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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 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

CFD Predictions of Fluctuating Pressure Environments on NASA’s SLS Ascent Unsteady Aerodynamics Wind Tunnel Test

This paper details work that is being conducted on predicting fluctuating pressure environments on NASA launch vehicles using computational fluid dynamics (CFD). The accurate characterization of these aeroacoustics environments is necessary in the analysis of vehicle structural health and aerodynamic performance and in the vehicle design process. High-fidelity simulations of the unsteady flow over NASA’s SLS Ascent Unsteady Aerodynamics wind tunnel Test (AUAT) using the hybrid Reynolds-averaged Navier-Stokes (RANS)-large eddy simulations (LES) methodologies in Mississippi States’ Loci/CHEM solver are presented. The two available methods, Nelson-Nichols and dynamic hybrid RANS-LES (DHRL), are compared head-to-head on identical grids at two Mach numbers. At the high-subsonic Mach number, locally supersonic flow expanding over a shoulder induces a separation-reattachment system that is predicted poorly by the Nelson-Nichols method due to an under-prediction in unsteady content. The DHRL solution predicts the spatial extent and frequency domain response of this system well but under-predicts the peak noise levels due to a delay in the RANS-to-LES transition. At the low-supersonic Mach number, compression corner dynamics dominate the unsteady flow. While the Nelson Nichols solution captures this phenomenon well, another solution on a refined grid indicates that some model stress depletion is occurring. The DHRL solution again performs well at this Mach number and matches the wind tunnel data fairly closely, but perhaps most impressively, is fairly agnostic to increasing grid resolution. The findings in this paper are expected to be generally applicable and will be used to guide the prediction of aeroacoustics environments of other NASA launch vehicles.

CFD↗
NASA NTRSDate not supplied

An Initial Electric Motor Rotor Vibration Model

Ongoing integration of outrunner brushless electric motors into drones and Advanced Air Mobility aircraft presents a need for accurate acoustic predictions derived from prediction of the motor rotor vibrations. In outrunner motors, the external rotor vibrates and drives the acoustic field. At resonant frequencies of the rotor, the rotor displacements will be the largest. The vibrations can lead to acoustic tones that are relevant to the overall acoustic design of these types of vehicles. This study performs a finite element analysis to assess the modes in two electric motor rotors. This model is then refined into a simple parameterized geometry that can make the same predictions for motors of the same class. A parametric sweep and least-squares-curve fit to the finite element analysis data results in a series of simple curves that can predict the mode shapes and frequencies that are likely to appear in this class of motors without the need for any simulation. The simulations are validated by comparison to acoustic and experimental modal-analysis data.

Electric Motor Noise↗
NASA NTRSDate not supplied

Re-Creation of an Apollo-Era Separation Anomaly Using a Low-g Slosh Mechanical Analog

Recent interest in sending humans to the lunar and martian surfaces has led to spacecraft designs with large ratios of liquid propellant to dry mass. Large amounts of liquid propellant can lead to significant coupling between the rigid-body dynamics of the spacecraft and the motion, or slosh, of the liquid within its propellant tank. These spacecraft-propellant interactions can degrade the performance of the vehicle; therefore, a thorough analysis of the impact of slosh is required. The interactions that take place in a low-g environment, which is characterized by small relative accelerations between the spacecraft and its propellants, are of particular interest since the study of low-g slosh is a complicated undertaking and remains an active area of research.

low-g slosh↗
NASA NTRSDate not supplied

Linear Covariance Techniques to Analyze a Multi-Vehicle, Multi-GN&C System with Applications to Rendezvous in a Near Rectilinear Halo Orbit

