Signature Redacted a Uthor

Evaluating Human-EVA Suit Injury Using Wearable Sensors MASS ACUS0 ILNSTITUTE )F TECHNOLOGY by JUN 28 2016 Ensign Sabrina Reyes, U.S. Navy IBRARIES B.S., Aerospace Engineering United States Naval Academy (2014) ARCHIVES Submitted to the Department of Aeronautics and Astronautics in partial fulfillment of the requirements for the degree of Master of Science in Aeronautics and Astronautics at the MASSACHUSETTS INSTITUTE OF TECHNOLOGY June 2016

Signature redacted A uthor ...... ;...... Department of Aeronauticand Astronautics

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am= Signature redacted-- Certified by...... Jelfrey A. Hoffman, Ph.D. Professor of theractice, Aeronautics and Astronautics Siqnature redacted A ccepted by ...... I...... PauloI C Lozno7n PhDT Associate Professor of Aeronautics and Astronautics Chair, Graduate Program Committee 2 Evaluating Human-EVA Suit Injury Using Wearable Sensors by Ensign Sabrina Reyes, U.S. Navy

Submitted to the Department of Aeronautics and Astronautics on May 19, 2016, in partial fulfillment of the requirements for the degree of Master of Science in Aeronautics and Astronautics

Abstract

All the current flown spacesuits are gas pressurized and require astronauts to exert a substantial amount of energy in order to move the suit into a desired position. The pressurization of the suit therefore limits human mobility, causes discomfort, and leads to a variety of contact and strain injuries. While suit-related injuries have been observed for many years and some basic countermeasures have been implemented, there is still a lack of understanding of how humans move within the spacesuit. The rise of wearable technologies is changing the paradigm of biomechanics and allowing a continuous monitoring of motion performance in fields like athletics or medical re- habilitation. Similarly, pressure sensors allow a sensing capability to better locate the areas and magnitudes of contact between the human and their interface and reduce the risk of injuries. Coupled together these sensors allow a better understanding of the complex interactions between the astronaut and his suit, enhance astronauts performance through a real time monitoring and reducing the risk of injury. The first set of objectives of this research are: to gain a greater understanding of this human-spacesuit interaction and potential for injury by analyzing the suit-induced pressures against the body, to determine the validity of the particular sensors used with suggested alternatives, and to extend the wearable technology application to other relatable fields such as soldier armor and protective gear. An experiment was conducted in conjunction with David Clark Incorporated Company on the Launch Entry Development spacesuit analyzing the human-spacesuit system behavior for isolated and functional upper body movement tasks: elbow flexion/extension, shoulder flexion/extension, shoulder abduction/adduction and cross body reach, which is a complex succession of critical motions for astronaut and pilot task. The contact pressure between the person and the spacesuit was measured by three low-pressure sensors (the Polipo) over the arm, and one high-pressure sensor located on the shoulder (Novel). The same sensors were used in a separate experiment conducted in conjunction with Protect the Force Company on several different United States Marine Corps (USMC) protective gear configurations, which analyzed the human-gear interactions for: shoulder flexion/extension, horizontal shoulder abduction/adduction, vertical shoulder abduction/adduction, and the cross body reach. Findings suggest

3 that as suit pressurization increases, contact pressure across the top of the shoulder increases for all motion types. While it proved to be a perfectly acceptable method for gathering shoulder data, improvements can be made on the particular sensors used and the type of data collected and analyzed. In the future, human-suit interface data can be utilized to influence future gas-pressurized spacesuit design. Addition- ally, this thesis briefly explores the incompatibilities between Russian and U.S. EVA capabilities in order to make a case for equipment standardization.

Thesis Supervisor: Jeffrey A. Hoffman, Ph.D. Title: Professor of the Practice, Aeronautics and Astronautics

4 Acknowledgments

First and foremost, I would like to thank the wonderful advisors I had at MIT, without whom this thesis could have never happened. To Dr. Jeff Hoffman, thank you for all your honest guidance during the thesis process and regarding my aspirations to become an astronaut. To Dr. Dava Newman, thank you for introducing me to the world of human spaceflight and reigniting my passion for aerospace. My MIT experience would not have been the same without such a wonderful person in my life to give me incredible opportunities like meeting Buzz Aldrin, skiing in Montana for a conference, or working with spacesuits and other fantastic people for my research. Thank you both for all the opportunities and the unwavering support.

To the EVA team, Pierre, Alexandra, and Allie, I cannot thank you enough for all your help on this thesis. It seriously would not have happened without you. Thanks for all the fun meetings, for being some of my first friends at MIT, and for being incredibly patient and helpful with all my questions even after you had moved on to bigger and better things!

To Tony, John, and Grant, thank you guys for being my Navy partners in crime. You guys understand and tolerate my awful mood swings, humor, and personality probably more than anybody else, and for that I am so grateful. I am happy I had you all to provide advice and/or sounding boards for weird Navy situations like P-codes, disappearing without leave, etc. Tony and Grant, I guess I'm sort of happy we will all be in the same pipeline so I can see your ugly faces even after we leave MIT, and John, I am going to miss you so much but I know that you'll kick butt in flight school!

To Hannah, thanks for being the sweetest roommate, officemate, classmate, etc. Our weird cookie binges, burger quests, lunch runs, and wonderful conversations kept me from insanity (seriously). Thank you for being such a wonderful and patient friend.

To Conor, Richard, Lynn, Forrest, Eddie, and the rest of the MVLers, you guys are seriously the most amazing people ever! I am highly convinced that the Man Vehicle Lab is the coolest, funnest lab at MIT, plus we produce some darn good

5 research. Thanks for letting me waste all your time because I don't feel like doing any of my own work. Thanks for lab lunches, lab dog-sitting adventures, IEEE skiing, HST formal shenanigans, Captain America movie nights, and all the other incredible memories that I will cherish forever. I will miss you all so much, please come visit me wherever I am in the Navy!

To the close friendships: Macauley, Anne, Parker, Patricia, Mark, and Emily, thank you guys for random dinners, drink nights, and for distracting each other from research and life. I love you guys to the moon and back. A special thanks to Liz Zotos, Barb DeLaBarre, Ed Ballo, and Beth Marois for providing advice, help, and friendship throughout my stay at MIT. Finally, I would like to thank my family for their incredible prayers, love, support, and encouragement. To Elizabeth, thank you for adopting my family into your own, because you have become such an important part of our family. Thank you for all your spot-on advice in all areas of life, because no one else seems to understand my way of thinking quite like you do. I love all of you very much and would not have gotten to where I am without you.

6 Contents

1 Introduction 13

2 Literature Review 16 2.1 Extravehicular Activity ...... 16 2.2 EVA Training and Injury ...... 19 2.3 Previous Work on Development of a Quantitative Understanding of Human-Spacesuit Interaction ...... 23

3 Sensor Systems and Experimental Design 25 3.1 Sensor System s ...... 25 3.1.1 Low Pressure Sensing System, the "Polipo" ...... 25 3.1.2 Novel High-Pressure Shoulder Sensor ...... 28 3.1.3 APDM Inertial Measurment Units ...... 29 3.2 Spacesuit Testing Experimental Design ...... 30 3.3 Marine Protective Gear Experimental Design ...... 32

4 Novel System Results and Discussion 36 4.1 David Clark Experiment ...... 36 4.1.1 Pressure Distributions ...... 37 4.1.2 Pressure Profiles ...... 41 4.1.3 Statistical Analysis ...... 47 4.2 Protect the Force Armor Gear Prototype Experiments . .... 53 4.3 Conclusions and Future Work ...... 55

7 5 International EVA Capabilities 58 5.1 A Case for EVA Standardization ...... 58

6 Conclusions 66

A Human-Suit Interface Pressure Evaluation 68

8 List of Figures

2-1 Extravehicular Mobility Unit and Exploded View Diagram. (Image Sources: NASA, Hamilton Sustrand) ...... 17

2-2 Pivoted HUT on left and Planar HUT on right. Note the different angles of the scye bearings in the two HUTs. (Image Source: NASA) 18

2-3 David Clark Launch and Entry Development Suit ...... 18

2-4 Astronaut training in the NBL in an inverted position (Image Source: N A SA ) ...... 20

3-1 Printed carbon-grease sensor with electrode extensions. (Image Source: W yss at Harvard, 2014) ...... 27

3-2 AMOHR two-stranded conductive tape used for second Polipo iteration. 28

3-3 Experimental Sensor Systems: A) Low-pressure Polipo sensors, B) High-pressure Novel shoulder sensor, C) APDM Opal inertial measurement unit. (Image Source: Anderson, 2014) ...... 29

3-4 Placement of the in-suit sensor systems. (Image Source: Anderson, 2014) 30

3-5 Descriptions of the four upper body motions performed during the spacesuit experiment: three isolated joint motions (elbow flexion/extension, shoulder flexion/extension, shoulder abduction/adduction), and one functional task (cross body reach). (Image Source: Anderson, 2014, .31 Hilbert et al. 2014) ......

9 3-6 Experimental Design Test Protocol: Each movement group consists of a counterbalanced ordering of the motions. The motions studied were: three isolated joint motions (elbow flexion/extension, shoulder flexion/extension, and shoulder abduction/adduction) and a functional task motion (cross body reach). In each movement group, the specific motion was repeated 5 times for a total of 15 repetitions per motion. 32

3-7 Different USMC protection gear configurations used during testing . 33

3-8 Horizontal shoulder abduction/adduction. Beginning with their arms extended at shoulder height, shoulder width apart, the subject bends their arms at the shoulder in the transverse plane. The subject moves through his or her maximum range of motion. The subject returns to the initial start position then releases to the relaxed position...... 34

3-9 Protective Gear Experimental Design Test Protocol. Each movement group consists of a counterbalanced ordering of the motions. The motions were: three isolated joint motions (shoulder flexion/extension, shoulder abduction/adduction vertical, shoulder abduction/adduction horizontal) and a functional task motion (cross body reach). In each movement group, the specific motion was repeated 5 times for a total of 15 repetitions per motion...... 35

4-1 Orientation of the Novel Sensor. The orientation corresponds to the information in each pressure distribution figure. Coloring is for orientation and is not related to pressure scales. (Image Source: Hilbert 20 15) ...... 3 7

4-2 Contact pressure distributions for each motion at each pressurized condition for Subject 1...... 38

4-3 Contact pressure distributions for each motion at each pressurized condition for Subject 2...... 40

4-4 Contact pressure profiles for all motions in the 2.5-psi pressurized condition for Subject 1...... 42

10 4-5 Contact pressure profiles for all motions in the 3.5-psi pressurized condition for Subject 1...... 43 4-6 Contact pressure profiles for all motions in the 2.5-psi pressurized condition for Subject 2...... 45 4-7 Contact pressure profiles for all motions in the 3.5-psi pressurized condition for Subject 2...... 46 4-8 Effects of pressurization on mean contact pressure for Subject 1. . .. 49 4-9 Effects of pressurization on mean contact pressure for Subject 2. . .. 49 4-10 Effects of motion type on mean contact pressure for Subject 1. .... 50 4-11 Effects of motion type on mean contact pressure for Subject 2. . ... 50 4-12 Effect of subject on mean contact pressure for intermediate pressuriza- tio n ...... 5 1 4-13 Effect of subject on mean contact pressure for full pressurization. . . 51 4-14 Pressure distributions of all motions for different USMC armor configurations...... 54 4-15 Pressure distributions for rifle carry motion for Configuration 1 (on left) and Configuration 4 (on right)...... 55 4-16 Novel Single S2012 Sensor with 2 cm diameter (Image Source: novel.de) 57

5-1 Rear entry opening for Russian Orlan-M spacsuit. (Image Source: NASA)...... 59 5-2 The U.S. EMU and Russian Orlan-M spacesuit shown side by side. (Image Source: NASA) ...... 63

