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At least 1,675 records · Page 93
All sourcesNASA NTRSDOE OSTI
NASA NTRS1958

A Flight Evaluation of the Factors which Influence the Selection of Landing Approach Speeds

The factors which influence the selection of landing approach speeds are discussed from the pilot's point of view. Concepts were developed and data were obtained during a landing approach flight investigation of a large number of jet airplane configurations which included straight-wing, swept-wing, and delta-wing airplanes as well as several applications of boundary-layer control. Since the fundamental limitation to further reductions in approach speed on most configurations appeared to be associated with the reduction in the pilot's ability to control flight path angle and airspeed, this problem forms the basis of the report. A simplified equation is presented showing the basic parameters which govern the flight path angle and airspeed changes, and pilot control techniques are discussed in relation to this equation. Attention is given to several independent aerodynamic characteristics which do not affect the flight path angle or airspeed directly but which determine to a large extent the effort and attention required of the pilot in controlling these factors during the approach. These include stall characteristics, stability about all axes, and changes in trim due to thrust adjustments. The report considers the relationship between piloting technique and all of the factors previously mentioned. A piloting technique which was found to be highly desirable for control of high-performance airplanes is described and the pilot's attitudes toward low-speed flight which bear heavily on the selection of landing approach speeds under operational conditions are discussed.

Drinkwater, Fred J., III↗
NASA NTRS2005

An Updated Assessment of NASA Ultra-Efficient Engine Technologies

NASA's Ultra Efficient Engine Technology (UEET) project features advanced aeropropulsion technologies that include highly loaded turbomachinery, an advanced low-NOx combustor, high-temperature materials, and advanced fan containment technology. A probabilistic system assessment is performed to evaluate the impact of these technologies on aircraft CO2 (or equivalent fuel burn) and NOx reductions. A 300-passenger aircraft, with two 396-kN thrust (85,000-lb) engines is chosen for the study. The results show that a large subsonic aircraft equipped with the current UEET technology portfolio has very high probabilities of meeting the UEET minimum success criteria for CO2 reduction (-12% from the baseline) and LTO (landing and takeoff) NOx reductions (-65% relative to the 1996 International Civil Aviation Organization rule).

Tong Michael T.↗
NASA NTRS2008

Ares I First Stage: Powering Exploration

he mission of the National Aeronautics and Space Administration (NASA) is not simply to maintain its current position with the International Space Station and other space exploration endeavors, but to build a permanent outpost on the Moon and then travel on to explore ever more distant terrains. The Constellation Program will oversee the development of the crew capsule, launch vehicles, and other systems needed to achieve this mission. From this initiative will come two new launch vehicles: the Ares I and Ares V. The Ares I will be a human-rated vehicle, which will be used for crew transport; the Ares V, a cargo transport vehicle, will be the largest launch vehicle ever built. The Ares Projects team at Marshall Space Flight Center (MSFC) in Huntsville, Alabama is assigned with developing these two new vehicles. The Ares I vehicle will have an in-line, two-stage rocket configuration. The first stage will provide the thrust or propulsion component for the Ares rocket systems through the first two minutes of the mission. The First Stage Team is tasked with developing the propulsion system necessary to liftoff from the Earth and loft the entire Ares vehicle stack toward low-Earth orbit. Building on the legacy of the Space Shuttle and other NASA space exploration initiatives, the propulsion for the Ares I First Stage will be a Shuttle-derived reusable solid rocket motor. Progress to date by the First Stage Team has been robust and on schedule. This presentation provides an overview and update on the design and development of the Ares I First Stage Propulsion system.

Tiller, Bruce K.↗
NASA NTRS2008

Progress on Ares First Stage Propulsion

The mission of the National Aeronautics and Space Administration (NASA) is not simply to maintain its current position with the International Space Station and other space exploration endeavors, but to build a permanent outpost on the Moon and then travel on to explore ever more distant terrains. The Constellation Program will oversee the development of the crew capsule, launch vehicles, and other systems needed to achieve this mission. From this initiative will come two new launch vehicles: the Ares I and Ares V. The Ares I will be a human-rated vehicle, which will be used for crew transport; the Ares V, a cargo transport vehicle, will be the largest launch vehicle ever built. The Ares Projects team at Marshall Space Flight Center (MSFC) in Huntsville, Alabama is assigned with developing these two new vehicles. The Ares I vehicle will have an in-line, two-stage rocket configuration. The first stage will provide the thrust or propulsion component for the Ares rocket systems through the first two minutes of the mission. The First Stage Team is tasked with developing the propulsion system necessary to liftoff from the Earth and loft the entire Ares vehicle stack toward low-Earth orbit. Building on the legacy of the Space Shuttle and other NASA space exploration initiatives, the propulsion for the Ares I First Stage will be a Shuttle-derived reusable solid rocket motor. Progress to date by the First Stage Team has been robust and on schedule. This paper provides an update on the design and development of the Ares First Stage Propulsion system.

