The Digital Astronaut Project (DAP) Applying computational models and

simulations to inform life science research

Lealem Mulugeta DAP Project Scientist

mulugeta@dsls.usra.edu

lealem.mulugeta@nasa.gov

USRA DSLS Brown Bag Lunch Seminar - April 19th, 2012

Acknowledgments

Christian Otto, MD VIIP Project Scientist

Dr. Jean Sibonga, PhD HACD Bone Discipline Lead

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Marlei Walton, PhD IMM Project Scientist

Overview

• Goals of the Digital Astronaut Project

• Processes DAP follows to accomplish its goals

• The modeling and simulation tools currently under development

• Video demonstration of the ARED and exercise modules

• Our recent achievements

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Introduction

• Mars and NEO missions will expose astronaut to extended durations of reduced-gravity, isolation and higher radiation

• These new operation conditions pose health risks that are not well understood and perhaps unanticipated

• Advanced computational simulation environments can beneficially augment research to predict, assess and mitigate potential hazards to astronaut health

• The Digital Astronaut Project (DAP) strives to achieve this goal

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DAP’s Model Development and Implementation Process

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How Models Can be Applied to Enhance Life Science Research

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Current Focus Areas

1. Exercise countermeasures modeling and simulation – Advanced Resistive Exercise Device (ARED) – Biomechanics of exercise – Bone adaptation – Muscle adaptation – Advanced Exercise Concept Devices

2. Risk of bone fracture – Bone adaptation – Biomechanics of post-flight activities for bone load predictions

3. Visual Impairment and Intracranial Pressure (VIIP) – Preliminary stages

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ARED Exercise Modeling

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ARED Exercise Modeling Kick-off Plan

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Exercise Countermeasures Modeling

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• Human exercise simulation in micro-gravity – Squat – Single-leg squat – Dead-lift – Heel-raise

• Prediction of: – Muscle forces – Muscle adaptation – Ground reaction forces – Joint torque – Mechanical load bones/joints – Bone adaptation

• Influence of: – Anthropometric variation – Stance variation – Range of motion

Exercise Countermeasures Modeling

Targeted HRP risk knowledge gaps: B15: (a) What exercise protocols are necessary to maintain skeletal health? And (b) Can exercise hardware be designed to provide these? M7: Can the current in-flight performance be maintained with reduced exercise

volume? M8: What is the minimum exercise regimen needed to maintain fitness levels

for tasks? M9: What is the minimum set of exercise hardware needed to maintain those

(M8) fitness levels? M24: What is the time course of changes in muscle protein turnover, muscle

mass, and function during long-term spaceflight?

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ARED Hardware Model

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• High fidelity dynamics model of ARED/VIS developed in MSC Adams™

– Mass and inertial properties

– Friction forces

– Gas laws

• Currently allows for simulation of bar exercises only

Modeler: Brad Humphreys

ARED Hardware Model

13 Modeler: Brad Humphreys NOT VALIDATED

Force generated at the bar in 1-g

14 NOT VALIDATED Modeler: Brad Humphreys

Force generated at the bar in 0-g

15 Modeler: Brad Humphreys NOT VALIDATED

ARED Exercise Modeling Kick-off Plan

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Developed in parallel with ARED/VIS model

ARED Exercise Models

• Developed with LifeMOD™ using motion capture data acquired on the ARED ground unit at JSC

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Dead lift Normal Squat Single-leg squat M

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Modelers: Nate Newby and Erin Caldwell

Integrated ARED-Dead Lift Exercise Model

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NOT VALIDATED

Modelers: Nate Newby and Erin Caldwell

Integrated ARED-Dead Lift Exercise Model

19 Modelers: Nate Newby and Erin Caldwell

NOT VALIDATED

Integrated ARED-Squat Exercise Model

20 Modeler: Bill Thompson

NOT VALIDATED

Integrated ARED-Exercise Squat Model

21 Modeler: Bill Thompson

NOT VALIDATED

Integrated ARED-Exercise Squat Model

22 Modeler: Bill Thompson

NOT VALIDATED

ARED Exercise Modeling and Implementation Process

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Muscle Adaptation Model

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• Conceptual phase

• Enhance the fidelity of muscle representation in the LifeMOD biomechanics models in terms of space flight changes

• Gain insight on muscle adaptation factors: – Neuromuscular drive and activation

– Muscle atrophy and fiber morphology

– Blood flow and intramuscular pressure

– Metabolic processes

– Fatigue

Modeler: Beth Lewandowski, PhD

Bone Adaptation Model

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• Predicted muscle force from biomechanics models is an input to the bone adaptation model

• Bone adaptation model factors :

– Cortical bone tissue rate of change

– Bone fluid calcium rate of change

– Biochemical equations

– Mechanical stimulus

– Cellular dynamics

Modeler: Jim Pennline, PhD

Risk of Bone Fracture

Targeted HRP risk knowledge gaps: B15: (a) What exercise protocols are necessary to maintain skeletal

health? B1: (a) Is there an increased lifetime risk of fragility

fractures/osteoporosis in astronauts? (b) Is bone strength completely recovered post-flight, and does

BMD reflect it? (c) What are the risk factors for poor recovery of BMD/bone

strength B30: What are the loads applied to bone in-flight and during EVA

activities and do they increase fracture risk in light of expected bone loss?