11 List of Tables

3.1 Anthropometrics from typical Marine compared to anthropometrics of subject used ...... 34

12 Chapter 1

Introduction

Human spaceflight programs are facing new challenges rising from the evolution of the exploration agenda, the need for Commercial Crew and the new entry on the market of space tourism. These different activities bring new challenges: planetary exploration missions will require intensive extravehicular activities (EVA), space tourism will require new, cheap and user friendly space systems, specifically, pressure suits. Spacesuits need to adapt to this new era of space exploration and democratization of space. Spacesuits are technical marvels: their main functions are providing oxygen, pressure, food, water, waste removal, communication, thermal control, mobility, radiation protection, direct sunlight protection, and micrometeorite protection. The human body cannot survive in the vacuum of space because all air the air would rush out of the lungs, blood vessels would rupture and the blood would eventually boil. However, lower total pressure than atmospheric pressure can keep the astronaut alive and be an adequate environment to work in as long as the partial pressure of oxygen is maintained. One of the most important functions of a spacesuit is to provide mobility: "the advantage of a human in space over a robot is the ability to see, touch, and adapt instantly to real-time conditions. This is an advantage only if the astronauts are able to effectively use their hands, arms, legs, eyes, and brains." Spacesuit joints are one of the most critical parts of the design of the spacesuit since they determine its mobility. The common gas-pressurized spacesuit designs tend to keep a constant or near constant volume in the joints. Spacesuits have evolved since

13 the initial designs but many issues remain. Over time, these gas-pressurized suits cause fatigue, increase metabolic expenditure, and eventually may lead to injuries in astronauts. Gas-pressurized suits cause astronauts to experience discomfort, hot spots, skin irritation, abrasions, contusions, and over time injuries requiring medical attention [21]. Injuries occur primarily where the person impacts and rubs against the suit to change its position. Although most injuries have been minor and did not affect mission success, injury incidence during EVA is much higher than injury that occurs elsewhere on-orbit. While the most common injuries occur in the hands, feet, and shoulders, shoulder injuries (including rotator cuff tears that require surgery) are some of the most serious and debilitating injuries astronauts face as a result of working in the suit. Countermeasures have been developed to mitigate suit-related injuries, but still relatively little is known of how humans move within the spacesuit. In addition to the technical challenges, human spaceflight programs face implementa- tion challenges in terms of cost, schedule, and regulatory barriers. In order to provide a holistic view of the problems presented in human spaceflight, we must look at both the technological and policy aspects. For the purpose of this thesis, we will look specifically at international cooperation for EVA capabilities. The objectives of this research are to:

1. gain a greater understanding of the human-spacesuit interaction specifically at the shoulder interface in order to determine potential for injury by analyzing the suit-induced pressures against the body using a network of pressure-sensing and kinematics systems,

2. determine the validity of the particular sensors used in an effort to understand this interaction and suggest alternatives if the current sensors are found to be sub-optimal,

3. extend the wearable technology application to other relatable fields such as soldier armor and protective gear,

4. and finally, compare and contrast EVA capabilities and incompatibilities be-

14 tween the U.S. and Russia in order to build a case for equipment standardization.

Chapter 2 provides relevant literature on EVA training, astronaut injury, shoulder injury, and previous studies and countermeasures addressing these issues. Chapter 3 sets forth the pressure sensing systems and experimental design that were used in order to conduct experiments with the David Clark Company for spacesuits and Protect the Force Company for United States Marine Corps (USMC) protective gear. Chapter 4 presents the results and discussion of the shoulder pressure data that was gathered during the human subjects experiment for the spacesuits and protective gear. A combination of graphical and statistical analyses were performed to examine the data, and results regarding pressure distributions, pressure profiles, and effect of pressure magnitudes are presented. Chapter 5 presents a general comparison of EVA capabilities between the U.S. and Russia in order to build a case for equipment standardization. Finally, Chapter 6 provides a summary and conclusion of all the results of the thesis. Recommendations for future work are also provided.

15 Chapter 2

Literature Review

The following is a review of literature on space suit design and EVA working envi- ronments.

2.1 Extravehicular Activity

Extravehicular activity (EVA) is critical to human spaceflight. Since the Soviet cosmonaut Alexey Leonov performed the first EVA on March 18, 1965, to the moment American astronaut Neil Armstrong stepped foot on the moon on July 20, 1969, the human race has been eager to further human space exploration for national pride, the sake of curiosity and possibly survival, as well as secondary rationales that include economic development, new technologies/innovation, education and inspiration, and the development of peaceful international relations. Astronauts and cosmonauts have performed nearly 300 EVAs as of 2009 [6]. Only 14 of those EVAs have been conducted on the lunar surface in one-sixth gravity. However, despite the large number of EVA expeditions over the course of forty years, relatively little is known about the interactions between the human and the EVA suit that they utilize. NASA has already publicly expressed its intentions for human missions to Mars, but before these missions can be realized, it is imperative that we can thoroughly characterize space suit performance. This research addresses how we are currently developing a method to evaluate space suit design and understand injury.

16 Figure 2-1: Extravehicular Mobility Unit and Exploded View Diagram. (Image Sources: NASA. Hamilton Sustrand)

The fundamental challenges faced by U.S. space suit designers include providing pressure. oxygen, waste removal. coimunication. food, water, therimal control, 111o- bility. radiation protection, and a safe working environment [20]. U.S. astronauts currently fly and train in the extravehicular mobility unit (EMU). The EMU consists of the space suit assembly (SSA), protective and comfort pieces. and the life support system. The space suit assembly is a 14-layer suit weighing 64 kg (140 lb) that is pressurized to 29.6 kPa (4.3 psi) [12]. The additional portable life support systeim

(PLSS) backpack increases the total suit weight to 115 kg (254 ib). Components of the SSA are available in multiple standard sizes to allow astronauts to mix pieces and provide a better fit. Although suit fit is optimized for each astronaut with the standard sizes available, not all astroamtsanthropometries cai be comfortably ac- conmnmodated. Currently, the only component of the SSA that can be custom fit for an astronatutspecific anthropometric measurements are the gloves. The hard upper torso (HUT), a fiberglass shell that connects to the arm, helnet. and lower torso asseniblies. coies in two designs: the pivoted and planar HUT. There are only three sizes currently available to astronauts: nedimun, large, and extra large [9]. Both are available for use during training. bitt only the planar HUT is currently used iII spaceflight. The pivoted HUT is no longer used on orbit simnce a rupture in the bellows would be a catastrophic failure of suit integrity [21]. The planar HUT has planar

17 seve bearings in fixed planes at the armli openings, vhereas the 1)ivoted HUT has a

shoulder gimbal with a two-point pivot to aid the range of motion of the shoulder

joilit [19].

Figure 2-2: Pivoted HUT on left, and Planar HUT on right. Note the different angles of tlie seve bearings in the two HUTs. (Image Source: NASA)

There are several prototylpe suits that have been developed for planetary aild deep

space exploration. Future nissions to \Jars will require spacesuits that have high

mobility and dexterity. and currentlv the ENJU does not satisfy those requirements.

The E\IU limits mobility and requires a substantial aniount of eiiergy iii order to

move the suit into a desired position. Mechanical counter-pressure suits such as

the BioSiit are currently bei]ig developed to address issues of mobility and energy

consmiiption. but gas-pressurized suits are officially NASA's state of the art capability

[13]. Of the gas pressurized space suits being developed to address different sceliarlo

requirements. the one of particular focus in this thesis is the David Clark Launch and

Entry Development Suit. which is currently being developed to address launch and

entry requirements. No other information is currently publicly available for this suit.

Figure 2-3: David Clark Launch and Entry Development Suit

18 2.2 EVA Training and Injury

Extravehicular activity training currently focuses on preparing only for microgravity as astronauts are only sent to the International Space Station (ISS). The Neutral Buoyancy Laboratory (NBL), a 23.5 million liter pool at the NASA Johnson Space Center, is the primary facility that conducts training for the weightless microgravity environment; it contains a full-size mock-up of the International Space Station. Every astronaut spends an average of 11.6 hours of training in the NBL per hour of planned in-flight EVA and between 200-400 hours in training over the course of their career [19, 3]. The specific number of hours per astronaut depends on their mission's specific sorties, and the technical details of the EVA. NASA defined an optimum work envelope for tasks performed on the Hubble Space Telescope and ISS, however, repeatedly performing tasks outside the envelope can have a significant impact on the astronaut [9]. As mentioned previously, the current EMU is pressurized at 4.3 psi, which makes it difficult to move within the spacesuit. Maintaining different postures to complete certain tasks within the suit causes increased metabolic expenditure and fatigue. A combination of the time spent training for each EVA and the EVA suit mechanics is cited as a contributing factor for the astronaut injury incidence rate [19, 18]. Gravity acting on the astronaut inside the neutrally buoyant space suit causes shifting within the suit in the NBL not seen on orbit [3]. Another important aspect in NBL training is that crews are subjected to inversion for short durations, where the body is oriented in a head down position greater than 45 degrees as seen in Figure 2-4 [9]. Inversion is defined as a position in which the body is at a head-down angle of more than 45 degrees; this position loads the shoulders with the astronaut's full body weight during training for a few minutes at a time. This commonly leads to injury and discomfort. The lack of restraint within the suit has resulted in a shoulder bruising during training for nearly every case. Additionally, insufficient recovery time between NBL training runs prevents astronauts from physically recovering and may exacerbate developing injuries [9]. Although no EVA-related injury has prevented successful completion of a mission objective, there have been several instances when

19 I

the EVA was nearly terminated(ldue to suit discomfort [18 3].

loll A

Figure 2-4: Astronaut training in the NBL in an inverted position (hage Source: NASA)

Wieii sunt discomfort becomes suit-related injury. it becomes a major cause for concern. Anecdotal reports from astroiiauts have mentioned the occurreice of in-flight inisculoskeletal injuries since the begiining of NASA's human spaceflight progran

[18]. In December 2002. Williams and Johnson at NASA created the shoulder injury tiger team to evaluate the possible relationship between shoulder injuries and EVA training in the NBL. The Tiger Team confirmed that NBL EVA training was directly liked to a number of shoulder injuries [9]. By administering aii EMU Shoulder

Injury Survey to 42 astronauts aund astronaut candidates. they were able to find the primary factors coitributing to both major. defined as significant shoulder injuries requiring medical intervention or surgical correction. andi inor. defined as self-limited conditions requiring iiiinimal medical intervention, injuries. They foun11d that factors contributing to both major andi minor injuries are: limitations to niormal shoulder mobility iin the E\IU Planar HUT. performing tasks ini inverted body positions. using heavy tools. and frequent NBL runs. Three astronauts had surgery for EVA training- related shoulder ilIjuries. only one of which had sustained a shoulder injury previously. Additionally. the onset of a moderate dull ache over the top of the shoulder or within

20 the shoulder joint during or within 24 hours of an NBL run strongly suggests a causal relationship, and repeated episodes of pain during training suggest overuse that could lead to surgical repair [21, 9]. The findings and recommendations of the tiger team are wide-ranging due to the multi-factorial nature of EVA training injuries [21]. Based on their findings, Williams and Johnson made key recommendations to mitigate injury, but these recommendations were only based on subjective findings [9].

From 2002 to 2004, Strauss et al. quantified and characterized signs, symptoms, and injuries resulting from extravehicular activity spacesuit training at NASA's Neu- tral Buoyancy Laboratory immersion facility. By identifying the frequency and incidence of symptoms by location and mechanism, they determined the most frequent injuries occurred in the hands and shoulders, with shoulders being rated the most severe injuries. Of 770 spacesuit symptom questionnaires, 24.6% of tests yielded symptoms, with 47.6% of symptoms in the hands, 20.7% in the shoulders, and 11.4% in the feet. The only shoulder countermeasures available are supplementary comfort pads, an EMU shoulder harness to prevent shoulder contact complaints and an optimal suit fit to include unique fit adjustments [19].