Priskos, Alex S.↗
NASA NTRS2008

Progress on Ares First Stage Propulsion

The mission of the National Aeronautics and Space Administration (NASA) is not simply to maintain its current position with the International Space Station and other space exploration endeavors, but to build a permanent outpost on the Moon and then travel on to explore ever more distant terrains. The Constellation Program will oversee the development of the crew capsule, launch vehicles, and other systems needed to achieve this mission. From this initiative will come two new launch vehicles: the Ares I and Ares V. The Ares I will be a human-rated vehicle, which will be used for crew transport; the Ares V, a cargo transport vehicle, will be the largest launch vehicle ever built. The Ares Projects team at Marshall Space Flight Center (MSFC) in Huntsville, Alabama is assigned with developing these two new vehicles. The Ares I vehicle will have an inline, two-stage rocket configuration. The first stage will provide the thrust or propulsion component for the Ares rocket systems through the first two minutes of the mission. The First Stage Team is tasked with developing the propulsion system necessary to liftoff from the Earth and loft the entire Ares vehicle stack toward low-Earth orbit. Building on the legacy of the Space Shuttle and other NASA space exploration initiatives, the propulsion for the Ares I First Stage will be a Shuttle-derived reusable solid rocket motor. Progress to date by the First Stage Team has been robust and on schedule. This paper provides an update on the design and development of the Ares First Stage Propulsion system. The presentation provides an overview of the information presented in the paper.

Priskos, Alex S.↗
NASA NTRS2015

Methods for LEO Testing of CubeSat Propulsion Systems

Low Earth Orbit is becoming an inexpensive and readily available technology demonstration environment. Many new CubeSat technologies are taking advantage of this as an economical mechanism to advance beyond TRL 5. A wave of CubeSat propulsion systems favoring both reaction control and primary thrust will approach TRL 5 over the coming years, with some already there. These propulsion systems cover a wide range of capabilities including taking CubeSats to interplanetary destinations. In order to determine the feasibility of using LEO to validate the propulsion system performance and in doing so raising the TRL, a variety of factors need to be addressed. These factors include: method of measurement, environmental disturbances, spacecraft control states, and spacecraft mass properties. Propulsion Pathfinder is a NASA Ames Research Center lead project focused on raising the TRL of multiple propulsion systems over a series of flights in the coming years. This paper will highlight a few of the methods of measurement considered by this project to validate the performance of a propulsion system. The measurement methods range from tracking acceleration andor wheel spin-up to monitoring Two Line Elements between thrusting and non thrusting states. Focus will then be placed on the uncertainty of the measurement method and subsequently its feasibility through an analysis of LEO disturbance environment models and common CubeSat mass properties. In addition, the primary spacecraft control states and their imposition from the propulsion system are assessed.

Feasibility↗
NASA NTRS2023

Computational Study of Vortex-Induced Separation for a 5-Bladed Rotor

This work computationally investigated the rotor blade vortex-induced separation recently observed during an aerodynamic rotor test campaign in the NASA Langley Research Center 14- by 22-Foot Subsonic Tunnel. Two separate approaches (i.e., airfoil modification and blade tip modification) were studied to mitigate the vortex-induced separation. Low-fidelity tools based on blade element momentum theory were shown to mispredict the rotor inflow and were also shown to not capture the vortex-induced separation caused by perpendicular blade-vortex interaction. This misprediction was exploited to isolate the aerodynamic thrust deficit caused by the vortex-induced separation (i.e., 20%) from the thrust deficit due to inflow variation (i.e., 31%). High-fidelity tools were shown to reasonably predict aerodynamic forces within 13% and flow separation when compared to experimental results. The modified airfoil variant of the baseline rotor effectively mitigated the vortex-induced separation while the blade tip modified variant still showed separation, though the size and strength of the vortex was reduced. Acoustic predictions were underpredicted by 10 dB from preliminary measurements taken in the untreated wind tunnel. Broadband noise contributions from different rotor blade sections showed that self-noise due to flow separation and other turbulent boundary layer mechanisms was the dominant noise source for all three rotor cases, followed by blade-wake interaction noise caused by perpendicular blade-vortex interactions.

