Astronaut Extravehicular Activity : safety, injury & countermeasures; &, Orbital collisions & space debris : incidence, impact & international policy

Orbital Collisions & Space Debris

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Incidence, Impact & International Policy

by

Roedolph A. Opperman B.Eng., Mechanical Engineering University of Pretoria, South Africa, 2006

Submitted to the Department of Aeronautics and Astronautics and the Engineering Systems Division in Partial Fulfillment of the Requirements for the Degrees of

Master of Science in Aeronautics and Astronautics and

Master of Science in Technology and Policy at the

MASSACHUSETTS INSTITUTE OF TECHNOLOGY

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Author Certifie September 2010

© 2010 Massachusetts Institute of Technology. All Rights Reserved.

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Department of Aeronlities.&-Astronautics, and Engineering Systems Division August 6, 2010 i by ... . .. .

Dava J. Newman, Ph.D.

Professor, MacVicar Faculty Fellow, HST Affiliate Department of Aeronautics & Astronautics, and Engineering Systems Division Thesis Supervisor A ccepted by ...

Dava J. Newman, Ph.D. Professor of Aeronautics and Astronautics and Engineering Systems Director, Technology and Policy Program

7 / s

Accepted by ... ...

Eytan H. Modiano, Ph.D. ssoiate Professor of Aeronautics and Astronautics, Chair, Graduate Program Committee

&

Orbital Collisions & Space Debris

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Incidence, Impact & International Policy

by

Roedolph A. Opperman

Submitted to the Department of Aeronautics and Astronautics and the Engineering Systems Division on August 6, 2010 in partial fulfillment of the Requirements for the Degrees of Master of Science in Aeronautics and Astronautics and Master of Science in Technology and Policy

Engineering Abstract

Extravehicular Activity (EVA) spacesuits are a key enabling technology which allow astronauts to survive and work in the harsh environment of space. Of the entire spacesuit, the gloves may perhaps be considered the most difficult engineering design issue. A significant number of astronauts sustain hand and shoulder injuries during extravehicular activity (EVA) training and operations. In extreme cases these injuries lead to fingernail delamination (onycholysis) or rotator cuff tears and require medical or surgical intervention. In an effort to better understand the causal mechanisms of injury, a study consisting of modeling, statistical and experimental analyses was performed in section I of this thesis.

A cursory musculoskeletal modeling tool was developed for use in comparing various

spacesuit hard upper torso designs. The modeling effort focuses on optimizing comfort and range of motion of the shoulder joint within the suit.

The statistical analysis investigated correlations between the anthropometrics of the hand and susceptibility to injury. A database of 192 male crewmembers' injury records and anthropometrics was sourced from NASA's Johnson Space Center. Hand circumference and width of the metacarpophalangeal (MCP) joint were found to be significantly associated with

injuries by the Kruskal-Wallis test.

Experimental testing was conducted to characterize skin blood flow and contact pressure inside the glove. This was done as part of NASA's effort to evaluate a hypothesis that fingernail delamination is caused by decreasing blood flow in the finger tips due to compression of the skin inside the extravehicular mobility unit (EMU) glove. The initial investigation consisted of a series of skin blood flow and contact pressure tests of the bare finger, and showed that blood flow decreased to approximately 60% of baseline value with increasing force, however, this occurred more rapidly for finger pads (4N) than for finger tips (ION). A gripping test of a pressure bulb using the bare hand was also performed at a moderate pressure of 13.33kPa (100mmHg) and at a high pressure of 26.66kPa (200mmHg), and showed that blood flow decreased 50% and 45%, respectively. Excessive hyperperfusion was observed for all tests following contact force or pressure, which may also contribute to the onset of delamination. Preliminary data from gripping tests inside the EMU glove in a hypobaric chamber at NASA's

Johnson Space Center show that skin blood flow decreased by 45% and 40% when gripping at

applied to the finger pad than the finger tip. Our results indicate that the pressure on the finger pads required to articulate stiff gloves is more likely to impact blood flow than the pressure on the fingertips associated with tight or ill-fitting gloves. Improving the flexibility of the gloves will therefore not only benefit operational performance, but may also be an effective approach in reducing the incidence of finger injury.

Space Policy Abstract

EVA injury is only one of many dangers astronauts face in the extreme environment of space.

Orbital debris presents a significant threat to astronaut safety and is a growing cause of concern. Since the dawn of satellites in the early 1950's, space debris from intentionally exploded spacecraft, dead satellites, and on-orbit collisions has significantly increased and currently outnumbers operational space hardware. Adding to this phenomenon, the advent of commercial spaceflight and the recent space activities in China and India to establish themselves as space-fairing nations are bound to accelerate the rate of space debris accumulating in low Earth orbit, thus, exacerbating the problem. The policies regulating orbital debris were drafted in the 1960s and 1970s and fail to effectively address the dynamic nature of the debris problem. These policies are not legally enforced under international law and implementation is entirely voluntary.

Space debris is a relevant issue in international space cooperation. Unless regulated, some projections indicate space debris will reach a point of critical density, after which the debris will grow exponentially, as more fragments are generated by collisions than are removed by atmospheric drag. Space debris proliferation negatively impacts human spaceflight safety, presents a hazard to orbiting space assets, and may lead to portions of near-Earth orbit becoming inaccessible, thus limiting mission operations.

The aim of this research effort was to review current international space policy, legislation and mitigation strategies in light of two recent orbital collision episodes. The first is the February 2009 collision between a defunct Russian Cosmos spacecraft and a commercial Iridium satellite. The second is China's display of technological prowess during the January

2007 intentional demolition of its inactive Fengyun-IC weather satellite using a SC-19

anti-satellite (ASAT) missile. In each case the stakeholders, politics, policies, and consequences of the collision are analyzed.

The results of this analysis as well as recommendations for alternative mitigation and regulatory strategies are presented.

Thesis Supervisor: Dava J. Newman, Ph.D.

Title: Professor, MacVicar Faculty Fellow, HST Affiliate

While spending the past three years surrounded by thick, windowless concrete walls that allow for no cell phone reception, accumulating long hours of research conducted in artificial lab lighting and many a late nights - some without sleep, others spent sleeping on a lab couch, desk, or the occasional centrifuge - I came to realize that I could not have kept this up without the help

that I received from so many. I would like to thank the following people without whom this work would not have come to fruition.

Professor Dava Newman, my academic advisor for her active support and guidance for both the

engineering and policy sections of this work. Thank you for teaching me so much about not only scholarly research but also life in general. Thank you for inspiring me, driving me, and igniting my passion for space flight. Before I came to MIT it had been the farthest thing in my mind to get involved in this field, thinking that a young guy from a small country at the southern tip of Africa does not stand a chance. You were the one who proved me wrong and who introduced me to this amazing adventure. Thank you for all that you have done for me on so many occasions

and for your big role in preparing me for the future. I deeply appreciate all that you have done for me and I will never forget it.

