid shear stress sensor

A micro sized multi-axis semiconductor skin friction/wall shear stress induced by fluid flow. The sensor design includes a shear/strain transduction gimble connected to a force collecting plate located at the flow boundary surface. The shear force collecting plate is interconnected by an arm to offset the tortional hinges from the fluid flow. The arm is connected to the shear force collecting plate through dual axis torsional hinges with piezoresistive torsional strain gauges. These gauges are disposed on the tortional hinges and provide a voltage output indicative of applied shear stress acting on the force collection plate proximate the flow boundary surface. Offsetting the torsional hinges creates a force concentration and resolution structure that enables the generation of a large stress on the strain gauge from small shear stress, or small displacement of the collecting plate. The design also isolates the torsional sensors from exposure to the fluid flow.

Bajikar, Sateesh↗

NASA NTRS1995

A well-posed numerical method to track isolated conformal map singularities in Hele-Shaw flow

We present a new numerical method for calculating an evolving 2D Hele-Shaw interface when surface tension effects are neglected. In the case where the flow is directed from the less viscous fluid into the more viscous fluid, the motion of the interface is ill-posed; small deviations in the initial condition will produce significant changes in the ensuing motion. This situation is disastrous for numerical computation, as small round-off errors can quickly lead to large inaccuracies in the computed solution. Our method of computation is most easily formulated using a conformal map from the fluid domain into a unit disk. The method relies on analytically continuing the initial data and equations of motion into the region exterior to the disk, where the evolution problem becomes well-posed. The equations are then numerically solved in the extended domain. The presence of singularities in the conformal map outside of the disk introduces specific structures along the fluid interface. Our method can explicitly track the location of isolated pole and branch point singularities, allowing us to draw connections between the development of interfacial patterns and the motion of singularities as they approach the unit disk. In particular, we are able to relate physical features such as finger shape, side-branch formation, and competition between fingers to the nature and location of the singularities. The usefulness of this method in studying the formation of topological singularities (self-intersections of the interface) is also pointed out.

Baker, Gregory↗

NASA NTRS1997

The Development of a Tool for Semi-Automated Generation of Structured and Unstructured Grids about Isolated Rotorcraft Blades

The grid generation used to model rotorcraft configurations for Computational Fluid Dynamics (CFD) analysis is highly complicated and time consuming. The highly complex geometry and irregular shapes encountered in entire rotorcraft configurations are typically modeled using overset grids. Another promising approach is to utilize unstructured grid methods. With either approach the majority of time is spent manually setting up the topology. For less complicated geometries such as isolated rotor blades, less time is obviously required. This paper discusses the capabilities of a tool called Rotor blade Optimized Topology Organizer and Renderer(ROTOR) being developed to quickly generate block structured grids and unstructured tetrahedral grids about isolated blades. The key algorithm uses individual airfoil sections to construct a Non-Uniform Rational B-Spline(NURBS) surface representation of the rotor blade. This continuous surface definition can be queried to define the block topology used in constructing a structured mesh around the rotor blade. Alternatively, the surface definition can be used to define the surface patches and grid cell spacing requirements for generating unstructured surface and volume grids. Presently, the primary output for ROTOR is block structured grids using 0-H and H-H topologies suitable for full-potential solvers. This paper will discuss the present capabilities of the tool and highlight future work.

Shanmugasundaram, Ramakrishnan↗

NASA NTRS1987

Protecting a Ball-Bearing-Deflection Monitor

Deflectometer probe monitors deflection of ball-bearing race in liquid oxygen with aid of small window or diaphragm. Diaphragm or window isolates optical deflectometer from liquid oxygen or other fluid in ball bearing. At high pressures, diaphragm integral part of housing preferable to window, since there would be no leakage.

Kuhr, George A.↗

NASA NTRS1999

Investigation of the Influence of Microgravity on Transport Mechanism in a Virtual Spaceflight Chamber: A Flight Definition Program

A need exists for understanding precisely how particles move and interact in a fluid in the absence of gravity. Such understanding is required, for example, for modeling and predicting crystal growth in space where crystals grow from solution around nucleation sites as well as for any study of particles or bubbles in liquids or in experiments where particles are used as tracers for mapping microconvection. We have produced an exact solution to the general equation of motion of particles at extremely low Reynolds number in microgravity that covers a wide range of interesting conditions. We have also developed diagnostic tools and experimental techniques to test the validity of the general equation . This program, which started in May, 1998, will produce the flight definition for an experiment in a microgravity environment of space to validate the theoretical model. We will design an experiment with the help of the theoretical model that is optimized for testing the model, measuring g, g-jitter, and other microgravity phenomena. This paper describes the goals, rational, and approach for the flight definition program. The first objective of this research is to understand the physics of particle interactions with fluids and other particles in low Reynolds number flows in microgravity. Secondary objectives are to (1) observe and quantify g-jitter effects and microconvection on particles in fluids, (2) validate an exact solution to the general equation of motion of a particle in a fluid, and (3) to characterize the ability of isolation tables to isolate experiments containing particle in liquids. The objectives will be achieved by recording a large number of holograms of particle fields in microgravity under controlled conditions, extracting the precise three-dimensional position of all of the particles as a function of time and examining the effects of all parameters on the motion of the particles. The feasibility for achieving these results has already been established in the ongoing ground-based NRA, which led to the "virtual spaceflight chamber" concept.