aerodynamics↗
NASA NTRS2004

Low-Cost, User-Friendly, Rapid Analysis of Dynamic Data System Established

An issue of primary importance to the development of new jet and certain other airbreathing combined-cycle powered aircraft is the advancement of airframe-integrated propulsion technologies. Namely, engine inlets and their systems and subsystems are required to capture, convert, and deliver the atmospheric airflow demanded by such engines across their operating envelope in a form that can be used to provide efficient, stable thrust. This must be done while also minimizing aircraft drag and weight. Revolutionary inlet designs aided by new technologies are needed to enable new missions. An unwanted byproduct of pursuing these inlet technologies is increased time-variant airflow distortion. Such distortions reduce propulsion system stability, performance, operability, and life. To countermand these limitations and fully evaluate the resulting configurations, best practices dictate that this distortion be experimentally measured at large scale and analyzed. The required measurements consist of those made by an array of high-response pressure transducers located in the flow field at the aerodynamic interface plane (AIP) between the inlet and engine. Although the acquisition of the necessary pitot-pressure time histories is relatively straight-forward, until recent years, the analysis has proved to be very time-consuming, tedious, and expensive. To transform the analysis of these data into a tractable and timely proposition, researchers at the NASA Glenn Research Center created and established the Rapid Analysis of Dynamic Data (RADD) system. The system provides complete, near real-time analysis of time-varying inlet airflow distortion datasets with report quality output. This fully digital approach employs Institute of Electrical and Electronics Engineers (IEEE) binary data file format standardization to establish data-acquisition-system-independent processing on low cost personal computers. Features include invalid instrumentation code-out, logging, and multiple replacement schemes as needed for each channel of instrumentation. The AIP pressure distribution can be interpolated to simulate measurements by alternate AIP probe arrays, if desired. In addition, the RADD system provides for the application of filters that can be used to focus the analysis on the frequency range of interest.

Arend, David J.↗
DOE OSTI2016

Cost-Benefit Analysis of High-Strength Materials for Safety-Related Nuclear Reinforced Concrete Shear Walls

A numerical parametric investigation was conducted to determine the economic benefits of utilizing high-strength concrete and high-strength steel reinforcing bar (rebar) in reinforced concrete (RC) shear walls for nuclear power plant structures. Thick RC shear walls with low height-to-length aspect ratios (i.e., aspect ratios, h{sub w}/l{sub w}≤2.0, where h{sub w} is the wall height and l{sub w} is the wall length) are the most common lateral load resisting members in non-containment, safety-related nuclear structures. Typically, the walls are reinforced with multiple layers of overlapping, large-diameter vertical and horizontal rebar on each face. These heavily-reinforced walls provide large lateral stiffness and strength to prevent significant deformations and/or cracking that could compromise the integrity of the nuclear facility. However, this design adversely affects constructability as the rebar cages become highly congested. The time, labor, and materials required for this construction lead to high overall project costs. There has been a recent research thrust in the U.S. to allow high-strength rebar in non-nuclear building structures. While some of this research (e.g., steel properties, bond, anchorage) is applicable to RC structures in general, there are important differences specific to nuclear structures, such as much thicker walls (often controlled by radiation and thermal cycling), larger reinforcement ratios, and increased susceptibility to shear-controlled behavior (due to low aspect ratios). An important limiting factor for non-nuclear structures in seismic regions is the reduced deformation capacity of high-strength rebar as compared with normal-strength rebar used in current practice. Differences in seismic design philosophy lessen this limitation for nuclear structures (i.e., nuclear structures are designed more conservatively and allowed to undergo significantly smaller nonlinear displacements), making high-strength rebar a promising alternative to reinforcement currently permissible in the ACI 349-13 code requirements, which govern the design of nuclear safety-related concrete structures. To improve constructability and economy, this study investigates the benefits of using high-strength rebar [i.e., ASTM A615 Grade 550 (U.S. Grade 80); ASTM A1035 Grades 690 and 830 (U.S. Grades 100 and 120), where the grade indicates the specified yield strength of the steel in MPa (ksi)] together with high-strength concrete [compression strengths up to 138 MPa (20.0 ksi)] in RC nuclear shear walls. These strength ranges represent steel and concrete materials that are commercially available in the U.S. High-strength rebar can significantly reduce the required steel areas, thereby reducing material/fabrication costs, reducing rebar congestion (fewer/smaller bars and bar layers), and facilitating concrete consolidation and placement. Previous research on the use of high-strength rebar and/or high-strength concrete in nuclear RC structures does not exist in North America. A recent study assessed the potential of high-strength steel to reduce the rebar volume in non-nuclear building construction. In Japan, researchers investigated the use of high-strength materials in safety-related nuclear RC structures, but did not explore the economic benefits of these materials. To address this knowledge gap, the current paper describes a numerical parametric investigation on the potential cost savings of nuclear shear walls with high-strength rebar and/or concrete through comparisons against state-of-practice walls with normal-strength materials. Overall, the results demonstrate that significant economic benefits can be realized by implementing high-strength rebar and concrete in these structures. (authors)