In 2007, Scheuring published his results from the Apollo Medical Operations Project. The Apollo Medical Operations Project collected feedback from 14 of the 22 surviving Apollo astronauts. Recommendations centered on improving the function- ality of the suit as well as improving human factors and safety features. Of the EVA Suit recommendations listed, the recommendations related to mitigating astronaut injury were to improve glove flexibility, dexterity, fit, and to increase general mobility by a factor of four [17]. The astronauts surveyed also recommended increasing ambulatory and functional capability through increased suit flexibility, decreased suit mass, lower center of gravity, and reduced internal pressure [17]. In 2009, Scheuring's following study cataloged and analyzed all in-flight musculoskeletal injuries occurring throughout the U.S. space program beginning with the Mercury program through the conclusion of ISS Expedition 13 in September 2006 [18]. A total of 219 in-flight musculoskeletal injuries were identified, 198 occurring in men and 21 in women. The incidence of in-flight musculoskeletal injuries was found to be 0.021 injuries per day

21 for male crewmembers and 0.015 injuries per day for female crewmembers. While hand injuries represented the most common location of injuries, shoulder and back injuries are also notable in the data of injuries separated by anatomical location. The most common types of injury were abrasions, contusions, strains, and lacerations. Of note, most astronauts also remarked that their wounds healed more slowly while on orbit. Hand injuries were most common among EVA crewmembers, often due to the increased force needed to move pressurized, stiff gloves. These hand injuries mani- fested themselves as small blisters and pain across their metacarpophalangeal (MCP) joints. Injuries occurred most frequently during crew activity and within the EVA suit. Engineers can use in-flight injury data to further refine the EVA suit and vehicle components [18]. In 2010, Opperman developed a musculoskeletal modeling tool to compare various spacesuit hard upper torso designs and focus on optimizing comfort and range of the motion of the shoulder joint within the suit. He also performed a statistical analysis to investigate the correlations between the anthropometrics of the hand and susceptibility to injury using a database of 192 male crew members' injury records. He found hand circumference and width of the MCP joint to be significantly associated with injuries. Experimental testing was also conducted to characterize skin blood flow and contact pressure inside the glove. The tests show that finger skin blood flow is significantly altered by contact force/pressure, and that occlusion is more sensitive when it is applied to the finger pad than the finger tip [16]. Countermeasures to address shoulder injury in the NBL and orbit include different types of simple padding and harnesses for the HUT. The most commonly used pads are primarily for protection from the scye bearing and HUT shell, while the rarely used shoulder harness acts like a pair of suspenders inside the HUT that have a pad assembly at the shoulders to absorb contact loads in the suit [21]. Countermeasures can still be improved by expanding our understanding of human-spacesuit interaction.

22 2.3 Previous Work on Development of a Quanti- tative Understanding of Human-Spacesuit In- teraction

Over the past few years, a team of researchers at the Massachusetts Institute of Tech- nology (MIT) along with collaborators at Trotti and Associates, Inc. (Cambridge, MA), has studied Spacesuit Trauma Countermeasure System for Intravehicular and Extravehicular Activities under NASA Grant NNX12AC09G. The main objectives were to: 1) analyze data for correlations between anthropometry, space suit components, and injury, 2) model human-spacesuit interaction, 3) design and develop modular protective devices to mitigate injury, and 4) quantify and evaluate human- spacesuit interaction using a suite of sensors [14].

The first objective was addressed by a study published in 2014. The study quan- titatively evaluated the causes of astronaut shoulder injury and performed a meta- analysis investigating injury trends, proposing an injury classification system, and creating predictive statistical shoulder injury models using a database of 278 astronauts that included anthropometric measurements, training record, and injury record [3, 2]. It found that percent of training performed in the planar HUT was the strongest predictor variable for injury, while training frequency and recovery between sessions were also important variables. It also identified that bideltoid breadth, expanded chest depth, and shoulder circumference were the most relevant anthropometric measurements for predicting injury. The second objective was addressed by Diaz at the IEEE Aerospace Conference in 2014, where a biomechanical analysis using OpenSim (Stanford, CA) was performed to understand the effect of the space suit on muscle activation and force generation on the knee using motion capture data and EMU joint torque data [5]. The third objective was addressed by developing injury protection concepts, evaluating materials for their offloading capabilities, and eventually developing both passive and inflatable protective device prototypes. The fourth and final objective of evaluating human-spacesuit interaction has been addressed, but

23 methods and tools are continually being improved. A human subjects experiment was performed at David Clark Company and at NASA Johnson Space Center using the David Clark Mobility Suit and the NASA developmental Mark III suit. A pressure sensing system was built to evaluate pressures over the arm for this experiment, and the results on sensor performance are analyzed and discussed [3]. An additional commercially produced pressure sensor measured pressures at the shoulder for this experiment, and a quantitative analysis of the human-suit interaction at the shoulder was published [8]. The two pressure sensing systems were used in conjunction with kinematic inertial measurement units, and the kinematics data has also been published [4]. The quantitative techniques used in this thesis and in the preceding research present a novel way to understand human-spacesuit interaction. Prior to this grant, studies only included cataloging incidence and mechanisms of injury, but none had assessed the human-suit interface with experimental methods. The implications of this research will help to influence suit techniques and future spacesuit design.

24 Chapter 3

Sensor Systems and Experimental Design

Through prior work on characterizing the human-suit interface, it was determined that the following suite of pressure-sensing systems and inertial measurement units were to be used [3, 8].

3.1 Sensor Systems

3.1.1 Low Pressure Sensing System, the "Polipo"

A custom-built, low-pressure sensing system was designed for placement along the arm for 5-60 kPa pressure ranges [3]. These sensors were created at the Massachusetts Institute of Technology in conjunction with researchers at the Wyss Institute for Biologically Inspired Engineering at Harvard. Known as the Polipo, this low pressure- sensing system uses 12 soft hyper-elastic sensors to measure low-pressures applied to the body under soft goods. The sensors are cast from a silicon rubber (EcoFlex0030, Smooth-On, Inc., Easton, PA), and after two individual pieces are mated, they are injected with a highly conductive liquid metal called galinstan (Gallium-Indium Tin eutectic, 14364, Alfa Aesar, Ward Hill, MA), in a spiral pattern to minimize strain readings. Prior to mating the sensors, a flex circuit made of kapton that has been

25 coated and laser cut in a specific circuit pattern is sandwiched between the two sensors layers. A detailed description of the design and manufacturing process can be found in reference [3]. These sensors sense pressure through a change in resistance of the galinstan as the channel walls deflect when normal pressure is applied to the completed sensor. The change in resistance corresponds to a change in voltage, which is then calibrated to correspond to the pressure value. Each individual sensor is housed in a "chele,"which are all connected through the Polipo garment, a wiring system developed to accommodate system requirements and human range of motion requirements. The final Polipo design, which integrated seven strands of copper wrapped polyester per sensor vest, gives the wire a resistance of 0.6 ohms/meter, while the polyester core allows it to be very durable and flexible, but the wiring itself was not elastic or electrically isolated. The wire was sewn in a zigzag pattern to achieve elasticity. The cheles housed the sensors, and the sensors were held in place by soldering the flex circuit with the copper wiring mentioned above. As the wires stretch with movement, the ends of the wires are fixed into place with hot glue. The cheles and the rest of the Polipo were connected to a conformal base layer using Velcro, and protected by another conformal cover shirt to prevent catching of the wires or movement of the sensors. According to Anderson, the pressure-sensing system achieved both high weara- bility and utility, however, a design concern mentioned for future iterations was improving sensor wiring durability, which proved to be a limitation after several hours of wear inside the spacesuit performing EVA motions. Tears in the elastomer caused sensor failure, and the sensors performed sub-optimally under static loading due to creep effects and hysteresis. Another important area of future work mentioned was to improve manufacturability such that the process is less highly-skilled, takes less time, and fewer sensors fail during the construction process.

In an effort to capitalize on Anderson's design suggestions for future iterations of the low-pressure sensing system, two major possibilities were investigated to address the durability and manufacturing process concerns mentioned above.

In order to address manufacturing concerns, the possibility of using a 3D-printed

26 sensor. rather thaii a hand-manufactured sensor. was investigated. The W'yss Insti- tute for Biologically Inspired Engineering at Harvard developed a 3D-printed carbon grease sen1sor that could efficieitlv and effectively sustain an electric current, shown in Figure 3-1. Carbon fiber nanotnlbes are suspended in grease. and contact between the llanotubes creates a complete circuit to sustaim an electric current when a voltage is applied. After viewing preliminary resistance tests conducted by colleagues at the

WvYss. it was determined that these 3D-printed sensors prvecd to be less reliable ill their pressure measurements because naliottibe shifts led to inconsistient resistances

across each sensor. This was verified with arbitrary resistance measurements using a voltmneter. The 3D-printed carbon grease sensors were not pursued.

Figure 3-1: Printed carbon-grease sensor with electrode extensions. (Image Source: Wyss at Harvard, 2014)

For (irability concerns, a conniercial replacement for the hand-sewn copper

wiring was sewn in order to improve garment elast icitv and iinhnize tearing where the

copper wiring met the sensor. A suitable onie-stranded version of a conductive tape

was found through AMOHR Tecinisehe Textilien GnmbH. a company in Germany

that produces technical narrow fabrics for various purposes. AIMOTAPE Conduct

Nylon + Elastoner #45708. containing 2 insnlated copper strands was custom or-

dered as a replacement for the Polipo. which can be seen iii Figure 3-2. The AIOHR

two-stranded conductive tape was implemented in a new version of the Polipo by

CostnmeWorks in Somerville. MA. The original galinstan sensors, which are difficult

27 to manufacture, were used ilI the second version of the Polipo. however, due to seiisor nmanufacturing issues leading to sensor failure. the second version of the Polipo was not tested in the following experiments.

Figure 3-2: AT\(OHR two-stranded conductive tape used for second Polipo iteratioll.

3.1.2 Novel High-Pressure Shoulder Sensor

The Pliance sensing system developed by Novel GmbH. a German comnpaimny that specializes in dynamic pressure distribution measurement technology, 'an be used for an accurate mleasiuremlelnt of pressure 1(d load distribution on boti 1(ard and soft surfaces. The Pliance system was connected to a range of flexible, elastic seil- sors iade from capacitive transducers with high-tecb elastomers. These sensors are

calibrated through pre-determined loading sequences so as to create a baseline for

future measurements. guarantee accracv amd generate reproduciile data [8]. The

accompanying Pliance software gives the user the ability to acquire and store pres-

sure (istribuition data. view absolute pressure values in each sensor of the sensor ilat

network. playack mileasuremlelnts. and view maxiium1111 pressure. force 81(1 contact

area. The particular sensor used in our experiment and past experiments is a nodi-

fied S2073 sensor mat approximlaitely 22.4 cm x 11.2 cm with 128 individual senlsors

arranged in a grid of 1(6 by 8. Each sensor is 1.4 (111 ill length and width and can

measuire pressures between 20-600 kPa at a resolution of approximlately 1 kPa. The

Pliance systeill uses tell 1.2 V nickel metal hydride batteries with 2000 mAh. and

the sensor is rul at 330 mA. While the data collection rate can be adjusted. for the

purposes of our experiment, the data, was recorded once every 0.02 s (50 Hz). The

28 sensor imat was kept in place using the Polipo's base layer mentioned above, wvhich was equipped with a rectaigular pocket interface that housed the Novel sensor mat.

Low-Pressure High-Pressure Novel APDNI Inertial Polipo sensors sensor and hardware 'MeasurementUnit

A) B) C)

Figure 3-3: Experimental Sensor Systemis: A) Low-pressure Polipo sensors, B) High- pressure Novel shoulder sensor C) APDM Opal inertial measurement unit. (Image Source: Anderson. 2014)

Prior to any experinients. the Novel sensor is calibrated to ensure accurate data

collection during official mneasurenment trials. The calibration device used ws also

provided by Novel GmbH and was developed specifically for use with sensors devel-

oped by Novel and their Pliance sensing system. The calibration device consists of an inflatable rubber bladder that is housed by secure rigid plates. The sensor being calibrated is placed on the calibration board and centered within the alpparatis.

Compressed air is then fed into the device, thereby exerting pressure on the sensor

nat. The Novel software provides caliiration steps to lhad the sensor mat at vain-

ous known pressures in order create calibration curves create( within the software.

Calibration files are stored for subsequent testing.

3.1.3 APDM Inertial Measurment Units

The APDM Opal Inertial Measurement Unit (IMU) Sensing systeii (Portland. OR) consists of three accelerometers, three gyroscopes, and three nagnetometers. A

Kalnan filter integrates these signals into an orientation quaterion for each IMU.

The IMUs were placed in-phine with one another to optimize the output for isolated off-axis rota- joint movements, but their relative orienitations allow the detection of tions [3]. Three sensors were mounted internally on the upper arm. lower arm. and

29 Low- Pressure Polipo -- Sensor Network

High-pressure Novel Sensor Mat

Body Mounted Opal IMUs

Figure 3-4: Placeineit of the ill-suit sensor systems. (Image Source: Anderson. 2014) chest. Three cxternally imounted sensors were correspondingly iouinted oil the upper and lower spacesuit ami and suit torso. Each sensor is 4.8 x 3.6 x 1.3 ciii and weighs approxiinately 21 g. Tlhe gyroscopes and imagnetonieters were recalibrated before placed on each sul1ject to take into account the iagnetic environment and inimilize the gyroscope drift over tiie. They are powered by a lithiuiI battery at 3.7

V nloiliniaI, nd the imiaximumiliii current through the sensor is approxiimately 56 mA.

IMU seisoi data was collected wirelessly and continuously synchronized in real time.