Dr. James Waldie for all your support and advice throughout this study. You have always

shown a keen interest in my work and at so many occasions guided me to ask the right questions and helped me to overcome hurdles along the way. Thank you for being such a great role model to look up to, not only in a professional setting but also a personal one. You have definitely left a

lasting impression on my life.

Dr. Alan Natapoff for being such a great resource and mentor when it comes to all things

statistical and also for being a good friend, someone with a sincere interest in my life and who always makes time to help. I really appreciate all your guidance and assistance and I will truly miss our talks.

Dr. Jeff Jones for making it possible for me to spend a summer at NASA's Johnson Space

Center and for entrusting to me such great responsibilities throughout the astronaut hand injury study. I appreciate all that you have done.

Dr. Rafat Ansari for inviting me to spend a summer at NASA's Glenn Research Center and for

the opportunity to learn about the technical side of our study. Thank you for all your invaluable advice and wisdom regarding my future career, for fueling my interest in becoming a pilot and for believing in me.

My funding sources: ILC Dover, the MIT Portugal Program (MPP) and the National Space

Biomedical Research Institute (NSBRI) for funding my research efforts.

The people at ILC Dover, especially Phil Spampinato, Keith Splawn and George Sharpe, for their support.

Dr. Luca Pollonini, Jim King and Jason Hochstein, my colleagues with whom I worked

closely while at the two NASA centers. I really appreciate all your help and hope to work with you again in the future.

All the NASA folks for helping me throughout this research effort. Dr. Michael Gernhardt who

is the lead from the NASA Johnson Space Center's Extravehicular Activity Physiology System and Performance (EPSP) Project, for his input and suggestions in this work. Thanks also in particular to Lesley Lee, who was my point of contact at EPSP, for all her support and help with badging, shipping equipment etc. Other members of EPSP include Drs. Jennifer Tuxhorn,

Jennifer Jadwick and Jason Norcross. Dr. John Dewitt with NASA-JSC's Exercise

Physiology Lab, for his help with signal processing and experimental design of the pilot study.

Dr. Rick Scheuring for his suggestions, valuable knowledge on crewmember injury and for

including me in his daily activities at JSC. Dr. Sam Strauss for his work in contributing findings to the EVA injury database and with the NBL and Dr. Robert Ploutz-Snyder for his helpful comments and suggestions in our statistical analysis. Elisca Hicks for helping with the badging process on countless occasions.

Angela Lesser and Trent Barret from the ILC field office at Johnson Space Center, as well as

the glove box technicians for their support and helpfulness in scheduling and running sessions in the glovebox room.

Ed Hodgson and Steven Dionne from Hamilton Sundstrand for their input and for loaning the

suit hardware used in a preliminary glove study at MIT.

Holzbaur et al. (2005) for making available the SIMM upper extremity model used in this study. Sofia d'Orey, my office mate, research colleague and close friend. Thank you for all the

countless things you have done for me - be it showing me how to optimize my matlab code, providing an ear to listen to my problems, or making me smile with a witty comment or

attempting to make me look when you are taking photographs. Obrigado! ©

All of my fellow MVL'ers, especially the EVA group (Brad Holschuh, Allie Anderson and Aaron Johnson) for all the adventures in the lab and during our EVA meetings. MVL rocks!!!

Brad especially, for being my partner in crime when it comes to EMU spacesuit research. It was the many hours of CoD that pulled me through. I salute you: Underpants!

Past MVL students, including JunJay Tan (My first officemate, the person who introduced me

to the nerf gun, and a good friend), Chris Oravetz (who's lifestyle serves as a great inspiration and who helped me achieve my goal of skydiving before the age of 25 (2 more since and

counting...)), Dr. Jessica (Edmonds) Duda, who has always been very helpful and with whom I had the privilege to work in tackling 2.183. Drs. Leia Stirling and Erika Wagner, for their

examples and helpfulness.

Anthony Wicht and Stephen Zoepf, fellow graduate students who were very helpful in

All the MIT administrative and support staff, especially Sally Chapman, Sydney Miller, Ed Ballo, and Liz Zotos to whom I am eternally grateful for all their help on countless occasions.

Also Barbara Lechner, Beth Marois, Marie Stuppard and Robin Pringle for all their helpfulness.

Tod Billing and Dave Robertson, for their technical expertise and guidance in design and

fabrication projects.

All my homes away from home: The de Jagers, to whom I was able to make many memorable

trips in Philly and for having South African beer on hand. Baie dankie! Mr. & Mrs. Robinson for their generous hospitality throughout my stay in Cleveland. The Whitley's for hosting me in Houston, and The Railstons who often invite me to Wellesley to break away from the often stressful campus environment.

The Portuguese taxpayers, who indirectly funded me through the MIT Portugal Program to perform my research here in the States.

Denel Dynamics, for allowing me to pursue this great opportunity of coming to the U.S. for

graduate studies and for funding part of it.

Werner Hugo van Vuuren, my good high school friend for his example, inspiration, advice,

and patience throughout my stay in Harvard. Jy het my laat besef dat ek 'n sukses kan maak hier in die VSA.

Definitely not at the end of the list due to unimportance, my friends and family back home, for your encouragement and support even from afar. Ek sou dit nie sonder julle ondersteuning kon doen nie. Ek waardeer dit opreg en in my hart was ek altyd by julle.

Anyone whom I may have forgotten, please know that I appreciate all the support, guidance and impact you all had on my work.

Most importantly, my Father in Heaven, without Whose guidance, mercy and blessing none of this would have been possible.

Reik na die Sterre

Biographical Note

Roedolph Opperman was born in 1984 in Pretoria, South Africa, where he lived up until the time he moved to the United States in the fall of 2007. From 2003 to 2006, he attended the University of Pretoria, earning a Bachelor's degree in Mechanical Engineering with a minor in aeronautics and control. Upon graduation he worked for Denel Dynamics, a South African Aerospace company, where he stayed for about a year before enrolling to MIT to begin graduate studies as a dual Master of Science degree candidate in Aeronautics & Astronautics and Technology & Policy.

