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The Communications link analysis and simulation system (CLASS)

The Communications Link Analysis and Simulation System (CLASS) is a comprehensive, computerized communications and tracking system analysis tool under development by the Networks Directorate of the NASA/GSFC. The primary use of this system is to provide the capability to predict the performance of the Tracking and Data Relay Satellite system (TDRSS) User Communications and Tracking links through the TDRSS. The general capabilities and operational philosophy of the current and final versions of the CLASS are described along with some examples of analyses which have been performed utilizing the capabilities of this system.

Godfrey, R. D.

Simulation and analysis of flexibly jointed manipulators

Modeling, simulation, and analysis of robot manipulators with non-negligible joint flexibility are studied. A recursive Newton-Euler model of the flexibly jointed manipulator is developed with many advantages over the traditional Lagrange-Euler methods. The Newton-Euler approach leads to a method for the simulation of a flexibly jointed manipulator in which the number of computations grows linearly with the number of links. Additionally, any function for the flexibility between the motor and link may be used permitting the simulation of nonlinear effects, such as backlash, in a uniform manner for all joints. An analysis of the control problems for flexibly jointed manipulators is presented by converting the Newton-Euler model to a Lagrange-Euler form. The detailed structure available in the model is used to examine linearizing controllers and shows the dependency of the control on the choice of flexible model and structure of the manipulator.

Murphy, Steve H.

Large perturbation flow field analysis and simulation for supersonic inlets

An analysis technique for simulation of supersonic mixed compression inlets with large flow field perturbations is presented. The approach is based upon a quasi-one-dimensional inviscid unsteady formulation which includes engineering models of unstart/restart, bleed, bypass, and geometry effects. Numerical solution of the governing time dependent equations of motion is accomplished through a shock capturing finite difference algorithm, of which five separate approaches are evaluated. Comparison with experimental supersonic wind tunnel data is presented to verify the present approach for a wide range of transient inlet flow conditions.

Varner, M. O.

Modeling techniques used in the communications link analysis and simulation system (CLASS)

CLASS (Communications Link Analysis and Simulation System) is a software package developed for NASA to predict the communication and tracking performance of the Tracking and Data Relay Satellite System (TDRSS) services. The modeling techniques used in CLASS are described. The components of TDRSS and the performance parameters to be computed by CLASS are too diverse to permit the use of a single technique to evaluate all performance measures. Hence, each CLASS module applies the modeling approach best suited for a particular subsystem and/or performance parameter in terms of model accuracy and computational speed.

Braun, W. R.

Validation of the communications link analysis and simulation system (CLASS)

CLASS (Communication Link Analysis and Simulation System) is a software package developed for NASA to predict the communication and tracking performance of the Tracking and Data Relay Satellite System (TDRSS) services. The methods used to verify CLASS are described. The usefulness of a software tool such as CLASS depends strongly on the reliability and accuracy of the results it produces. For this reason, considerable attention was paid to validation throughout the CLASS development.

Braun, W. R.

User's manual for the Simulated Life Analysis of Vehicle Elements (SLAVE) model

The simulated life analysis of vehicle elements model was designed to perform statistical simulation studies for any constant loss rate. The outputs of the model consist of the total number of stages required, stages successfully completing their lifetime, and average stage flight life. This report contains a complete description of the model. Users' instructions and interpretation of input and output data are presented such that a user with little or no prior programming knowledge can successfully implement the program.

Paul, D. D., Jr.

A STOL airworthiness investigation using a simulation of an augmentor wing transport. Volume 2: Simulation data and analysis

A simulator study of STOL airworthiness was conducted using a model of an augmentor wing transport. The approach, flare and landing, go-around, and takeoff phases of flight were investigated. The simulation and the data obtained are described. These data include performance measures, pilot commentary, and pilot ratings. A pilot/vehicle analysis of glide slope tracking and of the flare maneuver is included.

Heffley, R. K.

