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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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All sourcesNASA NTRSDOE OSTI
NASA NTRS2003

Technical Evaluation Report, Part A - Vortex Flow and High Angle of Attack

A symposium entitled Vortex Flow and High Angle of Attack was held in Loen, Norway, from May 7 through May 11, 2001. The Applied Vehicle Technology (AVT) panel, under the auspices of the Research and Technology Organization (RTO), sponsored this symposium. Forty-eight papers, organized into nine sessions, addressed computational and experimental studies of vortex flows pertinent to both aircraft and maritime applications. The studies also ranged from fundamental fluids investigations to flight test results, and significant results were contributed from a broad range of countries. The principal emphasis of this symposium was on "the understanding and prediction of separation-induced vortex flows and their effects on military vehicle performance, stability, control, and structural design loads." It was further observed by the program committee that "separation- induced vortex flows are an important part of the design and off-design performance of conventional fighter aircraft and new conventional or unconventional manned or unmanned advanced vehicle designs (UAVs, manned aircraft, missiles, space planes, ground-based vehicles, and ships)." The nine sessions addressed the following topics: vortical flows on wings and bodies, experimental techniques for vortical flows, numerical simulations of vortical flows, vortex stability and breakdown, vortex flows in maritime applications, vortex interactions and control, vortex dynamics, flight testing, and vehicle design. The purpose of this paper is to provide brief reviews of these papers along with some synthesizing perspectives toward future vortex flow research opportunities. The paper includes the symposium program. (15 refs.)

VORTEX BREAKDOWN↗
NASA NTRS1973

Statistical determination of space shuttle component dynamic magnification factors

A method is presented of obtaining vibration design loads for components and brackets. Dynamic Magnification Factors from applicable Saturn/Apollo qualification, reliability, and vibroacoustic tests have been statistically formulated into design nomographs. These design nomographs have been developed for different component and bracket types, mounted on backup structure or rigidly mounted and excited by sinusoidal or random inputs. Typical nomographs are shown.

Lehner, F.↗
NASA NTRS2015

Design Process of Flight Vehicle Structures for a Common Bulkhead and an MPCV Spacecraft Adapter

Design and manufacturing space flight vehicle structures is a skillset that has grown considerably at NASA during that last several years. Beginning with the Ares program and followed by the Space Launch System (SLS); in‐house designs were produced for both the Upper Stage and the SLS Multipurpose crew vehicle (MPCV) spacecraft adapter. Specifically, critical design review (CDR) level analysis and flight production drawing were produced for the above mentioned hardware. In particular, the experience of this in‐house design work led to increased manufacturing infrastructure for both Marshal Space Flight Center (MSFC) and Michoud Assembly Facility (MAF), improved skillsets in both analysis and design, and hands on experience in building and testing (MSA) full scale hardware. The hardware design and development processes from initiation to CDR and finally flight; resulted in many challenges and experiences that produced valuable lessons. This paper builds on these experiences of NASA in recent years on designing and fabricating flight hardware and examines the design/development processes used, as well as the challenges and lessons learned, i.e. from the initial design, loads estimation and mass constraints to structural optimization/affordability to release of production drawing to hardware manufacturing. While there are many documented design processes which a design engineer can follow, these unique experiences can offer insight into designing hardware in current program environments and present solutions to many of the challenges experienced by the engineering team.

Aggarwal, Pravin↗
NASA NTRS2009

Evaluation of Margins of Safety in Brazed Joints

One of the essential steps in assuring reliable performance of high cost critical brazed structures is the assessment of the Margin of Safety (MS) of the brazed joints. In many cases the experimental determination of the failure loads by destructive testing of the brazed assembly is not practical and cost prohibitive. In such cases the evaluation of the MS is performed analytically by comparing the maximum design loads with the allowable ones and incorporating various safety or knock down factors imposed by the customer. Unfortunately, an industry standard methodology for the design and analysis of brazed joints has not been developed. This paper provides an example of an approach that was used to analyze an AlBeMet 162 (38%Be-62%Al) structure brazed with the AWS BAlSi-4 (Al-12%Si) filler metal. A practical and conservative interaction equation combining shear and tensile allowables was developed and validated to evaluate an acceptable (safe) combination of tensile and shear stresses acting in the brazed joint. These allowables are obtained from testing of standard tensile and lap shear brazed specimens. The proposed equation enables the assessment of the load carrying capability of complex brazed joints subjected to multi-axial loading.