Trolinger, James D.↗

NASA NTRS2016

High-pressure sensor using piezoelectric bending resonators

A novel design of pressure sensor based on piezoelectric bending resonator is described in this paper. The resonator is isolated from and mechanically coupled to the surrounding fluid using a sealed enclosure. The pressure applied to the enclosure induces a compressive stress to the resonator and reduces its resonance frequency. In principle the mechanism allows for achieving large resonance frequency shifts close to 100% of the resonance frequency. A high-pressure sensor based on the mechanism was designed for down-hole pressure monitoring in oil wells. The sensor is potentially remotely-readable via the transmission of an electromagnetic signal down a waveguide formed by the pipes in the oil well. The details of the pressure sensor design and verification by FE analysis and initial test results of a preliminary prototype are presented in this paper.

Takano, Nobuyuki↗

NASA NTRSDate not supplied

Astrobee: Improving Capabilities for Free Flying Robotic Technology Demonstrations

The Astrobee Project has completed three years operating inside the ISS. Three Astrobee Free Flyers reached the ISS in April 2019 and are currently hosting a variety of users. During this time, Astrobee has advanced the state of the art in free-flying robots on ISS, operated over 100 sessions, logged over 750 hours of free-flyer operation, and made several capability improvements. Astrobee’s primary objective is to provide a highly flexible and capable free-flying robotic research platform to enable future guest scientist investigations. However, Astrobee is also demonstrating the feasibility of intra-vehicular robots (IVR) for performing key caretaking functions within exploration vehicles as part of NASA’s Moon-to-Mars exploration strategy. IVR capabilities will be especially vital during uncrewed mission phases. For example, current plans call for the lunar Gateway to be uncrewed >85% of the time. Astrobee’s baseline implementation supports free-flying camera and sensor survey use cases. Astrobee guest scientists can deploy software updates and hardware payloads to extend its capabilities. Astrobee is continuously improving its navigation robustness, general flight software maturity, and ISS interior maps, both through the baseline Astrobee operations and with the help of the ISAAC project. Astrobee began with mapping, localization, and operations in the Japanese Experiment Module (JEM), and has expanded to mapping in Node 2 and the US Lab. Astrobee has improved localization and operational robustness through improved mapping processes, algorithm updates (Soussan 2022) that reduce the occurrences of lost localization as well as developed recovery techniques to return to a good localization fix when loss of localization does occur. Future guest science experiments currently in development could demonstrate cargo transfer, fault isolation, free flyer and stationary robot collaboration, microgravity fluid transfer, and new docking mechanisms, among others. This presentation will focus on 1) Astrobee technical capabilities 2) What Astrobee can provide to a guest science experiment 3) Astrobee’s recent improvements 4) Possibilities for using Astrobee for future investigations. Soussan, R., Kumar, V., Coltin, B. and Smith, T. (2022) AstroLoc: An Efficient and Robust Localizer for a Free-flying Robot, Proc. Int. Conf. Rob. Autom. (ICRA) [to appear]

Astrobee↗

NASA NTRS2022

Reversible Colorimetric Sensing of Volatile Analytes By Wicking in Close Proximity to A Photonic Film

Isolation of volatile analytes from environmental or biological fluids is a rate-determining step that can delay the response time for continuous sensing. In this paper, we demonstrate a colorimetric sensing system that enables the rapid detection of gas-phase analytes released from a flowing micro-volume fluid sample. The sensor platform is an analyte-responsive metal-insulator-metal (MIM) thin-film structure integrated with a large area quartz micropillar array. This allows precise planar alignment and microscale separation (310 μm) of the optical and fluidic structures. This configuration offers rapid and homogeneous color changes over large areas that permits detection by low-resolution optics or eye, which is well-suited to portable/wearable devices. For our proof-of-principle demonstration, we utilized a poly(methyl methacrylate) (PMMA) spacer and evaluated the sensor's response (color change) to ethanol vapor. We show that the RGB color value is quantitatively linked to the spacer swelling, which is reversible and repeatable. The optofluidic platform reduces the sensor response time from minutes to seconds compared with experiments using a conventional chamber. The sensor's concentration-dependent response was examined, confirming the potential of the reported sensing platform for continuous, compact, and quantitative colorimetric analysis of volatile analytes in low-volume samples, such as biofluids.