3.2 Spacesuit Testing Experimental Design

This experiment was performed using two subjects in the David Clark Launch and

Entry Development Suit. The suit was pressurized aid tested at venting pressimre (0.25 psi). iiltermedliate pressure (2.5 psi). and full pressure (:3.5 psi). While the

EIU defines 4.3 psi as "full pressure . David Clark pressurizes their suits to 3.5 psi ill order to iicrease mobility 1)it ,minitai a smaller safety mgin for oxygen partial pressure requirements. They wvere asked to perforn a series of upper body notions inside the spaceslit while lying iii the recumbent position. These series of upper- body motions is niilmed at characterizing') the hunan-suit interactions. Three isolated joint nmovenmenits vere evaluated: elbow flexion /extension. shoulder flexion/extension. and shoulder abduction/adduction. i addition. one nmulti-joint functional task was I evalulated: the cross-body reach.

Elbow Flexil/Extenslo V The subject stands away from the donning stand supported by their own effort. Beginning with both arms relaxed at their side, palms k s Do facing anterior, the subject bends the anis at the elbow through s ' their maximum range of motion. The subject then releases to the relaxed position. MO M

Shoulder Fexion/Lxtension The subject stands away from the donuing stand supported by their own effort. Beginning wsith both anns relaxed at their side, the subject bends the arms at the shoulder through the sagittal plane. The subjects move through their maximun range of motion. The subject then releases to the relaxed position. Shioulder Abduction/Adduction The subject stands away from the donning stand supported by their own effort. Beginning with both arns relaxed at their side, the subject bends the anns at the shoulder through the coronal plane The subject moves through his or her mAximumi rangP ot motion The subject then releases to the relaxed position Cross-Body Reach The subject begins in a relaxed position and reaches across their body to touch their hip on the opposite side. The subject mos a their ann up to chest level and sweeps in front of their body. When the arm is extended in front of the shoulder, the subject touches the helmet on the same side The niovement is then repeated with the opposite arm.

Figure 3-5: Descriptions of the four upper body motions performed during the spacesuit experiment: three isolated joint notions (elbow flexion/extelision. shoulder flexion/extension. shoulder abduction/adduction) and one functional task (cross body reach). (Image Source: Anderson. 2014, Hilbert et al. 2014)

The test protocol consisted of 15 repetitions of the four different motions inside

the spacesuit. These repetitions were divided into three groups of five repetitions

to allow for assessment of fatigue or changes ill biomnechanical strategies. Motionls

XVere divided into movement groups such that the order was counterbalanced within

the groumlp [3]. Prior to the test. subjects were trained on each motion and allowed

to practice it until they were comfortable ill order to maximized mnotion coilsistency

duirilng the experiment. The subject performned each notion iii the prescribed order

of the movement group, with no less than a 5-minute break between each movement

group in order to (ollect subjective feedback and to allow the subject to rest. After

all three imovment groups were completed, there was an intermittent rest period

to increase the pressure iii the suit. The subject was first tested in the unsuited

condition, and then at the corresponding test pressulr('s in the suit. The pressure

profiles and joint angles were recorded throughout the experiment. A representative experiment schemlati( is showii in Figure 3-6, and the full experimental test plan can

31 he found inl Appendix A.

Movement Group 1 Movement Group 2 Movement Group 3

H 11 12 13 14 13 I1 14 12 12 14 11 I3

11: Elbow Flexion/Extension 12: Shoulder Flexion/Extension Si vvvr. 13: Shoulder Abduction/Adduction 14: Cross Body Reach S2 r

Figure 3-6: Experimental Design Test Protocol: Each imovenent group consists of a counterbalanced ordering of the motions. The motions studied were: three isolated joint iot ions (elbow flexion/extension. shoulder flexion/extension. and shoulder abduction/adduction) and a fiictional task motion (cross body reach). In each move- iment group. the specific nmotion was repeated 5 tinmes for a total of 15 repetitions per mlotionl.

3.3 Marine Protective Gear Experimental Design

In an effort to expand the applicalbility of the sensor systems. two rounds of experi-

ments were performed in conjunction withIi Protect the Force. a strategic consulting

firm specializing in product development for the U.S. aried forces.

Infantry soldiers and officers are a central comnponent of ground forces in the Ma-

rine Corps anod other branches of the military. According to the Marines, infantrymen

are trained to locate, close with and destroy the enemyn 1y fire and umaneuver, or repel

the eiemv's assault by fire aiid close co1bat. Riflenem serve as the primary scouts.,

assault troops and close colmlbat forces within each infantry unit. Crucial to combat

iission effectiveiness is ensuring each Marine's safety. However. in order to provide

safety in the form of heavy armiiior, often physical mobility aid strength must be less-

ened or compromised to carry heavy loads of arimor in addition to the gear Marines

are required to carry. Iii an effort to provide lightweight but effective armmor to lesseii

32 heavy loads and increase imobility while wearing armor. the Marine Corps System

Command has developed several prototypes of advanced larine protection gear as alternatives to the current gear provided to Marines.

Both experiments were performimed with the same subject ill (lifferelt proteetion gear configiiratioiis: 1) the interim capability, USMC Plate Carrier (PC) and neck plates. 2) the current capability. USNIC Improved Modular Tactical Vest (IMTV), 3) the newly designed Ballistic Base Layer (BBL) protective garment and 4) the future

capability, the plate carrier combined with the BBL protective garment. Different

configurations of the protection gear were tested for their mobility. the shoulder con-

tact pressure, aid the subjective evaluation for comfort. fatigue, and mobility. This

is critical in order to ensure the future capabilities being currenItly developed will

provide an improvement in the design and the use of the protection gear.

Figure 3-7: Different US\IC protection gear conifiguratiois used during testing

One subject was tested in the Man Vehicle Laboratory. at the Massachusetts Iii-

stitute of Technology (Cambridge, MA) oil two different occasions (December 2015

and Jaimuary 2016). The subject corresponded with the Narine infantrymen anthro-

polmetrics provided by Protect the Force as seen iln Table 3.1. Similar to tlie spacesulit test experimental desigm. the experiment colmsisted of

15 repetitions divided into three groups of five repetitions of four different mo-

tions inside the spacesuit. Three isolated joint movements were evaluated: shol-

33 Table 3.1: Anthropometrics from typical Marine compared to anthropometrics of subject used Marines [Subject Height 5'8" 5'11" Weight 176 lbs 190 lbs Waist Circumference 34.5" 34.5" Chest Circumference 40.5" 38" der flexion/extension, the vertical shoulder abduction/adduction (defined as simply the shoulder abduction/adduction in Figure 3-5, and the addition of the horizontal shoulder abduction/adduction shown in Figure fig12. The multi-joint functional cross-body reach was also evaluated.

SHOULDER ADOUCTION (A), ABDUCTION (B)

Figure 3-8: Horizontal shoulder abduction/adduction. Beginning with their arms extended at shoulder height, shoulder width apart, the subject bends their arms at the shoulder in the transverse plane. The subject moves through his or her maximum range of motion. The subject returns to the initial start position then releases to the relaxed position.

This motion is particularly useful to combine basic motions performed by Marines during operations: reaching helmet on its side, reaching opposite side of the body, or extending the arm in front of the body. The subject performed each motion in the

34 prescribei order (Iof the movement group. with n1o less than a 5-iiiiinute break 1b)etweeli each movenient group ill order to collect subjective feedback an( to allow the subject to rest. After all three inoveiiient groups were conmlleted(. there was ain iiiteriiiittenit

rest period. The subject was first tested( in the unsuited condition. ald then with the

corresponiiig protective gear coiifiguratioiis. At the en(l of the second experinelit

following all iotiolis outlined in the experimienital design, the subject )erufoled a

set of rifle carry motions in Configurations 1 an(l 4. The rifle carry iotions were

perforimled ill the followillg sequence for each condition: 5 repetitions. 10 second pause, aild 5 repetitioils for a total of 10 rifle carry repetitions per configuration. The rifle

(ally motiol1s were performed with a 7.2 lb pipe similar in shape to an M16 A2 rifie.

The shoulder contact pressure profiles al(l joint angles were recorle(trlonghoIt the

experimeiit. A representative experiment scheiatie is shown in Figure 3-9.

Movement Group 1 Movement Group 2 Movement Group 3

11 12 13 14 j3 11 14 12 12 14 11 13

11: Shoulder Flexion/Extension 12: Shoulder Abduction/Adduction vertical S1 / \/\A 13: Shoulder Abduction/Adduction horizontal 14: Cross Body Reach S2 V0

Figure 3-9: Protective Gear Experimental Design Test Protocol. Each movement group consists of a couiiterbalanced ordering of the motions. The motions were: three isolated joint motions (shoulder flexion/extension, shoulder abduction/adductioli vertical. shoulder abduction/adduction horizontal) and a functional task motion (cross body reach). In each imoveineit group. the specific motion was repeated 5 times for a total of 15 repetitions per motion.

35 Chapter 4

Novel System Results and Discussion

The following chapter presents a variety of analysis intended to provide an understanding of the human-suit shoulder interface. The diagram in Figure 4-1 shows the presentation of the data and the orientation of the Novel sensor with respect to the subjects shoulders. This diagram shows that the lower portion of the sensor with respect to the diagram corresponds to the anthropometric region toward the clavicle and front of the body, whereas the upper portion overlays the back of the shoulder, toward the shoulder blade.

4.1 David Clark Experiment

For the David Clark Launch and Entry Development Suit, two main categories of data are presented for the Novel pressure sensing system: 1) the overall pressure distributions and 2) the pressure profiles seen in each of the motions. For the following results, data from the elbow flexion/extension was excluded as it was deemed less relevant to the shoulder portion of the human-suit interface. Hilbert first determined that analysis of pressure distributions aids in determining which areas of the shoulder are experiencing the highest pressures during upper body motions and providing a visual understanding of what is happening at the human-suit shoulder interface. Ad-

36 Diktal fnd of Shoulder Ba dg i u w suusc 111m Im I

Figure 4-1: Orientation of the Novel Sensor. The orientation Corresponds to the information i i each pressure (listtribution figure. Coloring is for orientation and is not related to pressure scales. (Image Source: Hilbert 2015) ditionally, analyzing pressure profiles as a function of tie provides how the pressures vary over the course of a particular movement while allowing us to determine whether there is any time effect [8]. Upon visual inspection we can claim that Subject 1 had a narrower an(d taller body frame than Subject 2. which will be critical to the discussioli of varying contact pressures.

4.1.1 Pressure Distributions

The pressure distribution mnaps for Subject 1 and Subject 2 are shown in Figures 4-2 and 4-3. The figures show the pressure distributions as a color scale representing the pressure in kPa. For practical reference. 100 kPa provides approxinately the same pressure as a 1 kg (2.2 lbs) weight oi one square centimeter of the skin. For each of the motions at each of the pressurized conditions. the pressure (listributioli map represents the pressure (listribution at the peak of the movenient, or the pressure distribut ion at the moment when the highest pressure appeared.

Looking at Subject I's neasuireients in Figure 4-2. it is evident that as suit presslurizatloll increases. contact pressure increases as well. From visual inspection, it is not clear whether any one motion has higher Overall pressures than the other motions. At 0.25-psi vented condition. pressure is concentrated along a line just above

37 Subject 1 Sh FI/Ext Sh Abd/Add CrBReach 160 140 120 100 IA P80 60 40 20 I 0 kPa 160 140 120 100

Ln~ 80 60 40 20 I 0 kPa 4,) 160 140 120

CL 100 (n 80 60 40 20 I 0 kPa

Figure 4-2: Contact Pressure listributions for each inotion at ( (ch Cressurizedeon- dition for Subject 1.

38 the clavicle for all three motions, likely over soft musculature near the top of the shoulder as was seen in Hilbert's results. These areas of pressure concentration (peak of ~75 kPa) are accompanied by a secondary area of pressure concentration at the most distal end of the lower edge of the sensor. Likely, the sensor was being slightly pinched by the chest and the armpit in each of the motions. However, after dynamic inspection of the data in the form of pressure distribution videos, the pressure line can also be attributed to a crease in the Novel pressure sensor at the peak mobility point of a motion. During motions where the subject retains high mobility, a crease would form in the mat at the top of the shoulder due to the rigid nature of the mat, and this produces artificially high pressure values. At the 2.5-psi intermediate-pressurized condition, the pressure (peaks between -100 and ~140 kPa) is now concentrated in a region centered just above the end of the clavicle toward the acromion for all motions. At this pressure and higher pressures, the Novel mat did not seem to demonstrate any creasing, most likely due to limited mobility and the mat pressing against the suit. The peak pressure is highest for the cross body reach, followed by the shoulder abduction/adduction, and lastly the shoulder flexion/extension, but the location and shapes of the pressure distributions are nearly identical in all motions. At the 3.5-psi full-pressurized condition, the pressure distributions maintained the size and shape of the peak pressure locations for the intermediate pressure condition, however, the magnitudes of the peak pressures reach -160 kPa at the clavicle and acromion.

