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NASA NTRS2016

Large Observatory for X-ray Timing (LOFT-P): A Probe-Class Mission Concept Study

LOFT-P is a mission concept for a NASA Astrophysics Probe-Class (less than $1B) X-ray timing mission, based on the LOFT M-class concept originally proposed to ESA's M3 and M4 calls. LOFT-P requires very large collecting area, high time resolution, good spectral resolution, broadband spectral coverage (2-30 keV), highly flexible scheduling, and an ability to detect and respond promptly to time-critical targets of opportunity. Many of LOFTP's targets are bright, rapidly varying sources, so these measurements are synergistic to imaging and high-resolution spectroscopy instruments, addressing much smaller distance scales than are possible without very long baseline X-ray interferometry, and using complementary techniques to address the geometry and dynamics of emission regions. LOFT-P was presented as an example mission to the head of NASA's Astrophysics Division, to demonstrate the strong community support for creation of a probe-class, for missions costing between $500M and $1B. We submitted a white paper4 in response to NASA PhysPAG's call for white papers: Probe-class Mission Concepts, describing LOFT-P science and a simple extrapolation from the ESA study costs. The next step for probe-class missions will be input into the NASA Astrophysics Decadal Survey to encourage the creation of a probe-class opportunity. We report on a 2016 study by MSFC's Advanced Concepts Office of LOFT-P, a US-led probe-class LOFT concept.

x-ray↗

DOE OSTI2025

Wildfire towers drive firebrand lofting: insights from coupled fire-atmosphere model simulations

Wildfire behavior is shaped by complex fire dynamics, with firebrands playing a critical role in spot fire ignition and fire spread. While previous studies have explored firebrand generation and transport, the specific role of towers and troughs from wildland fires in the lofting of firebrands remains unquantified. This study addresses that gap by using physics-based coupled fire-atmosphere model simulations to examine how wildfire towers (updrafts) and troughs (downdrafts) influence firebrand lofting. Our results show that the majority of firebrands (78.85%) are lofted from towers, where strong updrafts drive long-range transport. In contrast, only 21.15% of firebrands are lofted within troughs, where downdrafts cause most firebrands to fall near the fireline. We also find that firebrand size significantly influences lofting behavior, with smaller particles (1 mm radius) exhibiting the strongest correlation with updraft intensity. These findings highlight the dominant role of wildfire towers in promoting long-distance firebrand dispersal—an essential factor in rapid wildfire growth and wildland-urban interface (WUI) fire risks. By quantifying the relationship between firebrand lofting and fire-induced atmospheric features, this study provides critical insights to improve spot fire modeling, support mitigation planning, and enhance firefighter and WUI community safety in spot fire-prone regions.

54 ENVIRONMENTAL SCIENCES↗

NASA NTRS2011

Be/X-Ray Pulsar Binary Science with LOFT

Accretion disks are ubiquitous in astronomical sources. Accretion powered pulsars are a good test bed for accretion disk physics, because unlike for other objects, the spin of the neutron star is directly observable allowing us to see the effects of angular momentum transfer onto the pulsar. The combination of a sensitive wide-field monitor and the large area detector on LOFT will enable new detailed studies of accretion powered pulsars which I will review. RXTE observations have shown an unusually high number of Be/X-ray pulsar binaries in the SMC. Unlike binaries in the Milky Way, these systems are all at the same distance, allowing detailed population studies using the sensitive LOFT WFM, potentially providing connections to star formation episodes. For Galactic accreting pulsar systems, LOFT will allow measurement of spectral variations within individual pulses, mapping the accretion column in detail for the first time. LOFT will also provide better constraints on magnetic fields in accreting pulsars, allowing measurements of cyclotron features, observations of transitions into the centrifugal inhibition regime, and monitoring of spin-up rate vs flux correlations. Coordinated multi-wavelength observations are crucial to extracting the best science from LOFT from these and numerous other objects.