Flom, Yury↗
NASA NTRS1983

Environmental Control and Life Support for an evolutionary Space Station

The requirements for the Space Station are being defined. The Environmental Control/Life Support System (ECLSS) is one of its 13 systems. The ECLSS is further divided into five functional categories. Major ones are the Air Revitalization and Water Reclamation Systems. The paper presents ECLSS performance requirements, average design loads and fluids interfaces. The major cost savings of regenerable ECLSS techniques versus the open loop approach are quantified. Issues impacting ECLSS design are cited. Priority regenerable ECLSS developments are reviewed including the Electrochemical CO2 Concentrator, Static Feed Electrolyzer and Automated Control/Monitor Instrumentation. Baseline and alternative approaches are cited. The ECLSS planning issues are reviewed including functional boundaries, planning schedule, technology maturity definition and technology gaps. The paper concludes with a review of water electrolysis as a Space Station utility impacting ECLSS design.

Quattrone, P. D.↗
NASA NTRS1988

Optimum structural sizing for gust induced response

The present paper describes an optimization capability for sizing airframe structures that are subjected to a combination of deterministic and random loads. Design constraints are implemented to prevent structural failure in fatigue and due to a single exceedance of the allowable stress. The random load is treated as a stationary, homogeneous process with a Gaussian probability distribution, and a frequency domain method is used for the computation of dynamic response parameters. An equal-probability-of-load-combination criterion is proposed in the formulation of strength constraints. This alleviates problems associated with the incomplete phase information available when using power spectral density methods. The optimization procedure is illustrated by examples using typical built-up structures.

Hajela, P.↗
NASA NTRS1988

Active control law synthesis for flexible aircraft

An application of an active control law synthesis procedure is presented, to meet multiple design requirements for a flexible aircraft modeled by a large order state space system. In this synthesis procedure, a linear quadratic Gaussian type cost function is minimized by updating the free parameters of the control law, while satisfying a set of constraints on the design loads, responses and stability margins. Analytical expressions for gradients of the cost function and the constraints, with respect to the control law design variables are used to facilitate rapid numerical convergence. These gradients can also be used for sensitivity study. A stable classical control law as well as an estimator-based full or reduced order control law can be modified, in order to meet individual root-mean-square response limitations as well as minimum singular value restrictions. Both analog and digital control laws can be optimized. Low order, robust control laws were synthesized for flutter suppression of a flexible aircraft.

Mukhopadhyay, V.↗
NASA NTRS2014

Loads and Structural Dynamics Requirements for Spaceflight Hardware

The purpose of this document is to establish requirements relating to the loads and structural dynamics technical discipline for NASA and commercial spaceflight launch vehicle and spacecraft hardware. Requirements are defined for the development of structural design loads and recommendations regarding methodologies and practices for the conduct of load analyses are provided. As such, this document represents an implementation of NASA STD-5002. Requirements are also defined for structural mathematical model development and verification to ensure sufficient accuracy of predicted responses. Finally, requirements for model/data delivery and exchange are specified to facilitate interactions between Launch Vehicle Providers (LVPs), Spacecraft Providers (SCPs), and the NASA Technical Authority (TA) providing insight/oversight and serving in the Independent Verification and Validation role. In addition to the analysis-related requirements described above, a set of requirements are established concerning coupling phenomena or other interaction between structural dynamics and aerodynamic environments or control or propulsion system elements. Such requirements may reasonably be considered structure or control system design criteria, since good engineering practice dictates consideration of and/or elimination of the identified conditions in the development of those subsystems. The requirements are included here, however, to ensure that such considerations are captured in the design space for launch vehicles (LV), spacecraft (SC) and the Launch Abort Vehicle (LAV). The requirements in this document are focused on analyses to be performed to develop data needed to support structural verification. As described in JSC 65828, Structural Design Requirements and Factors of Safety for Spaceflight Hardware, implementation of the structural verification requirements is expected to be described in a Structural Verification Plan (SVP), which should describe the verification of each structural item for the applicable requirements. The requirement for and expected contents of the SVP are defined in JSC 65828. The SVP may also document unique verifications that meet or exceed these requirements with Technical Authority approval.

