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NASA NTRS2002

Comparisons of Kinematics and Dynamics Simulation Software Tools

Kinematic and dynamic analyses for moving bodies are essential to system engineers and designers in the process of design and validations. 3D visualization and motion simulation plus finite element analysis (FEA) give engineers a better way to present ideas and results. Marshall Space Flight Center (MSFC) system engineering researchers are currently using IGRIP from DELMIA Inc. as a kinematic simulation tool for discrete bodies motion simulations. Although IGRIP is an excellent tool for kinematic simulation with some dynamic analysis capabilities in robotic control, explorations of other alternatives with more powerful dynamic analysis and FEA capabilities are necessary. Kinematics analysis will only examine the displacement, velocity, and acceleration of the mechanism without considering effects from masses of components. With dynamic analysis and FEA, effects such as the forces or torques at the joint due to mass and inertia of components can be identified. With keen market competition, ALGOR Mechanical Event Simulation (MES), MSC visualNastran 4D, Unigraphics Motion+, and Pro/MECHANICA were chosen for explorations. In this study, comparisons between software tools were presented in terms of following categories: graphical user interface (GUI), import capability, tutorial availability, ease of use, kinematic simulation capability, dynamic simulation capability, FEA capability, graphical output, technical support, and cost. Propulsion Test Article (PTA) with Fastrac engine model exported from IGRIP and an office chair mechanism were used as examples for simulations.

Yeu-Sheng Paul Shiue↗

NASA NTRSDate not supplied

Sliding Mode Transient Scaling Controller for Gas Turbine Engine Emulation on an Electric Machine

The testing of hybrid-electric aircraft propulsion system components and control strategies has dictated the need for a low-cost gas turbine engine (GTE) emulation testbed. Within that testbed, electric machines (EMs) are used to emulate the dynamics of a GTE. GTE mathematical models are used to provide control torque commands to EMs. Most GTEs operate at much higher power levels than commercially available EMs. Therefore, the transient shaft dynamics of the GTE must be scaled appropriately. The sliding mode controller being presented here aims to deliver a control torque to an electric machine with a fixed inertia that will allow it to mimic the response of a GTE with a different inertia. This solution provides an easily scalable and tunable transient emulation method without having to scale the GTE mathematical model and/or add inertia to the physical EM shaft. This controller has been proven in simulation to produce nearly identical transient rotational speed response to a reference GTE shaft model which has a large difference in rotational inertia compared to the motor. Also, the inherent robustness of the sliding mode control scheme results in negligible changes in performance for large amounts of parameter uncertainty while minimizing high frequency fluctuations in the control signal.

sliding mode↗

NASA NTRS2016

Structural Design Considerations for a 50 kW-Class Solar Array for NASA's Asteroid Redirect Mission

NASA is planning an Asteroid Redirect Mission (ARM) to take place in the 2020s. To enable this multi-year mission, a 40 kW class solar electric propulsion (SEP) system powered by an advanced 50 kW class solar array will be required. Powered by the SEP module (SEPM), the ARM vehicle will travel to a large near-Earth asteroid, descend to its surface, capture a multi-metric ton (t) asteroid boulder, ascend from the surface and return to the Earth-moon system to ultimately place the ARM vehicle and its captured asteroid boulder into a stable distant orbit. During the years that follow, astronauts flying in the Orion multipurpose crew vehicle (MPCV) will dock with the ARM vehicle and conduct extra-vehicular activity (EVA) operations to explore and sample the asteroid boulder. This paper will review the top structural design considerations to successfully implement this 50 kW class solar array that must meet unprecedented performance levels. These considerations include beyond state-of-the-art metrics for specific mass, specific volume, deployed area, deployed solar array wing (SAW) keep in zone (KIZ), deployed strength and deployed frequency. Analytical and design results are presented that support definition of stowed KIZ and launch restraint interface definition. An offset boom is defined to meet the deployed SAW KIZ. The resulting parametric impact of the offset boom length on spacecraft moment of inertias and deployed SAW quasistatic and dynamic load cases are also presented. Load cases include ARM spacecraft thruster plume impingement, asteroid surface operations and Orion docking operations which drive the required SAW deployed strength and damping. The authors conclude that to support NASA's ARM power needs, an advanced SAW is required with mass performance better than 125 W/kg, stowed volume better than 40 kW/cu m, a deployed area of 200 sq m (100 sq m for each of two SAWs), a deployed SAW offset distance of nominally 3-4 m, a deployed SAW quasistatic strength of nominally 0.1 g in any direction, a deployed loading displacement under 2 m, a deployed fundamental frequency above 0.1 Hz and deployed damping of at least 1%. These parameters must be met on top of challenging mission environments and ground testing requirements unique to the ARM project.