Typically for a rendezvous and docking scenario, only a single vehicle is considered the active vehicle. As a result, the target vehicle’s GN&C system is typically not a factor in the integrated performance analysis as it assumes a passive role. However, for upcoming NASA Artemis missions the active vehicle is both the chaser and target spacecraft. In addition, both vehicles are cooperating with one another, sharing telemetry data, and relying on data extracted from the GN&C system of the other. The process also includes a team of ground support personnel in mission control are tracking and monitoring each spacecraft uplinking state estimates and targeting solutions to support mission operations and enhance the onboard flight system performance. Being able to quickly analyze the impact of both vehicles with two different GN&C systems that also interact with the ground that does its own navigation and targeting uploads is critical. This paper outlines how to perform this rapid analysis using linear covariance techniques and applies them to a rendezvous scenario initiated in low lunar orbit and completed in a Near Rectilinear Halo Orbit (NRHO) representative of the NASA Artemis III mission.

Linear Covariance Analysis↗
NASA NTRS2009

International Space Station USOS Crew Quarters Ventilation and Acoustic Design Implementation

The International Space Station (ISS) United States Operational Segment (USOS) has four permanent rack sized ISS Crew Quarters (CQ) providing a private crewmember space. The CQ uses Node 2 cabin air for ventilation/thermal cooling, as opposed to conditioned ducted air from the ISS Temperature Humidity Control System or the ISS fluid cooling loop connections. Consequently, CQ can only increase the air flow rate to reduce the temperature delta between the cabin and the CQ interior. However, increasing airflow causes increased acoustic noise so efficient airflow distribution is an important design parameter. The CQ utilized a two fan push-pull configuration to ensure fresh air at the crewmember s head position and reduce acoustic exposure. The CQ interior needs to be below Noise Curve 40 (NC-40). The CQ ventilation ducts are open to the significantly louder Node 2 cabin aisle way which required significantly acoustic mitigation controls. The design implementation of the CQ ventilation system and acoustic mitigation are very inter-related and require consideration of crew comfort balanced with use of interior habitable volume, accommodation of fan failures, and possible crew uses that impact ventilation and acoustic performance. This paper illustrates the types of model analysis, assumptions, vehicle interactions, and trade-offs required for CQ ventilation and acoustics. Additionally, on-orbit ventilation system performance and initial crew feedback is presented. This approach is applicable to any private enclosed space that the crew will occupy.

Broyan, James Lee, Jr.↗
NASA NTRS1988

Results of an integrated structure-control law design sensitivity analysis

Next generation air and space vehicle designs are driven by increased performance requirements, demanding a high level of design integration between traditionally separate design disciplines. Interdisciplinary analysis capabilities have been developed, for aeroservoelastic aircraft and large flexible spacecraft control for instance, but the requisite integrated design methods are only beginning to be developed. One integrated design method which has received attention is based on hierarchal problem decompositions, optimization, and design sensitivity analyses. This paper highlights a design sensitivity analysis method for Linear Quadratic Cost, Gaussian (LQG) optimal control laws, which predicts change in the optimal control law due to changes in fixed problem parameters using analytical sensitivity equations. Numerical results of a design sensitivity analysis for a realistic aeroservoelastic aircraft example are presented. In this example, the sensitivity of the optimally controlled aircraft's response to various problem formulation and physical aircraft parameters is determined. These results are used to predict the aircraft's new optimally controlled response if the parameter was to have some other nominal value during the control law design process. The sensitivity results are validated by recomputing the optimal control law for discrete variations in parameters, computing the new actual aircraft response, and comparing with the predicted response. These results show an improvement in sensitivity accuracy for integrated design purposes over methods which do not include changess in the optimal control law. Use of the analytical LQG sensitivity expressions is also shown to be more efficient that finite difference methods for the computation of the equivalent sensitivity information.

