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NASA NTRS2014

Analytical Assessment of Simultaneous Parallel Approach Feasibility from Total System Error

In a simultaneous paired approach to closely-spaced parallel runways, a pair of aircraft flies in close proximity on parallel approach paths. The aircraft pair must maintain a longitudinal separation within a range that avoids wake encounters and, if one of the aircraft blunders, avoids collision. Wake avoidance defines the rear gate of the longitudinal separation. The lead aircraft generates a wake vortex that, with the aid of crosswinds, can travel laterally onto the path of the trail aircraft. As runway separation decreases, the wake has less distance to traverse to reach the path of the trail aircraft. The total system error of each aircraft further reduces this distance. The total system error is often modeled as a probability distribution function. Therefore, Monte-Carlo simulations are a favored tool for assessing a "safe" rear-gate. However, safety for paired approaches typically requires that a catastrophic wake encounter be a rare one-in-a-billion event during normal operation. Using a Monte-Carlo simulation to assert this event rarity with confidence requires a massive number of runs. Such large runs do not lend themselves to rapid turn-around during the early stages of investigation when the goal is to eliminate the infeasible regions of the solution space and to perform trades among the independent variables in the operational concept. One can employ statistical analysis using simplified models more efficiently to narrow the solution space and identify promising trades for more in-depth investigation using Monte-Carlo simulations. These simple, analytical models not only have to address the uncertainty of the total system error but also the uncertainty in navigation sources used to alert an abort of the procedure. This paper presents a method for integrating total system error, procedure abort rates, avionics failures, and surveillance errors into a statistical analysis that identifies the likely feasible runway separations for simultaneous paired approaches.

Madden, Michael M.↗

NASA NTRS2011

Asteroid Return Mission Feasibility Study

This paper describes an investigation into the technological feasibility of finding, characterizing, robotically capturing, and returning an entire Near-Earth Asteroid (NEA) to the International Space Station (ISS) for scientific investigation, evaluation of its resource potential, determination of its internal structure and other aspects important for planetary defense activities, and to serve as a testbed for human operations in the vicinity of an asteroid. Reasonable projections suggest that several dozen candidates NEAs in the size range of interest (approximately 2-m diameter) will be known before the end of the decade from which a suitable target could be selected. The conceptual mission objective is to return an approximately 10,000-kg asteroid to the ISS in a total flight time of approximately 5 years using a single Evolved Expendable Launch Vehicle. Preliminary calculations indicate that this could be accomplished using a solar electric propulsion (SEP) system with high-power Hall thrusters and a maximum power into the propulsion system of approximately 40 kW. The SEP system would be used to provide all of the post-launch delta V. The asteroid would have an unrestricted Earth return Planetary Protection categorization, and would be curated at the ISS where numerous scientific and resource utilization experiments would be conducted. Asteroid material brought to the ground would be curated at the NASA Johnson Space Center. This preliminary study identified several areas where additional work is required, but no show stoppers were identified for the approach that would return an entire 10,000-kg asteroid to the ISS in a mission that could be launched by the end of this decade.

near Earth asteriods (NEA)↗

NASA NTRS2009

Venus Mobile Explorer with RPS for Active Cooling: A Feasibility Study

We present our findings from a study to evaluate the feasibility of a radioisotope power system (RPS) combined with active cooling to enable a long-duration Venus surface mission. On-board power with active cooling technology featured prominently in both the National Research Council's Decadal Survey and in the 2006 NASA Solar System Exploration Roadmap as mission-enabling for the exploration of Venus. Power and cooling system options were reviewed and the most promising concepts modeled to develop an assessment tool for Venus mission planners considering a variety of future potential missions to Venus, including a Venus Mobile Explorer (either a balloon or rover concept), a long-lived Venus static lander, or a Venus Geophysical Network. The concepts modeled were based on the integration of General Purpose Heat Source (GPHS) modules with different types of Stirling cycle heat engines for power and cooling. Unlike prior investigations which reported on single point design concepts, this assessment tool allows the user to generate either a point design or parametric curves of approximate power and cooling system mass, power level, and number of GPHS modules needed for a "black box" payload housed in a spherical pressure vessel.