solar arrays↗

NASA NTRS1989

Preliminary results on noncollocated torque control of space robot actuators

In the Space Station era, more operations will be performed robotically in space in the areas of servicing, assembly, and experiment tending among others. These robots may have various sets of requirements for accuracy, speed, and force generation, but there will be design constraints such as size, mass, and power dissipation limits. For actuation, a leading motor candidate is a dc brushless type, and there are numerous potential drive trains each with its own advantages and disadvantages. This experiment uses a harmonic drive and addresses some inherent limitations, namely its backdriveability and low frequency structural resonances. These effects are controlled and diminished by instrumenting the actuator system with a torque transducer on the output shaft. This noncollocated loop is closed to ensure that the commanded torque is accurately delivered to the manipulator link. The actuator system is modelled and its essential parameters identified. The nonlinear model for simulations will include inertias, gearing, stiction, flexibility, and the effects of output load variations. A linear model is extracted and used for designing the noncollocated torque and position feedback loops. These loops are simulated with the structural frequency encountered in the testbed system. Simulation results are given for various commands in position. The use of torque feedback is demonstrated to yield superior performance in settling time and positioning accuracy. An experimental setup being finished consists of a bench mounted motor and harmonic drive actuator system. A torque transducer and two position encoders, each with sufficient resolution and bandwidth, will provide sensory information. Parameters of the physical system are being identified and matched to analytical predictions. Initial feedback control laws will be incorporated in the bench test equipment and various experiments run to validate the designs. The status of these experiments is given.

Tilley, Scott W.↗

NASA NTRS1983

Space platform attitude control system

A discussion is presented of the preliminary design of the Space Platform System, which is being developed to support the Shuttle Orbiter in a sortie configuration with power, communications, and thermal and attitude control capability for up to 30 days while supporting payloads within the Shuttle bay or mounted directly on the platform. Three payload pallets can be supported for indefinite periods of time by the platform in a free flier mode. The vehicle is stabilized against gravity gradients and aerodynamic disturbance torques by the attitude control system. The attitude control system requirements are stringent, due to the need to counteract large aerodynamic disturbances despite the large platform size and low earth orbit altitude. The design of the control system allows it to control both free fly and sortie configurations, with differing inertias as payload pallets are changed.

Levinthal, J.↗

NASA NTRS1987

Optimization of payload mass placement in a dual keel space station

In order to keep a Space Station in a stable low-Earth orbit, angular momentum storage and translational attitude control systems will have to be used. In order to minimize the size of these attitude control systems, the induced gravity gradient torque effects will have to be minimized. This can be done by minimizing the cross-products of inertia of the Station through the management of payload placement with the Station geometry. A derived and automated methodology is presented which utilizes mathematical nonlinear programming techniques. An optimal arrangement of a set of five payloads on a Dual Keel Space Station was found that minimized the cross products of inertia and thus the required controllability resources.