36 MATERIALS SCIENCE↗
NASA NTRS2020

Autonomous Assessment and Predictive Capabilities for Low-Altitude Urban Flight Operations

The integration of unmanned aerial vehicles in the national airspace will introduce new vehicle types, technologies, and operational paradigms for which safety must be maintained and hazards mitigated. One approach is to attempt to design for possible hazards and unsafe incidents that can occur at different phases of flight (pre-flight, in-flight, and post-flight) and during ground operations. Another is to mitigate safety incidents by implementing changes to policies, procedures, regulations, and design to cover personnel, equipment, and aircraft during operations. These and other techniques, not described herein, are typically conservative or adhoc in that they reduce the likelihood of risk after safety incidents have occurred. In this work, the goal is to develop a more predictive capability to monitor and mitigate risk and hazards to safety “in-time” enough for decisions to be made. In line with NASA’s Aeronautics Mission Directorate Strategic Thrust 5 [1] (In-Time System-Wide Safety Assurance), the System-Wide Safety (SWS) project under which this work falls, is developing and demonstrating innovative and safety-oriented solutions that enable modernization and aviation transformation. To that effect, this work will detail data-driven efforts on the SWS project to develop a number of safety-critical services for in-time monitoring and mitigation of hazards to low-altitude flight operations. First, hazards to these operations are identified based on previous work by NASA [2,3] and others in the aerospace industry. These hazards include (i) unsafe proximity to other vehicles, property, and people on the ground, (ii) critical system failures such as communication signal/GPS loss, unexpected propulsion system degradation, engine/power failure, and (iii) operational/environmental issues such as severe weather and gusty winds. For these hazards, safety metrics, which can be quantified and assessed are defined, models to monitor and predict them are developed, and flight test data is generated to develop, validate, and test these models, considering the complex interplay of the different hazards that define them [4-6]. In addition, the uncertainty in the non-deterministic effects that cannot be modeled nor predicted and unknown unknowns that arise after design/testing and during operations must be handled in rigorous manner. As a result, for each of the developed safety metrics, their dependencies on one another are characterized and a framework for handling the uncertainties inherent in the modeling, algorithms, and measurements required for prediction is also developed [7]. To that effect, this presentation will describe the safety metrics and services already developed and underway under the System-Wide Safety project that utilize data-driven techniques for the identification of anomalies, precursors, and trends (APTs) to monitor and mitigate hazards to safety, in-time, for urban flight operations in low-altitude airspace.

Okolo, Wendy A.↗
DOE OSTI2021

Aspects of rare earth element enrichment in Allegheny Plateau coals, Pennsylvania, USA

The Allegheny Plateau in western Pennsylvania, western Maryland, and northern West Virginia has relatively flat-lying strata with southwest-northeast-trending anticlines cored by splay faults originating from the thrust faults and southeast-northwest-trending lineaments. The lineaments define both the structural relief of the anticlines and the coal rank. Coal rank in the Pennsylvanian Allegheny Group coals is medium volatile bituminous in the region of less-prominent structural relief and low volatile bituminous in the region with more pronounced anticlines. Zinc and Cl exhibit high values in coals in the vicinity of the lineaments. Although coal rank was not a parameter in the Principal components analysis, the highest rank coals clustered together in a quadrant defined, in part, by the Zn concentration. Zinc was selected as a parameter due to its possible link with hydrothermal mineralization and Zr and TiO 2 /Al 2 O 3 were selected based on their presumed association with detrital mineral influences. The highest rare earths + Y values in benches of the Lower Kittanning coal were found at sites close to the lineaments. Negative or negligible Ce anomalies (δCe) and strongly positive Gd anomalies (δGd) suggest marine or hydrothermal influences and negative Eu anomalies (δEu) along with high TiO 2 /Al 2 O 3 values suggest a terrestrial input. In conclusion, the plots of δCe vs. δGd and δCe vs. δEu show that the low volatile bituminous coals are segregated from the other coals, suggesting that the factors that influenced coal rank also influenced the distribution of the rare earth elements.