Leifer, Stephanie D.↗

NASA NTRS2015

The Feasibility of Wearables in an Enterprise Environment and Their Impact on IT Security

This paper is intended to explore the usability and feasibility of wearables in an enterprise environment and their impact on IT Security. In this day and age, with the advent of the Internet of Things, we must explore all the new technology emerging from the minds of the new inventors. This means exploring the use of wearables in regards to their benefits, limitations, and the new challenges they pose to securing computer networks in the Federal environment. We will explore the design of the wearables, the interfaces needed to connect them, and what it will take to connect personal devices in the Federal enterprise network environment. We will provide an overview of the wearable design, concerns of ensuring the confidentiality, integrity, and availability of information and the challenges faced by those doing so. We will also review the implications and limitations of the policies governing wearable technology and the physical efforts to enforce them.

wearables↗

NASA NTRS2015

A CFD-Based Study of the Feasibility of Adapting an Erosion Burner Rig for Examining the Effect of CMAS Deposition Corrosion on Environmental Barrier Coatings

Thermodynamic and computational fluid dynamics modeling has been conducted to examine the feasibility of adapting the NASA-Glenn erosion burner rigs for use in studies of corrosion of environmental barrier coatings by the deposition of molten CMAS. The effect of burner temperature, Mach number, particle preheat, duct heating, particle size, and particle phase (crystalline vs. glass) were analyzed. Detailed strategies for achieving complete melting of CMAS particles were developed, thereby greatly improving the probability of future successful experimental outcomes.

Deposition Studies↗

NASA NTRS2015

Feasibility of Self Powered Actuation for Flow, Separation and Vibration Control

A gas turbine engine is anywhere from 40-50% efficient. A large amount of energy is wasted as heat. Some of this heat is recoverable through the use of energy harvesting and can be used for powering on-board systems or for storing energy in batteries to replace auxiliary power units (APUs). As hybrid electric aircraft become more common, the use of energy harvesting will see increasingly more benefit and become commonplace in gas turbine engines. For electric aircraft with motors, TEGs would be beneficial for reclaiming waste heat from electric motors. The primary focus of this work was to evaluate the feasibility of harvesting energy from the hot section of a gas turbine engine (for a single aisle Boeing 737 thrust class) using thermoelectric generators (TEGs). The resulting heat could be used to power on-board actuation mechanisms such as plasma actuators and piezoelectric actuators. The work is a result of a two year NASA Center Innovation Fund from 2009 to 2011. The trade-off between thermoelectric harvesting and blade surface temperature were studied to ensure that blade durability is not adversely impacted by embedding a low thermal conductivity TEG. Calculations show that.5-10 Watts can be harvested per blade depending on flow conditions and on the thermoelectric material chosen. BiTe and SiGe were used for this analysis and future thermoelectric generators or multiferroic alloys could considerably improve power output.

bottoming cycle↗

NASA NTRS2015

Feasibility of Supersonic Aircraft Concepts for Low-Boom and Flight Trim Constraints

This paper documents a process for analyzing whether a particular supersonic aircraft configuration layout and a given cruise condition are feasible to achieve a trimmed low-boom design. This process was motivated by the need to know whether a particular configuration at a given cruise condition could be reshaped to satisfy both low-boom and flight trim constraints. Without such a process, much effort could be wasted on shaping a configuration layout at a cruise condition that could never satisfy both low-boom and flight trim constraints simultaneously. The process helps to exclude infeasible configuration layouts with minimum effort and allows a designer to develop trimmed low-boom concepts more effectively. A notional low-boom supersonic demonstrator concept is used to illustrate the analysis/design process.