Ferebee, Melvin J., Jr.↗

NASA NTRS2004

Transition from Pool to Flow Boiling: The Effect of Reduced Gravity

Applications of boiling heat transfer in space can be found in the areas of thermal management, fluid handling and control, power systems, on-orbit storage and supply systems for cryogenic propellants and life support fluids, and for cooling of electronic packages for power systems associated with various instrumentation and control systems. Recent interest in exploration of Mars and other planets, and the concepts of in-situ resource utiliLation on Mars highlights the need to understand the effect of gravity on boiling heat transfer at gravity levels varying from 1>= g/g(sub e) >=10(exp -6). The objective of the proposed work was to develop a mechanistic understanding of nucleate boiling and critical heat flux under low and micro-gravity conditions when the velocity of the imposed flow is small. For pool boiling, the effect of reduced gravity is to stretch both the length scale as well as the time scale for the boiling process. At high flow velocities, the inertia of the liquid determines the time and the length scales and as such the gravitational acceleration plays little role. However, at low velocities and at low gravity levels both liquid inertia and buoyancy are of equal importance. At present, we have little understanding of the interacting roles of gravity and liquid inertia on the nucleate boiling process. Little data that has been reported in the literature does not have much practical value in that it can not serve as a basis for design of heat exchange components to be used in space. Both experimental and complete numerical simulations of the low velocity, low-gravity nucleate boiling process were carried out. A building block type of approach was used in that first the growth and detachment process of a single bubble and flow and heat transfer associated with the sliding motion of the bubble over the heater surface after detachment was studied. Liquid subcooling and flow velocity were varied parametrically. The experiments were conducted at 1 g(sub e), while varying the orientation of surface with respect to the gravity vector. In the laboratory experiments, holographic interferometry was used to obtain data on velocity and temperature fields associated with a bubble prior to, and after detachment and during sliding motion. A test rig for conducting experiments in the KC-135 was developed, but experiments could not be conducted due to the unavailability of the aircraft prior to completion of the project. Numerical simulations modeling the micro and macro regions of the bubble were carried out in three dimensions. The results of the experiments were used to validate analytical/numerical models.

Dhir, Vijay K.↗

NASA NTRS1992

Project Wish: The Emerald City, phase 3

Phase 3 of Project Wish saw the evolution of the Emerald City (E-City) from a collection of specialized independent analyses and ideas to a working structural design integrated with major support systems and analyses. Emphasis was placed on comparing and contrasting the closed and open cycle gas core nuclear rocket engines to further determine the optimum propulsive system for the C-City. Power and thermal control requirements were then defined and the question of how to meet these requirements was addressed. Software was developed to automate the mission/system/configuration analysis so changes dictated by various subsystems constraints could be managed efficiently and analyzed interactively. In addition, the liquid hydrogen propellant tank was statically designed for minimum mass and shape optimization using a finite element modeling package called SDRC I-DEAS while spoke and shaft cross-sectional areas were optimized on ASTROS (Automated Structural Optimization System). A structural dynamic analysis also conducted using ASTROS enabled a study of the displacements, accelerations, modes and frequencies of the C-City. Finally, the attitude control system design began with an initial mass moment of inertia analysis and was then designed and optimized using linear quadratic regulator control theory.

Source record↗

NASA NTRS1991

A Rocket Powered Single-Stage-to-Orbit Launch Vehicle With U.S. and Soviet Engineers

A single-stage-to-orbit launch vehicle is used to assess the applicability of Soviet Energia high-pressure-hydrocarbon engine to advanced U.S. manned space transportation systems. Two of the Soviet engines are used with three Space Shuttle Main Engines. When applied to a baseline vehicle that utilized advanced hydrocarbon engines, the higher weight of the Soviet engines resulted in a 20 percent loss of payload capability and necessitated a change in the crew compartment size and location from mid-body to forebody in order to balance the vehicle. Various combinations of Soviet and Shuttle engines were evaluated for comparison purposes, including an all hydrogen system using all Space Shuttle Main Engines. Operational aspects of the baseline vehicle are also discussed. A new mass properties program entitles Weights and Moments of Inertia (WAMI) is used in the study.

MacConochie, Ian O.↗

NASA NTRS1992

Project WISH: The Emerald City

Phase 3 of Project WISH saw the evolution of the Emerald City (E-City) from a collection of specialized independent analyses and ideas to a working structural design integrated with major support systems and analyses. Emphasis was placed on comparing and contrasting the closed and open cycle gas core nuclear rocket engines to further determine the optimum propulsive system for the E-City. Power and thermal control requirements were then defined and the question of how to meet these requirements was addressed. Software was developed to automate the mission/system/configuration analysis so changes dictated by various subsystem constraints could be managed efficiently and analyzed interactively. In addition, the liquid hydrogen propellant tank was statically designed for minimum mass and shape optimization using a finite element modeling package called SDRC I-DEAS. Spoke and shaft cross-sectional areas were optimized on ASTROS (Automated Structural Optimization System) for mass minimization. A structural dynamic analysis of the optimal structure also conducted using ASTROS enabled a study of the modes, frequencies, displacements, and accelerations of the E-City. Finally, the attitude control system design began with an initial mass moment of inertia analysis and was then designed and optimized using linear quadratic regulator control theory.

