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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 1,009 records · Page 56
All sourcesNASA NTRSDOE OSTI
NASA NTRS2007

Mission Operations of the Mars Exploration Rovers

A document describes a system of processes involved in planning, commanding, and monitoring operations of the rovers Spirit and Opportunity of the Mars Exploration Rover mission. The system is designed to minimize command turnaround time, given that inherent uncertainties in terrain conditions and in successful completion of planned landed spacecraft motions preclude planning of some spacecraft activities until the results of prior activities are known by the ground-based operations team. The processes are partitioned into those (designated as tactical) that must be tied to the Martian clock and those (designated strategic) that can, without loss, be completed in a more leisurely fashion. The tactical processes include assessment of downlinked data, refinement and validation of activity plans, sequencing of commands, and integration and validation of sequences. Strategic processes include communications planning and generation of long-term activity plans. The primary benefit of this partition is to enable the tactical portion of the team to focus solely on tasks that contribute directly to meeting the deadlines for commanding the rover s each sol (1 sol = 1 Martian day) - achieving a turnaround time of 18 hours or less, while facilitating strategic team interactions with other organizations that do not work on a Mars time schedule.

Bass, Deborah↗
NASA NTRS2010

A Minimax Network Flow Model for Characterizing the Impact of Slot Restrictions

This paper proposes a model for evaluating long-term measures to reduce congestion at airports in the National Airspace System (NAS). This model is constructed with the goal of assessing the global impacts of congestion management strategies, specifically slot restrictions. We develop the Minimax Node Throughput Problem (MINNTHRU), a multicommodity network flow model that provides insight into air traffic patterns when one minimizes the worst-case operation across all airports in a given network. MINNTHRU is thus formulated as a model where congestion arises from network topology. It reflects not market-driven airline objectives, but those of a regulatory authority seeking a distribution of air traffic beneficial to all airports, in response to congestion management measures. After discussing an algorithm for solving MINNTHRU for moderate-sized (30 nodes) and larger networks, we use this model to study the impacts of slot restrictions on the operation of an entire hub-spoke airport network. For both a small example network and a medium-sized network based on 30 airports in the NAS, we use MINNTHRU to demonstrate that increasing the severity of slot restrictions increases the traffic around unconstrained hub airports as well as the worst-case level of operation over all airports.

Lee, Douglas W.↗
NASA NTRS2009

Building a Formal Model of a Human-Interactive System: Insights into the Integration of Formal Methods and Human Factors Engineering

Both the human factors engineering (HFE) and formal methods communities are concerned with finding and eliminating problems with safety-critical systems. This work discusses a modeling effort that leveraged methods from both fields to use model checking with HFE practices to perform formal verification of a human-interactive system. Despite the use of a seemingly simple target system, a patient controlled analgesia pump, the initial model proved to be difficult for the model checker to verify in a reasonable amount of time. This resulted in a number of model revisions that affected the HFE architectural, representativeness, and understandability goals of the effort. If formal methods are to meet the needs of the HFE community, additional modeling tools and technological developments are necessary.

Bolton, Matthew L.↗
NASA NTRS2006

Airport Remote Tower Sensor Systems

Networks of video cameras, meteorological sensors, and ancillary electronic equipment are under development in collaboration among NASA Ames Research Center, the Federal Aviation Administration (FAA), and the National Oceanic Atmospheric Administration (NOAA). These networks are to be established at and near airports to provide real-time information on local weather conditions that affect aircraft approaches and landings. The prototype network is an airport-approach-zone camera system (AAZCS), which has been deployed at San Francisco International Airport (SFO) and San Carlos Airport (SQL). The AAZCS includes remotely controlled color video cameras located on top of SFO and SQL air-traffic control towers. The cameras are controlled by the NOAA Center Weather Service Unit located at the Oakland Air Route Traffic Control Center and are accessible via a secure Web site. The AAZCS cameras can be zoomed and can be panned and tilted to cover a field of view 220 wide. The NOAA observer can see the sky condition as it is changing, thereby making possible a real-time evaluation of the conditions along the approach zones of SFO and SQL. The next-generation network, denoted a remote tower sensor system (RTSS), will soon be deployed at the Half Moon Bay Airport and a version of it will eventually be deployed at Los Angeles International Airport. In addition to remote control of video cameras via secure Web links, the RTSS offers realtime weather observations, remote sensing, portability, and a capability for deployment at remote and uninhabited sites. The RTSS can be used at airports that lack control towers, as well as at major airport hubs, to provide synthetic augmentation of vision for both local and remote operations under what would otherwise be conditions of low or even zero visibility.