ACKNOW LEDGEM ENTS ... 5

TABLE OF CONTENTS... ... 9

INDEX OF FIGURES ... ... ---... 13

INDEX OF TABLES...-... ---... 17

LIST OF ACRONYM S AND ABBREVIATIONS ... 19

1. INTRODUCTION 23 1.1 Background...23

1.2 EVA Injury Problem Statement & M otivation ... 24

1.2.1 EVA Training-related Shoulder Injury ... 24

1.2.2 EVA Hand Injury... 24

1.3 Space Policy Problem Statement & M otivation...25

1.3.1 Orbital Collisions...25

1.3.2 Regulation of Space Debris...25

1.4 Hypotheses & Research Objectives... 26

1.4.1 Research Objective: Engineering Section... 26

1.4.2 Research Objective: Space Policy Section... 26

1.4.3 Research Questions... 26

1.4.4 M ethodology...27

1.4.5 Hypotheses ... 28

1.4.5.1 EVA Suit Design Tool...28

1.4.5.2 Statistical Analysis... 28

1.4.5.3 EVA Glove Task Study... 29

1.4.5.4 Regulation of Space Debris... 29

1.5 Thesis Outline ... 29

1.6 Contributions...31

SECTION I: ENGINEERING ANALYSIS 33 2. EVA BACKGROUND 37 2.1 Extravehicular Activity...37

2.3.1 EVA & NBL Injury ... 41

2.3.2 Current Countermeasures... 43

2.3.3 Proposed Countermeasures ... 46

2.4 EVA Hand Injury ... 49

2.4.1 Hand Injury in Spacesuit Gloves - Literature Review ... 50

2.4.2 Fingernail Delamination Incidence...51

2.4.3 Hand Injury Countermeasures... 52

2 .5 C on clu sion ... 53

3. MUSCULOSKELETAL DESIGN TOOL 55

3.1 _{Design Tool Developm ent ...--- . . ----... ... 55}

3.1.1 M usculoskeletal M odeling in SIM M ... ₅₆

3.1.2 M odeling Strategy ... ₅₆

3.1.3 Hard Upper g ... ₅₇

3.1.4 Assum ptions and M odel Lim itations... 61

3.2 Com fort Envelope ...---... -... ... 62

3.2.1 Range of Motion...62

3.2.2 Joint Torque Calculations... ₆₃

3.3 Conclusion ... ₆₄

3.4 Lim itations and Future W ork... 65

4. STATISTICAL ANALYSIS OF EVA HAND INJURY DATA 67 4.1 Background -M etric Predictive Study ... 67

4.2 Statistical Analysis of Crewm em ber Hand Data... 68

4.3 Results...70

4.4 Discussion... _{. ---... ---... 75}

4.5 Conclusion ...-... ₇₈

5. EXPERIMENTAL ANALYSIS OF EVA GLOVE TASKS 79 5.1 Prelim inary Finger Contact Pressure Investigation... 79

5.1.1 Test Equipm ent... ₇₉

5.1.2 M ethod ... ₈₃

5.1.3 Results...83

5.1.4 Discussion of Pilot Study Results... 85

5.2 Hand Injury Pilot Study at Johnson Space Center ... 86

5.2.1 M ethod ... ₈₆

5.2.1.1 Test Equipm ent... ₈₇

5.2.1.2 Subjects...91

5.2.1.3 Testing Procedure... ₉₂

5.2.1.4 Finger Pad vs. Fingertip Tests ... ... ... 94

5.2.1.5 Pressure Bulb Test... ₉₄

5.2.2 Results...95

5.2.3 Discussion ... ₉₇

5.2.4 Conclusion...99

6. SUMMARY AND CONCLUSIONS ₁₀₁ 6.1 Sum m ary...101

6.2 Contributions... ₁₀₁

6.3 Lim itations and Future W ork... 102

SECTION II: POLICY ANALYSIS 105 7. ORBITAL COLLISIONS & SPACE DEBRIS ₁₀₉ 7.1 Introduction and Background... 109

7.2 Tracking, M itigation & Protection Strategies ... 114

7.2.1 Tracking of Orbiting Bodies ... 114

7.2.2 Technical M itigation and Cleanup Strategies ... 115

7.2.2.1 Atm ospheric Drag - N ature's Vacuum ... 116

7.2.2.2 D e-orbiting of Space Hardware...116

7.2.2.3 Re-orbiting of Space H ardware ... 116

7.2.2.4 Passivation... 117

7.2.2.5 On-orbit M aneuvering... 117

7.2.2.6 M inim izing Release of Operational Debris... 117

7.2.2.7 Space Traffic M anagem ent ... 118

7.2.3 Shielding ... 118

7.3 Latest Space D ebris M itigation Concepts... 119

7.4 Orbital Collision Exam ples... 122

7.4.1 Example #1: February 2009 Orbital Collision between Cosmos and Iridium Satellites...- -.... ---... 122

7.4.1.1 Second-party Liability... 124

7.4.1.2 Third-party Liability ... 124

7.4.1.3 Insurance Coverage... 124

7.4.2 Example #2: Chinese Anti-Satellite Incident during January of 2007...124

7.5 Conclusion ... 126

8. INTERNATIONAL & DOMESTIC U.S. SPACE POLICY 127 8.1 Introduction... 127

8.2 Background on Space Law and Space Policy... 128

8.2.1 International Space Law ... 128

8.2.1.1 The Outer Space Treaty ... 129

8.2.1.2 The Rescue A greem ent ... 130

8.2.1.3 The Liability Convention ... 131

8.2.1.4 The Registration Convention...131

8.2.1.5 The M oon Treaty ... 132

8.2.2 International Space Policy on Orbital Debris...132

8.2.3 Current U .S. Space Policy...134

8.2.4 Current NA SA Policy ... 139

8.3 Advent of Com m ercial Spaceflight... 140

8.4 Conclusion ... 142

9. POLICY DISCUSSION & CONCLUSIONS 143 9.1 Introduction... 143

9.1.1 Shortcomings of the Current Space Debris Policy Framework ... 143

9.1.1.1 N on-Quantifiable ... 143

9.1.1.2 Non-Enforceable ... 144

9.1.1.3 N ot Taken Seriously ... 144

9.2 OBJECTIVE: New Policy Architecture Recommendations... 144

9.2.1 Stakeholders and Intended Audience... 144

9.2.2 Antitrust Issues ... 145

9.3 Policy Architecture Analysis ... 145

9.3.1 Tragedy of the Com m ons... 146

9.3.2 Comparison with Common Resource and Pollution Policies ... 146

9.4 Policy Fram ework Recom m endations...148

9.4.1 Recommendation #1: Exhort Insurers to Adopt a Bond System ... 148

9.4.2 Recommendation #2: Facilitate Debris X-Prize Competition ... 149

9.4.3 Recommendation #3: Tailor an International Treaty to Meet the Needs of all S tak eh old ers... _{14 9} 9.4.4 Recommendation #4: Foster Research to Upgrade Debris Monitoring System... 150

9.4.5 Recommendation #5: Actively Promote Mitigation & Protection Strategies... 151

9.5 Conclusion and Summary of Contributions... ₁₅₁

9.5.1 Problem Statem ent... ₁₅₁

9.5.2 T hesis Q uestion ... ₁₅₁

9.5.3 H ypotheses ... . . --... ... 152

9.5.4 Study M ethodology ... 152

9.5.5 Sum m ary of Contributions... ₁₅₃

9.6 Lim itations and Future W ork... 153

FINAL REMARKS ₁₅₄ ASTRONAUT INJURY REFERENCES ₁₅₅ SPACE POLICY REFERENCES ₁₅₉ APPENDIX A: HAND INJURY PILOT STUDY EXPERIMENTAL PROTOCOL ... 162