Looking at Subject 2's measurements in Figure 4-3, the pressure distributions follow similar trends to Subject 1's such that as suit pressurization increases, contact pressure also increases. At the 0.25-psi vented condition, the artificially high crease pressure band is only seen in the shoulder flexion/extension. For the shoulder abduction/adduction and cross body reach, there is a large but low-pressure (-40 kPa) peak at the top of the shoulder toward the clavicle and chest. At the 2.5-psi pressurized condition, the size of the peak pressure area is reduced and becomes more concentrated in the acromial region toward the distal end of the shoulder for all motions. The shoulder abduction/adduction experiences the highest peak pressure (-120 kPa), followed by the shoulder/flexion extension (-100 kPa), and the

39 Subject 2 Sh Fl/Ext Sh Abd/Add CrBReach 140 120 100 80 En 60 40 20 I 0 kPa 140 120 100 80 60 40 20 Lfl I 0 kPa 140 120 100 CL 80 U') 60 C0 40 20 I 0 kPa

F'igiire 4-3: Contact pressure distributions for each 1i1otion at each pressurized cou- dition for Subject 2.

40 cross body reach (~70 kPa). For the 3.5-psi pressurized condition, the size, shape, and location of the peak pressures remains almost identical to the 2.5-psi pressurized condition. The peak pressure locations are concentrated at the top of the shoulder toward the acromion for all three motions. The peak pressure magnitudes for the shoulder abduction/adduction and cross body reach approximate to ~120 kPa, with the shoulder flexion/extension peak pressure magnitude reaching -140 kPa at the acromion. Comparing subjects we see that Subject 1 experiences higher pressure than Sub- ject 2 in all motions at the fully pressurized condition (3.5-psi pressurization). It is interesting to note that for both subjects, pressure was concentrated in a consistent location across all motions: approximately on the acromion and just above the clavicle and the soft musculature at the top of the shoulder.

4.1.2 Pressure Profiles

Pressure profiles as a function of time are now considered at each pressurized condition for each subject, shown in Figures 4-4 through 4-7. For each motion, selected pressure profiles for different sensors are plotted for each of the three movement groups. The individual sensiles are chosen based on whether they experienced the peak pressure on the mat at any moment in time during the motion repetition, and they represent the highest magnitude profiles of each general trend of sensor response. Since it was determined that at lower pressurized conditions where the subject retains high mobility the Novel mat develops a crease and reads artificial pressures, the pressure profiles of the lowest pressurized condition, 0.25-psi, are not shown. All plots have the same scales: the y-axis being pressure in kPa from 0 to 160 kPa, and the x-axis being a normalized time axis. Each cube in the grid represents a 0.1 sec interval in the horizontal direction and a 20-kPa interval in the vertical direction. Normalizing the x-axis and plotting each of the profiles on the same time scale allows for easier comparison. While each motion included five repetitions per movement group, only the two most consistent repetitions are shown since the subjects found it very difficult to remain consistent in the recumbent position. All motion pressure

41 U'

Subject 1- 2.5 psi pressurized condition Movmt. Group 1 Movmt. Group 2 Movmt. Group 3

-&j .1

.0 I-t 11

A- -&jr U N

Figure 4-4: Contact pressure profiles for all motions in the 2.5-psi pressurized condition for Subject 1. profiles are shown, however in some cases, it is impossible to identify the profile of the motion.

Starting with Subject 1, we will analyze the pressure profiles by motion. The shapes of the general profile for the shoulder flexion/extension are consistent for both the 2.5 psi pressurized condition and the 3.5 psi pressurized condition. The shoulder flexion/extension appears to have two distinct peaks per repetition in approximately the same location at the top of the shoulder where the second peak is only a sensile or two closer to the chest than the shoulder blade. Analyzing the subject video taken during the experiment, it appears that the subject would shift inside the suit during the beginning of the motion during flexion, and then shift again after the peak of the motion during extension, hence the slightly higher contact pressures seen in the second peak. The shift in full body position can be attributed to air displacement in the soft suit in the recumbent position since the subject did not have

42 El

Subject 1- 3.5 psi pressurized condition Movmt. Group 1 Movmt. Group 2 Movmt. Group 3

UJ *I t

Vt ttj

CA ~J4M

L) k 4!

Figure 4-5: Contact pressure profiles for all motions in the 3.5-psi pressurized condition for Subject 1.

-I the stability of standing on his feet. There is also a constant contact pressure seen at the top right corner, which corresponds to the shoulder blade. This is due to resting on the shoulder blade and back in the recumbent position and the shoulder activity that occurs in the shoulder blade during the shoulder flexion/extension. For the shoulder abduction/adduction, the general profile for the peaks are consistent, however, the magnitudes of the peaks in the 3.5 psi pressurized condition are highly inconsistent between movement groups. During the shoulder abduction/adduction, the same body shift due to air displacement in the suit occurred as it did in the shoulder flexion/extension. There is an initial spike in contact pressure as the body shifts toward the feet in the suit and initiates contact at the top of the shoulder, then again as the body shifts back upward toward the head and initiates contact during the contrary movement. In the cross body reach movement, the pressure profiles change in between pressurized conditions. In the 2.5 psi pressurized condition, there are three peaks: the two larger peaks occur at the top of the shoulder during the motion, and there is a much smaller peak between the two larger peaks that occurs at the shoulder blade. These peaks coincide with the multiple motions necessary to complete the functional task motion. In the 3.5 psi pressurized condition, the same two major peaks occur without the smaller peak occurring at the back of the shoulder.

Looking next at Subject 2's pressure profiles, the shapes of the general profile for the shoulder flexion/extension are consistent for both the 2.5 psi pressurized condition and the 3.5 psi pressurized condition. Unlike Subject 1, the shoulder flexion/extension appears to have only one distinct peak per repetition in approximately the same location at the top of the shoulder as Subject 1. While the same body shift was seen inside the suit as Subject 1, due to the different anthropometries between subjects, the suit displacement had less of an effect on Subject 2 since Subject 2 had overall larger anthropometric measurements. For the shoulder abduction/adduction, the general profile for the peaks are consistent and nearly identical to the shoulder flexion/extension profile. Before the large prominent peak, there is a smaller, less distinct peak of contact pressure that occurs on the back of the shoulder toward the armpit (top left corner of the diagram) during the 2.5 psi pressurized condition. This small

44 Subject 2- 2.5 psi pressurized condition Movmt. Group 1 Movmt. Group 2 Movmt. Group 3

X LLI

.0 B . rf. ~11wi

Figure 4-6: Contact pressure profiles for all motions in the 2.5-psi pressurized condition for Subject 2. back-of-shoulder peak also occurs during the 3.5 psi pressurized condition, but not in all three movement groups. In the cross body reach movement, the pressure profiles remain extremely consistent between pressurized conditions, only the magnitudes of the first large peak changes. Subject 2's cross body reach experiences only two major peaks instead of three as seen in Subject 1: initial large park at the top of the shoulder, and a second smaller peak occurring at the back of the shoulder blade next to the arm pit.

Comparing the pressure profiles between subjects, it appears that while the general pressure distributions appear to be similar, the pressure profiles give the resolution to observe distinct differences between subjects. The primary location for contact pressure in Subject 2 is located slightly to the left of the primary location for contact pressure in Subject 1. This can be for one of two reasons: either the mat placement was slightly different between subjects and so the primary locations for both subjects

45 Subject 2- 3.5 psi pressurized condition Movmt. Group 1 Movmt. Group 2 Movmt. Group 3

x LU

- -J

-o t 4*1

r NZ23A

U fa It

Figure 4-7: Contact pressure pr ofiles for all motions in the 3.5-psi pressurized condition for Subject 2.

6 corresponds to the same anthropometric location on the body (the acromion), or the differences in anthropometric measurements between subjects caused the primary contact pressure location to vary slightly between subjects but remain in the general area at the top of the shoulder. The only motion profiles that vary significantly between subjects are the pressure profiles of the cross body reach motions between subjects. While the two peaks seen for Subject 1 are both concentrated at the top of the shoulder, the two peaks for Subject 2 shift from the top of the shoulder to the back of the shoulder blade. This supports the claim that for functional movements, contact pressure locations can vary depending on anthropometric measurements. Another example is demonstrated during the instances in which there is contact with the shoulder blade: Subject 1 tended to experience contact pressure on the inside of the shoulder blade toward the spine, whereas Subject 2 experienced contact pressure on the outside of the shoulder blade toward the armpit.

4.1.3 Statistical Analysis

In order to more clearly understand the effects of pressurization conditions, motion type performed, and subject variability, a statistical analysis was performed. Five peak pressure values were extracted from the data for each motion during each movement group. Each subject had a total of fifteen peak pressure values for each motion during each condition. The mean and standard deviation were calculated for the peak contact pressures, and a statistical analysis was performed. A multi-factor ANOVA (Factor A- motion, Factor B- pressurization condition, Factor C- subject) was performed, as well as Kruskal Wallis tests since shoulder abduction/adduction at 0.25 psi and cross body reach at 2.5 psi for Subject 2 were not normally distributed. For all tests, an alpha value of 0.05 was used to determine significance. First, we will analyze the effect of pressurization on mean contact pressure. Main effects for pressurization condition (p <0.0005) were found with both the multi-factor ANOVA. The effect of pressurization on mean contact pressure across motions can be seen in Figures 4-8 and 4-9. For all three motion types in both subjects, mean contact pressure increases, significantly in most cases, as suit pressurization increases. For the

47 shoulder flexion/extension, both subjects experienced a significant change in contact pressure between vent pressurization and full pressurization as well as intermediate pressurization and full pressurization. For the shoulder abduction/adduction, Subject 1 experienced a significant change in contact pressure between all three conditions, whereas Subject 2 did not experience any significant change in contact pressure between the intermediate and full pressurization conditions. Finally during the cross body reach, Subject 1 experienced a significant change in contact pressure between vent pressurization and full pressurization as well as vent pressurization and intermediate pressurization, but no significant change was found between intermediate and full pressurization. Subject 2 experienced significant changes in contact pressure across all conditions during the cross body reach. Since the pressure profiles reflect the same data as the pressure distributions seen earlier, all vent pressure profiles recorded and considered in the statistical analysis are likely higher than actual pressure experienced by subjects since peak data reflects pressure during the mat crease.

Next, we will analyze the effect of motion type on mean contact pressure. Main effects for type of motion were not found (p=0.73) for the multi-factor ANOVA. The results are presented in Figures 4-10 and 4-11. There is also no single motion that produces higher contact pressure than any other motion across all cases. At vent pressurization, Subject l's shoulder abduction/adduction contact pressures are significantly lower than the other two motions. However, at the same pressurization, Subject 2 experiences the highest contact pressures during the shoulder flexion/extension and the lowest contact pressures during the cross body reach, those being significantly different from each other but neither from the contact pressures found during shoulder abduction/adduction. It is difficult to determine the validity of motion type results during the vent pressurization condition due to artificial mat pressures, so while there are no conclusions to be drawn from the results, the results would not be considered for recommendations. At intermediate pressurization, there are no significant differences in contact pressure between any of the motion types. At full pressurization, the shoulder abduction/adduction differs significantly

48 Subject 1 2 0 Julder Flex)Ext Lr'lrAbdSAdd 7 rssbody Reach

60 -

01 01 20

1300-

20-

Vent Pressure Intermediate Pressure Full Pressure

Figure 4-8: Effects of pressurization on imean contact pressure for Subject 1.

Subject 2 J43- Shoulder Flex-Ext Shoulder Abdci ---iCrossbody' Reach

100

2 IsO

velit Pressure Irterr'rede Pressure Full Pressure

Figure 4-9: Effects of pressIIrizatioII OH mIea coutact l)ressure for Subject 2.

49 250t Subject 1 Vent Pressure viIntermediate Pressure Full Pressure

200C

1501

0 Rud ExFle r ouidr AtxdAdd r' dy Reach

Figure 4-10: Effects of motion type on mean contact pressure for Snbject 1.