Maluf, David A.↗
NASA NTRS2005

PCM Passive Cooling System Containing Active Subsystems

A multistage system has been proposed for cooling a circulating fluid that is subject to intermittent intense heating. The system would be both flexible and redundant in that it could operate in a basic passive mode, either sequentially or simultaneously with operation of a first, active cooling subsystem, and either sequentially or simultaneously with a second cooling subsystem that could be active, passive, or a combination of both. This flexibility and redundancy, in combination with the passive nature of at least one of the modes of operation, would make the system more reliable, relative to a conventional cooling system. The system would include a tube-in-shell heat exchanger, within which the space between the tubes would be filled with a phase-change material (PCM). The circulating hot fluid would flow along the tubes in the heat exchanger. In the basic passive mode of operation, heat would be conducted from the hot fluid into the PCM, wherein the heat would be stored temporarily by virtue of the phase change.

Blanding, David E.↗
NASA NTRS2012

Overview of a Preliminary Destination Mission Concept for a Human Orbital Mission to the Martial Moons

The National Aeronautics and Space Administration s Human Spaceflight Architecture Team (HAT) has been developing a preliminary Destination Mission Concept (DMC) to assess how a human orbital mission to one or both of the Martian moons, Phobos and Deimos, might be conducted as a follow-on to a human mission to a near-Earth asteroid (NEA) and as a possible preliminary step prior to a human landing on Mars. The HAT Mars-Phobos-Deimos (MPD) mission also permits the teleoperation of robotic systems by the crew while in the Mars system. The DMC development activity provides an initial effort to identify the science and exploration objectives and investigate the capabilities and operations concepts required for a human orbital mission to the Mars system. In addition, the MPD Team identified potential synergistic opportunities via prior exploration of other destinations currently under consideration.

Mazanek, D. D.↗
NASA NTRS2012

Is Mars Sample Return Required Prior to Sending Humans to Mars?

Prior to potentially sending humans to the surface of Mars, it is fundamentally important to return samples from Mars. Analysis in Earth's extensive scientific laboratories would significantly reduce the risk of human Mars exploration and would also support the science and engineering decisions relating to the Mars human flight architecture. The importance of measurements of any returned Mars samples range from critical to desirable, and in all cases these samples will would enhance our understanding of the Martian environment before potentially sending humans to that alien locale. For example, Mars sample return (MSR) could yield information that would enable human exploration related to 1) enabling forward and back planetary protection, 2) characterizing properties of Martian materials relevant for in situ resource utilization (ISRU), 3) assessing any toxicity of Martian materials with respect to human health and performance, and 4) identifying information related to engineering surface hazards such as the corrosive effect of the Martian environment. In addition, MSR would be engineering 'proof of concept' for a potential round trip human mission to the planet, and a potential model for international Mars exploration.

biohazards↗
NASA NTRS2016

RotCFD Analysis of the AH-56 Cheyenne Hub Drag

In 2016, the U.S. Army Aviation Development Directorate (ADD) conducted tests in the U.S. Army 7- by 10- Foot Wind Tunnel at NASA Ames Research Center of a nonrotating 2/5th-scale AH-56 rotor hub. The objective of the tests was to determine how removing the mechanical control gyro affected the drag. Data for the lift, drag, and pitching moment were recorded for the 4-bladed rotor hub in various hardware configurations, azimuth angles, and angles of attack. Numerical simulations of a selection of the configurations and orientations were then performed, and the results were compared with the test data. To generate the simulation results, the hardware configurations were modeled using Creo and Rhinoceros 5, three-dimensional surface modeling computer-aided design (CAD) programs. The CAD model was imported into Rotorcraft Computational Fluid Dynamics (RotCFD), a computational fluid dynamics (CFD) tool used for analyzing rotor flow fields. RotCFD simulation results were compared with the experimental results of three hardware configurations at two azimuth angles, two angles of attack, and with and without wind tunnel walls. The results help validate RotCFD as a tool for analyzing low-drag rotor hub designs for advanced high-speed rotorcraft concepts. Future work will involve simulating additional hub geometries to reduce drag or tailor to other desired performance levels.