APPENDIX B: HAND INJURY PILOT STUDY TEST MATRIX ... 172

APPENDIX C: HAND INJURY PILOT STUDY DATA...174

APPENDIX D: HAND INJURY PILOT STUDY CPHS APPROVAL ... 179

APPENDIX E: TEKSCAN VASCULAR SENSOR DATA SHEET...181

Figure 1: a) Hard upper torso (HUT) restricting motion of the glenohumeral joint b) Lateral position of scye bearing joint for the three HUT sizes [EMU Shoulder Injury Tiger Team Report

p.34 (W illiam s, D . & Johnson, B., 2003)] ... 42

Figure 2: a) Glenohumeral joint b) Rotator cuff impingement c) Rotator cuff tear [EMU

Shoulder Injury Tiger Team Report p.27 (Williams, D. & Johnson, B., 2003)] ... 43 Figure 3: Cut-away view of the planar HUT with the shoulder harness visible [Evaluation of the Hard Upper Torso Shoulder Harness p.2 (De Witt, J. D., & Jones, J. (2007)] ... 44 Figure 4: The a) -335/-336 and b) -338 shoulder pad configurations used inside the

HUT (Williams, D. & Johnson, B., 2003)... 45 Figure 5: Combination of -335/-336 and -338 padding [EMU Shoulder Injury Tiger Team Report p.51 (Williams, D . & Johnson, B., 2003)] ... 46 Figure 6: Hip-support assembly concept by Grant Schaffner [Evaluation of the Hard Upper

Torso Shoulder Harness p.30 (De Witt, J. & Jones, J. 2007)]...47 Figure 7: Concept testing of the Festo fluidic muscles on the morphing SUT [Development of a Space Suit Soft Upper Torso Mobility/Sizing Actuation System with Focus on Prototype

Development and Manned Testing p.3 (Jones et al., 2007)]...48 Figure 8: Measurement of the SUT with the passive cable system [Development of a Space Suit Soft Upper Torso Mobility/Sizing Actuation System with Focus on Prototype Development and M anned Testing p.11 (Jones et al., 2007)] ... 49

Figure 9: Example of fingernail delamination [Extravehicular mobility unit training suit

symptom study report p.13 (Strauss, S. 2004)]... 51

Figure 10: Example of fingernail delamination of a female crewmember ... 52 Figure 11: Examples of countermeasures for fingernail delamination [Extravehicular mobility unit training suit symptom study report p.18 (Strauss, S. 2004)]...53 Figure 12: a) Laser-scanned model of pivoted HUT b) & c) HUT overlaid on musculoskeletal m odel in SIM M ... .-. ---... 58 Figure 13: a) & b) Hard point locations of scye bearings from the prototype SUT overlaid on the upper body m odel... ... ---.. ---... 60 Figure 14: Range of motion cone superimposed on model with ellipsoidal constraint object show n ... ... - . ---... 62

Figure 15: Shoulder joint torque plotted against shoulder flexion angle...64

Figure 16: Measured hand parameters for EMU glove sizing ... 68

Figure 17: Injury distribution vs. finger-to-hand ratio... 71

Figure 18: Injury distribution vs. hand circumference...72

Figure 19: Injury distribution vs. hand width... 72

Figure 20: ROC Curve from logistic regression analysis (Area under ROC curve = 0.73)...74

Figure 21: Cumulative Fraction of right hand circumference for injured and uninjured crew m em bers...75

Figure 22: Tekscan (Boston, MA) series 4305 vascular sensor to be used inside the EMU glove for measuring pressure distribution over the finger (with dimensions in millimeters)...79

Figure 23: Testing hardware and sensors that include the EMU glove and arm assembly, aluminum ring that fits on hypobaric chamber seal, and Tekscan pressure sensors. ... 80

Figure 24 a) Vascular pressure sensor positioned over middle finger b) Hand inserted into surgical glove for ease of donning/doffing of EMU glove. ... 81

Figure 25 a) EMU assembly inside hypobaric pressure chamber b) Pressure sensor on subject's hand inside EM U arm -glove assembly ... 82

Figure 26: Glove data recorded at the 3 pressure levels for a) relaxed & b) clasped hand...84

Figure 27: Tekscan series 4305 vascular sensor with handle and control box (Scale indicated in cm ) ... 8 7 Figure 28: Series 4305 vascular sensor with handle and EMU comfort glove (Scale indicated in cm ) ... _{8 8} Figure 29: Laser Doppler Flowmetry Probe with protective sheath...88

Figure 30: Vascular sensor and LDF probe positioned on the right middle finger such that no transducers are present on the finger tip ... 90

Figure 31: Digital countertop scale and bulb-gauge assembly of the sphygmomanometer used for compression and gripping tests (Scale indicated in cm)...91

Figure 32: Subject applies pressure to scale using the finger tip while wearing instrumentation and the EM U com fort glove... 93

Figure 33: Subject demonstrating use of the sphygmomanometer assembly during the 100 mmHg test ... _{9 5}

Figure 34: Epidermal blood flow in the finger - Fingertip vs. Finger pad... ... 96

Figure 35: Pulsatile flow in the finger - Fingertip vs. Finger pad. ... 96

Figure 36: Skin compression and blood flow for different regions of the hand and middle finger measured at no gripping (0 mmHg), moderate gripping (100 mmHg), and high gripping pressure (200 m m H g). ...---... ---...--- 97

Figure 37: Hypobaric chamber (or Glovebox) at NASA's Johnson Space Center in Houston, T exas ...--- .. . . ---... 103

Figure 38: Subject applies pressure to the digital scale inside the glovebox with EMU gloves donned ...---- . . ---... 104

Figure 39: Position of all objects surrounding the Earth as contained in the Space Command Satellite Catalog at 0000 GMT (McNutt, 1992). Image courtesy NASA Orbital Debris Program O ffice ...--... . ----... ---... 112

Figure 40: The damage caused by a 0.2 mm paint fleck impact on the shuttle window during the STS-7 mission required a $50,000 repair (McNutt, 1992) Image courtesy NASA...113

Figure 41: Damage caused by a 1 gram Tantalum pellet that impacted six 2 mm aluminum plates with an impact velocity of 6.54 km/sec (McDonnell Douglass Corp, 1990)...119

Figure 42: Cubesail concept demonstrated with a nanosatellite in front of a 5x5 m deployed solar sail (Im age courtesy of engadget.com )...121

Figure 43: Mock-up of the Iridium 33 Satellite with scale of actual satellite indicated (Image C redit: N A S A )...123

Figure 44: The Fengyun FY-IC weather Satellite with a deployed length of 10 m. The dimensions of the hexahedron is 1.42x1.42x1.2 m (Image Courtesy: NASA)...125

Figure 45: Estimated growth of passenger demand for suborbital space tourism over the next decade (extracted from Suborbital Space Tourism Demand Revisited (Futron, 2006)). ... 141