Timothy J. Palinski↗

NASA NTRS1987

Workshop on Structural Dynamics and Control Interaction of Flexible Structures

The Hubble Space Telescope features the most exacting line of sight jitter requirement thus far imposed on a spacecraft pointing system. Consideration of the fine pointing requirements prompted an attempt to isolate the telescope from the low level vibration disturbances generated by the attitude control system reaction wheels. The primary goal was to provide isolation from axial component of wheel disturbance without compromising the control system bandwidth. A passive isolation system employing metal springs in parallel with viscous fluid dampers was designed, fabricated, and space qualified. Stiffness and damping characteristics are deterministic, controlled independently, and were demonstrated to remain constant over at least five orders of input disturbance magnitude. The damping remained purely viscous even at the data collection threshold of .16 x .000001 in input displacement, a level much lower than the anticipated Hubble Space Telescope disturbance amplitude. Vibration attenuation goals were obtained and ground test of the vehicle has demonstrated the isolators are transparent to the attitude control system.

Davis, L. P.↗

NASA NTRS2011

CO2 Insulation for Thermal Control of the Mars Science Laboratory

The National Aeronautics and Space Administration (NASA) is sending a large (>850 kg) rover as part of the Mars Science Laboratory (MSL) mission to Mars in 2011. The rover's primary power source is a Multi-Mission Radioisotope Thermoelectric Generator (MMRTG) that generates roughly 2000 W of heat, which is converted to approximately 110 W of electrical power for use by the rover electronics, science instruments, and mechanism-actuators. The large rover size and extreme thermal environments (cold and hot) for which the rover is designed for led to a sophisticated thermal control system to keep it within allowable temperature limits. The pre-existing Martian atmosphere of low thermal conductivity CO2 gas (8 Torr) is used to thermally protect the rover and its components from the extremely cold Martian environment (temperatures as low as -130 deg C). Conventional vacuum based insulation like Multi Layer Insulation (MLI) is not effective in a gaseous atmosphere, so engineered gaps between the warm rover internal components and the cold rover external structure were employed to implement this thermal isolation. Large gaps would lead to more thermal isolation, but would also require more of the precious volume available within the rover. Therefore, a balance of the degree of thermal isolation achieved vs. the volume of rover utilized is required to reach an acceptable design. The temperature differences between the controlled components and the rover structure vary from location to location so each gap has to be evaluated on a case-by-case basis to arrive at an optimal thickness. For every configuration and temperature difference, there is a critical thickness below which the heat transfer mechanism is dominated by simple gaseous thermal conduction. For larger gaps, the mechanism is dominated by natural convection. In general, convection leads to a poorer level of thermal isolation as compared to conduction. All these considerations play important roles in the optimization process. A three-step process was utilized to design this insulation. The first step is to come up with a simple, textbook based, closed-form equation assessment of gap thickness vs. resultant thermal isolation achieved. The second step is a more sophisticated numerical assessment using Computational Fluid Dynamics (CFD) software to investigate the effect of complicated geometries and temperature contours along them to arrive at the effective thermal isolation in a CO2 atmosphere. The third step is to test samples of representative geometries in a CO2 filled chamber to measure the thermal isolation achieved. The results of these assessments along with the consistency checks across these methods leads to the formulation of design-guidelines for gap implementation within the rover geometry. Finally, based on the geometric and functional constraints within the real rover system, a detailed design that accommodates all these factors is arrived at. This paper will describe in detail this entire process, the results of these assessments and the final design that was implemented.

CO2↗

NASA NTRS1986

Fluid flow meter for measuring the rate of fluid flow in a conduit

A tube fluid flow rate meter consists of a reservoir divided by flexible diaphragm into two separate isolated compartments. The incoming and outgoing tubes open into the compartments. The orifice is sized to allow maximum tube fluid flow. Opposing compression springs are secured within the two compartments on opposite sides of the orifice to maintain orifice position when the tube fluid pressure is zero. A tapered element is centered in, and extends through the orifice into the compartment, leaving an annular opening between the element and the perimeter of the oriface. The size varies as the diaphragm flexes with changes in the tube fluid pressure to change the fluid flow through the opening. The light source directs light upon the element which in turn scatters the light through the opening into the compartment. The light detector in the compartment senses the scattered light to generate a signal indicating the amount of fluid.

White, P. R.↗