Gilbert, Michael G.↗
NASA NTRS2010

Evaluation of Dual-Launch Lunar Architectures Using the Mission Assessment Post Processor

The National Aeronautics and Space Administrations (NASA) Constellation Program is currently designing a new transportation system to replace the Space Shuttle, support human missions to both the International Space Station (ISS) and the Moon, and enable the eventual establishment of an outpost on the lunar surface. The present Constellation architecture is designed to meet nominal capability requirements and provide flexibility sufficient for handling a host of contingency scenarios including (but not limited to) launch delays at the Earth. This report summarizes a body of work performed in support of the Review of U.S. Human Space Flight Committee. It analyzes three lunar orbit rendezvous dual-launch architecture options which incorporate differing methodologies for mitigating the effects of launch delays at the Earth. NASA employed the recently-developed Mission Assessment Post Processor (MAPP) tool to quickly evaluate vehicle performance requirements for several candidate approaches for conducting human missions to the Moon. The MAPP tool enabled analysis of Earth perturbation effects and Earth-Moon geometry effects on the integrated vehicle performance as it varies over the 18.6-year lunar nodal cycle. Results are provided summarizing best-case and worst-case vehicle propellant requirements for each architecture option. Additionally, the associated vehicle payload mass requirements at launch are compared between each architecture and against those of the Constellation Program. The current Constellation Program architecture assumes that the Altair lunar lander and Earth Departure Stage (EDS) vehicles are launched on a heavy lift launch vehicle. The Orion Crew Exploration Vehicle (CEV) is separately launched on a smaller man-rated vehicle. This strategy relaxes man-rating requirements for the heavy lift launch vehicle and has the potential to significantly reduce the cost of the overall architecture over the operational lifetime of the program. The crew launch occurs first, four days prior to the optimal trans-lunar injection (TLI) departure window. This is done to allow for launch delays in the Altair/EDS launch. During this time, the Orion vehicle is required to conduct orbit maintenance while loitering in low Earth orbit (LEO). The alternative architectures presented aim to eliminate the need for costly orbit maintenance maneuvers while loitering in LEO. In all of the alternative architectures considered, it is assumed that the Altair and Orion vehicles are nominally launched 90 minutes apart, depart the Earth separately, and complete the rendezvous and docking sequence at the Moon. In this lunar orbit rendezvous (LOR) strategy, both the Altair and Orion vehicles will require separate EDS stages, and each will be required to perform lunar orbit insertion (LOI). This has the effect of balancing payload requirements between the two launch vehicles at the Earth. In this case, the overall payload mass is increased slightly, but the increased mission costs could potentially be offset by requiring the construction of two rockets similar in size and nature, unlike the current Constellation architecture. Three dual-launch architecture options with LOR were evaluated, which incorporate differing methodologies for mitigating the effects of launch delays at the Earth. Benefits and drawbacks of each of the dual-launch architecture options with LOR are discussed and the overall mission performance is compared with that of the existing Constellation Program lunar architecture.

Stewart, Shaun M.↗
NASA NTRS2014

Space Shuttle Launch Probability Analysis: Understanding History so We Can Predict the Future

The Space Shuttle was launched 135 times and nearly half of those launches required 2 or more launch attempts. The Space Shuttle launch countdown historical data of 250 launch attempts provides a wealth of data that is important to analyze for strictly historical purposes as well as for use in predicting future launch vehicle launch countdown performance. This paper provides a statistical analysis of all Space Shuttle launch attempts including the empirical probability of launch on any given attempt and the cumulative probability of launch relative to the planned launch date at the start of the initial launch countdown. This information can be used to facilitate launch probability predictions of future launch vehicles such as NASA's Space Shuttle derived SLS. Understanding the cumulative probability of launch is particularly important for missions to Mars since the launch opportunities are relatively short in duration and one must wait for 2 years before a subsequent attempt can begin.