Figure 46: Tekscan sensor and LDF probe placement on finger...164

Figure 47: Layout of measurement and data analysis equipment ... 166

Figure 48: a) Contact pressure and b) blood flow for finger pad configuration...174

Figure 49: a) Contact pressure and b) blood flow for finger tip configuration...175

Figure 50: a) Pressure and b) Blood flow data for Sphygmomanometer test ... 175

Figure 51: Pressure Distribution over different regions of the hand ... 176

Figure 52: Occlusion sets in at about 240 seconds in the finger pad configuration...176

Figure 53: _{a) Pressure and b) blood flow data for astronaut subject while performing typical}

E V A tasks inside the glovebox...177

Table 1: Sum m ary of Literature Review ... 54 Table 2: Numbers of injured and uninjured crewmembers who have complete anthropometric

data...--- .- . . . ---... 69

Table 3: Significant (p = 0.0 167) Parametric and Nonparametric Statistical Results for Fingernail

Injury in M ale Crew m em bers... ... ... 71 Table 4: Logistic regression results for hand circumference and body mass index (BMI) ... 73 Table 5: Hand data for subjects (n=7) and crewmembers whose records are complete (n=216) .92 Table 6: Comparison between space debris mitigation, common resource and pollution

m anagem ent policies...- -. --...--- 147

C

CAD Computer Aided Design

CEV Crew Exploration Vehicle

COPUOS Committee on the Peaceful Uses of Outer Space

CPHS Committee for the Protection of Human Subjects

E

EMR Electronic Medical Records

EMU Extravehicular Mobility Unit

EPSP EVA Physiology, Systems, and Performance

ESA European Space Agency

EVA Extravehicular Activity

EU European Union

F

FAA Federal Aviation Administration

FCC Federal Communications Commission

FFT Fast-Fourier-Transform

G

G Gravity

GRC Glenn Research Center

H

H/A Hazard Assessment

HS Hamilton Sundstrand

HST Hubble Space Telescope

HUT Hard Upper Torso

I

IRB Internal Review Board

ILC International Latex Corporation

ISS International Space Station

ITU _{International Telecommunications Union}

ITS Injury Tracking System

J

JAXA Japanese Aerospace Exploration Agency

JSC Johnson Space Center

K

kPa Kilopascal (1 kPa = 0.1450378 psi)

Liquid Cooling and Ventilation Garment Laser-Doppler Flowmetry

Metacarpophalangeal Millimeters of Mercury

Massachusetts Institute of Technology Man-Vehicle Laboratory

National Aeronautical and Space Administration L LCVG LDF M MCP mmHg MIT MVL NASA 20

NBL

NSBRI

Thermal Micrometeoroid Garment Technology Readiness Review

UN UNCOPUOS USRA U.S. UTMB UTHS United Nations

United Nations Committee on the Peaceful Uses of Outer Space Universities Space Research Association

United States

University of Texas -Medical Branch United Technologies Hamilton Sundstrand a

Greek Symbols

pt-g Microgravity

21 Neutral Buoyancy Laboratory

National Space Biomedical Research Institute

Pounds per Square Inch (1 psi = 6.894757 kPa) Pounds per Square Inch Absolute

Red Blood Cells Russian Space Agency

Software for Interactive Musculoskeletal Modeling Soft Upper Torso

psi psia R RBC RSA SIMM SUT TMG TRR

-

Joseph Joubert

INTRODUCTION

Ever

since Ed White's venture into the vacuum of space on June 3, 1965, marking the

first American spacewalk, mankind's dreams of space exploration outside the limits of a rigid spacecraft became more tangible. When Neil Armstrong left his first bootprint on the surface of the moon on July 20, 1969 during the Apollo 11 mission, the dream of exploring other worlds became a reality. Integral to all of the momentous achievements of the Gemini and Apollo programs, is the separation of astronaut and spacecraft, known as extravehicular activity or EVA.

1.1

Background

With President Obama's new U.S. space policy on human space flight that includes sending humans to an asteroid by 2025 and to Mars by the mid-2030s, EVA will once again play a major role in exploration (U.S. Office of the Press Secretary, 2010). This time though, EVA will be much more significant. Throughout the entire Apollo era, fewer than 20 EVA's were performed in contrast to the 2000 plus EVA's that are projected for a future exploration program that would result in a sustained presence of humans on another celestial body (Gernhardt, 2007).

Another aspect of continued advances in space exploration that is not always as readily realized is that of space debris and orbital collisions. Throughout mankind's endeavors to explore and conquer the heavens, we have been leaving behind hardware that seems insignificant at first, but slowly accumulates as more companies, conglomerates, and nations join in with their own space-faring vessels - many of which stay in orbit decades after it has reached the end of its useful life. This growing number of old and new spacecraft being launched poses a threat to human safety in space as well as to the Low Earth Orbit (LEO) environment as orbital collisions become more

prevalent. Effective regulation of decommissioned spacecraft is essential to ensure future human and planetary safety.

1.2

EVA Injury Problem Statement & Motivation

With such an expected escalation of EVA hours, it is absolutely essential to re-assess the in-use

EVA hardware and procedures in order to minimize and preferably eliminate spacesuit trauma

that is experienced by astronauts training and performing EVA's in the current spacesuit known as the extravehicular mobility unit or EMU.

1.2.1

EVA Training-related Shoulder Injury

The literature shows that a significant number of EVA crewmembers experience suit-induced shoulder trauma while training in the Neutral Buoyancy Laboratory. The goal of this study is to assess the causal mechanisms associated with the reported injury and to mitigate this through improved suit design and enhanced training operations.

1.2.2

EVA Hand Injury

Suit-induced fingernail delamination and other injuries sustained inside the EMU glove pose a significant threat to extended EVA's planned for long duration lunar and Mars missions. The hand is not only the most complex geometry of the human body, but it is also used extensively during EVA tasks. By investigating the causal mechanisms of EVA-related finger injury, recommendations can be made for future glove designs that will provide the suited crewmember with enhanced comfort and protection.

1.3

Space Policy Problem Statement & Motivation

Since the dawn of satellites in the early 1950's, space debris from intentionally exploded spacecraft, dead satellites, and on-orbit collisions has significantly increased and currently outnumbers operational space hardware. Adding to this phenomenon, the advent of commercial spaceflight and the recent space activities in China and India to establish themselves as space-fairing nations are bound to accelerate the rate of space debris accumulating in low Earth orbit, thus, exacerbating the problem. The policies regulating orbital debris were drafted in the 1960s and 1970s and fail to effectively address the dynamic nature of the debris problem. These policies are not legally enforced under international law and implementation is entirely voluntary.