Oz, Hayrani↗

NASA NTRS2004

MOBI and FEANICS Programming in Labview

The flight software engineering branch provides design and development of embedded real-time software applications for flight and supporting ground systems to support the NASA Aeronautics and Space Programs. In addition, this branch evaluates, develops and implements new technologies for embedded real-time systems, and maintains a laboratory for applications of embedded technology. This branch supports other divisions and is involved with many other projects. My mentor Rochelle and I are involved in the Fluids and Combustion Facility (FCF) project, the MOBI project, and the FEANICS project. The Fluids and Combustion Facility (FCF) will occupy two powered racks on the International Space Station (ISS). It will be a permanent modular, multiuser facility to accommodate microgravity science experiments onboard the ISS's U.S. Laboratory Module. FCF will support NASA Human Exploration and Development of Space program objectives requiring sustained, systematic research in the disciplines of fluid physics and combustion science. The fluids experiment is called FIR and the combustion experiment is called CIR. The MOBI Experiment is an experiment that is performed to understand the physics of bubble segregation and resuspension in an inertia, monodisperse gas-liquid suspension, and to understand how bubble pressure resists segregation in suspensions with continuous phase inertia. The main focus of FEANICS and the solid combustion experiments will be to conduct basic and applied scientific investigations in fire-safety to support NASA's Bioastronautics Initiative. Based on data obtained in microgravity and experience gained from the beginning of the U.S. manned space program, these normal gravity flammability assessments have been assumed to be conservative with respect to flammability in all environments. However, some of the complex interactions that govern ignition and flame growth can only be evaluated in the long durations of microgravity available on the ISS. Before any of these projects actually go to the ISS, they are going to be tested on NASA's KC-135 Low-G airplane, the KC-135 Low-G Flight Research aircraft (a predecessor of the Boeing 707) is used to fly parabolas to create 20-25 seconds of weightlessness so that the astronauts can experience and researchers can investigate the effects of zero gravity. My mentor and I have been working with Labview to write the programs that are going to acquire, analyze and present the data acquired from these Test flights on the KC-135. We have been working closely with electrical, and mechanical engineers to make sure the program and the hardware can communicate and perform the operations necessary for the flight test. LabVIEW delivers a powerful graphical development environment for signal acquisition, measurement analysis, and data presentation, giving you the flexibility of a programming language without the complexity of traditional development tools. The programming of the control panel and the code are both done in GUIs which allow for flexibility in the code and the program.

Rios, Jeffrey N.↗

NASA NTRS2015

Attitude Ground System (AGS) for the Magnetospheric Multi-Scale (MMS) Mission

MMS Overview Recall from Conrads presentation earlier today MMS launch: March 13, 2015 on an Atlas V from Space Launch Complex 40, Cape Canaveral, Florida MMS Observatory Separation: five minute intervals spinning at 3 rpm approximately 1.5 hours after launch MMS Science Goals: study magnetospheric plasma physics and understand the processes that cause power grids, communication disruptions and Aurora formation Mission: 4 identical spacecraft in tetrahedral formation with variable size1.2 x 12 RE in Phase 1, with apogee on dayside to observe bow shock1.2 x 25 RE in Phase 2, with apogee on night side to observe magneto tail Challenges Tight attitude control box, orbit and formation maintenance requirements Maneuvers on thrusters every two weeks Delta-H Spin axis direction and spin rate maintenance Delta-V Orbit and Formation maintenance Mission phase transitions AGS support Smart targeting prediction of Spin-Axis attitude in the presence of environmental torques to stay within the science attitude Determination of the spacecraft attitude and spin rate (sensitive to knowledge of inertia tensor)Calibrations to improve attitude determination results and improve orbit maneuvers Mass properties (Center of Mass, and inertia tensor for nutation and coning) Accelerometer bias (sensitive to the accuracy of the rate estimates) Sensor alignments.