Cates, Grant R.↗
NASA NTRS2006

The Role of Flight Experiments in the Development of Cryogenic Fluid Management Technologies

This paper reviews the history of cryogenic fluid management technology development and infusion into both the Saturn and Centaur vehicles. Ground testing and analysis proved inadequate to demonstrate full scale performance. As a consequence flight demonstration with a full scale vehicle was required by both the Saturn and Centaur programs to build confidence that problems were addressed. However; the flight vehicles were highly limited on flight instrumentation and the flight demonstration locked-in the design without challenging the function of design elements. Projects reviewed include: the Aerobee Sounding Rocket Cryogenic Fluid Management (CFM) tests which served as a valuable stepping stone to flight demonstration and built confidence in the ability to handle hydrogen in low gravity; the Saturn IVB Fluid Management Qualification flight test; the Atlas Centaur demonstration flights to develop two burn capability; and finally the Titan Centaur two post mission flight tests.

Chato, David J.↗
NASA NTRSDate not supplied

NASA Reference Motor Designs for Electric Vertical Takeoff and Landing Vehicles

Electric and hybrid electric vertical takeoff and landing vehicles require high performance and high reliability electric motor drivetrains. Failure analysis of NASA’s Revolutionary Vertical Lift Technologies’ reference vehicles pointed to current electric motor drivetrain reliability being below what is needed to meet the expected stringent reliability requirements for Urban Air Mobility vehicles. In this paper, design studies are carried out for UAM vehicle electric motors to produce reference designs. The primary intent of these reference motor designs is to provide guidance for UAM motor reliability model development and technology advancement. They additionally provide high fidelity motor sizing information for vehicle designers and references for different technologies or motor topologies to be traded against.

Electric Motor Urban Air Mobility↗
NASA NTRSDate not supplied

NASA Reference Motor Designs for Electric Vertical Takeoff and Landing Vehicles

Electric and hybrid electric vertical takeoff and landing vehicles require high performance and high reliability electric motor drivetrains. Failure analysis of NASA’s Revolutionary Vertical Lift Technologies’ reference vehicles pointed to current electric motor drivetrain reliability being below what is needed to meet the expected stringent reliability requirements for Urban Air Mobility vehicles [1]. In this paper, design studies are carried out for UAM vehicle electric motors to produce reference designs. The primary intent of these reference motor designs is to provide guidance for UAM motor reliability model development and technology advancement. They additionally provide high fidelity motor sizing information for vehicle designers and references for different technologies or motor topologies to be traded against.

Thomas Tallerico↗
NASA NTRS1990

Active control of aerothermoelastic effects for a conceptual hypersonic aircraft

Procedures for and results of aeroservothermoelastic studies are described. The objectives of these studies were to develop the necessary procedures for performing an aeroelastic analysis of an aerodynamically heated vehicle and to analyze a configuration in the classical cold state and in a hot state. Major tasks include the development of the structural and aerodynamic models, open loop analyses, design of active control laws for improving dynamic responses and analyses of the closed loop vehicles. The analyses performed focused on flutter speed calculations, short period eigenvalue trends and statistical analyses of the vehicle response to controls and turbulence. Improving the ride quality of the vehicle and raising the flutter boundary of the aerodynamically-heated vehicle up to that of the cold vehicle were the objectives of the control law design investigations.

Heeg, Jennifer↗
NASA NTRS1990

Active control of aerothermoelastic effects for a conceptual hypersonic aircraft

This paper describes the procedures for an results of aeroservothermoelastic studies. The objectives of these studies were to develop the necessary procedures for performing an aeroelastic analysis of an aerodynamically heated vehicle and to analyze a configuration in the classical 'cold' state and in a 'hot' state. Major tasks include the development of the structural and aerodynamic models, open loop analyses, design of active control laws for improving dynamic responses and analyses of the closed loop vehicles. The analyses performed focused on flutter speed calculations, short period eigenvalue trends and statistical analyses of the vehicle response to controls and turbulence. Improving the ride quality of the vehicle and raising the flutter boundary of the aerodynamically-heated vehicle up to that of the cold vehicle were the objectives of the control law design investigations.