1.3.1

Orbital Collisions

Orbital collisions are directly linked to space debris and threaten human life, space hardware and ultimately mission success. In an effort to better understand the complexities and incidence of orbital collisions this thesis reviews current international space policy, legislation and mitigation strategies in light of the past half-century of United States space flight and two recent orbital collision episodes. The first example is the February 2009 collision between a defunct Russian Cosmos spacecraft and a commercial Iridium satellite. The second is China's display of technological prowess during the January 2007 intentional demolition of its inactive Fengyun- 1 C weather satellite using an SC-19 anti-satellite (ASAT) missile. In each case the stakeholders, politics, policies, and the aftermath of the collision were analyzed and recommendations for alternative preventative and regulatory strategies set forth.

1.3.2

Regulation of Space Debris

Space debris is a relevant issue in international space cooperation. Unless regulated, some estimations indicate space debris will reach a point of critical density, after which point the debris will grow exponentially, as more fragments are generated by collisions than are removed

by atmospheric drag. Space debris proliferation negatively impacts human spaceflight safety,

presents a hazard to orbiting space assets, and may lead to portions of near-Earth orbit becoming inaccessible, thus limiting mission operations.

1.4 Hypotheses & Research Objectives

1.4.1

Research Objective: Engineering Section

The aim of the engineering section of this study was to investigate EVA-related injury in order to gain a more in-depth understanding of the underlying causal mechanisms and to better realize techniques for enhanced injury mitigation, comfort and protection.

1.4.2

_{Research Objective: Space Policy Section}

The research aim of the space policy sections was to review current literature pertaining to the regulation of space debris and prevention of orbital collisions and to propose possible future policy and regulatory mechanisms for implementation.

1.4.3

Research Questions

The two main areas of injury identified are EVA training related shoulder injuries and hand injuries sustained inside the EMU glove. Questions that are relevant to this study are:

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Could a musculoskeletal modeling tool be developed and utilized to enhance the fit and comfort of the space suit torso?

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How can the suit be outfitted with sufficient comfort layers while not surrendering mobility?

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What role does finger skin blood flow, contact pressure and hand anthropometrics play in the incidence offingernail delamination sustained from EVA operations and training in the EMU glove?

With regard to space policy the following questions require answers:

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How does current international space law address the issue of orbital debris, if at all?

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What is the official view of the United States with regard to space debris mitigation?

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What are current and proposed technical mitigation strategies?

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In the light of recent collision incidents, are these efforts successful?

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What policy measures should be put in place for the effective regulation of space debris? o What should be the procedure for decommissioning old satellites/spacecraft?

o What are the impacts on human safety and the environment?

o What are the foreseeable consequences?

1.4.4

Methodology

This thesis has been divided into 4 distinct parts:

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The development of a cursory musculoskeletal design tool for comparing different suit concepts while optimizing comfort and mobility.

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A statistical analysis of EVA crewmember anthropometric and injury data to investigate

possible correlations between fingernail delamination and hand size.

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Experimental testing to evaluate changes in blood flow and contact pressure in the finger tips due to compression of the skin inside the EMU glove while performing simulated

EVA tasks.

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A detailed look at past and current policy and regulatory measures pertaining to orbital

collisions. This literature review forms the foundation of recommendations for future space policy.

1.4.5

Hypotheses

1.4.5.1

EVA Suit Design Tool

Hypothesis 1:

Hypothesis 2:

The musculoskeletal design tool will enable the user to develop a spacesuit Hard Upper Torso or HUT assembly with increased range of motion when compared to the current EMU HUT.

The musculoskeletal design tool will facilitate placement of simulated comfort padding and protection that will result in a significant increase in

crewmember comfort.

1.4.5.2

Statistical Analysis

Hypothesis 3:

Hypothesis 4:

NASA personnel hypothesize that the crewmember finger-to-hand length ratio is significantly correlated to fingernail delamination. This thesis aims to test this hypothesis.

Crewmembers with larger hand dimensions are more likely to sustain fingernail trauma during EVA missions and training sessions.

1.4.5.3 EVA Glove Task Study

Hypothesis 5:

Hypothesis 6:

A significant decrease in blood flow is expected during gripping and pressing tasks both in and outside of the hypobaric chamber.

Blood flow occlusion effects are significantly more pronounced during finger pad compression as opposed to finger tip compression.

1.4.5.4 Regulation of Space Debris

Hypothesis 7:

Hypothesis 8:

No clear set of space policy regulations is actively being enforced to regulate the ownership and decommissioning of redundant orbiting spacecraft,

satellites and associated debris.

A combination of technical mitigation techniques and clear international policy strategies/legislation is needed for the space industry to limit further debris growth.

1.5

Thesis Outline

Chapter 1 contains the introduction and problem statement of the study on EVA injury, comfort and protection as well as the space policy problem statement pertaining to orbital collisions and space debris.

Chapter 2 takes a historic look at shoulder injuries sustained during EVA training. Main causes for injury and implemented countermeasures are identified. The effectiveness of current countermeasures is discussed as well as new alternatives to the current EMU hard upper torso

(HUT). Hand injury, specifically fingernail delamination, and implemented countermeasures are

discussed.

In the quest of mitigating shoulder injury inside the suit, a cursory musculoskeletal model was developed to aid in the design of new HUT's that will allow for maximum mobility while protecting the suited astronaut from being exposed to excessive joint torques. Chapter 3 discusses the modeling strategy and implementation.

To further understand the causal mechanisms of these hand injuries, a statistical analysis was performed to investigate possible correlations between astronaut anthropometric data and susceptibility to fingernail delamination. The details of the analysis with its results are presented in the first section of Chapter 4.

Results from a preliminary study in the hypobaric chamber of MIT's Man-Vehicle Laboratory are presented in Chapter 5. The second section of Chapter 5 discusses a study that was conducted during the summer of 2008 at NASA's Johnson Space Center, Houston TX, where skin blood flow and contact pressure was recorded for 7 subjects. The goal of the study was to investigate the correlation between blood flow and contact pressure inside the glove. The pilot study was also used to validate hardware for subsequent testing on astronaut subjects to determine whether differences in blood flow and contact pressure exists between uninjured and injured crewmembers.

Chapter 6 contains the conclusions for both the shoulder and hand injury sections of the thesis. The chapter summarizes the conclusions of the preceding chapters and discusses future work and limitations.

Chapter 7 provides an introduction to space policy and presents current space treaties and conventions that may be applied to the regulation of space debris.

Chapter 8 involves a deeper look into the topic of space debris and orbital collisions. Examples of past collisions are considered and the relevant regulatory statuses (if any) are discussed. The effect of debris on human safety and the environment is discussed and future policy measures for regulating this rising concern are presented.

The thesis concludes with Chapter 9 that contains a discussion on the relevant debris policy issues, briefly summarizes section II of this thesis and recommends further work that may follow from this policy analysis.

1.6 Contributions

The following contributions are made in this thesis:

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A cursory musculoskeletal design tool is developed that may be used to get a sense of

range of motion and comfort consideration during the initial stages of new hard upper torso spacesuit concepts. The tool allows the user to optimize comfort and mobility before the design leaves the digital drawing board.