Estimation and Calibration Support↗

NASA NTRS1993

The Effects of Neutral Inertia on Ionospheric Currents in the High-Latitude Thermosphere Following a Geomagnetic Storm

Results of an experimental and theoretical investigation into the effects of the time dependent neutral wind flywheel on high-latitude ionospheric electrodynamics are presented. The results extend our previous work which used the National Center for Atmospheric Research Thermosphere/Ionosphere General Circulation Model (NCAR TIGCM) to theoretically simulate flywheel effects in the aftermath of a geomagnetic storm. The previous results indicated that the neutral circulation, set up by ion-neutral momentum coupling in the main phase of a geomagnetic storm, is maintained for several hours after the main phase has ended and may dominate height-integrated Hall currents and field-aligned currents for up to 4-5 hours. We extend the work of Deng et al. to include comparisons between the calculated time-dependent ionospheric Hall current system in the storm-time recovery period and that measured by instruments on board the Dynamics Explorer 2 (DE 2) satellite. Also, comparisons are made between calculated field-aligned currents and those derived from DE 2 magnetometer measurements. These calculations also allow us to calculate the power transfer rate (sometimes called the Poynting flux) between the magnetosphere and ionosphere. The following conclusions have been drawn: (1) Neutral winds can contribute significantly to the horizontal ionospheric current system in the period immediately following the main phase of a geomagnetic storm, especially over the magnetic polar cap and in regions of ion drift shear. (2) Neutral winds drive Hall currents that flow in the opposite direction to those driven by ion drifts. (3) The overall morphology of the calculated field-aligned current system agrees with previously published observations for the interplanetary magnetic field (IMF) B(sub Z) southward conditions, although the region I and region 2 currents are smeared by the TI(ICM model grid resolution. (4) Neutral winds can make significant contributions to the field-aligned current system when B(sub Z) northward conditions prevail following the main phase of a storm, but can account for only a fraction of the observed currents. (5) DE 2 measurements provide a demonstration of "local" (satellite-altitude) flywheel effects. (6) On the assumption that the magnetosphere acts as an insulator, we calculate neutral-wind-induced polarization electric fields of approx. 20-30 kV in the period immediately following the geomagnetic storm.

Deng, W.↗

NASA NTRS1990

Dynamic Characteristics of Space Station Freedom Mars and Lunar Evolution Reference Configurations

One concept for a manned mission to Mars uses an evolutionary version of Space Station Freedom (SSF) as a transportation node. The station is modified by the addition of dual keels, an upper and lower boom, additional laboratory and habitation modules, increased power and an assembly platform. With these modifications the station is called the Mars Evolution Reference Configuration (MERC). The mass of the station is 65 percent greater than the mass of SSF and its moments of inertia through the mass center are greater by approximately a factor of four. Over a period of months, several flights from Earth to low-Earth-orbit carry the components of a manned Mars piloted vehicle (MPV) to the MERC where the vehicle is constructed on the assembly platform. After each flight the station is reboosted to an appropriate altitude, such that the orbit decay due to atmospheric drag forces lowers the spacecraft to the proper altitude at the appropriate time for rendezvous with the next assembly flight. When the assembly process is completed, the MPV, which has a mass of approximately 200,000 lbm, is situated on the evolutionary station. The mass increase of the MERC with MPV system over SSF is 112 percent and the moments of inertia about axes through the mass center increase by up to a factor of 12. When the MPV is assembled, inspected and verified, the mission is ready to proceed and the MPV is moved from the station to a staging area and mated with fueled trans-Mars injection stages for the flight to Mars. This presentation describes a finite element model of the MERC formulated to investigate the expected low frequency modes and its variation with the addition of a large payload. A basic reboost procedure using near-continuous firing of reaction control system jets is proposed with off-modulation of the jets used to control flight attitude. The reboost procedure is described with the closed-loop attitude control dictating jet on/off cycling based on feedback signals which contain both the rigid body rotation information and the elastic rotations local to the attitude sensor. The presentation contains a description of the dynamic response at critical points of the station during the reboost and concludes with results of a brief study of the dynamic characteristics of a Lunar transportation node configuration.