58 GEOSCIENCES↗
DOE OSTI2020

CPAP Ventilators Needed for Rapid Response to COVID-19 by Modification of CPAP Equipment

Early on in the COVID-19 pandemic, potential ventilator shortages were a critical issue identified by national health care providers. Capacity modeling at the time suggested patient demand may exceed ventilator supply. Thus, the challenge became finding an urgent interim solution to meet health care needs. Our initial hypothesis was that CPAP technology could be modified to provide similar functionality to a ventilator, relieving demand and allowing physicians to decide which patients need high end machines, ultimately saving lives. In conjunction with medical experts and pulmonologists, we were able to identify three key thrusts associated with this research problem: (1) modification of CPAP technology to allow for 02 input that would be capable of providing ventilation; (2) development of an alarming function that would provide real-time audible alarms to alert medical personnel to critical conditions, which would be used inline with CPAP technology; and (3) a method of sterilizing expiratory air from such a system in order to protect medical personnel from biohazard, since CPAPs vent to the atmosphere. We were unable to realize results for thrust 1 (CPAP modification for 02); we identified potential safety issues associated with utilizing medical grade oxygen with a common CPAP device. In order to characterize and mitigate these issues, we would need to partner closely with a device manufacturer; such a partnership could not be achieved in the timeframe needed for this rapid response work. However, we determined that some medical grade BiPAP devices do not need this modification and that the significant progress on thrusts 2 and 3 would be sufficient to buy down risk of a massive ventilator shortage. Our team built a prototype alarm system that can be utilized with any assistive respiratory device to alert on all key conditions identified by medical personnel (high pressure, low pressure, apnea, loss of power, low battery). Finally, our team made significant progress in the rapid prototyping and demonstration of an inline UV air purifier device. The device is cost efficient and can be manufactured at scale with both commercially available and additively manufactured parts. Initial tests with SARS-CoV-2 analog bacteriophage MS2 show 99% efficacy at reducing bioburden. Following a successful demonstration of the prototype device with medical personnel, we were able to obtain follow-on (non-LDRD) funding to provide additional device characterization, validation, and production in order to respond to an immediate regional need.

42 ENGINEERING↗
NASA NTRS1975

Rotorcraft low-speed download drag definition and its reduction

Download drag for rotorcraft in hover and low-speed flight is a burden which significantly affects useful load, fuel, and payload. Reduction of the burden will enhance these aspects of rotorcraft and complement the forthcoming improvements in isolated rotor performance. Analyses and experimental data are available, though fragmentary, regarding gross drag, thrust recovery, and other characteristics which can be utilized to define interim rotorcraft design changes to reduce the burden. Eventually the experimental data and a comprehensive combination of rotor, rotor-wake, and potential-flow analyses can evolve to reduce the burden to an absolute minimum.

Wilson, J. C.↗
NASA NTRS1980

Advanced materials for space

The principal thrust of the LSST program is to develop the materials technology required for confident design of large space systems such as antennas and platforms. Areas of research in the FY-79 program include evaluation of polysulfones, measurement of the coefficient of thermal expansion of low expansion composite laminates, thermal cycling effects, and cable technology. The development of new long thermal control coatings and adhesives for use in space is discussed. The determination of radiation damage mechanisms of resin matrix composites and the formulation of new polymer matrices that are inherently more stable in the space environment are examined.