George James↗
NASA NTRS1981

Buffet loads on shuttle thermal-protection-system tiles

This paper presents results of wind-tunnel and acoustic tests to investigate buffet loads on Shuttle Thermal-Protection-System (TPS) tiles, It also describes the application of these results to the prediction of tile buffet loads for the first shuttle flight into orbit (STS-I). The wind-tunnel tests of tiles were conducted at transonic and supersonic Math numbers simulating flow regions on the Orbiter where shock waves and boundary-layer separations occur. The acoustic tests were conducted in a progressive wave tube at an overall sound pressure level (OASPL) approximately equal to the maximum OASPL measured during the wind-tunnel tests in a region of flow separation. The STS-I buffet load predictions yielded peak tile stresses due to buffeting, that were as much as 20 percent of the total stress for the design-load case when a shock wave was on a tile.

Charles F. Coe↗
NASA NTRS1989

Digital robust control law synthesis using constrained optimization

Development of digital robust control laws for active control of high performance flexible aircraft and large space structures is a research area of significant practical importance. The flexible system is typically modeled by a large order state space system of equations in order to accurately represent the dynamics. The active control law must satisy multiple conflicting design requirements and maintain certain stability margins, yet should be simple enough to be implementable on an onboard digital computer. Described here is an application of a generic digital control law synthesis procedure for such a system, using optimal control theory and constrained optimization technique. A linear quadratic Gaussian type cost function is minimized by updating the free parameters of the digital control law, while trying to satisfy a set of constraints on the design loads, responses and stability margins. Analytical expressions for the gradients of the cost function and the constraints with respect to the control law design variables are used to facilitate rapid numerical convergence. These gradients can be used for sensitivity study and may be integrated into a simultaneous structure and control optimization scheme.

Mukhopadhyay, Vivekananda↗
NASA NTRS1979

Wind Loads on Flat Plate Photovoltaic Array Fields

The aerodynamic forces resulting from winds acting on flat plate photovoltaic arrays were investigated. Local pressure distributions and total aerodynamic forces on the arrays are shown. Design loads are presented to cover the conditions of array angles relative to the ground from 20 deg to 60 deg, variable array spacings, a ground clearance gap up to 1.2 m (4 ft) and array slant heights of 2.4 m (8 ft) and 4.8 m (16 ft). Several means of alleviating the wind loads on the arrays are detailed. The expected reduction of the steady state wind velocity with the use of fences as a load alleviation device are indicated to be in excess of a factor of three for some conditions. This yields steady state wind load reductions as much as a factor of ten compared to the load incurred if no fence is used to protect the arrays. This steady state wind load reduction is offset by the increase in turbulence due to the fence but still an overall load reduction of 2.5 can be realized. Other load alleviation devices suggested are the installation of air gaps in the arrays, blocking the flow under the arrays and rounding the edges of the array. A wind tunnel test plan to supplement the theoretical study and to evaluate the load alleviation devices is outlined.

Miller, R.↗
NASA NTRS1946

Consideration of dynamic loads on the vertical tail by the theory of flat yawing maneuvers

Dynamic yawing effects on vertical-tail loads are considered by a theory of flat yawing maneuvers. A comparison is shown between computed loads and the loads measured in flight on a fighter airplane. The dynamic effects were investigated on a large flying boat for both an abrupt rudder deflection and sinusoidal rudder deflection. Only a moderate amount of control deflection was found to be necessary to attain the ultimate design load on the tail. In order to take into account dynamic effects in design, specifications of yawing maneuverability or control movement are needed.

Boshar, John↗
NASA NTRS1981

Shuttle tile environments and loads

This paper will discuss the Shuttle tile ascent environments and outline the procedures used to convert these environments into tile loads. Testing which was performed to quantify or verify the loads will also be discussed, along with the load combination rationale which was used. The discussion of the ascent environment will be limited to the transonic/supersonic portion of the mission since mechanical design loads occur during this time, and to specific regions of the vehicle, in particular those regions in which undensified critical (black) tiles are located. The induced environments can be broken down into three categories. The first of these are aerodynamic environments. These, in turn, are broken down into two categories-- (I) quasi-steady, which includes spatial surface pressure gradients, pressure differentials due to vent lag, and skin friction, and (2) the unsteady aerodynamics (aero-buffet). The second induced environment is defined as the vibration of the skin-stringer aluminum panels (hereafter referred to as the substrate) due to the acoustic environment. The third environment is defined as a quasi-steady substrate deflection, which results from in-plane and out-of-plane substrate loads.