Li, Wu↗

NASA NTRS2015

Feasibility of Dynamic Stability Measurements of Planetary Entry Capsules Using MSBS

The feasibility of conducting dynamic stability testing of planetary entry capsules at low supersonic Mach numbers using a Magnetic Suspension and Balance System (MSBS) is reviewed. The proposed approach would employ a spherical magnetic core, exert control in three degrees-of-freedom (i.e. x, y, z translations) and allow the model to freely rotate in pitch, yaw, and roll. A proof-of-concept system using an existing MSBS electromagnet array in a subsonic wind tunnel is described, with future potential for development of a new system for a supersonic wind tunnel.

Britcher, Colin↗

NASA NTRS2016

Biodigester Feasibility and Design for Space and Earth Project

Biodigesters harness and utilize byproducts, and are a valuable technology for waste conversion and advanced exploration closed loops targets (6.1.a-E), including that of human waste. On Mars and at JSC, this could lead to growing food and to more sustainable uses of waste. It is critical to understand biogas generation rates, odor management of the effluent, and nutrient viability. Improved efficiency and reliance on this renewable energy source can become feasible for deep space missions.

Terrier, Douglas↗

NASA NTRS2017

Conceptual Feasibility Study of the Hyperloop Vehicle for Next-Generation Transport

The Hyperloop concept is proposed as a faster, cheaper alternative to high-speed rail and traditional short-haul aircraft. It consists of a passenger pod traveling through a tube under light vacuum while being propelled and levitated by a combination of permanent and electro-magnets. The concept addresses NASA's research thrusts for growth in demand, sustainability, and technology convergence for high-speed transport. Hyperloop is a radical departure from other advanced aviation concepts, however it remains an aeronautics concept that tackles the same strategic goals of low-carbon propulsion and ultra-effcient vehicles. System feasibility was investigated by building a multidisciplinary vehicle sizing model that takes into account aerodynamic, thermodynamic, structures, electromagnetic, weight, and mission analyses. The sizing process emphasized the strong coupling between the two largest systems: the tube and the passenger pod. The model was then exercised to examine Hyperloop from a technical and cost perspective. The structural sizing analysis of the travel tube demonstrates potential for signi cant capital cost reductions by considering an underwater route. Examination of varying passenger capacity indicates that the system can be operated with a wide range of passenger loads without significant change in operating expenses. Lastly, a high-level sizing study simulated variations in tube area, pressure, pod speed, and passenger capacity showing that there is a tube pressure that minimizes operating energy usage. The value of this optimal tube pressure is highly sensitive to numerous design details. These combined estimates of energy consumption, passenger throughput, and mission analyses all support Hyperloop as a faster and cheaper alternative to short-haul flights. The tools and expertise used to quantify these results also demonstrate how traditional aerospace design methods can be leveraged to handle the complex and coupled design process. Much of the technology development required for the Hyperloop is shared with next-generation aircraft. Furthermore, the substantial public interest and active commercial development make it an ideal candidate as an aircraft technology driver and test bed.

Hyperloop Vehicle↗

NASA NTRS2016

Feasibility for Orbital Life Extension of a CubeSat in the Lower Thermosphere

Orbital flight of CubeSats at altitudes between 150 and 250 km has the potential to enable a new class of scientific, commercial, and defense-related missions. A study is presented to demonstrate the feasibility of extending the orbital lifetime of a CubeSat in a 210 km orbit. Propulsion consists of an electrospray thruster operating at a 2 W, 0.175 mN thrust, and an specific impulse (Isp) of 500 s. The mission consists of two phases. In phase 1, the CubeSat is deployed from a 414 km orbit and uses the thruster to deorbit to the target altitude of 210 km. In phase 2, the propulsion system is used to extend the mission lifetime until propellant is fully expended. A control algorithm based on maintaining a target orbital energy is presented that uses an extended Kalman filter to generate estimates of the orbital dynamic state, which are periodically updated by Global Positioning System measurements. For phase 1, the spacecraft requires 25.21 days to descend from 414 to 210 km, corresponding to a delta V = 96.25 m/s and a propellant consumption of 77.8 g. Phase 2 lasts 57.83 days, corresponding to a delta V = 119.15 m/s, during which the remaining 94.2 g of propellant are consumed.