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Results of the statistical analysis of EVA crewmember anthropometric and injury data indicate that the ratio of finger-to-hand length is not a significant contributing factor to the onset of fingernail delamination. Hand width and hand circumference, however, were found to be significantly associated with injury. A cut-off hand circumference value was identified that may serve as an early warning indicator of crewmembers that may be prone to fingernail delamination within the current EMU glove.

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The experimental testing with blood flow and contact pressure in the finger tips serves as a pilot study and protocol validation for ongoing research efforts at NASA's Johnson Space Center. The study reveals correlations between blood flow and skin contact pressure that may contribute to the onset of fingernail delamination.

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A detailed look at past and current policy and regulatory measures pertaining to orbital

collisions, discussion thereof and recommendations of mitigation and policy strategies that may serve as the basis for international discussion makers to formulate future space debris policy.

man will not be lacking [on the moon and Jupiter]... Given ships or sails adapted to

the breezes of heaven, there will be those who will not shrink from even that vast

expanse."

- Johannes Kepler, letter to Galileo, 1610

that's what living is all about."

- Michael Collins

EVA BACKGROUND

2.1

Extravehicular Activity

Extravehicular

Activity or EVA spacesuits are a key enabling technology for space

operations, particularly during construction, maintenance and exploration missions (Newman & Barratt, 1997). The NASA EVA suit, called the Extravehicular Mobility Unit (EMU), is a 14 layer body-shaped enclosure pressurized with 100% oxygen at 29.6 kPa (4.3 psi) (Newman, 2000). The design of the EMU gloves is regarded as the most challenging "softgoods" part of the suit, and developing a small tactile joint for the fingers has been extremely challenging (Newman & Barratt, 1997; Harris, 2001; Sietzen, 1999; Scheuring et al.,

2009).

The current EMU glove is the Phase VI, which was first flown in December 1998. The Phase VI is the successor of the 4000 series glove, and was at first custom-made for crewmembers using hand casting, laser scanning, stereo lithography, 3D computer modeling, laser cutting and CNC machining. According to Graziosi, these processes result in a better fit and improve comfort and mobility in the glove compared to the 4000 series gloves. At the same time, the Phase VI gloves can be produced faster and at lower cost (Graziosi et al., 2001). Through the years the range of available glove sizes increased, eliminating the need to fabricate a custom glove for certain crewmembers. When selected for an EVA mission, a crewmember is fit checked in "close-fit" gloves that have been customized for other crewmembers. However, customizations are performed if no adequate glove fit can be achieved. One pair of gloves will only be used for training, while other pairs are crafted for flight use (Splawn, 2009).

As almost all EVA tasks require some form of hand function, effective suit gloves are critical to successful EVA performance (Cadogan et al., 1993; Graziosi et al., 2001). Improvements in

glove flexibility, dexterity, tactility and comfort, with a reduction in muscle fatigue and injury, would have the greatest impact on astronaut productivity (Scheuring et al., 2007; Jones & Schmitt, 1992; Shepherd & Lednicky, 1990). With the one to two orders of magnitude increase in EVAs required for imminent and complex Asteroid and Mars missions, the demands on safe and effective hand function will also increase (Viegas et al., 2004); it is therefore essential that glove performance be improved for both Asteroid and Mars EVA missions and EVA training.

The primary NASA EVA training facility is the Neutral Buoyancy Laboratory (NBL) at Johnson Space Center, Houston, TX, which simulates the weightless conditions of orbital operations. The

NBL is a 23.5 million liter water tank that contains full-sized mock-ups of the Space Shuttle

cargo bay, flight payloads, and the International Space Station (ISS). The spacesuit assemblies used in the NBL are certified for training only, and accept the custom training gloves. Initial crewmember EVA qualification, evaluation and skills training consists of -65 hours in the NBL, while specific mission training consists on average of 11.6 hours per hour of flight EVA (Williams & Johnson, 2003). Mission training usually starts approximately 1 year before the scheduled spaceflight.

Despite the advances in spacesuit glove technology and fabrication, astronauts still claim that the hardest part of any EVA is working with the hands (Chaikin, 1999). Hand dexterity, tactility, strength and endurance are impeded because of the force required to bend the rigid, gas pressurized materials from the neutral position (Sorenson et al., 1997; Eckart, 1996; Welsh & Akin, 2001). In addition, the gloves are often uncomfortable to the point of pain and/or minor physical injury to the hand: they cause calluses, abrasions, contusions, fingernail trauma, wrist and forearm muscle stress and nerve impingements between the thumb and forefinger (Viegas et al., 2004; Welsh & Akin, 2001; Lee, 2001; Strauss, 2004; Strauss et al., 2005). In a study of in-flight EVA injuries to U.S. astronauts, 20 instances of hand injury were reported, followed by 12 to the foot (Scheuring et al., 2009). Strauss et al., (2005) found that in 770 EVA training sessions conducted from 2002 to 2004, 352 injury symptoms were reported. Of those, the largest number, 47.2% were complaints about the hand, and 20.7% concerned the shoulders. Of the hand symptoms, more than half were due to fingertip and nail contact inside the glove. During the study period 18 astronauts required continued medical care for hand issues, 13 of which were

for fingernail delamination from the nail bed (onycholysis) (Strauss et al., 2005). At least one astronaut has had fingernails removed before an EVA mission to prevent pain, obstruction of the fingertip by the loose/protruding nail inside the glove, and the risk of secondary bacterial or yeast infection of the exposed bed in the moist conditions in the glove (Gernhardt, 2009). In sum,

EVA injuries have become more prominent since 2002, probably due to the unprecedented

increase in training to support construction and maintenance of the ISS (Williams & Johnson,

2003; Strauss et al., 2005).

Onycholysis or fingernail delamination is caused by axial loading of the fingernails during hard contact with the inside of the glove when the fingers are reaching or forcefully grasping an object (Strauss, 2004). Additional factors that may contribute to onycholysis are the local presence of moisture (Jones et al., 2008), and reduced/occluded perfusion to the fingernail bed due to contact pressure inside the glove. The most effective countermeasure for onycholysis as reported by Strauss is to provide optimal glove fit. Other countermeasures are for the crewmembers to keep their fingernails short, to apply dressings to fingertips for protection and to keep the fingers free of moisture.

A potential mechanism of pain in the fingertip, found after EVA training or activity in some

crewmembers, is an intermittent restriction of blood in the finger tissue due to gripping and relaxing of the hand inside the pressurized glove. This is analogous to reperfusion injury commonly observed following organs such as the liver that have been made transiently ischemic (Jones, 2009). Following post-ischemia reperfusion, there is capillary fluid and cellular leak, which could result in increased interstitial fluid pressure or swelling. In a fingertip with an intact nail, the increased tissue pressure against the rigid nail could be sensed by the pain fibers in the nailbed, thus causing crewmember discomfort. This reperfusion induced pressure increase in the nail matrix is hypothesized to cause the nail to detach from the nailbed, resulting in the onset of fingernail delamination. Hyperperfusion, the term used for the fierce return of once constricted blood to a blood-deprived in vivo tissue region is hypothesized to intensify these effects.