Ralph J. Muraca↗
NASA NTRS2006

A 'Super Bowl' Approach to Mars Rover Touchdown Loads Analysis

Touchdown Driving Requirement: The mechanical system surface element shall be capable of facilitating a safe, stable landing at terrain angles up to 15 degrees, given an initial vertical velocity of 1 m/sec, horizontal velocity of 0.5 m/sec, and Z-axis spin rate of [4] deg/sec.Touchdown Loads Development: A multi-year development effort has been successfully conducted leading to an innovative analytical methodology for the prediction of rover touchdown design loads and the assessment of rover touchdown stability.

landing↗
NASA NTRS1946

Consideration of dynamic loads on the vertical tail by the theory of flat yawing maneuvers

Dynamic yawing effects on vertical tail loads are considered by a theory of flat yawing maneuvers. A comparison is shown between computed loads and the loads measured in flight in a fighter airplane. The dynamic effects were investigated on a large flying boat for both an abrupt rudder deflection and a sinusoidal rudder deflection. Only a moderate amount of control deflection was found to be necessary to attain the ultimate design load on the tail. In order to take into account dynamic effects in design, specifications of yawing maneuverability or control movement are needed.

Boshar, John↗
NASA NTRS1987

STA-2A NDT testing

The nondestructive testing (NDT) on the Space Shuttle Solid Rocket Booster (SRB) filament wound case (FWC) short stact structural test articles 2 (STA-2A) during test of phases 1B-9C is described. The primary objective of this testing was to verify the structural integrity of the SRB-FWC for critical design loads. Another objective was to quantify the effect of load distributions in the aft skirt. The NDT objectives were to determine the acoustic emission characteristics of the FWC-SRB and to identify possible design deficiencies or defect growth. The results from the posttest inspection of the samples shows the depth measurements taken were accurate until exceeding .260 inches thickness. The data then show that pulse echo measurements exceeded actual part thickness by 10 to 14 percent. The mapping of forward boundaries of delaminations proved to be within the tolerance of the equipment. Using the ZIP probe, the maximum difference between the pulse echo boundary and the visual boundary was expected to be no greater than one half the diameter of the probe. The NDT performance on STA-2A shows how NDT can be used to assist design engineering in evaluating the structural integrity of composite test articles.

Lewis, T. J.↗
NASA NTRS2016

International Docking Standard (IDSS) Interface Definition Document (IDD) : Revision - E

This International Docking System Standard (IDSS) Interface Definition Document (IDD) is the result of a collaboration by the International Space Station membership to establish a standard docking interface to enable on-orbit crew rescue operations and joint collaborative endeavors utilizing different spacecraft. This IDSS IDD details the physical geometric mating interface and design loads requirements. The physical geometric interface requirements must be strictly followed to ensure physical spacecraft mating compatibility. This includes both defined components and areas that are void of components. The IDD also identifies common design parameters as identified in section 3.0, e.g., docking initial conditions and vehicle mass properties. This information represents a recommended set of design values enveloping a broad set of design reference missions and conditions, which if accommodated in the docking system design, increases the probability of successful docking between different spacecraft. This IDD does not address operational procedures or off-nominal situations, nor does it dictate implementation or design features behind the mating interface. It is the responsibility of the spacecraft developer to perform all hardware verification and validation, and to perform final docking analyses to ensure the needed docking performance and to develop the final certification loads for their application. While there are many other critical requirements needed in the development of a docking system such as fault tolerance, reliability, and environments (e.g. vibration, etc.), it is not the intent of the IDSS IDD to mandate all of these requirements; these requirements must be addressed as part of the specific developer's unique program, spacecraft and mission needs. This approach allows designers the flexibility to design and build docking mechanisms to their unique program needs and requirements. The purpose of the IDSS IDD is to provide basic common design parameters to allow developers to independently design compatible docking systems. The IDSS is intended for uses ranging from crewed to autonomous space vehicles, and from Low Earth Orbit (LEO) to deep-space exploration missions.The purpose of the IDSS IDD is to provide basic common design parameters to allow developers to independently design compatible docking systems. The IDSS is intended for uses ranging from crewed to autonomous space vehicles, and from Low Earth Orbit (LEO) to deep-space exploration missions. The purpose of the IDSS IDD is to provide basic common design parameters to allow developers to independently design compatible docking systems. The IDSS is intended for uses ranging from crewed to autonomous space vehicles, and from Low Earth Orbit (LEO) to deep-space exploration missions.

docking↗