26 Modeler: Jim Pennline, PhD

Risk of Bone Fracture

• Implement biomechanical modules to predict the forces experienced at specific bone sites during various activities (not exercise)

• Enhance bone adaptation module to determine changes in the macro- and microstructure of bone during long-duration spaceflight and implications on long-term bone health risks

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(Hewett et al., 2008)

Modeler: Jim Pennline, PhD

Advanced Exercise Devices Modeling

• Develop device models for advanced exercise (AEC) devices:

– Multi-mode Exercise Device (M-MED) – NSBRI / UC Irvine

– Gas spring device (ZIN)

– Streamline ergometer (SBIR)

28 Modeler: Brad Humphreys

Advanced Exercise Devices Modeling

• Objectives: 1. Gain insight into the efficacy of AEC devices for exercise

countermeasures

2. Provide timely input for design, development, and refinement of AEC devices

3. Help reduce the time and cost to develop the exercise devices

4. Help reduce the time and cost to clinically test new exercise devices

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Visual Impairment and Intracranial Pressure (VIIP)

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Changes in visual acuity

Intra-ocular Pressure

(Adapted from Google Body – http://bodybrowser.googlelabs.com)

Papilledema

Intracranial Hemodynamics

Intracranial Pressure

Cerebrospinal Fluid Flow

Intracranial Compliance Primary focus:

• biomechanical responses to the of the intracranial and ocular structure while microgravity environment that may affect visual acuity

Model types under consideration: • Lumped parameter models of the

intracranial and spinal compartments • Finite element model of the eye • Computational fluid dynamics of the

intracranial and spinal space • High fidelity tissue models to capture

nonlinear/viscoelastic properties

Current Status for VIIP Modeling

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VIIP Targeted Gaps

• VIIP6: How do changes in vascular compliance/ pressures influence intraocular pressure or intracranial pressure?

• Gap VIIP2: Does exposure to microgravity cause changes in visual acuity, intraocular pressure and/or intracranial pressure? Are the effects related to mission duration?

• Gap VIIP4: Are changes in visual acuity related to changes in: 1) deformation of the optic nerve head; 2) chronic choroidal engorgement; 3) elevated intraocular pressure; and/or 4) intracranial pressure?

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Recent Successes

ARED Model used for Flywheel Preventative Maintenance

• The ARED flywheels were disengaged due to ground evidence that suggested the flywheel set screws may back out of their engagement to cause damage to the ARED

• Substantiation was requested from the ISS Program Office on whether or not crew time should be allocated to re-torque the set-screws as a short term fix to buy enough time to investigate a long-term fix

• The exercise lab at JSC leveraged the Beta ARED hardware model to partially substantiate the benefit of having the inertial wheels engaged during exercise

34 Analysts: Nate Newby, Erin Caldwell and Brad Humphreys

ARED Model used for Flywheel Preventative Maintenance

35 Analysts: Nate Newby, Erin Caldwell and Brad Humphreys

ARED Model used for Exercise Envelope Analysis

36 Analysts: Nate Newby and Erin Caldwell

• The ISS Program Office requested an analysis to assess if the ISS operational envelope for ARED exercise to assess if the envelope is being exceeded during exercise due to excess stowage in the exercise area

• DAP modelers used the dead lift/ARED model within the currently assigned ISS operational envelope for ARED exercise to assess if the envelope is being exceeded during exercise

• DAP modelers developed a model of a 95th % male performing a bench press on the ARED to perform the same analysis

• The results were shared with the ISS Program Office to determine the necessary operational envelope

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ARED Model used for Exercise Envelope Analysis

Analysts: Nate Newby and Erin Caldwell

Contributions to the Field for V&V of Biomedical Models and Simulations

• The FDA is leveraging a lot of the methodologies DAP and IMM have laid out for verification, validation and credibility assessment of M&S

• Collaboration talks are currently underway with FDA

• The NIH Multiscale Modeling Working group meeting in October 2012 is going to have a large emphasis on V&V and credibility assent

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Synapses

• DAP has established a systematic process to closely work with researchers to leverage computational models inform HRP risk knowledge gaps

• Current areas of focus are exercise countermeasures, risk of bone fracture and VIIP

• Substantial strides have been made in the past year in biomechanical and exercise device modeling

• Making notable contributions to the field in verification and validation, and credibility assessment of computational models

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“All models are wrong, but some are useful.” - George E. P. Box

The DAP Team

Beth Lewandowski, PhD – Muscle Model

Bill Thompson, MS – Squat Integration

Brad Humphreys – Exercise Device Modeling

Chris Sheehan – Exercise Device Modeling Task Lead

Chris Werner – ARED V&V

DeVon Griffin, PhD - Project Manager

Emily Nelson, PhD – VIIP M&S

Erin Caldwell , MS - Biomechanics Modeling and Dead Lift Integration

Jennifer Stein – Exercise Device V&V Processes

Jim Pennline, PhD – Bone Modeling Lead

Jerry Myers, PhD – M&S Advisor

Lealem Mulugeta, MS - Project Scientist

Nate Newby, MS – Biomechanics Modeling and Dead Lift integration

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Questions?

DAP Mission Statement

The DAP implements well-vetted computational models to predict and assess spaceflight health and performance risks, and enhance countermeasure development. The DAP aims to accomplish these goals by:

1. Partnering with subject matter experts to address Human Research Program (HRP) knowledge gaps and countermeasure development decisions

2. Modeling, simulating, and analyzing the physiologic responses to exposure to reduced gravity and analog environments

3. Providing timely input to mission architecture and operations decisions in areas where clinical data are lacking

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NASA Standard 7009

A comprehensive set of requirements and processes for developing and applying models and simulations, while ensuring appropriate verification, validation and credibility of the M&S results

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NASA-STD-7009 Background

• NASA M&S that impact on the crew or mission will be required to follow NASA-STD-7009, including biological models

• It was initially developed for engineering systems

• DAP and Integrated Medical Model (IMM) have adapted NASA-STD-7009 for biomedical models for clinical and research applications

• Given the highly comprehensive nature of the standard, DAP and IMM are working to establish a systematic process to apply it to vet M&S

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