Wilson-Hodge, Colleen A.↗

NASA NTRSDate not supplied

Design of Electrostatic Dust Lofting Suborbital Flight Experiment Examining Photoionization under Lunar Gravity

Dust on the lunar surface electrostatically charges due to the plasma environment surrounding the Moon, causing grains to become lofted and adhere to nearby surfaces including landers and astronauts. Studying the behaviors of these charged particles in the lunar environment is essential to plan around the deleterious effects of dust to future Moon missions. Models attempt to predict the amount of dust loading that can be expected in many of these scenarios, but they require experimental validation to be predictive. This physics cannot be fully studied on Earth due to the six times larger gravitational force obscuring the electrostatic interactions, so it is necessary to run experiments in a more relevant environment, including vacuum and near-lunar gravitational effects. An experiment has been designed to fly on the Lunar Gravity Acceleration (LGA) mission aboard the Blue Origin New Shepard suborbital rocket. This experiment will perform photoionization charging of lunar regolith simulant grains under the illumination of an ultraviolet (UV) source. As a result, the charged grains will then electrostatically repel one another and loft in the reduced gravity environment; their trajectories will be imaged via a high-speed camera. Preliminary laboratory results influencing the design of this experiment will be presented, including characterization of several UV sources, measurements of photoionization currents under various vacuum conditions, and examination of lunar simulant dust lofting under terrestrial gravity. Results from this flight will be compared with ground-based testing and the laboratory results outlined above to examine the dependence on gravity and will be fed into the dust charging and lofting models currently under development.

electrostatics↗

NASA NTRS2007

Effects of Convective Ice Lofting on H2O and HDO in the Tropical Tropopause Layer

We have added convective ice lofting to a Lagrangian trajectory model of near-tropopause water vapor (H2O) and its isotopologue HDO. The ice lofting simulation is based on a parameterization derived from Aura Microwave Limb Sounder (MLS) icewater content measurements. In previous papers, the Lagrangian model has accurately interannual and seasonal H2O abundances; there was no need for convection to be included in the model. We show here that this model does a poor job of simulating near-tropopause HDO, but that the addition of convective ice lofting greatly improves the HDO simulation. Convective ice lofting has a small effect on lower stratospheric H2O. H2O there is set by the minimum temperature encountered at the cold-point tropopause, so H2O added by convection below this level does not make it through this cold point and into the lower stratosphere. Thus, adding convection to the model does not degrade the model's previously demonstrated accurate simulations of H2O. We conclude that the HDO data suggest an important role for convective mass flux into the so-called tropical tropopause layer.

Dessler, A. E.↗

NASA NTRS1981

United Airlines LOFT training

Line oriented training is used in a broader, more generic sense that as a specific program under FAR 12.1409 and AC 120-35. A company policy was adopted more than twenty years ago requiring that all pilot checks and recurrent training be conducted with a full crew occupying the seats they occupy on the line. Permission was obtained to reschedule the hours for recurrent proficiency training to include one and one-half hours of LOFT flight. The number of emergencies and abnormal procedures which could be undertaken were considered and the introduction of an a occasional incapacitation revealed which person is the most difficult to replace on the widebodies. By using the LOFT concept, every training period can be structured like a typical line flight. The use of LOFT in simulator syllabus development and problems that need to be refined are discussed.

Cavanagh, D.↗

NASA NTRS1981

Delta Airlines LOFT training

A LOFT program was developed as part of the DC-9 training program which serves as a prototype for much of Delta's other aircraft training programs. The LOFT used differs little from the ideology presented in the Advisory Circular. Difficulty and experienced concerns regarding the effectiveness of LOFT as a complete training vehicle are explored.

Whitehead, J.↗

NASA NTRS1984

Use of airplanes for loft training

The use of an aircraft for line oriented flight training (LOFT) is examined. Cockpit resource management (CRM) and LOFT training are compared. The advantages of the LOFT is a better cost effectiveness since there is no need to buy a simulator. The flight crew workload can be limited to a minimum.

Sele, M.↗

NASA NTRS1991

What makes a good LOFT scenario? Issues in advancing current knowledge of scenario design

An effort is made to ascertain which combinations of technical demands and crew coordination should be incorporated in training scenarios in order to maximize the effectiveness of training for crew members. Such high-fidelity simulation, which has come to be known as 'line-oriented flight training' or LOFT, involves the practice of both technical and crew coordination skills in a realistic setting, in conjunction with periodic reviews of performance via videotaped feedback. Attention is given to the integration of appropriate information, the measurement of objective task demands, the character of information from LOFT students, and the leeway allowed LOFT instructors.