Subject 2 Vest Pressure I1Intermediate Pressure -Full Pressure

Shoulder FlexiExt Shoulder AbdAdd Crossbody Reach

Figure 4-11: Effects of motion type on mean contact pressure for Subject 2.

50 intermediate Pressurization

1 2

Shoulder Flex,.Ext Shoulder Abd/'Add Crossoody Reach

Figure 1-12: Effect at subject on mean contact pressure for iflterllediate pressuliza- tion.

Full Pressurization - ubI I DuI 2

200 - IOU -

Shouldei Flex Ext Shoulder Abd/Add Crossoody Reach

Figure 4-13: Effect of subject on iean contact pressure for full pressurizationl.

51 from both the shoulder flexion/extension for both subjects. However, in Subject l's case it is significantly higher than the other two motion types whereas Subject 2's case demonstrates that it is significantly lower than the other two motion types. It can be said that at intermediate pressure the contact pressures experienced are all similar between motions types, and at full pressure the contact pressures experienced are similar between the shoulder flexion/extension and the cross body reach but not the shoulder abduction/adduction. Finally, we will analyze the effect of subject variability on mean contact pressure. Main effects for different subjects were found (p<0.0005). The results are presented in Figures 4-12 and 4-13. At both intermediate and full pressurization, Subject 1 experiences higher contact pressures than Subject 2 with every motion type. In the cross body reach at intermediate pressurization and in the shoulder abduction/adduction at full pressurization, this difference in contact pressure is statistically significant. For reasons mentioned above, results at vent pressurization are not shown. Subject variability can be attributed to two major factors: 1) subject anthropometry, which can determine how often they make contact and how high the contact pressures will be, 2) subject experience, which determines how experienced the subject is at mitigating contact within the suit to maintain their comfort and increase the amount of time they can tolerate spending in the suit.

52 4.2 Protect the Force Armor Gear Prototype Ex-

periments

The advanced Marine gear aims at distributing loads and pressures more evenly across the shoulders as opposed to having concentrated areas of extreme pressure at the top of the shoulders. The Novel pressure sensor was located at the top of the shoulder, and the data will be displayed in an identical fashion to the shoulder data from the David Clark spacesuit shoulder experiment. The pressure distribution maps for the different configurations are shown in Fig- ures 4-14 and 4-15. The figures show the pressure distributions as a color scale representing the pressure in kPa. For each of the motions at each of the pressurized conditions, the pressure distribution map represents the pressure distribution at the peak of the movement, or the pressure distribution at the moment when the highest pressure appeared. The movements that provide the most insight on changes in pressure distributions across the shoulder are the vertical and horizontal shoulder abduction/adduction movements. Figure 4-14 shows the pressure profiles during moments of peak pressure for the four separate suited configurations and four separate motions in kPa. The top two configurations are the configurations without the BBL (the potential future capability). When the Novel mat is used on top of the shoulder during motions of high mobility, it causes the mat to bend, which is shown across all four conditions as a diagonal increase in pressure across the mat. Configuration 2 (frog -shirt + IMTV) show the highest overall pressures distributed across the top of the shoulder. The more lightweight current capability, Configuration 1 (frog shirt + PC), also shows heavy pressures across the top of shoulder as well as mat bending. The most significant comparison to make is between Configuration 1 and Configuration 4; both use the PC but the BBL has also been incorporated into Configuration 4. The pressure distribution across the shoulder is similar, however, the pressures in Configuration 4 are much lower overall across all sensors. This indicates the BBL has relieved the wearer of some of the pressure/weight from the PC.

53 Sh. FI/Ext. ShAbd/Add V. ShAbd/Add H. CrB Reach 100 90 80 70 on p60 fl 50 C C 40 t} It 30 i~i~..m 20 10 0 kPa 'I I-T! 100 90 J-t 71W-i'1- 80 70 on 60 IC 50 C C 40 (-7 30 A j.4. 20 10 I 0 kPa 100 90 80 rn 10 or 60 IC 50 C C 40 U 30 20 10 I 0 kPa 100 90 80 70 60 on 42 50 C 10 0 (-7 30 20 10 U 0 kPa

Figure 4-14: Pressure distributions of all motions for different US\JC arnior configu- rati(1s.

During the horizontal aidiction/adhuetion. the weight of the arumor is plaeed heavily (1 the shoulders. aid depell(ling on the widtll of the straps. either manifests itself as an acute pressure point or more even distribution. In Configuration 1 anld

Configuration 2. the pressure distribution shows the iiat bendiig phenoiiienon. Ili addition. the surrounding pressures are higher with the frog shirt and PC thian the frog shirt and IMTV. While the IMTV is heavier., it is most likelv that the wider straps of the INITV cause a wider (listributioli of pressure of the armor weight, thereby relieving the subject of a concentrated pressure.

100 90 80 70 g 60 50 40 30 20 10 0 kPa

Figure 4-15: Pressure distributions for rifle carry motion for Configuration 1 (on left) and Configuration 4 (on right).

Figure 4-15 shows the pressure distributions at the mnoment of peak pressure for rifle movements between the two different PC configurations. The figure clearly delon- strates that the BBL helps minimize pressure at the top of the shoulder when usiig the PC. The frog shirt loes little to nmninze pressiures at the tops of the mnotionis.

Overall, it appears that the IMTV distriblites the weight of itself better than the PC oii its owii does, eveni though the PC is 1mch lighter. However. the addition of the

BBL reduces the load of the PC ini some cases and is not helpful in others.

4.3 Conclusions and Future Work

These results yield no common conclusions across suit types or subjects. For the

David Clark Lauinch and Entry Development Suit. both subjects experieiice(d sig-

nificant contact pressures at the top of the shoulder and acromion. However, the the two suilbjects magnituides of contact pressures were significantly different between and furthermore, it was not clear whether certain imotions elicited more contact than

others. The effects of motion type oi contact pressure cannot be generalized across

subjects as they are likely affected by individual anthropomnetry, suit fit. and bionie- chanics, but the information gathered for each subject can be used to decrease the risk of astronaut injury when applied individually. The less experienced subject (Subject 1) experienced the highest pressures, but both subjects experienced discomfort on the top of the shoulder over time.

The results yielded for the Protect the Force armored gear can draw some general conclusions, but since only one subject was tested, further testing is necessary in order to validate these conclusions. While heavier, the IMTV provides a better pressure distribution than the PC due to its wider straps. When the BBL is incorporated, it has the same effect as the IMTV (in terms of distribution) by distributing the PC load across the shoulder. It also appears that this load exerts an overall lesser force than the IMTV. The vertical abduction/adduction causes pressure across the shoulder between all motions regardless of configuration. The IMTV and frog shirt seem to provide an overall less pressure than the PC and frog shirt. During rifle carry motions, the BBL significantly offloads pressure from the PC as compared to the frog shirt.

The most important point to address is the validity of the results. While the Novel sensor system proves to be state-of-the-art pressure sensing equipment, it may not be the optimal equipment for the particular human shoulder application. When placed at an interface with high mobility, the sensor is susceptible to false, artificial readings caused by creases in the sensor. As a future alternative, it would be ideal to incorporate a network of small, variably placed sensors across the joint and rest of the body. A sensor such as the Novel S2012 shown in Figure 4-16, which is 2 cm in diameter, if paired with many others, could get a general profile for pressure readings across the shoulder while remaining small enough to gather data across a seemingly flat surface.

Further studies should integrate the spacesuit pressure and joint angle data found in other work with metabolic data in order to understand how fatigue and injury influence the metabolic work necessary for spacesuit operations. All of this information would allow us to more accurately determine where injury is most probable, incorporate a quantitative measurement for fatigue, and ultimately influence air-pressurized

56 spacesuit design in the future.

Figure 4-16: Novel Single S2012 Sensor with 2 cin diaieter (Image Source: iiovel.(e)

57 Chapter 5

International EVA Capabilities

"The United States will seek to cooperate with other nations in the peaceful use of outer space to extend the benefits of space, enhance space exploration, and to protect and promote freedom around the world"-National Space Policy (2006)

5.1 A Case for EVA Standardization

Despite the fact that our collective EVA capabilities are advanced compared to other capability requirements needed for a potential mission to Mars, there is a lack of cooperation that causes difficulty when trying to develop facilities to accommodate different suits. The most obvious interoperability requirement is hardware compati- bility. The current NASA spacesuit, the EMU, has already been described in Chapter 2. The International Space Station (ISS) also uses the Russian Orlan suits for EVA operations. While both NASA and Roscosmos are both currently developing newer models than the ones mentioned, we will compare in-flight capabilities for simplicity. Even though equipment and tools developed by NASA and Roscomos perform the same functions in the same environemnt, differences in operations philosophies lead to very different design solutions [10]. NASA's collection of EVA suits from B.F. Goorich (Mark-IV IVA suit), David Clark (Gemini high altitude pressure suit), Hamilton Sus- trand, and a handful of other companies indicates a very wealthy nation with many designs to choose from, but it also indicates a non-linear EVA suit evolution [7]. On

58 the other hand. Russia has iever been a very wealthy nation. and the coinlbinati(oni of linited funding. a single supplier (Zvezda). and organic national design philsophy

has served to create Russian EVA suits that are rugged. straight forward. and easy

to naintain ii-orbit [71.

Figure 5-1: R ear entry opening for Russian Orlaii-M spacsuit. (Image Source: NASA)

The spacesuit (.urr1enltly used by cosinionauts is the Russian Orlcan-MK imodel. which is the fifth varint in the Orln series of scinli-rigid onle-piece space suit iod- els designed and ianufactured by NPP Zvezda [15]. Unlike American EVA stilts. Russian EVA stilts have had a direct evoluitionary path as they have all been built

by NPP Zvezda [7]. The Orln stilts were first used inl flight during Salytit-6 and Salyut-7, anld variouis mnodels have beenl introduced for Mir and ISS operations. The Orln spacesiuits are scinli-rigid: the enclosure incorporates a HUT. integrated with a hehinet and miade of ahiiintinn alloyv, and soft stilt arins and 1lg enclosures [1]. They inchidc a rear hatch entry through the backpack that allows it to be self-donned ill

approxiinately five miinutes. which is shown inl Figure 5-1. The Orlan suits comne inl a

59 "one size fits most" standard size that can be used by cosmonauts with various (but limited) anthropometric characteristics. The Orlan suits also contain an integrated, regenerative (closed-loop) life support system (LSS). The first three Orlan suits (Or- lan, Orlan-D, and Orlan-DM) used a 20-m electric umbilical which served as a safety tether and provided the power supply, radio communication, and telemetry. The Orlan-DMA was the first suit that was fully self-sustaining, that is, it could be used without the electrical umbilical because it was provided with a removable unit that incorporated an electrical power source (battery), radio and telemetry system, and an antenna-feeder device. The Orlan-DMA also introduced a second safety tether. The Orlan-M, which was used on the ISS from 2001-2009, took into account the experience of Orlan-DMA operations on Mir and the additional requirements imposed by operations on the ISS: 1) the suit's dimensions were enlarged, 2) an additional helmet-top window and protective glass for the main window were introduced, 3) a calf bearing and the third pressure bearing (elbow) on the suit arm were introduced, 4) one of the safety tethers was given variable length, and 5) the carbon dioxide control cartridge (CCC) capacity was increased. Power supply, radio comms, and telemetry were available for both the self-contained mode and via the 25-m electrical umbilical cord from the station. The service characteristics (mobility, donning/doffing, field of view) and anthropometric ranges were improved from earlier models. The suit was also provided with attachment points for Simplified Aid for EVA Rescue (SAFER). The Orlan-MK model's main improvement is the installment of a mini-computer in the Portable Life Support System (PLSS) backpack. The computer processes data from the spacesuit's various systems, issues a warning in the event of a malfunction, and outlines a contingency plan that is displayed on an LCD screen attached to the right breast of the spacesuit [15]. The current Orlan spacesuit assembly weighs 238 lbs, operates at 5.8 psi with a 100% oxygen atmosphere, and has a maximum EVA duration of 7 hours. It is designed for an on-orbit lifetime of 12 EVAs or 4 years without return to Earth [11].