Heeg, Jennifer↗
NASA NTRS2020

Pterodactyl: The Development and Performance of Guidance Algorithms for a Mechanically Deployed Entry Vehicle

Pterodactyl is a NASA Space Technology Mission Directorate (STMD) project focused on developing a design capability for optimal, scalable, Guidance and Control (G&C) solutions that enable precision targeting for Deployable Entry Vehicles (DEVs). This feasibility study is unique in that it focuses on the rapid integration of targeting performance analysis with structural & packaging analysis, which is especially challenging for new vehicle and mission designs. This paper will detail the guidance development and trajectory design process for a lunar return mission, selected to stress the vehicle designs and encourage future scalability. For the five G&C configurations considered, the Fully Numerical Predictor-Corrector Entry Guidance (FNPEG) was selected for configurations requiring bank angle guidance and FNPEG with Uncoupled Range Control (URC) was developed for configurations requiring angle of attack and sideslip angle guidance. Successful G&C configurations are defined as those that can deliver payloads to the intended descent and landing initiation point, while abiding by trajectory constraints for nominal and dispersed trajectories.

Johnson, Breanna J.↗
NASA NTRS1986

Thrust vectoring for single-stage-to-orbit, horizontal takeoff, horizontal landing, space vehicles

The preliminary design of a horizontal takeoff, horizontal landing, single-stage-to-orbit, rocket-powered space vehicle was performed. The purpose was to examine technology requirements for future small payload launch vehicles. The distinguishing aspect of the design was the utilization of thrust vectoring to provide half of the lift at takeoff. The inclusion of a canard was necessary to provide additional lift at takeoff and to balance the moments produced with thrust vectoring. A weights estimation, an aerodynamic assessment, a trajectory analysis, and a gear weight analysis were performed. The takeoff weight of the resulting vehicle was approximately 1.26 million pounds, based on advanced technology structures and subsystems. The vehicle was designed to deliver a 5000-pound payload to a polar orbit.

Cunningham, M. J.↗
NASA NTRS2013

Launch Vehicle Abort Analysis for Failures Leading to Loss of Control

Launch vehicle ascent is a time of high risk for an onboard crew. There is a large fraction of possible failures for which time is of the essence and a successful abort is possible if the detection and action happens quickly enough. This paper focuses on abort determination based on data already available from the Guidance, Navigation, and Control system. This work is the result of failure analysis efforts performed during the Ares I launch vehicle development program. The two primary areas of focus are the derivation of abort triggers to ensure that abort occurs as quickly as possible when needed, but that false aborts are avoided, and evaluation of success in aborting off the failing launch vehicle.

Hanson, John M.↗
NASA NTRS1975

Investigation of lightweight designs and materials for LO2 and LH2 propellant tanks for space vehicles, phase 1

Design, analysis, and fabrication studies were performed on nonintegral (suspended) tanks using a representative space tug design. The LH2 and LO2 tank concept selection was developed. Tank geometries and support relationships were investigated using tug design propellant inertias and ullage pressures, then compared based on total tug systems effects. The tank combinations which resulted in the maximum payload were selected. Tests were conducted on samples of membrane material which was processed in a manner simulating production tank fabrication operations to determine fabrication effects on the fracture toughness of the tank material. Fracture mechanics analyses were also performed to establish a preliminary set of allowables for initial defects.

Source record↗
NASA NTRS1986

Evaluation of a Stirling engine heater bypass with the NASA Lewis nodal-analysis performance code

In support of the U.S. Department of Energy's Stirling Engine Highway Vehicle Systems program, the NASA Lewis Research Center investigated whether bypassing the P-40 Stirling engine heater during regenerative cooling would improve engine performance. The Lewis nodal-analysis Stirling engine computer simulation was used for this investigation. Results for the heater-bypass concept showed no significant improvement in the indicated thermal efficiency for the P-40 Stirling engine operating at full-power and part-power conditions. Optimizing the heater tube length produced a small increase in the indicated thermal efficiency with the heater-bypass concept.

Sullivan, T. J.↗