Gregorich, Steven E.↗

NASA NTRS2013

Proposed US Contributions to LOFT

Proposed US Enhancements include:Tantalum X -ray collimator, Additional ground station, Large Observatory for X-Ray Timing (LOFT) instrument team participation, US science support center & data archive, and Science enabled by US hardware. High-Z material with excellent stopping power. Fabricated using a combination of laser micromachining and chemical etching. Known technology capable of producing high-aspect ratio holes and large open fractions. Reduces LOFT LAD background by a factor of 3. Telemetry formats for LOFT based upon RXTE/EDS experience. Ground system software and strategies for WFM based upon RXTE/ASM automated pipeline software. MSFC engineering trade studies supporting the Ta collimator. Burst alert triggers based upon Fermi/GBM and HETE-2. Science Enhancements Enabled by US Hardware include: Tantalum collimator: Reduces background by factor of 3. Improves sensitivity to faint sources such as AGN. Eliminates contamination by bright/variable sources. outside the LAD field of view. US Ground Station: Enables continuous telemetry of all events from the WFM. Allows LAD to observe very bright >500 mCrab sources with full event resolution.

Wilson-Hodge, Colleen↗

NASA NTRS2019

The Comprehensive LOFT

The training of pilots at major US air carriers has changed little over the years. These courses often begin in learning each and every sub-system of the particular airplane to be flown. The training course culminates in a series of training sessions in a full-motion, full-mission flight simulator. Most US airlines now incorporate one final simulator training session known as LOFT, Line Oriented Flight Training, where rather than going through a series of disconnected, isolated, flight maneuvers, the session is conducted as a flight from a departure airport to a destination airport. Flying for an Air Line, one is a Line Pilot, flying the "line." And so the LOFT session in the simulator is supposed to represent the reality of line operations and thus prepare the trainee to fly the line. But if the ultimate goal of the training is to produce a pilot who is ready to safely and efficiently fly the line, shouldn't all training be "line oriented"? This paper describes an approach to structuring airline flight training such that all training is "line oriented." This approach represents an opportunity to translate many of the training principles offered by Healy and her colleagues into training specifications.

Training Principles↗

NASA NTRS1981

Group 2: Real time LOFT operations

All LOFT scenarios should be constructed so as to provide the highest degree of realism that is economically, technically, and operationally feasible. The more realistic the situation, the faster the crew will adjust their thinking and provide reactions which would be typical of a line-flight orientation. The goal is to produce crew performance which would be typical of a crew on an actual line flight, given the same set of circumstances that were developed during the scenario. The briefing which is provided to the crew before entering the simulator for LOFT, the trip papers, the communications throughout the flight, the role played by the instructor, and so on, are important factors, crucial to the establishment and maintenance of a high degree of realism. Crews should have all manuals and other required equipment for a normal line-flight.

Cavanagh, D.↗

NASA NTRS1983

Aerodynamic analysis of the loft anomaly observed on orbital flight tests of the space shuttle

The loft anomaly observed during the launch phase of the orbital flight tests (OFT) of the Space Shuttle is described and evidence that the loft anomaly resulted from previously unobserved aerodynamic phenomena is presented. The anomaly was that the altitude at staging was higher than anticipated. The anticipated altitude profile was predicted on wind tunnel test results that did not accurately simulate the flow between the orbiter vehicle and external tank and did not adequately simulate the engine plumes and thus the base pressures. An analogy is used to relate the flow between the orbiter and external tank to the flow in a two dimensional channel. Plume simulation is identified as a major goal during wind tunnel testing, and a wind tunnel test that was conducted to provide the best possible representation of the plume effect on the channel flow field is described.

Surber, T. E.↗

NASA NTRS1996

Facilitation techniques as predictors of crew participation in LOFT debriefings

Based on theories of adult learning and airline industry guidelines for Crew Resource Management (CRM), the stated objective during Line Oriented Flight Training (LOFT) debriefings is for instructor pilots (IP's) to facilitate crew self-analysis of performance. This study reviews 19 LOFT debriefings from two major U.S. airlines to examine the relationship between IP efforts at facilitation and associated characteristics of crew participation. A subjective rating scale called the Debriefing Assessment Battery was developed and utilized to evaluate the effectiveness of IP facilitation and the quality of crew participation. The results indicate that IP content, encouragement, and questioning techniques are highly and significantly correlated with, and can therefore predict, the degree and depth of crew participation.