Tenney, D. R.↗
NASA NTRS1985

Status of advanced orbital transfer propulsion

A new Orbital Transfer Vehicle (OTV) propulsion system that will be used in conjunction with the Space Shuttle, Space Station and Orbit Maneuvering Vehicle is discussed. The OTV will transfer men, large space structures and conventional payloads between low Earth and higher energy orbits. Space probes carried by the OTV will continue the exploration of the solar system. When lunar bases are established, the OTV will be their transportation link to Earth. Critical engine design considerations based upon the need for low cost payload delivery, space basing, reusability, aeroassist maneuvering, low g transfers of large space structures and man rating are described. The importance of each of these to propulsion design is addressed. Specific propulsion requirements discussed are: (1) high performance H2/O2 engine; (2) multiple engine configurations totalling no more than 15,000 lbf thrust 15 to 20 hr life; (3) space maintainable modular design; (4) health monitoring capability; and (5) safety and mission success with backup auxiliary propulsion.

Cooper, L. P.↗
NASA NTRS1985

Introduction - The space infrastructure

This book focuses on the Space Station and its associated platforms, which are the central and most visible space facilities in the thrust toward establishing a permanent presence in space. Facilities cannot be operated in isolation, however, and must have transportation for access. This is particularly true for space facilities. In order to attain the goal of permanent presence in space, the Space Station and its low altitude platforms must be developed and operated with transportation for routine access to and from the earth; local transportation between the Space Station, its platforms, and other low altitude satellites; and long-range transportation between low and geostationary orbits, and escape orbits. In addition, geostationary facilities and habitation elements must also be developed. It is in such an assembly of space facilities and transportation elements that will be vested the capabilities to service the earth, establish bases on the moon or planets, and eventually move beyond.

Bekey, I.↗
NASA NTRS1985

Status of advanced orbital transfer propulsion

A new Orbital Transfer Vehicle (OTV) propulsion system that will be used in conjunction with the Space Shuttle, Space Station and Orbit Maneuvering Vehicle is discussed. The OTV will transfer men, large space structures and conventional payloads between low earth and higher energy orbits. Space probes carried by the OTV will continue the exploration of the solar system. When lunar bases are established, the OTV will be their transportation link to earth. Critical engine design considerations based upon the need for low cost payload delivery, space basing, reusability, aeroassist maneuvering, low g transfers of large space structures and man rating are described. The importance of each of these to propulsion design is addressed. Specific propulsion requirements discussed are: (1) high performance H2/O2 engine; (2) multiple engine configurations totalling no more than 15,000 lbf thrust 15 to 20 hr life; (3) space maintainable modular design; (4) health monitoring capability; and (5) safety and mission success with backup auxiliary propulsion.

Cooper, L. P.↗
NASA NTRS1993

Performance assessment of low pressure nuclear thermal propulsion

An increase in Isp for nuclear thermal propulsion systems is desirable for reducing the propellant requirements and cost of future applications, such as the Mars Transfer Vehicle. Several previous design studies have suggested that the Isp could be increased substantially with hydrogen dissociation/recombination. Hydrogen molecules (H2), at high temperatures and low pressures, will dissociate to monatomic hydrogen (H). The reverse process (i.e., formation of H2 from H) is exothermic. The exothermic energy in a nozzle increases the kinetic energy and therefore, increases the Isp. The low pressure nuclear thermal propulsion system (LPNTP) system is expected to maximize the hydrogen dissociation/recombination and Isp by operating at high chamber temperatures and low chamber pressures. The process involves hydrogen flow through a high temperature, low pressure fission reactor, and out a nozzle. The high temperature (approximately 3000 K) of the hydrogen in the reactor is limited by the temperature limits of the reactor material. The minimum chamber pressure is about 1 atm because lower pressures decrease the engines thrust to weight ratio below acceptable limits. This study assumes that hydrogen leaves the reactor and enters the nozzle at the 3000 K equilibrium dissociation level. Hydrogen dissociation in the reactor does not affect LPNTP performance like dissociation in traditional chemical propulsion systems, because energy from the reactor resupplies energy lost due to hydrogen dissociation. Recombination takes place in the nozzle due primarily to a drop in temperature as the Mach number increases. However, as the Mach number increases beyond the nozzle throat, the static pressure and density of the flow decreases and minimizes the recombination. The ideal LPNTP Isp at 3000 K and 10 psia is 1160 seconds due to the added energy from fast recombination rates. The actual Isp depends on the finite kinetic reaction rates which affect the amount of monatomic hydrogen recombination before the flow exits the nozzle. A LPNTP system has other technical issues (e.g. flow instability and two-phase flow) besides hydrogen dissociation/recombination which affect the systems practicality. In this study, only the effects of hydrogen dissociation/recombination are examined.

Gerrish, Harrold P., Jr.↗