Blandino, John J.↗

NASA NTRS2017

Walking the Filament of Feasibility: Global Optimization of Highly-Constrained, Multi-Modal Interplanetary Trajectories Using a Novel Stochastic Search Technique

Interplanetary trajectory optimization problems are highly complex and are characterized by a large number of decision variables and equality and inequality constraints as well as many locally optimal solutions. Stochastic global search techniques, coupled with a large-scale NLP solver, have been shown to solve such problems but are inadequately robust when the problem constraints become very complex. In this work, we present a novel search algorithm that takes advantage of the fact that equality constraints effectively collapse the solution space to lower dimensionality. This new approach walks the filament'' of feasibility to efficiently find the global optimal solution.

Englander, Arnold C.↗

NASA NTRS2017

Walking the Filament of Feasibility: Global Optimization of Highly-Constrained, Multi-Modal Interplanetary Trajectories Using a Novel Stochastic Search Technique

Englander, Arnold C.↗

NASA NTRS2018

The Feasibility of Detecting Supercooled Liquid with a Forward-Looking Radiometer

A three-dimensional radiative transfer model is utilized to determine the feasibility of a forward-viewing passive sensor for remotely detecting hazardous icing conditions. Wband ground-based radar simulations show no obvious ability to discriminate a cloud-top supercooled layer; however, the spectra for a forward-viewing passive sensor show a strong signal at two stand-off distances when compared with the clear sky spectrum. Such an instrument would be critical for manned and unmanned aircraft, particularly when size, weight, and power requirements restrict the installation of deicing equipment.

clouds↗

NASA NTRS2016

Feasibility of Varying Geo-Fence Around an Unmanned Aircraft Operation Based on Vehicle Performance and Wind

Managing trajectory separation is critical to ensuring accessibility, efficiency, and safety in the unmanned airspace. The notion of geo-fences is an emerging concept, where distance buffers enclose individual trajectories and areas of operation in order to manage the airspace. Currently, the Air Traffic Management system for commercial travel defines static distance buffers around the aircraft; however, commercial UASs are envisioned to operate in significantly closer proximity to other UAS requiring a geo-fence for spacing operations. The geo-fence size can be determined based on vehicle performance characteristics, state of the airspace, weather, and other unforeseen events such as emergency or disaster response. Calculation of the geo-fence size could be determined as part of pre-flight planning and during real-time operations. A largely non-homogeneous fleet of UASs will be operating in low altitude and will likely be commercially developed. Due to intellectual property concerns, the operators may not provide detailed specifications of the control system to UTM. In addition, the huge variety of UAS makes modeling each control system prohibitive and flight data for these vehicles may not exist. Therefore, a generalized, simple geo-fence sizing algorithm must be developed such that it does not rely on detailed knowledge of the vehicle control system, accounts for the presence of urban winds, and is sufficiently accurate. In this work, two simple models are investigated to determine its feasibility as an adequate means for calculating the geo-fence size. The vehicle data used in this work are provided by UAS manufactures who have partnered with NASA's UTM project and some publicly available websites. The first model utilizes wind data processed from the NOAA HRRR (Hourly Rapid Refresh) product and Sonar Annemometer data provided by San Jose State. The second model utilizes OpenFOAM which is a CFD code used to generate a wind field for flow around a single building. The key vehicle performance parameters can include UAS response time to disturbances, command to actuation latency, control system rate limits, time to recovery to desired path, and aerodynamics. It was found that the first model provides an initial understanding of geo-fence sizing, but does not provide enough accuracy to provide UTM with an efficient means of scheduling vehicles. The results of the second model reveal that modeling UAS controls systems with a linearized plant and gain scheduled PID controller does not allow capture the UAS flight dynamics within a significant envelope of the wind disturbances.