McDonnell, L. K.↗

NASA NTRS1996

A Cross-Industry Analysis of LOFT Debriefings

Line Oriented Simulation (LOS) iss widely used to provide crews opportunities to practice Cockpit Resource Management (CRM) concepts in realistic, challenging simulated flight situations. LOS includes both Line Oriented Flight Training (LOFT), the original "non-jeopardy" form in which the crews are not graded on their performance, and Line Oriented Evaluation (LOE). In LOE, crews are graded, which is required in those airlines that participate in the FAA's Advanced Qualification Program (ALP). How much crews learn in LOS arid take back to the line hinges on the effectiveness of the debriefing that follows the LOS. The simulation itself is a busy, intense experience, and thoughtful discussion afterwards is necessary for the crew to sort out and interpret what happened and why. Instructors are expected to lead briefings in a way that encourages crew members to analyze for themselves their performance in the LOS. Rather than lecturing the crew in the traditional manner on what they did right and wrong, the instructor is expected to facilitate self-discovery and self-critique by the crew. We have recently completed a study in which we observed 36 LOFT briefings at 5 major U.S. airlines. We audiotape recorded the briefings, transcribed the recordings, and coded for more than 70 variables. Our analysis addresses four broad questions: To what extent do instructors attempt to facilitate crew self-analysis? What techniques do instructors use to facilitate and how effective are these techniques? What is the character of crew participation? To what extent do briefings emphasize CRM and crew performance? We discuss the implications of our findings for ALP and LOE.

Dismukes, Key↗

NASA NTRS2007

Extinction-to-Backscatter Ratios of Lofted Aerosol Layers Observed During the First Three Months of CALIPSO Measurements

Case studies from the first three months of the Cloud and Aerosol Lidar and Infrared Pathfinder Spaceborne Observations (CALIPSO) measurements of lofted aerosol layers are analyzed using transmittance [Young, 1995] and two-wavelength algorithms [Vaughan et al., 2004] to determine the aerosol extinction-to-backscatter ratios at 532 and 1064 nm. The transmittance method requires clear air below the layer so that the transmittance through the layer can be determined. Suitable scenes are selected from the browse images and clear air below features is identified by low 532 nm backscatter signal and confirmed by low depolarization and color ratios. The transmittance and two-wavelength techniques are applied to a number of lofted layers and the extinction-to-backscatter ratios are compared with values obtained from the CALIPSO aerosol models [Omar et al., 2004]. The results obtained from these studies are used to adjust the aerosol models and develop observations based extinction-to-backscatter ratio look-up tables and phase functions. Values obtained by these techniques are compared to Sa determinations using other independent methods with a goal of developing probability distribution functions of aerosol type-specific extinction to backscatter ratios. In particular, the results are compared to values determined directly by the High Spectral Resolution Lidar (HSRL) during the CALIPSO CloudSat Validation Experiments (CCVEX) and Sa determined by the application of the two-wavelength lidar Constrained Ratio Aerosol Model-fit (CRAM) retrieval approach [Cattrall et al., 2005; Reagan et al., 2004] to the HSRL data. The results are also compared to values derived using the empirical relationship between the multiple-scattering fraction and the linear depolarization ratio by using Monte Carlo simulations of water clouds [Hu et al., 2006].

Omar, Ali H.↗

NASA NTRS2011

Loft: An Automated Mesh Generator for Stiffened Shell Aerospace Vehicles

Loft is an automated mesh generation code that is designed for aerospace vehicle structures. From user input, Loft generates meshes for wings, noses, tanks, fuselage sections, thrust structures, and so on. As a mesh is generated, each element is assigned properties to mark the part of the vehicle with which it is associated. This property assignment is an extremely powerful feature that enables detailed analysis tasks, such as load application and structural sizing. This report is presented in two parts. The first part is an overview of the code and its applications. The modeling approach that was used to create the finite element meshes is described. Several applications of the code are demonstrated, including a Next Generation Launch Technology (NGLT) wing-sizing study, a lunar lander stage study, a launch vehicle shroud shape study, and a two-stage-to-orbit (TSTO) orbiter. Part two of the report is the program user manual. The manual includes in-depth tutorials and a complete command reference.

Eldred, Lloyd B.↗

NASA NTRS2011

Neutron Star Spin Measurements and Dense Matter with LOFT

Observations over the last decade with RXTE have begun to reveal the X-ray binary progenitors of the fastest spinning neutron stars presently known. Detection and study of the spin rates of binary neutron stars has important implications for constraining the nature of dense matter present in neutron star interiors, as both the maximum spin rate and mass for neutron stars is set by the equation of state. Precision pulse timing of accreting neutron star binaries can enable mass constraints. Particularly promIsing is the combination of the pulse and eclipse timing, as for example, in systems like Swift 11749.4-2807. With its greater sensitivity, LOFT will enable deeper searches for the spin periods of the neutron stars, both during persistent outburst intervals and thermonuclear X-ray bursts, and enable more precise modeling of detected pulsations. I will explore the anticipated impact of LOFT on spin measurements and its potential for constraining dense matter in neutron stars

Strohmayer, Tod↗