Mars 2020 Perseverance Entry Descent and Landing Simulation Statistical Analysis and Operations

On February 18, 2021, the Perseverance rover and Ingenuity helicopter demonstra- tion landed at Jezero Crater. The Entry, Descent, and Landing (EDL) architecture, largely the same used to land Curiosity at Gale Crater on August 6, 2012, required high-fidelity flight dynamics simulation with two independent tools to verify per- formance. The process for creating the EDL simulation using the Dynamics Sim- ulator for Entry, Descent and Surface landing (DSENDS) tool will be discussed, along with its use for for independent verification of the EDL statistical analy- sis results and reference trajectory simulation. Analysis and usage details both in development and cruise, along with post-landing assessment of the prediction performance of the simulation, will also be discussed.

"O'Farrell, Clara"

The Advanced Modeling, Simulation and Analysis Capability Roadmap Vision for Engineering

This paper summarizes a subset of the Advanced Modeling Simulation and Analysis (AMSA) Capability Roadmap that was developed for NASA in 2005. The AMSA Capability Roadmap Team was chartered to "To identify what is needed to enhance NASA's capabilities to produce leading-edge exploration and science missions by improving engineering system development, operations, and science understanding through broad application of advanced modeling, simulation and analysis techniques." The AMSA roadmap stressed the need for integration, not just within the science, engineering and operations domains themselves, but also across these domains. Here we discuss the roadmap element pertaining to integration within the engineering domain, with a particular focus on implications for future observatory missions. The AMSA products supporting the system engineering function are mission information, bounds on information quality, and system validation guidance. The Engineering roadmap element contains 5 sub-elements: (1) Large-Scale Systems Models, (2) Anomalous Behavior Models, (3) advanced Uncertainty Models, (4) Virtual Testing Models, and (5) space-based Robotics Manufacture and Servicing Models.

Zang, Thomas

Numerical simulation and analysis of a prefrontal squall line. I - Observations and basic simulation results. II - Propagation of the squall line as an internal gravity wave

Results of an observational and numerical study of the squall line that occurred on June 17-18, 1978, are presented. This squall line was initially triggered by the strong surface convergence along a cold front and stretched from Illinois to the Texas Panhandle. The squall line was aligned with the surface front during its initial development, but then propagated faster than the front, resulting in a separation of approximately 200 km by 0300 UTC and 300-400 km by 0600 UTC. The Colorado State University Regional Atmospheric Modeling System is used to model the squall-line development and propagation. Results are described from several experiments that tested the sensitivity to the use of the Kuo-type cumulus parameterization scheme and grid-scale microphysical processes. The movement of the squall line in the model is shown to be due to the propagation of a deep tropospheric internal gravity wave in a CISK-like process. The thermal and dynamic perturbations associated with the hypothesized wave are shown to be consistent with internal gravity wave theory.

Cram, Jennifer M.

Analysis Results for Lunar Soil Simulant Using a Portable X-Ray Fluorescence Analyzer

Lunar soil will potentially be used for oxygen generation, water generation, and as filler for building blocks during habitation missions on the Moon. NASA s in situ fabrication and repair program is evaluating portable technologies that can assess the chemistry of lunar soil and lunar soil simulants. This Technical Memorandum summarizes the results of the JSC 1 lunar soil simulant analysis using the TRACeR III IV handheld x-ray fluorescence analyzer, manufactured by KeyMaster Technologies, Inc. The focus of the evaluation was to determine how well the current instrument configuration would detect and quantify the components of JSC-1.

Boothe, R. E.

Improvements to the Flight Analysis and Simulation Tool (FAST) and Initial Development of the Genesis Flight Mechanics Simulation for Ascent, Aerocapture, Entry, Descent, and Landing (A2EDL) Trajectory Design

The NASA Engineering and Safety Center (NESC) was requested to provide significant enhancements to the Flight Analysis and Simulation Tool (FAST), a generic, variable-degree-of-freedom, multi-body ascent, aerocapture, entry, descent, and landing (A2EDL) flight simulation code and a key Agency analysis tool. This report details the upgrades to FAST that were completed, describes a change to the assessment’s scope that allowed its goals to be exceeded with a new and innovative approach, and discusses the results of the modified approach.

NASA Engineering and Safety Center; Flight Analysi