uncertainty↗

NASA NTRS2017

Diving Deeper: Exploring the Feasibility of Lowering Cassini’s Final Orbits

During the final five orbits of Cassini’s mission, the spacecraft will get closer to Saturn than it has ever been. These five orbits were designed to be as deep in the atmosphere as Cassini could safely fly; however, recent occultation data of Saturn’s atmosphere suggest that it is contracting. Given this contraction, the primary concern during these orbits has shifted from spacecraft health and safety to loss of science value. This paper explores a scenario for modifying the Cassini spacecraft’s trajectory, during these final orbits, such that it dips deeper into Saturn’s atmosphere. This scenario describes the method for in-situ detection of Saturn’s atmospheric state, the locations and sizes of maneuvers that would reduce the final periapsis altitudes, the effects of such maneuvers on the remaining trajectory, and the risks involved. The result is that a periapsis-lowering, “pop-down” maneuver is feasible during Cassini’s final orbits. Risk to the spacecraft is minimized by using the attitude control thrusters as density detectors during the first three atmospheric transits of the final five orbits. Should these transits reveal sufficiently low density and should sufficient propellant remain, then the Cassini project will consider performing the maneuver.

Sturm, Erick J., II↗

NASA NTRS2019

Feasibility of Electrified Propulsion for Ultra-Efficient Commercial Aircraft Final Report

MIT, Aurora Flight Sciences, and USC have collaborated to assess the feasibility of electric, hybridelectric, and turbo-electric propulsion for ultra-efficient commercial transportation. The work has drawn on the team expertise in disciplines related to aircraft design, propulsion-airframe integration, electric machines and systems, engineering system design, and optimization. A parametric trade space analysis has been carried out to assess vehicle performance across a range of transport missions and propulsion architectures to establish how electrified propulsion systems scale. An optimization approach to vehicle conceptual design modeling was taken to enable rapid multidisciplinary design space exploration and sensitivity analysis. The results of the analysis indicate vehicle aero-propulsive integration benefits enabled by electrification are required to offset the increased weight and loss associated with the electric system and achieve enhanced performance; the report describes the conceptual configurations than can offer such enhancements. The main contribution of the present work is the definition of electric vehicle design attributes for potential efficiency improvements at different scales. Based on these results, key areas for future research are identified, and extensions to the trade space analysis suitable for higher fidelity electrified commercial aircraft design and analysis have been developed.

Hall, D.K.↗

NASA NTRS2017

Oxygen Storage Tanks Are Feasible for Mars Transit

The Mars transit tanks will probably be titanium lined, composite over wrapped pressure vessels (COPVs) similar to those used in the space shuttle and International Space Station(ISS). Since the mass of a storage tank is proportional to the mass of the gas it contains, the required oxygen will use about the same mass of tanks regardless of the number and size ofthe tanks. Using existing relatively small COPVs is possible. Pressure vessels can fail due torupture and leakage but no failures have occurred in space and the expected failure rates are very low. Since one or two spare tanks are required for reliability, using smaller tanks can reduce the total mass. For a Mars round trip, the mass of oxygen and tanks including spares is roughly equal to the mass of the ISS Oxygen Generation Assembly (OGA) and its spares. Since the OGA must orbit Mars and be returned to Earth, while half the storage tanks are emptied on the way to Mars and can be abandoned, storage tanks have a significant launch mass advantage over the OGA. Storage tanks are simpler, more reliable,and have fewer failure modes than an OGA. They would have smaller design and development costs and need less crew time and maintenance. Oxygen storage tanks are feasible for Mars transit and are attractive compared to the ISS OGA.

Jones, Harry W.↗