AH-56 Cheyenne↗
NASA NTRS2017

Scientific Investigations Associated with the Human Exploration of Mars in the Next 35 Years

A human mission to Mars would present an unprecedented opportunity to investigate the earliest history of the solar system. This history that has largely been overwritten on Earth by active geological processing throughout its history, but on Mars, large swaths of the ancient crust remain exposed at the surface, allowing us to investigate martian processes at the earliest time periods when life first appeared on the Earth. Mars' surface has been largely frozen in place for 4 billion years, and after losing its atmosphere and magnetic field what re-mains is an ancient landscape of former hydrothermal systems, river beds, volcanic eruptions, and impact craters. This allows us to investigate scientific questions ranging from the nature of the impact history of the solar system to the origins of life. We present here a summary of the findings of the Human Science Objectives Science Analysis Group, or HSO-SAG chartered by MEPAG in 2015 to address science objectives and landing site criteria for future human missions to Mars (Niles, Beaty et al. 2015). Currently, NASA's plan to land astronauts on Mars in the mid 2030's would allow for robust human exploration of the surface in the next 35 years. We expect that crews would be able to traverse to sites up to 100 km away from the original landing site using robust rovers. A habitat outfitted with state of the art laboratory facilities that could enable the astronauts to perform cutting edge science on the surface of Mars. Robotic/human partnership during exploration would further enhance the science return of the mission.

Niles, P. B.↗
NASA NTRS2011

TPSAS-NF1676L-12321-DND

The operation of some networks, such as air transportation networks, can be complicated by congestion through a small subset of nodes. The congestion may be influenced by the connectivity of the network, or by the presence of constraints restricting the flow through particular nodes. This work investigates the effects of both connectivity and node flow constraints on the operation of a network. We develop the Minimax Node Load Problem (MNLP), a multicommodity flow model which minimizes the worst-case flow through any node in a given input network. The optimal solution to this problem provides us with the minimax node load, which we propose as a measure of network congestion. Keeping the number of nodes fixed, we first increase connectivity in a series of networks, and observe that topologies with more distributed connections result in a reduction in the minimax node load. However, when connectivity is increased further, the reductions diminish and are accompanied by solutions with undesirable qualities such as longer commodity paths. We then perform a second set of experiments over the same network, constraining flow through different subsets of nodes at different magnitudes of flow restriction, finding that (1) more constrained nodes lead to the largest increases in minimax node load and (2) constraints on the most connected nodes have the greatest effect on both congestion and commodity path length.

Douglas W Lee↗
NASA NTRS2011

TPSAS-NF1676L-12264-DND

The operation of some networks, such as air transportation networks, can be complicated by congestion through a small subset of nodes. The congestion may be influenced by the connectivity of the network, or by the presence of constraints restricting the flow through particular nodes. This work investigates the effects of both connectivity and node flow constraints on the operation of a network. We develop the Minimax Node Load Problem (MNLP), a multicommodity flow model which minimizes the worst-case flow through any node in a given input network. The optimal solution to this problem provides us with the minimax node load, which we propose as a measure of network congestion. Keeping the number of nodes fixed, we first increase connectivity in a series of networks, and observe that topologies with more distributed connections result in a reduction in the minimax node load. However, when connectivity is increased further, the reductions diminish and are accompanied by solutions with undesirable qualities such as longer commodity paths. We then perform a second set of experiments over the same network, constraining flow through different subsets of nodes at different magnitudes of flow restriction, finding that (1) more constrained nodes lead to the largest increases in minimax node load and (2) constraints on the most connected nodes have the greatest effect on both congestion and commodity path length.

Douglas Lee↗
NASA NTRSDate not supplied

Effects of Confinement on Flame Spread in Microgravity

Solid fuel combustion experiments aboard the ISS examine the effects of confinement on a concurrent, purely-forced-flow flame spread in microgravity environment. The results for a thin, cotton-fiberglass-blended textile fabric fuel are presented. Flat baffles of differing materials are used to alter the radiative boundary conditions with transparent polycarbonate, black anodized aluminum (reflectance ~ 0), and highly polished aluminum (reflectance ~ 1). The baffles are parallel to the fuel sheet and placed symmetrically on each side. The inter-baffle distance is varied to change the boundary conditions for the flow. In all tests, samples are ignited at the upstream leading edge and allowed to burn to completion. Results show that the flame reaches a steady length and spread rate at low flow speeds (< 15 cm/s) for all tested inter-baffle distances. As the distance decreases, the flame length and spread rate first increase then decrease showing an optimal inter-baffle distance. For all baffle types, the flame either fails to ignite or extinguishes before reaching the end of the sample when the inter-baffle distance is too small (~ 1 cm). This is attributed to the reduction of oxygen supply to the flame zone and heat loss to the baffles. The results also show at the same inter-baffle distance, flame length and spread rate are highest for polished aluminum baffles, and lowest for transparent polycarbonate baffles. The differences are most prominent at intermediate tested baffle distances. While the radiative heat feedback from the baffles is expected to increase when the baffle distance decreases, the combustion is limited by the reduced oxygen supply. Near this limit, flame lengths and spread rates are similar for all baffle types.

Microgravity↗