Ayers, J. Kirk↗

NASA NTRS1957

Analog-computer investigation of effects of friction and preload on the dynamic longitudinal characteristics of a pilot-airplane combination

With an electric analog computer, an investigation has been made of the effects of control frictions and preloads on the transient longitudinal response of a fighter airplane during abrupt small attitude corrections. The simulation included the airplane dynamics, powered control system, feel system, and a simple linearized pseudopilot. Control frictions at the stick pivot and at the servo valve as well as preloads of the stick and valve were considered individually and in combinations. It is believed that the results which are presented in the form of time histories and vector diagrams present a more detailed illustration of the effects of stray forces and compensating forces in the longitudinal control system than has previously been available. Consistent with the results of previous studies, the present results show that any of thesefour friction and preload forces caused some deterioration of the response. However, even a small amount of valve friction caused an oscillatory pitching response during which the phasing of the valve friction was such that it caused energy to be fed into the pitching oscillation of the airplane. Of the other friction and preload forces which were considered, it was found that stick preload was close to 180 degrees out of phase with valve friction and thus could compensate in large measure for valve friction as long as the cycling of the stick encompassed the trim point. Either stick friction or valve preload provided a smaller stabilizing effect primarily through a reduction in the amplitude of the resultant force vector acting on the control system. Some data were obtained on the effects of friction when the damping or inertia of the control system or the pilot lag was varied.

Crane, Harold L↗

NASA NTRS1961

Analog-Computer Investigation of Effects of Friction and Preload on the Dynamic Longitudinal Characteristics of a Pilot-Airplane Combination

With an electric analog computer, an investigation has been made of the effects of control frictions and preloads on the transient longitudinal response of a fighter airplane during abrupt small attitude corrections. The simulation included the airplane dynamics, powered control system, feel system, and a simple linearized pseudopilot. Control frictions at the stick pivot and at the servo valve as well as preloads of the stick and valve were considered individually and in combinations. It is believed that the results which are presented in the form of time histories and vector diagrams present a more detailed illustration of the effects of stray forces and compensating forces in the longitudinal control system than has previously been available. Consistent with the results of previous studies, the present results show that any of these four friction and preload forces caused some deterioration of the response. However, even a small amount of valve friction caused an oscillatory pitching response during which the phasing of the valve friction was such that it caused energy to be fed into the pitching oscillation of the air-plane. Of the other friction and preload forces which were considered, it was found that stick preload was close to 180 deg. out of phase with valve friction and thus could compensate in large measure for valve friction as long as the cycling of the stick encompassed the trim point. Either stick friction or valve preload provided a smaller stabilizing effect primarily through a reduction in the amplitude of the resultant force vector acting on the control system. Some data were obtained on the effects of friction when the damping or inertia of the control system or the pilot lag was varied.

Crane, Harold L.↗

NASA NTRS2017

Osiris-REx Spacecraft Current Status and Forward Plans

The NASA New Frontiers OSIRIS-REx spacecraft executed a flawless launch on September 8, 2016 to begin its 23-month journey to near-Earth asteroid (101955). The primary objective of the OSIRIS-REx mission is to collect and return to Earth a pristine sample of regolith from the asteroid surface. The sampling event will occur after a two-year period of remote sensing that will ensure a high probability of successful sampling of a region on the asteroid surface having high science value and within well-defined geological context. The OSIRIS-REx instrument payload includes three high-resolution cameras (OCAMS), a visible and near-infrared spectrometer (OVIRS), a thermal imaging spectrometer (OTES), an X-ray imaging spectrometer (REXIS), and a laser altimeter (OLA). As the spacecraft follows its nominal outbound-cruise trajectory, the propulsion, power, communications, and science instruments have undergone basic functional tests, with no major issues. Outbound cruise science investigations include a search for Earth Trojan asteroids as the spacecraft approaches the Sun-Earth L4 Lagrangian point in February 2017. Additional instrument checkouts and calibrations will be carried out during the Earth gravity assist maneuver in September 2017. During the Earth-moon flyby, visual and spectral images will be acquired to validate instrument command sequences planned for Bennu remote sensing. The asteroid Bennu remote sensing campaign will yield high resolution maps of the temperature and thermal inertia, distributions of major minerals and concentrations of organic matter across the asteroid surface. A high resolution 3d shape model including local surface slopes and a high-resolution gravity field will also be determined. Together, these data will be used to generate four separate maps that will be used to select the sampling site(s). The Safety map will identify hazardous and safe operational regions on the asteroid surface. The Deliverability map will quantify the accuracy with which the navigation team can deliver the spacecraft to and from specific sites on the asteroid surface. The Sampleability map quantifies the regolith properties, providing an estimation of how much material would be sampled at different points on the surface. The final Science Value map synthesizes the chemical, mineralogical, and geological, observations to identify the areas of the asteroid surface with the highest science value. Here, priority is given to organic, water-rich regions that have been minimally altered by surface processes. Asteroid surface samples will be acquired with a touch-and-go sample acquisition system (TAGSAM) that uses high purity pressurized N2 gas to mobilize regolith into a stainless steel canister. Although the mission requirement is to collect at least 60 g of material, tests of the TAGSAM routinely exceeded 300 g of simulant in micro-gravity tests. After acquiring the sample, the spacecraft will depart Bennu in 2021 to begin its return journey, with the sample return capsule landing at the Utah Test and Training Range on September 23, 2023. The OSIRIS-REx science team will carry out a series of detailed chemical, mineralogical, isotopic, and spectral studies that will be used to determine the origin and history of Bennu and to relate high spatial resolution sample studies to the global geological context from remote sensing. The outline of the sample analysis plan is described in a companion abstract.