To compare, the current EMU spacesuit assembly was designed to accommodate individuals ranging in size from the 5th percentile Asian female, to the 95th percentile

60 Caucasian male, which made a "one size fits all"design impossible [10]. While sizing differences do not pose a problem for interoperability between suits, it does affect which individuals can participate in the astronaut/cosmonaut programs. There are significant hardware differences that make EVA cooperation difficult. While both suits function perfectly well at vacuum, it is not physically possible for the EMU and Orlan to go to vacuum simultaneously in the same airlock. First, the Shuttle EMU is nearly four inches wider than the Orlan suit, which made it difficult for the EMU to transit through the small Russian hatches [7]. The coolant loop and sublimator water that the EMU and Orlan-M use in their respective life support systems is also incompatible. While both suits use approximately 1 gallon for each EVA, the Orlan uses distilled water for the sublimator function but adds silver ions to the coolant water supply loop to extend its storage life [7]. In contrast, the EMU uses iodized potable water for both the coolant and sublimator functions. If the Russians must perform an EVA from the ISS airlock, they must empty the EVA coolant loop supply of American water and substitute it with Russian water, then purge and refill the supply with American water after the EVA [7]. Furthermore, because of the unknown way in which the suits' respective coolant systems may react over the long term to differing water supplies, it would be difficult to support simultaneous EVAs. Another airlock discrepancy is in back-up oxygen supply tank replenishment: the Orlan-M stored its back-up oxygen supply at 6,000 psi in reserve tanks that can be easily detached and replaced on-orbit whereas the EMU's reserve tank cannot be refilled with its 900 psi oxygen anwhere except on the ground due to the inability to check for leakage while on-orbit [7]. In order to avoid decompression sickness (DCS), decompression cycles also differ: the Orlan-M operates at 5.8 psi which require a 30-45 minute nominal oxygen prebreathe time and the EMU operates at 4.3 psi which requires a 4 hour oxygen prebreathe before it can go EVA from the station's 14.7 psi sea level atmosphere. Thus, when designing for both the U.S. and Russian EVA systems onboard the ISS, a new airlock was required. The Quest Airlock, a joint airlock, attached to the ISS in 2001, and acts as a stowage area for spacewalk hardware as well as a staging area for crew members preparing to

61 conduct a spacewalk [22]. Both suits also have their own airlocks on station [11]. With two spacesuits, three separate airlocks, plus hundreds of EVA hand tools in use, the requirements on instructor, crew, and flight controller certification training are enormous with several thousand hours of certification and proficiency work and need to be condensed or simplified [10].

Another significant factor is the effect of non-hardware issues: non-native lan- guages, training facilities on separate continents, and different task development philosophies can present major problems when handling difficult or non-routine situations and can even create minor disagreements in everyday operations. There are extensive challenges for interoperability during mission operations because during the planning phase, personnel must integrate requirements from numerous foreign and do- mestic sources [10]. For example, Russian and American crew members operate in the EMU while performing EVA tasks on the Canadian-manufactured robotic arm; this requires task/procedure integration, integration of the event into overall ISS operations, establishment of flight rules, etc. [10]. The current solution to minimize this complexity is EVA planning and integration responsibilities lie with the organization whose suit is being used, however, this could be eliminated with one jointly-developed suit for all operations on an international spacecraft or station. After planning, training the EVA tasks is also necessary, and in the previous example, while the task will be trained by U.S. instructors, technical expertise for the task lies with the Canadians [10].

At first glance, the Russian and EVA suit systems seem to share a resemblance and they are very "functionally similar" in that they are both meant to carry out the same functions [7]. However, while these two systems were designed to achieve similar tasks, they are "the products of such disparate national outlooks, design philosophies, operating parameters, and fabrication methods as to make them almost incompatible" [7].

The concept of international cooperation with respect to EVA has not been com- pletely neglected. After the ninth International Academy of Astronatuics (IAA) Man- In-Space Symposium in Cologne, 1991, members of all national space agencies agreed

62 18012 9

Figure 5-2: The U.S. E\IU and Russian Orlan-M spaeesuit shown side by side. (Inage Source: NASA)

to form an IAAA subgroup to exchange ideas on EVA interoperability and supply reeoiinnleii(lations to solutions to EVA interoperability problems [7]. Iii 1992, the

U.S./Russia Agreement on Cooperation in Space Exploration was signed [1]. NASA and Hamilton Standard (HS. now Hamilton Sundstrand) showed interest in Zvezda's experience in the development and operation of orbit-based EVA suits. That year,

ESA and Roscosmos separately agreed to Initiate a requirements analysis and con-

(eptual design study to determine the feasibility of joint spacesuit developillent- the EVA 2000 [1]. WThen the Space Station Freedom (SSF) became the ISS and was expanded to include Roscosnos, ESA and Roscosnos pushed for U.S. support on a joint development of a new spacesuit based o1 the EVA Suit 2000 to become the one and only spacesuit system on the ISS [20]. Not only is it expensive to develop and prototype a new EVA system. but to do so while incorporating the different design philosophies and their contractors can seem insurmountable: it is clearly not cost effective [7]. Moreover, the EMU was already too far along for them to consider

63 it. The EVA suit 2000 program eventually also faltered due to financial difficulties [20]. There have been several other contracts between Roscosmos and NASX: com- parative analysis of US and Russian EVA suits (Figure 5-2), feasibility of bringing them together, provision for EVA in the Russian suit undertaken from the US airlock, development of means for unassisted rescue of ISS crew members during EVA (SAFER), training U.S. specialists in Orlan operations, and training US astronauts in wearing Russian EVA suits [1]. One of the only successful joint suit-system programs between NASA and Roscosmos is the development of the Russian Simplified Aid for EVA Rescue (SAFER). It was initially developed in the U.S. as an element of the EMU so that should the primary crewmember-to-station restraint tether fail, there would be a backup means of retrieving the crewmember since the ISS could not ma- neuver for rescue [20]. Since 1997, astronauts and cosmonauts have used Russian and U.S. made spacesuit systems interchangeably and with increasing frequency, however, mission operations planning and training would become significantly easier with the design of one single spacesuit for all future joint missions. According to Harris, NASA and Roscosmos had (and still currently have) three choices in interfacing their divergent spacesuit systems:

1. an expensive "clean sheet" approach, giving up the current agency specific development (then the Shuttle EMU/Orlan) and building a whole new suit,

2. symbiosis by joining the two suit systems with as many interchangeable components and operational methods as possible,

3. or, a level of interoperability that would cover efforts to find a minimal interface while actually changing their respective systems little [7].

The third option has been somewhat accomplished since Harris published his book in 2001 with the introduction of the ISS Quest Airlock. The second option seems more reasonable than starting with a clean sheet and building a whole new spacesuit, however, a cost analysis would be in order to determine whether option two would be that much more cost efficient than option when merging major suit incompatibilities.

64 However, if we want to continue to expand beyond LEO, into planetary EVA, it is imperative to build (or modify) a spacesuit as a collaboration between all relevant agencies.

65 Chapter 6

Conclusions

Extravehicular activity is perhaps the most rewarding and complex aspect of human spaceflight. Perhaps in the near future, EVA will be performed outside of low-Earth orbit on the surface of Mars. There are still major EVA suit design challenges to overcome, as well as challenges in standardization for streamlined international cooperation. Additionally, there are major physiological and technical challenges humans will need to overcome in order to accomplish successful long-duration flight missions. The contributions of this research are:

1. 'an increased understanding of the human-spacesuit interaction specifically at the shoulder interface: while pressure magnitude can vary based on anthropometric measurements, it can be confirmed that pressure magnitudes at the top of the shoulder must be addressed with protective measures and in future design.

2. While the Novel sensor system proves to be state-of-the-art pressure sensing equipment, a network of smaller, variably placed sensors may be a preferred means of analyzing the human shoulder interface for clearer data.

3. With the future pressure sensing design improvements mentioned above, this method of measuring contact pressures can and should be expanded to protective wear and other applications.

66 4. There have been attempts to incorporate EVA capabilities among space agencies, but a stronger push is necessary between U.S. and Russia for complete equipment standardization.

With regard to the EVA human-shoulder interface experiment, further studies should integrate the spacesuit pressure and joint angle data found in other work with metabolic data in order to understand how fatigue and injury influence the metabolic work necessary for space operations. With regard to policy and standardization in EVA operations, NASA and Roscosmos should reevaluate current suit development projects and attempt to consolidate projects to develop a joint spacesuit program such as the EVA 2000 program. Each of the specific aims addressed in this thesis provides a different suggestion for approaching the issues currently present in EVA. It is imperative that these issues be overcome if we plan to continue toward the ultimate goal of human planetary exploration.

67 Appendix A

Human-Suit Interface Pressure Evaluation

68 Human-Suit Interface Pressure Evaluation

MIT Man Vehicle Lab & David Clark Company

Preparedby PierreBertrand, Alexandra Hilbert, SabrinaReyes, MIT

1 Introduction The objective of this research is to develop an understanding of how the person interacts with the space suit, and use that information to assess and mitigate injury. Our approach is to quantify and evaluate human-space suit interaction with a pressure sensing tool, focusing on the arm and shoulders under different loading regimes. Additionally, inertial measurement units (IMUs) will be placed both internal and external to the space suit arm to assess biomechanics. This portion of the study builds from previous collaboration between the MIT Man Vehicle Lab and the David Clark Company. Informal objectives include evaluating the feasibility of a synchronized pressure sensing as a platform used inside the space suit. MIT has developed a prototype platform, consisting of custom and off-the-shelf sensors and an integrated data acquisition system, all incorporated into a modified athletic garment, capable of sensing pressure at various locations along the arm and shoulder. Establishing a precedent and proof of concept for this methodology will open the doorway for future collaboration and technology development.

2 Test Summary One subject, two, time permitting, will be asked to perform the test protocol in the Boeing space suit. Subjects will be selected based on availability from David Clark personnel who meet the medical requirements for in-suit testing. These individuals have a great deal of experience working inside the space suit so will not have to develop new, potentially confounding movement strategies. The subjects will be wearing the pressure sensing and IMU systems while performing the tests, and pressure profiles and angle histories will be recorded. The test protocol will consist of 20 repetitions of 4 motions inside the space suit. The selected movements use the upper body where the sensors are placed. The 5 motions are 3 isolated joint movements (Elbow flexion/extension, Shoulder flexion/extension, and Shoulder abduction/adduction) and 1 functional task (Cross Body Reach). Prior to the test, subjects will be trained on each movement and allowed to repeat it as many times as they desire. For each movement, the 20 repetitions will be further subdivided into 4 groups of 5 repetitions each. This is done to evaluate subject fatigue or potential change of biomechanical strategies over the course of the test period. After each group of movements, qualitative information on subject comfort and hot spots will be collected. The information will also be collected after training. Each of these test conditions will be counterbalanced and randomized.

69 3 MIT Hardware The human-suit interface is currently an unknown in space suit characterization. Pressure measurements would allow greater insight into how these interactions occur and help characterize suit performance. Additionally it would allow us to prevent injury incurred by motion inside the suit. There is currently no method by which to characterize this pressure. The two systems selected to measure pressure are targeted at different pressure sensing regimes.

The pressure sensing system is integrated into one conformal athletic garment. Both pressure sensor systems are mounted to the shirt as described below. Finally, a cover shirt slides easily over the sensors to prevent catching and ensure proper sensor placement. 3.1 Novel Pressure Sensing System The garment has a pocket interface over the shoulder to house the Novel pressure sensor, which is used for the high-pressure sensing regime. The high pressure regime is at the interface between the person's body and the hard upper torso of the suit. A Novel pressure sensing mat has been used previously in a study by the Anthropometry and Biomechanics Facility (ABF) on an Extravehicular Mobility Unit hard upper torso.

e One commercially available Novel pressure mat, S2073 with 128 sensors " Each sensor is 1.4cm in each dimension and pressure range between 20-600kPa * Mat slips into pocket over shoulder

e On-board data collection with electronics mounted at the base of the back * Similar system used inside the extravehicular mobility unit by the Anthropometry and Biomechanics Facility without modification for a shoulder load study * Sensor runs at 330mA current e Battery is 10 1.2V nickel metal hydride The system is certified to the European safety standard 93/42/EEC (Annex 1X). * Due to the construction of the battery it is unlikely that water or sweat will come into contact with the electronics board of the battery pack. It is also unlikely that a small amount of moisture would create an electrical shortcut. * The pedar NiMH 2000mAh battery pack is internally secured with an overheating and an overcurrent protection (Polyswitch). * Worst case scenario for puncture: On the transmitter side of the sensor mats a voltage of 7 V (effective) = equal to 20 Vpp is applied (pp = peak to peak). The maximum current for a shortcut is 100 mA(pp) if one directly touches the transmitter. For technical applications the resistance of the human body is typically considered to be 1 - 2.4 kOhm. In that case the maximum current would be 8 - 20 mA(pp).