Beyond the glove design, a fundamental challenge to glove performance is the complexity of joints and dimensions inherent in the hand. Recent experience and observations by NASA EVA

personnel seem to support a hypothesis that crewmembers with long fingers and short palms are more likely to sustain finger injury as they are not able to utilize muscles in the palm to close the glove (Gernhardt, 2009). If this hypothesis is true, then crewmembers with short fingers and larger palms may unload their finger pad pressure by grasping objects more in the palm of the gloved hand, while subjects with longer fingers and shorter palms will require more fingertip pressure application to surround and compress the same object. Thus a prospective study evaluating differences in the pressure-perfusion relationship between crewmembers with varying hand anthropometrics (finger-length-to-hand-circumference ratio, hand-length-to-circumference ratio, etc.) is needed to better define which anthropometric and glove factors are contributory to

space suit hand injury.

A database of injury records and anthropometrics was compiled from EVA logs at NASA

Johnson Space Center and the Neutral Buoyancy Laboratory training facility (Hochstein, 2008, Scheuring et al., 2009). Crewmember anthropometric and injury data were analyzed, exploring the hypothesis that crewmembers with a high finger-to-hand length ratio are more likely to experience EVA-related fingernail injuries, as early evaluation of the data suggested this trend. In the more complete data review, this hypothesis has not been confirmed, however results show that hand circumference may be a predictive factor for injuries in the hand. The finger length to hand circumference ratio relationship to injury is being explored during the analysis.

2.2

Apollo Program Interview

Dr. Richard Scheuring of NASA's Johnson Space Center recently interviewed 14 of the 22 surviving Apollo crewmembers in an effort to hear firsthand their recommendations for going back to the moon. Below is an excerpt that captures the key findings relevant to this thesis work:

"According to the Apollo lunar crews, the most fatiguing part of all surface EVA tasks was repetitive gripping inside the glove. One crewmember stated, "Efficiency was no more than 10% of the use of the hand" The fingernails generally tended to be pulled back resulting in separation of the nail from the bed, or onycholysis. Additionally, the skin frequently was abraded from the top of the knuckles. This event took on operational and potentially mission significance as several lunar

walkers stated that they would not be able to work in the glove beyond the two to three EVAs they completed due to the swelling and pain over the bony prominences of the metacarpal phalangeal (MCP) and proximal interphalangeal (PIP) joints (knuckles), although had they been asked, it is probably that at least one more EVA would have been possible" (Scheuring, 2007).

Another area that needs significant improvement according to the Apollo crewmembers is mobility within the suit. This brings us to another area of injury within the suit: shoulder injury.

2.3 Shoulder Injury in Shuttle and ISS Programs

2.3.1

EVA & NBL Injury

A significant number of astronauts who undergo EVA training at the Neutral Buoyancy

Laboratory (NBL) testing facility at Johnson Space Center sustain significant shoulder injuries that in some cases even require surgical intervention (Strauss et al., 2004). After mounting anecdotal evidence had been raised by crewmembers, trainers and physicians, a multi-directorate tiger team was formed that collected data, interviewed crewmembers and performed tests to determine whether a causal relationship existed between training in the NBL and the observed shoulder injuries (Johnson et al., 2004)

The study found that EVA training related shoulder injuries were attributed to the following six main causes (Williams & Johnson 2003):

- The EMIU Planar HUT design restricts normal scapulothoracic motion of the shoulder joint, resulting in rotator cuff impingement when the arm is abducted (Figure 1)

- Suboptimal suit fit - Only three sizes of the HUT is available, thus not all crewmembers are accommodated in the suits and these are more prone to injury

- Inverted body orientations of the astronauts while training inside the tank - Performing overhead tasks while inverted

- The frequency of the NBL training runs - Frequent runs prevented crewmembers from recovering completely from minor injuries, leading to more serious injuries

- Heavy EVA training tools that are used during training sessions

The design of the planar HUT shoulder joint is a significant factor that contributes to the risk of

EVA training-related injury. Figure 1 shows the restricted scapulothoracic motion caused by the HUT as well as the lateral position of the scye bearing joint that gives rise to a concentrated

pressure points on the shoulder when inverted. (Williams & Johnson, 2003).

b)

Figure 1: a) Hard upper torso (HUT) restricting motion of the glenohumeral joint b) Lateral position of scye bearing joint for the three HUT sizes [EMU Shoulder Injury Tiger Team Report p.34 (Williams, D. & Johnson, B., 2003)]

Excessive loading of the shoulder joint and repetitive overhead arm motion can lead to chronic irritation of the rotator cuff tendon, resulting in rotator cuff tendonitis. The glenohumeral (shoulder joint) with surrounding muscle and bone is shown in Figure 2 a). Figure 2 b) and c) depict rotator cuff impingement and ultimate tear that occurs when no appropriate intervention steps are taken.

Figure 2: a) Glenohumeral joint b) Rotator cuff impingement c) Rotator cuff tear [EMU Shoulder Injury

Tiger Team Report p.27 (Williams, D. & Johnson, B., 2003)J

2.3.2

Current Countermeasures

The current countermeasures that are used to mitigate injury sustained in the NBL are:

- Hard Upper Torso (HUT) Shoulder Harness

- Removable Shoulder Pads

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Hard Upper Torso Shoulder Harness

The HUT shoulder harness incorporates Teflon strips at the shoulder regions with the purpose of distributing the loading from the scye bearings on the crewmember's shoulders when inverted. Figure 3 shows the placement of the shoulder harness inside the HUT.

De Witt & Jones (2007) performed a study to evaluate the effectiveness of the shoulder harness. Their findings revealed that, although the harness reduces crewmember discomfort, it does not

completely eliminate pain, it may affect arm range of motion, and it does not reduce total shoulder loading, which suggests that the shoulder harness may not eliminate the incidence of shoulder injury.

ADJUSTMENT

BRACKET

BIC ATTACHtMENT ATTACHMENT LONG

BRACKETS PIN (BACK) STRAP

(FRONT)

Figure 3: Cut-away view of the planar HUT with the shoulder harness visible [Evaluation of the Hard Upper

Torso Shoulder Harness p.2 (De Witt, J. D., & Jones, J. (2007)]

Williams and Johnson (2003) also came to a similar conclusion in addition to their observation that many crewmembers were unaware that the harness was available as a means to alleviate the pressure points on their shoulders. Johnson et al., (2004) states "It appears that this portion of the suit design was given little to no thought over the years because it was deemed a crew comfort or preference item. In fact certain items like the HUT harness had been almost erased from the corporate memory of the program."