Messenger, Scott↗

NASA NTRSDate not supplied

Comparison of Orion Flywheel to Commercially Available Flywheel Device

INTRODUCTION: The chosen exercise device for the Orion Multi-purpose Crew Vehicle (MPCV) for Artemis missions is the Orion Flywheel (OFW), which was selected in 2017 from a pool of exercise devices. The Orion Flywheel is to be installed in the MPCV for its first use during the Artemis II mission and will be utilized for subsequent Artemis missions. The OFW provides the capability to perform both resistive and aerobic exercises while taking up a small volume and not requiring power. Aerobic exercise consists of rowing while resistive exercise includes the deadlift, harness squat, and deadlift high pull among others. The efficacy of the OFW as an exercise countermeasure to spaceflight deconditioning has not yet been fully evaluated. A future HRP-funded study using head-down tilt bed rest is planned to evaluate the efficacy of the OFW to mitigate aerobic and muscular deconditioning. The OFW, made by KBR, is a specialized device that poses high costs for purchase and maintenance. The aim of the study is to determine if a commercially available alternative could be used as a backup for the OFW during the bed rest study or as an alternative in other studies. This study seeks to compare the loading profile and mechanics of a commercial flywheel device (kBox Pro) with the three resistance settings of the OFW using a controlled, instrumented setup to validate its acceptability as a backup. METHODS: An experimental setup was designed to simulate human use of the OFW. Flywheel devices can have varied actuated inertial mass and strap length. The inertial mass refers to the flywheel itself or the object that spins as the result of the movement of the strap. The OFW has three gears actuated with a lever, with the low gear used for aerobic rowing and the medium and high gears used for resistance exercises. These gears correspond to increasing flywheel inertia, which corresponds to a certain number and sizes of inertial plates on a commercial flywheel. The kBox Pro has varied sizes of inertial discs that are installed to the external shaft of the device and can be configured to roughly match the inertia seen in the OFW per gear setting. The strap length can be adjusted to allow for different ranges of motion. The experimental setup allows for the simulation of rowing, harness squats, and deadlift high pulls with corresponding exercise strap lengths. All three OFW gears are to be tested, as well as multiple combinations of kBox discs. The setup was created using a system of pulleys and cables to minimize friction loss. The system is actuated through the dropping of a connected mass which, through the pulley system, pulls the strap of the exercise device upwards as if a human was exercising. A string potentiometer and tensile force transducer are used to measure strap displacement and strap force, respectively. The masses dropped are exercise chains that simulate the decrease in force observed throughout a typical exercise. As the chains are lowered to the ground, they begin to spool and therefore are no longer subjecting the exercise device’s strap to their load. This setup was designed to provide realistic loads and protect the OFW from damage, an important precaution because it’s the only available unit for research and ground operations. Data is to be collected across simulated exercises and with different strap lengths, with the same conditions collected on both the OFW and the kBox Pro. RESULTS: Data collection is ongoing for the kBox and the Orion Flywheel. CONCLUSIONS: Study results will inform if the OFW and a kBox Pro device can be deemed mechanically similar. Depending on the results, additional data collection may be required to assess the user experience between the devices. A key result of this study is a mechanical characterization of the OFW device, demonstrating the load and force profile using a repeatable test method. This data will guide next steps on potential kBox Pro modifications needed to produce a comparable exercise experience to the OFW.

Exercise↗