70 Figure 2: Novel Pressure sensing system. A) Sensor mat. B) Data acquisition and battery

3.2 Polipo Pressure Sensing System This shirt is worn by the subject and has targets over which the low pressure sensors are mounted. The Polipo, or octopus in Italian, is the system of 12 sensors which were developed as part of this research effort for low-pressure sensing under the soft goods. These sensors are placed over the arm in a way that targets anticipated hot spots, and secondarily for uniform coverage. The sensors are detachable from the athletic garment, allowing independent pressure sensing system. It also allows for shifting the sensors to concentrate them over a certain region of the body.

- 12 developmental sensors distributed over the arm

* Detachable system transferrable between subjects with velcro e On-board data collection with electronics mounted at the base of the back

- Each sensor powered with constant current of.5mA

o Microcontroller shown; new board will be fabricated (not shown)

0 The entire board in nominal operation with 12 sensors is estimated to be around 100mA - Battery selection is TBD but at the moment may be an off the shelf 9V battery. A typical 9V has about 500mAh, so we are estimated to have 4 hours of use - Shorting the sensor wires of one circuit will result in -. 5mA through the short - A sensor short through the sink wire of another sensor will result in -1.1mA - Worst case scenario would short the sink wire of all 12 circuits giving -6mA. This is highly unlikely

71 Figure 2: Polipo pressure sensing system. A) Sensors mounted on sleeve. B) Microcontroller. Arduino shield not shown

3.3 APDM IMU Sensing System Additional information about the human-suit interface may be gathered using IMU data collected inside the space suit. There is a joint angle difference between the person's movement and that of the space suit. This is due to the resistance of a gas pressurized suit to movement, as well as (in some instances) anatomically inaccurate rotation due to bearing movement. Calculating the joint angles measured internal and external to the suit would help elucidate these differences. Previous studies performed by the ABF and researchers at the University of Maryland have evaluated the use of IMUs inside a gas pressurized space suit. This experiment uses similar methods, mirroring a previous study performed by our research group inside a gas pressurized suit at David Clark Company. This data will be used not only to determine biomechanical differences but also to help find points of maximum and minimum movement to analyze the pressure profiles. It will be matched with video data to improve the results. Sensors will be placed on the lower and upper arm of the subject, not in contact with the pressure sensors. An additional chest mounted IMU will serve as a reference for shoulder rotation data. Three sensors will be placed external to the suit, two on the upper and lower arm and one on the suit upper torso.

* Commercially available APDM Opal inertial measurement unit (IMU) - 3 internally mounted sensors on the upper and lower arm and chest - 3 externally mounted sensors: Upper and lower spacesuit arm and suit torso - Each is 4.8x3.6x1.3 cm (lxwxh) and weighs less than 22g e Lithium Ion battery at 3.7V nominal - The capacity found online is 450mAh. Assuming that it can last minimum 8h (as said in the documentation), the current is max 56 mA. It's maximum is1.6 hours of operation, so the current would be 28mA - The worst case scenario is venting of the battery. Safety precautions include aluminum base to protect the person, battery protection circuit, safe charging features. Probability estimated at .000001

72 The Opal movement monitor Figure 4: Opal IMU sensor from APDM

4 Detailed Test Plan This test will be performed by one subject or two if time permits. The following tasks will be performed both suited (at pressures: 0.25 psi (venting), 2psi (intermediate pressure) and 3.5 psi (full pressure)) and unsuited as described in the configurations above. The first time the task is performed suited, each task will be repeated through 5 repetitions, whichever comes first. After each of the 5 movements is performed, the subject will rest for 5 minutes and subjective data will be collected. The subject will then repeat the movement sequence and rest period three additional times.

Below are the tasks the subject will be performing in this test campaign.

Elbow Flexion/Extension

The subject stands away from the donning stand supported by their own effort. Beginning with both arms relaxed at their side, palms facing anterior, the subject bends the arms at the elbow through their maximum range of motion. The subject then releases to the relaxed position.

ShoulderFlexion/Extension

The subject stands away from the donning stand supported by their own effort. Beginning with both arms relaxed at their side, the subject bends the arms at the shoulder through the sagittal plane. The subject moves through their maximum range of motion. The subject then releases to the relaxed position.

Shoulder Abduction/Adduction

The subject stands away from the donning stand supported by their own effort. Beginning with both arms relaxed at their side, the subject bends the arms at the shoulder through the coronal plane. The subject moves through his or her maximum range of motion. The subject then releases to the relaxed position.

Cross Body Reach

73 The subject stands away from the donning stand supported by their own effort. Beginning with both arms relaxed at their side, the subject will reach across their body in an attempt to touch their hip on the opposite side. The subject will then move their arm up to chest level and sweep their arm in front of their body in the horizontal plane. When the arm is extended straight in front of the shoulder, the subject will then attempt to touch the helmet at the position of their ear on the same side. The movement is then repeated with the opposite arm.

Table 1 shows a summary of all functional tasks each run will consist of, and a cumulative time for the run as currently scheduled. Each subject will perform these tasks in the order specified.

Minute Task Type Description MinCCount

Elbow Isolated Stand free of donning stand and bend elbow 1.30 1.30 Flexion/Extension Shoulder Isolated Stand free of donning stand and bend shoulder 1.30 3 Flexion/Extension Shoulder 1.30 Isolated Stand free of donning stand and bend shoulder 4.30 Abduction/Adduction Stand free of donning stand and reach from Cross Body Reach Functional 2.30 7 overhead across the body, alternating arms Rest mounted in donning stand. Qualitative Rest 12 Information collected Table 1: Test variables matrix

Each of the subjects will perform this series of tasks identified in Table 1 four different ways:

1. Unsuited 2. Suited at 0.25 psi (venting pressure) in the Boeing suit 3. Suited at 2 psi (intermediate pressure) in the Boeing suit 4. Suited at 3.5 psi (full pressure) in the Boeing suit

The order of these tasks will vary between subjects, but the matched-pace unsuited run will always be completed last. In addition, some familiarization time is built into the test plan for each suit to allow the subject to become comfortable performing each task in the suit he or she has just donned. Not only will this make the subject more comfortable and safe while performing the tasks, but it will also reduce the possibility of familiarization of a task negatively affecting the outcome of the test

This test may be terminated by the subject at any time for any reason, or by the test conductor, suit technicians or suit engineer due to any safety or hardware concerns or concern for the suited subject. Between movement groups, subjective data will be taken from the subject. This will be

74 used as an indicator of subject fatigue and desire to terminate the test. An outline of the questions to be asked is shown in Appendix A.

The test will also be terminated in the event of unrecoverable suit system failure. Standard David Clark procedures will be followed regarding the failure of any suit system part, or any suit emergency.

75 5 Procedures

5.1 Test-Specific Pre-Test Safety Briefing

1. Anyone can stop this test at any time for any reason

2. Test personnel: Manage video camera, extension cords and functional task props at all times.

3. Suited Subject: We will ask you how you're feeling between each task, absent any other reports from you. After each series of 5 tasks, which will last approximately 2 minutes each for a total of 10 minutes, you will rest for at least 5 minutes.

5.2 Detailed Test Procedure

1. Initial IMU calibration

2. Review summary of test with subject

3. Conduct test-specific pre-test safety briefing

4. -Synchronization process

a. Close Motion Studio b. Connect IMUs and Novel system through sync box c. Turn on Novel and sync box d. Open Motion Studio with appropriate settings e. Initiate MATLAB timer tool f. Trigger the synchronization and begin the timer g. Unplug synchronization cables

5. -Test personnel places IMUs on the subject and notes location on the body

6. Subject dons pressure sensing systems

7. Polipo is turned on

8. Cover shirt is donned

9. -Body marks are pressed (1-acromion, 2-clavicle, 3-shoulder blade) Unsuited Test

Unsuited Calibration

10. Subject perform wrist pronation/supination 90 degrees (2 times)

76 11. Subject perform elbow flexion/extension 90 degrees (2 times)

12. Subject perform shoulder flexion/extension 90 degrees (2 times)

13. Subject perform shoulder abduction/adduction 90 degrees (2 times)

Unsuited Familiarization Session

14. Subject practices elbow flexion/extension

15. Subject practices shoulder flexion/extension

16. Subject practices shoulder abduction/adduction

17. Subject practices cross body reach task

Unsuited Data Collection Run

18. Subject performs 1st movement group

a. Allow subject to rest while prompting for subjective feedback

19. Subject performs 2nd movement group

a. Allow subject to rest while prompting for subjective feedback

20. Subject performs 3rd movement group

a. Allow subject to rest while prompting for subjective feedback

21. Body marks are pressed (1-acromion, 2-clavicle, 3-shoulder blade)

Suited Tests

22. Subject dons suit

23. Suit pressurized to venting pressure

24. Test personnel places IMUs on the space suit's arm and notes location (anthropometrics)

25. Suit technicians assist subject in moving from donning stand to functional task area

Suited Venting Pressure Test

NOTE: The subject completes 5 repetitions of the task. Time is not limited, but the task may be terminated if the subject is unable to complete 5 repetitions.

NOTE: Instruct subject to complete these tasks at what they consider to be a natural pace

77 NOTE: Request a report of any symptoms from suited subject after each task and ask qualitative questions from Appendix B during the 5-minute rest periods.

NOTE: Five minute break (minimum) is enforced between each group of movement tasks. Allow suited subject to take additional rest time as needed.

NOTE: Subject task order is counterbalanced for each subject and each movement run. The task order is provided in Appendix A.

NOTE: Subject may return to donning stand for rest if necessary at any point

Suited Venting Calibration

26. Subject perform wrist pronation/supination 90 degrees (2 times)

27. Subject perform elbow flexion/extension 90 degrees (2 times)

28. Subject perform shoulder flexion/extension 90 degrees (2 times)

29. Subject perform shoulder abduction/adduction 90 degrees (2 times)

Suited Familiarization Session

30. Subject practices elbow flexion/extension

31. Subject practices shoulder flexion/extension

32. Subject practices shoulder abduction/adduction

33. Subject practices cross body reach task

34. Subject returns to donning stand for rest (at least two minutes)

Suited Venting Pressure Data Collection Run

35. Subject performs 1st movement group

a. Allow subject to rest while prompting for subjective feedback

36. Subject performs 2nd movement group

a. Allow subject to rest while prompting for subjective feedback

37. Subject performs 3rd movement group

a. Allow subject to rest while prompting for subjective feedback

38. Suit technicians assist subject in moving back to donning stand

Suited Intermediate Pressure Test

78 39. Suit pressurized to intermediate pressure (2 psi)

40. Suit technicians assist subject in moving from donning stand to functional task area

Suited Intermediate Pressure Calibration

41. Subject perform wrist pronation/supination 90 degrees (2 times)

42. Subject perform elbow flexion/extension 90 degrees (2 times)

43. Subject perform shoulder flexion/extension 90 degrees (2 times)

44. Subject perform shoulder abduction/adduction 90 degrees (2 times)

Suited Intermediate Pressure Data Collection Run

45. Subject performs 1st movement group

a. Allow subject to rest while prompting for subjective feedback

46. Subject performs 2nd movement group

a. Allow subject to rest while prompting for subjective feedback

47. Subject performs 3rd movement group

a. Allow subject to rest while prompting for subjective feedback

48. Suit technicians assist subject in moving back to donning stand

Suited Full Pressure Data Collection Run

49. Suit pressurized to full pressure

50. Suit technicians assist subject in moving from donning stand to functional task area

Suited Full Pressure Calibration

51. Subject perform wrist pronation/supination 90 degrees (2 times)

52. Subject perform elbow flexion/extension 90 degrees (2 times)

53. Subject perform shoulder flexion/extension 90 degrees (2 times)

54. Subject perform shoulder abduction/adduction 90 degrees (2 times)

Suited Full Pressure Calibration Data Collection Run

55. Subject performs 1st movement group

79 a. Allow subject to rest while prompting for subjective feedback

56. Subject performs 2nd movement group

a. Allow subject to rest while prompting for subjective feedback

57. -Subject performs 3rd movement group

a. Allow subject to rest while prompting for subjective feedback

58. Suit technicians assist subject in moving back to donning stand

Post-Test Procedures

59. External IMUs removed from suit

60. Depressurization of suit and suit doffed

61. Subject remains in LCVG with pressure sensors and IMUs in place

62. Body marks on the shoulder are recorded (1-acromion, 2-clavicle, 3-shoulder blade)

63. Subject debrief (any final subjective feedback)

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